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#427102 - 03/31/12 12:41 am T140 5speed gearbox selectors  
Joined: Sep 2011
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Excalibur Online content
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Here are photos of the T140 dragbike gearbox that is giving intermittent issues with changing gear. The gearchange in question is either into 3rd or into 4th. The lever initially locks solid, but changes OK if released, then re-activated. It's difficult to remember which gear it is, as during the race, everything happens rather quickly! It certainly isn't 2nd or top, so that only leaves 3rd or 4th.
You'll notice parts are lightened with a significant amount of material removed. Lightness is a key factor which makes this bike go as well as it does. I think carefully about what and how much material to trim, but I may have created the issue with some of these mods.

The gear lever spindle is hollow. The selector pawl plate has had material peeled off, drilled and chamfered. The outer cover was made from one that was already broken at the flashing.


Here is where the quadrant fits to the inner case. This was the best shot of a difficult to capture issue. Look where the quadrant pin area has been milled. Part of the area around the hole was too low for the mill cutter. Obviously this happened at the factory and could be a result of not enough material allowed for in the mold. This allows more sideways "rock" of the quadrant than would otherwise be desirable.


Here you'll see an extra hole drilled between where the pawls are housed. One pawl has an identifying groove. Their springs have about a millimeter difference in length. The bigger springs were renewed recently. The plate that covers these was pruned and modified. Where the spring ends contact this plate, the tit was built up and squared to give a fuller "rest" for the spring ends.


Here is the crack (circled). Probably it's been there since before the bike was run for the first time. It was hard to spot but upon closer inspection the tooth is slightly bent as a result of impact, is my guess. The pin is made from silver steel and wasn't hardened. It's a closer fit than the original by a thou or 2. The quadrant sure was hardened!!

This gearbox was built from leftovers so mismatching is a distinct possibility.
Questions:
Is there any known issues with mismatched items?
Would it be worth shimming the quadrant endfloat to say .002"?
Is it worth shimming the gear lever spindle endfloat to say .002"?
Is it worth adjusting the layshaft endfloat to say .002"?
Is the camplate worth having a look at for endfloat shimming?
A later camplate is used with more factory removed material from the outer. Are these as good as earlier "full circle type"?
As original, a quadrant is split pinned to its' shaft. Is there any advantage?
Any other tweaks for a sweet changing box?
Thanks.

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#427131 - 03/31/12 4:16 am Re: T140 5speed gearbox selectors [Re: Excalibur]  
Joined: Nov 2008
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desco Online content
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My God I wish I could help you, but you are operating at a level far beyond my comprehension. Congrats on your win. One more trophy for Triumph's.


1968 T120R
1972 T120RV
Any advice given is without a warranty expressed or implied.
#427138 - 03/31/12 5:59 am Re: T140 5speed gearbox selectors [Re: desco]  
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Excalibur Online content
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Excalibur  Online Content
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desco, thanks for the encouragement!

The team is doing everything it can to hold the Triumph flag high! The hope is that with our efforts, Triumph owners/fans will be uplifted and have reason to feel proud of their bikes. We are like family, all helping each other and this forum presents such a great opportunity to do that. I thank all those who made this forum possible and all those that make it what it is today.

We've had a very good run of success these last two seasons. Sadly, the gearbox prevented the possibility of another win on the day, not to mention the prize money. I've a few ideas of what to do, but the forum collective are such a vast wealth of knowledge.... and experience.

#427140 - 03/31/12 7:26 am Re: T140 5speed gearbox selectors [Re: Excalibur]  
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Phatt Bob Offline
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I've never had any trouble with my 5 speed doing clutchless shifts, but here are a couple of brain farts which may help (no doubt I'll be told I'm wrong again but it works for me)

I think the bush in the gears sometimes move, some have a notch cut in the gear and the bush is peened into it to stop it happening.
You said the box was built from parts? The 4 speed and 5 speed pawls are different (one has the edge half way across the diameter and the other about 2/3rds), but I don't think it would change at all if they were wrong.
I've shimmed my positive stop up so it slighty under selects. Momentum carries the plunger into the v notch. I assembled the camplate and selector mechanism and dropped a bulb thru the sleeve gear bearing to see what was happening. The shims are pieces of angle held under the pawl plate which has to relieved a bit to take them. There's a good photo of some in the Shenton book, showing the 5 speed Quaife which uses the same principle.
I did once have a problem with over shifting, but that was cured by deepening the index plunger notch by a mm.
When third jams, is it actually because you're still trying to force second in as the lever and pawls haven't restored to centre?

