Advantage to six wheel drive?

[JamesCH95]

I've done a little math (pardon my mixed units):

150lb robot traveling@ 15ft/s has 711 Joules of energy

Six 1-foot axles of 1/2 in OD made from steel rotating @ 14.32 hz (15ft/s w/ 4inOD wheels) has 0.148 Joules of rotational energy.

If those same axles are moving with the robot @ 15ft/s they have 18.8 Joules of energy.

What difference does that make?

Rough numbers here:

Assume 500W power train (i.e. 4 CIMS with some inefficiency and non-peak power output slapped on)
Assume perfect traction

It will take 1.4220s to output a total of 711J, i.e. get a dead axle robot to 15ft/s

It will take 1.4222s to ouput a total of 711.148J, i.e. get a live axle robot to 15ft/s

The amount of rotational energy in the axles at full-speed is utterly trivial. If you need that extra 0.2ms to get to full speed... well... good luck. You could shave 0.03 lbs of static mass from your robot and break even.

I may have used rough numbers, but we're talking multiple orders of magnitude of triviality.

Bottom line: live or dead axle, it does not matter.

[lemiant]

Bottom line: live or dead axle, it does not matter.

It does not matter... as far as rotational inertia. I'm interested as to the effect of a large first stage gear like in the CIMple, gearbox

[JamesCH95]

Originally Posted by lemiant

It does not matter... as far as rotational inertia. I'm interested as to the effect of a large first stage gear like in the CIMple, gearbox

You can do the math too! I found all of the equations I needed from Wikipedia and Google does a great job handling units. Give it a shot.

[lemiant]

Originally Posted by JamesCH95

You can do the math too! I found all of the equations I needed from Wikipedia and Google does a great job handling units. Give it a shot.

Haha, I tried, but without knowing the dimension of the gear itself, I'm pretty much out of luck

[R.C.]

Originally Posted by lemiant

Haha, I tried, but without knowing the dimension of the gear itself, I'm pretty much out of luck

Thats also pretty easy to find. Open a cad model or look at the martin gears website. They have a pdf of physical dimensions for 20DP gears.

-RC