Apple 2 in an ammo tin.

This was a follow on from my Tardis MAME console. The idea was to build a small portable MAME machine. My idea, not an original one it turns out, was to build a PC into a .50 cal ammo tin. I bought a tin from Kiwi Disposals on K Road, the local army surplus place. Apparently this was some time in about mid 2008 but I can’t be sure. I know I took loads of pictures of things but I can’t seem to find them!

Ammo tin.

Ammo tins are made from steel and they are very solid. They are also waterproof, have a solid catch, a carry handle and the lids can be detached. They make great tool boxes (I have one in the back of my MGB) and they have been used in the past for making other ammo tin computers. I think mine cost me about $25NZ. Apparently it heldM728 artillery shell fuzes not actual .50cal rounds.

To go inside it I wanted an older motherboard. I specifically wanted one with a joyport, the old 15 pin D ones. The idea was that I would use this machine with my ancient but excellent Thrustmaster F16 FLCS joystick. I had a look on TradeMe and came across an older motherboard for sale. It was a Gigabyte GA-8LD533 with a 1.7GHz Intel Celeron processor. I had to look in my TradeMe history to see I bought this back in June 2008 which is how I dated when I started the project!

To fit the computer into the ammo tin I made a metal sub frame to mount everything too. I am sure at the time I took pictures of all this but I can’t find them at all now. I did get everything finished and I think it was all working but I never actually used the machine for anything so it is been sitting on the floor under my computer desk for the last 3 years gathering dust. All the pictures here are new ones. I can’t remember if I actually got the thing running. I think so?

You’re probably wondering why I dug it out now. Well, that is my colleague Grant’s fault.  I know several Grants. The first is old beardy from my Zeacom days. He gives me old engines to play with. The second is artist Grant who helps me with car things. The third is author Grant at my current job. He got me addicted playing Taipan on our Android phones. It turns out this isn’t a great port. So I started looking at the original versions. The one I remember is the Apple 2 one.

Now the Apple 2 is a computer I remember very fondly. It wasn’t my first computer, that was a Commodore Vic 20. The Apple was my second computer. At first I had an Apple 2 plus, bought by my parents second hand from the computer shop that used to be over the road from the old Farmers building on Hobson street in Auckland. Oddly enough I now work less that a km from there – doing computer stuff! We eventually upgraded that to an Apple 2E enhanced.  Recently I discovered at my parents house my old Apple 2 folder. In 1986 that computer cost my father $1864! And that was at a discounted price since he worked at the university so got an educators discount. I was 13.

Original 1986 receipt.

That was a lot of money then. Still is now! I guess it paid off, computers is what I do and now it pays for me to be able to spend money to recreate what I had way back then.

It’s kind of circular really.

Anyway, Grant got me into Taipan and we both fondly remember the Apple 2 version. Grant has an idea to build a PC into an old Apple 2 disk drive. I remembered my old ammo tin project and decided to turn that into an Apple 2 emulator. I had previously tried out the AppleWin emulator and knew that worked well. The latest version is now here. I decided to try Taipan on the ammo tin.

When I tried to run it the damn thing wouldn’t boot. It seems that somewhere along the line the 120GB drive in it failed. I found it wouldn’t boot up and I wasn’t able to reformat the drive to reinstall Windows XP on it. I did find an old 1.2GB drive and was able to get the machine up and running on that. Unfortunately 1.2GB is far too small for an up to date XP installation. But it was enough for me to get the machine running and AppleWin installed to make sure it was going to work.  Once I confirmed that author Grant came to my rescue with an old 20GB drive I could use.

So I set about rebuilding the machine.

In the original box I had made the basic fame and mounted the motherboard, power supply and hard drive. I had bought a small PC power supply to fit inside the tin. I am not sure what the wattage on it is but it is tiny. I am using the on-board video port and have no peripheral cards at all so I should need too many watts.

Basic box.

The basic fame is made from aluminium sheet with aluminium extrusions in the corners.

Front panel.

The front panel is another sheet of aluminium with appropriate cut outs. I used two drawer handles on the front to provide an easy way to pull the chassis out of the ammo tin.

The motherboard is mounted with four brass screws fitted through the bottom of the chassis. To keep the screw heads flush I used countersunk screws. I drilled the holes for them then put the screws into the holes and hit the heads with a hammer. This indents the aluminium to fit the screw head so they fit flush with the chassis. I used a plastic sheet under the motherboard to ensure it wouldn’t short and used rubber power cord grommets cut in half as rubber spacers to hold the board off the chassis.

MB mounts.

The motherboard was mounted into the chassis. The front panel provides cut-outs for the connectors on the back of the motherboard, the power supply and for switches, LEDs and USB ports.

MB and supply installed.

The MB sits in the base of the chassis. The power supply sits above it attached to the front panel. The hard drive, in this case a 5 1/4 drive, is attached vertically to the back of the chassis.

I used a missile switch as the main power/reset switch. I added two LEDs for power and HDD indication. All of this was basically how the box was as I built it in 2008. The front panel had a large hole in it which I was going to use as storage. I never actually got around to making a liner for the hole so I made up a new aluminium panel which isolates the motherboard from the rest of the tin. This panel, forming a neat cubby hole, is held in place by the LED bezels and provide useful storage space.

Cubby hole.

With this in place the chassis was finished and it ould be slid into the ammo box. It is worth nothing that if you need to reinstall Windows or need the use of a CD/DVD ROM drive you can simply slide the chassis out and temporarily attach a drive. All the cables are present in the chassis already.

DVD drive.

You can see how when the chassis is slid into the box the cubby hole is separated from the rest of the box.

Chassis in box.

If you look carefully you will see the third USB socket is upside down. This is one I added with the update to the build. I had two spare USB cables floating about inside the box so I made one available on the panel. I put it upside down since I have found you sometimes come across some USB accessories that won’t fit into the socket in a sensible orientation. They need to be inserted upside down! This way I have all bases covered.

Well, that’s my excuse anyway.

Everything is very snug in the box. After running it for a while. I discovered several thing. 1) it gets very hot and 2) it would be handy not to need to connect external speakers.

For the first problem I added in a second (well third) fan. The CPU already has a fan as does the power supply. All the air was being blown out of the holes on the front of the power supply and this seemed rather hot. I added in a fan to the side of the cubby hole to blow air through the box. This made a massive difference to the temperature of the box and now it runs very cool.

  Fan vent in cubby hole.

