Home built independent suspension?

[RAM5500 CAMPERTHING]

DISCLAIMER: I AM NOT A WELDER OR A FABRICATOR!!!

Ok, right off the bat, i am NOT a welder, or a fabricator and usually cut myself on anything sharp, i dont know crap about the subject, so i wont pretend to talk as if i do.

WHAT I DO KNOW:
Is that Metal Twister knows his stuff, argue all you want, but it is because of Metal Twister Aka Uncle Bob (no really my uncle) and his knowledge of welding and metalurgy that two of my friends are alive today.

As you know, our Baja1000 effort ended in a horrific barrell roll down a 700ft cliff. Well, Uncle Bob and his 20 year old son Robert are the reason that both occupants are still alive, one escaped without even a bruise.

We designed most of the cage, but "Uncle Bob" adjusted some things that he thought would be safer and his son Robert and Himself did the final welding after we tacked it together. They spent 30-45mins adjusting gases and such and making sure the welds we perfect, bla bla bla.

Finish product of the cage, came out amazing, when we brought it to SCORE tech to get the "tag" for it, Bill Savage (builds rigs that race DAKAR) even complimented/commented on the weld work and passed us with ease! Bill is usually a grumpy old guy, but was honestly smiling and checking out every inch of the cage commenting on how the welder did everything perfect, not a single mm of bead had a void, knew his poop, etc....

Unfortunately we dont have pics of the wreckage of the rig, but the cage performed flawless with a 6500lb truck barrel rolling down a cliff and saved my friends lives!

I will side with "Uncle Bob" on this one and if he says something will work, you should listen to him!

Or, the question will be asked (by me): "What have you done, or who have you saved to back up your reasoning?"

Also, i have personally driven and beat the living SNOT out of some of the sand cars he built, racing from Glamis to Gordons Well at WELL over 100mph, launching them off jumps and simply driving like "That Guy" and have not ONCE broke or cracked anything he has made.

Sorry for the rant, but "Uncle Bob" is the man, knows his stuff, saved 2 lives, and will be building my chassis for my 5 car!

Carry On!

 

[UK4X4]

no need to rant....

cromoly tubing just is'nt something you can weld at home with a mig

which most of us here use in our little garages......

unobtanium as used by NASA may mean I can use only 1/4" 0.049 wall tubing.....

But if I need a special welder, special wire, special conditions, a oven, a tempering bath, a hardness tester and X-ray inspection.........

The words home built independant suspension does not mean much

Now if he can specify that we could use X size dom tubing, lighten the weight
and change the design slightly to enable Homer Simpson to weld it up in his attic and it will do the job.....

I welcome the input...please don't take this the wrong way...I'm only 1 year into hoby welding and do need and apreciate responces......:arabia:

especially from an expert:bowdown:

 

[oldcj5guy]

Yeah, what UK4x4 said.

Wasn't saying twisted didn't know his stuff.

I was saying that most of the joes on this board don't know how to play with chromoly. I have bilt several cages in my time and a couple of scca cars, and I still have no clue how to play with chromoly. Think i'll have to learn one of these days.

 

[Metal Twister]

Hey Kevin, Thanks for the kind words. I apologize for stepping on this thread. Just so you guys know, I was a sales rep for a couple of the larger welding distributors in San Diego for 20 years. I’ve been very fortunate to work with some of the brightest cutting edge welding engineers there are. I also spent hundreds of hours in training with the manufactures of the welding machines and robotics. With all that said, welding is a very subjective science with thousands of variables. Everything from the atmosphere to the angle of the arc makes a difference in the weldment. I have a hard time when I hear that the RIGHT WAY, or the RIGHT PROCESS is... There truly is many ways to skin a cat. With today’s technology and electronics the welding world has busted wide open. I’m not saying that older proven methods aren’t good. But maybe newer, quicker, and easier methods are better suited for the novice welder. I weld 4130 as most off road chassis mfg. do with a short arc mig machine. Just like the one in the garage, a Millermatic 185. We trigger weld the welds making sure there is no cold lap in the weldment. We, as well as most chassis builders use c25mix gas. (Mig Mix) we use an e80sd2 .o3o wire. No pre heat required no post heat required. The reason we use a softer wire than the 4130 is to allow the joints to flex. If the moly was welded with 4130 filler metal it would not flex, causing cracks, and weldment failure. If you were using 4130 filler metal, stress relieving would be required as well as pre heat. Which brings me to the point of how good are your welds? When I read about someone that is going to put a vehicle on the public roads, I would hope that they have had enough experience welding to insure the safety of his creation as well as all who may be around it. At that level of welding competence you should have no problem welding 4130 in the garage with the home 220v welder. With today’s liability climate... well I won’t even go there.

