Air piston lift system

Aie suspension not for offroad or overlanding as you cantsimply fix it on side of road and not in middle of nowhere australia or us areas. Its cool thou as when its new and works properly.
Russians had some extreme going touraeg with air. It was cool car until it worked.
 
^ I agree. We had a Disco 2 rear air suspension fail in the middle of the Simpson Desert. We unloaded it into other vehicles but couldn't fix it so the car was trashed by the time we finished crossing and reached Birdsville; even the tops of the A pillars were cracked!
 
The air piston system is not an airbag suspension like the Land Rover or Touareg, its only a 2" lift from the height given by the helical springs. If it fails, you just come back to that height without any issues.

@Red, indeed, you have no gap between the spring seat and the canister.....and how far is the tyre from the housing at the rear ? I have approximately 25mm, even 100mm OD cups should fit but I would go for 90mm OD. Now I need to know how much bar/psi is needed to make it lift.
 
[MENTION=3295]jf1sf5[/MENTION] I'm confused.. where are you looking at putting the lifting canister? I thought above the strut? but what your writing seems to imply the middle of the strut?

edit: or is it like the link given at the start, but the sleeve covers most of the coil when lowered?? I did say I was confused..!
 
I have about 10mm between rear tyre and housing.

Your psi per inch of lift is spring rate in pounds/inch divided by the piston shafts cross sectional area in square inch. Comes down to how large a piston diameter you use. Then times that by your inches of lift you want and that's your psi.
 
Probably the best design, which Dedman suggested to me, would be to have a a gas piston next to the shock. This way the piston is not change preload, therefore not risking spring block. And it is not extending the max length of the shock, so won't max out other components. This design would effectively stiffen the spring rates, raising the car, but won't change the shock and spring travel parameters. Hard part would be mounting it. As with all the mentioned designs, if it fails your shocks and spring will still operate as normal.
 
@Ben Up North, yes, you can be confused because I now want to install the air piston lift just under the springs as I have enough space to do it this way.

@Red, thank you for the maths ! And I don't understand the way Dedman wants to change the height and how ?!
 
Correct me if I'm wrong doing the maths in lbs/inch and psi...

125 lbs/inch : 4,2 sq/inch (8,54 sq/inch OD - 4,34 sq/inch ID) = 30 psi/inch

This means I would need 60 psi for a 2" lift....could be done with a CO2 power tank !

Now for the stroke, when on diagonal spin, there is twice the weight on 2 wheels meaning the compressed air cups would still allow full compression/wheel travel, wouldn't they ?
 
jf1sf5 said:
I now want to install the air piston lift just under the springs as I have enough space to do it this way.
Click to expand...

But won't that affect suspension travel? I thought that the best way would be to move the entire strut, keeping suspension travel the same, rather than increasing height by by compressing the spring ?
Or is that not what will happen?
I really am confused.
 
Well as far as i saw any air suspension or air bags inside springs or similar the more you lift car with it up the less travel you get. Touraegs on airbags had that extra height option where it would lift it maximum height for slow offroad driving but it would feel like driving on boltet suspension it wouldnt travel at all
Or lest say air bag inside spring if its takes half spring space and its inflated thats it you just got half spring travel left.
 
Sorry above calculations were for a separate piston taking partial load of the spring (A bit like an airbag system, but but a piston will give better travel then a bag). Not for raising the spring as per your design. I was thinking about the other design when I typed that. The other design is to have a gas piston running parallel to the shock, so that it only takes some of the load from the spring.


For your design, that raises the spring at the spring seat you are actually supporting the full weight of the car at the piston and the load the spring takes on level ground is exactly the same due to being stacked. So you would have to work out how many pounds each corner of the car weighs. Then it's just that weight in pounds divided by the cross sectional area of the piston shaft. You will need slightly more pressure then this figure to actually get the car to rise.



With your design, as you go on diagonal wheels, the weight on the diagonal corners of the car doubles, so the pistons will roughly half their lift. So if you are with in 1" of spring block currently, then you will get spring block. Alternatively, if you had the lower setting 1" lower then you have now, then the higher setting won't get spring block.

Ben - There's a few designs going on, and I'm not yet sure which is best. All the designs will cost some suspension travel when raised, just trying to work out which will remove the least. The Hotbits coilovers already use full suspension travel, if a lift mechanism spaces the entire shock down further, you will exceed the max travel of other suspension components. So the goal is to leave the shock as is, so that the shock is the limiting factor.
 
