FrontWheelDrive dual-hubbed KMX

[Jozzer]

Just use it alot, or let it get wet too often! ...the frame is real thin stuff. The most I have ever had it loaded was 35kg (bike, batts and motor), when it was carrying NiMh batts, i suspect this was when the damage was done. THese days it carries a 2kg A123 pack I weigh 80KG...

 

[geoff57]

hi all

The KMX frames is not sooo strong..mine snapped right in the middle (under the seat). THey fatigue very easily under a lot of weight, very thin steel.

I have a similar problem though mine has not snaped I found out before it got that far mine was caused by a combination of the frame being in 2 parts joining under the seat and the twisting force that is put on that by all the weight we pile over the back wheel.
The signs to look for are the frame cracking under the seat front of the seat attachment point where the front half is clamped over the rear half or rear forks, a crack start to form at the end of the clamp slot and slowly spreads round, as it starts from underneath you don't notice,I have come up with a soloution I have made a clamp out of two sheets of 6mm aluminium on each side with two bolts above and two below the frame acting as an external secondary clamp over the primary one which is the front frame.
This is not the fault of KMX
the forces we put on the frame are way out of what the frame was designed for!

KMX have now changed their design and done away with the two part frame and gone for a one piece frame this should make the frame a lot stronger for the type of motor setup that most of us go for.

 

[paultrafalgar]

Please forgive this diversion from your original idea of hub-motors on the front wheels, but I was thinking that you could use an AXI motor as Matt Shumaker did here viewtopic.php?f=6&t=3904. I wish I could draw it but I can't so here's an attempt at a description:
1. Fix one AXI motor above each KMX front wheel (on a strengthened fender - you might need a bowed-upwards crossbar tying the two motor together - bowed-up to avoid oscillating knees).
2. Let that AXI, through a very small "sprocket", drive a toothed belt.
3. Let that toothed belt drive a giant pulley, the same diameter as the wheel (20") and clamped to the spokes.
The AXI motor goes 10000 rpm so you need 25:1 gear reduction(?) - can this be done in one stage?
Whadyathink?

 

[Drunkskunk]

generaly, any gear reduction above 10:1 will be Very hard to turn for the wheel when the motor is off, or if you start going down a hill, or try to push the bike in the garage, ect. at 25:1 it would probably act like it's locked up, or nearly.

As an example, I have a 1 horsepower electric whinch on a track in my garage. it runs a 50:1 rediction to the spool, and can lift 900 pounds. when I turn the motor off, it will hold that 1600 pounds just fine. There is no cable lock on it. It was designed and sold that way. Only the resistance of a 50:1 reduction is needed to hold the cable and what ever I have suspended off it: Engine blocks, refrigerators, Couple of girls in rock climbing harneses hooked to it and using it as a swing. The binding force of high Ratio gears is a verey efective lock.

 

[paultrafalgar]

Doesn't that mean you just need a freewheel on the motor? Not sure if I understood you?

 

[kbarrett]

Most c'lyte brushless and gearless hubs ( and similar ilk ) add quite a bit of drag when the power is off.

No gears, so there is no way to use a freewheel to disengage the motor.