Powerful Hub Motor with Front Derailleur Only

[wturber]

On top of that, rear derailleurs work lots better than front derailleurs. For equal component quality, setup, and maintenance, the rear will always shift better for longer.

And while I'm not sure, my impressions is that front chain shifts can put more strain on a chain the rear ones. Though that impression may be colored by the recent chain break I had that occurred while doing a front chainring shift.

 

[Chalo]

And I want to ditch the rear derailleur.

So you want to be rid of the rear derailleur itself, or just not have shifting there? A short cage rear derailleur used as a tensioner is a great way to provide chain tension and to make your bike tolerant of imperfect chainline.

I think of Pinion gearboxes the way I think of Rohloff hubs (and I own a bike with a Rohloff hub): they're an incredibly expensive way to get most of the functionality of a derailleur system. The fact that the Rohloff hub system has its own dedicated chain tensioner for vertical dropout bikes that looks like a little derailleur and costs as much as a pretty nice derailleur really bears out this point.

I can imagine using a hub motor with a single sprocket, and using three front chainrings (with front and rear derailleurs) to give me three useful speed ranges to work with. But at this point I don't know how the expense and non-interchangeability of a Pinion gearbox could possibly be justified unless one has so much money that the expense is insignificant.

 

[HDMW]

Hello Chalo :
Thank you for your ideas.

So you want to be rid of the rear derailleur itself, or just not have shifting there?

I had three chainrings and a wide range derailleur on my HPV FS20. The latter was close to the ground and of course it picked up a lot of dirt. And I wanted to avoid maintenance and adjustments.

A short cage rear derailleur used as a tensioner is a great way to provide chain tension and to make your bike tolerant of imperfect chainline.

You make as convincing argument in your last two paragraphs as well. The setup would be entirely maintenance free on a bicycle with horizontal dropouts. On a trike the chain tensioning is the problem. There seems to be no way around a tensioner.

This is what I simulated at Grin. eZee 350 rp, 48v 23 Ah, 25A controller.
I chose wide gearing on the FS 20 because there was no electric assist. Would the short cage rear provide enough gear range for PAS up to 47 kph?

Regards : Hubert Wagner
France

 

[Chalo]

Would the short cage rear provide enough gear range for PAS up to 47 kph?

A short cage front derailleur has about 29 teeth of capacity. You can use this link capacity in the front, rear, or both. On a road bike, it would typically be divided between a 53-39t crank and a cassette of 12-27t or 11-26t. That would work for your trike, but the rear derailleur would need to be attached to a shifter. At 47 kph in the top gear, you'll be pedaling at almost 110 rpm. That's because your drive wheel is small.

If you used a modified wide range front derailleur, you could use a triple crank that uses the entire rear derailleur capacity, as long as you only have one sprocket in the rear. So as an example, you could use a 53-34-24 crank with a single 16t freewheel in the rear. The same 110 pedal rpm will only get you about 33kph in top gear.

It's relatively easy to find chainrings up to 60t, and harder but still possible to find 64t rings. Even with these large rings, using a single freewheel won't allow you to pedal fast enough to maintain 47 kph. So you'll need to use a multiple freewheel that has an 11t small sprocket, and at that point you may as well use an operational rear derailleur.

The small diameter drive wheel of your trike limits the top speed you can attain with normal bicycle gears. It might be worthwhile to look at the Schlumpf High-speed Drive that has a 2.5:1 overdrive built into the crank. Then you could use a moderate chainring like 39t, but have the equivalent of a 97t front ring when you shift it to the high gear.

 

[amberwolf]

So you'll need to use a multiple freewheel that has an 11t small sprocket, and at that point you may as well use an operational rear derailleur.

If a 12T is small enough, they make those as singlespeeds:
https://endless-sphere.com/forums/viewtopic.php?f=2&t=67833&p=1237062&hilit=freewheel+mxus#p1237062
The one I have came on the used motor so I don't know where it originally came from. IIRC someone else has a 10T or 11T in this same design, but I can't remember the thread it was in, and a search didn't find it so I might be misremembering.

Cant say how durable they are; never used mine (need bigger ones rather than smaller for my purposes ).

 

[HDMW]

Hello Amberwolf and Chalo :
I'm persuaded by Chalo's argument. It's pointless choosing an expensive gearbox instead of a rear derailleur when the trike will require a chain tensioner.

I'm looking now at the Heinzmann Direct Drive which means I can have a torque sensor. The voltage is 36 rather than 48. I've requested data on the motor, battery and controller from a Heinzmann agent. I'll plug that into the Grin simulator to see how the DD compares with an eZee with the 48v battery and a 25A controller I looked at.

And of course I'm keen to hear the forum's opinion of the Heinzmann DD.

Sanity seems to be returning among EU agents for these motors. The agent I spoke to said he could reprogram the controller to deliver a speed of 50kph. I guess that would be only for a few seconds. However, if I can get up to 40 kph on the flat I'll be satisfied.

I guess I'm making progress.
Regards : Hubert

“The lyf so short, the craft so long to lerne…”
Geoffrey Chaucer