Cleaning up boring job

Cleaning up boring job

Irregular Logic
Irregular Logic

January 19th, 2012, 8:03 am #1

Over at the Strictly Hodaka forum, they were discussing ways to improve the transmission; specifically, it's shifting mechanism.

The transmission is very compact, but it has the problem with the springs on the shifter rod that fatigue, unwind and cause problems with shifting and gear engagement. One guy, while doing measurements between the two styles of transmissions that were used on these bikes, posted these pictures of the inside of the countershaft.


Part 6 is the countershaft.


This shaft is from a Model 94 Wombat, circa 1972. It looks pretty ugly in there.

in the later years, Hodaka did do a little bit cleaner job inside the countershafts, as witnessed by this shaft from a Model 03 Wombat, circa 1976.


The shifter ball (Part 20) is the only part that may have contact with this shaft surface, but there was some thought on what might be done to clean these surfaces up. I don't know what the hardness of the metal is, or if it goes through all the way. I thought a slow, light pass with a sharp boring bar might be enough, but i'm still wondering if there is another way to avoid removing too much metal.

Any thoughts?

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Shargo
Shargo

January 19th, 2012, 8:26 am #2

If not, don't fix it if it ain't broken...

(My guess is that the shaft is hardened in some way and that will make for difficult machining)
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Irregular Logic
Irregular Logic

January 19th, 2012, 10:06 am #3

The ball reciever does get "dented" from the gear balls, but the problems with shifting is more from the springs unwinding when pushed into and out of gear. Hodaka riders are constantly told to "Snick their shifts" when riding to stretch the life of the springs.

This is a better picture of the shifter ball used in the transmissions:



Newer transmissions did use a different ball with flutes added to help guide the balls onto the incline. I think that is partially why the countershaft ID for the 03 is a slightly larger diameter.



I don't think the ball actually touches the ID of the countershaft, but I am sort of scratching my head on how you would polish the inside surface of a hole.
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Lakc
Lakc

January 19th, 2012, 11:12 am #4

Over at the Strictly Hodaka forum, they were discussing ways to improve the transmission; specifically, it's shifting mechanism.

The transmission is very compact, but it has the problem with the springs on the shifter rod that fatigue, unwind and cause problems with shifting and gear engagement. One guy, while doing measurements between the two styles of transmissions that were used on these bikes, posted these pictures of the inside of the countershaft.


Part 6 is the countershaft.


This shaft is from a Model 94 Wombat, circa 1972. It looks pretty ugly in there.

in the later years, Hodaka did do a little bit cleaner job inside the countershafts, as witnessed by this shaft from a Model 03 Wombat, circa 1976.


The shifter ball (Part 20) is the only part that may have contact with this shaft surface, but there was some thought on what might be done to clean these surfaces up. I don't know what the hardness of the metal is, or if it goes through all the way. I thought a slow, light pass with a sharp boring bar might be enough, but i'm still wondering if there is another way to avoid removing too much metal.

Any thoughts?
I think I have an idea of what your saying is happening. The surface finish of the bore can be lapped but I dont think thats going to help much. The shifter ball as you call it looks like it really needs to be keyed to prevent its rotation and unwinding the springs.
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Doc Nickel
Doc Nickel

January 19th, 2012, 12:57 pm #5

Over at the Strictly Hodaka forum, they were discussing ways to improve the transmission; specifically, it's shifting mechanism.

The transmission is very compact, but it has the problem with the springs on the shifter rod that fatigue, unwind and cause problems with shifting and gear engagement. One guy, while doing measurements between the two styles of transmissions that were used on these bikes, posted these pictures of the inside of the countershaft.


Part 6 is the countershaft.


This shaft is from a Model 94 Wombat, circa 1972. It looks pretty ugly in there.

in the later years, Hodaka did do a little bit cleaner job inside the countershafts, as witnessed by this shaft from a Model 03 Wombat, circa 1976.


The shifter ball (Part 20) is the only part that may have contact with this shaft surface, but there was some thought on what might be done to clean these surfaces up. I don't know what the hardness of the metal is, or if it goes through all the way. I thought a slow, light pass with a sharp boring bar might be enough, but i'm still wondering if there is another way to avoid removing too much metal.

Any thoughts?
First off, you need to determine what action part 20 makes while in operation.

If I understand it properly, part 20 acts as kind of a collar, that slides left and right on it's shaft (part 16.) And at each of the five positions, I'm presuming, expands the four balls (part 7) outward slightly to lock that particular spur gear (parts 8 through 12) to the output shaft (part 6.)

