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Jean-Marie Raedts

Outside diameter Lucas C40 dynamo

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After installing a heatshield between the exhaust manifold and the dynamo/alternator location, I mounted my new Dynalite (alternator in dynamo housing). To put on the original fat (wide) belt, the alternator has to be pivoted towards the engine block. Even when the alternator touch the engine, I cannot put on the belt on the original pulley.

Does it means that the outside diameter of the Dynalite, 106 mm, is bigger than the outside diameter of the original Lucas C40 dynamo? My after market dynamo has only one outside diameter (102,2 mm), but I know that the original Lucas C40 is slightly different, for instance it doesn't have the same diameter over the total length.

A smaller pulley then the original one would solve this issue (and let also the alternator spin faster), but I cannot find it for the wide belt. May be I can try to take off the pulley and mount it on its axes with the belt in the groove.

 

I would be pleased with the dimension of the outside diameter of the original Lucas C40 and of course any other suggestion will be appreciated.

 

Jean-Marie

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I measured my spare C40 for you Jean-Marie.there are indeed two diameters, and on mine they are 97 and 104mm, arrived at by dividing the measured circumferences by 2pi. I don't have a vernier caliper with large enough jaws.

 

Tim

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Oops, I divided by pi of course!!

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102,7 and 96 mm, but 102,7 mm is the diameter that touches the engine

Edited by Z320

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Do you use a noched Flennor 900X20?

 

Edit: notched

Edited by Z320

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Use an old fan belt rather than a new one. Us old lags keeps a used fan belt in the spare wheel just in. Add. We know a new one is a devil to fit but will stretch within 100 miles.

Peter W

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Many thanks for the feedback. I learned that the outside diameter of the Dynalite (106 mm) is increased versus the Lucas C40 (102,7 mm or 104 mm as calculated by Tim). This makes it more difficult, impossible up to now, to mount the wide belt. I didn't try yet the notched belt I have, but will do it during the next weekend. I hope that I can manage it by taking off the pulley, putting it in the belt and then mount the pulley back on the Dynalite axis. Otherwise a pulley with a smaller outside diameter of a slightly longer belt would solve the problem, but both alternatives are not feasible while these parts are not available.

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Longer belts are readily available provided you use a modern raw-edged 'cogged' type rather than the inflexible solid original. 17mm BX belts fit the pulleys just fine - though they do sit a little deeper in the vee. There is a wide selection of different lengths here:

 

https://simplybearings.co.uk/shop/Belts-V-Belts-BX-Section-Cogged-V-Belts-17x11mm/c4601_4790_4699/index.html

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Jean-Marie. I have the standard pulley and wide belt set up on my car. When fitting a new belt I move the dynamo as close to the block as possible, fit the belt round the crank and dynamo pulleys and have an assistant stretch it over the front edge of the water pump pulley as far as possible, being careful not to get their fingers trapped. I then push the car forward in gear and the belt simply winds itself onto the pulley. might work for you.

 

Tim

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Thank you all for your reply. In the weekend, I toke off the pulley of the installed alternator and put the groove of it in the belt and mounted the pulley back on the axis of the Dynalite. Not so complicated. I appreciate the suggestion of Rob and Tim. After the holiday period, I will follow both advises. Now the real test will be if the Dynalite will survive after the long drive first to the south of France and then towards the Stelvio in Italy. Mostly it is very hot over there in summertime and when queuing the overheating starts. I discovered already that the two layer heatshield I installed becomes warm at both sides (the 2 aluminium sheets are separated by some nuts) and that the body of the alternator also was warm after a drive of 100 km.

I keep my fingers crossed, and take my old dynamo with its control box with me.

 

Jean-Marie

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That's an attractive price for the 17mm BX belt Rob, does it still drive on the sides of the pulley as it should?

 

Tim

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Yes its what is known as a 'raw edge 'belt so it has no fabric on the sides and the rubber gives a better grip on the pulleys without excessive tension. Because its narrower than the standard belt it does sit lower in the pulley but its much less deep in cross-section so it doesn't seem to bottom out in the vee, at least on my set-up. There were 19mm versions available too which might be preferable but they seem to be difficult to get. The pic below is my 17mm one but it isn't from the company I linked to. I don't think standard BX belts usually have notches on the outside also but this does make the belt even more flexible.

 

 

post-7865-0-69231000-1530648470_thumb.jpg

Edited by RobH

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Thanks Rob, I'll definitely look at this option when I am next in the market for a fan belt, This might be some time, I have two spare Flennor ones at present and that on the car is still in perfect shape.

 

Tim

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