Hydraulic Scissor Lift Help

[icecactus]

Hey Guys,

I have been doing a lot of learning/researching over the last couple weeks on Hydraulics and other methods of creating a scissor lift. I want to create a height adjustable assembly table like the one pictured below..

I was hoping to get some advice and avoid any serious and costly mistakes

For the size I want, I am thinking dual scissors is the way to go. That means I either need to tie the scissors together mechanically or use dual cylinders. From my understanding, synchronizing the cylinders is going to be the challenge. I have no background in hydraulics. This is my first time learning all this stuff.

Power Unit:

I also want it to powered lift. I looked into a foot pedal deal for a manual lift and they are impossible to find and really expensive when I do find them. So I am thinking electrical with a remote pendant. The table will have 110V anyway. The problem has been finding a compact 110V hydraulic power unit, thats small enough to fit inside the lift. I can find 12V ones all day long, but I really dont' want to mess with a battery that needs replacing every few years.

I think I finally found one though...the quickjack 110V power unit
It's made for the quickjack obviously, but is 110V, has a remote pendant, is tiny, and has a flow divider/combiner built in which from my understanding should automatically synchronize the dual cylinders.

What do you think?

Cylinders

Finding single acting cylinders also has not been as easy as I thought. However, its my understanding I can take a dual acting cylinder and put a breather vent plug in the down port of the dual acting cylinder. That effectively makes it single acting correct?

End of Stroke

When the cylinder reaches its end of stroke, the pressure relief port should open and just flow back into the tank correct? Does that harm the cylinder? I would think its better to let the cylinder reach end of stroke, then have the table hit a stop and possibly bend/deform the scissor arms...probably a stupid question but I have not been able to find a definite answer on google yet.


Appreciate any advice/ideas etc!

EDIT:

Looking for 2000 lbs capacity min.
8" height when closed, min 37" height when open
Approx table dimensions of 32" x 76" (not 100% sure on this yet)

 

[tool-guy]

Maybe consider looking for a motorcycle lift, either new or secondhand and add a table top to that.

 

[oldironfarmer]

You've got a big job ahead of you. You also might look for an old electric gurney.

Posting a lot more information about what you want, and why you are doing it will help with people suggesting ideas.

1 A flow divider is not accurate enough to keep two cylinders aligned unless you go all the way down regularly. Flow dividers leak, cylinders leak, small differences in scissor lifts put them in a bind real quick. A horizontal cylinder driving both scissors is one option.

2 You are correct on how to make a single acting cylinder. However you effectively get storage and prevent external leaks by connecting the dead end of the cylinder to the bottom of the hydraulic reservoir. Then as the cylinder extends it helps refill the reservoir.

3 It is OK to extend a cylinder under full pressure. No external stops required.

 

[no704]

How much travel (vertical) are you looking for? I have built a couple using electric actuators. How precise are you trying to be? What kind of weight?

You can get pheunamitic over hydrolic foot pumps ranging from HF (~$200) to real ones for a few $1000

 

[icecactus]

Thanks for the tips so far guys

How much travel (vertical) are you looking for? I have built a couple using electric actuators. How precise are you trying to be? What kind of weight?

You can get pheunamitic over hydrolic foot pumps ranging from HF (~$200) to real ones for a few $1000

Electric Actuators was another option I was looking at. Most seem to be 12V and I still have the problem of trying to keep them in sync.

I want the lift to be 8" high when closed, and about 37" min when opened. Doesn't need to be within thousands, but as close as possible.

I have looked at the air/hydrualic pumps. I have never used one before but it looks like they pulse which I didnt really care for and are noisy. Its also a hassle to run the air hose out every time I want to lift. I have not completely ruled it out but so far I am not keen on the idea.

 

[Keyblazer]

If 12v is cheaper then look at powering it with a hacked computer power supply. Looked like a cheap, and easy solution to powering my 12v project beadroller.

 

[gordo9742000]

For my scissor lift I used a 110v hydraulic power unit off of a two post lift. Originally started with and air over hydraulic. But like you said noisey and it pulsed going up.

 

[jimgood]

Wouldn't the cylinders be in sync as long as the fluid can cross freely between the two to equalize the pressure?

 

[icecactus]

Wouldn't the cylinders be in sync as long as the fluid can cross freely between the two to equalize the pressure?

Pretty sure the cylinder with the least resistance is going to fill first. So if you had your load on one side of the table, the other side will lift first. They would not lift equally.