Anyway, I am sure that we all have a level of comfort with the process, equipment, and materials that we have had experience with. My suggestion is that you work with in those parameters and don’t make it more difficult than it needs to be. I really do apologize for the detour here. If in San Diego stop by the shop And I will show you how easy the process really is. Press on and enjoy.:wavey:

 

[Pskhaat]

I really have nothing to add of value here but I will ask a question? I'm sure a few of you guys could easily answer:

Aren't many non-steering independent rear suspensions designed to give a little toe-in during the down cycle? There's been some talk on camber and toe and maybe the toe question is moot as the camber is on something like this, but don't many mfg's slightly angle the arms to provide this toe-in at drop?

 

[UK4X4]

"cromoly tubing just is'nt something you can weld at home with a mig'

oops looks like I was wrong there...


So much for the hours wasted reading roll cage threads on pirate.

Now that just adds another material for me to research........:smilies27


Ref the worry about dodgy homer simpson welded creations falling apart on the road...................

Funnily enough I did used to work at an atomic research station and ate doughnuts for breakfast this morning

 

[GeoTracker90]

Ref the worry about dodgy homer simpson welded creations falling apart on the road...................

Funnily enough I did used to work at an atomic research station and ate doughnuts for breakfast this morning

That's funny! Just last week at work I was talking to one of our part time guys that also does work in the nuclear field and he was telling me of a small isolated contamination problem. (Can't remember where or when.) I told him about the opening of "The Simpsons" where Homer leaves work with the glowing green piece of nuclear fuel hitching a ride with him. I couldn't believe that he hadn't seen that opening bit before. I thought that was funny too.

Sorry, side track over - return to the suspension discussion.

 

[Metal Twister]

I noticed that in my first reply here that I said I would use 3/4 " moly on my arms. My bad, I could of swore I wrote that i would use 1 3/4" Now I see what the problem was and you were right!!! Never use 3/4 " .120 wall on trailing arms.Sorry guys for the screw up. Bob

 

[ntsqd]

Neither was I. My intent was to caution those who might try it w/o realizing the pitfalls. However, for my own use I fail to see any advantage to not going to full distance with 4130. It is either a 4130 weldment or it is a mild steel weldment. If others wish to make those sets of compromises it is their choice.

If the pivot points are angled rather than straight across the width of the trailer, as was mentioned, then the arc of motion induces both a camber change and a toe change.

 

[Metal Twister]

Neither was I. My intent was to caution those who might try it w/o realizing the pitfalls. However, for my own use I fail to see any advantage to not going to full distance with 4130. It is either a 4130 weldment or it is a mild steel weldment. If others wish to make those sets of compromises it is their choice.

If the pivot points are angled rather than straight across the width of the trailer, as was mentioned, then the arc of motion induces both a camber change and a toe change.

Back when most aircraft was built with 4130 it was used for its high tensile/ yeild strength. It was the metal of choice because it was very thin and very strong. Back then they had two ways to weld it, Stick or oxy actyelene. The goal was to build a light weight, strong airframe. Then climbing in and flying it. The down side is that with the high strength it becomes very brittle with high heat. That is why the weld perameters were established in the first place. Fast foward 50 years, now we are welding on the same metal but a thick.120 wall with and electric arc, small wire, and just enough heat to get the job done, not a Flame. The aircraft was held as rigid as possible, there just was no need to build it for impact, sharp bumps and bangs. If you were to build an all terrain vehicle with that process it wouldnt last very long. The weld joint has to flex abit, if it dosent, something will flex on inpact, and then breakage is the result. That is why an 80,000psi wire is used. It will allow a little flexability without snapping. Im sorry for making this sound so basic, I just want the garage guys to understand what is being said here.

