Discussion in 'Norton Motorcycle Rebuilds' started by lcrken, Jan 23, 2016.
Looks much better than your mk1 version Ken.
Looking forward to the next instalments ...!
Back to the project, now that the landspeed bike is done, and the next meet is not till next May. After trying the RGM bronze clutch plates in my grandson's 883 cc MK3, where it cured his clutch slip problems, I decided to do the same on this bike. The kit from RGM includes a thinner steel plate, presumably to make the clutch pack thickness correct. But it also has a much larger ID to match the bronze friction plates narrow dimension. This is a picture of the RGM plate compared to a stock Commando steel plate
That looked to me like a good idea, saving some weight in a good spot, so I set up some simple tooling in the lathe to cut the stock plates down to the same dimensions
It worked great. This picture shows the narrowed plates, next to the RGM friction and steel plates.
With the four narrowed stock plates and one thinner RGM plate, the clutch pack is still a little too tall to be able to fit the RGM pressure plate. I'll either have to use another thinner plate, or machine the pressure plate a bit. But it should all work out when done. I'm hoping that this clutch, along with the taller primary ratio I'm using, will give me a no-slip clutch without needing a gorilla grip at the lever.
In other progress, I've finished the mounts for the primary cover, and as soon as I put a couple more coats of clear on it, I'll have new pictures of that. I've also rebuilt two period AP racing clutch and front brake master cylinders, and will have those with some new hydraulic lines to show soon.
Got to get moving on this project in time for next year's rally.
The bronze plates come in two thicknesses. 3.6 mm and 3.2 mm. Not sure which ones you have. I like the fact that you are able to machine the centers out of the old steel ones. Really let’s you fine tune the pack. With CNW hardened clutch center that should be a bullet proof unit.
i have been doing the steels like that for a while. i will say the ones i have are very hard and requires a lot of resharpening but is worth while even with stock friction plates as it increases the torque capacity of the clutch.
According to the RGM info. the 'plain' plate supplied with the 050008 "5 Bronze plate conversion kit is HS0746 which is a standard thickness plate (2mm) and five 063741 3.2mm (standard 5-plate thickness) friction plates and standard 'thin' (5-plate) 063768 pressure plate.
Standard plain clutch plate 060746
The 5 plate clutch has 4 plain plates. The additional plain plate is for converting from '4 plate' (3 plain) to 5 plate (4 plain).
"The 050008 clutch kit is supplied with 5 new bronze plates and a new pressure plate and only one steel plate, the reason we only supply one steel plate is if you are replacing the fibre clutch plates you would already have 3 steel plates in that clutch arrangement and these can be reused with the bronze plate as long as they are flat and in good condition."
Hi Bill and Ken, have you weighed the modified stack using RGM friction plates against a standard 850 5 friction plate stack?
I'll have to measure the friction plates. It might be that I have the thicker ones. I did measure the thickness of the RGM steel plate, and it was thinner than the stock ones, but not by much. At the moment, the stack is high enough that I can't fit the snap ring, so I will have to do something to sort it.
When I ordered from RGM, I ordered two sets, one for my grandson's bike and one for mine. I don't recall seeing two thickness' listed, but that doesn't mean much. I'll go back and look at their listings again. It worked fine for my grandson's bike, but I did end up using a batch of stock plates that I had previously had surface ground thinner (trying to fit an extra friction plate in the stock basket), along with a modified pressure plate that I had previously machined for another experiment.
In any case, it should work fine once I get the stack height right.
I haven't done so, but I will, probably tonight. The RGM plates should be lighter than the stock bronze setup, but it will be interesting to see how much.
That's five plain plates and there should only be four.
i was not doing it to save weight as i run the surflex fiber plates which are a lot lighter than the bronze and don't have the spline wear issues of the barnetts. the sole reason is to increase the torque capacity of the clutch as the effective mean radius is increased.
I realize that, but the side-effect of reduced weight is still noteworthy. The effect would be even greater if the clutch basket was made of aluminum.
Weight reduction of rotating parts will not only improve acceleration but also improves responsiveness of the engine and saves energy.
i am already running a belt drive.
