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Stopping a slipping clutch. #462435
11/08/12 7:34 pm
11/08/12 7:34 pm
Joined: Mar 2005
Posts: 460
Cincinnati, Oh
Jethro Offline OP
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Cincinnati, Oh
Just wanted to post a few things for those who have, or who will, struggle with a slipping clutch. I have a 72 T120 which I just rebuilt into a 750cc. By the way, some past research here led me to believe the 750 conversion might lead to more vibration, and little increase in power. That has not been the case. Engine runs smoother, and puts out a lot more power, which leads me to the slipping clutch issue! smile

Before I post photos and what I did to stop the slipping, I want to say that this is not to be ignored. The constant slipping of the plates will eventually glaze over the metal discs until they are polished, and will never grip. Additionally, we want to put horsepower to the ground; a slipping clutch is wasteful.

After the rebuild the clutch could not take the additional torque, and began to slip. I took it apart. Checked the plates for glazing and metal discs for flatness. Additionally I took a fine metal file and removed some burrs inside the housing and on the tangs of the metal discs so that the clutch plates would move freely. Measured the fiber discs and visually inspected. I had Barnett plates in but they appeared worn. Put in new, made in the USA plates from DOMIRACER. They looked great. Measured springs and they were slightly compressed. New springs. Adjusted springs and made sure clutch basket did not "wobble" while kicking over, and pressure plate was level and remained level while deploying clutch lever. Put in exactly the right amount of oil (I share with the engine), and the right type. Properly adjusted clutch using the manual. I mention these things because the above steps may stop a slipping clutch.

Clutch still slipped past about 3,000 rpm. Poopy.

As an aside, some people think that the Triumph design guarantees a slipping clutch. I disagree. I think that if the primary is properly filled, with the right type of fluid, and the oil performs it's purpose, which is to say, lubricate the primary chain, then the wet type clutch should work correctly. Hell, it works on my Harley like a champ, and I am putting out some SERIOUS horsepower/torque. But, there are some weaknesses to the Triumph design.

Anyway, took it apart, took the metal discs and cut a half inch groove at an angle. Not my idea, but a tip from a well respected Triumph mechanic. Had heard of this before. Filed off all metal edges. Next, sandblasted the metal discs. Leaves a definite surface roughness. Cleaned all in Dawn detergent and then installed with the angled cut as shown. Additionally I tightened the springs to the degree shown. Yes, the clutch lever works a little stiffer, but I make sure the cable is new, clean, and lubed.

Anyway, SLIPPING BE GONE!











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Re: Stopping a slipping clutch. [Re: Jethro] #462440
11/08/12 8:14 pm
11/08/12 8:14 pm
Joined: Jan 2008
Posts: 1,522
Farmington,Connecticut,USA
JBMorris Offline
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Hi Jethro,
Same subject with a similar fix: right here a few post's down the leaderboard list
http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=461696#Post461696
. . .and a photo
http://www.triumphrat.net/attachments/me...-clutch-mod.jpg

Trying to figure out the ball bearing deal- stress relief?


1978 Bonneville T140V PX
Re: Stopping a slipping clutch. [Re: JBMorris] #462448
11/08/12 9:12 pm
11/08/12 9:12 pm
Joined: Mar 2005
Posts: 460
Cincinnati, Oh
Jethro Offline OP
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Jethro  Offline OP
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Cincinnati, Oh
Originally Posted By: JBMorris
Hi Jethro,
Same subject with a similar fix: right here a few post's down the leaderboard list
http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=461696#Post461696
. . .and a photo
http://www.triumphrat.net/attachments/me...-clutch-mod.jpg

Trying to figure out the ball bearing deal- stress relief?


Sorry, didn't mean to rehash something on the board. I WILL say, though, that I think that is too aggressive a modification, but then again, I am finding out that as I learn I know less and less.

Re: Stopping a slipping clutch. [Re: Jethro] #462451
11/08/12 9:35 pm
11/08/12 9:35 pm
Joined: Jan 2008
Posts: 1,522
Farmington,Connecticut,USA
JBMorris Offline
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Quote:
Sorry, didn't mean to rehash something on the board


Jethro,
Don't be sorry just because this came up elsewhere and I am not the Forum Police!

My curiosity is how and why these fixes originated and thought you would be interested with the drilling and ball bearing bit?

Where is beltdriveman when you need him?

