Two hub motors on trike - how to set it up?

[Morten]

Hi all,

I’m new to this forum. Have been reading up on some of the threads – great stuff in here, so much useful information.

Now to the point:
I have a trike similar to this one: Cattrike, Road (http://www.catrike.com/catrike_road.html) and I’m planning a conversion to an electrical bike with some other modifications to the bike aswell.

What I am going for is:
Internal hub gear (Shimano ALFINE (8 Speed), SRAM i-MOTION 9 or maybe Rohloff Speedhub 500/14 (14 Speed).

So with the internal gear, which is a must, I would like to mount two hub motors in the two front wheels.

We have a legal restriction to 250W electric motors in my country. But the peak can be higher I guess.

My question is:
Which kind of hub motor to choose and which specific model could be an option.
Direct Drive vs Geared?
Which hub producer and where to order?

I will also add space for extra luggage so I can transport up to 70 kg extra weight.
Normal driving: Around the city with many stops and accelerations- the city is relatively flat, some small hills but nothing major.

Hope to get some feedback and a discussion going.
Looking forward to hear from you.

 

[SamTexas]

Welcome to ES. I am interested in the answers too.

 

[Drunkskunk]

Welcome to the forum. That's a good looking bike, and Catrikes have a great reputation.

adding front hub motors to that bike will be nearly impossible without access to a machine shop and some fabricating skill. The axle of a hub motor are are part of the motor and designed to stick out of both sides of the motor and into the dropouts of a normal bike's frame. The axles of the front wheels of a tadpole style trike are part of the bike, and fit through the hub.

The only direct drive motor I know of at 250 watts is the Crystalyte 20X. Its discontinued, but I've seen some vendors still selling it, and at one time crystalyte had a version of their 40X motor that had the axle you would need (also discontinued). Not directly compatible, but since the design is similar, it is a good indication that a custom axle would be successful.

A geared hub has a more complex axle. it might be possible to build the custom axle needed, but would involve a lot more work, and more parts than just the axle.

Once you solve the axle issue, you'll have a rather complicated throttle balance issue. Since it's front wheel drive, you'll have torque steer unless you can keep the throttle perfectly balanced

The best option would be to run a rear motor. You won't need more than a few gears once you have a hub motor. But if you insist on running an internal gear hub, then your next best option is a chain drive motor.

 

[The fingers]

My dream bike is a tadpole tryke!

 

[JEB]

I have 3 tadpole trikes, they are all rear wheel driven, very happy with the drive system, in my case there is not enough weight on the front wheels when making a turn. (at least one)

 

[dogman dan]

Shucks out of luck. Go mid drive, or stick with derailur on a regular rear hub. If you had two front forks on a tadpole, then you could simply have two front hubmotors.

To do it with what you have, you'd have to make new axles for your hubmotors. ones that would be similar to what exists on the bike. Might mean the stators would be basicly permanently part of the bike if the existing axles weld on. So to remove a wheel, you'd pull the rotor off the hub, leaving one cover and the axle and stator still attached.

Lotta work to keep from having a derailur. Especially when once you have a big motor, YOU WILL NEVER SHIFT THAT BIKE AGAIN.

 

[docnjoj]

I've build a bunch of tadpoles and now have a store bought one. Either way you need a rear motor or a mid-drive of some kind. Check out Rassy's mid drive trike. Way cool and lots of torque. Good luck with your project.
otherDoc
edit: I actually shift quite a bit but only use the rear deraileur, unless the battery dies. Then it is good to have some chainwheels too!

 

[biohazardman]

I have seen the single shaft motors around now and then if you are talking about a hub motor in each front wheel. Some research may get you what you are after. http://www.hs-escooter.com/sdp/1012764/4/pd-4958252/7927584-2261363/16inch_Single-shaft_out_hub_motor_E-bike_hub_motor.html You will need to balance outputs, two controllers and plenty of werq to do it but it's not impossible.
Nice trike by the way!
Good luck

 

[amberwolf]

Golden motor makes some small low-power wheelchair hubmotors with single-ended axles. You might have to run them at a fairly high voltage to get any speed out of them, but they should work for your application.

Their site doesn't appear to allow direct linking to any specific product, so you'll have to just go to the page and scroll down for it.
http://www.goldenmotor.com/wheelchair.htm
This is a link to the dimensional PDF:
http://www.goldenmotor.com/wheelchair%20motor%20drawing%202009.pdf