Pneumatic rams

[widow_twanky]

Just picked up today the following:

Humphrey 25-SP-1 air cylinder

See page 150 in this link

http://www.controlandpower.com/catalog/PDFs/Humphrey/Humphrey%20Actuators%20-%20SS.pdfhttp://www.controlandpower.com/catal...tuators%20-%20 SS.pdf

and one of these

http://www.metalwork.it/eng/img/prodotti/cilindri/11GB04%20SSC.pdfhttp://www.metalwork.it/eng/img/prod...GB04%20SSC.pdf

This one is the double acting 63mm bore, 75mm stroke version

Before I stick theseon a bench and start building the pneumatic circuit I thought it would be worthwhile checking they are suitable for CO2.

The one which concerns me is the Humphrey one which is marketed as an air ram. Obviously there is a significant temperature difference between compressed air and CO2 so I thought Id check the significance of this.

Once Ive got some advice on this, Ill probably ask a few more questions on competition rules compliance, sizing etc.

Andy

[mightymouse]

Go with the second one - but you will probably have to dismantle it and drill out the inlet holes as they are very small and you will need the gas flow to make them work well.

The phrase air ram means that is limited to compressed air, meaning it will not be rated much above 10bar so you will have to build a low pressure system.

Using CO2 will cause the rams to cool significantly but you will have to live with it - you may find that on cooling the alumunium body will cool more than the steel drive rod and this can cause the ram to seize up.

Trev

Why am I not surpirsed by your response Trevor. I was thinking of going with the second one anyway.

I think Ill hold off on taking it apart for the moment and do a bit of testing. Mainly because restricting the flow will restrict the operating speed and power until Ive got the bones of the system sorted out.

I deal a lot with the design and testing of CO2 extinguishing systems at work, but dropping down from 3 pipe to this is a bit of a learning curve. Having almost have a client kill himself once I have developed a healthy respect for CO2.

Ill probably get one of our suppliers to take it away and deal with it when I know what I want. (Thats the advantage of not having designed anything to go on the end of it yet!!

I would be interested in just going through the CO2 system. I was thinking:

CO2 bottle, regulator, isolating valve (any requirement for gauges?), three port manual valve to purge the system from outside the bot, big bit of pipe to act as a buffer tank, five port valve and actuator.

That was about all I could think of.

Andy

Take care with opening the port on the 63mm bore.
Its likely to be a slot thats only just below the ram seal when the ram is closed .... just drilling out the port might not be an option unless you have sufficient clearance.

No need to worry for the moment Woody, as I say Ill just be bench testing the system for the moment so it may be that eventually I get another ram for the final version.

I just really want to get the whole system together before sticking it in a bot.

Got to sort out Cylon 2 along with this which is becoming abit more work than I thought, but should be ready for the 27th Jan in Swindon. (BTW even if you follow all the good design rules about good design of friction drives theyre rubbish)

Next comes a nice simple spike weapon on a ram bot. Dont really want to over complicate things just yet.

Andy

Big bit of pipe a small powder extinguisher bottle can make a good donor for a buffer tank.

No gauge requirements.

A single port valve is all you need to purge the system .......( its normal practice to close the bottle supply valve first )...but a 3 port that shuts off the supply as well as dumps the system is good.

because restricting the flow will restrict the operating speed and power
You may not notice any speed reduction due to poor flow if the ram is in an unloaded state.... to slow the ram down for testing restrict the extend exhaust on the 5 port valve.