Middrive, belt drive and coaster brake

[elgeniz]

I want to build a bike from scratch with the following as mandatory. But don't know if it's even possible.
- Middrive
- belt
- coaster brake
- 5-7 gears

 

[nicobie]

Anything is possible. But is it reasonable or cost effective?

 

[neptronix]

You'll probably need and IGH and i gotta let you know that IGH is 4-15% less efficient than just using a derailleur setup, so that's gonna eat into your power :/

Getting a ~7 speed IGH that has something like a drum or coaster brake on it isn't too hard, getting a belt drive in addition might be impossible.

If you're looking for drivetrain durability consider using some thick singlespeed chain and a chain guard, it will make your build a lot easier!

 

[offGridDownUnder]

A belt means you are giving up flexibility for the belt-line. Chains bend sideways - belts do not.

You'll want to investigate the 'chain line'/'belt line' of your motor and destination rear hub. Gates recommends a millimetre of difference at maximum.

My trike has a belt from (mid mounted, rear hub) motor to actual rear hub, but I have much room to play. For an upright bicycle form, you have less option in this way.

 

[offGridDownUnder]

If you don't use all of the sprockets, you can mount a belt sprocket with spacers anywhere along the freewheel/freehub to buy more adjustment room to match a front motor sprocket line.

Gates belt sprockets to mount to a Shimano 9 spline freehub are standard parts.

There are even some rear hubs with freewheel/freehub and internal gears - 3 at least, maybe some with 5 internal. Don't know if that suits your wishes.

 

[elgeniz]

Okay so what I understand: Belt drive with these settings are impossible to get a good result. I was afraid that was the case, thats why i tried this Forum.

So a decent middrive motor with 7 gear hub and a chain with chainguard is the way? I'm building a bike for mass production

 

[E-HP]

Okay so what I understand: Belt drive with these settings are impossible to get a good result. I was afraid that was the case, thats why i tried this Forum.

So a decent middrive motor with 7 gear hub and a chain with chainguard is the way? I'm building a bike for mass production

Do you have other examples of bikes you’ve produced?

 

[elgeniz]

Yes. But that's not relevant for this case. I'm building a bike in order to win a tender at a municipality the next quarter. Its a whole new task for me. Since I'm just use to build one unit at the time
I'm looking to build a price sensitive and extremely low maintenance bike. The tender spec is pretty straightforward Therefore my specs

 

[Chalo]

I'm building a bike for mass production

Well if you're starting from scratch, and will be designing your own frame and other parts, then all the fit and physical compatibility issues can be addressed.

5 and 7 speed internal gear hubs are not designed for superhuman power or torque. At EU-legal power levels, they'll probably be okay, but you will need to employ a shift cable power interrupter. A hub intended for motor power, like the 3X3 Nine or one of the more robust Enviolo models, would be a better match for the application, but is expensive.

Bicycle drive belts are a problem no matter what's turning them. They require an amount of static tension that is harmful to the other parts of the system (especially the hub) and they don't last as long as chains. They stack friction and hysteresis losses on top of gearbox losses to exact a noticeable performance penalty compared to traditional bike transmissions.

If you want to make a business of it, you probably need to decide an acceptable price that will allow you to sell in quantity, then budget out your individual components and costs to see if it's feasible to make everything you want (including profit) fit inside that price. Even thrifty mainland Chinese manufacturing has its limits, and it's no good to manufacture a bike with every single checklist item you desire, if it costs so much that you can't attract buyers.

 

[offGridDownUnder]

Well if you're starting from scratch, and will be designing your own frame and other parts, then all the fit and physical compatibility issues can be addressed.

This sounds real - you can space the components as you need to ensure the belt line.

I am not certain of the other remarks about the consequences of belt drives. My reading suggests a Gates belt will last for 20k kilometers. As well, I see Gates sells snubbers and tensioners for belts which suggests they may be run with lower tensions.

 

[Chalo]

This sounds real - you can space the components as you need to ensure the belt line.

I am not certain of the other remarks about the consequences of belt drives. My reading suggests a Gates belt will last for 20k kilometers. As well, I see Gates sells snubbers and tensioners for belts which suggests they may be run with lower tensions.

I keep hearing things about how long belt drives last, and I keep observing them laid to waste at a young age when they arrive at my work stand. Gates has been hammering away at the problem for decades now, so they're probably the best in the business. But not observably as worked out as they claim.

