[FW] Hydraulic Crusher Bot

[Giles]

Me and a work buddy, Dave, are working together on a featherweight for the champs in April. We're going to post our progress here, will probably just be working on spare weekends up until the event.

Here is a very rough idea of the kind of design we are aiming for. Nothing is set in stone yet, just trying to think of a shape that works, and this is our best effort so far:




We're going to be running two Satern-16's with 775's from Ranglebox with a belt driven 4WD setup. Powered these things on for the first time on Saturday and they are absolute beasts! Can't wait to get something driving around on them.

For the weapon, we're using a hydraulic pump from a convertible car roof. This pump is nice and compact, with the motor, pump and reservoir all combined into one block. Spent the weekend figuring out which valves and wires do what, it works in a strange fashion, with different flow directions controlling different outlets. It works a treat though, one ram had no trouble lifting a fully grown man off the ground, and we plan on using two of them

We used a pretty ghetto set up for testing... a computer power supply with all the wires soldered together and croc clipped onto the motors!



That is all for now... more soon!

[Gabe01]

What car is the pump/motor combo from? Looks good btw

[Giles]

It's out of a Mitsubishi Colt, not sure which exact model as we just got it from Ebay. Weighs 2.5kg in total for the motor, pump and res. Good bit of kit!

[shakesc]

thats a good find, will watch with interest

[maddox10]

Should look into that.

[harry hills]

Agree the saturns are phenominal. They made my robot scream around on 60mm wheels and were good as new after a spinner hit pretty much wrote off the frame.

[cavecrusher]

It's out of a Mitsubishi Colt, not sure which exact model as we just got it from Ebay. Weighs 2.5kg in total for the motor, pump and res. Good bit of kit!

Those pumps, using a quick google search, are good for 1750 PSI max.

http://www.jagrepair.com/HydSystemEvaluationXK8XKR.htm

[maddox10]

Still 120 bar tough. A 32mm bore ram will develope 1 ton of force on that pressure.

The main question, how much oil is in that tank?

[Giles]

I'm not sure what the norm is for feathers, but that seems pretty good to me? With our two 20mm bore rams we should be pushing out around 700kg of force (Force = Pressure * Area * nCylinders).

The tank is pretty small. Doesn't seem to require much liquid. Once we remove two of the rams (it currently has 2 big and 2 small rams, we only want the big ones), then we'll be saving even more fluid.

[Eventorizon]

Hmmm, this is looking very good! Little Nipper came 4th this year so Crushers have their place. I'm sure it will produce enough forced to scare off most opponents.

[Gabe01]

if you're going to use the rams it came with, I think you'll bend the rams before you bend hardox. get yourself one fat ram.

[maddox10]

Crusher norm for feathers. No clue
Ram power ain't the main thing. Pressure on the tip is what counts, combined with the shape of the tip.

Also, stroke and speed have their place.

The 20mm rams, what stroke are those? If the stroke is longer than 40, the forces impared in robot combat will bend the rods.

On the other hand, Tiberius uses a 70*148 ram, with a 20mm hardened steel rod, and it seems it's still going strong, even build by me in 2003.

[Giles]

Hmmmm yes the rams are extremely light, which leaves me to wonder what they are made from... The big rams have a stroke of 140mm, was planning to use these on a 3:1 lever ratio to help with grabbing speeds.
Will look into sourcing a single, fat ram. 32mm would be ideal. I'll see if anything crops up on ebay that will fit the bill.

Is there a standard in how to prevent the pump from overworking when the ram is at its full extent? The rams i'm using at the moment are sensored, but I can't imagine many second hand rams on Ebay having such features.

EDIT:
Something like this seems to fit the bill.
http://www.ebay.co.uk/itm/Flowfit-Hy...item3a7cb3126c

[maddox10]

That one will be heavy.

To avoid burned out motors or burst parts, an PRV or current limiter is in order.

[Giles]

Just wanted to test out the rams/pumps under load to make sure everything worked as expected. Seems to be working fine. Will need to explore the strength of these rams though until I can find a good 32 bore one which isn't too heavy (suggestions anyone?)