Building "Hard-Ox" the HW Robot.

[harry hills]

Oh no. Please no.

Only the dead can know peace from these puns.

[overkill]

Jamie: no more messing about in Jay's asstronomical build thread.

Ahem,

Now that's out of my system, I plugged all the known design elements into the EDT simulator and got these results:



This assumes 150mm wheels, 8:1 gearing, 24V with 'unlimited' current capacity and the full 110Kg weight limit. I used a Bosch 750 motor as I don't know which Movimotor is being considered - I hear its lower RPM, so maybe the gear ratio needs changing to get a decent speed. Hope this helps and if I can get more motor info, I can make the figures more accurate.

[overkill]

EDIT: Just saw the model number in another thread - with a 3,300 RPM speed at 24V, lower gearing might be advisable.

[jay]

So less teeth on the drive wheel?
Would different size wheels make a difference?

[overkill]

I would personally go for larger wheels rather than a smaller sprocket; you will get a larger contact patch on the arena floor and hopefully better grip with a larger wheel. What is your target speed and I can plug that into the simulator to work out a wheel size?

[jay]

I would personally go for larger wheels rather than a smaller sprocket; you will get a larger contact patch on the arena floor and hopefully better grip with a larger wheel. What is your target speed and I can plug that into the simulator to work out a wheel size?

Ive not really thought about speed, good acceleration, 15+ mph seems a good figure.

[jay]

Was going to be a trail and error type procedure ha...

[overkill]

OK, with the first set-up the theoretical top speed is only 7.1 MPH. If you double the wheel size or halve the reduction then the bot should top out at around 14MPH. The problem with that is the maximum tractive current (the current when the wheels just start to spin) increases to 230 amps. That's for both motors but half of that is still way more than the average current capability of the Roboteq, so its going to get quite toasty!

[maddox10]

Just to give a real world example.

Bullfrog uses Iskra 24V 1.2Kw 3100rmp motors, on 10S LiPo. Gearratio 20 to 1 with custom mod 1 gears -wider than standard- and a Foam wheel like Sewer Snake uses.

Top speed theoretical 11km/h. But it reaches it instantly and as an added benefit, we can use a Sidewinder as the current draw is low.