Telescopic cylinders – where to buy?

This topic has 8 replies, 4 voices, and was last updated 16 years, 5 months ago by sheep_fragger.

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January 24, 2008 at 2:36 pm #1258

tmacd
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So we’re building an ROV at school for the upcoming MATE contest, and I’m in charge of the arm that we’re going to need. I designed something that is simple and I think will work, but I’m wondering, are single,double or even triple stage extending cylinders (usable with hydraulics/pneumatics) hard to come by? Looking for about 3 in diamter, with a length extendable to about 18 inches maybe? Any online retailers or any suggestions? Thanks!

January 24, 2008 at 3:46 pm #15579

sheep_fragger
Participant

Google it, loads of company’s out there or you could make something if you have access to a machine shop, there is a compnay called seal jet that can make seals to whatever size you need depending where you live.

Or scavange the scrap yard.

Can I ask how big your rov is going to be, a three inch ram if it was for hydraulic use would be very heavy.

Are you going to use Hydraulic power or a compressed gas?

January 24, 2008 at 5:18 pm #15580

tmacd
Participant

its not cube shape persay, but it takes up maybe 2.5 by 3.5 feet and a foot and a half high? Now I’m not sure what you mean by "ram", the TC is going to have a two finger gripper at the end, which will be controller pneumatically, while the TC was going to be controller through hydraulics. Yeah I’ve been looking online, and it looks like mostly industrial things, which are too big, both size and price wise. I found one company, AHP which i am waiting on a quote from for 3 different sizes. They’ve been pretty good so far.

January 24, 2008 at 6:40 pm #15581

Ray Shields
Participant

I was going to Suggest Air & Power Hydraulics, but I see you have already found them. They supply a lot of hydraulic actuators to offshore companies.

January 25, 2008 at 4:40 am #15582

Horris
Participant

APH is the way to go. Usually good on price and speed of delivery.
I presume it is space constraints forcing you to consider 2 or 3 stage cylinders but be careful as this could cause you problems later on with position movement etc as they dont always work the way they are meant to as well as seals leaking more often than on single stage cylinders !

January 25, 2008 at 4:50 pm #15583

sheep_fragger
Participant

Have you thought about using water instead of compressed gas, you could use a small water pump for a hydraulic system using water.

The possible advantage is that you reduce the weight of components needed to power you manip arm.

This would also be fairly low pressure so much safer for a school project, plus water is free.

January 25, 2008 at 6:04 pm #15584

tmacd
Participant

well the thing about air vs water, is that we’d need a pretty big bilge pump down on the ROV already, but they are going to give us an air pig to use, which we keep up on the surface, so that would take of that, dont need to worry about buying/placing pumps, good call on the leaks in multistage cylinders, thats a concern of mine too, and i wasnt’ sure how that would work, basically, it doesnt have to stay extended for long, just long enough that it can grip something, then we’ll suck it right back. We have a machinist on the team now too, so we’re thinking about just making out own cylinders, but really we’re not sure yet, depends on the price, and whats available, but thats why we’re thinking about using air (even though i originally DID think about using water); no bilge pump on the ROV, dont have to buy a bilge pump, air is more powerful, etc. Its quite exciting, I’m really pleased with the cylinder placement and design, and everyone says its pretty clever, and i think we’re going to give the other teams a real run for their money. Apparently a lot of recruiters are at this competition every year, so I’m hoping i can snag an ROV design job

January 25, 2008 at 6:20 pm #15585

tmacd
Participant

also, meant to ask before, AHP looks great for cylinders, etc, any suggestions for goto places for valves? Right now it looks like im going to need a 3 spool valve, and potentially 3, 3 way pneumatic control valves (one for each cylinder) though i bet there is a way to do it with only 1 of each. Am i going to be able to find spool valves small enough to fit on an ROV, say 6 in x 6 in x 6 in?

January 25, 2008 at 9:46 pm #15586

sheep_fragger
Participant

When i mentioned water hydraulics i was thinkning along the lines of the system fitted to Mantis and Duplus submeribles.

The system on them would be fairly easy for you to source parts for at a reasonable price.

It consisted of single acting cylinders that were controlled by solenoid valves to control the flow of water.

The power source is a gear pump driven by a dc motor. Quite small from what I remember.

When you need to extend a cylinder the pump pressure is directed via the sol valves to the cylinder, to retract the cylinder the pump direction was reversed and the water would be sucked out of the cylinder via the open valve assisted by hydrostatic pressure acting on the cylinder.

If you are set in the design using air i seen a lot of pnenmatic solenoid valves on ebay that are cheap.

Good luck with the project btw
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