Cutting into the frame to accomodate longer coil springs for a rear 4-link
- Thread starter truggier
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If you have an Engineer friend or are capable yourself calculate the cross section inertia of the original vs your proposed design. Make yours stronger and then you can cut the frame and have less compromise in your design. That is what i would do.
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- #23
That's crazy but cool...never heard of such a thing. I was planning on having onboard air, I'll have to look into it. I wonder what DMV would think of it? Ah, decisions...
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- #24
I used to work for Lockheed Martin as a structural design engineer (hence my fondness for solid modeling). I jumped careers completely 13 years ago, but probably could blow the dust off the books. It's a simple statics problem. Intuitively I know what I was proposing is stronger than stock - I was mostly worried about stress concentrations and fatigue resistance. I wonder if they make Finite Element Modeling software for the PC these days.
Look up Xtreme 4x4 tv show, project saggin wagon. They 4 linked the rear of an fj60. They cut the back half of the frame totally off and fabricated a simple rear end framework to accomodate all the changes. Sometimes it's easier and alot better to build what you need, rather than try to modify and make sacrifices on an existing structure. Think outside the box. Good luck.
Have you thought about trailing arm? It gives you a smoother ride, and takes advantage of shorter springs.
Check this build out.
http://www.pirate4x4.com/forum/toyota-land-cruiser/977913-way-too-slow-fj40-build-2.html
Check this build out.
http://www.pirate4x4.com/forum/toyota-land-cruiser/977913-way-too-slow-fj40-build-2.html
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- #27
Getting interested in the air springs...doesn't look like I'd have to change much. Firestone 1T14C-7: compressed = 6.8", extended = 21.7".
Here's a writeup where someone put these in a Land Rover, doesn't look that difficult:
http://www.aulro.com/afvb/projects-tutorials/156574-110-air-spring-conversion-rear-axle.html
They don't look as 'cool' as conventional springs though.
Here's a writeup where someone put these in a Land Rover, doesn't look that difficult:
http://www.aulro.com/afvb/projects-tutorials/156574-110-air-spring-conversion-rear-axle.html
They don't look as 'cool' as conventional springs though.
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- #29
I'd be SOA on the front with these bad boys on the back. Need to figure out how to work in bump stops.
I vote for a cantelever swing link dealie that compresses a coil over that is mounted horizontally under the cargo floor fi style. Thats all I got lol.
D
D
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- #31
Love all of the ideas, though I think it's contributing to my ADD.
How's this for slightly insane (and expensive) - what about combining the Firestone air springs under the frame with dual-rate emulsion coilovers (emulsion because they're way cheaper)? That way I'd get the stability and load carrying capacity of the air springs on the road, but could air them down and use the coils on the trail. I could use the air springs to force articulate in hard spots. Also, I'd have redundancy if an air spring popped - I could just run on the coils.
I'm also wondering about putting air spring helpers inbetween the leaf and the frame on the front SOA in place of bump stops. Better ride, prevent sag, and possibly forced articulation?
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- #32
By the way...do you have a reference or any more info for the 'with positioning shackles radical travel is possible' part of this?
15 years ago, I saw a Suzuki SJ410?? with air bag suspension. Rather than having the top of the bag secured to the frame, it was attached to a shackle that ran parallel to the frame. Therefore, the airbag didn't limit droop. When loaded the shackle sat rested against the "Frame" and then when unloaded, it dropped down an extra 8-10". I'll look for a reference, but I saw it in person at a local IRC rock crawl here on Vancouver Island.
Love all of the ideas, though I think it's contributing to my ADD.
How's this for slightly insane (and expensive) - what about combining the Firestone air springs under the frame with dual-rate emulsion coilovers (emulsion because they're way cheaper)? That way I'd get the stability and load carrying capacity of the air springs on the road, but could air them down and use the coils on the trail. I could use the air springs to force articulate in hard spots. Also, I'd have redundancy if an air spring popped - I could just run on the coils.
I'm also wondering about putting air spring helpers inbetween the leaf and the frame on the front SOA in place of bump stops. Better ride, prevent sag, and possibly forced articulation?
I'd not run coil overs and air. Rigs have been running air suspensions for at least a decade... If in doubt, carry a spare air bag.
On the front, I can see an advantage. Some day, I'd like to add them to my rear SUA to combat sag and improve ride. I've got plenty of rearched leaves, but they struggle with the 2500+ lbs I've got on the rear axle.
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- #36
I guess what makes me nervous about the air springs is what if one pops at high speed, say on the highway...the rig would lurch to one side and control would be difficult. Pretty much like blowing a tire.
You don't need to cut the frame to fit coil springs... see my build thread in the Hardcore section (https://forum.ih8mud.com/hardcore-corner/618203-project-resurrection-v1-1-a.html) for reference. Rear double triangulated 4 link with front coils from a 6 cyl Jeep TJ. Packaging is tight with a cruiser width axle, but the suspension cycles without the tires rubbing the springs or frame. From the looks of it, you have your rear axle sitting in roughly the same location as I do... pushed back ~12.5".
80 or 75 series coils would obviously work if you want to stick with Toyota, but TJ coils are cheap and spares can be had in just about every junk yard and they're considerable smaller in diameter than LC coils so packaging is more in your favor. You can also get lift springs in smaller increments for the TJ's for much less money than LC's.
80 or 75 series coils would obviously work if you want to stick with Toyota, but TJ coils are cheap and spares can be had in just about every junk yard and they're considerable smaller in diameter than LC coils so packaging is more in your favor. You can also get lift springs in smaller increments for the TJ's for much less money than LC's.
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- #38
Love your build. It's a lot like mine will be. Why does it look like you have more space between your lower spring bucket and the chassis than I do?
My wheelbase is 103", which is about as far as you can stretch it and not have to cut your fenders too radically. The rear is pushed back 10" and the front is pushed forward 3" due to flipping the front leafs.
Those springs look very flexy. Are you concerned about load capacity at all?
I'm curious why you rebuilt the back chassis - what you put in looks pretty much the same as stock except for the crossbracing, except it is much stronger. Why not just box the stock chassis and reinforce the rear most cross member / bumper mount?
Spring rate? Amount of weight in the back end?
Right now they are very flexy. If the rear end doesn't drop down any more than 2" from where it is now I will probably keep these springs in. Otherwise I will get a pair of 1.5" lift springs, or see if there's stock height available in a slightly higher rate. The factory TJ coils are ~175 lb/in.
Rust. The factory diagonal braces were only (barely) attached with the 2 rivets on the top of bottom of the frame rails, and flopping at the rear X member. The rear X member and rear sections of the frame were in pretty bad shape too. Almost nothing left to weld to. The replacement sections of frame rail are 2"x4"x.120" and the rear X member is 2"x4"x.188".
