Can you heat a co2 ram ?

The system Andy is running doesnt have any small bore pipes in it. The connection between the bottle, valve and buffertank is a solid ali bullet, finned for more heat exchange surface.
The smallest bore after the flow restrictor/liquid stopper is 13mm.

The flow restrictor between bottle and collector stops any liquid CO2 entering the system.

The flow is the reason for the chilling, and restrict that flow you degenerate that system from powerfull into mediocre.

Quotes from my CO2 page.

With a gas fed source as the pressure drops in an orifice, liquid droplets nucleate and the percentage of liquid increases. At the interface between the liquid-gas and gas-solid regions (near 80 psi.), all the liquid converts to solid - yielding about 6 % dry ice.
With a liquid fed source as the pressure drops in the orifice, gas bubbles form and the percentage of gas increases until the gas-solid boundary is met. Here, the remaining liquid is transformed into solid - yielding about 45% dry ice.

So.......If you use compressed co2 in liquid form and utilise the gas that boils off from it ...then your containing vessel , bottle or cylinder will get cold .....if you exceed the ability of the bottle or cylinder to warm back up by absorbing heat from its surroundings then the pressure will drop and the contents may freeze.


I attempt to keep a majority of heat transfer freezing in the main tank and buffer and away from the ram using a combination of a main tank inverted dip tube a restricted or slow buffer refill of say around 2 seconds ... and a thru buffer tank feed.

Cant resist ....:)

The flow is the reason for the chilling, and restrict that flow you degenerate that system from powerfull into mediocre or none if the ram seizes.

Just out of interest what is the bore of the ram?

61mm bore 80mm stroke. Full ali construction, with HDPE piston and 5mm Viton Oring.

Assuming 45 BarA, around 7°C and no pressure drops (guess-timate figures), Id guess youre looking at filling the ram (under no load) in around 0.04 seconds through a 13mm orifice - which is pretty quick :)

The only thing I can think of is what Woody says, if the pipework gets bigger downstream you might be over expanding your gas and giving it too much opportunity to form ice. If possible Id be inclined to try it with all the bores at 13mm. It might help keep the pressure and temperature up a bit.

You can download an Excell spreadsheet that will give MY guesstimate of required MAX flow for a given mass , pressure ,leverage ratio and ram size.

Here

http://www.teamonslaught.fsnet.co.uk/Max.xlshttp://www.teamonslaught.fsnet.co.uk/Max.xls

or theres an embedded one in my first pneumatic page...scroll to the bottom.

http://www.teamonslaught.fsnet.co.uk/pneumatics.htmhttp://www.teamonslaught.fsnet.co.uk/pneumatics.htm

(Message edited by woody on January 03, 2008)

Andrew, first of all, very clever thinking with the heating of the ram. Indeed it is not allowed so we cant use a system like that but I like it when people think out of the box.

The plumbing on H2/Wedgie has already wide bores all the way through, nothing smaller than 13mm. If you need to get more heat into that system you would have to think about adding more heatsinks. Having the buffertank not in a T configuration but a connection at each end like Woody suggested will also help, but that would require a very drastic rebuild of the system. But I am sure it would be more efficient.

Would you be allowed to route your pipework around motors? (like a cooling jacket)
What about routing your wiring against the pnuematic system and using slightly smaller wiring than you would normally?

What are the safety issues with bottle heaters?

Most robots are effectively heaters since the entire electrical and mechancal system warms up during use. In that situation it seams a little odd to have a rule not allowing any heaters without clarifying what constitutes a heater. If it is a safety hazard then shouldnt it be defined? If it isnt, whats the rule there for?

How much could it improve perfomance in reality?

You can over define what is and what isnt allowed. I think its another occasion where common sense comes in.

In the end the event organisers are the ones that say yes or no to a bot running in their arena. If they feel that someone is doing something unsafe then they are the ones that say no.