I also decided since all I was trying to emulate was very simple Apple 2 sounds I should add an internal speaker. The Apple 2 used a simple, small, single channel speaker. I added one inside the case held to the side of the power supply with industrial strength Velcro. I added a switch to the front panel that switches the output from the internal speaker (wired so both channels are going into the one speaker) to the normal rear (in my case front) line out socket. I did this using the front audio output socket on the motherboard. This way I can plug external speakers into the box if needed but most of the time the Apple sounds are sent to the internal small speaker, just like in an original Apple 2.

Front panel with speaker switch.

With those in place I slide the chassis into the box.

Chassis in place.

The cubby hole is used for storing the cables and mouse. I am currently using a wireless mouse with a large receiver that I got when I originally started the project in 2008 . I modified the receiver by opening it up and hot gluing a rare earth magnet into it. I can then stick the receiver to the outside of the steel ammo tin.

Storage and magnetic mouse receiver.

I will probably replace the mouse with a modern Bluetooth one to save some space. I also had a USB folding keyboard that would fit into the cubby hole. Unfortunately that broke so for now I am using conventional keyboard. I have bought a new folding one that will hopefully fit into the case.

And that is the box basically finished. Even though it is an old motherboard and CPU it is easily enough to run the Apple 2 emulator. So far every single game runs fine.

I can attach the box to a external monitor or, through an interface box, to my old tellie (yes, will get an LCD one day). Everything (hopefully including the keyboard soon) fits into the cubby hole when the box is being carried. It is all pulled out and set up to run the machine. The cubby hole is left free then so the fan is unobstructed although it does provide handy storage for temporary items.

The toggle switch is used to power the box on and off. Flicking it off will cause the box to shut down nicely rather than just killing the power.

AppleWin allows you to run the screen either windowed or full screen as well as simulating colour or monochrome screens.

Next is to download as many old games as I can. So far all of them seem to run well. It’s a real trip down memory lane for me. All the old games: Below the Root, Wings of Fury, Captain Goodnight, Rescue Raiders, Choplifter, Loderunner, Conan, Drol, Bolo, Dungbeetles! We got ya!

I also need to build the equivalent of an old Apple joystick. AppleWin allows the use of a PC joystick but I want to build a PC compatible joystick in the style of the old Apple 2 ones. I have a plan to build a small one using the analogue stick from an old Playstation controller and a couple of buttons.

I started building up a small collection of cufflinks (I also have a collection of salt and old 1950/60s Gillette razors but that’s another story). Cufflinks are ridiculously overpriced in NZ (what isn’t?) so I tend to order mine from overseas. You get better quality ones at better prices if you hunt about.

Favourite cufflinks.

Above are some of my favourites. Yes, I am something of an Anglophile and a train-spotter. The Dalek ones are very cool and I always had it in my mind that the TARDIS would make a nice cufflink. It is possible to buy some but I never got around to it. The London Underground ones a friend of mine got for me when he and his wife visited London from their home in New York and I then had to wait till they visited New Zealand to bring them to me. Those are well travelled cufflinks!

One of my other (many) projects is an N scale model railway I am building to go into a dining table. That is a 1930s British themed layout and when looking around at what buildings I could get for it I discovered you can buy a tiny N scale Police Box.

Hornby Police Box.

This is one of the Hornby Lyddle End range of resin models. I bought one, as well as some buildings, online since they don’t seem available in NZ easily. Oh, if you’re a retailer in NZ (and elsewhere actually) and have an online shop here is a hint – listing products you don’t actually have in stock and not telling people until they get to the checkout is not good!

The Police Box arrived and it is very cute. Perfect for my railway but also perfect to make some cufflinks from. The model is about 22mm high.

Lyddle End Police Box model.

It looks just like another TARDIS I happen to have here at home! I didn’t want to cut up my railway one so I ordered another from the UK. I got mine from Celestial Games and Books on eBay who were excellent. It’s interesting that ordering things from the UK is much easier than ordering from the US and shipping takes far less time than getting things sent from America.

I also bought some brass cufflink bases from a local online jewellery supply shop called Beadaholic. They, by the way, have an excellent online shop!

Model and brass cufflink base.

Next I used a modelling razor saw to carefully cut the model in half. This unfortunately results in the loss of the lamp from the top of the box but that is easily fixed later. After cutting I flattened the back of each half by rubbing them on some wet and dry paper.

Model sawn in half.

To attach the model to the bases I made some small brass backing plates. These were cut and filed from 0.9mm thick brass. I first made one then used that as a template to make the second. They are a little rough but at this scale they don’t need to be perfect and I like the hand crafted look. A quick clean up with some wet and dry and a final clean with steel wool finished them off.

Brass backing plates.

I was then able to solder the cufflink bases to the backing plates and later I could glue the model onto them.

Bases soldered on.

Next I repainted the model halves. I used small tins of Humbrol enamel paint – matt number 25. I love the smell of that stuff, reminds me of childhood and making models. Unfortunately I couldn’t recreate the fine lettering that was on the original models. These were actually stickers stuck to the model. Again the loss of detail doesn’t matter too much as these will be seen from a distance usually. I didn’t have a brush fine enough so I used a toothpick to put on tiny dabs of paint. White for the “Police Box” signs and white for the “Pull to Open” sign with some black lettering.

Painting.

I also made a replacement lamp using a tiny piece of styrene plastic glued on with superglue.

Replacement lamp.

Finally I superglued the painted model to the brass backing and gave the whole lot a coating of satin varnish, Humbrol 135, and I was done!

Little TARDIS in front of big TARDIS.

TARDIS cufflinks completed and ready to wear.

Right, where was I? I stuck the templates for the letters and the direction arrow onto the remains of the steel case.

Templates glued to the steel.

The letters and arrow were then cut out using the jigsaw and a hacksaw then filed and sanded smooth.

I then worked out how to make the pivot. I have no idea how real weather vanes do it. Looking online all I could find were silly toy ones. I found people online who make and sell real weather vanes but none explained how the pivots work. Perhaps it’s a trade secret? So I invented my own.

I am using a tube sealed at the bottom with a ball bearing at the base as a pivot and a bush near the top to stop the vane flapping about. The vane itself is attached to a straight steel shaft that slides into the sealed tube part. The whole thing is full of oil so it shouldn’t rust or wear out and it should provide a smooth rotation without being too sensitive due to the damping effect of the oil. Pictures should make it clearer.

Pivot parts.

The main body is simply a piece of steel tube.  Into the bottom of this is brazed a bolt, the head of which was turned on the lathe to make it fit into the tube. I put a small countersunk hole into the head of the bolt to locate a small ball bearing to work as the pivot. The ball bearing I got from inside an old spray paint can. These are what you hear rattling when you shake the cans. Now some cans have steel balls and some glass marbles. How do you tell which has which sort? Stick a magnet to the outside of the spray can and gently tip the can so the ball inside rolls past the magnet. If it is a steel bearing it will stop when it reaches the magnet whereas a glass marble will just roll past. Actually it makes no difference to me, I cut them ALL open and rescue what’s inside before putting the steel can out to be recycled! I have a jar full of the damn things.

