Drive belts

[storm42]

Are Gates drive belts sensitive to heat ? I have stripped the teeth off mine today and it is the second belt I have done on this bike.

The belt runs true with no run out on the pulleys and it was neither overly tight or loose, the case is as dry as a Commando case can be but it is sealed, I have seen some nice case plugs that seem to have a gauze in them, presumably to allow air in the case, is that necessary?

I was as comprehensive tooth strip as I have seen and left me stranded in Derbyshire and waiting for my mate to bring my van out to me.

There are worse places to be stranded whilst waiting for a van though.

 

[Bernhard]

What type of Bates belt?
Kevlar reinforced?

 

[storm42]

Gates Powergrip HTD, the same belt I use on the race bike, although that is 40mm wide not 30mm like the above. I guess I should ask the supplier when they open on Monday although they did know what it was being used for when they supplied the belt for the race bike.

 

[storm42]

Just found some spec on the belt and they say it has fiberglass tensile member, I don't see that as a problem though as the teeth have separated from the belt which is still in one piece.

 

[Chris]

Hi Ralph
Run these belts on most of my bikes. 40mm on the racers. All have open primarys. I have 30mm belts on the Tritons. Never lost teeth like that?
Bob Newby swapped the belt on my 8 valve for another as it whistled like a kettle. Slightly different profile on the teeth?

 

[storm42]

Hi Chris, I have 40mm on the racer and the last time i looked at it was fine, also running in the open. I have been trying to remember when I fitted this belt, I know I ruined the previous one at Cadwell at the Beezumph and I reckon it must have been 5 or 6 years ago, so it has probably done 2 or 3 years on tracks and a couple on the road, not big miles but mostly as fast as it would go, I am not so worried about fitting another now but will probably vent the case.
It was strange when it went this time, I had just passed a car and shortly after I thought the clutch was slipping, not for long though, as it coasted to a halt only to be passed by the car, I am sure they were laughing.

Have you got your entries in for Pembrey?

 

[Fast Eddie]

Are you sure it’s the right spec material etc Ralph? I often think that buying belts from bearing suppliers etc is fraught with danger. A belt designed to power a conveyor at the supermarket check out might struggle with hot snot Norton primary drive ....

 

[ludwig]

I believe this is caused by a too loose belt.
If you stick to Gates, go for GT3 belts:

But I'm afraid 912 length is not available in GT3 quality.
( at least it wasn't till last year..)
Optibelt and Continental also make stronger belts in 912 mm.

Side note : tie your stator cable to the stator stud.

 

[storm42]

Are you sure it’s the right spec material etc Ralph? I often think that buying belts from bearing suppliers etc is fraught with danger. A belt designed to power a conveyor at the supermarket check out might struggle with hot snot Norton primary drive ....

Yep couldn't agree more, and I know sod all about belts. Yesterday morning I was looking at a CNW electric start and noticed the 21mm belt, I wondered if it was specialy made for CNW to cope, so I looked for the spec and found this

When designing Poly Chain GT Carbon belt drives to be used in low-speed applications (generally 500 rpm and less), traditional drive design procedures may yield drives with greater-than-needed capacity. These design load calculations are intended primarily for applications on the output side of gear reducers, and will yield Poly Chain GT Carbon belt drives competitive in both cost and performance with roller chain and superior to other belt drives.

I don't think any of these belts are designed for what we use them for and the more I read, none of them are designed for high rev situations. Also they are rated with electric motors not pulsing twin cylinder motors. I suppose most things in life are a compromise, some more than others.

 

[storm42]

I believe this is caused by a too loose belt.
If you stick to Gates, go for GT3 belts:

But I'm afraid 912 length is not available in GT3 quality.
( at least it wasn't till last year..)
Optibelt and Continental also make stronger belts in 912 mm.

Side note : tie your stator cable to the stator stud.

It doesn't look like the size is available. Good point re: the cable.

 

[Matchless]

I had this happen on my 920. I think what caused it was the Norvil clutch & engine pulleys had become worn & rough which started to eat the belt. The problem lay with poor quality anodising. Often the so called hard anodising is no such thing because if it were you would not be able to scratch it with a scriber, which in the case of the Norvil parts I could.

Martyn.

 

[storm42]

Mine is a Norvil

 

[Nortoniggy]

I have a Norvil belt drive in a closed primary case and thankfully had no problems with it. I use the same type of belt as yours and did replace the first belt after many years just as a precaution as the old one still looked fine. I kept it as a spare. I bought my replacement belt from a bearing supplier which is identical to the Norvil one. Gates are not going to make different qualities, and/or strengths, of belt without them being marked differently so can't see any problem with buying one from a bearing place if it's labelled the same. Where do you think Norvil buy theirs?

