Belt drive on a thru-axle Cruzbike

[bret]

The earlier models had hinges in the front triangle to permit length adjustments, so the chain length would change as well.

But the thru-axle Q45 has the adjustment axes coincident with the crank axis and wheel axle. Changing the pedal distance does not change the chain length.

An eccentric bottom bracket would permit using a belt drive. I don't know if the existing bottom bracket is a standard size to permit using one of the already available eccentric brackets.

The other problems to solve are alignment between front cog and wheel cog ("chain-line"), and an internal gear hub. Unfortunately, the Shimano Alfine 8 uses washers with a block to fit the drop-out as it's anti-rotation solution.

I don't have the $$ to pursue this right now, but I wouldn't mind if someone solves it while I save my pennies.

 

[Gromit]

The earlier models had hinges in the front triangle to permit length adjustments, so the chain length would change as well.

But the thru-axle Q45 has the adjustment axes coincident with the crank axis and wheel axle. Changing the pedal distance does not change the chain length.

An eccentric bottom bracket would permit using a belt drive. I don't know if the existing bottom bracket is a standard size to permit using one of the already available eccentric brackets.

The other problems to solve are alignment between front cog and wheel cog ("chain-line"), and an internal gear hub. Unfortunately, the Shimano Alfine 8 uses washers with a block to fit the drop-out as it's anti-rotation solution.

I don't have the $$ to pursue this right now, but I wouldn't mind if someone solves it while I save my pennies.

The Q45 specs say that the bike has a bog-standard, BSA threaded bottom bracket.
"Bottom Bracket - Square Taper 68mm*113mm".

 

[Robert Holler]

I am of the opinion that a good clean chain drive will always be king and always be the preferred drivetrain. I have seen studies that belts are not more efficient until over a specific wattage - and it was of a wattage that a lot of riders are only at during their peak anyway - so there is no efficiency gains. Add to the the loss and expenses in the hub. There is a reason these things come and go and never actually take the place of the chain.

 

[bret]

belts are not more efficient until over a specific wattage

I am not interested in watts. Unless it's debilitating, a few extra watts means I slow down a little and probably stay in better shape - only for a narrow segment of the riding public does this matter, the majority will not notice, nor care. Riding a faster bike because I spent money to get a lighter one does not mean I am healthier.

I am interested in a bicycle as transportation, and chains mean grease, and work re-lubricating every time I ride in the rain, which relegates my bicycle to a fair-weather, and somewhat elitist, hobby for people with substantial disposable income and extra time to dedicate to it.

A chain means I must have the time and space to clean and re-lube it - somewhere I can use solvents and manage splashed oil and grease and that's on the dictates of the weather, not my convenience. For someone living in an apartment, or a shared flat, the solvent and grease issue is a concern - not everyone handles solvents well.

I crewed on a RAAM - enjoy the hobby of pursuing peak performance. But the vast majority of riders want to ride, and it seems clear to me that the populace will benefit more from more riding than from peak performance. More time on bicycles, less time with cars. An emphasis on peak performance will drive people away from cycling, rather than increase it's popularity.

I want to ride my bicycle year round in any weather, and switching to a belt drive eliminates many of the barriers to that. Less hassles means more riding and more riders. More riders means better social accommodation for cycling, leading to even more demand. That means a broader customer base, as well.

More desire, more associated innovation, such as clothing solutions, social solutions, technical solutions.

You advertise yourself that this platform prevents or avoids widely experienced bio-mechanical problems such as numbness in wrists or due to spinal mis-posture. Many people would ride if they could manage those issues - and those people vote on road and law improvements. And you have a monopoly on this platform now.

At least please don't put barriers in the way of people that want this bio-mechanical form factor for general riding - the audience for general cycling massively dwarfs the people who want to, and can afford to, sacrifice all else for performance - you are really shooting your business in the foot.

Allow 2"+ tires on all your designs even if 'performance' suggests to you personally to use narrower ones - particularly on an 'off-road' design like the Q45. Please don't design your forks to prevent a belt drive - accommodate one of the anti-rotation methods for internal hubs (and not just the Rohloff - that's very expensive). You use an add-on piece at the end of the stays for the derailler hanger now - design that piece for the anti-rotation connection and do the same on the other side if needed.

Let us work out how to use a belt drive on a Cruzbike. We want to. We can ride more that way.

