Belt fitting

[Crazymanneil]

Dagnabbit. Fitting belt and ran into a snafu. Perhaps someone has experience here.

The belt I have (8mm pitch round tooth HTD profile) fits on my engine pulley just lovely. Sets on nice and easy and seems pretty snug. I wish the same could be said for the gearbox (clutch) pulley. The belt fits on the first 10 or 20 teeth ok but then seems to lose sync with the teeth. It seems as though the pulley teeth are just slightly wider than the belt, meaning the belt will just about fit more teeth if it is persuaded.

So, is this normal for a toothed belt? Do I just need to set the pulleys up and put loads of tension on them to keep the belt in the teeth of the clutch pulley? Or am I missing something? Does the belt/pulley need to be returned? The BDL clutch says its 8mm pitch which checks out ok with my digital calipers as far as I can see.

Both are pretty decent brands. Belt is contitech and clutch is BDL.

Cheers,

N

[andrewaust]

Hey Neil !


That doesn't seem right mate, now in saying that I am no expert in toothed belts on bikes, more experience with blowers and timing belts etc.

Sounds to me like the pitch of the teeth on the clutch side is slightly larger, I could see the belt prematurely eating itself to death. I'm to the understanding belts are like gear teeth, they need near perfect syc to be reliable.

I'd love to grab a complete belt set for the Enfield and do away with the primary chains etc. It also could do with better clutch.

Hopefully someone can offer you a definite answer.



A

[toad]

crazy
i want to say my only experience is with harleys.. to me if all your belt and pulley measurements are right i would say to put it on and tighten it up. on harleys i run a little loose at first till it gets the break in over with. usually about 3/4 of an inch. after break in around 3/8 to a 1/2 inch. that will be measuring from pulley to pulley. toothed belts have quite a different look than a chain or v belt.

if your using a standard harley oem clutch bearing, not of the highest design effort. it works and has for many years.. to me when your looking at it looks like it may be missing rollers, kind of staggered.. but there are better bearings.. the reason being, the better bearing you can run your belt a little tighter.. does your belt have any recommendations? i think there are different settings for an tensioner and non-tensioner set up.

ps
i had one on my harley, i tried my best to get it to fail. it just kept going and going..lol
after breakin i never touched it again. i checked it a few times but didn't do anything to it..
3000 rpm and dump the clutch stresses it all pretty hard...

t

[Crazymanneil]

hmm thanks for the replies. not convinced the setup is ok. if i run the belt any way loose it will lose sync with the clutch pulley and eventually miss teeth. not sure if belt maybe stretches slightly on breakin.

i'm not using standard backing plate etc, have to make a bearing carrier for gearbox and engine.

are bdl belts any different from a standard 8mm htd belt from another manufacturer? seems to it my front pulley much better...

n

[toad]

the belt will stretch a bit, but the surfaces of the belt and pulley kind of mate to each other. the ones i have seen have a cloth looking lining on the inside of the belt. most have a coating on the pulley that will ware down. after break in all these surfaces smooth out and give a more complete contact. a new belt is quite stiff, after the break in it will be quite a bit more flexible.

if your wrapping the belt all the way around the pulley you might see a little mis-alignment on the contact surfaces. when fully setup you will only get about 60% contact with the pulley.

i have also never took parts from different sources.. my experience is with a package that came with both pulleys and belt.. i would think a 8 mm belt should work with any 8 mm pulley. the tooth design is an industry standard, ie 6 mm, 8 mm, 11 mm, 14 mm and so on..

t

[andrewaust]

Neil, I would get an accurate tape measure and try measuring the small pulley first, counting all teeth and then do the same for the larger pulley, measuring the X amount of teeth and see if the pitch is out, you can even do it on the belt if you can flip it over.

Say you have 30 teeth on you smaller sprocket, measure the circumference then measure 30 teeth on the larger pulley, it has to be accurate. You'll soon see if they don't match.



A

[Crazymanneil]

Good points toad. I would have thought the 8mm would be industry standard but it does not work too well with my clutch (which says 8M on the box). I think I'll post a wee youtube vid for you's to see. I have another belt ordered from a different manufacturer to try. Do you know who makes the BDL belts?

You made an interesting point about coatings. The belt looks like its ready to run though the clutch is brand new and has a silvery finish that looks like it may well be coated somehow. It would be nice to have a BDL belt to try...

And good idea Andrew, I will definately try that. I put the digital calipers on the teeth but they register 8mm but then again thats by sight only and the mismatch is small.

n

[Stuart]

All I can say is I had no such problem with the belt on my BNR clutch. It wrapped round no problem. Steve (Kubota 500 twin) had severe problems with a standard RE chain duplex clutch having its teeth wrongly machined so maybe its happened on this belt job?
The only probs I did have were calculating the belt size from forumla's. I have fixed centres

Stuart

[Crazymanneil]

Stuart,

Did you try mitcalc?

http://www.mitcalc.com/en/download.htm

Time trial limited but works out all sort of stuff like the force generated on the axles (useful for bearing selection). You need excel for it. I'm not sure how accurate it is yet since I've not got mine setup in real life but it seems close.

I hope the teeth on mine are machined ok since it will add delay sending it back if not (and won't be a great advert for BDL!). We'll see....

