commando clutch in a P11

Is it possible to change out the P11 mainshaft with a Commando and then run the Commando clutch? Will it fit under the P11 primary cover?

No.

The AMC primary case is designed for the single row primary chain. There is very little clearance between the chain and the case.

I have run the Cdo clutch in my Atlas with no clearance problems. I'm not saying the same will be the case with the P11 primary cases. I went to the Cdo clutch to get away from the heavy pull of the AMC clutch, but after 15K miles, went back to the AMC clutch. The heavy pull can be reduced about 25% by using a Venhill Teflon lined clutch cable, and it is now manageable.

I liked the Cdo clutch for its light pull, but the increased weight over the AMC gave my Atlas a flywheel effect that I did not especially like. Then, after the friction plates wore thin, I ended up fighting the three demons of the Cdo clutch .... lever pull, slippage, and dragging. Get two of them right, and the third bites you.

Another factor to consider if you contemplate change to the Cdo clutch - there is no shock absorber cushion in the Cdo clutch. The first Norton Cdos were breaking gears until Norton remedied the problem by putting the cushion in the rear hub.

BTW ... it is possible to use the Cdo clutch without changing the primary shaft. There is a center body available that has a modification to allow cinching up the clutch without the circlip on the shaft.

Slick

The tin primary on an Atlas/Dommie is different from the alloy primary on the AMC bikes. I imagine one could put a filler between the two halves to give more chain room, but then one would have alternator issues, as the stator mounts in the outer primary. I don't know if you'd have a good match-up between the rotor and stator if you bumped the outer cover out, say a 1/2 inch to clear the chain.

It's hard enough to ensure clearance between stator and rotor as it is.

BillT said:

The tin primary on an Atlas/Dommie is different from the alloy primary on the AMC bikes. I imagine one could put a filler between the two halves to give more chain room, but then one would have alternator issues, as the stator mounts in the outer primary. I don't know if you'd have a good match-up between the rotor and stator if you bumped the outer cover out, say a 1/2 inch to clear the chain.

It's hard enough to ensure clearance between stator and rotor as it is.

Click to expand...

BillT makes a good point regarding the rotor and stator. The Cdo stator stands off the inner cover by about 3/8 inch extra. I had to use 3/8 inch spacers to align the stator with the rotor, which also stands off by an extra 3/8 inch. Then, I had to substitute the Cdo rotor and Cdo rotor nut. This arrangement may not be possible in the P11 with the stator mount in the outer cover.

When I made my conversion, I had planned to change the inner and outer primary covers to the Cdo, to get away from the tin ware leaks of the Atlas covers. I never did the cover change due to the foot peg mounting problem. However, with enough $Franklins, that problem can be solved. It may be more cost effective to change to the Cdo primary covers as well, solving the clearance issues.

Slick

It always scares me to put on the outer primary case containing the stator and HOPE it maintains its clearance to the rotor. I forgot about the cush drive problem. Who supplies the magic piece that allows a Commando clutch on an Atlas shaft?

seattle##gs said:

It always scares me to put on the outer primary case containing the stator and HOPE it maintains its clearance to the rotor. I forgot about the cush drive problem. Who supplies the magic piece that allows a Commando clutch on an Atlas shaft?

Click to expand...

http://www.clubmanracing.com/beltdrivesnorton.php

BTW ... I ran my Cdo clutch WITHOUT any Cush drive for 15K miles, but my days of stoplight racing were over by then, and I was not hard on the shifts. Nevertheless, concern for the gears was the principal reason I converted back. Hope it goes well for you.