Anyway, the bush at the top of the tube is just a nut I turned down to fit. The main shaft of the vane was some rusty old 1/2 inch steel rod I found in my old garage. The bush is pushed into the tube then held in place via a small hole in the tube I then plug welded through to hold it all in place. The picture above shows the relative positions. The whole tube is eventually filled with oil so the bush is actually totally submerged meaning it won’t rust or wear out in a hurry.

The pivot ball bearing.

You can see above how the ball bearing sits on the bolts at the base of the tube. The bolt is brazed into the bottom of the tube as shown. Later that bolt thread is used to screw the pivot into the main mounting bracket of the weather vane and it allows it to be turned to accurately position the direction markers.

To this pivot base (which doesn’t turn) the direction indicators are attached. I brazed the letters to lengths of 6mm diamater steel rod then welded these to the base.

Direction letters.

Once the base was done I brazed the direction arrow and locomotive to the main 1/2 inch steel shaft. I changed the rear of the arrow from my original design to one with more surface area based on this original LNER sign from Briglington I found online. I also added a small water shield made from a piece of tube and a washer. This gets welded to the weather vane shaft and it forms a cap that goes over the top of the pivot base to stop rain getting into the tube. This needs to be welded on very carefully so it is concentric to the main shaft so it won’t rub on the pivot base as the vane turns. I also added some balance weights to the front of the arrow head to balance the main vane.

A weather vane needs to be balanced with equal weight each side of the main shaft, so it spins easily, but has to have more surface area on the rear half than the front so it points into the wind.  I didn’t get this quite right (hey – it’s my first try!) so I needed to add weight to balance things out.

I then made the base which is simply a section of tube welded to a steel base. PArt way down the inside of the tube is a nut that matches the thread on the base of the pivot. This nut is welded inside the tube. I drilled a hole in the tube at the point the nut needs to sit then just plug welded the nut in place from the outside of the tube. For some reason I didn’t photograph this! The base was just some scrap 3mm steel plate I had that I cut to what I felt was a pleasing shape. The tube is welded to this.

Mounting plate.

This mounting plate is in turn screwed to a wooden base that is bolted to the eaves of the garage. The wooden base was made from some scrap marine ply I had about the place.  I needed to know what angle to cut the wood but since I didn’t have a ladder tall enough to get up to measure the angles I made a little measuring jig. This is just a long piece of wood with a T piece nailed to to top arranged so, with some force, it can pivot. To the pivot I hung a plumb line. I then took this contraption to the front of the garage and held it up making sure it was vertical using the plumb line. I then pushed it up onto the eaves. This moved the T piece to the correct angle.

Contraption for measuring roof angle.

I then transferred that angle (turns out it was 20 degrees) onto the wood. Simple! The steel mount is simply screwed to the wooden base which is in turn bolted to the garage eaves. I turned up a pointed plug from a piece of dowel to fit to the bottom of the mounting bracket just to finish it off. The steel base was primed with a zinc rich primer.

Wooden base for steel mounting bracket.

Another detail I didn’t get a picture of was the spacer used between the base and the mount. It goes on the threaded part of the base and is carefully cut to the right length so that when the base it turned fully into the nut in the base the direction pointers point in the right direction. I used a pice of 1/2 inch copper water pipe. Using copper means the spacer has some give in it. You can snug the base up very tight into the mount, the copper distorting a little for the last part of the rotation so you can get it in the exact right place. I got the idea from the crushable spacer used in an MGBs rear differential to set the differential pinion gear.

Oh, about now I discovered I could buy online some really nice locomotive cufflinks that happened to be almost the same as my weather vane. So I bought some! $30NZ shipped from the UK, arrived in 4 days! Cheaper than buying locally.

Locomotive cufflinks!

With everything done it was just a matter of painting it all. I painted the steel with black satin paint. Obviously I used the right stuff since the spray can has a picture of a weather cock on the front! Who wants a giant cock on their roofs?!? I painted the wooden base white and I used carriage bolts (appropriate for a railway themed vane) to bolt the whole thing to the eaves. So the vane sits into the base which is filled with oil to cover the ball bearing and steel bush. The base is in turn screwed into the mount via a spacer and a into nut welded inside the base shaft and the whole thing is bolted to the garage.

Finally painted.

Finally with everything painted and finished I just needed to bolt the whole lot to my garage roof. Luckily my father had a ladder long enough and he came over to help me by holding the ladder while I clambered up to bolt it all in place. Once done we stepped back to inspect it all and this is how it came out!

Finished weather vane.

Now if you wondering why the N-S letters are backwards in this view there is a good reason for this. As my mate Dave pointed out to me weather vanes will have one correct orientation. From other views the letters will be backwards. I was to busy making sure I got the N-S-E-W order the right way round to notice! Mine is the right way round when viewed from inside the house!

Yep, that was totally planned, not lucky chance at all…..

View from indoors.

Finally, to prove it works, a little film on YouTube.

Works at night too!

So in light of all that I decided to start a new project – a railway themed weather vane to put up on my spare garage. Currently my house and spare garage (I have two – doesn’t everyone?) are being painted and they are looking really good. The peak of the spare garage roof is the perfect place to put a nice weather vane which should be a fun little project to build.

Spare garage soon to be painted.

I seem to be going through a railway phase just at the moment. Reading everything I can about old British railways, locomotives, stations, etc, etc. I’ve always been a bit of a trainspotter I guess. I decided to make this weather vane with a railway flavour. I knew I needed some suitable steel and looking through my junk cupboard I found an ancient PC whose case I could cut up. It is a 486SX-25 so slightly past it’s best. The top cover of the case is nice thick steel – 1.2mm thick to be exact.

Nice steel case.

I decided to reuse this steel to make the bulk of the weather vane. I hunted online for a suitably representative locomotive that would look good as a sillouette. In the end I decided on a LNER J83 tank loco. The Hornby model railway provided me with a nice clear side view of one so I copied the image and put it into a graphics program, turned it into a black image and printed it out. I used that image to take measurements from which I then scaled up 3x to transfer onto the steel cover.

Outline drawn onto the cover.

I did tweak the design a little to make it clearer and easier to cut out. I just drew the design onto the steel with a Sharpie, some of it freehand, some with a ruler. The wheels I made slightly oversized. A screw jar lid made a useful template to trace around for those!

Once drawn out I drilled holes in strategic places then, using a metal cutting blade in my jig saw, I started cutting it out.

