pic: Wide base robot CAD

[Ether]

How much less motor torque does it take to just start rotating a wide trackwidth 4-wheel robot compared to a long wheelbase robot (all other things being equal). Say 30"x24" compared to 24"x30". Does anybody have any data?

[artdutra04]

1. What is the gear ratio for the drive base? Are the CIM shafts long enough to do what you propose?

2. Why is each wheel individually powered? If the gear ratios are what they appear to be (AndyMark CIMple Box), why not just mount that on the chassis and run roller chain to the wheels?

3. You should move your wheels to as close to the front/back ends of the robot as possible to lengthen the wheelbase. If you actually built a FRC robot with this drive base as shown, whenever you would rapidly change direction, at best the robot will tip enough for the frame will dig into the carpet momentarily, at worst you will entirely tip over.

[CNettles11]

Originally Posted by artdutra04

1. What is the gear ratio for the drive base? Are the CIM shafts long enough to do what you propose?

2. Why is each wheel individually powered? If the gear ratios are what they appear to be (AndyMark CIMple Box), why not just mount that on the chassis and run roller chain to the wheels?

3. You should move your wheels to as close to the front/back ends of the robot as possible to lengthen the wheelbase. If you actually built a FRC robot with this drive base as shown, whenever you would rapidly change direction, at best the robot will tip enough for the frame will dig into the carpet momentarily, at worst you will entirely tip over.

1) The gear ratio is the same as the 2011 KoP CIMple Box, The CIM shafts aren't long enough to use normal gears. I've been brainstorming a way to either have the gears cantilevered off of the CIM shaft somehow or to just have the CIM motors mounted over the frame rails instead of through the frame rails.

2)I was trying to save as much weight as possible in this design and calculated from the Autodesk Inventor material properties that it would be lighter to have a gear on each wheel instead of using the gearboxes.

3)My train of thought was that if this robot were to have 8 inch wheels on it instead of 4 inch wheels, the wheels would be touching the ground in the same place and there would be no difference between 4 and 8 inch wheels with this wheelbase.

This feedback is greatly appreciated!

[Ninja_Bait]

Originally Posted by CNettles11

3)My train of thought was that if this robot were to have 8 inch wheels on it instead of 4 inch wheels, the wheels would be touching the ground in the same place and there would be no difference between 4 and 8 inch wheels with this wheelbase.

This feedback is greatly appreciated!

First of all, the design has 4 inch wheels, so take advantage of it and give yourself some stability. Don't design a drivetrain for 8 inch wheels if you're using 4 inch wheels.

Also, even the 8 inch wheels could probably move outwards at least an inch.

On another note, make sure you don't block the fans on those Victors. I've never seen one catch fire, but I'm sure if they're too close there's a good chance of it happening.

Last thing: Is the frame 1/16" aluminum and do you plan to weld or use bolts and brackets?

[CNettles11]

Originally Posted by Ninja_Bait

First of all, the design has 4 inch wheels, so take advantage of it and give yourself some stability. Don't design a drivetrain for 8 inch wheels if you're using 4 inch wheels.

Also, even the 8 inch wheels could probably move outwards at least an inch.

On another note, make sure you don't block the fans on those Victors. I've never seen one catch fire, but I'm sure if they're too close there's a good chance of it happening.

Last thing: Is the frame 1/16" aluminum and do you plan to weld or use bolts and brackets?

That's true, I'll probably re-design it for more stability if there are ever plans to actually build this robot. The controls design needs more work and if it ever comes to life, I'll definitely have the victors spaced out. The frame is 1/8" aluminum and would be welded if the design ever takes off.

[Allen B.]

Yes, the victor fans should have clearance, but when spacing out the victors also take into consideration of the connections and accessibility of all of the connections. It would be easier to wire and trouble shoot. Also, is there any reason you decided to put the CRio on its side? If you had it vertical it does take up less of a footprint and lets you access ports from multiple sides easier.

[CNettles11]

Originally Posted by Allen B.

Yes, the victor fans should have clearance, but when spacing out the victors also take into consideration of the connections and accessibility of all of the connections. It would be easier to wire and trouble shoot. Also, is there any reason you decided to put the CRio on its side? If you had it vertical it does take up less of a footprint and lets you access ports from multiple sides easier.

The cIRO is on it's side due to the fact that I was aiming to make this drive base vertically compact. I've got the strangest feeling that this year will be a limbo year. The whole design will be reworked if it comes to fruition so that the robot can be built around the game strategy and not the other way around.

[John]

Originally Posted by Ninja_Bait

On another note, make sure you don't block the fans on those Victors. I've never seen one catch fire, but I'm sure if they're too close there's a good chance of it happening.

I have seen one catch on fire, this year. I don't think we ever learned exactly what the problem was, it had plenty of ventilation and the one we replaced it with never had any trouble. We might have just been running the robot for too long continuously.

The only other time i've seen a victor fail was when a piece of PWM wire broke of inside it and shorted something out.

[Chexposito]

Originally Posted by Ether

How much less motor torque does it take to just start rotating a wide trackwidth 4-wheel robot compared to a long wheelbase robot (all other things being equal). Say 30"x24" compared to 24"x30". Does anybody have any data?

i'm not sure, but i can tell you by my team's experience when we did crab drive, turning using the wide side as the front was a lot easier. i don't have any idea the numbers, but it was significant enough of a difference, however drop centers are the way to go

[JesseK]

Originally Posted by Ether

How much less motor torque does it take to just start rotating a wide trackwidth 4-wheel robot compared to a long wheelbase robot (all other things being equal). Say 30"x24" compared to 24"x30". Does anybody have any data?

My tool bases its equations off of another spreadsheet that broke down the equations in this whitepaper:

http://www.chiefdelphi.com/media/papers/1443

There's an equation at the very end to determine IF a robot will turn (Torque available > Torque Required) that's useful. Problem is, it's also dependent upon the X & Y locations of the center of gravity. To hold everything but the wheelbase itself equal, the c.g. placement would have to be the same proportional distance between the center of area and the edges of the wheelbase rather than the same precise distance.