Air over leaf - anyone using it?

Anak said:

Not that it is apples to apples, but my Camaro has mono-leaf springs in the rear. There is a way to do it.

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Exactly. No, it isn't quite analogous to a truck build, but building an antiwrap bar is really not difficult, either.

I've considered going with a linked front and rear - but the headache of chasing down death wobble problems is just not something I want to deal with. I came VERY close to going leaf springs on the front of my 90 XJ for this very reason. It wasn't until I tackled the DW on the front of my wife's ZJ (by replacing everything except the housing and gearset) that I realized what a pain links can be. Leafs are elegant in their simplicity - control arms and support all in one.

They have their own issues, of course - namely the fact that a firm ride and flexible suspension are more or less at odds. That's why I'm looking at the A-O-L solution.

Air bags have arrived, they are smaller in diameter than I expected- a good thing, I just suck at guesstimation. Smaller bags have higher spring rate for the same pressure, so I suspect this will work in my favor.

At 0 pressure, they are about 8" tall. That's strictly the rubber holding its shape. They look like they will package easily into my suspension, using the Ruffstuff Specialties HD spring plates as a base to build off of (seriously, those things are BEEF!- 3/8" thick, IIRC.)I will weld some 1/4" wall receiver hitch stock I have laying around to elevate the bag mounting surface high enough to allow me to get tools on the u-bolt hardware, and weld a 1/4" plate atop it, offset as needed to clear and align to the framerail. Similar arrangement from the framereail, with a reinforcing section of 3/16" welded to the existing frame to spread the load. While I'm at this I will work in trackbar mounts front and rear, to address lateral sway, and bumpstop mount/landing pads as well. I'll also use the Daystar bag cradles to allow suspension dropout when doing angles and dangles with the truck, so as not to rip the bags open.

Forgot to mention, at 0 pressure with a pipe plug loosely installed, they support about 260 pounds with little squashing. I think I'm on the right track here.

These bags will grow in diameter some under pressure, as do most. There are other bags out there- made in USA, called "Slam Specialties". SS6 are a direct replacement for these, but are also nearly 3 times the price. That said, they do not grow in diameter at all, apparently, and so they do more work with less pressure. If I have any issues, I may explore their use, it will be a simple affair to change these out.

Just thinking now, doing some "back of the napkin" engineering on the fly, I may leave the spring plates unmolested, as my bolts are extra long (I have long nuts, doubled up on them). Lock down the spring plates with nylocks of normal height, fabricate all my needs as above on 1/4 or 3/8" thick plate, with holes to enable them to bolt in atop the spring plates. Nylocks bolt that down, and likely some loctite as well.

This will all be on my S10, so it doesn't apply to the XJ world directly (honestly it will be adaptable with very little effort). The only reaason I am doing the S10 first is because it's my DD and is *super* soft and wallows all around like a pig. My 90 XJ is presently deadlined, and my son's 97 is in the hands of a new driver- the 4" lift I've installed is all he's getting for a while. I will install RC SRBs out back after the rear springs settle a bit more, and eventually will install airbags out back to enable him to have some towing capacity as he's getting interested in the fabrication arts as a possible career and will need a way to tow heavy stuff now and again.

That said, this is modified tech, and this info is applicable to XJs, so if all are fine with the pics not being of XJs for a while, I will continue to post my efforts.

As it looks now, I'm $80 for the bags, probably $50 for some steel (I could build with parts on hand but don't want it to look too terribly hack, so will buy some plate and the like), $60 for the cradles, $40 for air fittings. That will do one end of the truck, with enough steel to do the other. A friend is a heavy diesel mechanic so I can probably raid his spares stash for fittings and line. Worst case, I am looking at about $300 to do the whole truck with an external-fill air system. That will be phase 1, and I've long since intended to build some sliders and have them sealed for air tanks (giving me about 6 gallons of storage). Another $200 (haven't really shopped that yet, so maybe less) gets me an onboard electric pump. I can of course do all of that in bits and pieces on down the line.

burntkat said:

That said, this is modified tech, and this info is applicable to XJs, so if all are fine with the pics not being of XJs for a while, I will continue to post my efforts.

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That is great! I love individual creativity.

techno1154 said:

That is great! I love individual creativity.