The modification has the appearance of a diaphragm type setup

Last edited by JBMorris; 11/08/12 9:37 pm. Reason: spelling

1978 Bonneville T140V PX
Re: Stopping a slipping clutch. [Re: Jethro] #462471
11/09/12 12:14 am
11/09/12 12:14 am
Joined: Jul 2009
Posts: 3,549
Vic. Australia
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Pete R - R.I.P. Offline
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Originally Posted By: Jethro
I WILL say, though, that I think that is too aggressive a modification, but then again, I am finding out that as I learn I know less and less.


I would agree that a shorter cut makes less of a hinge in the plate.I would expect the plate with the weak hinge to distort more with heat,although it wouldn't take much force to push it flat again.

Carroll Smith said "An engineer can do something for 10 cents,that any damned fool can do for a dollar".Some of these clutch fixes seem too involved and time-consuming for my liking.I'm still not convinced enough to start cutting up plates to fix problems I don't have.

There is another alternative that costs about $10,and takes less time.I know that's a little more than 10 cents,but some suggestions lately cost a lot more than a dollar.

I don't have heavy clutch springs or plates that look like a cheese-grater.I don't seem to have any trouble with plates releasing.
This link might help,and there is another link in it; Stopping Clutch Slip

Re: Stopping a slipping clutch. [Re: JBMorris] #462473
11/09/12 12:14 am
11/09/12 12:14 am
Joined: Aug 2012
Posts: 128
wisconsin
J
jurbanec Offline
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wisconsin
Hmmm. Is it the fact that your surface roughness is much higer providing a higher friction coefficient allowing your clutch to transfer more torque or do the slots you cut allow the plates to flex for better contact... or a combination of the two. I'm curious what our moderator thinks of this modification?

Re: Stopping a slipping clutch. [Re: Jethro] #462480
11/09/12 1:14 am
11/09/12 1:14 am
Joined: Jun 2010
Posts: 523
Maine
M
MikeinBiddeford Offline
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Maine
Fair warning. I do not know what I am talking about, but that has never stopped me from having an opinion. I believe that is why the internet was invented in the first place.

Anyway; The friction part of the plate is about 1" from the edge of the plate towards the center. On my Harley it is about 3/8".
So the Triumph engineers logic may have been to keep adding more and more friction material so the clutch would have more and more area to grab.
The Harley engineers put a smaller ring of friction material so that there are more pounds per square inch on the friction material.

Somebody need to take one for the team. They need to grind/cut off half the diameter of friction material and see if it makes a difference.

Barnett isn't going to do it. They are paid to make a clutch to spec. They are not paid to design them.

I changed to the "right oil" and I replace my clutch cable and my problem went away. But the next time my clutch acts up, I swear, that is what I am going to try.


Please do not believe anything I write. I am a hack but I like to guess the right answers.
Re: Stopping a slipping clutch. [Re: MikeinBiddeford] #462483
11/09/12 1:40 am
11/09/12 1:40 am
Joined: Jan 2008
Posts: 1,522
Farmington,Connecticut,USA
JBMorris Offline
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Originally Posted By: beltdriveman
If you talk to a few olde Triumph dealers in the USA you may hear from one...'I got really fed up with owners trucking their bikes back to mew telling me that as I sold them the ******* lump I could ******* well free off the ******* clutch..which I always did for free. This was one of the reasons I started making dry running belt drive systems for them'.
Please try to remember that a motor cycle multiplate friction clutch is supposed to possess a few VERY BASIC qualities some of which are that it should
1.NOT slip when fully engaged.(Guess you still have to find yours will!!)
2.Free off INSTANTLY and without drag whenever required.(You know that doesnt apply to yours)
3.Be EASILY operated by the rider.(Ridden around town changing gear every half a minute or so for an hour and you will know that doesnt apply either!!)
4.Possess the LIGHTEST rotating weight reasonably possible.(When you eventually take the unbalanced gearbox breaking flywheel out and weigh it you will realise that one doesnt apply to it either!)
As one of Mr Turners assistants said to me when, a couple of years ago,I asked him to describe the Triumph Tiger Cub clutch his comment could equally apply to the lump fitted to the 750.......It was **** when Edward designed it and it was still **** after we modified it to shove the ball race in for the basket to run on'.Apparently Edward Turner designed(if thats the right word) it so it was a plain metal to metal contact and after a few hundred miles road testing took a look at it and signed off the drawing for production......of course after a few more hundred miles use on production bikes it gave problems...........
Must admit I have never ben impressed with Barnett...especially after I phoned them to ask for the Coefficient of friction value for design purposes of their 'carbon' friction plates and I was told it was secret.........I suspect they didnt know what a Coefficient of Friction was!!!. Naturally I then found out who made the material and they sent me all the data on the material..


