Home built independent suspension?

[ntsqd]

As long as the trailer doesn't have brakes, I completely agree. If it does have brakes, the same system might simply need an anti wrap bar.

Sahara, what did you do with the suspension you took out? It seems like it would be just fine with something other than SREs. (Are the cool kids still using johnnyjoints or is there something better now?)

Good catch, I think that the traction available off road probably won't need any sort of anti-wrap bar, but the pavement traction could be a different story. Really depends on how much brake torque can be generated vs. the single leaf's rate.

There are a couple similar joints available now. Those from Ballistic Fab look to be the nicest that I'm aware of.

 

[LandyAndy]

Really interesting thread.... esp since I've got most of the parts sat in the shop to build a trailer next..... erm..... soon.

Anyway.... for my 2c.... if your building, on don't loose sight of the fact that it will most likely get bashed, dropped off ledges & generally hammered off road.

Having suspension that has adjustability is great as long as it doesn't self adjust, just as your trying to get round a large rock or tree stump. At that point when the trailers all hung up, keeping it nice & simple with all welded & gusseted joints just seems to be so much less to go wrong.

So, I guess the question really is..... are the benefits of adjustability really needed for a trailer that might only see low Km's each year. I can't answer that for you but it's something to throw into the mix if your still sat on the fence.

And remember the off-roaders proverb... when your in the bush it will break, at the worst possible time and with the spare sat on the shelf at home, cause you've never needed to use it in the past 'x' years !

Happy fabbing :safari-rig:

 

[ntsqd]

I'm reminded of a saying in light aircraft: "You can take a perfectly good part, put it on an airplane, and it will fail."

With the trailing arm(s) parallel to the tongue the arc of travel produces a tire motion that tries to retreat from the bump it has encountered. It is for this reason that the VW Bug's suspension design was so dominant in U.S. desert racing for so long.

With the suspension links perpendicular to the chassis centerline there will be a large loading of the inner pivot points when the tire hits a bump. The further these pivot points are horizontally apart the better, but the length of the links is the primary factor in lever arm that the bump force has against those mounts. With a well thought out SLA design you might be able to generate a travel path that also retreats from the bump, but I suspect that some serious compromises in other areas will have to be made.

I don't know about these air springs, but those used in the rear of the GMC motor coaches could not be relied upon to maintain the leveling overnight. This was a frequent complaint that my grandfather heard from other owners at the various GMC Coach rally's that my grandparents attended. My grandfather never bothered to try. He used the air springs to get level and then blocked the chassis at that point.

 

[Jerry L]

It is amazing how much head scratching that went into my trailing arms and I still got it wrong. DOH!

My first set of arms had undersized hiems and no brakes. They worked fine untill I towed the trailer over 20 miles of washboard dirt road. The hiems didnt break but they did bend causing major camber change.

The inside hiems took the most abuse. I totally under estimated how much twisting force was being applied.

I then built a second set with electric brakes and urathane bushings instead of the hiems. These arms work awsome!

I believe the solid axle and air bags is a great idea and it would be alot easier on the joints. Hiems or johnny joints like compression/extension forces better than twisting ones.

 

[IdaSHO]

That looks great, but you lost the ability to adjust the toe alignment

 

[LandyAndy]

The above posts sort of sum up what I was trying to say.... stick with 'garden shed backward engineering 101'.

1. Look how the manufacturers have solved the problems, cause they've spent mucho time & $$ doing it.

2. Locate parts that are easily available & come up with a simple alternative.

3. Double up all the fixings sizes & material thickness to allow for failure, cause you don't want to be making this thing twice.

Get out and have some fun with some degree of confidence your creations not going to fall to bits on you.

So, what you have might not be the lightest, might not tow 100% perfect on the highway (this is an off-road trailer) but at least after a few days/weeks hammering the crap out of it on the trails you can still make it home without having spent half the trip on repairs.

The above is based on may years of experience of making things twice

 

[UK4X4]

"I then built a second set with electric brakes and urathane bushings instead of the hiems. These arms work awsome!"

Urathane bushings........wait a while...............you'll find the inboard bushings will deform !

as I have the same, its not much , but measurable, about 3mm

This is about 4000km after finishing the trailer

with some serious washboard and desert pistes as a majority of the distance

down the road mine will need replacing, not a biggy but something to concider

toe in toe out, slotted holes in the inboard mount.

camber - shim it

also don't do gas shocks and airbags, better go with standard oil

the independant works awsome off road,but on road mine is too alive when seen in the mirror.