N

[toad]

"Good points toad. I would have thought the 8mm would be industry standard but it does not work too well with my clutch (which says 8M on the box). I think I'll post a wee youtube vid for you's to see. I have another belt ordered from a different manufacturer to try. Do you know who makes the BDL belts?"

it looks like they make there own belts.. google brought this up..http://www.beltdrives.com/

the site has some good info and contact number..

if it is expensive for you to call i would be happy to call them for you..

t

[Crazymanneil]

Hey,

I am still investigating this. It looks like you can use a Gates powergrip belt on a 1.5 inch BDL drive. I would have thought the fitting would be the same for my 3 inch? Goodyear also pops up a handful of times. I've another belt from a different manufacturer ordered so I will have to try that. Here is a youtube vid -

http://www.youtube.com/watch?v=YCI5fGwu-l8

Its awkward to shoot the thing and maipulate the belt at the same time but I am sure you can see whats going on. The first part of the vid is just loosly fitting the belt. The second part is with me stretching it to fit on with quite a bit of force. If I stretch and force it as much as I can I can just about get around 40% of the belt mated but the last couple of teeth are a real bind and I don't think the belt would last long. The other pulley by contrast is dead easy to fitup.

I worked out the belt loses synch by 1 complete tooth for around 30 teeth on the pulley, so thats about 3%? Does not sound like much does it...

N

[andrewaust]

But !!!! should it be out of syc at all ? If you were to machine gears and be slightly out you know what would happen = crunch. Belts need some tension but not brute force, sounds like you are making progress though.

Wouldn't you think manufacturers would use a standard pitch , same deal with some oil fittings on vehicles, some are NPT some are BTP, "Bloody hell" always something to totally bugger you up

In regard to threads, I hope the yanclone has a 1/8 NPT tread on the oil outlet "or" I'm in a lot of doo doo ????



A

[johnfireball]

Hi Crazy,
From my experience with machinery cars etc the belt should wrap around the pulleys perfectly by hand. Sounds like you have a mismatch on the large pulley.
John.

[Crazymanneil]

Hey guys

Got another belt today. It didn't fit particularly well either although it was a little better. I put this down to the other belt being a little softer than the first one and so could be squished into position ok. Both the belts I have are identical and fit perfectly into the front pulley so there must be some standards out there! I took some measurements and have a few ideas. Might change to another clutch, not sure yet. Would be nice to have a proper BDL belt to have a look at.

N

[toad]

crazy
i can see what your talking about. that's not right...from what i can see in the vid, it appears that the belt is not fitting all the way down in the teeth.. like it kinda wants to ride on top of the teeth.. a vid is worth a million words..

are all the components from different sources? i would almost say the front pulley and the belt belong together..if that is a standard harley clutch basket,, the belt and front pulley are non matching in reference to the basket. i can't for the life of me understand why it all says 8mm and it don't match up..

t

[Stuart]

I looked into getting the very latest type of belt which I thought was the same size as the HTD but I was told it was a different animal and wouldn't quite fit. The teeth were a bit different in profile. Might be worth double checking what kind of belt? That video shows the problem up real good. I never had that problem.

[Crazymanneil]

toad / stuart

i think you both hit the nail on the head. i measured the pitch of the clutch teeth by wrapping a bit of paper round it and even averaged over 30 teeth or so it was 8mm exactly. i measured th belts too and both were fine. so i scratched my head a while then took off front pulley to compare.

the tooth profile is a little different on the pulleys, so i got the calipers out again and measured depth rather than pitch. seems the bdl is shallower as well as the different profile. some research needed now to determine what it should be or maybe only bdl make it?

perhaps i could have the teeth recut somewhere although i fancy a thinner clutch now due to a design change on the bike which would work better that way.

getting there though! thanks for the replies

n

[Stuart]

Yeah, serveral websites seemed to indicate that these belts would be ok and were the next best thing to go with HTD cogs. They were made of even better material which appealed to me. But man in brown coat behind desk had furrowed brow and said they wouldn't fit. I steered clear of them.

Stuart

[sbrumby]

Might sound daft but have you measured the dia. of the said cog, calculate the circumfrance, and count the teeth. The pitch has to be a multipul of the circumfrance and this has to be the exact No of teeth, anything else is wrong.

[Crazymanneil]

good point sam. i measured about half of the circumference using a bit of paper wrapped round and it came out correct. am pretty sure tooth profile is wrong, though not sure if a different clutch would be better. hard to get the info even from manufacturers. may see if i can get somewhere to recut the different profile into the teeth but not sure where yet.

n

[Anorak_ian]

Hi, My Bob Newby (BNC) clutch had no problems going on the clutch and pulley, the belt went completely round the clutch with no problem at all, however I did try it on a Harley clutch and it had the same problem you have.

The Harley clutch was Imperial measurement while the belt and pulley were metric.
What's the chance that an imperial clutch has been put in the wrong box or packaged up wrong?

[Crazymanneil]

Good point Ian although measuring the teeth it comes out to be 8mm, but of course thats only half the story as the teeth have to be spaced 8mm at the PCD, not at the OD of the pulley. The devil really is in the detail. And then on top of that there are tons of teeth profiles out there which does not help as they are incompatible with each other. The one on the BDL could be anything at all.

I've decided to buy another BDL clutch basket as they take the same clutch plates anyway. The new basket will be thinner though which works out ok for my bike. Hopefully I can get a belt to fit ok.

Will post up when I get the new basket.

N