ALL belts are uneven, dress them

You got a digital caliper?

Did you know that all of the v belts I've tested are not consistent to their stated dimensions along its top width? The top width varies along the belts length sometimes up to .8mm. That's no good. Vibration and shitty wear will result.

Breaking in a wobbly ass belt will just give you a more wobbly belt.

So I made a v belt dressing jig.

Got some sticky coarse 40 grit sandpaper and set The jig to the thinnest width part of the belt, then manually pull the belt thru until the belt is even. Then it should keep that proper width while it wears in.

I checked the belt and it has a .7mm diff across the top. WTF?

I use 2 belts so you can imaging the vibrations I had with them at high speed. I measure the thinnest width on the belt first, then mark with a paint pen. Then check high spots. I pull the belt thru a few times and measure. Keep doing this until you're within .1-.2mm

It was fucking easy as shit and my bike has never been smoother.

If you see the belt going up and down in your pulleys when pushing it around, you got a wobbly ass belt bitch!

Fix it.

I should sell this jig.

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Re: ALL belts are uneven, dress them

Labels are where the width seems to be most, that's so fucked.

That's vanity, at the cost of a shitty tolerance

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Re: ALL belts are uneven, dress them

Jbot's Belt Truer , has a ring to it . ;)

Stating the obvious , maybe the belt makers make belts a bit out of spec to enhance quicker wear probabilities .(edited)

Re: ALL belts are uneven, dress them

Can I just send ya some belts and money or what? ;)

Re: ALL belts are uneven, dress them

Haha I should make a belt dressing machine. That would be so amazing to have. Like a drill doctor for belts.

Re: ALL belts are uneven, dress them

Just mussing ... That'd be pretty easy to make . Maybe a solid axle driven wheel under the belt , maybe protruding through the current plate and a wheel atop the belt that could be flipped out of the way , with a position lock for constant pressure .

Re: ALL belts are uneven, dress them

Belts don't come true from the factory!?!whaaaa! Blue converse with orange laces! What a world we live in.

No wonder why my hobbit hates me.

Re: ALL belts are uneven, dress them

Josiah Radebaugh /

Shoot. What is this sourcery? Hek, could make one out of wood just as easy.

Re: ALL belts are uneven, dress them

I copied my own response from that other place, I was wondering if fancier belts would have less inconsistency.....

I checked a Furioso, Bestorq, Bando, and Malossi belt. I have no objective numbers as my sheds a mess and I couldn't find my calipers, I just used an adjustable wrench to get a consistent point of measure. The first three all have noticeable width variations. The Malossi is more consistent, but it does have a spot where the cords don't seem to have trimmed cleanly and cause a bump.

You have proven that dressing belts needs to be part of the tuning process. I'd never even considered checking them before.

Re: ALL belts are uneven, dress them

> Josiah Radebaugh Wrote:

> -------------------------------------------------------

> Shoot. What is this sourcery? Hek, could make one out of wood just as

> easy.

Actually yeah, you could. Would be way easier too to cut the angles on a table saw. Good call.

Re: ALL belts are uneven, dress them

what else have you been dressing you sick fuck.

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(edited)

Re: ALL belts are uneven, dress them

I have noticed it before but it was always acceptable enough and had no way to fix, but tying 2 belts together made it awful at top speed. I want to true up a few belts down to .05mm and see how smooth I can get the trans.

I bet this belt variance is 50% of the vibration problem on French bikes. Without having a rear pulley to open to accept the belt bump, all that vibration goes right into the engine swing. Fuuuuck that

> Thomas TPRF Wrote:

> -------------------------------------------------------

> I copied my own response from that other place, I was wondering if

> fancier belts would have less inconsistency.....

>

> I checked a Furioso, Bestorq, Bando, and Malossi belt. I have no

> objective numbers as my sheds a mess and I couldn't find my calipers, I

> just used an adjustable wrench to get a consistent point of measure. The

> first three all have noticeable width variations. The Malossi is more

> consistent, but it does have a spot where the cords don't seem to have

> trimmed cleanly and cause a bump.

>

> You have proven that dressing belts needs to be part of the tuning

> process. I'd never even considered checking them before.

Re: ALL belts are uneven, dress them

That boy looks like my old boy Rick.

He was an ancient rabbit. Loved him. He got cancer, without the tumor he probably would have lived forever

Graham Motzing Wrote:

> -------------------------------------------------------

> what else have you been dressing you sick fuck.

> >

Re: ALL belts are uneven, dress them

seriously though this is huge, i've had so many french bikes that have vibrated and shook like crazy and never been able to figure out why some do and some don't... i've replaced belts before and had it go away or get better or get worse but never thought the belts being uneven would be part of it.

this is pretty much the whole reason i stay away from clamp mount PHBG19 and VM18 setups on 103's, if i can figure out a way to go back to the simplicity of a 2 petal phbg 19 setup that would be awesome.

Re: ALL belts are uneven, dress them

I also noticed on one of the cheap AX belts I checked that it was bent. Like sighting down along it the belt curved sideways. I'm not sure if that's from manufacturing or bad storage.

