Alternators. Which way round?

[Stueeee]

What sort of room is there around it in the bay? There is a belt drive that could be used to drive a dinky little alternator and leave the existing dynamo where it is as a jackshaft.

That is what a lot of people have done, and may be the thinking behind the the OP's question about running an an alternator "backwards". The fan pulley on a coil ignition A7 motor is mounted on the front of the camshaft. As the cam is gear driven it rotates in the opposite direction to the crank. It's a fairly simple matter to weld some brackets to the top of the A7 dynamo casing and mount a belt driven alternator there.

Another solution which leaves the underbonnet looking original is to drive an alternator from the propshaft. I've done this conversion a few times for friends. There's a bit of jiggery pokery needed to get a taper bush style pulley mounted on the shaft. Firstly, need to get some weight off the pulley; you really don't need another flywheel on the propshaft.

Then there's the "ship in bottle" issue of the taper bush not going over either end of the propshaft. dowelling it and splitting it fixes that.

This is the pulley assembled on the shaft, this is as far forward as the pulley can go if the car still has the original cable brake cross shaft. This particular setup has been on the car and working for a few years now.

 

[wookie]

the headlights do need proper bulbs, and really something a fair bit bigger than the 24W jobs that the factory fitted.

Are you really going to drive it at night that much ? Most of my old stuff I don't take out at night as it's too slow and too small to be safe amongst modern idiot drivers.

Whatever you do please make it easily reversible so the next custodian of that car can revert it back to stock if they wish. I've several classic vehicles and I have tweeked them to better suit my needs but nothing that couldn't be undone easily if required.

 

[cardiffrob]

Not very original at the moment, Wookie. I salvaged it from a garage loft after decades of it being a spares source, hence it having a new body and a cobbled-together engine. The old dynamo system either under or overcharged the battery and then melted so I didn't want to trust it. I have dozens of old A7 dynamos to play with but would have preferred a modern system. I'm toying now with a Motorbike Alt with some sort of belt drive with the old cooling fan pulley acting as a tensioner. Might work.

 

[wookie]

The old dynamo system either under or overcharged the battery and then melted so I didn't want to trust it.

All my old vehicles are still using their dynamos, setting up the regulator can be a bit fiddly but once it's set it hardly ever needs any attention but you do need a old moving coil meter to set them up, a modern DMM is no use.

I try and keep my stuff as original as possible but with an eye to keeping it useable, I much prefer a lightly modified classic that is regularly used over a totally original that is hardly ever used. It's your car so do with it what you want, if the dynamo won't provide the output you require by all means change it but I hate seeing perfectly usable old kit being junked because the owner couldn't be bothered to learn how it works (not accusing you of this)

 

[cardiffrob]

I wanted to get 12 volts out of the original 6v dynamo anyway so there were going to be some 'issues' whatever I did. I don't have any 6v parts but have loads of 12 volt stuff that are easier to change if anything dies.
I take it that poly belts are fairly standard in their design with regards to spacing of the grooves?

 

[sardine]

They run in either direction but the fans don't.

There are clockwise and anti clockwise fans available.

 

[wookie]

I wanted to get 12 volts out of the original 6v dynamo anyway so there were going to be some 'issues' whatever I did.

I'm getting 12volts out of my 6volt dynamo but I'm damned if I can remember how, I know I swapped the regulator for a 12volt one but can't remember if I had the dynamo rewound or it just copes as it is. It's close to 15 years ago I did it so my memory is hazy, I know I have a Lucas reg out of an old Landrover hiding inside the gutted original regulators housing. Other than that it was just swap bulbs, coil etc to their 12volt equivalent and add a 12volt battery. The starter doesn't half fly round, you've just not got to use it too long or it will unsolder itself. I've had to fix it once so far.

That reminds me I have to fix the dropper circuit I made as the fuel gauge will only work on 6 volts.