Primary belt phenomenon

robs ss · Mar 30, 2023

Don't worry, don't worry - I think I'll get over it!

SteveA · Mar 31, 2023

Remember that Ludwig's 0.5mm adjustment really is (very) fine-tuning. And fine if you can get sufficient grip with the retaining bolt so that it cannot slacken off, which you should be able to.

And I would hope that would be 100% fine on a road bike. On a race bike, if something can come loose, it will. The nut on mine is a nyloc!

But, too much slotting sort of defeats the object, road or race!

Flatspot · Mar 31, 2023

I just adjusted my belt primary with CNW electric start last week. My approach was to remove the belt casing, 3 footrest bolts 1 centre nut, 45 seconds. Then as the oil tank is dry I popped off the 2 supply/return hoses and that gave me access to the adjuster. I slackened off the 2 main gearbox bolts a touch, then the 2 nuts on the adjuster. I then adjusted the belt by tightening the front nut first and then the rear until both were solid. Then tightened the 2 main bolts, replaced the oil hoses, and then the chaincase. It really took no time at all, apart from when I lost my socket for 20 minutes as it was stuck to my magnetic hand lamp

mdt-son · Mar 31, 2023

robs ss said:
You have a cNw E-start and a LH gearbox adjuster?

I don't know about the e-start kit, but the CnW belt drive kit has no left side adjuster, for some reason. I consider twin adjusters a necessity.

cNw Belt Drive Kit

Complete drive kit with front sprocket, belt guards, rear sprocket, sealed bearing, extra clutch steel plate and belt One ratio available. 32 front and 70 rear offering a 2.188 gear ratio (std chain drive is a 2.19 ratio) Uses a Gates 21mm Poly Carbon belt. Stronger than what is used in other...

coloradonortonworks.net

- Knut

baz · Mar 31, 2023

mdt-son said:
I don't know about the e-start kit, but the CnW belt drive kit has no left side adjuster, for some reason. I consider twin adjusters a necessity.

cNw Belt Drive Kit

Complete drive kit with front sprocket, belt guards, rear sprocket, sealed bearing, extra clutch steel plate and belt One ratio available. 32 front and 70 rear offering a 2.188 gear ratio (std chain drive is a 2.19 ratio) Uses a Gates 21mm Poly Carbon belt. Stronger than what is used in other...

coloradonortonworks.net

- Knut

Could it be the width of the CNW belt only being 21mm
Less tendency to crab ?

ludwig · Mar 31, 2023

SteveA said:
But, too much slotting sort of defeats the object, road or race!

The slot is at a 60° angle against the arc the box moves in.
There is no risk it will slide for or aft.

mdt-son · Mar 31, 2023

baz said:
Could it be the width of the CNW belt only being 21mm
Less tendency to crab ?

Misalignment of the gearbox is caused by the transmitted torques, causing belt and chain pulling forces. As has been mentioned before, the final drive pulling force is much larger than that of the primary drive.
The gearbox tries to rotate along the vertical axis and bends the thin left engine plate in the process, subsequently causing heavy wear on belt and pulley.

The Commando set-up using a RHS adjuster only is completely inadequate for a belt drive as well as a chain drive. The adjuster clearly belongs on the LHS.
Alternatively, NV could have made a cradle featuring a fixed gearbox position (as per Mk3) and a chain tensioner slipper inside the primary chaincase, as HD and Triumph did.
Similarly, a belt drive needs a belt tensioner if a fixed position gearbox is used. Due to space constraints, a small idler pulley carried by an excentric bolt is suggested.

- Knut

SteveA · Mar 31, 2023

ludwig said:
The slot is at a 60° angle against the arc the box moves in.
There is no risk it will slide for or aft.

I didn't mean to suggest that I saw an issue with your solution. I rather thought the drawing offered in response was what I would have once called 'requirements creep'.

Jdub · Mar 31, 2023

This is what I found in my Mk2 with a Mk3 cradle.

baz · Mar 31, 2023

Jdub said:
This is what I found in my Mk2 with a Mk3 cradle.

View attachment 105316

Not a bad conversion I'd say

concours · Apr 1, 2023

ludwig said:
The slot is at a 60° angle against the arc the box moves in.
There is no risk it will slide for or aft.

Brilliant!

robs ss · Apr 3, 2023

Ive decided to go for a fixed stud in the cradle and make plate(s) to suit my needs.
First pass, made from plastic, below - this one gives 5mm adjustment (50mm c/c top, 45mm c/c bottom)
The big (32mm) hole is because that is the OD of the "nut" that Matt has put on the LHS.

If I get the adjustment numbers a bit wrong I can always fix it with a new plate - probably made from 4mm ss.
That way I only have to drill/tap one hole in the cradle.

BTW - I only intend putting one of these lock-plates on the LHS. That's where the load from the rear chain is. I will leave the RHS adjuster as is.
Cheers