Holes drilled to allow the pattern to be cut out.

It took a lot of careful cutting but eventually I removed most of the bits that aren’t locomotive.

Shape roughly cut out.

I then started filing, grinding and cutting the edges to clean up the shape. I found that was well as using the bench grinder and hand files I was also able to use my joggler, a panelbeaters tool used for bending and punncing holes in steel for plug welding through. I used it a lot when restoring my MGB. With it I was able to nibble close to the line in some tricky spots which then minimised the amount of hand filing needed.

Joggler tool.

After about an hour and a half of mainly hand filing the main cutout was done. I gave each side a quick once over with the random orbit sander to smooth off the rough edges.

Finished cutout.

About now I was felling pretty pleased with myself when I suddenly realised ‘Bugger, the damn thing looks a lot like Thomas the Tank engine‘. Bah!

<trainspottervoice> Oh well, everyone is sure to realise my locomotive is based on the LNER J83 where of course Thomas was based on an LB&SCR E2. Obviously completely different locomotives! </trainspottervoice>

There is just no way I am going to paint the thing blue and red now though!

Next I need to make a direction arrow in the style of the old station Way Out signs and make the letetrs for the direction pointer. In preperation for that I used an online font sampler to print out the cardinal directions. The font is Gill Sans which is the font used by the LNER railway back in the day for all their signage. Since I am using their loco it seems fair I should also use their lettering! I will glue the letter onto the steel then cut those out.

Gill Sans font for the cardinal point markers.

More updates soon.

Part two is now available here.

Click on the pictures to see larger versions.

A film is available on YouTube showing the pistol and how well it compares to a standard Nerf Maverick.

The main body is simply a length of PVC pipe.  The barrel assembly and the two centering rings are screwed into one end.

The main spring goes between the piston and the end cap. To assemble this you simply remove the ring from the end of the plunger and push the end cap over the end of the rod then reattach the pull ring.

With the end cap screwed into place the weapon can be cocked. As you pull back the plunger the telescoping rod pulls out until the internal stop hits the back of the catch. Then as you pull further the rod and piston move backwards compressing the spring. When pulled all the way back the catch protrudes through the end cap. The catch wire is bent so that the plunger pushes it aside as it passes. The catch wire can then move back into the notch in the end of the plunger preventing it from moving forwards again. Once the catch is locked into the notch the telescoping section can be pushed forwards. This is done to avoid having the plunger rod having to extend past the rear of the pistol. To release the piston to allow it to spring forward all you do is push the wire out of the notch.

The wire is moved by pulling the trigger which rides in a trigger housing. The trigger itself is made from a solid piece of aluminium cut and filed into shape.  This is attached to a flat aluminium plate by two small screws. One screw also holds a small brass tab used to attach the trigger return spring. At the other end of the plate is attached another piece of aluminium with an angled ramp cut on one end.  This piece is the part that actually pushes the catch wire aside to fire the pistol.

The trigger housing is made from a piece of 22mm wide aluminium extrusion. The housing is what the pistol grip attaches to as well as holding the trigger and trigger plate. Holes in the housing correspond to the holes in the end plate and barrel spacers so that one of the three screws holding each of these in place is also holding the trigger housing to the main body. The front screw also holds the trigger guard in place. At the rear is a small rectangular cut out the catch wire passes through. And there is also a small screw used as an attachment point for the catch spring.

The trigger and plate slot into the housing and are a nice, sliding fit. The bolt that holds the pistol grip in place passes though the trigger plate. The spacer mentioned earlier is what allows you to tighten the bolt to secure the grip but still allow the trigger plate to move freely back and forth without allowing it to move up and down. With the bolt done up tight the grip is held securely to the trigger housing. The acrylic side plates are then attached with the 3mm bolts. The top of the plates have a step filed into them to fit snugly over the sides of the trigger housing. This prevents both the grip from rotating on the housing and also prevents the side plates rotating on the grip.

With the trigger guard in place a long screw passes through the housing and guard to attach the housing to the gun body. This screw is also what the trigger return spring hooks onto. The spring pulls the trigger plate forwards. When the trigger plate is forwards the ramp at the rear of the housing is also forward, away from the catch wire.

When you squeeze the trigger the plate slides backwards. The ramp on the end of the trigger plate also moves back and the ramp pushes the catch wire to the right, out of the notch in the end of the plunger and the pistol fires. The spring then returns the trigger forwards.

With the trigger housing attached to the body and the catch spring in place you can see above how this works.

Above you can see how the NERF dart fits into the barrel.

And finally some pictures of the (mostly) finished article.

Finally a shot showing the advantage of the telescoping plunger. With a straight plunger the pistol would be much longer.

What’s left to do? Well, it can obviously be cleaned up and painted. I also want to remake the ramp piece on the trigger plate from steel rather than aluminium as this wears too quickly. I could also make a small cover to go over the rear of the gun although this would be purely for looks rather than any functional reason. I would hesitate to paint it black as then you start getting into ‘real looking gun’ terriority and people start getting twitchy and I don’t really want twitchy armed offenders squad members on my doorstep!

The range, well that’s tricky to say since the darts don’t fly that well as they are fairly light. Around 8 – 10 metres or so (26 – 33 feet) the darts are fairly accurate and travel fairly flat. Any more than that and you need to start lifting the barrel to get more range.

In the film on YouTube all shots were fired from 7 metres (23 feet) away. The standard Nerf Maverick can barely make that distance.

Click on the pictures to see larger versions.

A film is available on YouTube showing the pistol and how well it compares to a standard Nerf Maverick.

Homemade pistol with NERF Maverick.

Now, this isn’t new. In fact there are forums for doing just this as well as some very impressive homemade NERF guns around online. The site that inspired me most was www.boltsniper.com where Evan Neblett has documented his very impressive and remarkably sophisticated homemade NERF guns. Even more impressive is these have been made by hand. I have the luxury of having a small lathe!

My effort is not quite so impressive. I just wanted to see if I could make a simple pistol that would fire a NERF dart better than the original toys. This is how I did it. Generally the photographs should explain it so I will try to keep the text to a minimum.

The pistol is made from 32mm ID PVC pipe, some aluminium extrusion and aluminium pipe, wood for the grip and various pieces of metal and plastic. The main spring is one I got from Bunnings warehouse. This gun should be able to take a cut down AR-15 spring as used in the Boltsniper weapons but these aren’t that easy to come by in New Zealand. I believe I am legally allowed to buy one but by the time I found that out I already had the Bunnings spring. I may still get one to play with. The idea of a toy gun using a part from a real one appeals to me for some odd reason…

The spring seems to be this one from Century springs. It is 11/16ths (0.687) OD, 6 inches long and the wire is 0.072 diameter with 29 coils.

