DIY...tired of living the low life? Lift!

synolimit

So I don't know how many of you are tired of being lowered but I am, and hell I'm not even that low. I used to be like 1/4-1/2" lower but when I went 10.5" +15 and -5 with 285 square tires I started rubbing on the fenders.

So my current routine for lifting my car is drive up onto boards first. Now I don't have a lower profile jack so doing this at 2am sucks because I have to start the car and wake the neighbors. Also if I bought a low profile jack that's just gonna cost money or a car lift which takes up room I don't have plus $1000-$4000. Now even if I had a low profile jack I'd still have to jack one damn side at a time and then find a place for the stand to go. It's all just a PITA and I'm tired of it.

So what do I wanna DIY? Air jacks! So I started looking around and kits start at around $2500! Screw that. So I started looking for just the cylinders themselves, around $300-$400 each. Not bad but I can still do better. So I started googling pneumatic air cylinders and found one by Bimba that should work! It's 2.5" ID with a 12" shaft travel that'll raise the car. It's a 5x line pressure so with my air tank at 165psi each one can lift 825lbs or 3300lbs total for 4. Now that should work since the cars around 3000lbs and getting lighter. If it doesn't that's ok. Each cylinder can handle 250psi max or 1250lbs which I could do if I got a compressed air tank which holds 2000-3000psi with a regulator. The bonus....each ones only $100! So total investments around $400-450 after a few fittings, hoses, valve etc. Also each cylinder weighs only around 4lbs. So the car will only be gaining around 25lbs and that's not bad.

So question is mounting. Most pics I see they mount them onto the roll cage main hoop and front A pilar hoop. But mines not installed yet. So I was thinking the rear could be mounted to the frame where the tow hook lives and the front maybe the crash beam, all with brackets of course that the cylinders go into.

Stay tuned for more....

Pics....





Rear mounting spot to the corner of two frame spots

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13 370z-

black_sedan

Havent been on the forums lately.... But this is interesting.....

synolimit

Ok first update, kinda small.

Went to Home Depot to pick up a valve and fittings. The valve is needed on the air line because the air cylinders will fully pressurize if you just connect it from the tank and/or regulator instantly haha. I don't think it'd be a good thing for all 4 cylinders to receive 165psi and have the car jump off the ground when they push out and down. This ant a jumpin low rider.

Next I drilled a hole in the bumper and back of the trunk. Here some brass fittings will bolt/pinch them into place with the air connector sitting out the back for easy access.

Next update I'll probably run the lines and fittings and start making the mounts to hold the cylinders and bolt or weld to the frame.

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13 370z-

Havoc

subbed

Masterbeatty

have you come up with a bracket for the jacks?

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Masterbeatty journal

synolimit

Not yet. Still waiting to get them. Pics show a large threaded end so that's probably going to go through a box or cylinder I'll build and screwed down to it. Then it'll be welded or bolted into that rear corner of the frame. The front I'm still working on. I'm also not sure what holes are what yet. I believe these being "double" I need to air up and air down which is not what I want. Might have to find single stage cylinders that retract with a spring. I just need more time out side of work.

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13 370z-

daj349

you might need to do some reading on pneumatics. I like the project idea but it could be very dangerous if not done correctly. Here are a few things you should consider:

-A safety factor for the amount total force the cylinders will produce. If you're lifting a 3000lb car with 3300lbf then it won't be vary stable when it's off the ground and take a bit of time to lift up. Air is compressible, unlike hydraulic fluid, and the cylinders are gonna have some give without a large difference between their force and the car's weight. I'd say you should go with at least 4000lbf total, especially if someone is gonna be under this thing. You also need to consider the weight distribution of the car. Not every cylinder will be loaded equally by the car.

A 2.5" bore air cylinder is the internal bore which experiences the driving pressure. The shaft diameter will be much less. You need to make sure that the shaft diameter and material is strong enough to not fail in bending, compression, or shear. This can be calculated using the shear and tensile strengths of the shaft material along with the dimensions. Sounds harder than it is but you should also consider a large safety factor here. Similar material strength calculations should be done for however you mount the cylinders to the car.

Yes, you will need a single acting cylinder with a return spring.

Bimba is a big name in air cylinders, I've never had an issue with their stuff

The force the cylinder produces is the air pressure multiplied by the area of the bore. (pi/4)*(bore)^2*(pressure) 2.5" bore is closer to producing 4.9 times the line pressure, I wouldn't round up on this..