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Thank you sir, but I am FAR from being creative here. In all I am doing in the automotive world, I am "standing on the shoulders of giants"... ie, I saw some dude do this online and I'm imitating it.

That said, I do tend to do things a little different than most. Everyone has told me with the SAS build that I don't need swaybars, don't need trackbars with leafs, etc- "it's supposed to be soft, that's why you built it with solid axles". Uh, no.

I am inspired by Ujoint Offroad (Ford Van SAS custom shop) and their skidpad test drive, where they drove the slalom with very little body roll, at speed. Granted their system is all leaf-sprung, but I see no reason why an air assist can't stiffen up my suspension greatly, and then give me the flexibility (literally and figuratively) I see at the touch of a button.

EDIT: here's the link: https://www.youtube.com/watch?v=J7OxIKyIGOU

If this works very well, I may go nuts and work up some electronic whizbangery via a Rasapberry Pi body control system- giving me automated height control for different conditions- such as opening the door with the engine off- truck drops to the bumpstops.

Bring on the pics.

I've settled on 3/8 line to run the bags, because it's neither too fast (not building a hopping car) nor too slow. Also, as it happens I'm in the midst of upgrading 600' of my air lines from polyurethane line to Flexzilla hybrid hose. I have more 3/8 air line than I know what to do with! If I keep this away from heat and abrasion it should be fine under the vehicle. A 5/8 Addel Clamp (stainless clamp with a rubber cushion, what is used in aircraft) every foot or so ought to work fine in that regard. Also, I have fittings on hand already - hose barbs, 1/4 NPT, and some time with a Clamptite tool and stainless safety wire, I should have no concerns of leaks.

I found check valves to screw right into the 1/4 NPT. What I'm having a little trouble finding, are Schrader valves that screw into 1/4 NPT. If anyone has ideas, please pipe up.

Sealant - what am I using? I gave up on tape long ago, although if one must, the yellow stuff rated for gas pipe is FAR superior to regular Teflon tape. But I'm a dope man, only in this regard. Pipe dope, aka pipe joint compound. I use the Oatey brand, and have enough to last the rest of my lifetime (I'm super bad about losing stuff in my shop and finding multiples later).

I have a 6" stinger coming off each bag. Plan is to have a dump valve at each bag, with a check valve as close to the bag as possible, so I have less concerns of bag pressure loss if I have a problem with lines/tank /compressor. I spoke to a guy on another project at work, they are bagging F450 trucks with link arms to support a lot of very heavy equipment. I can't talk about it much except to say it's REALLY cool, and no, you'll probably never know about it. But the guy also has bagged several of his POVs, and brought this to my attention - you don't want to tee the bags together, as you will get pressure transfer while driving, and it can actually make sway and handling problems far worse. Each bag needs to be check-valved, and of course you'll need a dump valve, unless you are only going with external-source fills. For Phase 1 I am doing the latter, just to get them in service (and my truck tamed down - it really is a bit frightening!). I will run two 1/4" lines to vicinity of my fuel filler, down to a 3/8-3/8-1/4 tee close to each bag, with one 3/8 leg capped off for future expansion when I go to Phase 2.

Anak said:

Bring on the pics.

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X2

Pictures (there aren't many, yet) forthcoming, gents- I have to figure out where to post them, since Photobucket decided to screw everyone.

Will drop some sources and my findings here as I go about the build.

Source for prefab brackets and parts:
Bottom and Top mounting plates for 2500 and 2600 series bags: http://www.bcfab.com/Lower-Airbag-Mounting-Plate--188-Steel_p_1733.html
Those are presently on sale, normally $9/per, now $5/per. A set of 4 each tops and bottoms, shipped to my house, will be $62. I really can't compete with that, the steel alone would cost me in the vicinity of $30. Now, this is not a ready to go bracket, but that won't involve much work. I'm probably going to tack these heavily to a piece of 3/16, gusseted, and then build off of that to accommodate bumpstops, trackbar bracket, etc. It won't be as pretty as a CAD-rendered bracket built up from plate bits, but I don't have that kind of infrastructure to design the build.

Clearly I'm still in the research phase..

I realized that 3/8 line I was going to use- old air hose- was WAY too large. Why? Because it's 3/8" ID, and the hose used in air systems is OD. IE- the 1/4" line that most folks use is 1/4 on the outside, and really small internally.

Great, whatever, why worry? Because that's more volume the compressor would have to supply.

