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"wet" clutch.

Oh, boy...


GrandPaul (does not use emoticons)
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Originally Posted by GrandPaul
"wet" clutch.

Oh, boy...
Ever taken apart a Triumph or BSA clutch other than a triple that didn't have oil on the plates? I call that wet , lol.....Perhaps we need to say "damp". Early Sportsters had a sealed clutch assembly running in the primary oil, in theory it stayed dry inside....


79 T140D, 89 Honda 650NT ,61 A10 .On a bike you can out run the demons
"I don't know what the world may need
But a V8 engine is a good start for me
Think I'll drive to find a place, to be surly"
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Originally Posted by Hillbilly bike
Originally Posted by GrandPaul
"wet" clutch.Oh, boy...
Ever taken apart a Triumph or BSA clutch other than a triple that didn't have oil on the plates?...
Side track warning:....As a matter of fact, yes.

I recently did the clutch on my triple because it would barely disengage. The plate was oily. This effectively gummed the whole thing together. An oily triple clutch isn't a nice experience but I only rode it like that up the street a half block, enough to know it needed help. I have no idea if it was slipping under load. Probably was.

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The maximum torque 'T' that can be transmitted by a clutch depends on the following factors:
1. The number of friction surfaces in contact. 'S'
2. The spring force of the pressure plate 'P'
3. The coefficient of friction between the friction material and the plain plate surface 'C'. This must be the coefficient applying to the expected amount of oil on the surfaces.
4. The mean effective radius of the friction surfaces 'R'
The formula used for this calculation is: T=S x P x C x R
There’s no need to worry about the units for each of these parameters as we can draw general inferences without such specifics.

If we are considering any specific clutch, say Hillbilly’s in this instance, S, P and C being held constant, increasing the mean effective radius R linearly increases the torque capability T.

The mean effective radius could be increased by using a wider clutch basket with correspondingly larger radius plates, but we’re not doing that in this situation.

The mean effective radius is roughly the half-way radius of the friction pads.

This is only an illustration, to show the impact:
Say if the inner 10mm of the friction pads are removed, the mean effective radius increases by 5mm.

The usual outside radius of the friction pads is ~76mm
The usual inside radius of the friction pads is ~59mm

So the mean effective radius is ~ 67.5mm

Then removing the inner 10mm of the friction pads moves the mean effective radius to ~72.5mm.
This is an increase of torque capability of 72.5/67.5 X 100 = 7.4%.

Not a massive gain, and you probably wouldn’t remove as much as 10mm from the inside of the pads for a road bike (you might for racing) as that would be ~half the material. So you’d likely remove somewhat less, and gain 4% at a guess.

But every little helps, as is often said, and at least some of the 7-plate suppliers do this as well as the extra plate.

I don’t know the specifics of a BSA pre-unit clutch, but a p/u Triumph had a standard 5 friction plates with 10 friction surfaces. The unit Triumph clutch had 1 extra friction surface (apart from the late ones which had yet one more due to the basket mounted pads). If you add the extra plates that the 7-plate suppliers provide, that adds 2 additional friction surfaces.

So adding an extra friction and plain plate to one of the old clutches produces 12/10 = 20% improvement in torque capability, 13/11 = 18% in a unit clutch.

This is the main gain from the 7 plate kits, with or without the small gain from the mean effective radius change.

Of course there is a trade off when the friction pads are reduced to increase mean effective radius. The wear of the clutch is taken by reduced area, so increased wear is only to be expected. But if the clutch doesn’t slip at high torque (which many ordinary clutches do) then it possibly doesn’t matter too much.

Finally, I would say that my experience with Triumph clutches is to minimise the amount of oil within it, by maintaining the oil level in the chaincase such that it only reaches the lower end of the chain run under the clutch. It functions at its best when as dry as possible. That alone will make a standard clutch work satisfactorily in most ordinary riding experience.

