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Frantisek Jiracek 4 speed transmission

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Post Tue Apr 04, 2017 10:06 am
GuS

Posts: 408
Location: Bergen, Norway
Anyone have knowledge with the Frantisek Jiracek 4 speed conversion? Im struggling to find rollers for the clutch gear bearing. He used a metric clutch gear, 37.00mm. Available rollers are to small. One option is to open up the race and find 3.5mm metric roller.
As i undrestood he did not sell kits, but did the entire rebuild. I dropped by him some 12 years back and have him sell me a kit. Now Im trying to assemble and struggle with the clutch gear rollers.
I heard Jiracek passed away, and I dont know where to ask how he solved it. Anyone who have assembled or have opened up one of his transmissions?

GuS

Post Tue Apr 11, 2017 11:17 pm
GuS

Posts: 408
Location: Bergen, Norway
Found a 3.5mm metric roller, and resizing the race. Tanks Ralph and Pa for tips regardig removal of the race.
Now another headache was my flimsy toolpost grinder, or rather the flimsy dremel extender that goes into my toopost fixture. Done valves etc, but for this job vibrated to much. Caninalzed a broken dremed, it doesnt vibrate that easy, but i have to make really small cuts to avoid vibration. Like watching paint dry...
I know I was running a risk grinding through the hardening, but done 1/10 mm so far, and seem ok.

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GuS

Post Wed Apr 12, 2017 12:34 pm
Pa Site Admin

Posts: 6037
Location: Ohio USA

It is a tedious task when one does not own an industrial grinder. Even with an industrial one, one must take very light passes.

GuS

Posts: 408
Location: Bergen, Norway
Pa, Yes, but what i dont like is when it starts wobbling the surface gets damage and i loose control of the dimmension. Dont want that to happen close to the final pass. I might make a 3 version using my air grinder....

What surprises me in a positive sense is the race doesnt seem to loose the hardening with depth. Do you have any idea if these bearings are hardened through?

GuS

Pa Site Admin

Posts: 6037
Location: Ohio USA

I do believe they are hardened clear through Gus, just like the clutch sprocket and race are.

GuS

Posts: 408
Location: Bergen, Norway
Must clean some of the parts for rust. Best way I find is to use electrolysis.
3 tbls baking soda pr gal water. 12 v battery charger. Minus to rusted part. Plus to anode, stainless plate to avoid anode being eaten away.

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Let it sit a couple of days. Some scrubbing with a brush and rinse.

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GuS

GuS

Posts: 408
Location: Bergen, Norway
Pa, thanks for your reply. Here is another puzzle. Race reground to given spec clearance with new metric 3.5mm rollers. The length is 0.003" longer than original rollers.
Expected to maybe have to reduce thicknes of the trust washer, 2520-41. But no! The race width minus the trust washer thicknes give 0.015" clearance from roller to race edge, assuming the edge of trust bearing race, 2522-41 ends at the race edge.

Here comes the problem. From end of race to trust bearing race I measured approx 0.07" clearance. Meaning the roller would be having a free end play of 0.07+0.015=0.0715", and even worse the roller could wander hanging 0.07" on the inside of the race.

I noticed when taking the transmission apart, the trust washer, 2520-41 was installed on the wrong side towards the trust bearing race, 2522-41, and not towards the retaining washer 2520-41A. This may make sense as the person assembling this transmission once must have realised this problem. I even dug out a trust bearing/and race from other rebuilds Ive done to compare and see if the trust bearing race lip was smaller on this one, but they are the same. The only explanation I can think of is that the groove for trust bearing in the clutch gear race is to shallow.
Or should the rollers have this big end play? It does not make sense to allow the roller outside its race.

I have cut a second trust washer # 2520-41 from an old flyweel trust washer, to have on both sides of the rollers. That should keep the rollers within the race and give roller end play of 0.012".

Another interesting point is there must be an error in the 1950 45" spare part catalog. The retaining washer 2520-41A has switched place with 2520-41 on illustration on page 38.

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GuS

Post Sat Apr 15, 2017 12:27 pm
Pa Site Admin

Posts: 6037
Location: Ohio USA

Bottom illustration is in correct order. I am still trying to understand why the draftsman drew up the top illustration the way he did so. I see a problem around the corner using rollers which are to long. Those rollers in combination with the thrust washer, the 2521-41 bearing, and the 2522-41, will shift the position of the clutch gear. Shifting the clutch gear position will add additional problems when adjusting mainshaft endplay, the second gear retaining bracket, and al the mainshaft gears and shifting clutches. The cluster gear on the countershaft will also suffer.

