RGM pre-Commando belt clutch experiment for P11

Should be getting a pre-Commando belt drive kit from RGM dropped off on my porch soon. I'm going to see if I can get everything aligned and squeeze it in the P11 primary. The skinny 20mm belt the kit comes with might be pushing it for the grunt my motor makes, but gotta give it a shot. I suspect the kit belt will be too long as well. I know belt drives have been installed in a P11, but I can't find a post that specifically mentions the RGM pre-Commando kit and 20mm belt.

Is the Continental AT10 Gen III Synchroflex 8mm belt RGM uses regardless of width not up to the job? They are timing belts, not drive belts. I believe I read some "don't use that belt" complaining, but I'm not sure if the complainer ever used one on a 750 Norton.

Bring on the gloom and doom advice.

I know you know this, but Atlas/650 primary chain 76 links, P11/G15 68, so the belt might need a knot in it

I have more than 68 links in my P11 chain with the 22T engine sprocket I'm using. 69 and half or some odd ball number. Still nowhere near 76 links. But, yeah, the pre-Commando kit belt will be a throw away. I bought a shorter one as well. I wasn't getting any answers on making up a kit that would work on a P11 from Roger. He was helping initially and then got too busy to respond for a couple of weeks, so I just went ahead and ordered some things thinking he was done with talking about it. (Found out he is having staffing issues. Whatever that means.) The entire belt clutch could end up in a box on the shelf and I wouldn't care to be honest. Interesting what one gives a hoot about after 72 years on this spinning rock. If I were wallet hurt and didn't know how to live within my means, it would probably be upsetting. Fortunately, that is not the case.

Without modifying the inner primary and gearbox mount I can get the engine and gearbox shaft centers to 9 3/8" Not sure if the clutch basket would still fit in that little primary though with the shafts spread that far. Don't have the parts yet to check. I'm going ahead on the theory that I can get a belt of the correct length to get everything in there. Ron L did it, so it can be done.

I've calculated c-c diastance to 227.8 mm (8.972") based on use of simplex chain and standard gearing. I am able to match this distance pretty well when using the CNW belt kit and a 109*p belt rather the 112*p belt provided for the Commando. However, there is no 109*p belt available, so an idler needs to be accomodated. I am working on a solution.
(For the Commando, the 112*p belt matches the c-c distance prescribed by the triplex chain perfectly.)
As for the RGM kit, I haven't run through this exercise as yet.

- Knut

I run the same kit in my Atlas and 99 with no issues. If you end up not using the RGM supplied belt, please let me know.

Scott

Schwany said:

Is the Continental AT10 Gen III Synchroflex 8mm belt RGM uses regardless of width not up to the job? They are timing belts, not drive belts. I believe I read some "don't use that belt" complaining, but I'm not sure if the complainer ever used one on a 750 Norton.

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The belt drive developed by CNW utilises a 21mm belt and seems to work flawlessly. I think you will be fine with a 20mm belt width. I intend to use same width for my G15CS.

Continental AT10 Gen III Synchroflex has a pitch of 10 mm actually.

- Knut

Oops!!

AT10 kind of explains why I couldn't find a different length in 8mm pitch. lol

Good thing I bought the shorter AT10 890 from RGM instead of sourcing it elsewhere. I probably would have ended up with the wrong pitch.

The RGM parts arrived. UPS is quick from the UK (4 days to my door). It did not get hung up in customs like Royal Mail and DHL shipments do.

Unfortunately, and as more intelligent persons than I might have known, both the belts (980mm and 890mm) are too long. Several problems with what I got as well. Clutch rod I ordered is bent, the 980mm belt that was supposed to be 20mm width is 32mm wide, the engine pully is beat up on 4 of the teeth. I'm not sure yet if the drum is correct. The hub is correct for a pre-commando mainshaft, but the drum is 43mm wide. Seems wrong to me, but what do I know. The engine pulley and push rod I can blame on skimpy packaging and UPS throwing the box around like the Samsonite gorilla. The wrong belt is as far as I am concerned inexcusable for a clutch kit sold for specific model Nortons that specifies a 20mm belt. Couldn't somebody use a check list for farts sake. No cussing took place, just disappointment. Boo hoo

I have seen my fair share of light packaging damaging parts, often from UK vendors also. Hope they make it right for you. I have my eye on that RGM setup also, for my Mercury. Currently will be trying a unique quick change engine sprocket first. The P11 primary is more difficult for me to seal up, so I will be watching this thread closely to see if it works.

elefantrider said:

I have seen my fair share of light packaging damaging parts, often from UK vendors also. Hope they make it right for you. I have my eye on that RGM setup also, for my Mercury. Currently will be trying a unique quick change engine sprocket first. The P11 primary is more difficult for me to seal up, so I will be watching this thread closely to see if it works.

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If the shaft centers are far enough apart on the Mercury and the primary deep enough it would be a bolt on more or less. The shaft centers on a P11 or N15 are much closer together and the primary cover is a PITA to work with.

