Author Topic: Anybody with Twenty One / 3TA experience?  (Read 34156 times)

Offline dunboyne

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Re: Anybody with Twenty One / 3TA experience?
« Reply #15 on: August 05, 2013, 08:40:45 PM »
my 21 rollers do not fit perfectly and there is a gap left if they are all pushed tight together , there is some play in the basket but not enough to hit the casings . mine is a 58 motor . ill try put a pic up shortly .
the chain adjuster was retro fitted by owners so its no way to judge the motors age. mine is a distributor type engine .
keep her lit

Offline Rex

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Re: Anybody with Twenty One / 3TA experience?
« Reply #16 on: August 05, 2013, 10:27:19 PM »
There's a problem here then, as Triumph only fitted 20 rollers....

Offline dunboyne

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Re: Anybody with Twenty One / 3TA experience?
« Reply #17 on: August 05, 2013, 10:35:30 PM »
There's a problem here then, as Triumph only fitted 20 rollers....
lol
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wetdog

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Re: Anybody with Twenty One / 3TA experience?
« Reply #18 on: August 05, 2013, 10:44:17 PM »
hate to agree with rex  :D but same here 

Offline dunboyne

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Re: Anybody with Twenty One / 3TA experience?
« Reply #19 on: August 05, 2013, 10:51:35 PM »
the pic , you might be able to see the primary chain adjuster at the bottom , theres possibly a roller missing in this pic as well but i do remember they did not fully fill the space .
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wetdog

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Re: Anybody with Twenty One / 3TA experience?
« Reply #20 on: August 05, 2013, 11:08:21 PM »
very nice and a very good engine , if the rollers are tight they over crowed ? not what you want , you might want to change the ht caps they look metal , and the jap ones can track in the wet

Offline Bomber

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Re: Anybody with Twenty One / 3TA experience?
« Reply #21 on: August 06, 2013, 12:57:37 AM »
guys.. I might be "Stating the bleeding obvious" but I think when Dunboyne said "my 21 rollers", I think he meant his Triumph 21 rollers rather than the quantity of the said item....
If iver tha does owt for nowt alus duit for thissen

wetdog

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Re: Anybody with Twenty One / 3TA experience?
« Reply #22 on: August 06, 2013, 08:46:59 AM »
that would make more sence , not just my spelling now my readings sh*T

Offline Rex

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Re: Anybody with Twenty One / 3TA experience?
« Reply #23 on: August 06, 2013, 10:44:30 AM »
If Dunboyne has the original 3TA primary chaincase (which I think he said he did) the problem could be that that clutch basket looks to be the later deeper one, while the earlier 350s had a 4 (?) plate shallower basket, so the rubbing could be clearance issues rather than the actual basket rocking.

wetdog

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Re: Anybody with Twenty One / 3TA experience?
« Reply #24 on: August 06, 2013, 11:01:35 AM »
i think he must have the latter case as its fitted with the primmary tentioner , which on my 500 runs thro the primmary , i see the frame is also the latter type
« Last Edit: August 06, 2013, 11:04:47 AM by wetdog »

Offline antoni

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Re: Anybody with Twenty One / 3TA experience?
« Reply #25 on: August 11, 2013, 08:59:49 AM »

6mm is about 0.236" and 15/64 is 0.234375", both very close to the figure given by Rex. I know nothing about this clutch but assume that there was some end float in the original so that the odd thou and a bit wouldn't be enough to bind anything. Unless 1/4" (0.250") long rollers have been used and one or more washers have been left out?

Very hard to help Antoni without having a look - correctly set up there should be essentially no wobble. The answer is to measure everything (bearing inner and outer and the rollers with vernier and micrometer) and inspect the bearing tracks under a bright light. The diameter of the inner track + diameter of rollers should be only 0.001" or so less than the inside diameter of the outer track (in the basket). Something's badly amiss if it can wobble enough to hit the primary case!

Leon

Just had a good look over the rocking clutch problem with calipers and mic.

The previous owner replaced the basket during a (failed) gearbox repair and has admitted to being unhappy with the way the clutch went together. He thought it would 'sort itself out'.