Pistol stripped down to component parts.

I will go through the parts in turn.

Here we see the aluminium trigger guard and the screws used to hold the pistol together. I used stainless steel screws. The two small springs are the trigger return spring and the release catch spring.

Next is a bolt and insert that holds the pistol grip to the trigger housing. The insert is a 16mm diameter piece of steel with a 6mm hole threaded thought it for the bolt. On either side is a 3mm threaded hole. The bolt has a small spacer under the head the purpose of which should be clear later on.

The pistol grip is a piece of wood 18mm thick. A 16mm diameter hole is drilled through the grip to hold the threaded insert. A long hole is drilled vertically though the grip to allow the 6mm bolt to pass through it into the insert. The grip is bulked out with an acrylic plate each side. The plates are filed and sanded to provide a comfortable shape. Each plate is held with a 3mm screw that screws into the metal insert in the handle. Each acrylic plate extends past the top of the wooden grip so that when the grip is attached to the trigger housing with the single screw it won’t rotate.

The barrel is made from 19mm diameter aluminium tube. It is held inside the PVC body by two machined rings made from plastic chopping board.  Each ring is held into the body by three screws. Two circlip grooves are machined onto the outside of the barrel and the plastic rings slide up against the circlips to accurately position the barrel which then can’t move either forward nor backward. I used an o-ring under one clip to ensure the barrel was a tight fit and would not rattle or rotate in the housing. A standard NERF dart is 1/2 inch diameter, much smaller than the barrel. I used a piece of black irrigation pipe that is a 1/2 inch internal diameter which the NERF darts are a nice, tight fit into. I machined the outside of the pipe to make it a very tight push fit into the aluminium barrel.

The end cap is also made from machined chopping board. This is at the rear of the pistol and the main spring pushes against this when the pistol is cocked. The hole is to allow the plunger attached to a piston to pass through the rear of the gun. A fender washer is attached to the plastic cap with two screws to provide a flat, hardwearing surface for a music wire catch to slide against. The wire is pivoted through the end cap. A small brass piece was pushed onto the end of the wire to stop it falling out. The inside face of the cap is chamfered so the piston plunger will more easily pass though the hole as the piston and rod are pulled back.

The piston is again plastic chopping board. I machined an o-ring groove into it to provide a good seal inside the pistol body. The main piston rod is made from brass tube. Another o-ring is under the head of the piston rod to seal that against the piston. The plunger is designed to be telescoping.  The telescoping section is made from steel and is the most complicated part of the pistol. I used a 1/8 inch steed rod to make the moving section. On the far end of this rod is a metal piece to attach the pull ring to. On the other is a small stop. These ends are silver soldered to the rod. In the middle, but free to slide,  is the main catch piece.  This is machined so that it is a tight fit into the brass tube of the plunger rod and it is soldered in place. The 1/8 rod can now slide in and out of the brass piston tube but it won’t pull out of it. The catch piece has a chamfer on the end so it can easily pull through the hole in the end cap of the pistol. It also has a groove machined into it. It is this groove that the music wire catch hooks into to hold the piston back in the cocked position. Because the stop on the end of the 1/8 rod that is inside the brass tube is a reasonably good fit I drilled holes in the brass tube to allow air to escape from it as the telescoping section moves inside it. I should have made the internal stop on the end of the 1/8 rod smaller so this wouldn’t have been necessary.

Continue onto part 2 here: http://www.asciimation.co.nz/bb/2011/01/19/building-a-better-nerf-gun-part-2

Finished steam punk record player.

Before I bore people with details and photos here is a film of it in action on YouTube.

Yes, it’s a steam powered record player. Playing a punk LP. The Sex Pistols – God save the Queen (Victoria obviously).

You can’t really get more steam, or punk, than that!

And yes, I know it sounds terrible.

For those who haven’t followed the whole story here is a brief catchup. This all came about when I decided to build my own small steam engine from bits of junk around my garage. I built the engine first (named Nigel after Sir Nigel Gresley) then I made a boiler from some copper water pipe. After making the boiler and a small throttle valve I was able to test the engine running on steam. Now I knew the engine ran I started on the next part of my scheme – to use it to turn a record. I made up a firebox and heavy wooden platter. By this stage I already had it in mind to create the only true steampunk project on the Internet.

Now steampunk is an odd thing. It’s not really my cup of tea and I got somewhat annoyed after I posted details of my Google Maps Brass Wristlet Navigator that people called it steampunk. That wasn’t the intention! It just happens to be made from brass. But I thought well, if people want steampunk then let’s do something that’s really steampunk. Hence the steam powered gramophone.

My original plan was to use an old fashioned gramophone style pickup and horn. Unfortunately this didn’t work! So I went instead for a more conventional tone arm and pickup arrangement with the sound played through my phono pre-amp and stereo. That was tested and worked well so I next moved onto how to measure and regulate the speed. For this I used some magnets, a coil as a pickup and an Arduino driving a servo to move the throttle to control the speed.

Once I knew that would work I pulled everything apart, finished up a few details like a wooden drawer in the base to hold the electronics and batteries and I made a small brass meths burner to provide the flame. I varnished all the wood and reassembled everything. The visible wires are run through shoelace to give that fabric covered wiring look. All the brass and copper was polished then left to tarnish again to give a nice patina of age and the wooden parts were deliberately varnished in a rather slap dash fashion to give the impression of age (well that’s my excuse).

I also uploaded a film of the first actual test with steam using a different LP before I risked my Sex Pistols one which I have actually grown rather fond of.

First test run on YouTube.

The whistling of the safety valve was totally serendipitous, it wasn’t planned that way but it make it handy to know when it is venting steam pressure. You adjust it by changing the tension on the spring.

Anyway, some pictures of the finished device. I don’t have any plans for this thing. I basically made it up as I went along and experimented to see what would work and what wouldn’t.

The Arduino is a bare bones breadboard version I made up after I had things working well on my Duemilanove following the instructions here.

What’s next? Well, the software still needs some work. One problem is as soon as the platter starts to spin the PID controller immediately pulls the throttle to the minimum RPMs. The throttle should remain at the half way point until things stabilise for a while otherwise the throttle setting can be too low for the engine to continue running. The PID also needs tuning some more to make it run well. With a bit of work I should be able to get the speed regulation a bit more constant.

Anyway, progress is being made. As mentioned I had made up a little mount for the detection coil. This is just some scraps of brass I had in the junk box so I made a little stand with a sliding top held with thumbscrews made from more of those document interconnect things. It can adjust up and down as well as in and out so I can get a good signal from the 6 magnets around the perimeter of the platter.

