Were we ever limited on the amounts of non-CIM motor

[The Lucas]

If you are looking into designing a swerve drive with no prior experience, I recommend you check out the video of Team 118's crab drive presentation from the '09 Robotics Conference. It should show you the basics.

[NyCityKId]

Originally Posted by The Lucas

If you are looking into designing a swerve drive with no prior experience, I recommend you check out the video of Team 118's crab drive presentation from the '09 Robotics Conference. It should show you the basics.

Thanks for the link Lucas. I'm watching the video right now. I'm only 8 minutes into it and they're pointing out some problems that I over looked.

-Andre

[PAR_WIG1350]

Originally Posted by Al Skierkiewicz

Andre,
Make sure that you can live with the efficiency of the bevel gears.

Par,
Take a look at my post again, please.

I understand that you were specifically referring to motors mounted on the module it self, I was just clarifying that point for others who might have less experience with swerve drive and wanted a way around the rotary electric contact ban while still maintaining the unique capabilities of continuous rotation swerve drive.

[Al Skierkiewicz]

I was also referring to sensors mounted on the wheels, a convenient method of tracking robot movement for auto mode. Slip rings were legal in the past and may be legal in the future. Although cool in some respects, continuous rotation is generally never needed nor does it supercede the need to use inefficient bevel gears. Although they look good on paper, mechanical guys can discuss the unique problems with alignment and power transfer better than I can.

[NyCityKId]

How inefficient are bevel gears? I've looked it up and I keep getting a pretty big range (around 1-45% efficiency loss typically). What makes them inefficient? is it the quality of workmanship (i.e. how well they fit together) or is it just a flaw of the design and cannot be circumvented? I'm no mechanical engineer but it seems to me that if a pair of bevel gears a custom machined so that the fit together near perfectly then there should be very little losses. If anyone can explain this it would be greatly appreciated.

-Andre

[Mike Betts]

Andre,

When you stop to investigate, many gear efficiencies (or inefficiencies) may surprise you. For example:

The Globe motor (KOP a few years ago) had a 77% gearbox efficiency (23% loss). Granted, it was multiple stage (117:1) but it was probably better designed, integrated and implemented than anything you will accomplish in your school's machine shop.

Another example: A Globe gearbox/motor I used in another robotic competition last year (65:1 gear ratio) sported a gearbox efficiency of 66% (34% loss).

Also note that these examples were manufacturer's numbers and likely optimistic...

When we learn physics, we almost always "ignore friction". The real world never does...

Regards,

Mike

[SteveJanesch]

NYCK,

It sounds to me like you're attempting a really cool and ambitious development, which is great. It's the off-season, so don't let yourself be restricted by what's allowed in a particular year's KOP - this would make an excellent demo-bot. For turning, you could use 2 LH and 2 RH window motors, or four old Globe motors, FP's with transmissions, or whatever you've got in inventory. Learn as much as you can and have fun with it. Do keep in the back of your mind what restrictions you'll face with next year's KOP, but for now don't worry about it.

Also, if you plan to actually build a demo chassis, start working with a programmer or two on what sort of driver inputs (in addition to drive module sensors) that can be used/will be needed to control eight independent motors. Let us know how it works out.

- Steve