I have a 100 pound platform that shall rest at a height of 6 feet. The
user will pull it down to about 3 feet and climb aboard. When the user
gets off, the platform should slowly raise to its original height of 6
feet. I plan to accomplish this using a pneumatic cylinder or two,
where one side is the platform and the other is a counterweight of
about the same weight as the platform. Will pneumatics be good for
this or perhaps a pulley system would be better? It shouldn't be too
hard to pull the platform down for a 150 pound person, and the platform
should not shoot up, potentially doing damage to the project, or anyone
nearby.

Ideas?

Jake

Pneumatics would do fine, and I was thinking of a water brake or sorts
to keep the rate controlled.
Vacuum might be easier to work with. This way the only time you need
the actual vacuum would be to lower the platform, then let a counterweight
raise it. It won't pass OSHA, but its simple. By controlling the rate that
the vacuum re enters the cylinder (controlled flow check restructure sort of
thing) you can let the cylinder do the braking. Not at all dissimilar is a
vacuum elevator. Google for "vacuum elevator"

"Jake" wrote in message
ups.com...
| I have a 100 pound platform that shall rest at a height of 6 feet. The
| user will pull it down to about 3 feet and climb aboard. When the user
| gets off, the platform should slowly raise to its original height of 6
| feet. I plan to accomplish this using a pneumatic cylinder or two,
| where one side is the platform and the other is a counterweight of
| about the same weight as the platform. Will pneumatics be good for
| this or perhaps a pulley system would be better? It shouldn't be too
| hard to pull the platform down for a 150 pound person, and the platform
| should not shoot up, potentially doing damage to the project, or anyone
| nearby.
|
| Ideas?
|
| Jake
|

I have a 100 pound platform that shall rest at a height of 6 feet. The
user will pull it down to about 3 feet and climb aboard. When the user
gets off, the platform should slowly raise to its original height of 6
feet. I plan to accomplish this using a pneumatic cylinder or two,
where one side is the platform and the other is a counterweight of
about the same weight as the platform. Will pneumatics be good for
this or perhaps a pulley system would be better? It shouldn't be too
hard to pull the platform down for a 150 pound person, and the platform
should not shoot up, potentially doing damage to the project, or anyone
nearby.

Ideas?

Jake

Maybe using cables and a governor on the windless to slow down the
upward movement?
Ken.

Very heavy duty gas shocks? Kinda like on a hatchback door, except much
heavier. This dampens out the load by a significant amount.

In article . com,
"Jake" wrote:

I have a 100 pound platform that shall rest at a height of 6 feet. The
user will pull it down to about 3 feet and climb aboard. When the user
gets off, the platform should slowly raise to its original height of 6
feet. I plan to accomplish this using a pneumatic cylinder or two,
where one side is the platform and the other is a counterweight of
about the same weight as the platform. Will pneumatics be good for
this or perhaps a pulley system would be better? It shouldn't be too
hard to pull the platform down for a 150 pound person, and the platform
should not shoot up, potentially doing damage to the project, or anyone
nearby.

Ideas?

Jake


I don't think pneumatics is a good choice because it will do nothing
until the pressure gets high enough then it will snap up. Hydraulics is
more controllable and can move at a set rate less dependant on the load.

--
Free men own guns, slaves don't
www.geocities.com/CapitolHill/5357/

"Nick Hull" wrote in message
...
In article . com,
"Jake" wrote:

I have a 100 pound platform that shall rest at a height of 6 feet. The
user will pull it down to about 3 feet and climb aboard. When the user
gets off, the platform should slowly raise to its original height of 6

I don't think pneumatics is a good choice because it will do nothing
until the pressure gets high enough then it will snap up. Hydraulics is
more controllable and can move at a set rate less dependant on the load.

Correct about favoring hydraulics over pneumatics -- but a properly-designed
and maintained hydraulic system moves at a rate completely INdependent of
the load, so long as the load is within the design limits of the system.
Leaks and poorly maintained pumps can mitigate that. But for most purposes,
you may think of an hydraulic system as a true positive-displacement
mechanism.

LLoyd

"Nick Hull" wrote in message
...
In article . com,
"Jake" wrote:

I have a 100 pound platform that shall rest at a height of 6 feet. The
user will pull it down to about 3 feet and climb aboard. When the user
gets off, the platform should slowly raise to its original height of 6
feet. I plan to accomplish this using a pneumatic cylinder or two,
where one side is the platform and the other is a counterweight of
about the same weight as the platform. Will pneumatics be good for
this or perhaps a pulley system would be better? It shouldn't be too
hard to pull the platform down for a 150 pound person, and the platform
should not shoot up, potentially doing damage to the project, or anyone
nearby.

Ideas?

Jake


I don't think pneumatics is a good choice because it will do nothing
until the pressure gets high enough then it will snap up. Hydraulics is
more controllable and can move at a set rate less dependant on the load.



If you use a double acting pneumatic cylinder and a counterweight system,
you only need air on one side of the cylinder. Fill the other side with oil
and connect it to a reservoir of oil through a needle valve. This will allow
very good control of the speed of the outstroke of the system. It will
however do nothing for the return stroke. I suggest that you could put a one
way valve in parallel with the needle valve so the return stroke is not
restricted as all it will do is cavitate the oil in the system.

Tom