Chinese crank drives,throttles and gears.

Finally the chinese have got the crank drive motor right and are giving very high torque figures,the Kudos Ibex TCM motor has 60Nm torque at the motor,however with a throttle this torque is too suddenly delivered and that is the reason we are nervous about putting a throttle on the bike.

Our original samples used the cheap Shimano Tourney gears,these were rapidly destroyed by the motor,we have upgraded the gears to the stronger Alivio system,without further testing I would not be happy about connecting hub gears to these new crank drive motors. With a powerful rider the problem is obviously worse.

Standing on the pedal whilst operating the full throttles corkscrewed the gears.

I think the Alivio system is about the minimum quality that should be fitted with these new crank drive motors,with or without throttle. The Deore system is even stronger but difficult to source from Shimano at present.

I suspect it is one of the reasons why Bosch would not fit throttles on their system,aside from the fact that throttles are illegal in their prime market-Germany.

The TCM motor is now being offered to many of my chinese suppliers and I have been offered samples using that motor from many suppliers,some using the cheapo Tourney gears,I am sure many of these bikes will be offered by the cheap internet sellers-looking at the grief many testers gave my Ibex on the test track at London Excel Cycle Show and the thousands of testing cycles that my supplier performed on the bike,I am confident that the Alivio gear system will take the abuse but nothing less and not yet with a throttle.

Many testers reported that the TCM motor has considerably more torque than the Bosch system and that the bike accelerated strongly.

We are trying to incorporate a throttle that allows the power to be introduced gradually so as not to shock load the chain and gears,this is still under development.

If you want a throttle the BPM hub drive motors with low speed torque (we called it the TOP system)is probably a better choice as the sudden torque caused by quick full throttle operation at worst will just cause wheel spin.

Dave

Kudoscycles

Hub gears (esp nuvinci systems) are stronger than cassette + derailleur systems.

 

The sprocket on a geared hub is normally steel, whereas cassettes are alloy.

 

IMHO crank drives are ideally suited to hub gears.

Sorry for a silly question... but don't hub gears require back pedalling to change? Or have things moved on since the '70s?

Perhaps it comes down to the programming of the controller - limiting the torque until the drivetrain is rotating with a few rpm, then the gears would be able to handle the power better. Highest torque loads on a drivetrain imo happen under acceleration, perhaps restrict the rate that the power being applied to the motor ramps up at in situations of sudden full throttle

Perhaps it comes down to the programming of the controller - limiting the torque until the drivetrain is rotating with a few rpm, then the gears would be able to handle the power better. Highest torque loads on a drivetrain imo happen under acceleration, perhaps restrict the rate that the power being applied to the motor ramps up at in situations of sudden full throttle

 

Oigoi....thats exactly what we are working on,to incorporate a throttle.

Dave, you are right. Develop a system to ramp up progressively and the gearing systems will not be wrecked.

 

Soft start could be configurable by dip switches or pre programmed.

Sorry for a silly question... but don't hub gears require back pedalling to change? Or have things moved on since the '70s?

 

Things have moved on. You just need to ease off momentarily as you change gear. I wouldn't consider an Ebike with anything other than hub gears, especially for a commuter. The low maintenance is a great benefit with this type of setup.

The Kalkhoff crank drive s-pedelecs with the Bosch 350W unit have higher-end Shimano deraileurs.

 

I've not seen a high performance crank drive bike with Shimano hub gears, although some use the NuVinci hub which suggests it's stronger.

Hub gears (esp nuvinci systems) are stronger than cassette + derailleur systems.

 

The sprocket on a geared hub is normally steel, whereas cassettes are alloy.

 

IMHO crank drives are ideally suited to hub gears.

Nuvinci 360 is strong enough, but definitely dodgy on a Shimano 3 spd or 8 spd. The outer sprocket might remain intact, but not much use when you have shrapnel inside the hub.

The Kalkhoff crank drive s-pedelecs with the Bosch 350W unit have higher-end Shimano deraileurs.

 

I've not seen a high performance crank drive bike with Shimano hub gears, although some use the NuVinci hub which suggests it's stronger.

 

I think there is a degree of nervousness about combining hub gears with these German S Class bikes. Hubs are ok with bikes intended for the rest of Europe.

These torque figures are not enormous.If a 12 stone rider puts all his weight on a 6" crank he exerts a torque of 84 lb ft equal to 113nm.Tonaro claim 128 nm and have been running successfully for years with fairly low end Shimano derailleurs.So what's the problem?

These torque figures are not enormous.If a 12 stone rider puts all his weight on a 6" crank he exerts a torque of 84 lb ft equal to 113nm.Tonaro claim 128 nm and have been running successfully for years with fairly low end Shimano derailleurs.So what's the problem?

 

It's probably just scaremongering. I've not had any problems with a crank drive / Alfine hub gear combination and I don't ever recall hearing of any on this forum.

It's probably just scaremongering. I've not had any problems with a crank drive / Alfine hub gear combination and I don't ever recall hearing of any on this forum.