That's why you use a flow divider, that insures that your getting near the same flow to each cylinder. They claim within +-10% though...which could be quite a bit.

I have seen a ton of pics of tandem lifts on the internet, but I cannot find a hydraulic schematic to save my life. I want to see if they use flow dividers or maybe mechincally tie the 2 scissors together. Heck, maybe the table top ties it together enough that a simple T can be used and they equalize like a bucket on a loader.

 

[ilovevocs]

If your not lifting a literal ton of weight a winch can be used to pull the scissors together. Add a single movable pulley to increase mechanical advantage by 2. Pulley will however decrease the rate of travel.

 

[jimgood]

So my Ranger Quick Lift either has this flow divider in the pump or it relies on the weight of a car to be evenly distributed side to side.

 

[icecactus]

So my Ranger Quick Lift either has this flow divider in the pump or it relies on the weight of a car to be evenly distributed side to side.

Your quicklift has a flow divider built into the power unit. If you look at the power unit that I linked to in my original post, its the Ranger QuickLift power unit

 

[jimgood]

Your quicklift has a flow divider built into the power unit. If you look at the power unit that I linked to in my original post, its the Ranger QuickLift power unit

 

[no704]

If you size the cylinders correctly you maybe able to use a double acting as the master with the rod end supplying a smaller single slave cylinder forcing them to stay in sync.

 

[tonyprovo723]

I see this being an easy application to use the hospital bed as well. Bet you could find one cheap on CL once a family no longer needs it. Insurance companies buy the first one and people don't care to have used medical items around. You aren't using the mattress so no concern there. Should be cheap at an estate sale as well.

Sent from my SM-G930P using Tapatalk

 

[mcmlvii]

I want to see if they use flow dividers or maybe mechincally tie the 2 scissors together.

My 25yo Hydra-Lift scissor is mechanically tied together (yellow bar in photo below), with a single hydraulic line supplying both cylinders. Crude but effective.

 

[sanddan]

I built a folding work table that uses a acme screw to power the mechanism. You could tie the two folding scissors' together in a similar manner. I found this design online.

 

[icecactus]

I built a folding work table that uses a acme screw to power the mechanism. You could tie the two folding scissors' together in a similar manner. I found this design online.

I was/still considering using ball screws similar to how you did...can you lift a lot of weight with that? I am concerned that it would be hard to lift 2000lbs with it.

 

[icecactus]

My 25yo Hydra-Lift scissor is mechanically tied together (yellow bar in photo below), with a single hydraulic line supplying both cylinders. Crude but effective.

The more I study the other tandem designs, I am pretty sure they are just mechanically connected and will auto equalize themselves. Does yours operate smooth and at the same time?

 

[mcmlvii]

The more I study the other tandem designs, I am pretty sure they are just mechanically connected and will auto equalize themselves. Does yours operate smooth and at the same time?

I've only had a car on the lift once (see video link below, about the 2 min mark is where the fun starts) so I don't have a lot of experience using the lift yet but it worked well when I tried it out. The steel connecting bar is about 1/2" x 3-1/2" and is bolted to each platform with three bolts.

Scissor Lift Video

 

[mcmlvii]

I built a folding work table that uses a acme screw to power the mechanism. You could tie the two folding scissors' together in a similar manner. I found this design online.

That's a very cool table, Sanddan.

 

[greasyfingers01]

I'm wanting to build one of these as soon as I get my woodshop together. I was planning on using the harbor freight scissor lift cart and their pneumatic/hydraulic foot switch. I'm thinking of mounting it to a large metal base for a larger footprint (same size as the top) to make it stable, and offsetting the top so it's centered when at full lift. I don't think you'll need 2 synchronized lifts.


This was the inspiration for my table to be



Sent from my SM-N910V using Tapatalk

 

[icecactus]

I'm wanting to build one of these as soon as I get my woodshop together. I was planning on using the harbor freight scissor lift cart and their pneumatic/hydraulic foot switch. I'm thinking of mounting it to a large metal base for a larger footprint (same size as the top) to make it stable, and offsetting the top so it's centered when at full lift. I don't think you'll need 2 synchronized lifts.


This was the inspiration for my table to be



Sent from my SM-N910V using Tapatalk

Thats def a cool design, but I just think that's to much weight cantilevered. I have been considering trying to figure out to use 2 HF lifts though