Coil mounting.

The other thing I did was fit an old 0-5 amp meter to give some (vague) indication of RPM. I found this on TradeMe for $3. It was described as being sticky and that the calibration was out but it just looked so great I had to grab it. How can you not use a meter labeled ELECTRO-TEC! It took a little while to arrive but that was due to the postie sending it to the wrong house. Luckily my neighbour came and dropped it off to me. I stripped her down (the meter – not the neighbour) and cleaned and adjusted it and I also removed the current shunt. I worked out what FSD was (20mA) and just wired it up with a series resistor so I can drive it from 0-5 volts. I mounted the meter into the top of the base. It protrudes in so it prevents the drawer coming all the way out. Drawer? Yes, I don’t think I mentioned that before. I decided to add a shallow drawer under the base board. This is to give me somewhere to hide the electronics as well as to hold an oil drip tray under the engine bearings.

Meter mounted in base.

The other small thing I did was mount the cheap pickup I got onto a small piece of brass and soldered that to a tube that slides into the end of the tone arm. Currently it is held on with black tape but I will need to thing of something better there. It’s fully functional but not yet aesthetically pleasing!  I wired up the pickup head and took the wires to a 5 pin DIN socket in the plinth base. A cable goes from that to my stereo pre-amp. I finally used part of that old printer I pulled apart. A short length off one of the shafts was inserted into the end of the one arm to provide extra weight on the short end. Now the adjustable weight can be used to set up the stylus pressure on the needle. Pity I have no idea what that should be for this particular stylus!

I also added a little bracket made from brass and copper to the plinth to the hold the tone arm when it isn’t running on the record.

Tone arm bracket.

I tested the audio side of things by hooking the arm to my existing pre-amp and spinning the record by hand. That worked great! I get a lot of volume from it. With the tone arm tested and working well I stared looking at my servo controller on the throttle. The idea was always to use a small hobby servo driven by an Arduino to control the throttle position based on the RPM as measured by the sensor.

My friend Mike and I spent a lot of time chatting about different algorithms to use to actually move the servo. The throttle isn’t necessarily directly proportional to the speed so what you do is this:  If the RPMs are too low you open the throttle a bit. When it speeds up you close the throttle a bit.  If it goes too fast you need to close the throttle then open it again if the speed gets too low.

Now a person can do this easily and this is how I tested the engine to figure out the right PSI and drive ratios I would need. I just tweaked everything so that at 10 PSI the platter goes at approximately 33 1/3 RPM with the throttle in mid position. But for a computer to do this, especially a little one like the Arduino it is a bit harder.

After discussing various algorithms for a bit Mike made the comment it was a pity we didn’t do more control theory papers at uni all those years ago.  It suddenly occurred to me I should ask my colleague Gareth at work since he has done robotics and other such things in the past. Turns out he has done control theory and after explaining my problem to him and explaining my approach he  said what I needed was a ………

It took him a while to remember! But it came back to him. What I needed was a PID Controller. You can read that Wikipedia link to get the exact details but basically a PID controller is a feedback controller. You tell it what value you want to maintain. This is called the set point. Then you give it the actual current value you are at. This is the input value. The PID works out the error between the two and gives you an output variable you use to modify the process.

So, in my case is I have a machine which is my steam engine driving the platter. I want the platter to rotate at 33 1/3 RPM. With my coil, a little circuit and some software I can measure the actual current speed. And I can control the speed by changing the setting of a simple valve using a servo that takes a number to tell it what position to move to.

Now I had horrible thought about having to implement all this myself in software but I did a quick search online and discovered someone has already written a PID library for the Arduino! I love the Arduino and this is what makes it great. You want to do something and chances are it’s already been done and the libraries are available and free for you to use. So I downloaded the PID library.

With the Arduino PID I can tell it the speed I want, 33 1/3 RPM, and tell it the speed I have currently and it will give me a number I use to drive the servo in order to change the speed. There is some configuration of course. You specify the output range of numbers you want and you also specify three parameters that tune the behaviour of the PID.

My throttle valve I designed to have a 90 degree throw from 45 degrees to 135 degrees. I use a simple direct linkage from the servo to the throttle so I set the PID to output between those values. So the Arduino is set up to measure the pulses from my coil as the magnets pass by it. I have the coil hooked into an Arduino analog input. You need to use a snubber diode across the coil as you do get a positive and negative induced voltage for each magnet pass and the Arduino inputs don’t like negative voltages. I use the pulses to measure the RPM of the platter. With 6 magnets you get 6 pulses per revolution of course.

I then feed the RPM into the PID object and it does it’s weebly-wobbly magic I don’t understand and gives me back a number. I feed that number into the servo object and the servo arm moves. It’s really very simple! So with the PID configured correctly I should have a system that rides the throttle to maintain my 33 1/3 RPM. I am not actually trying to be that accurate with it so far so as long as the RPM comes out at 32, 33, or 34 I am happy. I might increase my accuracy depending on how terrible the sound is later but I actually want the sound to be a bit variable to add to the charm of the device. It is a  ye-olde-time device after all!

There are three values used to tune the PID and this is where it gets tricky. I basically used trial and error to set up the values for now and it seems to be working although it is probably not optimal. I have tried graphing the RPM I was getting with various parameter settings on the PID and that does show me what is happening in each individual case. But I am unable to easily compare different settings easily because although my Y axis is RPM and standard each time the X axis is samples. And the sample time depends on the RPM so it varies. I need to work out the X axis in actual time then I could compare all of the graphs together. For now though it is working well enough! Some example of the graphs I got are below are below. In the first the settings are wrong so the system was unstable and it oscillated about the set point.

PID output graphs.

To do all this testing I was driving the engine off air from my air compressor in the garage. I used my EeePC to program and monitor the Arduino as I was trying set up the PID. I wrote the values back up the serial port and later captured the text output to feed into a spreadsheet to make the graphs.

A small film of the servo being driven by the PID is here on YouTube. I set the servo to the 90 degree mid position when my sketch starts up but as soon as the PID start running it sets the servo to the slowest, or 45 degree, position. That’s why there is a big movement on the linkage when I start the platter spinning.

Before I could do all this I built a small bracket from some scrap aluminium channel to hold the servo. I extended the control arm on the servo with some strip brass so that the servo arm is the same size as the throttle control arm. I was able to then use a simple 1:1 linkage between the two. For the linkake I used little 2mm swivel ball links like those used on model aircraft and helicopters. I probably could have used a simple wire link but I love these little swivel joins and was dying to use them in something! I made a simple rod with a swivel joint on each end.