Slick

Wonder if a 20 mm wide DRY running Gates Polychain Carbon belt would fit?? If it did you could then fit a correctly hard anodised aluminium alloy clutch basket Commando type clutch fitted with an early 75 thou thick diaphragm spring which if correctly set up will give nice easy all day long two fingers max clutch lever operation.....thus ending up with a clutch that possesses all the qualities a motor cycle gearbox mounted multiplate friction clutch is suppossed to possess rather than those the manufacturers gave us!! For example a clutch that will free off instantly without drag whenever required even when hot, that will not slip when fully engaged even wnhen hot, that is easily operated by the rider at all times and lastly one that possesses the LIGHTEST rotating weight reasonably possible rather than the heaviest.
To fit such to your P11 woulds not require a main shaft change but simply a modification to the Commando clutch centre.
Trouble is I cannot think of any belt system maker manufacturing systems for sale to the public who knows anything about how diaphragm springs actually work and how to set trhem up correctly let alone the differences in the 4 versions of diaphragm spring fitted to Commandos......well I do know one that does but he does not sell direct to the public and if much toooo busy to even consider playing with such things.
I have,just for the hell of it, phoned a friend with a P11 along with enougfh bits to build another and asked him to take a few measurements just in case it looks possible because it might raise his interest and might prove an interesting project to keep me amused and brain active for while. I have also just tried phoning a friend in the USA to ask if he has ever manufactured a P11 belt system...he has been manufacturing primary and secondary belt systems for old British bikes since the 1970s so he may of done so. He was not answering eith his workshop or home phone so must be at church praying for someone competent to vote for as their next President !
For those twho are unaware, like one so called expert British belt system maker who once told a friend at a Stafford show that he could see no advantage to the diaphragm spring clutch..... The P11 clutch employs 3 coil springs applying a clamp load to the plates of approx 250 lbf. To start to free it off the user has to apply to the clutch push rod approx 250 lbf and with the clutch lever back to the bar approx 300 lbf. The ORIGINAL Commando clutch applied a clamp load to the plates of approx 380 lbf but because of the way the diaphragm spring works it only requires a load of approx 210 lbf at the pushrod to start to free off the clutch and with the clutch lever back to the bar approx 130 lbf. Personally I consider this to be an advantage........Of course if you fit a later stronger version of the diaphragm spring as fitted to the 820 Commandos the initial release load is approx 300 lbf and with the lever back to the bar it is approx 250 lbf......but the clamp load has risen to approx 550 lbf so if you actually run an 820 Commando clutch DRY you can happily shove an extra engine in the frame and go sprinting pretty certain that the clutch will not slip when fully engaged....bung some oil in it however and as as sure as God made little apples it will ..........

Friend with P11 played with measuring sticks last night has just phoed stating that he felt a 20mm wide Gates 8mm pitch Carbon belt would fit without a problem. As to whether the belt system would allow the alternator to still fit or whether a 4 friction plate Commando clutch would ............ Personally I had hoped my days of designing and manufacturing belt drive systems FOR FRIENDS ONLY were nearly over.......... I will try very hard NO to take on a new little project especially as the friend (ex drawing office) who plays with autocad for me has not touched it for many months and has a problem remembering what titty to press to get things to work correctly!! I will have a chat with Bob Oswald inthe USA shortly to see if he has ever done a P11 preimary belt system ........

Having just talked with a Gentleman in the USA who has been manufacturing dry running belt drive systems for British motor cycles since the 1970s I am informed that he has sold a few P11 systems over the years. The systems employ a dry running belt of 20mm width and a 4 friction plate diaphragm spring clutch which IF correctly set up with the correct diaphragm spring will give a very easily operated with no more than two fingers all day long clutch lever action....along with no clutch slip or drag problems.

And he would be where?

Mark in SC

@JM Leadbeater

OldForge said:

And he would be where?

Mark in SC

Click to expand...

And does his clutch have a cush drive?

Slick

great info. What the world needs is a good diaphragm spring clutch to retrofit into Triumph, BSA, and pre commando Nortons. I really like the light spring pressure possible from the Commando clutch.
Did not realize there were two different diaphragm plates for Norton. Would the lighter 750 plate work in a MK3 that is ridden as a sunday bike?

Two different plates? Do you mean diaphragm springs or pressure plates?
There were two different thickness pressure plates The 6mm thick version being for the 5 friction plate later clutch and the 9mm thick version for the earlier 4 friction plate clutch. Both set the deflection point of the diaphragm spring at the same point. IF you alter the deflection point of the spring in any way you alter the load the spring applies to the clutch plates and thus you alter the torque the clutch will transmit before slip occurs...not that the average Commando owner is aware of such facts......
There were 4 different versions of diaphragm spring fitted to Commandos whilst in production. They were prodeuced by Laycock Engineering of Sheffield to Laycock drawing No 83466 with the ref 10 and 20 being the two different springs used for the earlier Villiers Starmaker single and twin friction plate clutches and the Ref 30/40/50/60 on Commandos with the different yet again Ref 70 spring being the one fitted to the production rotary Norton clutches. The ORIGINAL Commando spring applied a clamp load to the plates of approx 380 lbf and required approx 210 lbf to start to free it off and with the lever back to the bar around 130 lbf giving an easy two finger clutch lever operation. The last version of spring, fitted to the later Commandos, gave a clamp load top the clutch plates of around 550 lbf and required approx 300 lbf to start to free off the clutch and with the clutch lever back to the bar approx 250 lbf. A Atlas and T140 for example had coil springs applying approx 250 lbf t6o the plates and required approx 250 lbf to start to free off and around 300 lbf with the clutch lever back to the bar. There are, apparently, people in this World who do not realise the benifits a diaphragm spring clutch CAN give!!
Triumph and BSA etc etc diaphragm spring clutch belt drive systems have been manufactured and available since the early 1980s from Quiet Power Drives in the USA. Take a loook at thierweb site Triumph video showing the QPD electric start system at work on a T140......infinitely simpler than other starter systems but requires someone with aq brain and mechanical Engineering skills to fit CORRECTLY!! Note the rear belt system which of course have been available for decades from QPD....... As to whether Bob Oswald of QPD is still alive I have no idea because he does not answer the phone when I phone trying to get info on the friction material Barnett fit to the friction plates they make for him ....as far as i can make out they fit a friction material only suitable for clutches designed to be employed in oil and as every Norton owner should know Norton clutches were designed to be employed dry if they are not to slip with a bit of torque being shoved through them and Bob Oswalds belt drive systems run the clutches DRY which is how ALL belts were designed to be employed.....not that some motor cycle AT10 belt system makers have ever bothered to talk to the belt manufacturers to determine such FACTS as some of us have....... Doesnt British Cycle Supply advertise Tony Hayward belt systems as designed to be used with oil or something? They certainly used to do so. Pahaps someone complained tothe Canadian Advertising Standards Authority as some rotten ********** did to the UK authority a few years ago about the Tony Hayward adverts . You dont believe adverts do you??
Newver seen the load /deflection curve for a Commando diaphragm spring? Send me your e mail address and I will send one....

