Hydraulics Question

[Oski1868]

Looking for a little advice on an idea I had for my M1078 hydraulic system. Specifically I am wondering if the standard system could be altered to have the "suspension" units re-tasked to run a lift off the back of the truck.

As I am slowly working on transforming the truck into an RV I want to be able build a lift capable of supporting a dirt bike ... or two. I have a design that will fit in the frame rails ... I just need to drive the pistons. I haven't done much with hydraulics in the past ... but it seems pretty straight forward. my concern is that the units for the lift would be larger than the ones for the suspension. I don't know if that is an issue or not. That said ... it would be really slick to be able to operate the rear lift at the same control point as the cab and spare tire.

Any thoughts from the brain trust would be appreciated ...

PS: Here are a couple of shots of the old girl ....



Now that the bed is off ... I just have to weld some extensions on the frame ... build a subframe and a comfy RV box and it's off to Alaska! (If only it were that simple!)

 

[NDT]

If you keep the new cylinder's bores similar to the present ones, you should get about the same amount of force. Larger bores will give you greater force. Either way, you will need to enlarge your reservoir at the pump to store the additional fluid needed for longer or larger cylinders.

 

[Suprman]

Im not feeling that the air hyd pump is reliable for long term continuous duty. The transmission has a pto port on the drivers side and they all have the ring gear already. Or you could do an electric hyd setup at the back. You could put the controls wherever you wanted.

 

[tobyS]

Im not feeling that the air hyd pump is reliable for long term continuous duty. The transmission has a pto port on the drivers side and they all have the ring gear already. Or you could do an electric hyd setup at the back. You could put the controls wherever you wanted.

I think he is talking about running the hydraulics only when he wants to load or unload, Will. That would be a good application for the truck's system, I think.

If you men can tell me about the system, I'll go through the numbers. His biggest issue will be the reservoir, but that all depends on what size and stroke cylinder (s) he is adding.

First, is this a gear pump with an open center system or is it a closed center system? Pictures will help.

Second, what size cylinder, how long will it's stroke be and is there more than 1?

Would simply teeing it off and having shut off valves be a viable option, rather than changing the valve?

 

[Suprman]

It's a little piston pump that is powered by truck air. It is meant to operate the cab folding and spare tire neither of which happen fast. Could it run something else, possibly. Is it wise to tap off the system I don't think so. The reservoir is parts of the pump.

 

[patracy]

From what videos I've seen of the cab tilt and the spare lift operations, moving a entire bed would probably take a unreasonably long amount of time with the stock pump. My vote would be a electric hydraulic pump, or a PTO based pump.

 

[tobyS]

It's a little piston pump that is powered by truck air. It is meant to operate the cab folding and spare tire neither of which happen fast. Could it run something else, possibly. Is it wise to tap off the system I don't think so. The reservoir is parts of the pump.

It wouldn't be much different than a battery operated pump but the reservoir is probably not big enough. I can't see that it would take a lot more than the cab tilt cylinders (but I don't have one to know). Is the reservoir potentially enlarged for the additional cylinder volume? Is the air/hydraulic system reliable or marginal? Is there a PTO?

 

[tobyS]

From what videos I've seen of the cab tilt and the spare lift operations, moving a entire bed would probably take a unreasonably long amount of time with the stock pump. My vote would be a electric hydraulic pump, or a PTO based pump.

"a lift capable of supporting a dirt bike ... or two".... doesn't sound like it's a whole lot heavier than the cab is.

If he is talking about an entire bed lift, then sure, find a larger capacity one. If a bike and the lift are about the same as a cab weight, I could see it operating at about the same speed...very slow (from the descriptions). It could work if the tank capacity is big enough or can be made bigger. Is the trucks air supply enough?

 

[patracy]

"a lift capable of supporting a dirt bike ... or two".... doesn't sound like it's a whole lot heavier than the cab is.

If he is talking about an entire bed lift, then sure, find a larger capacity one. If a bike and the lift are about the same as a cab weight, I could see it operating at about the same speed...very slow (from the descriptions). It could work if the tank capacity is big enough or can be made bigger.

You're right, I rushed to an assumption there. He's removed the bed and is making a RV. I'm guessing he's talking about something like a liftgate or maybe a "crane" like the spare tire setup.

 

[Oxyacetylene]

Now that the bed is off ... I just have to weld some extensions on the frame ... build a subframe and a comfy RV box and it's off to Alaska! (If only it were that simple!)

That is a dream of mine, to build an extreme RV or something similar and spend some time in Alaska. I thought about some system for transporting a dirt bike or dual sport bike. It would be pretty cool at the rallys and other events to have the bike to ride around. Maybe rather than a lift system, just have a mount and a removable ramp?

 

[Oski1868]

You're right, I rushed to an assumption there. He's removed the bed and is making a RV. I'm guessing he's talking about something like a liftgate or maybe a "crane" like the spare tire setup.[/QUOTE


Sorry for the delay in getting back to you guys ... pesky job always gets in the way of important truck things!

My plan was to mount a couple of these in the 4 ft extension we are welding on the frame (2.5" bore - 24 " stroke)


these will drive to cables that will lift the collapsible platform on the back of the truck .... something like this



In thinking about it ... the cylinders and weight involved are similar to those that lift the cab. Given the slow speeds of that operation, I think I might go for the self contained system for this project.

 

[tobyS]

2.5" dia is 4.91 square inches x 24" stroke = 117.84 square inches. There are 231 square inches in a gallon so it is just over 1/2 gallon per cylinder at the extended position. If you have a 1000 psi pump, one cylinder will lift 4,910# per cylinder or nearly 5 tons for both combined. Seems a bit strong, but I don't know the mechanical advantage in the mechanism.

Don't forget your 24 volt, not 12 when going for an electric pump/valve, if you go that way.

 

[Ukraine Train]

Cool idea, but I agree that it would be really taxing on the air pump to supply that volume of fluid at high pressure. Other options could be ball screw linear actuators or winches, since you're planning on pulling cable anyway.

 

[Oski1868]

2.5" dia is 4.91 square inches x 24" stroke = 117.84 square inches. There are 231 square inches in a gallon so it is just over 1/2 gallon per cylinder at the extended position. If you have a 1000 psi pump, one cylinder will lift 4,910# per cylinder or nearly 5 tons for both combined. Seems a bit strong, but I don't know the mechanical advantage in the mechanism.

Don't forget your 24 volt, not 12 when going for an electric pump/valve, if you go that way.

Thank you for that information ... that is helpful. I should have mentioned that my plan was to have a 2:1 disadvantage ... something like this:

 

[Suprman]

The newer armored cab lmtv trucks use a electric/hydraulic pump with a larger reservoir.

 

[Ukraine Train]

Thank you for that information ... that is helpful. I should have mentioned that my plan was to have a 2:1 disadvantage ... something like this:

View attachment 605672

That's an electric over hydraulic setup in the picture. Motor on the right, pump/reservoir on the left.

 

[Suprman]

Looks like this

 

[tobyS]

Looks like this
View attachment 605680

Are you setting on any of those Will?

 

[tobyS]

That's an electric over hydraulic setup in the picture. Motor on the right, pump/reservoir on the left.

Check out the piston size on the one pictured. I doubt it's more than 1.5", if that.

If you have two of them, one at each end of the lift platform, you could use a gear type flow divider so that one side doesn't bind like it might if you only have a tee.

Do you have any of these parts yet?

 

[Oski1868]

After doing some research and re-thinking my box design, I am thinking I might try and fabricate something like this ....



definitely will take a couple of cylinders ... but eliminates the chain/cable drive component.