Just some thoughts...

Cheers

Bob


Phatt Bob
'95 Daytona 1200
'98 Daytona 1200 dragbike
ex-850 T140 Caff Racer, 850 Triton, Morgo T120, Starfire and Pretend Daytona 500 owner
#427196 - 03/31/12 5:28 pm Re: T140 5speed gearbox selectors [Re: Excalibur]  
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For all your efforts in lightening you seem to have left a lot of material in the outer cover. You do not need the re-enforcement around the non-existent kickstart spindle. The screw bosses for the shift driver spring plate can be cut away from the bottom of the screws to the outer cover.
The pin area in the case started out too low or was worn/deformed by the quadrant? The split pin is so the bearing area is the full width of the pin in the case and not just the quadrant wearing on the pin. The driver dogs work in an arc so they push the quadrant sideways as the lever moves.
The crack is between the 1st and 2nd drive blocks of the quadrant?
I do not believe that shimming the kickstart spindle would make much difference. The drive pins are spring loaded against the quadrant so it is always being pushed against the outer cover. I have put needle bearings in the case to reduce the friction. Kasenit can be used to add case hardening to the surface. The shift shaft is rather soft and roughly machined.
The camplate should be as close to the shift forks as possible. It pushes on the fork pins which tries to rock the fork on the shaft. Have you checked the squareness of the forks to the shaft?
The pointed camplate stop plunger creates a lot of drag and usually wears a groove in the edge of the plate. A plunger with a straight tip (like a line contact rocker) would decrease the drag. It needs "ears" to capture the camplate so it remains square to the edge.

#427201 - 03/31/12 6:20 pm Re: T140 5speed gearbox selectors [Re: DMadigan]  
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Excalibur Online content
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DMadigan
Thanks for the good points made.


Crack position. Faint I know, but I missed it from the start! That tooth is bent from impact.

Quote:
For all your efforts in lightening you seem to have left a lot of material in the outer cover. You do not need the re-enforcement around the non-existent kickstart spindle. The screw bosses for the shift driver spring plate can be cut away from the bottom of the screws to the outer cover.

I thought about this quite a lot when I first modified it. Then a friend turned up and suggested that the cover itself didn't need to be the thickness it was either. The thickness remained the same, being that it was in the too hard basket for the time being. What's not visible is the old kickstart boss is drilled like Swiss cheese. I elected to retain the bossing because it has engine mount bolts nearby. For sure, more can be done here. The plate screw holes to outer cover webs only need keep captive the springs, but again more can be done. The cover itself feels like a heavy lump when compared to any bike modern covers. Any work done cutting away aluminum seems like little reward but I can't think like that. I need every "edge".
In review of this, I weighed the cover. 760grams (1.68lb) I think now, the kickstart boss can be removed completely. Also the boss in behind the inner cover can be slimmed down as well. 760grams is a lot more than this cover needs to be.

Quote:
The pin area in the case started out too low or was worn/deformed by the quadrant? The split pin is so the bearing area is the full width of the pin in the case and not just the quadrant wearing on the pin. The driver dogs work in an arc so they push the quadrant sideways as the lever moves.

Yes, the pin area in the case started too low from new. I'm not convinced the pin needs to turn with the quadrant. Perhaps my thinking is wrong, please elaborate. The quadrant getting pushed sideways by the driver dogs working in arc is what I reason is at least one issue. It would possibly account for the "locking solid" of the gearlever.

Quote:
I have put needle bearings in the case to reduce the friction. Kasenit can be used to add case hardening to the surface. The shift shaft is rather soft and roughly machined.

Needle rollers is an interesting mod and the kasenit I've been wanting to get some for a while now. Is the shaft and the bore in the casing a nominal size or was machining necessary? How did you seal the shaft for oil.

Quote:
The camplate should be as close to the shift forks as possible. It pushes on the fork pins which tries to rock the fork on the shaft. Have you checked the squareness of the forks to the shaft?

I once adjusted a pre-unit box with a 5speed cluster for my circuit bike in the manner you describe. If I recall these have a bushing which can be moved to adjust clearance. Logically, the camplate should be close without giving friction interference. Squareness of selectors needs a better inspection, after all I missed the crack in the quadrant.

