Request for advice concerning Belt Drive setup for an Atlas

Mike T

Mike T

Joined
Dec 30, 2012
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Hello guys,
I'd like to ask for your advice concerning fitting a belt drive to an Atlas with the standard alternator setup. I’m open to other setup suggestions. Please note that I'm going for a Manx-style cafe Racer look, so I'm not worried about anything that doesn't look standard Atlas!

I have a belt drive that came with my project bike called "Shep". I'd like to keep the belt drive, but the configuration of the new bike will be quite different to the Shep bike that I bought. It came with a G15 gearbox and G15 engine/gearbox plates and Commando inner & outer primary cases. However, I'm wanting to go to a more standard Atlas configuration. I've swapped the G15 gearbox for a standard Norton ‘NA’ gearbox and have dry fitted the gearbox into the standard Atlas engine plates.

The problem I have is that I don't know how the belt drive will work with a standard alternator setup. You'll see that once everyone is stacked up on the main shaft, it will be too 'tall' to fit inside the standard Atlas primary case.

Having said that, I'm not too concerned about having to use the inner and outer primary case; in fact I really like the naked look with perhaps a small mudguard-style cover for a little protection, so I'd be open to any cool and creative ideas.

Here’s a video which I hope explains more clearly..

Thanks for your help
Cheers,
Mike

[video]https://www.youtube.com/watch?v=CQ8s5GC10hQ[/video]
 
Re: Request for advice concerning Belt Drive setup for an At

I once fitted a Commando clutch with triple row chain inside an Atlas primary case. The triple row chain is about as wide as your belt, so it should be possible to stack everything in there.

I did this way back in the early '70's so I do not remember exactly how I did it. If I remember correctly, I had to put longer studs on the stator plate, and I used an early Commando rotor, and rotor nut.

It may be that I used the Commando stator plate as well. Just do not remember if so.

I do remember that the rotor outer face was flush with the end of the crankshaft, leaving no room to thread the Atlas rotor nut onto the crankshaft. The Commando rotor saved the day as it has a larger bore and the Command nut is long and fitted inside that larger bore.

I hope this helps.

Slick

PS .... I removed the Commando clutch and went back to the Atlas clutch because the Commando clutch does not have a cushion drive, neither does your belt clutch. Unless you convert to the Commando cush drive rear wheel hub, there is a risk of gear failure without any cushion in the drive line.
 
Re: Request for advice concerning Belt Drive setup for an At

Mike
I fitted a Bob Newby belt drive to my Dad's modified Model 50/ES2 a while ago
The 2 things that reduced how tall it was, as you call it, were:
1. machine the taper on the primary pull until it is very (1-2mm?) close to the crankcase
2: machine a recess in the alternator rotor too allow the end nut to sit flush with the outside of the rotor (had to cut a little into the magnets but not much)
I actually used a commando alloy primary case set and also had to grind a little off the inside of the outer case to create space for the stator windings
I'll have look to see if I've got any photos that might help.
Cheers
Rob
 
Re: Request for advice concerning Belt Drive setup for an At

Thank you Slick and Rob, appreciate your advice. I'll try the Commando primary setup. The bike came with a Commando setup so it's possible that it might still work, even though I've switched to the original Atlas plates and a Norton gearbox. Cheers, Mike
 
Re: Request for advice concerning Belt Drive setup for an At

@Mike T

I positively, absolutely remember that I had to do NO machine work to fit the Commando rotor and stator parts, and closed up the primary with the Atlas outer cover.

Slick
 
Re: Request for advice concerning Belt Drive setup for an At

One problem or shortcoming with the commando primary, at least for the single engine, is the shorter distance between pulleys meant there was no room for the centre stand spring to operate properly between the engine and gearbox.
If your bike has twin mono blocs (one chopped) this will be a real problem as it won't run on a sidestand - as the RH carb will starve
Cheers
Rob
 
Re: Request for advice concerning Belt Drive setup for an At

Hi Rob
Thanks for your comments. I'll take a look as soon as possible to see how things will fit together. I still have the tatty Commando inner primary case. I will also be running a single carb but will try to think about how this will look once it is mocked up. Cheers. Mike
 
Re: Request for advice concerning Belt Drive setup for an At

Mike
These pics may be of help
One point is that I had to make spacer tubes to hold the stator out further
Cheers
Rob

Request for advice concerning Belt Drive setup for an Atlas

Request for advice concerning Belt Drive setup for an Atlas

Request for advice concerning Belt Drive setup for an Atlas

Request for advice concerning Belt Drive setup for an Atlas

Request for advice concerning Belt Drive setup for an Atlas

Request for advice concerning Belt Drive setup for an Atlas
 
Re: Request for advice concerning Belt Drive setup for an At

Thanks very much Rob for posting your pics. I appreciate it. Wow, that is a nice looking setup you have. Cheers, Mike
 
Re: Request for advice concerning Belt Drive setup for an At

Hello guys
I tried dry-fitting the Commando inner primary case tonight and unfortunately it's too narrow to work with the Atlas engine/transmission plates and the Atlas gearbox. Here are a couple of pictures and I've also attached a short video below to illustrate. No problem, I'll keep thinking about the best option.
Cheers
Mike

Request for advice concerning Belt Drive setup for an Atlas


Request for advice concerning Belt Drive setup for an Atlas


[video]https://www.youtube.com/watch?v=OUfktQnDHIs[/video]
 
Re: Request for advice concerning Belt Drive setup for an At

When I fitted the Commando clutch to my Atlas, I used the Atlas inner and outer primary case. I also used the Commando triple row chain which is endless, and somehow I managed to get the crank and main GB shaft centers close enough to slip clutch basket and crank sprocket (joined by the triple row chain) on together. Your video shows you have used all the GB adjustment available, so I am at a loss to explain how I did it and you can not.

