Kitbot/cims/transmissions running too slow?

[Paul Copioli]

I tested the living daylights out of that gearbox. I tested the 4wd configuration with 8 inch wheels and it behaved as expected (around 9.5 ft/sec). I use a closed-form non-linear differential equation to solve for position, speed, and acceleration over time and it tracked exactly with my testing of the frame.

What type of six inch wheels are you using?

What type of bearings?

How much chain tension do you have?

Something is not quite right.

-Paul

[Jim Zondag]

For the past several years, Team 33 has been able to get our robots to reach over 90% of the theoretical free speed. If you are only getting 60%, something is wrong. Easiest way to find it: remove the chip motors and check for friction. Without the motors in the system, everything should spin freely when you turn the wheels by hand. If it doesn't, figure out why.

[Swampdude]

6" skyway wheel chair wheels (usual kit stuff). Chain had appropriate slack. Also the bot didn't drift to either side when full power - it went straight. Indicating the fact that if there were something wrong it would have had to happen in both gearboxes, or at least one motor in each box. So I'm almost certain there wasn't a mechanical problem. I also don't think we happened to receive (4) defective cims. So if everyone is positive these cims perform 5300 rpm free speed. Then it really only leaves one conclusion, that the RC wasn't providing full power. We also had the old victors (883's?). Anyhow, I'll measure the voltage tomorrow and let you know.

Dan

[Swampdude]

Well I couldn't get there today, but I had Amanda check the voltage on the output speed controllers, she told me they were reading 12v on the output at full power. I also had her spin the drive wheels - spun freely. Gearbox is in good shape. So I'm out of ideas... I prefer my dew cold please...

I'll have to make a little video to prove it all, since I doubt anyone will believe me now. I guess I'll try a different method of testing the speed, but the last was pretty good, and the chassis is visibly slow.

[JVN]

Originally Posted by Swampdude

So I'm out of ideas... I prefer my dew cold please...

I'm stumped too.
Try switching the Chips... see what happens.

I'll bring you your dew in Atlanta.

JV

[Al Skierkiewicz]

Originally Posted by Swampdude

Well I couldn't get there today, but I had Amanda check the voltage on the output speed controllers, she told me they were reading 12v on the output at full power. I also had her spin the drive wheels - spun freely. Gearbox is in good shape. So I'm out of ideas... I prefer my dew cold please...

I'll have to make a little video to prove it all, since I doubt anyone will believe me now. I guess I'll try a different method of testing the speed, but the last was pretty good, and the chassis is visibly slow.

Dan,
There are several threads discussing using a voltmeter on the output of the controllers. Don't believe them. The true indicator is the LED on the controller. If it isn't at full red or full green then you are not at full output. Both motors are connected and wired to run in the same direction? Are you sure of your wiring? Four Chalupas in trouble are going to draw a lot of current and therefore voltage drop in the wiring. Do the robot wheels turn faster when you lift the robot off the floor? Might be some misalignment in the wheel bearings. Try raising the robot and bypassing the speed controller, running breaker out to motor direct. Do they spin faster?

[Swampdude]

First let me preface this by saying it's now going 8.5'/s

OK last night I got some answers, but it's still not clear. The original setup had the 2005 motors in it, and transmissions assembled such that they made a little noise but not bad. They weren't greased yet. Just a student slapped together out of the box kit. But from a distance it all looked right. So we performed the tests and it ran slow - 5'/s.

Over the last few days we removed the 2005 cims. Milled and faced off some gears and Also added a gear to mate with the FP's Then installed cims from 2003 and 2004. They now weigh 8.5 lbs with motors.

Last night I tested the output voltage to be 12v
then we put a zip tie on the wheel letting it whack a piece of plastic so it was loud and ran it for 20 seconds (up on blocks) with a stop watch. I counted in 4-4 timing marking on a sheet while keeping the beat (I gots rhythm). I counted 108 revolutions/20 seconds x 3 = 324 rpm at the wheel (and I got the same results twice). Which on a 6" wheel works out to be 8.5'/s

So what happened?
I did notice the students had the gearbox assembled incorrectly "After" the mods. So it's possible they we're incorrectly assembled prior to this and during the original testing. Also I saw that the cables were all hastily crimped loose and the connectors were not screwed tightly on the controllers.

Analysis:
1. Either our 2005 kit cims are bad.... Nah...
2. Our transmissions were assembled incorrectly.
3. Teenagers in a hurry wired it up.

Answer:
SLOW DOWN YOU CRAZY KIDS!!!!
Why are teens always in such a big hurry? Where's the fire? Why does everything always have to be done in a nanomicrosecond?
ok off my soapbox

After all this, we don't plan to use these on our competition bot. But it's turning out to be a great sparring/practice system.

[Greg Ross]

Originally Posted by Swampdude

we put a zip tie on the wheel letting it whack a piece of plastic so it was loud and ran it for 20 seconds (up on blocks) with a stop watch. I counted in 4-4 timing marking on a sheet while keeping the beat (I gots rhythm).

Ghetto!

[sirbleedsalot]

You say that you used the 6 inch kit wheels, but aren't they 8 inch. At least that is what our team got.

[Swampdude]

Originally Posted by sirbleedsalot

You say that you used the 6 inch kit wheels, but aren't they 8 inch. At least that is what our team got.

We've got 6" from years past kits. We also purchased a dozen from this past yard sale.

[Projectchon]

i'm not a pro, but this is what i'm going to say:
Temperature maybe is a small facter, but i think is the Voltage.
Did you change the pin inside the gearbox?