1978 Bonneville T140V PX
Re: Stopping a slipping clutch. [Re: MikeinBiddeford] #462484
11/09/12 1:53 am
11/09/12 1:53 am
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Vic. Australia
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Pete R - R.I.P. Offline
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Originally Posted By: MikeinBiddeford

The friction part of the plate is about 1" from the edge of the plate towards the center. On my Harley it is about 3/8".
So the Triumph engineers logic may have been to keep adding more and more friction material so the clutch would have more and more area to grab.

It's like tyres;the extra area gives you longer life of the part (provided it doesn't slip when it's not meant to).The grip is not improved with more area at less pressure.

The mean radius of the friction material is proportional to the maximum torque without slippage.Cut away the inner half of the friction material and you increase the mean radius.

If the clutch wasn't slipping under load in the first place,you've just doubled the pressure and wear on the plates for nothing.

Adding an extra steel plate and one friction surface to mate to it takes you from 5-1/2 effective steel plates to 6-1/2 effective steel plates (better than 18% improvement,and even less wear on each plate).

Cutting away the inner 1/2 of the friction material may give the same grip,but double the wear.

Re: Stopping a slipping clutch. [Re: jurbanec] #462485
11/09/12 2:04 am
11/09/12 2:04 am
Joined: May 2011
Posts: 134
Muriwai,New Zealand
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Llewelyn Offline
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Muriwai,New Zealand
Surface roughness has nil to do with it.Mod was done after experiencing difficulty with dragging, freeing up clutch and occasional slipping after replacing plates.One look at plates after a few thousand miles showed uneven and opposed polished spots indicating buckled plates,though better with a bit of hammer and anvil work I proceeded to slot plates with result as shown in image full contact even with lower spring pressure.
Compressing edge of hole with ball bearing is not stress relieving but a way of preventing formation of cracks ,like shot peening rods/valve springs,though there is very little force applied to area around the hole.Once clutch is disengaged the plates rotate with clutch centre so doubt centrifugal force and speeds centre rotates would be enough to break plates and when clutch all clamped up they are held tight enough to transmit engine power.Slipping the clutch on takeoff still will not provide rotational speed as plain plates stationary till accelerated to friction plate speed .
Most modern clutches i have seen do ,as mike says,have a much narrower friction area on plates and this poss. would help lessen differential heating of the plain plate causing buckles to develop along with increased psi.
Though im really easy on clutches this mod served it purpose for 3/4 of my triumphs miles they are still good enough to reuse.
Only posted the mod to show how i solved the problem and to stimulate a bit of discussion,had a bit of "dont like grated cheese"etc but yet to hear any valid rational arguements to disprove this mod theory .I know no theory can be proven only disproved but it has served it purpose perfectly enough for me to be confident it works, so where are the rational arguements?

Re: Stopping a slipping clutch. [Re: Jethro] #462502
11/09/12 6:55 am
11/09/12 6:55 am
Joined: Jul 2007
Posts: 451
redondo beach, ca
Bob G Offline
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redondo beach, ca
I am going to try Mr. Pete's extra plate mod in conjunction with the slotted plate mod and see how they turn out. I want to see if I can use less clutch spring pressure.


Bob Gregor
Re: Stopping a slipping clutch. [Re: Llewelyn] #462512
11/09/12 8:58 am
11/09/12 8:58 am
Joined: Aug 2001
Posts: 1,081
Cheshire UK
Phatt Bob Offline
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This will stop it slipping. Good for 100bhp and user friendly on the road too.



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
Re: Stopping a slipping clutch. [Re: Jethro] #462525
11/09/12 11:10 am
11/09/12 11:10 am
Joined: Jul 2012
Posts: 1,634
UK Berks
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AngloBike Offline
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UK Berks
what the heck is that?!

Re: Stopping a slipping clutch. [Re: Jethro] #462555
11/09/12 5:32 pm
11/09/12 5:32 pm
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Posts: 7,459
scotland
triton thrasher Offline
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Centrifugal, by the look of it.


Amateur Loctite enthusiast.
Re: Stopping a slipping clutch. [Re: triton thrasher] #462565
11/09/12 7:02 pm
11/09/12 7:02 pm
Joined: Aug 2001
Posts: 1,081
Cheshire UK
Phatt Bob Offline
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"Centrifugal, by the look of it"

Tritonthrasher is right. Its whats commonly called a lock-up clutch. Its basically a plate which overlays the standard plate and locates on the clutch springs. In the plate are right angled fingers which bear on the pressure plate at one end and have bobweights (M6 bolts and nuts) on the other.