Re: ALL belts are uneven, dress them

Dirty30 Dillon /

Questions:

How do you angle-cut the profiles on the jig sections? Getting those at a consistent angle is pretty important or you just make it worse.

How do keep the belt flat in the groove?

What are you finishing the rough edge with? If it's left rough sanded, how can you know if the smoothness increase isn't due to the furred/softened edges of the belt from sanding and they'll wear in back to an uneven state?

Re: ALL belts are uneven, dress them

> How do you angle-cut the profiles on the jig sections? Getting those at

> a consistent angle is pretty important or you just make it worse.

Ypu do it in a mill. Or if you made the jig outta wood you use a table saw.

>

> How do keep the belt flat in the groove?

Fingers push the belt down.

You must be selective when trying the belt, don't just go at it.

Measure and mark along the length, then sand the high parts first.

>

> What are you finishing the rough edge with? If it's left rough sanded,

> how can you know if the smoothness increase isn't due to the

> furred/softened edges of the belt from sanding and they'll wear in back

> to an uneven state?

The edges will flatten and smooth by the pulleys. I know because I know. I also know that a new belt with a big ass hump isn't going to be good for anyone.

A belt will want to stay true if it starts true. The uneven state is when new, and that's fucked.

If your pulleys are true, the dressed belt will only wear to be more true, unless you do a lot of slipping...

There is something to the idea of belt break in, but it won't fix a.8mm difference. It'll just wobble like fucking crazy.

You can melt the poly threads on the outer part of the belt if desired, but they'll just smooth out after being run true for a few miles.

The belts I cut yesterday are smooth after 1 ride.(edited)

Re: ALL belts are uneven, dress them

My caliper technique,

Rest the top on the caliper on the belt, then I measure with the wide flat part of the caliper right at the top edge

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Re: ALL belts are uneven, dress them

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Original hobbit belt, used

14.67mm at its widest,

14.16 at its thinnest point

Re: ALL belts are uneven, dress them

Used gates "polini" belt

16.5-16.8 Closest accuracy I've found so far

Re: ALL belts are uneven, dress them

Thank you for always being willing to consider what's ACTUALLY goin on and taking nothing for granted. Real progress. I mean it man, thank you.

Re: ALL belts are uneven, dress them

All I want is the imperfect machine to become closer to perfect.

Thats why I love mopeds. So much imperfection to improve upon

Re: ALL belts are uneven, dress them

I've seen a bent belt too, though usually it's a hump from where the edge pieces are fused together.

Also have seen belts with a significant twist, and a side bend.

To true them up I've hung them in the sun with a cinder block hanging off the belt to try to fix. Had some success.

I found that my hobbits belt that I recently did this edge truing to still has one high spot, gonna take it down today. One easy test is to find the low spot, then sharpie its location all the way around on the variator or fixed cheek side.

Then roll the bike and see if the belt ever rises above that marking, denoting a wider spot.

Thomas TPRF Wrote:

> -------------------------------------------------------

> I also noticed on one of the cheap AX belts I checked that it was bent.

> Like sighting down along it the belt curved sideways. I'm not sure if

> that's from manufacturing or bad storage.

Re: ALL belts are uneven, dress them

What's bugging me now is I've watched the rear pulley wobble on engines and blamed it on a warp or misbalance there, now I'm wondering if it was just a really fucked belt.... Its bad enough trying to diagnosis problems in the moment. Worse thinking that input shaft bearing that went out two years ago may have held up if I'd just sanded my belt instead of trying to swap pulleys....

How has it taken J Bot's curiosity for someone to even think about belt consistency? We're all neanderthals and he's skipped to post human.

Re: ALL belts are uneven, dress them

> Thomas TPRF Wrote:

> -------------------------------------------------------

> What's bugging me now...

isn't that the worst part? as i'm reading this thread the first time i'm just thinking back on all those builds i've had that had weird driveline vibrations that i could never fix.

like that one time i ended up with an egg-shaped sprocket and couldn't figure out why my chain would get loose-tight-loose-tight.

Re: ALL belts are uneven, dress them

This thread is a total what-the-fuck-why-has-noone-thought-of-this-before moment

Re: ALL belts are uneven, dress them

Played with my moby belt

Very used dayco belt, off by about .7mm. Now I'm about .2-.3 and it's better for sure. Top rpm on the stand used to throw this thing around on the concrete. Not so much now. Most notable is top speed when the belt is really flying

Its better to do this to belts when they're new and firm. Measurement is a bitch if the belt has burns or got soft on the edges.

I picture a caliper setup you pull a belt thru and it tells you the high and low spots. Someone do that

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Re: ALL belts are uneven, dress them

I would be interested to know if this might have a correlation with the fuel starvation problems some people seem to have on the French single variated bikes. I don’t own one, but remember threads about the vibrations sloshing the fuel. I will definitely be checking my Derbi belt. Thanks JBot

Re: ALL belts are uneven, dress them

Josiah Radebaugh /

Woner if thats where my 28 mph vibes are coming from. This is truly amazing!

Re: ALL belts are uneven, dress them

Ok, watch this.

Even though it's Chinese I bet most V belt mfr processes are the same inthe US.

Warning: epic fucking music to jack it to during this vid.

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