Quote:
The pointed camplate stop plunger creates a lot of drag and usually wears a groove in the edge of the plate. A plunger with a straight tip (like a line contact rocker) would decrease the drag. It needs "ears" to capture the camplate so it remains square to the edge.

Another interesting observation. My camplate isn't showing any wear from the plunger but it's not to say it can't be improved for drag. Good tip about the plunger needing ears so it can't rotate.

Thanks, it's food for thought!

Last edited by Excalibur; 04/01/12 7:38 am.
#427270 - 04/01/12 2:38 am Re: T140 5speed gearbox selectors [Re: Phatt Bob]  
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Excalibur Online content
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Bob
Thanks for the thoughts.
Yes the clutchless shifts work surprisingly well once the art is mastered. I remember 1st learning the technique in the early 70's riding a Trident. Several circuit race seasons of clutchless shifting in the early 90's on the Triton gave no trouble from its' 5speed.

Quote:
I think the bush in the gears sometimes move, some have a notch cut in the gear and the bush is peened into it to stop it happening.
You said the box was built from parts?

I'll wash and inspect all the cogs, and check bushings as you suggest. Yes, the box was built from leftovers or otherwise rejected parts. In fact the whole engine is too. It's a wonder it goes as well as it does. Mismatch issues can surprise you for the darndest of reasons! Gearbox is all B range, unless I'm mistaken.

Quote:
The 4 speed and 5 speed pawls are different
Yes, I'm aware there is a difference. One of mine has an shallow groove which if I recall indicates 5speed while the other has the identical cutaway. I've had to troubleshoot bikes with 4speed pawls in 5speed boxes before. That fault gives different symptoms.

Quote:
I've shimmed my positive stop up so it slighty under selects. Momentum carries the plunger into the v notch. I assembled the camplate and selector mechanism and dropped a bulb thru the sleeve gear bearing to see what was happening. The shims are pieces of angle held under the pawl plate which has to relieved a bit to take them. There's a good photo of some in the Shenton book, showing the 5 speed Quaife which uses the same principle.

I looked at the Shenton book. That was early days for 5speed!
The bulb through the sleeve gear is a super cunning idea.

Quote:
When third jams, is it actually because you're still trying to force second in as the lever and pawls haven't restored to centre?

I think you're suggesting that the lever hasn't come back to its' home position in order that the upshift pawl can latch into the next "tooth". In order to test this possibility, I increased the spring tension by adding an extra spring, externally to the gear lever, . The "lock up" problem was exactly identical, no change whatsoever.

Thanks. It gives me time to reflect and consider some possible solutions.

#427361 - 04/01/12 5:35 pm Re: T140 5speed gearbox selectors [Re: Excalibur]  
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John Healy Online content
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Boston, Massachusetts
No meaning full discussion about shifting problems can be made unless one know which iteration of the five speed layshaft is installed in the engine. Beside the last iteration sporting a stronger/wider high gear, positive location of that gear was made by incorporating a circlip stop.

Earlier versions would allow the splined high gear to move under pressure, and capture the adjacent rotating gear. If the rotating gear isn't free to move (.010" clearance) it makes it difficult for it to change speed in its attempt to mate with the sliding gear which engages it.

I am also fond of the early five speed camplate made to be used with the leaf spring detent. I find the roller tracks better formed and provide for smoother changes between gears. You do have to modify the detents to make them look more like the later plunger style. This allows me to choose the amount of pressure I have on the camplate via the detents. AND to make it easier to install without removing mainshaft high, reshape a large portion of it so it looks like the later camplate.

I have to emphasize what Dave Madigan mentioned above about the importance of the clearance between the face of the camplate and the top face of the shift forks. Too much clearance and the fork tilts causing it to jamb hindering movement. To little, and you risk the faces binding if the camplate isn't rotating square to the faces of the forks.

Because time is the elephant here some thought should be given to the viscosity of the lubricant used. To make the shift you must get two gears spinning at the same rpm without the aid of syncro-rings. You are relying on the viscosity of the oil to get the two gears to reach similar speeds and allow the dogs to align. Because you don't have to take into consideration longevity there are a lot of options to explore.

Once sorted, the late version of the 5 speed is virtually bulletproof.

