Question on gas spring cylinder

[boblon]

I'm planning an upcoming build and want/need to compensate for the load of a rotary table I want to move vertically.

Am thinking of using a gas spring. Are they as simple as they seem, just order the length and force I need?

Is there anything I need to be aware of so I don't order the wrong thing?

I estimate the weight to be a total of around 60-70lbs.

Thanks,
BobL.

[dfmiller]

Bob,
I have never designed anything with them but there seems to be lots of information out there.
Gas lifts, props, struts, shocks & gas dampers technical information
This looked good.
Sounds like they might be just the thing.
Dave

[79TigerPilot]

A couple of things, the force is not constant though better than a real spring. You need to look at the curves on your particular gas spring to know how it will work for you. In reading up, I found a note indicating that you want to oriented them with the main body up and the push rod down. I guess this is to keep the seals wet with the internal oil.

I have two 250 pounders on the knee of my Bridgeport CNC conversion, so far they are working fine.

Craig

[boblon]

Thanks for the replies. I just wanted to make sure there wasn't something terribly wrong with the idea, or some 'feature' to really watch out for.
BobL.

[AndrewBond]

I used one to compensate for the load of a heavy Z axis, was a simpler solution than a brake, and I felt it was less prone to electro mechanical failure... They are easy to adjust by reducing the pressure of the gas.. just remember you can't put the gas back in once you have let it out...

Bondy

[boblon]

Thanks. I think I 'might' have found one that will work. The problem is finding one that will carry the load I want WITH the range I would like (didn't happen) AND fit in the spot I want to put it.

Two out of three was easy.

BobL.

[Geof]

You can make your own using a small air cylinder and a little pressure tank. This way you can tune it to the exact load you want to support, and adjust this during use. You can also get practically the same force throughout the stroke if the volume of the tank is many times larger than the displacement volume of the cylinder. Which is practical because the tank can be located anywhere.

[boblon]

Ok, forgive me but I don't know much about this, but the ones I'm looking at are in the 30 dollar range (mounting hardware excluded). By 'small air cylinder' you must be talking about something different maybe?

Thanks,
BobL.

[Geof]

This type of thing:

Pneumatic cylinder - 5/16" - 3" - Bimba

This is the type of tank you can use:

Amazon.com: BE Pressure 5 Gal Portable Air Storage Tank 125psi NEW: Home Improvement

Amazon.com: BE Pressure 5 Gal Portable Air Storage Tank 125psi NEW: Home Improvement

Bimba cylinders are expensive and you can probably find something cheaper but this solution will be more costly than just a simple gas spring. But it can allow you to use a cylinder that fits easily in the space available and adjust the pressure to suit the load. You do need a compressor of course.

[boblon]

Ok, I see now, Thanks.

I think I will proceed as I was going and if the concept works out but I need a better solution I will look into this more.

Thanks again,
BobL.