Belt-Drive Full sus update

You may have seen me post before about the belt-drive Kona A I’ve been working on. Having had a few problems with the belt “ratcheting” I tried a DIY snubber to keep it in place. All that happened was the plate I used to make the snubber got bent out of the way by the belt as it climbed the teeth. So I bought a genuine Gates one. It arrived today, fitted it this evening and headed out into the woods.

And it bent. Balls.

When it works, its ace, but it seems it just cannot cope with singlepseed climbing.

Chains are the future, belts as Saaaad. Or is it the other way round?

Sounds like your chainstay is either flexing or moving laterally due to pivot play.

Got a pic of how you mounted the snubber? How it’s mounted is very important.

I’m sure it is the chainstays moving, but I thought a snubber would prevent the ratcheting, but its clearly not up to the job 🙁

It started off with about 1mm clearance off the belt. And the black “spacer” is there to keep the pulley on the inner groove on the pin. My first attempt this evening saw it pop off into the other position. Design flaw I guess.

From an engineering point of view, that’s a poor design. There’s too much leverage on the plate.
It looks like there’s just about room for a second, thin plate inside the drop out.
That would make the shaft effectively shorter.
The thin plate would be under tension, so wouldn’t need to be particularly strong.
The existing outer plate would then be under compression, rather than a bending load, so would be adequate.

That snubber just looks wrong.

Try a homemade one out of L shaped alloy. 2 holes – one for the hub axle and the other for the derailleur bolt.

That will at least locate it properly.

Alternatively get a bit welded on the the sliding dropout to mount the pulley – it will reduce the bending leverage.

But probably the best thing is to cure what is causing the problem in the first place. Pivots or chainstay flex.

That snubber just looks wrong.

Ha! It the genuine Gates one!

I tried a homemmade one using plate, but that just bent, but I agree, it needs more section to it.
Gates have suggested a sliding dropout with built-in Snubber, so less cantilever, which makes sense. So I’m looking at checking measurements of my dropout with the one they have designed.

And I know it might be flex in the pivots, which is a real shame as the A made so much sense 🙁

Can you shim the pivots up tightly? It’s a shame you are having these problems – the Kona-A was a bike I had my eye on for a conversion.

Belt drive is really finicky for a conversion – it’s bad enough on bikes designed for it 🙂 The advantages make it worth persevering though.

The latest version from Gates with the centre ridge looks to me like it will be able to handle a bit of misalignment better.

This bodged YESS tensioner did a good job on a very flexy bike – no slip and it didn’t bend.

[/url]

The position of the pulley is not good though.

I just can’t see why the belt would climb the teeth to such an extent with slight misalignment caused by chainstay flex – that’s quite amazing. What are the torque limits on the belt and gear setup, and how are you pre-tensioning it?

the snubber needs to work where the belt engages the cog on the lower run, not behind – should be as per epicyclo’s pic. or did yours bend back as it slipped?

James, the snubber has a little pin on the back that fits in against the b-tension screw ridge on the dropout, so its fitted as Gates requirements. Its positioned just where the teeth are fully engaged.
see page 18 of this It also shows the ball-groove in the pin that i had to cover with a spacer to stop the pulley being pushed sideways.
I’ve asked Gates what forces were taken into account for the design, as they’re clearly not suitable. If there’s enough force in the belt to cause it to rise up the teeth, that’s the force the snubber should resist in bending.
Apparently I’m the first person to bend one! Grrr!

coffeeking – the only to pretension those dropouts is to lever them as back as possible. I could try fiting a bigger cog (which would give me a lower gear ratio) as the belt length is fixed, but I’m not sure the extra tension would do the frame any good.
Ah, the life of a bodger…

james-o – Member
the snubber needs to work where the belt engages the cog on the lower run, not behind – should be as per epicyclo’s pic. or did yours bend back as it slipped?

The 7 o’clock position is actually the best position because it allows the wheel to be removed without hassle.

I suspect the Gates snubber is made of Butterinium.

“Advantages make it worth persevering though”

I’m still curious what these are. What does it do that a single chaindrive doesn’t?

Increases your niche ratio.

Big pack -5
Full suspension -5
Gears -10
Snigglespeed +1
Snigglespeed on a full sus +10
29er +5
650B +7
Alfine +2
Belt drive +10
29er snigglespeed full sus belt drive +999999999999 stw god!

These only count if you post at least once a day stating your current configuration. An extra +10 if you suggest you’re going to try one of these configs and include the phrase “I think I’m crazy, but…”

29er snigglespeed full sus belt drive +999999999999 stw god!

I thought you got bonus points for a beard too?

Sam – lightweight and maintenance free. But the cost and faff only just makes it worthwhile. But I reckon as they get more popular, the cost will drop and availablitly of suitable frames will increase. I’m prepared to have a go at it to try and help things along.

lightweight and maintenance free

From what I’ve seen (which admittedly is not a lot) when considering it as a system – chain/belt, cogs/chainrings and frame any weight advantage is negligible.