Servo mounting and linkage to throttle.

Linkage detail.

To cover the servo I made a small copper cover made from an old soaker plate I had lying about. It is also worth mentioning here that the drive belt I am using is a poly cord belt used on wool spinning machines (again off TradeMe). It comes in a long length that you cut to size then you melt the ends in a candle flame and press them together to form a continuous  belt. I used these belts with great success in my Wimshurst machine.

There are also two places where electrical cables need to pass into the base of the device so I made two little brass top hat style grommets to use here. The cables will be put inside old shoelaces for that old fabric cabling look.

Copper servo cover and linkage.

Top hat brass cable grommet.

So now everything is pretty much tested and working – not necessarily all together though. I know the steam engine works and that the platter can be driven on air. I know I can measure the speed and control it. And I know the audio pickup works well. So there is no reason it shouldn’t all work together on steam.

But next I have to pull it all apart to finish it all off! I need to varnish the base and make up a permanent circuit instead of the breadboard I am currently using. I also need to make a new, smaller burner as my old one was a bit aggressive. And I still need to machine up the boiler safety valve. That will be set to about 10 PSI which is quite low but my engine seems to run fine on that. It always starts easily so there is easily enough torque there. I believe even the little Mamod steam engine run at 12 PSI or so.

It’s getting there!

Test setup.

This is an emergency parasitic bike pump which is basically an air hose that lets you inflate a presumably flat bike tyre from a handy inflated car tyre.

Make in turn got it from the original Instructable which is here: http://www.instructables.com/id/Automatic-bicycle-pump/

If you look at the comments in both of those you’ll see there is a bit of discussion on this. On the Instructable there are some very odd assumptions being made about what car tyres and bike tyres pressures actually are. The maker guys are more concerned about the morality of it all (me included).

One thing that annoyed me was people seem to think that a car tyre inflated to 30PSI would be able to then in turn inflate the bike tyre to 30PSI. That’s obviously wrong as the air has to come from one tyre (at 30PSI) to the other flat tyre (at 0PSI) so you’ll end up with them both at some pressure in between. I assumed they’d both end up at the same pressure.

In the end I decided the easiest way to see if this works was to try it!

So off out to my garage I went. I knew I had one old air hose (red) off a dead foot pump so I dug that out. I also knew the air hose (black) on my air compressors tyre inflator unscrewed. Some rummaging in my junk box produced a brass 90 elbow. I cut the end off the junk pumps hose and pushed that over a hose barb screwed into the elbow. The air compressors inflator hose happened to match the thread on the elbow so, with a bit of teflon tape, that just screwed in. This was handy as I needed to keep unscrewing it between tests to re-inflate my car tyre.

Air hoses on manifold. The blue thing is the air compressor tyre inflator.

Now I don’t actually own a bicycle. But I have something close. It’s a small mini bike project I started about 10 years ago and haven’t finished (yet).  It was to be powered but a small 2 stroke engine and vaguely resemble an old Norton Manx racing bike. The car tyre is on my MGB.

The test subjects – a mini-bike with bike tyres and an MGB.

On the car I run at Yokohama C-Drive 185/65-R15s at 32PSI on the front tyres. This is a fairly typical sort of pressure for a normal car tyre to be at. The mini-bike uses small wheels from a kids bicycle. I replaced the tyres that were on it with some Hookworm 16×1.95 tyres since those were what looked most little mini motorcycle tyres to me. A label on the side of the tyre says to inflate them to 110PSI! I don’t actually know what typical bicycle tyre pressures are but I am fairly sure it is more than a car tyre.

Bike tyre says inflate to 110PSI.

Hose connections.

To measure the pressure I used a normal pen style tyre pressure gauge. Now this isn’t any kind of rigorous scientific study. I’m just some bloke messing about in his garage on a Sunday afternoon so I did it with bits of junk and what I had on hand. Don’t go worrying that I didn’t use the right kind of gauge or I didn’t have a proper bike or I should have used a red MGB instead of a green one. I just wanted to see if this idea actually works.

Pressure gauge.

So, here is what I did. I inflated the car tyre to 30PSI. Seems like as good a pressure as any and representative of what you’d get on a normal car. I made sure the minibike tyre was fully deflated – no pressure on the gauge. I hooked one end of the hose onto the mini bike then I hooked the other end onto the car tyre.

What happened next is the air could be heard hissing down the hose and the bike tyre would inflate. I would wait a while till the hissing stopped (5-10 seconds) then quickly remove both valves at the same time.

Not that last point is important. You must remove both hoses simultaneously. When you disconnect one tyre first the other tyre is still connected to the hose so all the air will leak out of it. The car and bike tyres both use what is called a Schrader valve. These have a small pin in the middle of them that, when pressed, opens the valve. With the with hose connected the pin is depressed and the valve open.  You could probably design the hose with a one way valve in it so air can flow from the car tyre to the bike tyre but not the other way. Then you could detach the car tyre end first without worrying about the bike tyre deflating again. It’s not too hard to detach both at the same time with minimal air loss though.

I did this 10 times and recorded the results. Between each try I had to unscrew the black tyre inflator hose from the manifold and use it to re-inflate the car tyre back to 30PSI again.

I also did one test at 35 PSI and another at 40PSI. I didn’t want to inflate the car tyre more than that so I stopped then.

Results.

The results are fairly consistent given my very unscientific method and they are quite interesting. As I thought the bike tyre doesn’t go to 30PSI of course. But the two tyres don’t end up at the same pressure either. I averaged the 10 attempts at 30PSI and here are summarised results below:

Start pressure: 30PSI

• Car tyre end pressure: 27.75PSI
• Bike tyre end pressure: 25.1PSI
• Difference: 2.65PSI

Start pressure: 35PSI

• Car tyre end pressure: 31.5PSI
• Bike tyre end pressure: 28.5PSI
• Difference: 3PSI

Start pressure: 40PSI

• Car tyre end pressure: 37PSI
• Bike tyre end pressure: 32PSI
• Difference: 5PSI

So, what does this all mean? The hose does sort of work. Air will go from the car tyre into the bike tyre re-inflating it somewhat. But the bike tyre will be at a lower pressure than the car tyre and both will be at lower than the starting pressure. If the bike tyre needs to be inflated to 110PSI as it says on the side wall of even the little kids one I have you’d need a car tyre that’s at a pressure greater than that.

Interestingly my tyre pressure gauge only goes to 50PSI so you’re probably out of luck finding a car with pressures that high! I think you’d need to find a handy aircraft to steal air (actually more likely nitrogen) from. Chapter 6 of this Goodyear Tire PDF shows the difference between aircraft and passenger car tyres and indicates aircraft run at 200PSI and cars at 35PSI.

