Tufnel gear

[benet]

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

[bsa-bill]

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.

[Triton Thrasher]

I think I've heard that a Tufnol gear needs backlash.

Try another one from Price, if still in business.

[benet]

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

[a10 gf]

(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"

[Triton Thrasher]

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.

[lawnmowerman]

(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

[RichardL]

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.

[Triton Thrasher]

A fibre gear with hand formed teeth will promptly fail in service, I'd almost bet.

[Goldy]

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.

[RichardL]

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.

[Triton Thrasher]

They don't cost much.

[RichardL]

OK. I was going with the theory that all the new ones might be oversized; but,  no clue,  really.

[benet]

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 

[bsa-bill]

(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