Instructables

Help for completion of Knee Walker Project ?


Hi Everyone

I have a problem with a project I started to overcome my unique disability , this project was to basically install low powered electric motor on a kneewalker so I could get assistance / go off-road , yet still use it manually if need be i.e. to get some exercise or more importantly if battery dies ( something I cant do with mobility scooter or wheelchair  )

The problem however is I cant do this myself due my disability ( weld it , use power tools etc ) so I had this person i meet on a another  forum who agreed to help me - but unfortunately he hasnt   - so instead I am trying to find a replacement for him or any one that is willing to help.

The motor itself ( Motor - MW12B GoldenMotor  )seems to work fine using a Lyens controller , but  unfortunately there is no direct link to the hub motor whose details are below.

Model: MW12B -- 12" Motor Wheel
Voltage:36V (Brushless)
Power Rate:250W
Weight: 4.8Kgs

You will have to got to the gm website on the link above click on hub motors and scroll down to find more details , including links to 3d drawings .

You can see the motor itself working in following videos that were posted by the person who still has it

video1
video2
video3

Due to the size difference of the wheel  ( 16" compared to the front 9" using MTB tires ) amongst other things, we were  trying to find a way to mount it that he suggested would probably involve having to weld on some strong rear forks from a bike  or perhaps something else.

Ive included the whole assessment / plan we did based on our mutual ideas and discussions below for reference, but Im afraid thats pretty much it , as I dont have any of the parts here for reference or than the basic facts .

If any ones interested in helping , or going me any advice Id be grateful for your suggestions , if any ones wants to offer their services at a price just send me a pm and we discuss things further.

thanks for listening , heres the assessment / plan I mentioned..


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I need to figure out a rough plan for the wheel mounting, plus brake mounting. We need to get disc and caliper. We need to figure out what front wheels, how to mount them, and how to fix the sloppy steering.

In order to go see a welder we need to know where to weld the dropouts, the caliper mounts, and what, if any welding to do at the front end.




Assessment

Frame - good, solid, heavy. bulletproof.

Wheels - strong, solid, better made with bearings etc better than expected. but hard tires are not nice, and wheels are a little too thin and too small. I expect its easy to get hung up on small obstacles.

brakes - crap. none existent basically. Just a bit of metal pushing on the tyre. Also the lever is either crap or a bit broken. need to inspect it.

steering - not very good but not crap. whole linkgae is a bit loose and wobbly, just held together by a few bolts. this means it has a fair bit of play in the steering. The whole thing with the bolts is that they have to be a bit loose otherwise the steering won't move. not a very good design. but it will do.

handlebars/stem/steerer - designed to be collapsible easily, which is good, but there is also excessive play in this as well. it will do but its not great.

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Thoughts....

Because there is four wheels, I found that on uneven floors (just around the front room the floorboards were uneven enough) one wheel is often off the ground a tiny bit. This would be solved by having 3 wheels or tyres with a bit of give in them.

I would not want to keep any of the wheels. I would want to replace the front wheels with something a bit wider softer and grippier. like scooter wheels or MTB wheels.

Brakes - the center of gravity is quite far forward. if it had brakes only on the front then i feel like it might tip over. then again, with the weight of the frame, the motor, batteries and person, maybe not. I will do some testing.

Motors - Golden has the 8" single sided solid tyre motors that would be the easiest conversion, but I don't like the solid tyres and I don't like having 2 wheels at the back. I already ran into my foot.

There is also the 8" double sided solid tire. This is not so easy either because it is the same size as the existing wheels therefore the axle would want to go exactly where the existing axles join. Could be done with cutting and welding but would be a pain, plus you still have the solid tire etc.

I held up a 12" dinner plate and I reckon it would not look so bad actually. I will take some pics tomorrow. It looks like we would need to cut off a bit of the back section and weld on some dropouts, a bit higher up and further in than the existing axle mounts.. It looks like it will fit under the knee platform ok as well.

Controller - because we may well end up with a motor that is not exactly right for the job, I think its all the more important we get a controller with some intelligence. Something programmable where we can set a low voltage, top speed etc. This leads us back to the GM controller, Lyens mini monster, or......I just thought, hmmm the kelly controllers are programmable - well they do a little controller that might be up for the job as well. In fact it looks the most programmable one so far.