We're talking about higher torque motors than yours. If you have a look on the German forum, there's a very long thread where people report their problems with their Bosch motors, and there's a few there that have destroyed their gears. The Tonaros and the Kudos Ibex are supposed to have more torque than the Bosch.

As I posted in another thread my Shimano hub feels like it is being pushed beyond it's limit by a Tonaro crank drive, time will tell I suppose.

Isn't this ultimately about the amount of power that the gear system is being asked to transmit? The torque is just a component part of power. Is the amount of power at the point of input into the hub gear system significantly higher with a Bosch + Rider and Tonaro + Rider than it is with a Panasonic + Rider system? If it isn't, I can't see what the problem is. Motor and rider generated torque about the chain wheel is translated into a linear force along the axis of the chain and then translated back into an angular force, or torque, at the rear sprocket which in turn is fixed to the hub gear input shaft. Thus, the torque into the gear mechanism can be varied through the use of different sized rear sprockets.

 

I still have not heard of, or can see what the problem is.

So you can't see why a kw would load the gears more than 600w? bear in mind both will have the same reduction, as cadence will be similar and final road speeds will be desirable in the same ranges.

You can't vary the rear sprocket without changing cadence which generally falls into a very small range.

In his OP, Dave from Kudos wrote: "...the cheap Shimano Tourney gears,these were rapidly destroyed by the motor..."

 

That looks like a problem to me.

Is the amount of power at the point of input into the hub gear system significantly higher with a Bosch + Rider and Tonaro + Rider than it is with a Panasonic + Rider system?

Yes. And Daves saying also with the Kudos motor. That's the problem.

So you can't see why a kw would load the gears more than 600w? bear in mind both will have the same reduction, as cadence will be similar and final road speeds will be desirable in the same ranges.

You can't vary the rear sprocket without changing cadence which generally falls into a very small range.

 

I said in my opening sentence that this is all about power, not torque. Torque is just one component part of power. Torque = Power / Angular Velocity (speed of rotation). So, yes I can see how 1 KW will stress the gear system more than 600 Watts, the above equation describes that relationship.

 

My point is if the power of the Tonaro Motor, Bosch Motor and Panasonic motor are roughly the same, I can't see what the problem is.

Yes. And Daves saying also with the Kudos motor. That's the problem.

 

OK. I thought the motor power output was roughly the same. I suppose if I put my 12000 mile Alfine hub on a moped, it wouldn't last long either. That's the problem.

No problem on Tonaros.If the Tourney gears aren't good enough don't use them!'

My point is if the power of the Tonaro Motor, Bosch Motor and Panasonic motor are roughly the same, I can't see what the problem is.

 

From what I've heard from impartial and very experienced people, the Tonaro is definitely not a particularly powerful system, torque is good and it climbs slowly, but it's no record breaker.

 

In contrast, when the Bosch system was first introduced in Germany it got a reputation for destroying chains very quickly, so it was modified.

 

Hub gear manufacturers are very sensitive about torque and have rules about how low a bottom gear is allowed for systems they supply, Shimano for example specifying the limits to the sprocket pairings that can be used. These rules are for unassisted bikes and it's possible to break the rules on those, so one can see how much more tricky it can be with assist power. Any long term regular reader of Velovision will also know about the history of hub gear failures on hard-worked unassisted bikes. Since the Inter hub series, Shimano have increased the diameter of their newer hub gears to increase the strength of their components and have twice modified their 8 speed for this purpose, the first modification specifically to address a series of failures after it's introduction.

 

Historically Shimano withdrew their 4 speed Nexus Inter hub specifically because they were being destroyed by the Giant Lafree's Panasonic unit, and that was the lower powered early unit without a high power mode. Once again this shows there is a criticality with power assistance through hub gears, as well as an additional wear problem on derailleurs. SRAM who have suffered a number of failures on their S5 and S7 gear hubs are currently replacing the entire range with new designs to be announced. They had introduced one new design, the 9 speed I-motion, but it only lived for a very short time before SRAM withdrew it from the market.

 

I love hub gears and overall prefer them, but they do have their limitations with power assistance that can make them very apparent. Some ask for evidence from the manufacturers, but Shimano in particular are very sensitive about failures and keep very quiet about them, so its not surprising that SRAM and Sunrace-Sturmey follow suit in this competitive market.

Hub gear manufacturers are very sensitive about torque and have rules about how low a bottom gear is allowed for systems they supply, Shimano for example specifying the limits to the sprocket pairings that can be used. These rules are for unassisted bikes and it's possible to break the rules on those, so one can see how much more tricky it can be with assist power.

 

That makes sense. I can see there only being a problem with high powered, S class, bikes or standard ones where the torque is multiplied by an inappropriate combination of sprockets.

The safest bet for a hub gear with power assist is the NuVinci CVT, far stronger than any other. By reputation the frighteningly expensive Rohloff might be a good choice for the well-heeled.

Now that I know this exists, I won't be happy till I've got one.

 

NuVinci® Harmony