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Ideal External Shock Absorber for Air Cylinders

Ideal External Shock Absorber for Air Cylinders

Ideal External Shock Absorber for Air Cylinders

(OP)
Hi everyone,

I'm still very green when it comes to engineering design and I tried to look on the net to find what an ideal shock absorber would look like for an air cylinder that is travelling extremely fast (1300 mm/s)for a stroke length of 10mm, but I'm afraid I can't find any. I'm forced to use an external stopper because the internal cushioning cannot be used due to the extremely fast speed of the piston inside the air cylinder.

Is rubber ideal? If so, what kind? Does the shape of the rubber make a difference? Will it absorb more energy if the shock absorber was square as opposed to circular?

Any help or assistance would be appreciated. I attached a picture :P if that makes things a bit clearer

RE: Ideal External Shock Absorber for Air Cylinders

"Is rubber ideal?"

Sometimes, often we use sorbothane or equivalent


"If so, what kind?"

Typically high Shure - lots of carbon, lots of damping

"Does the shape of the rubber make a difference?"

Absolutely

"Will it absorb more energy if the shock absorber was square as opposed to circular? "
Pointy would be more typical, say half a parabolic cone

I realise that the advice i gtave is a bit gnomic, but you haven't really defined what you are trying to do. 1300 mm/s is no big deal in the suspension world, so you aren't exactly frightening me.

Cheers

Greg Locock


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RE: Ideal External Shock Absorber for Air Cylinders

(OP)
Hi Greg

I'm trying to modify an existing conveyer system that uses the mechanism in the picture to knock out or push out faulty products. For that, I need something that reacts pretty quick.

Is there any reference you can point to on why a pointy or conical shape is better? Your suggestion on using Sorbothane was something I learned today, thanks for that. It seems to be the material I am looking for but it does seem a bit pricier.

Thanks again!

RE: Ideal External Shock Absorber for Air Cylinders

A pointy or conical shape isn't necessarily 'better' or 'worse'.

When you're using a solid material as a damping element, the shape of the material effects the rate of change of damping vs. displacement (and via displacement, time).

Rubber is not a compressible material- it works for things like springs and dampers because it is flexible and it can move out of the way to absorb energy (not because it absorbs energy through a density change).

This all means that geometry is very important. Use a big rubber cube, and as soon as the damper and part to be damped are in contact, you're engaging the entire cross section immediately (i.e. a giant spike in damping force).

Use a conical section of some kind, and the damping force builds from zero in a progressive way that's easier on all the parts involved.

So, again, a particular shape isn't better or worse than any other shape; Greg is suggesting a parabolic or conical shape because in a large majority of cases, the type of damping ratio curve generated by such a shape is close to what most applications require.

RE: Ideal External Shock Absorber for Air Cylinders

Why not ask the cylinder mfg to beef up the internal dampers?
Very rapid acting cylinders are not uncommon, I'll bet that they have an answer.
After all there are half a dozen firms making good air cylinders.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Ideal External Shock Absorber for Air Cylinders

In addition to any bumper style that you may select, I would study the installation of a spring within the air cylinder to complement the bumper stopping power. Also think about the condition of the wing tip as it may bend from the stopping power of the bumper.

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