Last edited by John Healy; 04/01/12 8:55 pm. Reason: canged mainshaft to layshaft

#427478 - 04/02/12 6:31 am Re: T140 5speed gearbox selectors [Re: John Healy]  
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Excalibur Online content
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Excalibur  Online Content
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John
Thanks. I'm so pleased you've brought these issues up!
Quote:
No meaning full discussion about shifting problems can be made unless one know which iteration of the five speed layshaft is installed in the engine. Beside the last iteration sporting a stronger/wider high gear, positive location of that gear was made by incorporating a circlip stop.
Earlier versions would allow the splined high gear to move under pressure, and capture the adjacent rotating gear. If the rotating gear isn't free to move (.010" clearance) it makes it difficult for it to change speed in its attempt to mate with the sliding gear which engages it.

As it turns out, the layshaft gears are the earlier ones and is showing signs of moving on the spline. I have a good later shaft and with gears marked "B". I measured the clearance between the 2 gears at .007". Is this enough?


Quote:
I am also fond of the early five speed camplate made to be used with the leaf spring detent. I find the roller tracks better formed and provide for smoother changes between gears. You do have to modify the detents to make them look more like the later plunger style. This allows me to choose the amount of pressure I have on the camplate via the detents. AND to make it easier to install without removing mainshaft high, reshape a large portion of it so it looks like the later camplate.

Good points. I would have used the earlier one but the later was lighter, so I went with it. So what I'll do is cut down an earlier camplate to the same profile and I have a detent that fits. See pic:

The lower camplate and the detent to the left is what I'm proposing to use. The one to right is what I used with the later camplate. Easy to see the difference in point style.

Quote:
Because time is the elephant here some thought should be given to the viscosity of the lubricant used. To make the shift you must get two gears spinning at the same rpm without the aid of syncro-rings. You are relying on the viscosity of the oil to get the two gears to reach similar speeds and allow the dogs to align. Because you don't have to take into consideration longevity there are a lot of options to explore

That's something I can tweak and tune with. I've been using lighter oil this last season, chasing more horsepower. What is difficult to know is whether lighter oil makes for more power delivery. Certainly the bike got an awesome time but might have done just as well with heavier?? Am unsure.

While I'm on the subject, I should ensure all the gears are B range. I notice some spare gears I have are marked... and some exact duplicates are not. Did some get marked, while others didn't. Perhaps later on, the factory didn't bother or such?
Just how many got upgraded?

Quote:
Once sorted, the late version of the 5 speed is virtually bulletproof.

That is so true!

Thanks!!

#427481 - 04/02/12 7:11 am Re: T140 5speed gearbox selectors [Re: Excalibur]  
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Phatt Bob Offline
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My experience with the lower centre camplate is nothing but bad. May have been a dodgy pattern plate or something else which I subsequently fixed, but I always found the plate with the flat land between the notches tended to skip gears, whereas the one with the domed land was OK.

I also found there was an optimum shape to the plunger point, striking a balance between positive location, and ease of getting it to shift. Somewhere between both your shapes, mimicking the groove in the plate.

Bob


Phatt Bob
'95 Daytona 1200
'98 Daytona 1200 dragbike
ex-850 T140 Caff Racer, 850 Triton, Morgo T120, Starfire and Pretend Daytona 500 owner
#427529 - 04/02/12 5:25 pm Re: T140 5speed gearbox selectors [Re: Excalibur]  
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John Healy Online content
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Quote:
I am also fond of the early five speed camplate made to be used with the leaf spring detent. I find the roller tracks better formed and provide for smoother changes between gears. You do have to modify the detents to make them look more like the later plunger style. This allows me to choose the amount of pressure I have on the camplate via the detents. AND to make it easier to install without removing mainshaft high, reshape a large portion of it so it looks like the later camplate.


The early camplate cannot work without some work. Besides removing the portion that keeps you from removing it without taking out high gear, you need to massage the outer detent edge to more closely resemble the later iteration. It is the shift fork tracks that I am after and I will do the extra work required to get them!
John


#427591 - 04/02/12 11:32 pm Re: T140 5speed gearbox selectors [Re: John Healy]  
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Excalibur Online content
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Thanks for the comments.
A study of the camplates shows the earlier one is tidier in the tracks than the later one I've been using.
It appears to me that the later style is less likely to find false neutrals because of the ramping/funneling effect of the detent design.
Looking at adapting the the early one, it appears easy enough. The extra tall bump at 1st gear wouldn't be possible without building it up. Also the top gear bump might be slightly shorter as well. Maybe TIG weld a spot of stainless? John, have you found this necessary? Did you re-harden after reshaping/ramping the detents?

