Power transmission (to wheels) methods ?

[CompoSimmonite]

I want to build an off road mobility scooter.
After trying my large Class 3 scooter on even gentle dry terrain I've realised only a specialist machine will do what I want to allow me to explore countryside places I'd previously been able to venture on foot. Rolling a 150kg machine over on an uneven path (not much fun) means a much lower CofG also required !
Taking the design a step at a time first thing I need to mentally work out is how to transmit power from a single electric motor to all 4 wheel (2wd and diff are a guarantee of getting stuck - as already been confirmed )
Motor in each wheel would be how I'd go with a commercial scooter design but that isn't an option for me.

So far I can think of chain, belt ( Vee and toothed), shaft and hydraulic. I though about a flexible shaft like used with drills, Dremel and such but can't find any made in large enough capacity for the torque required.

So other than chain, belt, shaft and hydraulic can anyone think of other methods ?

Cheers.

Paul H

 

[waddycall]

Gear?

 

[Freddy0309]

Most of the ones I've seen seem to have a motor for each wheel, I'm not sure if that's for ease whacking them in quantities or if it's simply the easiest/cheapest way (commercially) to do it. A friend of mine made one for a client and it was based on a golf buggy

 

[GW8IZR]

+1

four small motors will make life easier for you both mechanically and electrically

 

[knighty]

have you looked at electric bike wheels ? (the ones with a motor in the center)

they're bit tall but that would help over rough ground

and I'm not sure about the power output of the geared wheels, but some are geared so better for low speed high torque... 800watts/wheel should be no problem... and you can run much higher power through it if you want (I ran a 500 watt wheel on 3000watts for a long time no problems)

 

[WorkshopChris]

Have a look at standing power chairs. A guy at the farm has built a few variations for off road , will get some images next time i see him. Will watch this with interest as i have thought of something similar, will know in a few weeks if i am going to need to build one.

 

[CompoSimmonite]

I've bought a couple of golf buggies in the past for parts. One had separate motors for each wheel so no need to a diff. Other had a small Dana axle with diff that 2hp motor I'd like to use was attached. The actual axle was similar weight as the Marina item on my Marlin (diff had stripped gears anyway so got binned) !
Design speed will be a little over walking pace so around 3-5 mph max. Not sure if bike wheel motors intended for at least double that would have the necessary torque at lower speeds. Also 4 such wheels would be outside my budget as they are around £150 each for cheapest china can produce.
FWIW I used to have a little 125cc French Sans Permis microcar. It was FWD and driveshafts were modified steering columns together with the joints

 

[Freddy0309]

Could you not buy a cheap 4x4 or quad? Or maybe mount 2 motors, one on each axle?

 

[CompoSimmonite]

Could you not buy a cheap 4x4 or quad? Or maybe mount 2 motors, one on each axle?

4x4 quads are dear and banned from most footpaths etc I want to wander.
One thought is 2 mobility scooter transaxles with the front adapted to have steering swivels. After all beam axles work fine under my Disco and Mahindra

 

[gordon stephenson]

If the electric bike motors could be obtained at a reasonable price they could always be built into smaller more suitable rims

 

[Bill Edwards]

There's enough ways to get power to all four wheels.

Mount the motor inline with the axle and use a belt or chain to link them. Then use another (or if you're able, even the same one) to simply go the length of the machine to the other axle. As to steering for the front wheels, spider joints/UJ's are common and cheap, or if you wanted things a little smoother you could probably get CV joints cheaply.

If you have a straight run you could use a solid shaft to link the axles, but without two 90 degree gearboxes my thoughts on the easiest way to twist the drive is with V belts, they can do that.

I would perhaps consider some means of disengaging the front axle, assuming this will sometimes be used on hard surfaces. Not having any diffs isn't ideal but I can't think of any that are lockable and easily/cheaply available.

 

[normspanners]

how much off road do you want to go ?

or look at this guy near to us, for ideas http://www.dailymail.co.uk/news/art...ix-wheeled-electric-powered-HexHog-likes.html

 

[s410man]

I'd go for a small quad with the panels all stripped off and newer ones made half the size of a quad is usually panels to make it look beefier

You'd be suprised where a 2wd will go with a good set of knobbly tyres with weight above them..

 

[GW8IZR]

I'd go for a small quad with the panels all stripped off and newer ones made half the size of a quad is usually panels to make it look beefier

You'd be suprised where a 2wd will go with a good set of knobbly tyres with weight above them..

When is a quad a mobility scooter...? in my view (which normally counts for F all!) when its used by someone who needs a mobility scooter.

I *know* there will be ramblers that will moan like stuck pigs but a suitably modified (and ridden at 4 or 5 mph) quad would seem tio be a good starting point.

You see these small chain driven kiddy quad things second hand, that would be easy to gear down and make a good base vehicle.

 

[Tinbasherdan]

When is a quad a mobility scooter...? in my view (which normally counts for F all!) when its used by someone who needs a mobility scooter.

I *know* there will be ramblers that will moan like stuck pigs but a suitably modified (and ridden at 4 or 5 mph) quad would seem tio be a good starting point.

You see these small chain driven kiddy quad things second hand, that would be easy to gear down and make a good base vehicle.

I agree, there should be some sort of allowance for using a quad as a disability buggy, however the ramblers association and they're pet politicians would never allow it.
I've had walkers tell me (whilst in a registered landrover search and rescue ambulance, on duty) that they didn't agree with us being where we were and "could we not just use a helicopter" I've also been told during a discussion with a ramblers group that if you can't walk up the fells, you shouldn't be allowed up there and it's tough luck. The countryside is generally spoilt by the red socks and bobble hat brigade

 

[Tinbasherdan]

In answer to the actual question, I would go for a two motor layout and chain drive, one for each side and running on a skid steer principle. Also the 6x6 idea is much better for a vehicle with such a small footprint, and not a whole lot more work. I'd mount the front axle with a single pivot and the rear 2 in a walkin beam arrangement similar to the old scammells, that way you maintain a good amount of points of contact at all times

 

[CompoSimmonite]

In answer to the actual question, I would go for a two motor layout and chain drive, one for each side and running on a skid steer principle. Also the 6x6 idea is much better for a vehicle with such a small footprint, and not a whole lot more work. I'd mount the front axle with a single pivot and the rear 2 in a walkin beam arrangement similar to the old scammells, that way you maintain a good amount of points of contact at all times

Funnily enough this is EXACTLY what I've been thinking earlier. I have two golf buggy motors with controller that powers them together which could be used.
Miniature Scammell - I like it

 

[normspanners]

similar to the old scammells

would have though you knew the name, let alone know the rear suspension setup

 

[normspanners]

what about a double pivot and no suspension ie central pivot for the rear walking beam so it can articulate both ways and just use low ground pressure tyres ie 3-5 psi ala m/c trials rears to provide the springing the front axle would help maintain the level running then would have a tripod type stance but allowing the rear drive to do its own thing.
might need some gas type struts either side at the rear to help maintain the upright stance ??

 

[penfold]

From a simplicity/low cost perspective as well as avoiding the ire of the bobblehats, perhaps a motorised version of the mountain trike? I saw them on telly and they looked quite capable of dealing with unsurfaced roads and paths as long as there's not too many giant pot holes or tractor-sized ruts.