The fog is dissipating-Continuation of Timing Gears

[Allan.Atherton]

The timing gear mark on the case is not necessarily what fits today because the case changes dimensionally over decades of use.

Timing Gear Rumors Dispelled:
Craig Vechorik, Bench Mark Works, on /2 List 1/1/01
1. I took up this subject of gears, and sizes versus numbers on the gears, with the people that MAKE the gears in Europe. Turns out I was wrong also... It seems that gears are not precisely sized, with corresponding numbers, as I had thought. The numbers denote deviation from design standard, and the crank and cam gear are matched to EACH OTHER. This may account for the fact that the two of the same numbered used gears that I have measured have been different in diameter. I thought it was my poor measurement techniques or wear, but this is what I was told...
2. The tolerance markings on the gears having absolutely nothing to do with the individual size of the gears. The "0" dimension between centers of cam shaft and crank shaft is exactly 90mm. The tolerances are measured in hundredths of a mm. That is "-10" is 1 tenth of a millimeter smaller, " +4" is 4 hundredths of a millimeter larger.
3. The different size wheels cannot be purposely produced, even by modern day methods. They are all from the same production, and measured according to out of tolerance by measuring the distance between the flank of 6 teeth at a 90 degree angle. This can only be carried out electronically. The gears are sorted according to deviation from the "0" or exactly 38,495mm.
4. The steel crankshaft gears have a far lower deviation than the Aluminum
gears for the cam shaft.
5. The gear sets (one crank gear and one cam gear) are matched to each other according to end deviation e.g. "-7", and not according to deviation of the individual gears by them selves as this would just not be possible. This is where the misconception of sizes comes from, and it is the most difficult for people to understand. That means that a +6 cam shaft gear on one engine could possibly be used as a "-2" or a "+4" on another engine. You must forget about viewing a size on one gear wheel, but always look on the set as a whole. The case is marked with the deviation number of the gears that were installed in it when new. The number on the gear is not a quantitative measurement of the gear size. Imagine an extreme case of two motors with a "-7" housing. The one has a larger aluminum gear and a smaller steel gear, the other has a smaller aluminum gear but a larger steel gear. The overall deviance from specs of BOTH of the engines is "-7".
6. Also, in regards to cases and the contraction with age: The case grows and get bigger when warm. This is normal for all aluminum alloys. As they get hot, they expand. As they cool, the contract. This cycle carries on thousands of times over the motors life span. Over time, this constant expansion and contraction results in material fatigue and the alloy eventually loses its "memory" and will no longer contract to the dimension it once was when first cast.

Timing Gear Marks vs Measurements
Brian Caro, /2 List, Msg 37940, 24 Mar 05
Based on Vech's analysis of the numbering system, here is the average c-to-c of cam and crank (one must measure the full range of movement within the bearing play):
89.90mm 3.5393" -10
89.91mm 3.5397" -9
89.92mm 3.5401" -8
89.93mm 3.5405" -7
89.94mm 3.5409" -6
89.95mm 3.5413" -5
89.96mm 3.5417" -4
89.97mm 3.5421" -3
89.98mm 3.5425" -2
89.99mm 3.5429" -1
90.00mm 3.5433" 0
90.01mm 3.5437" +1
90.02mm 3.5441" +2
90.03mm 3.5445" +3
90.04mm 3.5449" +4
90.05mm 3.5452" +5
90.06mm 3.5457" +6
90.07mm 3.5461" +7
90.08mm 3.5465" +8
90.09mm 3.5469" +9
90.10mm 3.5472" +10

[schrader7032]

Allan -

So, I've been following this and wondered a few things. How does one order new timing gears for a /2? Do you make precise measurements center-to-center cam-to-crankshaft and provide that to a dealer, etc., and let them provide you with two matching gears?

What if you only decide you need one of the gears replaced? Do have to do the center-to-center measurements and then send the one good gear back in and let the dealer or whoever figure out what would go with that gear?

Obviously, if you were a mechanic, like Vech, and had the resources, you could make some basic measurements and try different sets of gears together until you found a good match. The average person doesn't have those resources.