I would run a regulator in front of your cylinders too so they receive consistent pressure. Your compressor isn't gonna give a constant pressure at it's maximum rated pressure especially when you try to fill the cylinders. Shoot for 60 or 70% of what your compressor puts out. Also, this will let the system work consistently with any compressor that runs above what you set your regulator at.

You need to control the cylinder speed with flow control values or you're gonna crack the concrete when you put full pressure to a depressed cylinder that has no opposing force. It would be like a jack hammer. haha

Flow rate metering values or equal line lengths between cylinders would also be a good idea. This would help with actuate at similar rates which would make the car more stable as it rises and put less bending force on the cylinder shafts. Bending forces on a linear actuator are bad news.

The cylinders also need to be equidistant from the ground. The shaft needs to be perpendicular to the ground when raised or the shaft will experience bending forces.

That's all I can think of off the top of my heads. Good luck with the project, I wanna see what you come up with!

EDIT
Also, you can use the butterfly valve you bought to trap pressure in the cylinders after they are aired up. That way the car won't fall if there is a failure in the compressor or the feed line. (someone tripping over it and pulling it out, etc.)

SouthArk370Z

Great job of covering the basics of pneumatics in a few short paragraphs.

Side loads on the cylinder shafts will bend shafts and cause premature seal wear. Make sure the car lifts straight up.

Some feet on the ends of the shafts will help when on soft surfaces (dirt, asphalt, &c) plus add a little bit of stability.

Keep in mind that retracting force is less than extending force. Shouldn't be a big deal for this project.

It is important enough to deserve repeating: air is compressible and there can be a tremendous amount of potential energy in the system just waiting to go kinetic.

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zmanelite

^^^ If not done correctly, I can totally see this going up in the air like a logo stick or one of the shafts ripping apart its mounting point

The feet ideas I'd great ,also will need something to level the car on uneven surface

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synolimit

1. 2x2 or 3x3 feet will be added to the threaded ends and of course it'll be measured as straight as possible. I'll probable weld a bolt to a plate and screw it onto the shafts end and lock it down with a pin going through or something.

2. Most rods are made of chrome plated carbon steel or something stronger as they are lifting stuff in the 1250lbs range each.

3. You missed what I wrote. I said my tank only goes to 165psi which will equal 3300 lbs. Each cylinder can do 250psi max which is 5000 lbs of force. If my compressor can't do it then I'll buy a tank of nitrogen which holds the gas in the 2000-3000psi range. Then I can turn it down to 200-250psi in the lines.

4. Once up in the air of course I won't be getting under it. That's why air jacks systems come with mounts that rap around the cylinder shafts. I'll just be using my jack stands in the intended spots Nissan made for the car.

5. As much reading as I've done these cylinders have been used before so I'm sure they work but I'm still looking for single stage. If I can't find it which I'm not seeing as single stage for some reason only has very very small travel lengths I'll just use these and run them as double stage no problem. Or I'll cap the air line return port and push them up all the way with my hand with the air valve in the open position. I'm sure they can't be harder to push up like pushing on a cars shock shaft.

6. Lines will be cut and coiled so all 4 are 100% equal in length so lift will be equal as they should.

7. As for uneven surfaces there's nothing really to do. I can measure up from my garage floor and mount them accordingly but someone else's garage floor isn't going to be the same so I just have to mount to what I think will work. Most pits or floors are equal I'd hope minus maybe a small drainage run in one direction. At least these will only be used for seconds in each direction as the jack stands will be used when up in the air.

Hope that clarifies a few things.

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13 370z-

JARblue

Sub'd for results. But I will leave this here: How do you raise your 240sx? Product and comparison guide on floor jack alternatives.

Is it bad that I kinda want to see that?

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JC-Nismo

^^^, Dam there's a lot of good lift options out there.

synolimit

Them DIY ones are crazy and the ones on their sides

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13 370z-

SouthArk370Z

If you don't want to go with spring retraction, you can use an aspirator/eductor to pull a slight vacuum on the piston. You should be able to build a simple manifold to supply either pressure or vacuum.

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SouthArk370Z

Radial load rating is usually much less. But, since you will be on a level service when you use the jacks, this shouldn't be a big concern. Just keep in mind that the higher the length-to-diameter ratio, the more likely you are to bend the shaft with a radial load.


The best thing to do is not use it on uneven surfaces.
The units you show above have pretty long shafts (compared to diameter). I'd try to find out more about how much radial load they can take before using on an uneven surface. There may be a good reason that store-bought systems are sooooo expensive.

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