Last edited by koan58; 05/18/21 9:02 pm.
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Once it's bedded in a little, you can cram the extra plate pair in.
Although they sell them i have never managed to get the 7 plate kit
to go into the 4 spring clutch as a new item. Once it's run a while it
will go but then i cannot use the thick rear plate that was used on the
4 spring units. This is of course on A65's not A10'x but maybe the clutch
has similar dimensions just not triplex drive. I can get 6 fibre's into the
basket new and all 7 when bedded in (just) but not the thicker steel.

The point about increasing the inner radius by removing liner is not
new, blokes at race tracks have been doing that for years and yes,
it does work despite all the theory saying otherwise. Mind you, longevity
was not a requirement.

Last edited by NickL; 05/18/21 11:02 pm.
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The theory doesn't say otherwise Nick, practice is consistent with theory.

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Originally Posted by Hillbilly bike
Originally Posted by GrandPaul
"wet" clutch.

Oh, boy...
...Perhaps we need to say "damp"...
I WAS GOING TO SAY THAT!!!

Really.

Easy to test: Add an extra cup of oil to a pre-'69 primary then go for a ride.

THAT is a wet clutch. You DON'T want one...


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Well, the turd went out for a ride today..Steady 60 psi oil pressure, no smoke or funny noises..All was good except some idiot that didn't tighten the rocker box securely , a big oil mess...For sure the top end is getting oil, lol.
And the brakes, front and rear are about the same as dragging my feet. I was doing about 60 mph went to slow down to pull into the driveway and sailed right on by...

The short video show me coming down the road to pull into the driveway, but just sail on by with crappy brakes....

DB34BA9A-6B4A-440F-AFCF-1C2D8DD82DA6.jpeg
Last edited by Hillbilly bike; 05/21/21 7:44 pm.

79 T140D, 89 Honda 650NT ,61 A10 .On a bike you can out run the demons
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The trailing shoe has little braking effect and when it presses against the drum, it stops the cam turning, so the cam can’t put more pressure onto the leading shoe. The leading shoe can have good braking effect, if it’s actually being applied hard.

I think some Enfield brakes were the only common Brit single leading shoe drum brakes that had float in the right direction: that is, the cam could move in line with the direction it pushed the shoe ends. The Enfield brakes still weren’t great.

I’ve tried a few things on my SLS Norton 8” brake and the trick that has worked best so far is the Vintage Motorcycle Club mod, which is removal of lining material from the trailing end of the trailing shoe, so the shoe does not stop the cam turning. Removal of lining from up to two thirds of the shoe length. Sounds extreme, doesn’t it!

I don’t recommend that people alter or interfere with their brakes: it can be dangerous. Just saying what I did.


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TT, good explanation. I can do that...


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So long as brake experiments are done cautiously!


Success may depend on what area of lining material is on the shoe to start with. Some BSA/Triumph shoes had illogical-looking lining patterns.

Last edited by triton thrasher; 05/22/21 5:11 am.

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Other things people try are:

Reduce the size of the cam lobe that works the trailing shoe,

Reverse the lever on the cam spindle, so the cam turns backward. That gives the leading shoe slightly more movement.


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And of course, on a brake like this, the trailing shoe is the one above the cam and its trailing end is the end that is on the cam.

[Linked Image from i.postimg.cc]


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Originally Posted by triton thrasher
Reverse the lever on the cam spindle, so the cam turns backward. That gives the leading shoe slightly more movement.
I'm thinking the factory might have experimented with this change but never actually put it into practice for some unknown reason ?.

The way that i understand it working is > the opposite rotation of the brake cam tends to momentarily hold back the the trailing shoe from contacting the brake drum face while at the same time it advances the leading shoe out forwards to be the first to make contact with the face of the brake drum , The theory behind it all being that if any part of the trailing shoe makes contact first before the leading shoe does it can compromise the brakes efficiency .