It'll be a while before I finish up. Lot of little tedious modifications to take care of. Plus that finding a blet that works thing. lol

I suggest anyone that wants to convert to a belt clutch in their P11 or N15 get or make up your own kit that uses an 8m pitch belt. There are many choices for easy to source 8m pitch belts with an adequate specification. AT10 with the right heat spec for inside a primary is for the most part not available in the USA. Plus I am starting to think the right length may not exist either. Still working on it, but could be an exercise in futility unless I can come up with an idler setup.

Schwany said:

I suggest anyone that wants to convert to a belt clutch in their P11 or N15 get or make up your own kit that uses an 8mm pitch belt. There are many choices for easy to source 8mm pitch belts with an adequate specification. ... Still working on it, but could be an exercise in futility unless I can come up with an idler setup.

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Many choices? You have Gates .... and Gates. See my post #4.

mdt-son said:

Many choices? You have Gates .... and Gates. See my post #4.

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I read your #4 post when you made it. I knew about Bolton and what they had before you posted. You did straighten me out on the 10m pitch.

Let me know what you find that actually works when you actually get a RGM belt drive installed in a P11 or N15. The 890 length is close but not close enough. I will probably end up ordering a Continental 20 AT10 880 Synchroflex belt from Bolton given nobody in the USA stocks them at a reasonable price. The next size down is a 840, which is too short. If the 880 doesn't work for me, I'll look at the cheaper off brand belts that probably won't last, nor come in a length I can use without an idler.

Fitting an idler in the primary is looking a little fiddly. You should do it and teach everybody how it was done.

I was able to get the whole shebang into the primary cases without a perimeter spacer. Many hours with a Dremel reshaping the area around the drum . Also modified the clutch drum basket or whatever your favorite term is for it. Pics tomorrow for anyone that gives a flying burrito.

Roll your own....... and carry spares!! (Apologies )

In the 50's it was said, always to bring a girlfriend with nylon stockings along in case the generator belt snapped. (At least in the VW Beetle community, this was a saying .... not much else would render you stranded in a Bettle, if you still had petrol in your tank!) However, my hunch tells me nylon stockings won't last long at the primary drive of a Norton/Matchless!

- Knut

Schwany said:

Fitting an idler in the primary is looking a little fiddly. You should do it and teach everybody how it was done.

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Yes, it is fiddly, but I will perform the design. Teaching anyone is not my desire though.

I have to order a new belt drive pulley and I'd prefer the steel one made by Hayward, unfortunately these are no longer available, which means I have to fabricate my own pulley or convert one designed for a Triumph.
It may take a while to get ready. I will do the math and CAD work in the meantime.

- Knut

More work to do, but this is where I am visually on the experiment.

The 890 belt works if set at the position in the last pic, but I would need a very fat spacer. The 880 belt should fit with some more Dremel work and a thick home made gasket. BTW, the Red Gen III Syncroflex belts have a higher tensile strength and temperature rating than many other AT10 belt offerings. This is why I say the choices are limited with an AT10 belt in a 20mm width and 880 length.







Image above is with the gearbox back far enough to use the 890 belt. Work was done on the inner primary as well, but can't be seen in this pic. I'll have the clutch off later to show what I did. Basically the same thing everyone else has done to get a belt drum inside the P11/N15 style primary case.

I probably have a few more hours of Dremeling and fit work. However, with the gearbox moved forward 1/4" it all fits inside the primary and spins without any interference using only the stock gasket AN sells. Unfortunately, because the belt is too long, the belt skips off a tooth on the engine pulley on the compression stroke when using the kick start. Not a good feeling on the kicker.

Other thing I did was increase the bevel depth on the outside edge of the drum. Hoping that doesn't come back to bite me in the arse when I install the spring and circlip and start using the clutch. The pressure from the spring could in a very worst case scenario bend the slot the spring circlip sits in out like a mushroom due to the reduction of material above the circlip slot. It would be a hell of a mess in there if that happened. Living on the edge.

Hi Schwany, with gearbox in the center position and no change to the clutch basket / drum nor to the outer cover, I guess there is some interference? That's what others have experienced.
How is the clearance of belt towards inner cover with this kit?
For the outer cover, one alternative (albeit a bit drastic) is to alter shape of the clutch dome by adopting a fabrication of the Commando's dome.

Pls. remember that by fitting a belt drive, a double gearbox adjustor is highly recommended; alternatively, a top bolt locking mechanism proposed by Ludwig and others recently may be used (look up his posting March 30th).

- Knut

Yeah I know about all the problems others have faced and how they corrected them.

Like I said above most of my alterations are the same or similar to what others have done.

The ridge around the hole for the mainshaft in the inner cover was reduced, but not to the point of being flush. Wasn't necessary to cut it down flush.

I will be taking a small amount of material off of the tops of the humps around the case fasteners below the drum.

With the gearbox in the center position there is no belt that I want to use that would work. It might fit centered, but it wasn't anything I was going to look into.

I won't be using dual Commando gearbox adjusters. I may use a tab lock arrangement in place of the washers. Remains to be seen.

I don't have plans to cut out the clutch dome in the outer case and learn how to Tig weld. That was one of the first things I thought of.