4mph v 8 mph mobility scooters

[Cornishman]

Am I correct in thinking that, apart from the hign/low switch and controller, a different motor is used on an 8mph scooter as opposed to a 4mph one?
I have two axle units, one from a 4mph and one from an 8mph scooter. They appear to be very similar in gear ratios, so is the speed difference obtained by using different motors?
I have built a minature Landrover using parts from a couple of scooters, and, even though I have a high low switch and suitable controller,I can only go at 4mph in high speed. I am wondering if I am using the wrong axle/motor combination.

Can anyone please advise?

[Burgerman]

It makes no sense to build an 8mph scooter and limit it to 4mph electrically. If its gearing is adequate for 8mph it will suck double the amps from the battery at every speed as it would if it was geared for 4mph. And would be limited to half the torque at the same time. So requiring either batteries that were double the size, or have half the range. To get torque back to 4mph level, you would need a more expensive higher amp controller, thicker cables, and a bigger motor that took twice the amps.

So I suspect you have 2 of 4mph motor/axle combos.

Hi/lo isnt something I came across.

Its true that you could take an 8mph scooter, and program it to do 4mph. But thats economically daft. And adds weight/battery capacity that wasnt needed if it was built as a 4mph one to begin with.

[woodygb]

Difficult to say.... the motor on the faster axle is usually of a higher wattage output and the axle ratio is often changed ...sometimes in combination with a wheel diameter increase... to obtain a higher mph.

In general a motor rpm isn't increased to obtain the faster speed.

So your low is 2 mph and your high is 4 mph? ...rather than the switch making no difference?

[woodygb]

Its true that you could take an 8mph scooter, and program it to do 4mph. But thats economically daft.

And they are in fact fairly common as an ON PATH ( 4 mph limit ) or ON ROAD ( 8 mph ) option , just flick the switch.

[Cornishman]

Yes low 2mph high 4mph. I have an axle from a 4mph scooter and am using an S Drive controller, and was going to swap it for an 8mph one hoping that the motor and gear ratio was the difference. I am using an S-Drive controller which allows me to use a high/low switch.

[woodygb]

I'd suggest that you do so.

[Burgerman]

And they are in fact fairly common as an ON PATH ( 4 mph limit ) or ON ROAD ( 8 mph ) option , just flick the switch.

Yes but thats an 8mph scooter with a "slow" switch!

A real 4mph scooter, built with 8mph parts and programmed to go 4 makes little sense.

[woodygb]

AH! Gotcha!