Re: pic: Iso view
 

A few years ago, I was using 60% for what I called "working speed" (motor rpms at robot's top speed). The past few years, as our efficiencies have gotten better, this percentage of the free speed has gone up. Last year, we used 75%, I think.

I don't put too much faith in that number, though. It just gets us in the ballpark with regard to ratios, speed, and sizing. Our final number might have been 5% higher or lower, but it is about right.

John, you must have a very light robot or a very efficient drivetrain if you are running at 85% of your free speed.

Andy B.

Re: pic: Iso view
 

Andy, I assume you are talking about a dual motor (2 CIM and 2 Drill) drivetrain. The percentage is obviously significantly lower when you have half the maximum power. This question might also explain the discrepancy between John's and your numbers.

Re: pic: Iso view
 

Or... maybe I'm just wrong.
Thanks for sharing, Andy.

You heard it here first, folks. 70% is where it's at.

John

Re: pic: Iso view
 

Or you can measure the actual resistance force and use that to find your no load running torque to find the actual speed you are running at. John, you will find that you are probably closer to 80-85%.

Re: pic: Iso view
 

OK, I need to clarify my background. In '99, '01, '02, and '03, we designed treaded drive systems. These systems had much more drag and lower efficiency than wheeled systems. In '04, we did a wheeled system. I *think* that 75% was a good number for us to use, but I may be wrong. We did not do any after-the-fact testing to verify this number.

Also, Max has a good point. We used CIM motors and FP motors for our '04 wheeled drive base, so the CIM motor was doing the majority of the work on the system. Since we did not have two balanced motors on the drive system, this may be the reason that our "working speed" % number was lower.

If we used 2 equally powered motors, I can see this number jump from 75% to 80 or 85%.

Andy B.