As it spins up the centrifugal force applies additional pressure to the plate, effectively locking it up.

This is it in kit form:



The fingers are made by MTC in the states, but the plate you have to make yourself.

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
Re: Stopping a slipping clutch. [Re: Jethro] #462575
11/09/12 8:41 pm
11/09/12 8:41 pm
Joined: Sep 2012
Posts: 13
Ca Los Angeles
BananaGas Offline
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Anybody ever heard of or used a stuffer clutch plate from Barnett?
found this on eBay

http://www.ebay.com/itm/Barnett-Triumph-...6b3&vxp=mtr


1968 T120R
Re: Stopping a slipping clutch. [Re: Phatt Bob] #462578
11/09/12 9:20 pm
11/09/12 9:20 pm
Joined: Mar 2005
Posts: 460
Cincinnati, Oh
Jethro Offline OP
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Jethro  Offline OP
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Cincinnati, Oh
Originally Posted By: Phatt Bob
"Centrifugal, by the look of it"

Tritonthrasher is right. Its whats commonly called a lock-up clutch. Its basically a plate which overlays the standard plate and locates on the clutch springs. In the plate are right angled fingers which bear on the pressure plate at one end and have bobweights (M6 bolts and nuts) on the other.

As it spins up the centrifugal force applies additional pressure to the plate, effectively locking it up.

This is it in kit form:




Bob


OK... I WANT one of these. Mainly I just want the clear porthole effect so I can watch it spin around, although that may be hard while riding.

The fingers are made by MTC in the states, but the plate you have to make yourself

Re: Stopping a slipping clutch. [Re: Jethro] #462584
11/09/12 9:46 pm
11/09/12 9:46 pm
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Posts: 3,821
ohio
shel Offline
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You have to modify the cover for clearance as well.


When given the choice between two evils I picked the one I haven't tried before
Re: Stopping a slipping clutch. [Re: BananaGas] #462588
11/09/12 10:27 pm
11/09/12 10:27 pm
Joined: May 2005
Posts: 3,821
ohio
shel Offline
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Originally Posted By: BananaGas
Anybody ever heard of or used a stuffer clutch plate from Barnett?
found this on eBay

http://www.ebay.com/itm/Barnett-Triumph-...6b3&vxp=mtr


I suppose if you had an extra plate laying around you could grind the material off one side and give it a try for free.


When given the choice between two evils I picked the one I haven't tried before
Re: Stopping a slipping clutch. [Re: shel] #462589
11/09/12 10:33 pm
11/09/12 10:33 pm
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Posts: 1,522
Farmington,Connecticut,USA
JBMorris Offline
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Originally Posted By: shel
I suppose if you had an extra plate laying around you could grind the material off one side and give it a try for free.


not a bad idea!

What is the orientation of the 'stuffer' plate within the stack?

The Barnet plate as shown is fully bonded for the width of the plate.



1978 Bonneville T140V PX
Re: Stopping a slipping clutch. [Re: Jethro] #462594
11/10/12 12:11 am
11/10/12 12:11 am
Joined: Mar 2005
Posts: 10,158
Boston, Massachusetts
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John Healy Offline

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Boston, Massachusetts
As mentioned above by Pete, the workings of a clutch by several factors. They include:
Mean effective radius of the clutch facing.
Coefficient of Friction of the material.
Number of clutch surfaces.
Spring pressure.

The amount of Torque a clutch can transfer is N x f x Fa x Rm
Where N = number of friction faces in contact.
f = coefficient of Friction of the clutch material itself.
Fa = clamping force supplied by clutch springs.
Rm = Mean Radius of the friction facing.

Using the modern type of narrow friction facing as supplied by Surflex for Hyde and Aerco Triumph clutch kits increases the Mean Effective Radius. There is also an additional surfaces being that they use 7 plates instead of 6. They are also much less prone to sticking! They cure a lot of real, and perceived, problems with Triumph clutches, but at a price!

The old cork facings had a high coefficient of friction but poor wear qualities. Rubber cork facings have better wear characteristics, but lower coefficient of friction. Oil further reduces the facing's coefficient of friction. Modern oil with friction modifiers reduce it even further to where it almost reduces it to zero.

There are about 5 different Triumph clutch springs.

