Hefty actuators or fast travel hydraulics

You might look for a variable hand pump, if they are sold separately. I bought a Michelin floor jack last summer that will extend in one stroke when empty, about 10 strokes jacking up the front of my car, and about 30 strokes jacking the counter weight of my fork lift.
I have no clue how they do it, or if these pumps can be purchased separately, but it's one of the darnedest things I have seen in a while. Hand pressure on the jack handle seems to remain about the same.

How much force do you need at what speed? That's how about much energy you need to put in. How about using air bags from cars of some other pyrotechnically device? Fast enough?

Electrical or pneumatic RV slide-out section actuators? I saw some nice ones, can't find that page but this is about the same-
Dave

You might consider adapting the two speed hydraulic jack in the Harbor Freight manual log splitter item# 39981

of course, steve, but you underspecified your requirements - For example, the frequency response on the horizontal stabilizer on the L-1011 was 4 hz, and a step into it would move the stabilizer (about 60 feet wide by 20 feet deep) full travel fast enough that it would cause the nose wheel of a 350,000 pound airplane to lift off the ground several feet - is that fast enough? (don't ask me how I know this)
I think you really want to ask a question related to pump power - that is the limitation, not the cylinder

12V hydraulic power pack and a deep-cycle battery on the trailer tongue, and a ram on the tongue to tilt it. It'll go up fairly fast, especially if the pump is a 2-stage - it will run in High till the pressure starts going up, then shift to Low automagically.
-->--

I would add a mast with a boat winch to pull up the front edge. I think a pickup truck bed crane would be about right, you could attach the base plate to the tongue. If it had an outrigger support you could use it to load heavy cargo. I have an older model of the type of crane Harbor Freight sells but from Homier, a home made extension mast to raise the pump to clear a bulky washing machine etc and a boat winch added on top, essentially upgrading it to the current model: the load allows, it's easier to use without the extension mast.
jsw

Hmmm... maybe you need to go mechanical. How about an old scissor jack or one of the crank-type extension jacks that ford used for pickups? You could adjust the speed by how far from the fulcrum you mounted it, provided you could still jack it.
Actually, you could do the same thing with a hydraulic jack. If the load isn't too much to pump, just keep moving it closer to the fulcrum until you get the speed you want. It's not like there's any requirement that says you have to use the full jack travel...though you might need to make an extension for the release valve, and maybe a linkage to get the jack action out to where you can get at it without contortions.
--Glenn Lyford

It's to dump the rocks and dirt from the trailer when using it for a dumptruck. Your suggestions would be Mythbusters stuff, and expensive.
Steve

And, your point? I'll chip in if you do the video.

| I'm cutting the hitch to my ATV trailer to make a pivot point to make it | dump. I need something that will raise it up and fast. I have looked into | 12v. actuators, and found them expensive. A SMALL long ram hydraulic would | work, but I don't want to be pumping all day. Are there any hydraulics made | that have a faster than 1/8" per stroke rate? A site for reasonably priced | actuators would be appreciated, too, as I think this will probably be the | way it's gonna go. | | Steve |
You need to find out your maximum load and the desired speed you need that load to be raised! The available force needed to raise that load is determined by the resultant force of the hydraulic actuator acting upon the load and it is related to the hydraulic pressure and effective face area of the piston. (The maximum force a hydraulic actuator can provide is calculated from the formula Fmax = Pressure X effective area of piston) Remember, the angle of the force application relative to a base plane must also be factored in the calculation since it takes more force to raise a load if the raising actuator is not acting in line with the movement of the load. The speed of travel is determined by how much/how fast the hydraulic pump can supply pressurized hydraulic fluid at the target pressure necessary to raise the load. Between two pumps, the one with the highest volumetric output at a given pressure, (provided other things are the same) would provide the fastest actuation to a hydraulic actuator.

| | |
|| I'm cutting the hitch to my ATV trailer to make a pivot point to make it || dump. I need something that will raise it up and fast. I have looked | into || 12v. actuators, and found them expensive. A SMALL long ram hydraulic | would || work, but I don't want to be pumping all day. Are there any hydraulics | made || that have a faster than 1/8" per stroke rate? A site for reasonably | priced || actuators would be appreciated, too, as I think this will probably be the || way it's gonna go. || || Steve || | | You need to find out your maximum load and the desired speed you need that | load to be raised! | The available force needed to raise that load is determined by the resultant | force of the hydraulic actuator acting upon the load and it is related to | the hydraulic pressure and effective face area of the piston. (The maximum | force a hydraulic actuator can provide is calculated from the formula Fmax = | Pressure X effective area of piston) Remember, the angle of the force | application relative to a base plane must also be factored in the | calculation since it takes more force to raise a load if the raising | actuator is not acting in line with the movement of the load. | The speed of travel is determined by how much/how fast the hydraulic pump | can supply pressurized hydraulic fluid at the target pressure necessary to | raise the load. Between two pumps, the one with the highest volumetric | output at a given pressure, (provided other things are the same) would | provide the fastest actuation to a hydraulic actuator. | Of course mechanical linkages, gears and levers could also be employed to alter the movement and characteristics of the hydraulic actuators. To analyze it at it's simplest and basic form you can't get more energy higher than what your hydraulic pump could deliver to your hydraulic actuator.

On Thu, 4 Jun 2009 08:12:50 -0600, the infamous "SteveB" scrawled the following:
Hey, just nestle your favorite trebuchet under the pivot point of the trailer and it'll work just fine for expediting offloads.

Rearrange the jack and bellcrank from a floor jack?
jsw