As far as putting the bend in the cross bar. I want to be sure that everyone knows that I was refering to a long travel sand car with a transaxle, not a trailer. And yes camber and toe is built into it. I hope this clears thing up for us all. I really didnt want to turn this into one of those welding threads that go forever, so Im done here. Thanks for patients on this. Bob

 

[UK4X4]

A few pics of a home made independant suspension from Chille borrowed from the twisted andes site posted on the "is it copy" thread.......funnily enough you may recognise the finished item

 

[ntsqd]

Back when most aircraft was built with 4130 it was used for its high tensile/ yeild strength. It was the metal of choice because it was very thin and very strong. Back then they had two ways to weld it, Stick or oxy actyelene. The goal was to build a light weight, strong airframe. Then climbing in and flying it. The down side is that with the high strength it becomes very brittle with high heat. That is why the weld perameters were established in the first place. Fast foward 50 years, now we are welding on the same metal but a thick.120 wall with and electric arc, small wire, and just enough heat to get the job done, not a Flame. The aircraft was held as rigid as possible, there just was no need to build it for impact, sharp bumps and bangs. If you were to build an all terrain vehicle with that process it wouldnt last very long. The weld joint has to flex abit, if it dosent, something will flex on inpact, and then breakage is the result. That is why an 80,000psi wire is used. It will allow a little flexability without snapping. Im sorry for making this sound so basic, I just want the garage guys to understand what is being said here.

FWIW, TIG/GTAW/heliarc/whatever you want to call it was available then. It was judged too exotic to use on a large scale.
The basic problem is that most other weld options result in highly concentrated heat, which results in a brittle Heat Affected Zone due to the surrounding metal being a comparative iceberg relative to the weld metal and causing it to cool too fast. Really not much different than sticking the still red hot part in a bucket of water. Oxy-fuel isn't concentrated enough to yield those results since it heats a large part of the surrounding tube. I'm quite sure this is old info to some.
If you can get the penetration w/o heating the metal over the transition temp and in turn creating the possibility of freezing the metal in the brittle crystalline arrangement, then this won't be an issue. I'll not claim any experience or knowledge with MIG welding of 4130. It certainly would beat 'wash-welding' for speed of fabrication with appropriate fillet sizes. For my uses, which are not large structures, I'll continue to do it the old way.

I do not see the camber resulting from an angled pivot axis as being worth the toe change in a trailer application. For other applications I know it is desirable and can be exploited to be a hidden advantage (camber, not toe er, bump-steer). I just do not think it worth the compromise required for this use. With a toe change comes the potential for the trailer to 'steer' itself. In a driven vehicle you have steering to help with that. Not so in a towed vehicle, at least not in a practical manner.

 

[GeoTracker90]

Although the discussion over materials and weld processes has been interesting, I think that it is a topic unto itself and should not be hidden in a thread about a home designed and built independent trailer suspension.

In contrast the discussion about having the bushing pivot points off set from each other and how that translates into geometry changes as the suspension cycles has brought out points that I haven't considered before. Overall I have enjoyed everyone's comments and the thought that it has provoked.

That said, I do wish that there was a little more discussion as to the merits of different suspension designs. I've seen trailers that have two individual bushings where the trailing arms attach to the chassis. I've also seen designs where there is one long attachment point for the trailing arms. What are the advantages and disadvantages of each design? If you choose to use air bags for the suspension what brand and part number have been used and what are the results? If you use coilsprings what are the specs and sourcing on them? Should the idea be scrapped all together and just go with a solid axle and longer leaf springs such as some from a Suzuki Samurai instead?

Just saying.

Mike

 

[UK4X4]

For me the seperate bushings make more sence, however costs more.....

but also makes bushings of the shelf

The a frame will be made on the trailer all clamped in place as its the flatist thing I have in my garage, ie built and welded in place.

the bushing mounts however will be just tacked in place.

I'm not going to worry about toe in camber adjustment unless I Homer the A frame......

Then it will be a quick grind and re-position the mounts, either shimmed or moved.

I like metaltwisters input about the lazer...thats a neat way of testing the movement.

If you check my last post and look at the pics of a chilean self build, he's just used standard box section.

Springs...I've got two airbags in the garage, I'll dig out the part No's later as it took a while to track down a thinner tall one with longer travel, I think I paid $ 65 each

I went firestone, rather than "chong" enterprises

results...well that'l just have to wait for now...

For coil springs I'd be looking for springs matching the expected weight of the finished trailer mid way between fully and empty

 

[Metal Twister]

Like I said earlier. I like the simple approach, I would use airbags, two bushings, a brand name air bag with the height required for my design. I would probably fab up some kind of trick 2 inch hollow spindle only because I like to be different and i have the machinery and skills to do it. But with all that said Im no expert on trailers and am anxious to hear how the experienced trailer fabricator would approach it.