Quite right. I misspoke. I machined all four of the stock Commando plates, but only used three of them, plus the one from RGM, as well as the pressure plate that came with the kit.
I just measured the thickness of the friction plates, and they are .125" (3.18 mm).
After playing around with this clutch setup for a while, I've discovered that my basic problem is that the clutch pack is too tall for the clutch hub. The last friction plate does not engage fully with the center hub splines, even with one steel plate replaced with a thinner one (.065"). The center of the friction plate extends slightly above the end of the hub, even with the thinner plate. In addition, I would have to thin down the pressure plate just to get enough clearance to fit the diaphragm spring. The problem has to be with the clutch hub, because the RGM friction plates are the same thickness as the stock 850 bronze plates, so the overall stack height should be the same. I don't want to pull the primary apart again to shim the center hub further out, so my only solution is to find some thinner steel plates. I had a batch of stockers ground down to .065" a while back, but I only have one of them available. I'll see if Fred at Old Brits has any of his thinner ones left. If not, I'll probably have to have another batch done. Or, I could bite the bullet and tear it all down to fix the clutch hub. One way or another, I will get it sorted out.
For anyone who's interested, the measurement data I collected is included below.
Stock bronze friction plates, set of 5, weighs 2 lbs. 7.4 oz.
RGM bronze friction plates, set of 5, weighs 2 lbs. 3.8 oz.
Stock plates are only 3.6 oz. heavier for set of 5.
Steel carrier plate for bronze clutches is .065" thick for stock and .079" for RGM.
That explains why the stock plates are not much heavier than the RGM.
Stock steel clutch plates are .082" thick, while the RGM plate from their kit is .078" thick.
Not a big difference, but with 4 plates that adds up to a total pack difference of .016".
Both stock and RGM bronze plates are .1250" - .1255" thick.
The latest Barnett composite friction plate is .121" thick.
Stock steel plate weighs 6.3 oz.
Narrowed stock steel plate weights 3.4 oz.
The pressure plate supplied with the bronze plates is .1160" thick at the edge.
The stock 850 pressure plate is .1105" thick at the edge.
Good info there, my measurements of stock bronze and Barnett plates similar to yours and here are weights of O.E. Stock and Barnett clutch/primary chains on my modified setup.
Pressure plate, friction and steel plates:
O.E. steel pressure plate, 5x worn bronze plates, 4x steel plates (93.6mm i.d.)
Alloy pressure plate, 5x Barnett plates, 4x steel plates (machined to match Barnett plates 103mm i.d.)
O.E. triplex and Chainman duplex primary chains and Mk3 sprockets 57t-26t:
O.E. triplex chain and Mk3 sprockets
Chainman duplex chain and Mk3 sprockets (third row teeth ground off )
Clutch with primary chains and Mk3 sprockets:
O.E. clutch with triplex chain and sprockets
Barnett modified clutch with duplex chain and sprockets
1480g 3.25lbs (about 26%)
Triplex and Duplex chains and sprockets weighed as complete assemblies on the same scales, clutch parts added up from individual weights so above figures may vary slightly. If you see any obvious errors let me know and I,ll recheck.
I,ll weigh them as complete assemblies when I change over to the Duplex, great project by the way, don,t know where you get the energy to do all this plus the family and wildfire stuff.
“O.E. clutch with triplex chain and sprockets 5662g 12.45lbs”
Wow! Who needs a flywheel ?!
Great info, KiwiNeill and Ken.
plus diaphram and circlip, adjuster and nut 450g 1.0lb ±
I,ll double check all measurements once I get new parts on the bike, still using it daily at the mo.
Duplex assembly has a nice clean "mechanical" look about it, thanks to those who did the Chainman post, was non the wiser about his chains previously.
Looking at the Phil Pearson and NEB clutch baskets, there is a potential for saving another 1.5 kg / 3.3 lb or more by replacing the stock basket by one made of aluminum. This is another Mk. 3 part crying for a modern replacement (I am not considering a belt drive).
There is a method of modifying Norton clutches called the heinz-kegler servo clutch mod here-look at p12;