The guy I was discussing this stuff with recommended 3/8 air line, but I think I'm going to go with the 1/4 for now, at least while I'm just doing it as an external-fill system. I've been looking into the different fill speeds of different sizes and 1/4 ought to be fine.

Good to note I am not completely nuts-

http://gojeep.willyshotrod.com/HowtoAirbagHigherSuspension.htm

I haven't forgotten this. In fact I've been actively gathering parts. I have 4 bags and 4 top and bottom mounts purchased. Found a deal on Ebay for 4 top and 4 bottom mounts shipped to my door for less than $30. Done! I couldn't buy the steel for that price, locally. These are laser cut and perfect.

Looking back, I could have gotten steel from the scrap yard and cut these out myself. Would have required more effort, purchase of a 5.5" hole saw (I suck at the jigsaw, and don't have enough time on my plasma yet to turn out a good product), and so on, but the point is, it's nothing that can't be built without fancy tools. a 5.5" holesaw to cut toe overall steel disc, 1/2" drills to cut the mount holes, a jigsaw to cut straight between two adjoined 1/2" holes to make slots to allow 2500 and 2600 bags to interchange, and a 1.5" holesaw to cut the clearance port for the fill port. Not rocket science- but again, for less than $4/per, yeah, let the guys with the robot do it, and ship it to me.

It rained here all weekend and most of the week. I've been dodging raindrops to figure out where exactly I am going to put these. I have two options- inboard of the leaf springs, but that requires me to box the frame so I can weld a mount to the inboard side of it. Not a bad thing, really, as I've been meaning to box the frame. Just a LOT more work, as I have to move the brake lines, fuel lines, and breather lines if I'm going that way. Again, not a huge problem and I've been meaning to reroute those from inside the framerail to up high and on the inner boxed section of the frame, as the lines are 30 years old and I'd rather be proactive with any problems. More work, and I'm not going to do it if it's not done right.

OR, I can mount them atop the spring ubolt plate. This will require the bags to be installed squashed from their "atmospheric pressure" (ie: open ports) position. Not convinced that's a bad thing, to be honest. Luckily I have the Ruffstuff 3/8" plate spring plates, as I foresaw the need to build off of them for various reasons (swaybar end links, panhard rod, shock mounts, etc:If I go that way I will fab a bridge plate to go over the top, and weld it to the spring plate, with a 1.5" hole above each nut to enable clearance for a socket. This will leave me with a super strong, flat surface that I can drill and tap to put the bag wherever I want it. I'll also probably design a landing pad in the same plate, hanging forward of the spring bolts, so I can properly bumpstop right next to the bag and avoid a lot of mess.

I'm also going to use the poly buckets at the bottom of the bags, so I don't rip them apart. I've been meaning to limit strap the suspension all around to protect the shocks, so will work that in as well.

I spent the weekend drawing up the parts I will need- the bump plates, etc, the oldschool way. Ironically, since I'm an IT Guy, I have no clue how to use any sort of CAD package. But I did take a mechanical drafting class in high school... the sort with big slanted desks, gum erasers, and Koh-I-Noor mechanical pencils. Yes, I'm an old bastard. So now I need to find a decent price for 1/4" plate without having it shipped. Worse comes to it, I can buy a 12"x12" piece at Lowes.... for $40!

Some of this will involve bending that plate. I don't have a brake, but I will cheat it- cut the opposite side with a zip wheel, cutting a slot through most of it but leaving short tabs to hold things together. Then clamp it down and use two 12" adjustable wrenches to pry it into place. Tack it into the shape I want it, then weld it all up.

So, no pics as of yet, not much to see except a messy kitchen table covered with scraps of posterboard, compass, pen and pencil, and a scruffy old guy who's crosseyed from looking at small shite all day. But, progress is being made. I am awaiting more connectors and air tubing, and the arrival of the first pair of poly bag buckets. Once it stops raining, the first bit of fab will be installing a front sway bar. That's got nothing to do with the air system, but it needs to be in place to address the body roll, and to show me what I have to stay away from up front.

So, no pics as of yet, not much to see except a messy kitchen table covered with scraps of posterboard, compass, pen and pencil, and a scruffy old guy who's crosseyed from looking at small shite all day.

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Are you me?

:looney:

Don't know, it's all a bit fuzzy....