End of the world

[michaelgroves]

I have each bag individually controlled with it's own pneumatic switch. Works well...but its IS so not alot of wheel travel anyway!

When you say individually controlled - you mean you manually raise and lower the pressures in each bag individually depending on the obstacle you are negotiating? Or do you mean you decide which bag is connected to which other(s)?

For inflating/deflating mine, I didn't bother with having in-cab controls - I just had a schrader valve for each pair of bags (left pair or right pair), and so I could set the pressure in each pair from time to time using the onboard air.

 

[Antichrist]

IFS has certain advantages (ride quality among them), and there have been quantum leaps forward in IFS design since the early days.

Don't get me wrong, I'm not saying in and of itself IFS/IRS are a bad thing, it all depends on the application.
I don't think people who buy defenders have ride quality as major decision point. They want a good solid work platform. I just don't see the exponentially increased complexity justifying the added benefits in such an application.

 

[michaelgroves]

there are fully linked systems that the gravel trucks running in and out of the quarries use. All they use is a spring loaded check ball that is very crude. if air tries to move to fast between any of the airbags the check ball closes and blocks the passage. but if the pressure change/air movement is slow then the air passes without issue.

in effect at the very slow speeds that the suspension is cycled on the iregular surfaces of the quarry the pressure equalization helps the system articulate and keep the tires on the ground.

At speed on the road the system closes off because the suspension events are fast and the suspension acts normal. Pretty cool in action actually and just funny book simple in design.

That's an interesting tidbit. My perception was the other way around. Body roll seems a slow suspension event - going around a traffic circle for example, allows a long time for air to shift from the outer to the inner bag. Going over a bump, or diagonally through a dip in the ground, on the other hand, would take just a second or two, and therefore wouldn't allow enough time for air to pass from one side to the the other, and back again.

I was never convinced that my interconnecting the pairs of bags actually had the bogie effect I was hoping for, at least partly because the pipes connecting the bags were small bore, and it would take several seconds before a significant amount of air could be transferred.

 

[R_Lefebvre]

Body roll is a slow speed event, in suspension tuning parlance. Bumps when driving down the road are high speed. I think the case of articulation when we're talking about moving over very uneven terrain is VERY slow. I would think in Musky's example, the check ball would close the circuit somewhere between VERY slow and slow. So the axles could articulate when they are slowly moving over the ground of the quary.

In your case, I think the same is true. While slowly moving over uneven terrain, the air will move around to try and equalize pressure between the front and rear axle. Over bumps, there's not enough time for much air to travel through the line, so it acts as a regular independent airbag system.

I wouldn't want to link a system side to side without a valve of some sort, because a long duration corner, like a roundabout, would allow the air to transfer over, and you'd have excessive lean.

 

[muskyman]

gone

 

[Ron B]

When you say individually controlled - you mean you manually raise and lower the pressures in each bag individually depending on the obstacle you are negotiating? Or do you mean you decide which bag is connected to which other(s)?

For inflating/deflating mine, I didn't bother with having in-cab controls - I just had a schrader valve for each pair of bags (left pair or right pair), and so I could set the pressure in each pair from time to time using the onboard air.

I have each bag controlled by it's own pneumatic paddle switch and monitored by a gauge that shows all four corners as well as the tank pressure. Sure is alot smoother on dirts roads and the hwy. I tried to keep it as simple as a system like this would allow me.

rb

 

[muskyman]

gone

 

[Ron B]

I like it, but with any project like this it's a work in progress. I cannot admit to the fact that it is any good in off-camber situations (let alone anything) or Gurkha will accuse me of lying!

I have a build thread somewhere. If you are interested I'll pm the link to you. Didn't want to thread jack, but the talk of IS and airbags always gets me interested. There are many here who have forgotten more than I know about that subject!

rb

 

[muskyman]

gone

 

[Antichrist]

Or you could post the link here. I hardly think it would be a thread hijack.
I would admit to knowing very little about IS, but I think that's probably painfully obvious.

 

[Ron B]

here are two links with a bunch of pics:
http://www.hummerxclub.com/forum/viewtopic.php?f=23&t=3843
http://www.hummerxclub.com/forum/viewtopic.php?f=51&t=7560&st=0&sk=t&sd=a

I've been out of town working since last July so not too much has happened this year.

rb

 

[R_Lefebvre]

Pretty cool truck. Are you using automotive or industrial valves, etc? Just wondering how the durability of the system will work out, considering this is a thread about bashing overcomplexity. (Don't get me wrong, I like your setup.) I just hope you didn't use stuff from the street rod bagging crowd.

I'd love to set you up with an HMI touchscreen system with industrial valves and pressure sensors. For maybe $2000 you could have a colour display for bag and tank pressure, with a PLC program giving you push button control for selecting ride height, off-camber settings, etc. Would be a little more fun for me to do than industrial machine controls.

 

[Ron B]

I wanted to keep it simple and easy to fix. The touch screen sounds way cool, though it's the kind of electronic complexity (electrickery?) that I'm trying to stay away from. I didn't even want a digital gauge but had to use it because of space and durability. At first there were no electronics involved at all, just pneumatic switches, analogue guages, air-lines and bags. Very simple, worked well but the gauges kept getting thrashed when the pressure went too high -- such as the downhill side in an off-camber situation (hard to find smallish gauges that go over 200 psi, let alone dual needle to save space!). On steep hills or technical spots the pressure could spike near 300 psi!

The problem with auto ride height selection is adding sensors at the wheels (and more electronics) and I can't see going by the psi for ride height as it's a variable that constantly changes. You also have to be moving to level it out with IS.

Yes, I'm using the standard push/pull connectors and .25 inch lines -- they have held up really well. I wanted to change it all out for braided line but never got around to it (also a space issue). It's been 2 years and about 5k miles at 120 to 200 psi.

I've only had one failure so far. When I got the body lift the lines were all replaced with new ones and one was routed too close to my exhaust (meaning right on top of it). Made it a few weeks if local driving and about 100 miles of hwy before it blew (lost all pressure in the rear bags). Took about an hour or two to locate the leak, cut out the bad section and "splice" in a new section using a new length of line and 2 push connectors.

a work in progress, but still a lot of fun. I can do sections of bumpy trail at more than twice the speed as the other trucks with me...especially the other hummers! Stock I may have cracked a tooth!

rb

 

[michaelgroves]

I don't think complexity is too much of a problem if the failure mode is merely an inconvenience. I'm a bit of a gadget man by nature, but I always try to design systems in such a way that essential functionality won't be affected if the bells and whistles stop working. So things like digital gauges don't bother me - firstly, these days they are probably more reliable than analogue ones, and secondly, you could quite happily wing it without knowing the exact presssure in each of the air bags!

I guess the "limp home" mode of the LR3 is supposed to be a similar philosophy, although IMO, too many of the systems (and especially the anti-theft systems) don't leave one with sufficient capability in the event of a failure.

 

[Antichrist]

Exactly what my point has always been.