Front wheel hubs motors v's rear wheel

[Northern Irelander]

Is it fair to say, front wheel drive motors make the steering very heavy and have some under steer on the corners?

I have fitted a Powercycle puma motor to the front forks of a MTB

Before I respoke the wheel, trying to decide whether to fit to rear or front.

The rear will have to be very dish shaped to centre the wheel and allow 6 speed gearage.

 

[flecc]

A heavy and/or powerful front hub motor can make the steering as you describe and I personally prefer rear hub motors. The downside of the rear position is having to use limited choice multi sprocket freewheels instead of the stronger cassette system.

It's sometimes necessary to bend the rear frame a bit to accept a motor and 6 speed freewheel which usually exceed the normal 135 mm by quite a lot, but that's usually possible on a full size wheel bike. The dishing doesn't matter, it's quite normal for sport bikes with up to 9 rear sprockets to have the wheel very heavily dished, and my conversion of a single speed 20" wheel Quando to have 6 gears needed very heavy dishing as you see here:

 

[Mike63]

Front wheel drive was the biggest problem I found with the X6.
I found it impossible to hold it at walking speed, with my arm stuck out trying to make a right turn.
Very dangerous in heavy traffic and as such I came off a couple of times.

....Mike

 

[Tiberius]

I agree. A properly set up front hub bike can be perfectly manageable, but the rear hub is a better location for the weight and the bike will handle better.

In fact, if you went through the science of it and had to choose the two worst positions to add weight to a bike, you would come up with the front hub and the rear rack. Strangely, these seem to be the common places to put e-bike components.

I've also heard a theory that if something went wrong with the controller or the wiring and shorted out some of the motor windings, then the motor would apply a sudden drag and the end result would be worse with a front motor. I've only heard one report of this actually happening and that was with a very powerful motor.

I don't think there's a need to panic with the normal type of motor, but i do think that big, heavy, direct drive motors should only go on the rear.

Nick

 

[jerrysimon]

Interesting discussion and one which I suspect has been discussed here many times before, though being quite new this is the first time I have read about it.

I think the reason why many choose front hub installations is because its so easy and means you don't have to start messing about with rear gearing etc. Specifically for after market kits this must be the easiest method to add power to an existing push bike.

I guess the back panier tray is also the easiest place to put the battery and perhaps balances out the wieght with a front hub motor.

On my existing push bike having a back hub wheel and a battery and my panier bag for work would make the back VERY heavy.

Interesting comment about a front hub motor locking up

Some of these high powered 1000w front hub motors seem scary and I doubt I would ever fit one. With that power I would prefer a regular moped/scooter with the associated breaking and helmet that would go with it.

Regards

Jerry

 

[Straylight]

People here have also aluded to a possible lack of traction on steep hills with a front motor, being caused by the wheel lifting slightly. Of course, if the motor was really heavy, it'd probably compensate for this.

On the subject of batteries, I think there's a real gap in the market for a manufacturer to build a bare frame with a centre slot to carry a power pack (a la Wisper et al). There would, however need to be some kind of kit builders standard form factor for the battery case though...

 

[Northern Irelander]

Thanks all, some very good input and cool pic Flecc

The MTB has straight double butted forks (steel), these are going back to mid 90's, very strong and flexible, ahead of their time being one of the first straight forks for fast downhill competition.

There appears to be a lot of flex in the forks, with the hub on the front (bike upside down, just throttle)

I made a simple jig from M10 thread bar allowing me to widen the forks or frame at the rear to the precise size. easy to do

Edit - my reservation for the rear was I use double paniers usually quite heavy, just trying to distribute the weight, battery will deffo be mounted within the Main frame geometry

 

[flecc]

High rear weight and large panniers isn't a problem on a bike if it's fairly low. On my Q bike conversion, most of the bikes weight is concentrated on the rear wheel, the rear hub motor, the battery just in front of the rear wheel and my weight sat near to the rear as in any folder-frame small wheel bike. On top of that I use a car style rear centre balljoint towing attachment which carried the trailer nose weight, and all this on that heavily dished wheel seen above. After thioudands of miles there's been no broken spokes and not even a puncture on the Marathon Plus tyre. You can see what I mean here and also here, or the full story here.
.

 

[Pedalo]

The issue with controlability of front hub motors hadn't occured to me.

How heavy does the motor have to be before it becomes a real problem? Is it most of an issue with larger wheels?
Does added weight in front suspension forks have a similar effect?

 

[Barnowl]

No problems experienced with the Tongxin nano front hub which is a relative lightweight. Wheel size 700 X 32. I've never heard of the extra weight of front forks causing handling issues.

 

[flecc]

There's also no real problem with the popularly used Suzhou Bafang motors which weigh around 3.5 to 4 kilos. It's not just a matter of weight though, the diameter is important. Small diameter motors like the Tongxin and Suzhou ones keep the weight fairly central so the gyroscopic effect is small and handling is only slightly affected. Large diameter motors can have the weight at greater distances from the hub centre and have a greater gyroscopic force in consequence. This is what can upset the handling more and make the steering less responsive.
.

 

[daniel.weck]

Why not have both ?

2WD

 

[20 inch terror]

bet thats fun on snow and ice......i want one!

 

[Straylight]

With the pottential forthcomming regulation change to allow 500w e-bikes, do you think the point could be stretched to include 2x250w motor set ups? You could have one pedelec and one throttle to give a kind of boost function.

 

[flecc]

With the pottential forthcomming regulation change to allow 500w e-bikes, do you think the point could be stretched to include 2x250w motor set ups? You could have one pedelec and one throttle to give a kind of boost function.

Having two motors should be no problem, especially since we already have an EU legal two motor system,
the SRAM Sparc which has two motors inside it's hub making up the required wattage.
.

 

[eddieo]

I like the stand......

Daniel, have you time for these diversions...You do have a project to deliver

 

[Barnowl]

bet thats fun on snow and ice......i want one!

The thing is if you've got a front wheel motor hub rather than a rear wheel you've got 2 wheel drive. Leg power for the back and electric at the front. I was cycling last winter through the park and large pools of shallow (ish)water sitting on top of thick slippy bumpy ice. Great fun (especially with slicks!) and the 2 wheel drive made a difference.

 

[Northern Irelander]

Some very cool ideas there

I decided to go with the back wheelfor some reason I still can't upload pics to this forum?? EDIT -certain threads have the attachment paperclip, other threads don't have this option???

I won't disclose the topspeed on a public forum (throttle only, no pedalling) but I can tell now........ it's not 15mph (calibrated cycle computer)
the ickle 180w motor goes well, even before I add pedal assist.

 

[Northern Irelander]

Thought I would tidy this thread with the pics included (external link was removed)

I sized the 16" wheel against the 26" wheel, removed the hub and checked its clearance in the MTB frame.

Previously I had placed the 16" wheel in the forks, and at the rear.

Placing the bare hub in the frame was purely to give me an idea to the central line for the rim and subsequent spoke lengths, centre of the hub axle is 72mm, this was measured with verniers/calibers.

Note how M10 thread bar is used to widen the frame, controlled and precise, no need to wedge with 2 x 2 " timber

 

[Northern Irelander]

Once happy with the hub in the frame, I respoked the hub into the 26" wheel

I cut all stainless steel spokes (dremel) and re-threaded the ends.

Now with the pedal assist ring attached the motor is going much faster, a project well worth doing...makes a splendid mule