I would suspect that the collar (20) actually has little or no in-use contact with the bore of the countershaft- and even if it did, it appears everything rotates with the countershaft, meaning the only wear is left-right scrubbing, not rotary.

You can do a quick check yourself- mic part 20 (and probably 21) and see what the OD is. If it's more than, say, .005 to .010 less than the ID of the output shaft, there's essentially no contact, and any wear, therefore, would be as it engages and disengages the balls.

Which means, of course, that anything you do to the bore would be wasted effort.

I suspect this is what you'll find, since even a company like Hodaka, back in the seventies, could and would have finished the bore to better tolerances or finishes, if it was necessary to provide a smooth sliding fit.

Now, if it turns out you do, in fact, need to finish the bore better, and the actual ID spec can tolerate a little metal removal, this will likely be a grinding job.

The output shaft not only has to hold the countershaft sprocket- IE, the gear what drives the whole bike forward- but it also carries the transmission spur gears, which, at any given time, four of which are idling- spinning on the shaft without driving anything.

That means the shaft is very likely good and hard- more tough than glass hard, but hard enough you'd need a rigid boring bar and a good carbide insert to cut it.

The proper tool, depending on the depth of the bore to be finished, and especially considering it's more for cleanup than to drastically change the bore would be to grind it, using an extended nose toolpost grinder.

It's probably, however, not necessary. Sounds more like the proper fix would be to source better quality springs, and possibly replace those "cups" on the ends with hardened and ground pieces, rather than stamped cups. That would make it more difficult for the springs to get a "bite" on anything, and be unwound by the rotation of the shafting.

Doc.
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Curt
Curt

January 19th, 2012, 3:58 pm #6

Over at the Strictly Hodaka forum, they were discussing ways to improve the transmission; specifically, it's shifting mechanism.

The transmission is very compact, but it has the problem with the springs on the shifter rod that fatigue, unwind and cause problems with shifting and gear engagement. One guy, while doing measurements between the two styles of transmissions that were used on these bikes, posted these pictures of the inside of the countershaft.


Part 6 is the countershaft.


This shaft is from a Model 94 Wombat, circa 1972. It looks pretty ugly in there.

in the later years, Hodaka did do a little bit cleaner job inside the countershafts, as witnessed by this shaft from a Model 03 Wombat, circa 1976.


The shifter ball (Part 20) is the only part that may have contact with this shaft surface, but there was some thought on what might be done to clean these surfaces up. I don't know what the hardness of the metal is, or if it goes through all the way. I thought a slow, light pass with a sharp boring bar might be enough, but i'm still wondering if there is another way to avoid removing too much metal.

Any thoughts?
looks like part 18 and 19 are the springs in question? It looks like when you push it into gear they may be catching on the shifter rod and unwinding/rewinding with a torsional load in addition to the compressive load they are meant to relieve.

Might an additional washer assembly, say two very thin stainless sandwiching Teflon at either end of the spring relieve that? Or even a roller-bearing assembly if there is room, or the shaft flange can be expanded while maintaining shift tolerances.

-Curt
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Russ Kepler
Russ Kepler

January 19th, 2012, 5:35 pm #7

The ball reciever does get "dented" from the gear balls, but the problems with shifting is more from the springs unwinding when pushed into and out of gear. Hodaka riders are constantly told to "Snick their shifts" when riding to stretch the life of the springs.

This is a better picture of the shifter ball used in the transmissions:



Newer transmissions did use a different ball with flutes added to help guide the balls onto the incline. I think that is partially why the countershaft ID for the 03 is a slightly larger diameter.



I don't think the ball actually touches the ID of the countershaft, but I am sort of scratching my head on how you would polish the inside surface of a hole.
Something like that I'd polish with a flexhone or something similar, it's kind of depends on the material and how many you're doing. Do a couple, hone it, do a lot, ballsize or something similar.

Be careful. Honing will remove material and if it's as rough as it appears you might have to take off a lot to get it smooth. Might want to just take out the roughness first and see if there's any improvement.
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Hans
Hans

January 19th, 2012, 6:20 pm #8

looks like part 18 and 19 are the springs in question? It looks like when you push it into gear they may be catching on the shifter rod and unwinding/rewinding with a torsional load in addition to the compressive load they are meant to relieve.

Might an additional washer assembly, say two very thin stainless sandwiching Teflon at either end of the spring relieve that? Or even a roller-bearing assembly if there is room, or the shaft flange can be expanded while maintaining shift tolerances.

