Electric go-kart build from Jazzy 1100 mobility scooter

[Page]

I have a jazzy 1100 power chair that I restored for a family member who no longer needs it. I've tried to sell it, but cannot get an offer that would even cover the new batteries, so I picked up a go-kart frame, and am looking to power it with the chair. So far, I've figured out that the motors top out at 116 rpm. The kart has a 1" diameter rear axle with a worn 72 tooth sprocket and band brake on it. The chair spindles are 7/8" diameter on the round sides, and 9/16" on the flat sides, where the 13" wheels bolt on. My intentions are to weld the motor mount parts of the powerchair chassis to the go-kart chassis. I am trying to figure out
1.) Should I leave the motors mounted as is, with the drive spindles facing outwards, which would require a drive sprocket for each spindle, or should I switch the motors in the chassis, so that the drive spindles face each other, then connect them together with an axle and single drive sprocket?
2.) All the examples I've researched are using high RPM motors, and thus have small drive sprockets with large driven sprockets. With the low RPM/high torque setup I'm using, I'd have to go opposite on the sprocket ratios. Just throwing numbers around, if I did my math right...a 72 tooth drive sprocket connected to a 13 tooth driven sprocket (1:5.54), and a 13" tire would get the kart to 23.73 MPH (plenty fast for my 9 & 11 year old). Would I be asking for a bit much in the torque dept, or would it work?
I just have not seen any examples of a build using a powerchair mobility scooter...using sprocket size to achieve speed, versus quadrupling the batteries or designing new controllers. If it would work, I'd just use the motor controller on the chair, and limit its movement to forward and reverse. Any input?

 

[amberwolf]

1.) Should I leave the motors mounted as is, with the drive spindles facing outwards, which would require a drive sprocket for each spindle, or should I switch the motors in the chassis, so that the drive spindles face each other, then connect them together with an axle and single drive sprocket?

If you are paralleling the motors, then you could lock the shafts together with one sprocket.

If they're going to be independently controlled, you could independently hook them to each driven wheel (which would require altering the kart drivetrain).

2.) All the examples I've researched are using high RPM motors, and thus have small drive sprockets with large driven sprockets. With the low RPM/high torque setup I'm using, I'd have to go opposite on the sprocket ratios. Just throwing numbers around, if I did my math right...a 72 tooth drive sprocket connected to a 13 tooth driven sprocket (1:5.54), and a 13" tire would get the kart to 23.73 MPH (plenty fast for my 9 & 11 year old). Would I be asking for a bit much in the torque dept, or would it work?

It might work fine, but you may have to use some form of cooling for the motors (fans blowing on them, etc). These are brushed motors running thru their own gearbox, so you lose some power in that gearbox, and it gets warm, and the brushed motors themselves also get warm.

Since they're meant for powerchair use, meaning sealed up against environmental contamination/etc., they don't have as good a way to cool themselves off. They're typically only 300w motors (600w for the pair), though some of these units have 600w motors (so 1200w for the pair)

If you find heat is a problem, you could open up the motor casings and ventilate them, first taking the brake unit off the end of the motors (which you want to do anyway, so you don't have to power the solenoid wires in them to keep the brakes turned off), then opening that end up and hten adding some slots in the casing between the magnets down near where it mates to the gearbox.

I considered doing that when I used this type of motor on the early CrazyBike2 drivetrain, but before I got that far I switched to hubmotors for other reasons.

 

[AussieRider]

G'day Page.
Once again, Amberwolf is quick & generous in sharing his knowledge.
A couple of points though.
If you're going to use the same battery & controller from the power chair, I don't think you'll have any heat issues.
If you remove the brake from the end of the motor & disconnect them from the controller, the controller won't work & will throw an error code. Not that it can't be done. I built a mid drive Ebike with a power chair motor / gearbox & mobility controller. The controller programming was altered by disabling the "brake test" parameter.
Or, you could provide a 50 Ohm load across each brake connection on the controller.
If you had each motor driving one wheel, you could use one of Amberwolf's ideas of linking the left / right pot of the joystick to the steering to aid cornering.

AussieRider.