Maintenance of a single cog bike is pretty minimal anyhow I find.

The advantage I do see is cleanliness, which would be great for folding commuters people are taking on public transport. Or for folks who need to store a bike in the spare room, so the wife doesn’t complain about grease on the carpet. However for a general mountain bike for the majority of people I don’t really see much/any benefit.

True, the stiffer frame is likely to add a bit of weight, but the belts themselves are bonkers light.
I agree about ideal for commuters and not so for mtbs. But, i figure if it works on mtbs, then it’ll have no problems on commuters.

Maintenance of a single cog bike is pretty minimal anyhow I find

Minimal, yes. But not non-existent.
How many people buy a bike-shaped-object from t**co, leave it out in their garden and throw it away becasue the drive-train has seized up? Leaving them with the impression that bikes are high-maintenance and not worth it. If you can persuade just one person off their sofa and back onto the bike which requires NO maintenance, then I’d view that as a success.
…and off the high horse 😉

And

Or for folks who need to store a bike in the spare room

Why not a mtb then?

I store my bikes in the spare room.

(sometimes)

😳

but the belts themselves are bonkers light.

how is the weight saved with wider sprockets at both ends ?

Maybe if you replaced the rubber belt with a metal one this wouldn’t be a problem. You could even cut holes in the metal belt to let the cogs sit even deeper with the added advantage that mud would be pushed out. I am sure you could come up with some kind of linky thing to allow the metal to bend around the cogs.

Minimal, yes. But not non-existent.

Maintenance doesn’t quite seem to be non-existent on your belt drive bike either, given you haven’t managed to get it to work yet!

WCA, sounds like a good idea. Do you have a prototype you could show us? I’m running something very similar on my bikes and it’s working fine, SS and geared. Slight addaptation of something which is comercially available (bought it from large Japanese company, just had to trim it to length and then join the two ends together to make a loop. They even make a particualr kind of tool which seems ideal for this)

😛

keep at it bandito
early uptakers always suffer while the niggles workout
eventually the luddites will realise that their rattly greasy old chain isnt as good as the latest belt drives and copy you

eventually the luddites will realise that their rattly greasy old chain isnt as good as the latest belt drives and copy you

the whole chain drive thing (particularly with derailleurs) is hopelessly Heath Robinson and it’s a wonder it works at all – however it does seem to work better than all the alternatives…

the whole chain drive thing (particularly with derailleurs) is hopelessly Heath Robinson and it’s a wonder it works at all – however it does seem to work better than all the alternatives…

I refer Mr. Barnes to exhibit A: the snubber, as seen above. 😉

isn’t the whole idea of a derrailleur other than to change gears to keep the chain tight when the distance between the crank set and cassette increases/decreases when you enter into the travel of a full suspension bike? I may be wrong but how the hell is a belt meant to stretch to let you actually use the suspension?

I refer Mr. Barnes to exhibit A: the snubber, as seen above

meaning what exactly ?

isn’t the whole idea of a derrailleur other than to change gears to keep the chain tight

no, it was invented about 100 years before rear suspension became popular, but it just happens to fulfill that function too!

Will the increased drivetrain tension not increase bearing wear rates?

isn’t the whole idea of a derrailleur other than to change gears to keep the chain tight when the distance between the crank set and cassette increases/decreases when you enter into the travel of a full suspension bike? I may be wrong but how the hell is a belt meant to stretch to let you actually use the suspension?

thats why hes using it on a kona A, the suspension on which pivots around the bb…..

Keep at it irbandito, any fule kno early adoptors gets all the slagging

how the hell is a belt meant to stretch to let you actually use the suspension?

Its a Kona A. It doesn’t matter. That’s the point.

simon – I believe PMJ is referring to the snubber itself being a bit Heath Robinson. Either that or he’s just being a facetious c0ck. 😉

chiefgrooveguru – it probably will, which is why I’m following epicyclo’s idea of not running it too tight and theoratically using the snubber keep the belt attached.

thats why hes using it on a kona A, the suspension on which pivots around the bb…..

ah right fair enough.

ts a Kona A. It doesn’t matter. That’s the point.

do you mean the pivot is coaxial with the BB ?

simon – I believe PMJ is referring to the snubber itself being a bit Heath Robinson

oh, right :o)

I’d love to get away from the derailleur system, that’s why I tried a Rohloff, but unfortunately that wasn’t designed for Lakeland aquabiking and had to be sent back to Germany once a year 🙁

roller chain 98.8 percent efficient, pretty good for ‘heath robinson’ the fact you need a ‘nubber’ for your elastic band says it all. Ask any ‘proper’ engineer. yup your flares get oil on them but i can live with that….