Subject:
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Re: pneumatic cylinder: why not hydraulic ??
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Newsgroups:
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lugnet.technic
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Date:
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Thu, 8 Apr 2004 15:13:52 GMT
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Viewed:
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2608 times
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In lugnet.technic, David Laswell wrote:
> In lugnet.technic, Harro de Jong wrote:
> > 7. if you used hydraulics, a cylinder would extend or retract fully with
> > one stroke of the pump.
>
> Not necessarily. Assuming both cylinders are the same size, a full pump
> cylinder stroke will only result in a full working cylinder stroke if the
> working cylinder doesn't have significantly more resistance than the pump
> cylinder. If the working cylinder is trying to lift a heavy load, two or more
> pumps might be required to generate enough psi to lift the load.
It is my understanding that fliuds cannot be compressed. So a cylinder hooked to
another cylinder with fluid in between (assuming no leaks), would always provide
1 to 1 movement.
I'm not an expert in hydraulics, but I think your claim above only applies to
pneumatics, because gasses can be compressed.
>
> > You also couldn't use compressors anymore.
>
> Again, not necessarily. Theoretically a fluid with very little viscosity might
> be pumpable by compressor, assuming you can get away with submerging the
> compressor. The problem you'd have is that you'd need to keep the motor well
> removed from the area, and running a drive shaft is the only way I can think of
> that would prevent the hydrolic fluid from getting sprayed all over.
>
> That still doesn't answer the question of why a hydrolic system would be
> preferable to a pneumatic system.
Hydraulics are preffereable in some cases, because the fluid cannot be
compressed. This allows more direct control over the articulated pistons. For
things like steering, hydaulics is preferred over pneumatics because you get 1:1
movement, no matter how much the wheels don't want to turn.
Kevin
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Message has 1 Reply:
 | | Re: pneumatic cylinder: why not hydraulic ??
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| (...) The amount that a fluid can be compressed varies with the fluid, the temperature, the pressure and other things. Water can be compressed too much - that's why trucks don't use it for their hydraulic systems. Hydraulic fluid is special oil that (...) (20 years ago, 8-Apr-04, to lugnet.technic)
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Message is in Reply To:
| | Re: pneumatic cylinder: why not hydraulic ??
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| (...) Not necessarily. Assuming both cylinders are the same size, a full pump cylinder stroke will only result in a full working cylinder stroke if the working cylinder doesn't have significantly more resistance than the pump cylinder. If the (...) (20 years ago, 7-Apr-04, to lugnet.technic)
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