Gear for ATD - Material and Dealer?

stumpy lord

Well Known and Active Forum User
Non-VOC Member
Sebastian, your English beats my High school German by a long way! I assume that when you are talking about + or _ .002" you are referring to ET49, the half-time pinion on the crankshaft. ET 48 was never issued in sizes and always has backlash, presumably to avoid stress on the magneto bearings. There have been some astonishingly good technical articles written about half-time pinion sizes if you want to spend a few long winter nights going insane. What I generally do is get two new 1/8" drill bits and a micrometer to do a comparison on sizes by measuring across two opposite tooth spaces. I never trust what is marked on the pinions. If there was a way to give 4 to 36 degrees advance it might be better if your "Benzin" is as bad as the stuff in Australia. Good Luck and keep at it! Cheers, F5AB/2A/7945 since 1970

HI,
appart from ET49 the half time pinnion having five key ways cut in it, and the face markings ,ET 49 andET 48 are the same. THere fore their is no reason why an oversize half time pinion should not be used as the breather pinion, eliminating that infuriating backlash that always seem to be there between the A.T.D. pinion and the breather pinion.
Thats what we did on Rogers Twin, and what I will do on mine the next time the timing case cover is off.

cheers stumpy lord.
 

Sebastian Huber

Well Known and Active Forum User
VOC Member
Hello David,

thanks for info.
Have odered pinion at Russell Kemp. Expect to get it at the beginning of next week. Have asked for material but can`t remember at the moment. What I´m keen on is diameter, but as chankly bore answered this wasn`t ever modified. Hope the one who made it for Kemp knows requirements.
Shurely there are only a few guys who make pinions for the dealers. This way I go to know one who makes pinions out of Calaumid, (it is PA 6/12). Even I´ve no exoperience about this material in this application (oil and heat could be a little bit tricky) I feel it for the best solution.
After last bad experiences I made a solem vow to use this Forum for advices by Vincent Experts for beeing impossible to have all this detailed knowlegment by beeing Vincent Rider for only two years. It should be a simple jobs to renew this pinion, isn`t it? But after 40 years with oily fingers nothing drives me more crazy as to make stupid failures.


Regards
Sebastian
 

chankly bore

Well Known and Active Forum User
Non-VOC Member
Sebastian, be very careful about water absorption and heat-resitant properties of Calaumid. Some years ago the club chose an unsuitable material which enlarged in service and did very extensive damage! As Dave Dunphy says, Tufnol is the best unless you can be sure of the replacement material. ET 49 is half the diameter of ET 48, by the way. Cheers! I am sure Kemp parts would be o.k. as they test their stuff on their own 'bikes.
 

Sebastian Huber

Well Known and Active Forum User
VOC Member
Hi chankly bore,

thanks for compliments for my 3rd Class English, but here - with e-dictonary in the background - you can`t see the real disaster.

You`re right with ET49. I mixed ET48 with ET49 Halftime pinion because I`m usually on homepage of VOC Spares during lunch break in office as I do actually, but everytime it becomes short!

Yes, tooth profiles are difficult enough in Modul Pitch but Diametral Pitch is extremly strange for Continentals.
We have here in Germany only a few good adresses where you get this work done on Diametral Pitch.

Certainly our fuel here is the same waste as anywhere else in the so called civilized world. Pick it up and burn it immediately! Ohterwise the aerially goodies are gone and there is no more than 85 to 90 octan in it.

For to reduce advance range I had to add a plate or little screw with certain tickness on block area what I feel is difficult an dangerous too, to have any impurity in timing chamber. Think it`s better to keep out of maximum rpms for to ensure fun of this bike in next gereration too.

Keep Well,
Regards
Sebastian
 

clevtrev

Well Known and Active Forum User
VOC Member
Sebastian, be very careful about water absorption and heat-resitant properties of Calaumid. Some years ago the club chose an unsuitable material which enlarged in service and did very extensive damage! As Dave Dunphy says, Tufnol is the best unless you can be sure of the replacement material. ET 49 is half the diameter of ET 48, by the way. Cheers! I am sure Kemp parts would be o.k. as they test their stuff on their own 'bikes.
Ah, Tufnol, the name of a producer. They even make Thermoplastics. So you need to be a bit more specific in what you say.
As for Stumpy, the backlash is there for a reason, ignore that at your peril.
 

timetraveller

Well Known and Active Forum User
VOC Member
Well for one thing, 'Tufnol', that is the impregnated linen that we were all brought up to call 'Tufnol' , has a very high rate of thermal expasion. Give it zero backlash when cold and you will be in trouble when it is hot. Clevtrev might have additional reasons.
 

Jim Richardson

Well Known and Active Forum User
VOC Member
I was looking for the source of a rattle at the weekend and dealing with a leak from the ATD cover, I was surprised by the amount of noise generated just by moving the distrbuter gear by hand.
Wouldnt it have been better to put the Tufnol gear between the cam and the Mag/Distributer.

JimR
 

Sebastian Huber

Well Known and Active Forum User
VOC Member
Hi chankly bore,

thanks for advice. Yes, I´ve seen on technical details for Calaumid that it absobe 5,8% water what is normal for PA and certainly my cause problems when it is fixed by pressing on stell hub for getting bigger and won`t stick any more.
Actually I´m still waiting for those of Kemp.

Keep well,
Sebastian
 
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