Mid drive motors and freewheel questions

[HoraceLai]

Hi,

I am looking into mid drive motors for velomobile purposes. For those of you who don't know, velomobiles are enclosed trikes/quads. Most of which have foot holes at the bottom to go reverse. Some of which uses a hub motor to reverse. However, since they tend to weigh 30kg-50kg and top out at around 50kph, a mid drive makes more sense.

Which is where my question comes in. With the dual freewheels of most mid drives, would this mean that it would not be possible for a mid drive motor to reverse the velomobile? My understanding is that there is a freewheel between the pedals and the chainring, and another freewheel between the motor and the chainring. So to me that means both the motor and the pedals can drive the chainring forwards but not backwards, so no reversing capabilities.

Compared to a hub motor, where the motor is directly connected to the tire, reversing on a hub motor would only mean that the chainring is driven backwards by the motor.

Am I correct?

Horace

 

[Warren]

Only a direct drive hubmotor will drive the velomobile backwards, if reversed. Geared hubmotors have an internal freewheel, which makes them easier to pedal when not powered, but will prevent the wheel from driving backwards with the motor reversed.

Are you planning to use the motor all the time, or are just looking for a way to get reverse without foot openings?

 

[spinningmagnets]

You might consider an independent friction-drive as a reverse, one that is lowered onto the top of the rear wheel temporarily. Even a tiny 40mm-50mm diameter RC motor with a cheap ESC would be adequate to run for a few seconds (without overheating).

 

[HoraceLai]

I would like the velomobile to be motorized both forwards and backwards if possible. If not then I guess a fabric covered foot hole is the next best thing. Other solutions I can think off add a lot of complexity and reliability questions.

It's too bad that only a direct drive will work for this. If i'm correct they tend to be geared for more high speeds, right? Velomobiles are heavy and have a high range of speeds which I think makes gear critical for the pedals and the motor.

 

[Miles]

You need a locking freewheel.

http://www.endless-sphere.com/forums/viewtopic.php?f=3&t=54599

 

[ferret]

You could do a mid drive with only one freewheel (for the pedals not the motor). With this configuration you will also be able to use regenerative braking.
The disadvantage would be motor drag when you are pedaling without power to the motor.

Avner.

 

[HoraceLai]

Are there any available mid drive kits that only have one freewheel (no freewheel for the motor to the chain)?

Would this add a lot of drag when neither the motor or pedals are being powered?

 

[ferret]

No off the shelf kit that I know of will be able to reverse (even if you replace the motor freewheel with a fixed cog).
You can't reverse a bike with rear gears because it will be like back paddling, the freehub/freewheel wont transfer power from the cassette to the rear wheel in the backward direction. Even if you somehow lock the freehub/freewheel, the rear derailleur will not allow proper chain tension in the reverse direction.

The only way to reverse is to use a cog fixed to the rear hub, this is usually done by bolting a cog to the disk brake mount on the left side and running a separate chain from the mid drive to it.

The drag in such a system depends on the characteristics of the motor and the gearing it uses.

Avner.

 

[Miles]

My suggestion would be to contact few ebike manufacturing factories in China, so to ask them if they are aware of a specialized maker of electrical powered enclosed trikes/quads.

I think suggesting to contact ebike manufacturing factories directly is bordering on the irresponsible... I wouldn't advise doing this except through a properly certified professional ebike procuration expert....