The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: benet on 26.08. 2012 10:23

Title: Tufnel gear
Post by: benet on 26.08. 2012 10:23
Hi Guys, I have replaced the tufnel gear on the auto advance with a new one and all appeared in order untill installation. The new gear seems to be binding excessively with the camshaft gear. I guess my first question would be if there are different profiles for the teeth on the tufnel gear's. It seems to match quite well with the old one and has the correct number of teeth, the OD of the old gear is about 0.5 mm greater then the old one but i expect that may be due to wear. It's difficult for me to measure the actual teeth as my vernier won't reach evenly into the bottom of the teeth cavities. Any ideas? Ben
Title: Re: Tufnel gear
Post by: bsa-bill on 26.08. 2012 10:43
Hi Ben
I had the same thing when I replaced the A/A unit with an alloy pinion, it was a fairly tight fit on the cam pinion.
However it all turned over ok so I figured I'd run it for a while and then check it, the "while" is still in progress so can't tell you what it's like yet, but nothing seems amiss noise or running ways.

Possibly just a repro part tolerance thing, however with tuffnel there's the added thought of teeth breaking, not sure what others might recommend but if it is not much a very slight easing of the three magneto mounting holes might give you enough to let it engage better, but go easy with the file.
Title: Tufnol gear
Post by: Triton Thrasher on 26.08. 2012 10:56
I think I've heard that a Tufnol gear needs backlash.

Try another one from Price, if still in business.
Title: Re: Tufnel gear
Post by: benet on 26.08. 2012 11:30
Yea Hi Guys, thanks for the feedback. I had initially thought that maybe running it will wear it in, however what is happening is that the pressure to the side seems to be fouling the auto advance and the mechanism is not operating freely. I'm concerned it will just stay in the advanced position. Ben
Title: Re: Tufnel gear
Post by: a10gf on 26.08. 2012 11:53
(sorry, slightly offt.)

What is it really: tufnol, tufnel, tuffnel ? Nigel Tufnel? > http://en.wikipedia.org/wiki/Up_to_eleven
Ok. I guessed tufnol (as TT had a go at fixing the topic title) > http://en.wikipedia.org/wiki/Up_to_eleven
"Tufnol is made from phenolic resin and woven cotton or linen fabric"



Title: Re: Tufnel gear
Post by: Triton Thrasher on 26.08. 2012 12:33
There is a little tolerance on the magneto mounting holes and studs. Try levering the magneto away from the engine as you tighten the nuts. That might free it a bit.

Title: Re: Tufnel gear
Post by: lawnmowerman on 26.08. 2012 13:23
(sorry, slightly offt.)

What is it really: tufnol, tufnel, tuffnel ? Nigel Tufnel? > http://en.wikipedia.org/wiki/Up_to_eleven
Ok. I guessed tufnol (as TT had a go at fixing the topic title) > http://en.wikipedia.org/wiki/Up_to_eleven
"Tufnol is made from phenolic resin and woven cotton or linen fabric"





Hi A10gf

According to this it is tufnell:

 Novasteen is an industrial laminate material with both electrical insulating and mechanical properties.

Novasteen is available in both natural and graphite impregnated (black) sheets or rods.

Novasteen possesses high load bearing characteristics which makes it an ideal material for silent gears, rollers and bearings.

Novasteen is known by various trade names for example SRBF, Auspeton, Micarta, F3 and Tufnell.

Novasteen is fully machinable and can be supplied in whole sheets/rods or cut to size and if required machined to your requirements by Modern Engineering.

Applications:

    Gears
    Stern tube
    Tension wheels
    Scraper blades
    Insulating pads
    Pulleys
    Bearings
    Slipperpads
    Bushes
    Rollers
    Insulating sleeves
    Mountingpanels
    Mixingpaddles
    Wearstrips

Jim
Title: Re: Tufnel gear
Post by: RichardL on 26.08. 2012 14:40
If diameter is the only issue,  and it seems as good a place to start as any,  why not reduce the diameter to that of the original? Then,  if tooth profile still leaves it too tight,  you could dress each tooth down a tad with a jeweler's file,  using due caution not to overdo it.

Richard L.

Edit: This seems to me far less agressive and,  possibly,  damaging than altering the mag mounting holes,  which may not help anyway if the problem is tooth profile.
Title: Re: Tufnel gear
Post by: Triton Thrasher on 26.08. 2012 16:47
A fibre gear with hand formed teeth will promptly fail in service, I'd almost bet.
Title: Re: Tufnel gear
Post by: Goldy on 26.08. 2012 18:15
Correct gear cutting is quite complex and that is always going to be a problem with re made parts. If its binding I would not run it because it will put extra load onto the magneto bearings which will lead to other problems.
Title: Re: Tufnel gear
Post by: RichardL on 26.08. 2012 20:20
I don't believe reducing the O.D. would amount to reforming the teeth.  I would agree that any major reforming would probably lead to failure.  If it were I,  I would examine the fit between gears with the tufnel gear in hand (not mounted) and decide if
 the problem is just a matter of a couple thou of an inch. If that was all that had to come off,  I would try hand-dressing the teeth; however, I might still fail. Success,  if it's to be had,  would feel good.

Richard L.
Title: Re: Tufnel gear
Post by: Triton Thrasher on 26.08. 2012 20:54
They don't cost much.
Title: Re: Tufnel gear
Post by: RichardL on 26.08. 2012 21:09
OK. I was going with the theory that all the new ones might be oversized; but,  no clue,  really.
Title: Re: Tufnel gear
Post by: benet on 03.09. 2012 09:23
Hi Guys (by the way, are there any women on this forum?) Just to give you all an update on what happened to my binding gear. I took the advice to loosen the mag fixing bolts and then wedged it a little away from the binding gear. This made a significant improvement and the advance mechanism is now also operating freely. I was told by an engineering friend of mine that by soaking the gear in oil for 24 hrs, which i did,that the tufnel was slightly absorbant and might swell. Anyway thanks all for your help. Ben 
Title: Re: Tufnel gear
Post by: bsa-bill on 03.09. 2012 10:03
Quote
(by the way, are there any women on this forum?)

There was one once, If I recall she was after something for her Dad or something.

No offense guys but after the photo of that curry I think a lady might bring a bit of culinary realism  *fight*
Title: Re: Tufnel gear
Post by: Topdad on 04.09. 2012 13:26
Bill , ye of little faith in our breathren ,you should know you don't eat with your eye's ,it might have looked completely vile ( sorry Richard but true ) but if it tasted ok thats all that matters! particularly when partaking of large amounts of beer to keep it down!! slightly closer to post , my uncle ran the Tufnell office in Manchester from 1946  and if I recall correctly they made the winding gears for the NCB ,it was stronger than steel but they also needed something in the anti spark department and then diversified into electrical insulators etc BobH
Title: Re: Tufnel gear
Post by: bsa-bill on 04.09. 2012 15:04
interesting stuff Bob
and I'll close my eyes when next in our local curry house although that could be a long time off unless their portions have increased substantially (and I'm not a big eater)

PS spotted a spelling mistake just before I went to send, I'd put potions instead of portions - oops
Title: Re: Tufnel gear
Post by: RichardL on 04.09. 2012 19:20
Just listening.