Up the Ramp

[The Lucas]

As Al mentioned the chippies are designed for max power at high rpm. The chippies seem to lose power proportionally more than other motors as PWM values approach 127. In our 4-motor drive (drills and chippies) we noticed that at slow speeds (PWM values slightly out of deadzone) the the chippies would cut out and drills would continue to run. I think this is related to the easiness to backdrive the chippies, so it drives forward during a pulse and backdrives between pulses (or the pulse is not long enough to get out of stall). We corrected this in programing by giving the chippies a different PWM value curve at lower PWM values. Check the PWM values as supplied to the motors with DEBUG statements as previously mentioned.
Also check ur battery voltage. It may decrease significantly decrease during a match, draining ur power, especially if u have a 6:1 gear ratio. Last year when when MOEhawk was direct driving HI gear drills with chippies to match (we could drag race to goals in like 2 sec), the voltage dropped below 6v during the mad dash to the goals (it sent the controller into safe mode). After that dash the voltage would rise again but would still be a couple volts below starting voltage. If that is the case, I suggest u gear down like we did last year.

[Al Skierkiewicz]

What if all you had were the drill motors? You would be forced to figure out a way to use them. When the drive train is correctly designed, you can use the chalupas, FP or the drill motors (last year's or this year's) and still run without tripping breakers, at high speed and maximum torque for the motor.
From the spec sheets...
SB=376 watts out@9000RPM@ 56% eff. 398 in. oz.
CH=321 Watts out@2750 RPM@ 49% eff. 151 in. oz.

Fiqure out the torque on the SB if you geared it to the same speed as the chalupa. Take a look at the FP specs too!

BTW I mixed up the Bosch and Chalupa in my previous post. The above references are the correct relationship. The Bosch is the higher speed motor. Sorry for the mixup.

[Thunder360]

how fast were we going then, because we had to gear it down by using programing. We were able to switch between high and low speeds by flipping a switch on one of the sticks. We ran a Chippy to a 10 tooth gear connected to a 60 tooth on 8.5" wheels. We were 2 wheel drive, with the power to the front wheels, and casers on the back. So how fast do you think we were going. Ex: MPH or FPS also how many RPM's do the chippys put out?

[Joe Ross]

Originally posted by WakeZero
Just use the drill motors, they work great

assuming you ran them at the same RPM as the chipua's (4500/6 = 750 RPM) you wouldn't get enough extra power to make a difference. The problem was not the choice of motors, but the choice of gear ratios.

[Al Skierkiewicz]

Originally posted by Thunder360
how fast were we going then... We were able to switch between high and low speeds by flipping a switch on one of the sticks.

I am afraid you haven't given enough info here to determine what your speed was. How far did you have to reduce the speed in software, what was the low gear ratio RPM?
I can make some assumptions and give you an answer, although as an electrical guy I will defer to any mech engineer who would like to step in. Assuming your original design RPM was 4379, (the normal operating RPM from spec sheet) and that the motors could in fact drive the robot at that RPM. The output RPM of a 6:1 gear ratio would be 729 RPM. Coupled to a 8.5" wheel with a circumference of 26.69" at 729 RPM that is 12.15 Rev/sec times the circumference comes out to around 27 ft/sec. 27 ft/sec is more than double a good speed for both speed and torque in our designs. Most teams seem to go for 8-12 FPS. So you could reduce the size of the wheels or change the gear ratio.

[Frank(Aflak)]

gearing the chips down 6:1 is your problem. I mean, that gives you flat RPM's of close to 800 or so. with very little torque. We had ours geared down 60:1 or thereabouts. We were at stl also, maybe you saw us, team 1067, we flipped twice,

Well, we also use the drill motos in our drivetrain, but you needed to gear it down more.

[T967]

As a driver I noticed early on that our robot was extremely uncontrollabe on the ramp having trouble getting up without spinning out or not making it up consistently happened. However during auto mode it would perform fine!!!! So like some one said earlier the joystick/HUMAN DELAY was the problem. Our programmers killed that problem with the gyro. We use it to compinsate when ever we start turning too fast on the ramp making it easier to go up the ramp and even be able to turn on a dime, even when on the ramp. Conclusion your joysitck/human delay is the problem. Practice more or figure out a more controllable gearing for the robot.