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Author Topic: Aprilia bottom gear  (Read 1938 times)
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davidwheeler
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« on: 24 June, 2009, 06:34:54 PM »

My gearbox struggles continue - the gears I have in at the moment still fall out of third and now top as well despite new bearings, which means the box must come out again some time.  So, I would like to fit a new bottom gear pinion.  I suspect that means I shall have to get one made or at least repaired.
1.  Any advice.
2. Anyone interested in a batch.
David
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David Wheeler.  Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
davidwheeler
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« Reply #1 on: 08 July, 2009, 04:52:29 PM »

I have decided to make some bottom gears pinions 38 19525 as repair is not an option.  The spare I have to hand is short and requires two spacers.  It seems to have been made that way.  The one in the car is longer, as in the drawing and needs only one spacer 38 19523 and I think it would be preferable to use this as a pattern.  Please could anyone lend me one?


* Aprilia gearbox layshaft 125 Kb.jpg (125.15 KB, 1000x622 - viewed 183 times.)
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David Wheeler.  Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
davidwheeler
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« Reply #2 on: 12 April, 2010, 04:26:59 PM »

I have at last achieved success with what has turned out to be a very difficult task.  Apparently, the gears are of a strange profile and the only way to make them is to wire cut them from hardened steel on a computer controlled machine.  This is expensive!  I am going to take delivery of a sample gear in the next few days and will try it in a box.  THIS IS A SERIES 1 GEAR.  The series 2 has a different number of teeth and I doubt if they are interchangeable.

I shall buy one for 250.  A batch of 5 will cost 200 apiece.  All Aprilia bottom gears are worn out, how about it chaps?  After all, Aprilias now sell for 20K.

David
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David Wheeler.  Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
davidwheeler
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« Reply #3 on: 05 May, 2010, 08:44:31 AM »

The sample fits and I am now getting a gear made and hardened.  I shall fit it and be there at the Sliding Pillar I hope.  As this is being made on a CAD wire cutting machine, the program will be available in case anyone else needs a gear.  I shall make a small charge for the use of it!
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David Wheeler.  Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
davidwheeler
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« Reply #4 on: 09 June, 2010, 08:49:48 AM »

Bottom gear now fitted and functioning very well.   Still the noise of straight cut gears but without the horrid grinding of the old worn one.    Made in Carlisle on a CC lathe for 250 + VAT.   Pattern exists in computer so further copies may be a little cheaper.
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David Wheeler.  Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
davidwheeler
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« Reply #5 on: 10 June, 2010, 08:28:30 AM »

I have also posted recommendations for engine machining, piston ring manufacture, engine balancing and radiator manufacture on the Lambda Technical Information thread
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David Wheeler.  Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
davidwheeler
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« Reply #6 on: 10 June, 2010, 08:35:19 AM »

I also tackled the third/top gear problem.  In my box of bits I found a slightly rusty third gear pair and sleeve.  I looked closely at them for the first time in many years and could not see any signs of wear.  Faintly, a dim memory surfaced of my first trip to Torino in Old Boot (or F*rting Annie as she was then) in 1971 and a trip to Cavalitto when I bought a new Aprilia head and valves and a carburettor.  I also bought third gears!  After a little fettling they were fitted and moving sweetly.
Behold, silent gears that I no longer have to hold in place!  I've also managed to stop the engine oil leaks by pinching an unworn sump and engine end plates from another engine.  The new new big ends do not rattle and oil pressure is superb.
See you at the Sliding Pillar.
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David Wheeler.  Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
davidwheeler
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« Reply #7 on: 18 February, 2011, 03:49:05 PM »

Alas, the engineers chose the wrong material/hardening parameters for the bottom gear pinion and the teeth have gone.  Does anybody know the correct specifications?
Meantime, I have fitted a reasonable gear from the toy-box.   This has taken some time owing to certain arcane differences.  In order to prevent myself (and perhaps others) making the same mistakes I have posted details on the technical information only thread, q.v. but please do not comment there (unless strictly relevant).
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David Wheeler.  Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
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