Reliable High Discharge Lipos

[Eventorizon]

I don't know how long really. The maximum draw of each motor is 120A so the idea is to make all that power available when pushing and driving rather than being prevented by the limits of the battery and ESC's.

I the basic idea is to make the most powerful and robust full body hammer possible. But I have given over 3Kg to a small disc system so when brute force isn't enough we can turn around and use that.

Think a featherweight Tornado and then imagine what happens when you devote over a third of the robots weight to the motors and gearbox's in a featherweight. I think Tornados weight distribution was similar to that in its first iteration without the disc.

[mattsdragons]

Bloody hell, what motors are you using?!?!?!

[Ellis]

Why not make just that: a FW Tornado? Same weapon configuration and everything? Do it do it do it do it!

Also, as I am sure you are aware, power is useless unless it can be put down. I am assuming you'll deal with that with magnets?

[ewan]

You shouldn't be reaching anywhere near 1776W (120 x 14.8V) with even the most powerful featherweight drives - you're fundamentally limited by how much traction you can get on the floor as to how much you'll be able to use before you spin the wheels (unless you're using magnets?) - might be useful to have a play around with this http://www.architeuthis-dux.org/torquecalc.asp


edit: looks like someone was a minute ahead of me!

[Eventorizon]

Assuming I have set up the calculator right says that when I get to 30A of a possible 133A the wheels will spin. and I need 86 oz-in to spin the wheels or 6250g/cm... can someone explain what that actually means beside i have WAY to much power

[ewan]

There's some variables which you're unlikely to know with too much accuracy: the coefficient of friction of the tyres (which will be different on different surfaces) which obviously effects the point of wheel-spin, and also the inefficiencies in the drive-train (friction, heat etc.) which will add to power consumed when reaching wheel-spin. As far as your battery is concerned you only need to rate peak current at a little over the wheel-spin condition, the 'possible 133A' you mention is surely the stall condition (?) which you shouldn't be aiming to reach, the closer you get to it the more power you'll be expending as heat rather than movement.

[Eventorizon]

is there any real point in such powerful motors if I cant get the power down or can you put slick tyres on and the like to give more traction

[Max]

You could use tracks, depending on how you do it that could increase the friction giving you lots of power. But on my tracked bot the tracks slip on the ground rather than the motors stalling so still not enough friction on my design but that's partly due to the fact the bike tire I used wasn't very grippy and the lack of a wheel in the middle and suitable tensioning means in the middle of the track not much weight holds it on the floor.

[ewan]

The obvious thing you can do to boost traction is to increase the contact surface area by both changing the tyre material and wheel count. Think how Storm II is a 6WD machine with custom tyres specifically designed for the arena environment- specifically for this reason.
Although using a softer rubber compound generally helps, it's worth bearing in mind it can become 'gummed up' with dust and debris from the arena or just wear down too rapidly to be of any use. The orange banebots compound seem like a good compromise between wear resistance and traction from my experience, they're a little softer than the Robochallenge 'Blue' wheels but are not as wear prone as the (incredibly soft) green versions.
Other than that if you're aiming specifically for the Robochallenge arena magnets ought to be worth considering, though they bring their own complexities.

[Eventorizon]

I was going to use 8 of the green banebots wheels, but I know 30S is very soft, I had considered tracks but I know of now way to make featherweight tracks. it seems now that its not a question of power but a question of traction so now I just have to figure out how to maximise traction!

MORE WHEELS!!!