Ian

 

[1up3down]

I run a Norvil 30mm belt, last one before replacement lasted over 20,000 miles.
I have long believed primary belts are set too loose which causes the bottom
to slap the primary and promote early teeth wear upon pickup on the clutch side.
The standard advice is to set the belt when cold so there is a 90 degree twist
in the upper middle of the belt, too loose, it should be set at around 55 degrees.
This can be verified when the primary is hot and the belt is at its tightest.

 

[Fast Eddie]

Ralph, Steve Maney still had kits in stock when I spoke to him recently. Not expensive either.

 

[storm42]

Ralph, Steve Maney still had kits in stock when I spoke to him recently. Not expensive either.

I don't think there is anything wrong with the Norvil kit, but I might give Steve a bell tomorrow (if he is back from Thailand), be rude not to and I think I could make use of the Norvil kit on my ES2.

 

[storm42]

I have a Norvil belt drive in a closed primary case and thankfully had no problems with it. I use the same type of belt as yours and did replace the first belt after many years just as a precaution as the old one still looked fine. I kept it as a spare. I bought my replacement belt from a bearing supplier which is identical to the Norvil one. Gates are not going to make different qualities, and/or strengths, of belt without them being marked differently so can't see any problem with buying one from a bearing place if it's labelled the same. Where do you think Norvil buy theirs?

Ian

No problem buying from bearing places, in fact the place I get mine from will cut them to width, I think the point I was trying to make was that none of the belts are made with our purpose in mind.

 

[storm42]

I run a Norvil 30mm belt, last one before replacement lasted over 20,000 miles.
I have long believed primary belts are set too loose which causes the bottom
to slap the primary and promote early teeth wear upon pickup on the clutch side.
The standard advice is to set the belt when cold so there is a 90 degree twist
in the upper middle of the belt, too loose, it should be set at around 55 degrees.
This can be verified when the primary is hot and the belt is at its tightest.

I think my picture shows my belt hasn't been touching anything, so not too loose, and I do check the slack when everything is hot, but that does tend to be the last it gets any attention.

I think it is too easy to have a one size fits all attitude to belts and forget that they can have considerably differing lives with different people and use. The belt that failed on me this time was only used on track for it first 3 years of use, so between 5 to 7000rpm every time the bike ran, then I punched the motor out to 920cc with a stage 2 Maney head and cam and then abused it on the road for a couple of years.

After I asked the question about heat, I had a think about the age of the belt and the use it has had, and then read about the belts design and use criteria and thought I should have changed it last year as a precaution, we live and learn.

 

[lcrken]

Gates Powergrip HTD, the same belt I use on the race bike, although that is 40mm wide not 30mm like the above. I guess I should ask the supplier when they open on Monday although they did know what it was being used for when they supplied the belt for the race bike.

My experiences with the same Gates Powergrip HTD belts on race bikes is that the 920 works with the 40 mm belt, but not with the 30 mm belt. I have used the BNR drives on 920s for a long time now, and have had great luck with them. Back in the late '80s I tried switching to a different brand drive with a 30 mm belt (and a smaller front pulley), and almost immediately stripped the teeth off the belt.

That brings up the question of what primary drive ratio you are using. I've always used the 1.75 ratio drives, which use larger front pulleys. It looks like you are using a smaller front pulley to accommodate the stock alternator. If so, that is almost certainly contributing to the problem.

So far I've only used the original HTD belts, as well as the Optibelt Omega, and a few other brands. I haven't tried the GT3 that Ludwig mentioned, but they sound like a better choice. Gates also now lists the Powergrip GT4 s their latest and greatest GT tooth form belt, so maybe that should now be the go-to choice. Besides, I wasn't having any problems with the HTD belts. But next time I need belts, I'll look into the GT4.

The really hot new belt seems to be the Gates Poly Chain GT Carbon, but Gates says it is not compatible with the HTD pulleys, and I haven't seen anyone except CNW come out with a belt drive kit for Nortons that uses it.

Something to think about, anyway.

Ken

 

[Brooking 850]

I use Optibelts on my bikes 40 mm on the race bike and 30 mm on the Roadster.
Great life and durable . I dont have a vented primary cover on the Roadster and it stands up to all seasonal conditions here in New Zealand.

The specs for the Optibelts indicate that one of these is used for a constant speed drive (like electric motors running running at a constant speed )and the other for high torque drives with variable torque changes like our bikes.