roburrito

I need help with adjusting the chainline with a sturmey archer hub.

I've been building a belt drive setup with a 5-speed SA SRF5 hub on a modified Steamroller frame.

I'm having trouble getting the chainline (beltline) aligned. When I first set it up, I had both flanges (chainring and cog) facing out, and the belt was tracking towards the hub (in). But then I watched a Gates video and you are supposed to have the chainring out and the cog in. When I did this I have the belt tracking away from the hub (out). I added a 4mm axle spacer to the non-drive side of the hub and the belt is still tracking 3-4mm out. I can't add more or there isn't enough axle for the nut to thread on to (with the lock washer). I don't think you can adjust the axle through the SA hub. I can't move the cog over on the freehub because SA has a stupid lockring that fits into a groove to hold it in place.

I'm using a Bontrager Race GXP crankset. I already have a washer between the chainring and the crankset in order to get clearance for the 55t chainring. Not sure how bad of an idea that is. I know they make spacers for GXP bottom brackets to go with some cranksets. Can I safely add spacers to the driveside of the bottom bracket?

Anything I'm missing?

FBinNY 

Belt drive is different than chain drive because belts aren't as flexible laterally as chains are. While perfect alignment of sprockets is important, getting the two axles parallel is more important. If you've ever used a belt sander you've seen how moving one end of the adjustable roller can cause the belt to walk to one side or the other.

I do these adjustments trial and error, but I believe the belt moves toward the side that is father away as if trying to become tighter.

So since you can't move the crank, tweak the rear wheel to one side or the other and see if that causes the belt to float to center. Obviously the wheel will now be slightly off center in the chainstays, but it should only need to be a hair off.

As far as which way to face the hub sprocket goes, you want the direction that keeps the belt centered naturally with better wheel alignment in the frame.

Dan Burkhart 

What are we looking at here?

It looks like a 9 spline driver, but according to Sturmey Archer's web site, that is only an option on disc brake compatible 5 speed hubs. Not that this would be the first time they were behind on updating the web site.
Anyway, if it is a 9 spline driver, you should be able to put spacers behind the cog and lock it on with a threaded lock ring instead of the snap ring. Should gain some.

roburrito

This is the hub: Sturmey Archer
As far as I can tell it can't take a threaded lockring, only the snapring. I don't understand why there is the extra splined section if that is the case. But I tried a lockring and there was no thread to screw it into.

fietsbob

Your frame alignment ia an unknown ..

FBinNY 

1- Sight the chainline like a rifle and set the rear sprocket to give you the nearest to correct chainline.
2- align the wheel so the belt floats to center on it's own.
3- ride the bike

roburrito

Its a Surly Steamroller frame. I brazed one of these into the seatstay. I don't think that should have changed the alignment?


This is what I'm asking help for. There isn't room on the driver for spacers to align the cog.

JohnDThompson 

Was it perfectly aligned before? As FBinNY notes, belt drives are particularly sensitive to hub axle/bottom bracket spindle alignment. My experience with modern production frames is that they are seldom well aligned.

fietsbob

It's a long ways from the builder's jig in Taiwan to you door via the QBP warehouse ,

it may never have been spot on in the first place .. before the cut and patch..

chain drive you would never noticed the imperfection , now you do..


did the person doing the modification check it on an alignment table ?

the top of those is very Flat as a reference surface

FBinNY 

Get is as good as you can, then align the wheel to try to get the belt to center itself. Unless that requires the wheel to be materially off center in the chainstays, you've solved the problem.

Otherwise it's a case of "if you can't raise the bridge, lower the water". If you can't match the chainline at the hub, consider changing it at the crank.

Dan Burkhart 

Well would you look at that. I looked through the web site and missed it. I'm also perplexed as to why they don't make it to work with a lock ring.

fietsbob

Hearing the S-RF5(N) driver is the same as what goes on the BWR hub so 2 cog Brompton setups offer 10 speeds .

<guess> Gates was focused on the global big dog Shimano, and not thinking of wee sun-race Sturmey Archer.

Gates may be accessible to questions from customers .

roburrito

I'll def fudge with alignment tonight.

Edit: Arg I just realized putting spacers on the bottom bracket would make my problem worse not better.

roburrito

Looks like the BWR hub uses the same snapring. https://www.bikeforums.net/folding-bi...ml#post9444048

Can't find a picture of it using a different retaining mechanism.

fietsbob

Where is the 1 chainring , inside or outside position on a typical double crankset .. ??

perhaps because it uses the same one?

SquidPuppet

By this, do you mean that you are unable to move the chainring any farther inboard because then it will hit the chainstay?

FBinNY 

I read it to mean that there were no spacers to remove. IME- they still haven't produced negative space spacers.

SquidPuppet

What is the washer he is talking about?

roburrito

This. Using a 55t chainring. I could switch to a 50t, but I'd have to find one.

FBinNY 

I don't think there is any. I had suggested moving the crankset, and he was saying that adding spacers would make it worse. I took that to imply that the corollary option of removing them to move it in wasn't available because there were none, though it could equally be a question of chainstay clearance.

Either way, he can't bring the crank in.

roburrito

Currently I have a spacer between the outboard side of the crank spider and the chainring in order to give myself clearance between the chainring/chainstay. When I had the rear cog flange out, the belt was tracking in and I was considering adding a spacer to the bottom bracket to further bring the chainring outboard. I had forgotten that I now need to bring the crank inboard because I've flipped the cog flange in (as recommended by Gates) and have the belt tracking out. Still, if its safe, a spacer on the BB might be a better option for chainstay clearance than a spacer on the chainring bolts.

SquidPuppet

Why not put the cog back the way you originally had it and either use spacers on the bottom braket or a wider BB? What is Gates's reason for running the cog a certain way? Unsafe? Wear?

Edit: Nope, I have that backwards. Nevermind.

Edit # 2 : Nope, maybe that would work.

roburrito

I'll give that a try if I can get this configuration to work. If I was to take a guess, flange in would prevent the belt from hitting the spokes if it slipped. The setup video I watched said something about making it easier to put on the belt.

roburrito

So I flipped the cog flange out and added a couple spacers to the bottom bracket. Fixed the chainline issue.

When I pedal normally its fine, but when I start pedalling hard, the belt tracks in on both the front chainring and the cog and eventually falls off.

I'm thinking chain tensioners on the axles might help fine tune the belt tension and the axle alignment. But could it just be that the Steamroller is too flexy for belt?

fietsbob

maybe a snubber ? (its not tight enough) still the axis of the crank and hub are not parallel?

or you should have gone with the https://www.carbondrivesystems.com/products/cdxsprockets center track version?