Why no gearbox on ST2s or ST5?

[bluecat]

pinion gearbox and Gates belt instead chain and rear shifter. Often discussed here; today I've had a short chat with the Stromer chief engineer.

The main reason is the initial tension which the Gates belt needs. This force is so strong that the TMM4 sensor won't work anymore.

Some more only in german at stromerforum.ch

 

[Sonoboy]

Why do they have to rely on high tension on both the "power" side of the belt and the "return" section of belt? Could they not adapt a low tension return, as does the Riese & Muller Delite? Would this not allow the use of the dropout style torque sensor? See the attached photo above. The important thing when working with drive belts is the amount of "wrap" or interface of belt to the cog. As you can see, the R&M Delite achieves greater than 180 degree wrap with the addition of an idler pulley, and does not require high tension on both power and return sections.

 

[Sonoboy]

Upon further thought, is the Pinion gearbox available with a built-in torque sensor? Wouldn't this allow the use of a high tensioned belt as pictured by the OP, similar to a mid-drive motor? Maybe all this would have been a bridge too far for the Stromer design team and they decided to stick with the tried and true derailleur system. Just a thought.

 

[Sonoboy]

Ah, come on.. gauntlet thrown down. Doesn't anyone have an opinion on the relative weakness of the ST5 design? It's almost like Apple submitting three years of the same housing, with better innards, and calling it "new". Anyone? Let's mix it up.

 

[bluecat]

The bike in the pictures abvoe is from TdS. Their former motor supplier ran into bankruptcy. So, they were forced to build a new bike from scratch. The result is the "Speedster". Pricing around 6'300 CHF. It comes with an 558Wh / 36V battery and the frontlight is B&M IQ-X 100 Lux.

This is how it looks like:

Now, I'm ready to discuss about "Is Stromer design state of the art"?

 

[fxr3]

I'll take the challenge. Chains are more friction free requiring less power and the derailur has been around for 50 years- simple and proven. A sealed and lubricated chain would eliminate the cleaning and oiling(I think).
The 12 pack of gears stuffed in the bottom bracket would add considerably more complication(I think) and the belt requires more power to pull it around(I think). The 50 years of proof of operation is enough for me.