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jwatte
05-19-2014, 05:59 PM
I'd like to mount a motor with a 6 mm D shaft at a 90 degree angle (or 60-90 degrees, really.)
What's a good solution to transfer the motor power to the wheel? I have one motor per wheel, and need to move the motor out of the hub for space reasons.


I've looked at places like rushgears.com and sdp-si.com, and all the gears they have are $25 each and up -- and I need 10 of them! (It feels weird to pay more for the 90 degree joint than I paid for motor + encoder + gearbox...)


There are some plastic gears at sdp-si that are $6 each, but they are 1:2 and 1:2.5 ratio.


Or is there another choice for a 90 degree coupling than miter gears?

kamondelious
05-19-2014, 07:51 PM
How about a universal joint? I don't know what your options are like for something off the shelf, but I wager you could make something pretty decent.

Th232
05-19-2014, 09:00 PM
I'm not sure what space you do have, but is it possible to just offset the motor by using two normal gears instead of having a 60-90 deg turn?

jwatte
05-20-2014, 03:15 PM
is it possible to just offset the motor

I considered that, but couldn't see a way to make it work. The reason I want to move the motor out in the first place is to make more space; the suspension gets in the way in most directions.

I suppose I could go really far, straight up, and use a chain/belt drive, and suspend the motor straight above the wheel... That would add more sprung weight for the suspension, but maybe that's not so bad.

CasperH
06-06-2014, 09:26 AM
Would like to help, do you have a 3D design, or something with dimensions jwatte?

tician
09-08-2014, 01:28 PM
Although it is four months late (and 2+ months since jwatte was last active; it's too quiet now...), recent catching up on the projects of a builder of derpy electric vehicles and robots (http://www.etotheipiplusone.net/?p=3278) led me to search for replacement gears for angle grinders and other tools on amazon. Although the metal quality is probably not great and not all listings include size/tooth/shaft specs, you can find helical groove, bevel gear sets for <$10 each. Slipping sanity is making the temptation to build an EV of some sort rather unbearable, and PRS (http://www.powerracingseries.org/) sounds like an entertaining excuse to build a large-ish experimental (robot/human) platform.

Old post first started in May:
Since you already have a nice double wishbone suspension design on an off-road robot and electronics friggin' hate dirt and moisture, why not simply mount and seal the motors on the chassis and link them to the wheels with shafts and a pair of u-joints/cv-joints, like a traditional car/truck?

I've been somewhat working on a large-ish robot chassis similar to the amusing suspension of the 2CV but using belt/roller-chain shielded within the tube of the leading/trailing arms of the suspension. Will have quadrature encoders on the shielded shaft, maybe at the wheel but probably at the arm joint if using timing-belt or roller-chain, and likely add an absolute position encoder to determine arm angle for wheelbase/steering and quadrature encoder compensation calculations if I give the suspension a large range of motion. Definitely going for four wheel steering, and will at least be capable of four wheel drive for the lower unique part count.

Also, thinking of using the weight of the battery pack sliding inside the chassis to control pressure and fluid flow in fore-aft linked chassis suspension and orientation of electronics 'cabin' (basically mounted to chassis on a u-joint with multiple air springs), to prevent horrible pitching during rapid start/stop. During rapid lateral accelerations, the battery will slide a bit inside the chassis and cause restriction in fluid flow (should stiffen and partly decouple) until the battery velocity better matches the chassis velocity. Might need to add some sort of a correction system to maintain suspension compliance when driving on hills, although the acceleration from gravity on most drivable inclines would be quite a bit less than that experienced during rapid start/stop.