It is the mini one next to the coke can here:
Hub & Wheel Motor Controller | EV Parts

They have one that does 12-24v for $79 or $99 depending on max amps. You can get it waterproof for an extra $19

http://kellycontroller.com/kbs2405120a1 ... p-499.html

It is fully programmable, see the software screenshots and manual here:

Kelly KBS controllers online demo/help-Kelly Controls, LLC

http://kellycontroller.com/mot/download ... Manual.pdf

You need a serial port on your computer to program it, if you don't have one you need a serial to USB converter. They sell one for $29.

Kelly are good controllers. I never thought of them until just now - I usually associate them with high power controllers for cars and motorbikes. When I used to work at Sevcon (who make argubaly the best...and most expensive...controllers you can get.)....kelly was one of the few competitors we kept an eye on.

If you look at the setup software, you can fine tune min throttle, max throttle, max amps, max speed, all kinds of things. It will be just the ticket for fine tuning.

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So...........

This would be my personal plan right now -

Electronics:

$115 Motor - MW12B (GM)
$98 kelly controller waterproofed
$29 Serial RS232 to USB converter (from kelly)
$20 throttle (max)
$20 ebrake lever (max)
$50 wiring, connectors, etc
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$332



Frame / Fabrication:

$50 old steel bike to steal dropouts off (maximum, probably less from craigslist or a garage sale)
$150 to pay someone to weld the dropouts on and maybe brake caliper mounts plus machine front wheel mounts if necessary for new wheels (maximum)
$50 (max) 2 front wheels MTB or scooter 8 inch with pneumatic tyres.
$30 (max) new axles, bolts, washers etc
$30 box for battery plus mounting bolts etc
$50 (max) for respray or powdercoat frame (will be messy after welding.
something to put the battery in
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$360


Brakes

$20 (max) brake disk for rear plus screw on adapter for rear hub Brake discs
$40 (max) brake caliper (cable ok, hydraulic not needed)
$50 bolt on brake caliper mount (seen them somewhere but can't find right now) price is a guess.
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$110


Battery

depends. I am clueless as to the requirements of this system. I can test with my own batteries once it is setup. Then we will know, but at a minimum you will be talking about 18 or 24v 10 amp hour. That is :
$199 from ping

Picture of Help for completion of Knee Walker Project ?
hele (author) 2 years ago
MATERIALS

I already have the motor , motor tester and knee walker itself as you can see on those videos - and getting the tires etc shipped shouldn't be a problem , so yes all the materials would be covered .

TOOLS

For the most part I would cover all required tools , the only exception being anything that was really outside my budget ie. welding equipment etc unless it was really necessary


It would also be helpful for any one interested to tell me what sort of experience you have , whether have you built any EV vehicles before , and how would you approach something like this in regards to what was already outlined & proposed , and of course your rates / price ?


thanks

hele
hele (author)  hele2 years ago
LATEST UPDATE

I have enclosed a pic below here of the same knee walker model I bought last year ( the one in the video as you can see was black ) , which I intended to use for this project.

Unfortunately , as I found out 2 wks ago, this along with everything else has been stolen by that person in the video ( http://www.facebook.com/mrjonathanmiles ) leaving me with $700 less and 8 months behind schedule.

As our agreement was based on faith - I have no evidence or proof so in all likelihood I will have to buy all , if not most of this again. ( provided I can find someone to help )

Signing off. h
$(KGrHqJ,!q!E-w+GYe,MBP)EHqZSmg~~60_57.JPG
Concept sketches ?
Location in the world ?

Steve
For clarification - I assume you are paying for tools/materials?
Kiteman2 years ago
(Moved to Community Blog to increase views)
hele (author) 2 years ago
NOTE**

Just an update to this I should of amended


Tires / front wheels

T2 9" MTB tires should fit into the frame using the same
bolt type that is already currently in the 8 " front wheels and the 12mm bearing converters i bought ( http://www.trampaboards.com/bearings-12mm-reds-conversion-spacers-p-484

Regarding the Videos Shown

The reason the wheel sounds loose was because it was just finger tightened and the phase and halls were not wired up properly yet - hence why it was running backwards .


The Steering

Tightening up the bolts we agreed was another issue because it would squeeze the linkages together so you couldnt steer.

To avoid this he suggested the solution would be to use some kind of thrust needle roller bearings and some extra metal or washers so the bolts could be tightened right up but still rotate.

http://www.vxb.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=bearings&Category_Code=ThrustNeedleBearings