 

[CoolBreeze]

Bret, have you heard of waxing your bicycle chain? Ordinary wax, used for canning or making candles, is cheap, repels dirt, and keeps your chain cleaner for longer. Initially it may be a little work to remove the original grease that a new chain is packed in, as explained elsewhere on this forum. A clean chain placed in a jar with enough wax, sealed and placed in a pot of boiling water, is all it takes; the procedure is well documented in the forum.
I doubt very much that more people would ride bikes more if only they were outfitted with belt drives. Internal geared hubs are far more expensive and complicated than cassettes and derailleurs. Do you honestly think that most people would rather pay $1000 more for a bike so they wouldn’t have to learn how to shift gears? Or that belt drive and internal gear hubs eliminate all bicycle maintenance? Maybe these complicated systems are fine for people with substantial disposable income, but I prefer the simplicity, lighter relative weight and efficiency of a cassette and derailleur. I use my bike to commute to my job when the weather allows, because I’m not riding 70 km round trip in the rain. Maybe that qualifies as an elitist hobby, but I would guess that most people who use a bike for basic transportation on this planet are not using an internal gear hub.

 

[bret]

I waxed the chain on my previous Q. It must be re-done when it rains. This is not a solution for what I am pursuing.

zerofrictioncycling.com.au has supplies and information about waxing.

You are welcome to continue using a chain if you like, I don't mind. I am interested in putting a belt on as I can ride in the rain with less hesitation.

A few years ago my surgeon went into my ankle, removed loose debris, and had a good look. I am told to use the joint to pump fluid through it, but not to try to build it up, as there isn't much joint left to build up - I'll only hasten the day he must fuse the joint. For this reason, my Tern S8i belt drive commuter bicycle has a Grin Technologies motor on it - I do not hesitate as much to ride as I know I don't need to over stress my ankle, and I don't need to spend time on maintenance if I use it in the rain because it has a belt drive and Tern makes good kit.

I ride more. I get more exercise. My health is better. And I'm not using a car. And it changes my priority for making decisions about buying weather clothes, bags, lights.

However, despite some custom features I had made in concert with Quantum Cycles (plug for local do-anything people here in Perth), I find that my wrists hurt if I ride for more than an hour, so I bought another Cruzbike. An added advantage is I can also ride the Q45 in the morning on a training stand while I read my email and the news before I have my breakfast.

This is a thread about belt drives on a Cruzbike. I do not need to decide what other people should have, and that isn't relevant here. I would like a belt drive, and I'd be happy to work with others to try to make this work on a Cruzbike because then the option is available to those that do want it.

I'd like to hear from people that have ideas towards getting a belt drive on a Q45, or other Cruzbike, so we can share.

 

[jond]

Since you’re in Perth maybe look jt up. He may have an idea or two.

 

[Rampa]

Idler wheel behind the crankset should do it just fine. That's the optimum place when belts are used on mountain bikes. There are even sprung ones for full suspension. Like on the Zerode mountain bikes. https://zerodebikes.com/blog/zerode-carbon-drive

Since chain guides are already standard fair for mountain bikes, it should be relatively easy to find something you can adapt to a belt guide.

 

[bret]

Idler wheel behind the crankset should do it just fine.

I looked at the web site you mentioned. That's a nice implementation for a bike where the distance between the axle and the crank vary. The distance between the crank and the axle on a Q45 with a thru-axle does not vary, even when changing the pedal-seat distance for different riders.

The belt must be released to change it, so a small reduction in the crank-axle distance must be possible, and then re-tensioned before use, and an eccentric bottom bracket permits that with no structural changes to the Q45. If we weld something on, we must then heat-treat the stays-and-bottom-bracket part again. But I don't see a need.

Am I missing something?

The issues I'm aware of now:

1. Selecting an appropriate eccentric bottom bracket.
2. Selecting an appropriate internal gear hub. Must work with thru-axle and anti-rotation mounting somehow (biggest problem).
3. Aligning the crank cog and the drive cog. Dependent on the internal gear hub selected.
4. Sizing the belt that fits the application.

Apart from solving the anti-rotation problem, this can probably be accomplished with off the shelf parts now. Hopefully that has a solution as well.

Can you think of other issues that must be solved in order to replace the chain (and running bits) with a belt drive? We need not split the frame, as releasing the thru-axle permits opening the triangle to drop the wheel and remove/replace the belt - the fork separates from the stays.

 

[Rampa]

These types of things have been bolted to mountain bikes for years. Lots of different mounting methods. I think some even mount under the external bearing, so clamped in that way. They can be sprung or un-sprung. In fact, they usually are un-sprung.

 

[bret]

Thanks for the replies. I am continuing this in the Innovator's Workshop: https://forum.cruzbike.com/threads/belt-drive-on-a-thru-axle-cruzbike.14219/