I dismantled the clutch to get the gearbox out, not expecting to see any problems with the clutch, but did notice probably recent wear marks on the case cover. So before refitting everything the first time I placed the basket on my Goldring record deck, set 16 RPM and offered a bench grinder's wheel to the edge of the basket. Turning on the cheap. Re-assembled, the clutch functioned but rocked.

Getting the old basket out of the spares pile it looks like by chance I ground it back spot-on. Original 1.635", replacement 1.636".

The rollers' bearing surface on both baskets has a diameter of 1.873". The width of that bearing surface is different; 236th original, 239th replacement. The difference might be put down to wear on the original.

I can see now the reason for the rocking. Looking at the photo, the inner roller bearing surface's width on the 'mainshaft flange' controls the position of the driven bearing hub (pictured resting on the the mainshhaft flange). The hub looks clean and sensible. When the hub is placed over the splines it rests with 269th space left for the rollers and clutch basket flange. So regardless of quarter inch wide rollers or approx 6m ones, the clutch basket is free to float by 269th minus 239th = 30th. So it rocks.

Has the surface on which the roller sits in the picture worn badly? The flange thickness is 176th, very clean and flat but has 'Spirograph' wear marks.

Advice needed!

In the absence of said advice I will try to turn back the width of mainshaft clutch flange roller bearing surface on my small lathe, so that most of the 30th is taken up, and buy new correct rollers. I expect the material will be hard carbon steel but will sacrifice a turning tool or two to get the bike runing.

...runs under the nearest table and dons tin hat...

wetdog

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Re: Anybody with Twenty One / 3TA experience?
« Reply #26 on: August 11, 2013, 10:34:59 AM »
it will not/should not rock when the cluch is assembled and springs loaded , have you tryed this yet ? the measurements you quote as small and im surprised its enough to hit the case , does the chain line up ie is it the correct main shaft
« Last Edit: August 11, 2013, 10:54:53 AM by wetdog »

Offline antoni

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Re: Anybody with Twenty One / 3TA experience?
« Reply #27 on: August 11, 2013, 11:11:08 AM »

It does rock badly when fully assembled and working.

It rocks because there's a 30th difference between the space available for the clutch basket's flange, and the space it takes up.

30 thou becomes a lot more when you consider where that 30 thou play is, toward the middle of the assembly, and where you see the rocking/clouting which is at the outside diameter of the assembly.

Question for me is what to do about it.

Turn back the mainshaft clutch flange bearing surface to let the hub take up the slack?

Or do something less drastic which someone might tell me about!

Never used the word 'flange' so much in my life. John Lennon was fond of it I believe.



Offline Rex

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Re: Anybody with Twenty One / 3TA experience?
« Reply #28 on: August 12, 2013, 08:39:47 AM »
The bottom flange of that centre looks different to the usual Triumph part, so maybe that's an after-market piece with the incorrect taper and/or too thick a bottom flange and allowing the centre to sit too far onto the mainshaft?
If it sits too far on (as also happens if you try and fit a 650 part here) the taper doesn't grab before the flange hits the alloy casing, and although the uninitiated carry on and whang on the clutch nut hoping it  will all be secure and work OK, it doesn't.
Maybe the bloke who originally built it (and hoped the clutch would just sort itself out) didn't understand that centre was located by the shaft's taper?  A loose taper would lead to rock too.

Offline antoni

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Re: Anybody with Twenty One / 3TA experience?
« Reply #29 on: August 12, 2013, 09:04:01 AM »
The flange part is a perfect fit to the mainshaft taper. It correctly aligns the clutch basket sprocket with the engine sprocket.

There are a few different types of clutch - 3 and 4 spring, with and without a 'roller washer'. It may be that I have an incompatible set of clutch parts - or maybe not. It seems an easy fix would be to machine off some of the width of the inner roller bearing surface of the mainshaft taper.
In the real world this bodge might be easier than trying to understand and get the right parts. After all, the clutch could still be replaced in the future.

Another thing to think about is what sliding/rolling surfaces resist the clutch springs when the clutch is disengaged. As far as I can see it's the clutch basket flange pushing against the central hub through the rollers, but 'width-wise'. Don't see any wear marks at all on that part of the hub - so I must have that wrong....

« Last Edit: August 12, 2013, 11:34:24 AM by antoni »