Red XS said:
\The Hotbits coilovers already use full suspension travel, if a lift mechanism spaces the entire shock down further, you will exceed the max travel of other suspension components. So the goal is to leave the shock as is, so that the shock is the limiting factor.
Click to expand...

Ahh, Gotcha. Wasn't considering that the current suspension would already max out travel, which makes sense. I was looking at the perspective of it replacing strut blocks.
This is pretty much what hotbits do already from what I understand, only with increased travel as well? i.e you wouldn't put strut blocks and long travel hotbits on a vehicle would you?
 
Yeah that's right. If you used standard struts then replace the strut top lift with the air lift then that would work. You wouldn't use a strut top lift with long travel coilovers.
 
The spring seat air piston lift design (the one I want to fabricate) needs about 200 psi (800 : 4,2) but @Red, is this math per inch of lift or for full lift (2") ?

The design Dedman wants to make is gas struts bolted from the housing to the upper spring perch, right ? This needs pretty long stroke gas struts and with the Eibach barrel springs it might be difficult to fit them ?
 
Red XS said:
The other design is to have a gas piston running parallel to the shock, so that it only takes some of the load from the spring.
Click to expand...

I hadn't realised this was what Dedman meant. Does this mean it effectively stiffens the spring rate of the suspension? I would prefer the spring/strut to operate exactly as before but with the body lifted higher (some loss of suspension travel aside)

All the designs will cost some suspension travel when raised, just trying to work out which will remove the least. The Hotbits coilovers already use full suspension travel, if a lift mechanism spaces the entire shock down further, you will exceed the max travel of other suspension components. So the goal is to leave the shock as is, so that the shock is the limiting factor.
Click to expand...

This is the important bit. My thoughts:

*You can limit downtravel with a limiting strap, easily done & easily adjusted, also readily available. Often used on built 4wds

*My idea would be to have 3.5" lift front, 4.5" lift rear with 2" subframe drops & the air lift system at 0" lift. This gives effective CV angles of 1.5" fr 2.5" rr higher than stock, with they can easily handle. I would run this as the default setting for general driving & easy 4wds tracks

*With the air lift at 1" lift for harder tracks, effective CV angles are 2.5" fr 3.5" rr, which is totally fine if they're OEM & in good condition

*For extreme sections of track where maximum lift is needed to clear obstacles, have the lift at 2". Effective CV angles are 2.5" fr 3.5" rr, which should be fine for short periods at low speed. It's when the CVs are at high angles at high speed that they flog out quickly, so this should be ok

*IMO some loss of suspension travel is acceptable with the lift at full height.

My idea is to improve reliability for general driving while keeping maximum performance when it's needed. What's everyone else's thought?
 
That's what I thought he meant.


Using a strap as you suggested would allow the lift to space down the entire strut, not effecting spring preload. This means no risk of spring block which is good. If you could make it a part of the strut top then it would suit all sorts of suspension including oem, not just Hotbits, so you get a larger market.


If you have 3.5" lift standard, you won't need to raise the car very often so the loss in articulation wouldn't be bad.


Depending on design and being gas, raising the car to half lift probably won't be that exact. As you go over bumps and the load varies the gas will compress and lift will vary. It would give a softer, but undampened ride, unless you have a way of locking it at 1" of lift?


Having less CV angle on the highway is a good idea.
 
There would have to be some way to control how much each piston is lifted, maybe a limiting valve. That's where [MENTION=4168]Dedman[/MENTION]'s engineering ability comes in haha
 
Another option would be hydraulic pistons like those https://www.kwsuspensions.net/products/hydraulic_lift_system with hydraulic lines going to a large diameter canister (could be attached in the trunk) in which a floating piston divides the air and oil and just a small compressor or CO2 power tank to supply air to the canister that compresses the oil towards the hydraulic pistons.

Advantage with air is that it is compressible to gain some wheel travel when diagonal spin occurs. Front and rear should be independant with electrically-controlled valves, one on each line, so that when the rear is heavily loaded (for example), the air piston lift system could be used for the rear only.
 
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@Red, how long are your front canisters ? I just measured mine and the tube only, without the cap, is 155mm long. I could install/swap the rear (135mm) I had originally to gain a little height for more adjusting possibilities as they would still have enough volume for the shaft to compress completely.
 
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