Thanks...Kurt

[Bruce Frey]

I'm a bit out of my element here....I do not have a 51/3 or a /2. I know only what I see in the parts books on John's Beemergarage site and a bit of the collective wisdom that I have absorbed over time from several vintage forums.

In any case, I am confused about the situation.

Micha....did you use the cam/crank gearset (16-25x) from the same engine and the oil pump drive gear (52-154) from a different engine?

or

did you also mix the cam gear and crank gear from different engines?

It sounds like the oil pump drive gear (52-154) is distorted. Are the cam and crank gears distored or binding?

Which gear has missing teeth?

Bruce

[Allan.Atherton]

... How does one order new timing gears for a /2? Do you make precise measurements center-to-center cam-to-crankshaft and provide that to a dealer, etc., and let them provide you with two matching gears? What if you only decide you need one of the gears replaced? Do have to do the center-to-center measurements and then send the one good gear back in and let the dealer or whoever figure out what would go with that gear?
Obviously, if you were a mechanic, like Vech, and had the resources, you could make some basic measurements and try different sets of gears together until you found a good match...
I read Vech's article as saying you can't order gears by measuring. And I don't know how Caro came up with his figures, or what to do with them. I don't think there is any way of ordering the "right" gears for an old motor.

My impression is that old mechanics like Guenther and Vech take a best guess at what is needed, either a used single gear or a new set of gears. If too loose, the engine will be a little noisy - like the R60/2 I got from CA. If a little too tight on a few teeth, the contact points on the teeth can be filed. If generally too tight, they don't keep the gear(s). Seems to be a matter of feel, though I guess a tolerance measurement must be possible somewhere. I watched Guenther rotate a motor he had just put the gears on, and there was a little bit of free play to feel that he was pleased with. Also saw him mark some contact points on a set of gears that had no play at one point, and file the contact marks. I would not want to file the teeth and miss those marks.

My R60/2 evidently was rebuilt by the PO with odd loose gears with too much free play, because a friend's R60/2 with original gears was quieter. My bike was not noticeable until compared to the other bike, which was essentially silent. Still, a little too loose is harmless, while a little too tight is fatal.

I am not a mechanic and have not rebuilt an engine. Just watched, listened and read.

[Bruce Frey]

I read Vech's article as saying you can't order gears by measuring. And I don't know how Caro came up with his figures, or what to do with them. I don't think there is any way of ordering the "right" gears for an old motor.

I read it a bit differently. Brian's numbers are simply Vech's 0 = 90.00mm for the center to center shaft distance and 0.01mm increments from there.

It seems that it is the overall "sum" of the cam/crank gears that make up the number. You could have 2 gearsets with the same overall number, but they would probably not have identical gear sizes. (i.e, 1+6=7, 2+5=7, 3+4=7, etc)

The trick, of course, is being able to measure accurately. I think you can ORDER gears based on your individual measurement.

Since it IS impossible for mortals to measure individual gears and make up a set, the way Guenther and Vech do it is to fit gears on a trial and error basis from their vast collections of spares until they get a match.

My take is that if you are rebuilding an engine, fitting a correct gearset can be done by either by trial and error or by measuring and ordering a new set to match the measurement.

If you are replacing one gear, the only way is by trial and error.

Bruce

[VBMWMO]

Dear all,
Further to my problem, I have just found out that the oil gear is OK (more or less… It still has 2 teeth missing and a few rough ones) and the problem is the drive gear of the aluminium oil pump gear (11 41 0 052 164). It is twisted and so the alu gear runs back and forward. Well, I think that's good news, although replacing it while engine in frame will not be easy. It is also possible to get the alu gear at Huggett, part number 11 41 0 052 154. The thing is that they are expensive, about 200$. Will it be OK to fit the old one back? The bike did run it OK before those slingers changing. Another one: Are there a few types of those alu gears? I mean are they also a part of those timing gears set? Or can they be bought separately? The tolerance on the case is stamped as 2-
Thank you.
Michael.