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I'm having a bit of brainfade and struggling to figure out how to plumb a hydraulic ram system up. I want to lift a hinged floor from underneath, with two rams, which will require them to be pumped up. I want to be able to release the pressure and the floor then lower down, swinging on the hinges. (Imagine a trapdoor if you can't visualise it. I want to hold the door closed with the rams, and when the hydraulic pressure is released the trapdoor swings down.) I don't mind using a manual pump or a electric one, and along the way I'll need a flow divider to keep the two rams evenly fed, but I can't figure out the return flow path. Like I said I'm having a bit of a brainfade and doubting myself, so if anyone knows their way around a simple hydraulic system I'd appreciate some help. And it's totally old car related too! This picture might help. You're looking upwards at it.  |
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Phil H
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Posts: 1,448
Club RR Member Number: 133
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Hydraulic Ram SystemPhil H
@philhoward
Club Retro Rides Member 133
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My concern is your “rest” position is rams extended; stored energy and all that jazz. Slightest bit of leakage and your “trapdoor” will self-open unless you’ve got some sort of chocking/anti-fall mechanism (like a hydraulic lift)?
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Phil H
Posted a lot
Posts: 1,448
Club RR Member Number: 133
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Hydraulic Ram SystemPhil H
@philhoward
Club Retro Rides Member 133
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As long as the two rams are the same, there shouldn’t be any need to use flow dividers as the fluid will take the path of least resistance anyway. Just tee the two together?
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That's a good point, they will have an equal loading almost all the time.
There will be clasps in place once "up" so the rams will be relieved of some of the load bearing when extended. I'm planning on using locally sourced heavy duty rams that far outclass the maximum potential load anyway, my area is full of companies making £500k+ quarry rock crushers so we have a plethora of heavy industry manufacturers making things like that.
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slater
Club Retro Rides Member
Posts: 6,390
Club RR Member Number: 78
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Hydraulic Ram Systemslater
@slater
Club Retro Rides Member 78
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If you just want it to return under it's own weight (or a spring or somthing) You just need a single acting cylinder (or two) and a 2/1 valve. The ram connects into the '1' side. The other side you have your pressure source and a drain. If you want it to open under power you need a double acting cylinder and a 3/2 valve.
As has been mentioned tho. Safety may be questionable!
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bmw2101
Part of things
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the ones you have drawn look to be double acting, single stage, linea actuators, or "a ram"!
push the fluid on one port, and you will get fluid out of the other port. So you need a power up and power down and have the non powering returning back to tank.
If you get a 5 port, 3 position valve that has the two ports to the ram closed in the center position, it is fairly safe to use, and if your fluid rate is low, you can use anti burst valves which will hydrologically lock it into position.
However you design the system, remember that there is a magnification of power happening too, so powering out the ram will have more force than powering back the ram, this is because the blind end of the ram powering out has no rod in it, so you push with more fluid. Powering back, will give less force, and come back faster. So also, if you accidentally block off the rod end, and power the blind end, your likely to blow a hose or damage something.
I work with tipper trucks, and was working on a dmax with a small power up power down body today, that used a spx power pack, and a wray ram.
hth
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Jun 12, 2020 21:10:07 GMT
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However you design the system, remember that there is a magnification of power happening too, so powering out the ram will have more force than powering back the ram, this is because the blind end of the ram powering out has no rod in it, so you push with more fluid. Powering back, will give less force, and come back faster. hth That's exactly what I want, I want the up-swing to have lifting power, but it won't need it swinging down. I actually don't think i need it to operate two-ways, as the weight of it should swing it down naturally, kind of like an engine crane really, so a release valve to let pressure off would in theory work fine although I'd want more control than that and to release both rams at once, so it's not like I can just bolt up a couple of crane rams. I should just go look at something like a tail-lift on a truck shouldn't I? |
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bmw2101
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Jun 12, 2020 22:00:18 GMT
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truck tail lift has 2 chains, one ram. the chain is fixed at one point that is adjustable, around the top of the ram on a sprocket, then off to both sides of the tail lift to the top on a sprocket and back down to the platform. for flow speed you can use a flow control valve click herethat one only works one way, its free flow one way and restriction the other. we use that type of thing on tippers. |
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