It seems that the detent notches, spring tension and detent pin shape are in a fine balance to work nicely. For example, if the tension is too high or notches too deep, the shifting will be stiff and awkward. If the opposite is the case, over shifting could come into play.
I want to use air shifter next season so have this to consider as well.

Other things I notice is the flatness of the later one isn't what it should be. It's cupped a few thou. Its' gear is not well finished at the thrust face. The gear on the earlier was loose though fixed with a light peen of the locating pins.
Currently the weight difference is 43grams (1.5oz).

Comments appreciated. Thanks.

#427627 - 04/03/12 7:45 am Re: T140 5speed gearbox selectors [Re: Excalibur]  
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Just to expand on Dmadigans comment on putting ears on a straight line plunger why not take it one step further and include a small roller between those ears and reshape the detents to match. This should make for a much smoother operation and is how radial engine aircraft cam followers are designed to follow the track of their cam ring. I'll have to look and see how much room is in there, I never thought the pointy plunger digging into the cam idea was optimum...Mark

#427657 - 04/03/12 1:24 pm Re: T140 5speed gearbox selectors [Re: Excalibur]  
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John Healy Online content
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Quote:
It appears to me that the later style is less likely to find false neutrals because of the ramping/funneling effect of the detent design.


But it is a simple matter of grinding the edge of the earlier camplate to more closely match the later version. Although a time consuming job when done by hand, and a well dressed bench grinder, I have been modifying the earlier camplate for years. I want the tracks from the early leaf spring detent combined with something like the edge pattern of the later.

Personally I use, and prefer, the plunger on the right of your picture. It isn't "pointy" as described by Mark, but once in the camplate detent "V" accurately locates the camplate. I also have a cutaway gearbox that allows me to check the operation of the bits before I put it an engine (There is a picture of it in an issue of Vintage Bike).

Triumph spent an awful lot of money developing the early version of the camplate. Rather than machining the track with a cutting tool, it was punched.


#427700 - 04/03/12 4:40 pm Re: T140 5speed gearbox selectors [Re: John Healy]  
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John, not to stray to far from Ex's post, but were the early leaf spring/camplate problems because of the spring, the lower profile cam plate or both? We used to double up on the leaf springs and stopped short of any real analysis (kids). I guess I'm stuck on the roller/plunger idea because I can also visualize a leaf spring with the end folded in a U with a roller trapped in between and the leaf ears extended above the roller to keep it trapped along the cam plate and this is why my project bike is still a project...Mark

#427738 - 04/03/12 7:42 pm Re: T140 5speed gearbox selectors [Re: Excalibur]  
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John Healy Online content
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There were many people who owned and rode there Triumph with a leaf spring that didn't know that the spring set-up wasn't any good until some "helpful" mechanic told them. But for racing the plunger design seems to work better.

Do you want the camplate to turn easier? Would that make it easier for it to overshoot the detent. Don't you want a bit of friction between the detent and the edge of the plate. And the question, is can you fit a roller in the space available. There isn't much space between the edge of the camplate to bottom of the case.


#427857 - 04/04/12 5:01 am Re: T140 5speed gearbox selectors [Re: Excalibur]  
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MarksterTT Offline
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John, I don't remember what shifting symptom caused us to dbl. up on the springs, I didn't own a leaf spring shifter but was a young "helpful mechanic" who was told to do it by the boss. I took a close look with a magnifier at the late model cam plate and now I know why you prefer the earlier stamped version, those machined tracks are very rough on the late model, I've learned so much on this forum...still the best by far...thanks...Mark

#427859 - 04/04/12 5:13 am Re: T140 5speed gearbox selectors [Re: John Healy]  
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Excalibur Online content
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John, the cutaway gearbox idea is a gem. I should be able to find a right crankcase housing that's otherwise not worth repairing. Could be invaluable for when I set up the air shifter as well.

I agree about the plunger being a better bet than leaf spring.

Thanks to all for the thoughts.


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