Maybe someone would like to do a more rigorous test with better equipment and method and graph the results to see if there is some kind of trend happening. What I don’t understand is why they end up at different pressures? Is it just leakage when I remove the hoses or is there good scientific reason behind it.

The other thing worth mention is you really shouldn’t go stealing air from other peoples car tyres. One, it could be dangerous and two, it’s just plain rude! I would be very, very unhappy to discover someone had been messing with the tyres on my car without my knowledge.

I started trying to work out how to do they tone arm and audio pickup. My first idea was a totally manual old style gramophone. I came up with the idea of using copper water pipe and fittings to make a traditional mechanical pick up. First I took an old wooden baluster left over from another project and chopped a piece out to make a tone arm plinth. Then I machined up a piece of scrap plastic I had to make a bearing carrier for yet another skateboard bearing. Into this fits a piece of brass tube to which I had soldered a copper water pipe fitting.  I assembled a collection of copper parts to mock up the arm on the plinth.

Copper tone arm and original plinth.

The copper arm and pickup head (made from left over boiler tube copper) I liked but the plinth wasn’t right so it had to go. I made a new plinth from some scraps of wood I had.

After re-plinting.

I went ahead and soldered together the copper tone arm and pickup. The pickup is a section of pipe with a brass bottom soldered to one side and a brass ring to allow me to stretch a paper diaphragm over the  other, open end. To this I would attach the needle to run on the record.

Pick-up and ring.

The pickup head has a 90 degree pipe fitting soldered into the side of it for the sound to pass from the pickup. Since the pipe fittings are all designed to slide into each other I was able to cut a slot in the pickup tube and create a pin from a screw in the end of the tone arm. This held the pickup to the arm and also allows it to rotate partially.

Copper pick up arm pieces.

Pickup.

When it was all done it was a really lovely looking thing. Pity it didn’t bloody work! I tested it with some paper as a diaphragm and tried it on the platter. Unfortunately it is so heavy it creates too much drag on the record and I actually ended up killing part of my $1 test record (bought from the local charity shop) with it. I thought the needle was picking up a lot of fluff until I realised no, that was shavings of vinyl being cut from the LP! This should all have been obvious to me since I know how to set up a normal turntable arm and balance it. I think I was so pleased with how it looked and worked I just wanted to try it anyway.

So, back to the drawing board. Instead of a heavy metal arm I decided to see how things would work with a light weight paper cone. I removed the heavy copper arm and replaced it with a metal ring in a kind of gimbal arrangement. Into this I could insert a paper cone, with a sewing needle in the pointy end, that would then follow the grooves in the LP. This actually works reasonably well.

Gimbal mount for paper cone.

I don’t have a picture of the actual cone but I did film the result and put that up on YouTube as usual.

The sound, although there, is not very loud. Certainly not loud enough to be clearly heard over a noisy steam engine rattling away right next to it. I did some experiments with a small electret microphone hooked to a small amplifier. I put the mic right in the end of the cone and that would amplify the sound quite a bit but the quality was rubbish and if I put the speaker anywhere near the cone or mic I would get acoustic feedback. I also tried different needles and even a piece of sharpened bamboo (as used in the Gakken gramophone kit). None of it really helped.

The other problem is the sewing needle does horrible, horrible things to the records! I do have an old ABBA LP and the soundtrack to Saturday Night Fever in my record collection that probably deserve it but I just can’t bring myself to destroy vinyl with a sewing needle like that.

So, another rethink was in order!

Today I wandered along to my favourite junk shop (for those in Auckland it’s on Upper Queen Street just over the hill from Surplustronics – it’s the place that looks like a bomb has gone off in it) and had a hunt about there in their boxes of old tone arms. I was looking for an old stylus and cartridge to test out. The helpful but completely bonkers chap there helped me out and, from a secret stash, found me an old Philips head-shell/cartridge and stylus.  It’s an old GP204 if that means anything to anyone. I came home and soldered on some wires that I then plugged into my existing phono pre-amp and stereo. I then just hand held the head-shell over a record and turned the platter by hand. And that works! Worked very well in fact. Basically just the same as any other record player.

So, I needed to redesign my tone arm to take a normal turntable cartridge. I removed the cone ring and reused the brass axle. I cut a smaller ring from some scrap brass to make a new gimbal. The actual arm is a length of brass tube I found in the junk box. The gimbal ring rotates in the skateboard bearing in the top of the plinth. I soldered a brass tube through the tone arm and used two brass interconnects and a length of threaded rod cut from a machine screw to make the vertical pivot that allows the arm to move up and down.

Brass tone arm.

The counterweight was an amazing find. I was looking though my junk for something suitable to use as the weight on the end of the tone arm. My original though was to melt down some of the brass tyre weights I have collected over the years (I can’t not pick those up off the road when I see them I am afraid) and machine a little cylinder to slide over the end of the arm. Rummaging about though I came up with something better. It is a part of a machine found in a lot of workshops. This one was faulty so I had removed it and thrown it in the junk box. I just cut off the end and found it was perfect for the job. Here are some picture of it after I modified it.

Counterweight.

Know what it is yet? It’s an air compressor hose quick disconnect. They are used on the compressor and on air hoses to allow you to quickly connect things up and disconnect them again. There is a ring of ball bearings inside the connector that usually clip into the matching fitting on the air tool. By sliding back the other ring you release the balls which spring back allowing the connector to pop off. It turns out the hole in the middle of the connector is the exact same diameter as my tone arm. So the connector slides nicely over the end of the arm. The ball bearings also grip the arm so the weight won’t move on the arm unless you slide the outer housing back to release the balls. It is also almost the exact right weight. You change the balance by sliding the weight closer or further away from the pivot.  Without a cartridge on the end of the arm it balances perfectly.

Now, the stylus. This is where I have stopped for now while I decide what to do. My old cartridge and stylus from the junk shop (cost $10) do work so I should probably use them. But I also like the idea of getting a more modern and standard cartridge. Unfortunately these aren’t cheap and this project is meant to be made from junk where possible. I think what I will do is compromise and spend a few dollars to get a piece of brass tube to slide inside the arm. Then I can make a removable head-shell for it. I can start by attaching my junk parts then later, if I feel the need, I can make a new head-shell for a modern replacement cartridge/stylus.

There have a been a few other things done. I have tested driving the platter from the engine on air and I worked out the proper drive ratios needed. And I am working on enhancing the wooden base of the whole thing to make it look better and be more practical. I have also fitted 6 magnets around the rim of the platter and worked on the speed detection. I don’t yet have photos of all that so that will all be in the next update. Lots to do this weekend!