"scratching the surface"

[plargen]

yeh but i think it might need to be a bit steeper, it is probably a case of trial and error the get the angle right tho

[Jon Smith]

After a very long and useful conversation with Mario (maddox) and Ellis I believe I have decided on a drive system to use in my robot. The melty brain design will use these brushless motors: http://www.hobbyking.com/hobbyking/s...0KV_2665W.html
On a 1:4 gear ratio to banebots 98mm wheels

The ESC's will be http://www.hobbyking.com/hobbyking/s...Truck_ESC.html
To handle the breaking load.

I will use a 4s lipo for the power. Yet to be decided.

[Max]

Giving a top speed of 25km/hr! Sounds a bit too fast to me but I guess it is a melty brain style robot doesn't get too much stress so could be fine, I would gear it down a bit more though to give a lower top speed but that's just my opinion, I'd trust mario

[Jon Smith]

oh and im going to mount the motors the other way round so the weight is on the outside and the wheels are closer together giving a higher spin speed.

[SamO]

Sorry to hijack your thread, but...
I have been designing my next FW for a year or so now, and I have decided to go down the Hardox brick road (sorry big spinner guys ). I originally designed it to run off S900, but they have recently been discontinued, I then set out designing a brushless drive system. I later spoke to someone at the UK champs (sorry, can't remember your name) about brushless drives. If I remember correctly, he said that brushless motors don't like switching between forward and reverse too often. He said that he had tried and tested it, and it didn't work.

I don't mean to discourage you from brushless drive, but from what I can see, they seem to have some major reliability issues. Can any one else confirm/deny this???

[Jon Smith]

Really the load of reverse forward switching is place mainly on the ESC's as a power spike is produced so im using these ESC's that should handle the loads. Also as Brushless motors are not too expensive It shouldn't be much of a problem having to replace them. Of course there is a possibility that it completely fails and then I have alternate options.

[Jon Smith]

This is my drive system design still needs some work but should fit into my design without making too many problems

[Jon Smith]

Drive system.png

[archie2000]

Hi Jon,
Like the CAD design,
Just a quick question
Do you know if that brushless motor reverses or not?
Thanks

[harry hills]

Don't all brushless motors reverse?

[Max]

I believe all brushless motors reverse, it is only sme brushless speed controllers that don't reverse.

[maddox10]

Unless the brushless motor has a very rare way of windings on the stator, it can reverse. Just switch 2 of the wires. But, it's can't reverse when it's already running. It will just keep on running in the same direction.
So, the bright spark that tries reversing a brushless motor with an extra H-bridge on 2 wires won't enjoy an instant reversing motor.

[archie2000]

so a translating spinner/melty brain cant reverse?
couldn't it get stuck in the arena walls and floor without being able to reverse very well?

[Max]

It doesn't matter if it is a melty brain robot as the motors always spin in one direction and just break at certain points in each spin to make it translate across the floor. It only needs a reverse if you want it to spin in the other direction

[Jon Smith]

It will reverse very well just I would need to do a complete stop before reversing although if you get stuck as you suggest you are already stopped, so it shouldn't be much of an issue. I would aim to keep away from the walls of the arena as it is possible the contact would send me flying with the forces my robot will put out, Therefor it would possible to end up outside of the arena.

One key feature of my design is that the whole weight of the robot is its weapon, and the new concept allows for two ways of attack, either spinning one way to hit the opponent with a wedge to flip them or in reverse where I would give armour penetrating blows with the spike. If someone's using 4mm Hardox or titanium (anything equal or higher strength) armour I would not use the spike because it would have little effect.

I also have a wide range of control options for my robot as the Arduino is what controls everything on the robot acting as my failsafe and translation controller giving me the ability to program in a feature which prevents the motors from reversing until stopped.

Overall the design is a "New" and more complicated "electrically" than other robots although "Mechanically" it is simple.