Designing a Heavyweight

[Max]

I remember once seeing a video or picture of a lifter grabber that used a single linear actuator so that it first grabbed with a claw then started to lift as it reached the end of its travel, I think it was feather but might not have been, have just spent ages trying to find the video again but can't find it! Does anyone know which robot I'm talking about ???

[maddox10]

2 machines spring to mind. Storm and Antrax/Draven

But a feather linac lifter/grabber, no idea.

[Anttazz]

Was it not a MW that Tom made. Voodoo maybe?

[Max]

Ah found it:

It was Marco's creation from back in 2009! Though I'm not sure if anything ever came of the idea. (Build diary here: http://www.fightingrobots.co.uk/thre...w-heavy/page2?)
Could be an idea to look into using a single hydraulic ram to power a combined lifter grabber, I beleive Kenny is selling some hydraulic pumps in the for sale section though they be slightly underpowered for a heavy but I'm not sure

[RogueTwoRobots]

Voodoo had that setup, using an electric car jack. Not sure if it's the one you were thinking of but same principle:

There's also Uberclocker in the US, and the original Storm, although that used two rams.

Also where would you get a suitable pump?

Andrew Kenworthy (Kenny) was selling some hydraulic pump/motor units a few months ago. 500W ones, good for 140bar, although you presumably couple a more powerful motor to it. The Big Nipper boys strapped a brushless motor on theirs for their featherweight crusher this year. Not sure if he's got any left, but fourth post down here: http://www.fightingrobots.co.uk/thre...parts-for-sale

EDIT: Been beaten to it on both counts!

[Anttazz]

The detail is your downfall here. Keep it nice and vague and do as little research as possible to get in there first

[supernova]

I'm not sure what you mean Anttazz...?

Do you think these pumps would work n a HW? they are 1CC/rev, and 2Kw

http://www.ebay.co.uk/itm/hydraulic-...vip=true&rt=nc

[RogueTwoRobots]

Think he was referring to me there. I spent so much time looking for the right YouTube videos that people had already posted replies by the time I'd replied and was therefore just repeating what had been said

[Eventorizon]

While we are on the subject of HW's, what ESC would you use to control the massive Ampflow A40-300's? [Link: http://www.robotmarketplace.com/products/0-A40-300.html
I would be over volting the 24V them to 36V, possibly even 48V if people think the motors can cope. First thought is a Dual channel RoboteQ of some kind, but what ampage is suitable? The motors say 340A stall but you never want to give them that power else they will just burn out, so is it best to go with the 150A Dual or can you save a bit of money and go with the 120A version?
[Link 120A: http://www.robotmarketplace.com/prod...Q-HDC2472.html
[Link 150A: http://www.robotmarketplace.com/prod...Q-HDC2450.html

[Rapidrory]

Remember that when you overvolt you're also supplying them with more current (V/R = I), so those stall current ratings will go up proportionally. If you have a controller with adjustable current limiting then you can limit it to around 150A as you say, which is well above the peak efficiency of those motors (around 40A) and still gives you about 3.5KW output power max (assuming ~70% efficiency at that power). Although, never having used a controller with current limiting, I can't say how effective it is at stopping controllers/ motors from blowing up; sudden changes in direction create current spikes larger than the stall rating, and I don't know if current limiting would react fast enough to prevent these..
The safest bet is obviously to go for a controller that can handle at least the stall current of the motor, if not more to avoid the current spikes from heavy driving (something like a Wotty, or a custom IGBT setup), however that's clearly more expensive..