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donkeydrop
United Kingdom
77 Posts |
 Posted - 22/12/2003 : 11:47:27
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My PA/B dynamo is a Rotax 3 brush converted to 2 brush by someone years ago. It is currently not working!
I have joined to F & D terminals together and get a measly 3 volts when spun up.
I took it out of the car last night and had a closer look and found the Field coil connection was open circuit (to the casing) and the D connection was shorted to the casing even with the brushes out - neither of which is good news. The inside is very soggy with oil and the wires are saturated and the covering is in poor condition.
I suppose I have 3 options:-
1. Take it apart and sort it. If its just wire damage I might be able to sort it. I got the nut off but the cross shaft is firmly affixed. At this point I chickened out!!!
2. Get a recon unit from another car or original P type also modified. Do other cars use physically compatible 2 brush units?
3. Get this one reconditioned. Can anyone recommend an expert preferably in the Midlands UK
Any advice would be appreciated.
Thanks in advance
John |
Edited by - donkeydrop on 22/12/2003 11:48:18 |
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DickMorbey
United Kingdom
3683 Posts |
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LewPalmer
USA
3254 Posts |
Posted - 23/12/2003 : 02:30:23
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John,
Although I can't recommend a local specialist (I'm in the US), I can tell you that I had a similar situation back in 1984 when I was lining in England and restoring my J2. I found the solution with a local Lucas service depot (in Redhill, as I recall) who actually had a set of field coils in stock. He installed them and voila a perfectly good working dynamo. I subsequently overcharged and burned out the armature, but that's another story.
Cheers,
Lew Palmer
Registrar, NAMMMR |
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donkeydrop
United Kingdom
77 Posts |
Posted - 23/12/2003 : 08:45:04
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Thanks for the advice.
I have decided to put the dynamo back in the car and get it reconditioned in January. (I have made contact with someone to recon it).
However the plot thickens. Like a complete loon I lost the timing when removing the dynamo and am having difficulty recovering the situation.
The bottom end is I think correct. No 1/4 is at TDC according to the marks on the flywheel and the dynamo (which has two Xs engraved on the bottom gear which faces the rear of the car) has been replaced with the x-shaft along the length of the car.
At the top end No 1 valves are both closed so it can't be far out. My book speaks of timing marks on the cam gears but all I can see is a red blob on the gear with nothing to line it up with.
Can anyone tell me what I should be looking for.
John |
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Peter Green
United Kingdom
1682 Posts |
Posted - 23/12/2003 : 11:04:36
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John,
You have got the bottom end correct, with No 1/4 cylinders at TDC the dynamo fork (x-shaft) should point along the length of the car as you say. At the top end you should have no trouble if you have not disturbed the mesh of the vertical drive pinion and the camshaft. If you have, the points of the lobes of the camshaft for No 1 cylinder should be turned so that they are pointing at 10 to 2 when viewed from the front and the pinion fork (x-shaft) should be at 90 degees to the centre line of the engine (pointing across the car). There are timing marks engraved on the gears of the vertical drive pinion and camshaft bevel gear but they are always very dificult to see and they DO NOT line up at TDC. There is one further point, if the engine has been turned over with the dynamo removed make sure that the distributor is firing on No 1 cylinder.
I hope this is the information you required.
Peter.
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Edited by - Peter Green on 23/12/2003 14:13:55 |
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donkeydrop
United Kingdom
77 Posts |
Posted - 25/12/2003 : 18:39:05
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Thanks Peter,
Your final remark was the key. I had forgotten that a 4 stroke engine has two TDC per cycle and I was 180 degs out. In a modern car that would have been goodbye valves!!
John
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