 

[Vbruun]

I think the main benefit of the belt drive is that they are much cleaner than chains but also that they need less frequent adjusting of the chain tension.

IGH chains run with a straight chain line and kept lubed will last for a long time. But you will need to lube them regularly (by-weekly or so in my climate) and tension the chain a few times per year.

From what I have seen the belts do last at least 10.000 km without much work and I think that is a real benefit.

 

[ebike4healthandfitness]

I want to build a bike from scratch with the following as mandatory. But don't know if it's even possible.
- Middrive
- belt
- coaster brake
- 5-7 gears

Bosch Active line plus mid drive will work with coaster brake:

Active Line Plus: the innovative Bosch motor for eBikes

The Active Line ensures smooth, agile acceleration and enables easy handling. The barely perceptible pedal resistance above 25 km/h increases the fun factor.

www.bosch-ebike.com

It will also work with a belt drive.

 

[ebike4healthandfitness]

Getting a ~7 speed IGH that has something like a drum or coaster brake on it isn't too hard, getting a belt drive in addition might be impossible.

Why would it be impossible?

This bike has belt drive and 5 speed IGH:

Electric Bikes | Adult Electric Bikes | PRIORITY CURRENT E-BIKE

The Priority Current is the most progressive E-bike on the market, with more power and more comfort than any of its competitors at an unmatched price.

www.prioritybicycles.com

EDIT: Here is a 7 speed IGH and belt:

BRILLIANT L TRAIN

The L-Train is a nimble, speedy belt drive bicycle with a larger gear range to tackle leisure rides and daily commutes with ease.

www.prioritybicycles.com

 

[neptronix]

Cool but this is a DIY build so we need DIY parts to do that, not a recommendation for a prebuilt bike that has proprietary parts you can't buy / fit to a DIY ebike.

 

[ebike4healthandfitness]

Cool but this is a DIY build so we need DIY parts to do that, not a recommendation for a prebuilt bike that has proprietary parts you can't buy / fit to a DIY ebike.

I thought it was a mass production bike? (Edit: See post #6 where he says the bike will be mass produced.)

 

[neptronix]

Oh, well i'm wrong!

 

[2old]

I must be way behind the times, but doesn't a mid freewheel when pedaled backwards. How is that compatible with a coaster brake?

 

[ebike4healthandfitness]

I must be way behind the times, but doesn't a mid freewheel when pedaled backwards. How is that compatible with a coaster brake?

Not all mid drives freewheel when pedaled backwards.

Two that I know of that don't are the Bosch Active Line Plus and the Tongsheng TSDZ2 coaster brake version.

 

[2old]

Not all mid drives freewheel when pedaled backwards.

Two that I know of that don't are the Bosch Active Line Plus and the Tongsheng TSDZ2 coaster brake version.

Thanks; I wasn't aware of these. It looks like the the TS could be a viable option.

 

[ebike4healthandfitness]

Thanks; I wasn't aware of these. It looks like the the TS could be a viable option.

The Tongsheng is known to be unreliable and is therefore not recommended for serious transportation. I'm no expert on the Tongsheng but one of the weaknesses it has is the pedal spindle and bearings. However, there is a commonly known fix as described here:

Tsdz2 bottom bracket / crank spindle bearings

Hi, sorry I've searched but failed to find anything. I have a 36v 250w on stock firmware with UK legal low speed limiter. I've done 4500km never opened, used on road and gentle off-road all seasons for a year since fitting on a old FS MTB. There is play/wobble developing in the bottom...

endless-sphere.com

I don't know how well that fix in the link works as like I said I am no expert on the Tongsheng. Even if it did work the OP would have to tear apart and rebuild each motor as part of the build process for each of his production bikes.

Speaking of tearing the motor apart another problem I have read about is the blue gear. A metal gear and a stronger nylon gear are sold as replacements. Not sure how much of the problem with the blue gear is due to heat, but I have read even the 500 watt version of the TSDZ2 gets too hot. Therefore heat is another thing to be concerned about though people have reported good results when DIY heatsinks are added to the motor.

The sprag clutch is also a commonly sited problem. Fortunately the coaster brake version of the Tongsheng does not have the sprag clutch.

 

[2old]

My comment is related only to the possibility. I wouldn't and haven't purchased any TS models because the quality isn't existent IMO. My mids are BB's or Yamaha and I've never had a failure.