Dynamo.

May 28th, 2014

Today I started restoring the dynamo and distributor. I also had a couple of presents arrive. I decided to go ahead and buy the water pump and the fuel pump. I’ll need them sooner or later. The Austin 7 doesn’t normally have a water pump instead relying on a thermosiphon effect to circulate the water. Since I am blowing the engine and probably won’t be running a fan I figure a bit of extra circulation won’t hurt. I am using a Davies Craig Electric Booster Pump from here: http://dsrturbo.com/electric-water-pump/9001.html

These are available on TradeMe but are cheaper from here.

It is plastic and looks a bit modern but I can hide it away somewhere in the engine bay I think. I also bought an electric fuel pump (also plastic). I am using a Fuelflow Ecco pump like this: http://www.fuelflow.co.nz/FF_cms_03/eshop?page=shop.product_details&flypage=&product_id=65&category_id=28

Funnily enough you can get those on TradeMe from the company cheaper than on their own site. That can be hidden away in the boot beside the tank so won’t be seen at all. I didn’t want to use the mechanical pump and my blown cam doesn’t have the lobe for one anyway. Both these pumps run on 12 volts so I will be converting the car to 12 volt operation too.

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Both are quite small, water pump on the left and fuel pump on the right above.

I also started collecting together all the different engine bits I have. I need to work out which block will be the best to use. I’ll ask Ian nicely for advice there!

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On my original block I found the water branch stud holes have been coiled or else had the studs drilled out and rethreaded. I dug out the loose bits.

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I am wondering if it is possible to braze up those holes and redrill and tap them. I’d need to heat the whole block first I imagine but it should be possible to rebuild the mountings with braze. On this block they are weak and cracked. The other block is more intact but some of the head studs holes will need coils.

Next I tackled the dynamo which was filthy. I’ve never pulled one apart before so was using the red book and this site to help. Getting it apart wasn’t too bad. I use an air impact gun to remove the nuts on the ends of the shaft. You can easily hold the armature in a cloth and spin the nuts off without having to clamp the gears in the vice like the book suggests.

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The commutator was very scored. The book says it should be 1.28 inches diameter (32.5mm). Mine measured about 31mm at the lowest point. The books don’t tell you what the minimum is though. I did some quick electrical tests and it seems electrically OK so I chucked it in the lathe and cleaned it up. There is still copper there and the brushes will still reach it so it should be OK.

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When you machine it like this the copper needs cleaning out between the commutator sections. As mentioned in the book I made a scraper from an old hack saw blade. I held each side of the blade against the side of my bench grinder to flatten the teeth and I angled the end so I could get right between the sections. You then use that as a scraper to make sure there is a gap between the sections.

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I cleaned up the housing and field windings as best I could. The insulation is quite deteriorated but the enamel on the exposed wire seems OK.

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I took apart the end cap to check the bearing. It was so filthy the bearing wouldn’t turn. I washed it out in kerosene but it’s knackered so I will need a new one. Interestingly the bearing is made in the USA. I guess this dynamo has been serviced before.

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The other end, with the brushes got a good clean too. When most of the crud is off I might put it in the ultrasonic cleaner. I will need at least a new third brush since the one in there is broken and a large chunk is missing but it’s easy to replace all three. The VAR spares have them and they come as a set anyway.

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The problem with restoring something like this for the first time is knowing if it is worth restoring or would I be better to just get another on in better condition? I then started looking at the distributor but by now the kero fumes were giving me a headache so I didn’t get far.

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This will also need a damn good clean. What you see above are the weights for the automatic centrifugal advance. When the distributor spins the weights move out and they pull on little toggles that twist the shaft with the points cam on it. That is what gives you the spark advance at higher speeds. You can see in the second picture the weights are apart. I am not holding anything there. I think in theory the springs should pull the weights back in automatically but the mechanism is so stiff it just sticks. Hopefully I can clean and lubricate it so it works.

Tomorrow though is a darkroom day. Been practicing my black and white photography!

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