The most common are:
57-1560 used in the 650 twins with 4 springs. At a typical fitted length of 1.325" * they provide 32 lbs each or 128 pounds total clamping force.

57-1830 used on the 650 twins with 3 springs. At a typical fitted length of 1.325" they provide 43 lbs each or 129 pounds total.

57-4644 used on the 750 twin with 3 springs. At a typical fitted length of 1.325" they provide 53 lb each or 159 pounds total. You can use these in your 650 if you feel you need more pressure.

The Emgo replacement and the Barnett High Performance springs are both equivalent of the 57-1830 at 45 lb each. These are not to be used in a 750!!

The Precision Machine High Performance kit at a typical fitted length of 1.325" provide 72 lb each or 225 pounds total. When the nut is screwed in flush with the end of the stud you can get 93 lbs each or 279 pounds.

* A fitted length of 1.325" has the stud just level with the bottom of the clutch spring nut's tightening slot. For most applications this is all of the pressure you will need. When the stud is flush with the nut the fitted length is 1.185".

If you tighten the nut so the stud is flush with the face of the nut (fitted length of 1.185") you can add approx. 25% additional pressure. This increase the effort required to pull in the clutch lever.

The selection of engine oil, when the clutch shares oil with the engine, can have an effect upon clutch slippage. Modern API oils SH or later are not recommended for engines that share clutch and engine oil. Use API-SG 20/50 with a JASO rating of MA or MA2 for these applications.

I put the full story in the 2009-2 Vintage Bike Magazine.
Hope this helps!
John Healy


Re: Stopping a slipping clutch. [Re: shel] #462596
11/10/12 12:15 am
11/10/12 12:15 am
Joined: Mar 2005
Posts: 460
Cincinnati, Oh
Jethro Offline OP
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Cincinnati, Oh
Originally Posted By: shel
You have to modify the cover for clearance as well.


I am absolutely up for that. I love to weld.

Re: Stopping a slipping clutch. [Re: JBMorris] #462601
11/10/12 1:24 am
11/10/12 1:24 am
Joined: Jul 2009
Posts: 3,549
Vic. Australia
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Pete R - R.I.P. Offline
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Originally Posted By: JBMorris

What is the orientation of the 'stuffer' plate within the stack?

The Barnet plate as shown is fully bonded for the width of the plate.

This plate is 0.115" thick. It is a driven plate (anchored to the cush-drive),with a friction lining on one side.

It could be used to create a 6-1/2 plate clutch,instead of 5-1/2 effective plates (similar to the Hyde "7-plate" or 1981-onward Triumph "7-plate",which were effectively 6-1/2 plates).The friction lining would face the bottom of the basket (first plate in).That friction lining would grip against the bottom of the basket.You would need to carefully de-burr the holes in the basket,so it didn't act as a cheese-grater on the friction lining.

It would be far better to have the friction lining glued to the bottom of the basket and just use an extra steel plate,as Triumph eventually did.

Another link: "7-PLATE CLUTCH"


Last edited by Pete R; 11/10/12 3:05 am. Reason: fixed link
Re: Stopping a slipping clutch. [Re: Pete R - R.I.P.] #462605
11/10/12 1:56 am
11/10/12 1:56 am
Joined: Jan 2008
Posts: 1,522
Farmington,Connecticut,USA
JBMorris Offline
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Quote:
You would need to carefully de-burr the holes in the basket


Thanks Pete,

Have been hearing about this conversion for some time and am now starting to 'get it'.

De-burring is a point well taken and should be no problem to do.

Quote:
It would be far better to have the friction lining glued to the bottom of the basket and just use an extra steel plate,as Triumph eventually did.

Very interesting indeed,never heard that one before and wonder what type of lining (and width)and type of glue was used?

Btw, the link for '7-PLATE CLUTCH' slipped into database error!


1978 Bonneville T140V PX
Re: Stopping a slipping clutch. [Re: JBMorris] #462609
11/10/12 3:23 am
11/10/12 3:23 am
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Vic. Australia
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Pete R - R.I.P. Offline
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Originally Posted By: JBMorris

Very interesting indeed,never heard that one before and wonder what type of lining (and width)and type of glue was used?

Previously,I've used thin cork sheet (gasket material) and contact adhesive.The friction material has as much grip in the basket as it has grip against the driven plate;the glue is not highly stressed.Use enough cork to cover the full width of the driven plate.You can cut it out around the holes,because it's useless on the hole.

I'll try thick paper gasket material next,instead of cork (about 0.030" thick).

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