GuS

Posts: 408
Location: Bergen, Norway
Pa, the drafsman has swapped the -A, most likely done on a monday morning. :)
I'm not good at explaining. It is not the roller that are to long. Yes longer than the original, but that is only by 0.003". The roller is still inside its race. Problem is the bearing race for the trust bearing. Item 2522-41. The lip of this race is the thrust for the clutch gear roller. Problem is that this race is too far away from the roller hence not preventing the roller to wander inwards by as much as 0.0715".
The position of the trust bearing race lip is defined by size of the trust bearing balls, and the dept of the grooves for the trust bearing balls. Both trust bearing balls and race are checked with original ones.

But ulimately you are right if he trust bearing race is shifting the position of the clutch gear, this will affect position of the gear sprockets, and may affect alignment with the clustrr gear.

I plan to install the clutch gear bushing tomorrow so i can install mainshaft and shims to get a better picture how the rest will align up.

GuS


Posts: 76
Gus,
I'm not sure what you're working with but when using OEM parts the rollers can not hang over the race.
The lip on the thrust bearing race 2522-41 is not flush with the edge of the race when installed.
Haven't measured but I'm sure it protrudes into the case race .010-.015".
The thrust washer 2522-41 also fits inside the case race on the other end of the rollers, keeping the rollers inside the case race on both ends.
If the parts you are working with are the same size as original parts, your rollers that are only .003" longer should work fine.

GuS

Posts: 408
Location: Bergen, Norway
ralph. Thanks for your answer
In my case, the lip does not protrude into the race, but stays 0.07" away from the race.
The trust bearing race, and trust bearing came with an assambled early 41 case. I also have these parts from earler to compare with, and they are the same size and shape. The clutch bearing race was in another case, it still got remains of the green paint. I cannot guarantee these are OEM, but to my knowledge they are.
I will have to stack up all gears and shims on the mainshaft and see how this align.
GuS


Posts: 76
GuS,
I don't know what else it could be other than the thrust balls 2521-41.
Make sure the thrust balls you are using have 19 ball bearings, not 16 like the pre-'41 used.

GuS

Posts: 408
Location: Bergen, Norway
This transmission gave me some challenges. Progress is a bit slower since only one of the gearbushing had good interference fit in gear. One bushing and the clutch gear bushing had to be re-cut, and one bushing had to be made new. Seems like Mr. Frantisek liked to keep his own dimmensions.
But I have good hope for the final product, as the reports are his transmissions are bullet proof. And I may be able to do something with overall gearing.
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The trust race and bearing is the 41 and later version. The one to the right you can see trace of the needle trust on the lip. The left one came out of the one I'm working on. No trace of roller trust, since the trust washer, 2520-41 was installed towards the trust race lip.
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Clutch gear race installed after resizing. I have no OEM part to compare with, but seems right to me.
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Holding the trust bearing and race in position. Mini screwdriver pointing to the gap.
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GuS

Post Sun Apr 16, 2017 11:43 am
Pa Site Admin

Posts: 6037
Location: Ohio USA

Gus.....I just found these drawings in my files which I had forgotten I took from an original NOS clutch bearing race which was sealed in military packaging. If you know all the dimensions of the race you installed, these may help you. All measurements and dimensions show on the drawings are in inches.

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GuS

Posts: 408
Location: Bergen, Norway
Pa.
Thanks a lot.
I will mic up mine to compare with your drawing.
I have sent you a PM.

GuS


Posts: 76
GuS,
Just noticed in your photo that you haven't rotated your tripper bolts yet.
You may not have got to that point yet, but just in case I wanted to remind you.
If you don't rotate them to a fresh retracting surface you'll have trouble with your starter clutch.
Rotate 1/3 instead of 1/2 and you can get two more uses out of them instead of one.
NOS ones are not easy to find and the aftermarket ones I've seen are not hard enough and don't have correct retracting angle.


Posts: 76
GuS,
Also, I noticed in your post that you hoped to make some changes in your overall gearing.
This transmission only lowers the RPM loss between shifts, you're still 1:1 in high gear.

GuS

Posts: 408
Location: Bergen, Norway
ralph.
Thanks for the tip on the 1/3 rotation of the tripper bolts. That is correctly observed. I hadnt rotated them and hadnt planned to as the look really nice.
To the overall gearing, you are right. I wont get no OD. :D One could wish.
Plan is to gear her up on final drive and make use of the additional gear for less drop in rpm on shifting.
I havent decided on final ratio yet.
GuS

Pa Site Admin

Posts: 6037
Location: Ohio USA

GuS...I replied to your PM.

GuS

Posts: 408
Location: Bergen, Norway
Thanks Pa for the drawing.
I have the measurements, will make a sketch.

Had to cut trust washers for the 1st gear.
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.. and cut the sprocket cover to make room for the 1st gear.
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Local beer can comes in handy.
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GuS

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