I've been concidering adding "roadstraps"

limiting straps each side then pressure up the bags against them so the suspension is harder and limited for high speed road use.

arrive at the trail air down and remove the straps

Leaks....I don't have any.........but then I'm using 10,000psi swagelock fittings !

really though, I enjoyed building mine, and love the technology

but for standard usage, some long leaves and a standard setup is quite sufficient for normal usage.

 

[lowenbrau]

<snip a bunch of sage advice>
The above is based on may years of experience of making things twice

I hope to someday achieve the only-do-it-twice stage. I'm still a "third time's a charm" type of guy.

 

[dieselcruiserhead]

This is great to see. My 416 build thread is somewhere (EDIT - here is the link). I had a lot of warpage with welding and I mistakenly aligned my arms off the design rather than the wheel mounting surface. When I finally aligned them to the WMS I perfected the trailer and it was amazing how well it came out. I'm not sure I would do independent again mostly because it takes SO much time and labor. I would do something very similar to what is above which is a 3 or 4 link, or a radius arm solid axles with air bags. But this is great to see and great to see some updates on.

The final product of mine. Towed like a dream, handled anything with grace, and you didn't notice it behind you. Everything was perfect about this trailer particularly including its size. Not to big, not too small, not too heavy and not too light.

Delrin bushings that were custom machined. Jeep 4cyl rear OEM shocks. Largely modeled after the AT designed arms. Theese arms clearly would have been rejected by AT standards but when aligned at the WMS they did great and were also indestructible and worked perfectly. It also needed a heavy duty cross member as well (added in at the last round before final powdercoating).

 

[G-force]

So, i really like all the info i am getting in this tread:sombrero:

I am still going for airbags as springs, and adjusteble shocks of some kind. Searching for these, i came over these at Summit:drool:

(Picture borrowed from Summit)

Any of you tried these out? As i understand, this allowes for less fabwork, and an easier and cleaner system. And yes, they look freaking good:elkgrin:

The prize . . . . . Well, i`ll probably just buy and forget about the prize. And hopefully in time, i`ll find them to be worth every penny.

Input?

Dieselcruiserhead: can you please tell me how much your trailer weighs in at?

 

[G-force]

Bumping this one up again.

closer to begin my own trailer these days, and are in need of input :sombrero:

 

[Arya Ebrahimi]

I'm still in the building phase, but my suspension is nearing completion. Check out my build thread here: http://www.expeditionportal.com/forum/showthread.php?t=32267

 

[G-force]

Your buildtread is allready in the subscrpition folder :elkgrin:

And i really like what you are doing. Pretty similar ideas as i have, for the suspension solutions. Can i ask where you got the airbags from?

 

[Arya Ebrahimi]

Your buildtread is allready in the subscrpition folder :elkgrin:

And i really like what you are doing. Pretty similar ideas as i have, for the suspension solutions. Can i ask where you got the airbags from?

www.suicidedoors.com They had them on sale at the time. They're Air Lift Dominator D2600 bags.

 

[JPK]

The difficult thing about trailing arms is that each weld makes the tubing bend in a given direction. Once all the welds are completed you pray it's all square. You pray it's square even when the assembly is clamped on a welding table in a template.

Adding to the issue is getting the spindle welded into the tube at 90' to vertical and horizontal. Did I mention that nasty internal seam on the tubing that needs to be addressed?

We have a 15 - 20 % rejection rate on trailing arms. And before anyone asks we dont sell the rejects.

I don't know much about welding, but I do know that when the welders who work for my company have a tight clearence, critical dimension weld to make they use liquid nitrogen to keep the pipe or other steel they weld from distorting.

I guess that the liquid nitrogen doesn't affect the weld or its penetration, but apparently keeps the pipe or surrounding steel from distorting as much as it would otherwise. Our welders do this for high pressure hot water and steam piping and also for pressure vessel repair. The welds are performed under the watchful eye of an independent inspector, pressure tested and stamped when they pass.

Maybe someone who knows more about welding could chime in about using nitrogen or something else to limit distorsion?

JPK