Here's a picture i stumbled across a few years ago that i thought was quite interesting , It shows a clever bit of thinking as to how they achieved this brake arm cam reversal , (I haven't tried this 'supposed' upgrade myself yet but it looks pretty kosher)
[Linked Image from i.postimg.cc]

Comparing the standard brake plate & lever set up along side the factory picture
[Linked Image from i.postimg.cc]

With a little bit of help from photo-butchery ! .. It looks to me like they've just rotated the standard brake plate forward by roughly 40deg or so ? and made a new brake plate torque stay , The finishing touches should be quite simple to work out .
[Linked Image from i.postimg.cc]

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Hmm, interesting...But this brake is a lot worse than any stock brake...Got to run it more to see if the shoes bed in. No pulsating so it's likely not out of round....


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All they're probably doing is increasing the leverage by using the inner end of the brake cam instead of the outer end, but without seeing the cam, we can't determine the geometry. Maybe the inner end has a smaller radius.
The brake shoe is levered according to where you apply the force and the ratio of the length of the lever arm to the contact point of the cam. If you want more leverage, you could try shortening the cam (decreasing the radius), but you would get more travel at the handle. Or you could lengthen the lever arm. You could also improve it by using flat ends on the shoes where they ride on the fixed pivot allowing them to self-center in the drum as BSA did on the later brakes, even on the rear on my B50's. Kommando has indicated a way to convert the pivoted end to floating by just elongating the pivot slot so the brake shoe can move as it wants to, assuring maximum contact area especially as the brake shoe and drum wears.

Of course, with your experience, you probably already knew all these tricks of the trade, but it doesn't hurt to be reminded.

Tom

Last edited by koncretekid; 05/22/21 9:55 pm.

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Originally Posted by Hillbilly bike
Hmm, interesting...But this brake is a lot worse than any stock brake...Got to run it more to see if the shoes bed in. No pulsating so it's likely not out of round....

Part of the trouble with pre-1964 Norton SLS brakes was the plate and shoes couldn’t be centred by holding the brake on while you tighten the spindle, because the brake plate was a close fit on the spindle. They enlarged the hole on later SLS brakes and late manuals recommended that early plates be drilled out a bit.


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I have a brake question not related to this topic...Do all the 8 inch front brakes, like the single side or full width or later TLS have the same width but not necessarily interchangeable shoes?


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The later TLS has wider shoes,the conical shoes are slightly narrower, a conical hub type plate will fit an earlier full width hub with a bit of metal removal.

Last edited by gavin eisler; 05/23/21 9:04 pm.

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As well the later 8" singled sided front brake on the A65 and late B44 VS had wider shoes and deeper drum than the 8" singled side brake used on the pre-unit machines. I do not know when the change was actually made or if it was for introduction of the unit machines.

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I weighed the bike today using an accurate bathroom scale under one wheel at a time, bike sitting level...375 pounds....Also weighed the stock frame T140 race bike, 315 pounds....


79 T140D, 89 Honda 650NT ,61 A10 .On a bike you can out run the demons
"I don't know what the world may need
But a V8 engine is a good start for me
Think I'll drive to find a place, to be surly"
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Originally Posted by Hillbilly bike
I weighed the bike today using an accurate bathroom scale under one wheel at a time, bike sitting level...375 pounds....Also weighed the stock frame T140 race bike, 315 pounds....
I bought three cheap scales at WalMart to weigh my ultralight with; also works for bikes - one each wheel, one under the sidestand!


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One scale is accurate enough for me. And lees junk hanging around. lol


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Think I'll drive to find a place, to be surly"
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Originally Posted by Hillbilly bike
One scale is accurate enough for me. And lees junk hanging around. lol
True. While not EXACTLY accurate, it will be more than close enough, unless you need to get down to ounces and grams...

You can add a bit more accuracy (nearer to ounces, maybe) by chocking up the 2 other points with blocks of the same thickness as the scale's height.

Last edited by GrandPaul; 05/28/21 3:08 pm.

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I had Villers Services reshoe my BSA B44 VS front brake, gave them the ID of the drum and the OD of the unlined shoes fitted to the brakeplate. They gave me back shoes that just fitted the drum with a 30 thou clearance and they use MZ gold linings, that brake now matches the 7" TLS I have on the Starfire with original shoes well bedded in for early bit and total effectiveness.

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