in general, I have found that the lever ratio or drill pattern on the Amal clutch lever to be the major cause of early clutch pull issues.
This the 7/8", 1", 1-1/16, or others ............and you need the OEM 7/8".
TFE cable liner is excellent.
correct clutch lifting cam is important.
In the end, it does require period hand strength to use the clutch with ease.

p400 said:

in general, I have found that the lever ratio or drill pattern on the Amal clutch lever to be the major cause of early clutch pull issues.
This the 7/8", 1", 1-1/16, or others ............and you need the OEM 7/8".
TFE cable liner is excellent.
correct clutch lifting cam is important.
In the end, it does require period hand strength to use the clutch with ease.

Click to expand...

All true. Consider the following as more help.

The pivot hole in the lever tends to "wallow" out, causing binding and excessive play. I drilled out mine to accept a bronze bushing (5/16 OD X 3/16 ID if memory serves correctly).

I installed Barnett plates, using Ford type F ATF, and with the Venhill Teflon cable. I figured since ATF gives more friction than oil, and Barnett plates are intended to be run in oil, then I could back off on the clutch spring nuts about 1/2 turn from flush with studs.

The result is a manageable clutch pull. Still a four finger, but not the wrist wrenching "bear" pull of the original.
So far, no slip.

Slick

p400 mentions 'period' grunt to operate the clutch. The FIRST time I operated the clutch lever on an early 750 commando I turned to the owner and said...' OK so who is the clever ******* who has disconnected the ******* clutch?' The owner replied 'Funny but most people ask that question'. One early Commando road tesat (Motor Cycle Sport ???) said something like ...I find it incredable that such a delightfully light and posiotive clutch could of been ignored by motor cycle manufacturers for so long before being introduced on the Commando'.
The ORIGINAL 0.075 inch thick diaphragm spring applied a clamp load of approx 380 lbforce to the friction interfaces and required appropx 210 lbf to start to free it off and to hold the clutch lever back to the bar approx 130 lbf giving a clutch lever EASILY operated all day long with two fingers. the reason for later Commandos having heavy clutch lever action is simply because NVT had the spring manufacturer increase the spring thickness to increase the clamp load in a FAILED effort to reduce the clutch slip problem which is due to oil entering a clutch that like earlier Dommy clutches was designed to be run dry anbd NOT with oil on the friction intewrfaces. Thew last version of spring employed gave a clamp load of approx 550 lbf and required approx 300 lbf to start to free it off and approx 250 lbf to hold the lever back to the bar giving a rediculously heavy lever action.
The AMC clutch was designed to employ a lever with 7/8 inch between pivot point and centre of cable nipple. Fit say a lever of 1 1/16 inch centres and all you do is increase the lift way beyond that required for good freeing off and make clutch lever action heavier...its simple mechanics... Unfortunately when employing the same AMC lift mechanism for the original Commando clutch it did NOT give the required plate seperation for good drag free freeing off (due to the desig of the diaphragm spring clutch) so they changed the lever to 1 1/16 to icrease te lift. They also cxhanged the clutch operating lever in the gearbox so it cleared the inside of the gearbox outer case at the increased lift point.... but the Commando was LET US NOT FORGET only a two year production model to keep cash flow flowing into AMC while new models were developed and put into production so bidgery was the order of the day......
I did hear yesterday that Mr Negus is rebuilding one of those 800cc double overhead cam motors that AMC were developing / playing with ... where it came from I have no idea as I can only remember ever seeing one parked / abandoned outside the AMC factory and I thought that was bought by a Suffolk garage owner along with lots of the drawings when AMC went arse over tit and that was the one rebuilt and shoved in the National Motorcycle Museum.....but I could be wrong....