-Curt
A telescopic type cup sleeve maybe, to enclose the springs more completely? Looks like enough room in there.

Or possibly variable rate springs to control the amount / location of the unwinding?

-Hans
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Ze
Ze

January 20th, 2012, 5:44 am #9

What about a stack of Belleville Spring Washers? that way the rotation wouldn't matter.

Cheers,
Ze
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Maker Of Toys
Maker Of Toys

January 20th, 2012, 10:04 am #10

Over at the Strictly Hodaka forum, they were discussing ways to improve the transmission; specifically, it's shifting mechanism.

The transmission is very compact, but it has the problem with the springs on the shifter rod that fatigue, unwind and cause problems with shifting and gear engagement. One guy, while doing measurements between the two styles of transmissions that were used on these bikes, posted these pictures of the inside of the countershaft.


Part 6 is the countershaft.


This shaft is from a Model 94 Wombat, circa 1972. It looks pretty ugly in there.

in the later years, Hodaka did do a little bit cleaner job inside the countershafts, as witnessed by this shaft from a Model 03 Wombat, circa 1976.


The shifter ball (Part 20) is the only part that may have contact with this shaft surface, but there was some thought on what might be done to clean these surfaces up. I don't know what the hardness of the metal is, or if it goes through all the way. I thought a slow, light pass with a sharp boring bar might be enough, but i'm still wondering if there is another way to avoid removing too much metal.

Any thoughts?
. . . I'd say that the inside bore roughness is the wrong tree to bark up. Even assuming the selector ball is in substantial contact with the bore, it's going to be pretty much keyed to the outer shaft by virtue of its detent function, so no real relative motion there. . . and the springs are much smaller in diameter, and would have a hard time getting far enough out-of-concentricity on shaft 16 to touch the bore on their own without some significant outside force.

I assume that gear selection is accomplished by axial manipulation of shaft/pin #16, in turn inducing force through springs 18 and 19 to move selector 20? If so, dragging one's shifter-foot on the shift lever is going to be the root cause of the meyhem, by introducing drag on the rotation of 16 (and therefore relative rotation between 16 and 6. see below for the rest of the story) Get your lead-lined boot off the shifter, and hey-presto, no problem.

the next easiest solution? I'm guessing the 'unwound spring' problem comes most often to people who fail to keep a sufficient quantity of fresh, cool oil in the gearbox. Those parts are in the center of a shaft that turns fairly fast, with lots of opportunity for what oil manages to get in to be centrifuged right back out. . . leaving some heavily stressed parts with marginal lubrication at best. I would further guess that bikes with 'unwound' springs have also have a history of leakage from seal/o-ring 15, and wear on the external end of 16 (and mating part), indicating excessive relative rotation and force. See above for the solution: train the rider to respect the machinery!

But, humans being humans, better to do as others have said, and try to prevent the ends of the spring from catching on the thrust surfaces. . .

The engineered solution? Assuming the top of your first 'parts' photo to be 'forward' and part #16 to be stationary due to external drag, and therefore dragging on 18 and 19, the ends of those springs are eventually going to gall washers 17, which will lock to the spring, which in turn will gall the surface of 20, until something seizes (or the heat alters the temper of the spring) and the spring fails, screwing up the positioning function of the 16-18-17-20-17-19-21-22 stack. Looking at the handedness of the springs, the final damage is probably done by timid down-shifting and/or resting one's foot on top of the shifter while engine-braking.

As others have said, service life could be extended by doubling up the thrust washers (17) on each side of the detent ball, and/ or find a replacement with a phenolic/ptfe lining on one of the faces. . . . you might even get away with a single washer, appropriately faced, but wear would be rapid on a retrofit having a used detent collar/other parts, at least until the old wear pattern and the facing come to an understanding. A simple nylon shim under the end of the spring might be an improvement-- Anything to keep the sharp end of the spring wire from wearing on that thrust surface. Another thing to try, assuming a shared oil supply between engine and trans, and an oil pump with some extra capacity: spray some oil at the center of the 5th-gear end of shaft #6, in the hopes that it will get to the 17-20-17 interface where trouble begins.

But in any case, heavy-footed riders will kill that transmission sooner or later, just like those who drive with their hand on the shift-stick in a car are going to have to replace shift forks much more often. (figured that one out from bitter personal experience)

TL;DR: The springs/selector assy doesn't drag in the bore until after they've already failed. Look elsewhere for solutions.
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