I have given more thought on how I fitted the stator and rotor, and went to my parts bin for verification. I most certainly used the Commando stator mounting plate, as this has the wide slot necessary to pass the triple row chain, or in your case, the wide belt. This plate moves the stator outboard, requiring the rotor move outboard by a similar amount. I used a spacer behind the rotor (between rotor and triple row sprocket) to hold the rotor off the required amount. This put the rotor outer face flush with the end of the crankshaft with no room to thread on the rotor nut. If I had retained the original Atlas rotor, It would have been necessary to machine a recess in the rotor face, as Rob did in the pics he posted. In my case, I substituted the Commando rotor and nut. The Command rotor is also flush with the crankshaft end, but the Commando nut threads on to the crankshaft INSIDE the rotor bore. If this is not clear, I can post a pic of the rotor and nut after the upcoming holiday (I am not with the parts now).

I hope this helps.

Slick
 
Re: Request for advice concerning Belt Drive setup for an At

If you you want stock and cafe racer with open cases just use a 428 O ring chain, cheap and doesnt need oil.

I have sold dozens to Manx owners and they last very well with some racers getting over a seasons use.

Your chain should be 76 links.

Andy
 
Re: Request for advice concerning Belt Drive setup for an At

Thank you Slick and Andy for your replies.. I will keep you posted. Happy Thanksgiving!
Cheers, Mike
 
Re: Request for advice concerning Belt Drive setup for an At

I was going to mention CLUBMAN'S RACING but you beat me to it. I am involved in the same project as you. Clubmans offers longer stator studs. I then made a spacer to fit over the foot peg bracket inside the case so it would hold the outer primary even instead of tilted. It works alright but I believe the outer tin cover is pressing against the stator and new foot peg spacer. However, it holds well and is quite usable. For project #2...CR makes a new belt drive with a 20MM belt and pulley which solves the problem.
 
Re: Request for advice concerning Belt Drive setup for an At

Thank you guys. I'm still working on the engine at the moment but will post again once I resume work on this. Cheers, Mike
 
Re: Request for advice concerning Belt Drive setup for an At

Not the cheapest option but the Bob Newby Racing clutch and beltdrive kit for Dommies goes directly on without fuss.
Changing from the stock primary over to the Newby took a couple of hours ( including fitment of Dynodave trans seal), then it was road test time.
No machining required.
Works great, fixed the leaky primary cover problem and the slipping clutch problem plus trimmed off about five or six pounds of rotating weight hanging on the end of the trans mainshaft.

Glen
 
texasSlick said:
Re: Request for advice concerning Belt Drive setup for an At

I once fitted a Commando clutch with triple row chain inside an Atlas primary case. The triple row chain is about as wide as your belt, so it should be possible to stack everything in there.

I did this way back in the early '70's so I do not remember exactly how I did it. If I remember correctly, I had to put longer studs on the stator plate, and I used an early Commando rotor, and rotor nut.

It may be that I used the Commando stator plate as well. Just do not remember if so.

I do remember that the rotor outer face was flush with the end of the crankshaft, leaving no room to thread the Atlas rotor nut onto the crankshaft. The Commando rotor saved the day as it has a larger bore and the Command nut is long and fitted inside that larger bore.

I hope this helps.

Slick

PS .... I removed the Commando clutch and went back to the Atlas clutch because the Commando clutch does not have a cushion drive, neither does your belt clutch. Unless you convert to the Commando cush drive rear wheel hub, there is a risk of gear failure without any cushion in the drive line.
Click to expand...
 
texasSlick said:
Re: Request for advice concerning Belt Drive setup for an At

I once fitted a Commando clutch with triple row chain inside an Atlas primary case. The triple row chain is about as wide as your belt, so it should be possible to stack everything in there.

I did this way back in the early '70's so I do not remember exactly how I did it. If I remember correctly, I had to put longer studs on the stator plate, and I used an early Commando rotor, and rotor nut.

It may be that I used the Commando stator plate as well. Just do not remember if so.

I do remember that the rotor outer face was flush with the end of the crankshaft, leaving no room to thread the Atlas rotor nut onto the crankshaft. The Commando rotor saved the day as it has a larger bore and the Command nut is long and fitted inside that larger bore.

I hope this helps.

Slick

PS .... I removed the Commando clutch and went back to the Atlas clutch because the Commando clutch does not have a cushion drive, neither does your belt clutch. Unless you convert to the Commando cush drive rear wheel hub, there is a risk of gear failure without any cushion in the drive line.
Click to expand...
What are the problems converting to a Commando cush drive rear wheel?
 
As long as you lace it with the correct Atlas offset , no problem, I had done it and you fit the Atlas hub cover with the three holes and nobody knows, but you !
 
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