Need some input.

[CruxGNZ]

Before I put these on my car, I wanted to show them to you guys. I'm no engineer (well, no degree anyways), so I wanted some input from you guys. Does anyone see any problems with this design? It was conceived by a guy at a local speed shop that specializes in circle track cars and myself. Barely cost anything to make. It's a very simple design, kinda different from what I've seen, but it works excellent. 1 7/8" of total movement. The only thing I was worried about was the black pipe that holds the bushing, will it be sufficient enough for it's application? It's schedule 40 black pipe I picked up from the hardware store, with a bolt that I welded to it. Should I brace it some, kind of like the stock control arm is with reinforcement around the circumference of the bushing tube? Any input would be greatly appreciated. Hopefully you can see everything within these pics. Kind of a crappy camera.

 

 

 

Thanks,

 

!M!

[Guest Anonymous]

Looks very interesting for an adjustable front suspension lower control arm design. I would go with fine threads since they are stronger than coarse threads. Grade 8 bolts. I would be concerned with your pipe selection. A welding expert member could comment on the type of welding to be used for strength. There is definitely some higher grade pipe with thicker walls available from large machine shops or supply houses. I am impressed with your job but feel your selection of pipe and method or type of welding (heliarc, TIG ?? MIG may cut it) the bolt to the pipe needs further Research and Developement I am saving this thread!

[CruxGNZ]

Actually, they are fine thread, you really can't tell from the crappy pictures, sorry. Regarding the bolt attatched to the tube, it's just MIG welded on there. I tacked it, made sure it was stright, then welded around the head of the bolt. When it cooled, I went around that weld with another weld, making the total weld bigger in diameter. I'm not sure that making these "doubled up" welds is good practice, but it made sense to do it. I have not taken any welding classes or nothing, so I don't know the proper way of doing this, that's why I figured I would put this out for you guys to see, BEFORE I put it on my car.

 

!M!

[Guest Anonymous]

The pipe end is the only thing that I'm not so sure is the right material. I think maybe even DOM (drawn over mandrel) or mild steel tube like they use on roll cages would be a better selection, the rest of it I like, good job.

 

Just a gut feeling, as I don't know the strenth of sched 40 pipe, I do know no one that I've seen uses it in that application so I'd be really leary and nervous in doing so. Not a critism as much not wanting to see you get hurt if it breaks.

 

Regards,

 

Lone

[ZROSSA]

Cool Mat. Try to put a gusset of sorts all the way around that pipe. Get a big washer shaped piece of metal that inside diameter will just slide over your pipe. You will need two. Slide them over the pipe and weld them. also weld them to the head of the bolt. I was looking at welding a bolt to pick up a lower shock mount on my corolla and a engineering friend said he didnt like to weld hardened bolts to softer metals. You may want to check that out. The last thing you want to happen is the bloody wheel flying off.

 

Douglas

[CruxGNZ]

Yeah, I agree a couple gussets would be needed on each side of the bolt. I think I'll use some 12 gage steel (possibly thicker) to fab them up, or the hardware store might possibly have a washer with the correct inside diameter to fit the outside diameter of the pipe. Before that, I want to find out more info. on welding hardened bolts to softer materials. I hope I didn't make these adjustable control arms for nothing, but then again I'm learning quite a bit. Anyone know anything on welding hardened materials to softer materials?

 

!M!

[Guest Anonymous]

Your welds look good and your welding overlay method is apropriate but it is that Black Pipe. A gusset to the pipe and bolt would improve things. What I would be worried about is the bolt ripping or shearing loose from the cheap metal in the black pipe. I once extended a standard hydraulic jack by about 20 inches for a cherry picker application by replacing the outer cylinder pipe housing with scrap pipeand hydraulic shaft plus a new inner hydraulic tube in longer lengths.The seamless inner tube/pipe was $2.00 per inch and would not rupture under extreme pressure. This big machine shop had all kinds of speciality tubing and pipe for sale in about every flavor imaginable.The salesman also gave me lessons in pipe out at the pipe shed.I still can (after 15 years of use) jack a motor up and leave it hanging two weeks and that jack shaft might move down about 1/16 th of an inch.That expensive hydraulic tube is tough.

[Mike kZ]

I would take a piece of flat stock about 1/8 inch thick, weld one end to the bolt head, then heat and mold the flat stock around the pipe to the other side and weld it to the bolt head again. This would encase the pipe, and you could seam weld the edges all the way around.

[Dan Baldwin]

I'm not too worried about the pivot end, as there's no bending there. I'm more concerned with the portion of the bolt that has to take the full vertical bending load at it's outboard end, just inboard of the adjusting nut(Or am I not seeing something?). I would try to use stubby steel sleeves sandwiched in there to prevent the bolt from having to take the bending load. Of course you lose ease of adjustability there, but that's what I'd do. If any of the bolt has to take all the bending load, it should be the inboard end. The control arm is basically a simply supported beam-column, with the sway bar attachment being the point of maximum bending. Bending drops to zero at the inboard pivot and at the ball joint.

 

Dan Baldwin

M.S., B.S. Aerospace Engineering

[katman]

I generally hate using a bolt in anything but a shear application, especially when the threads are involved, so I always squeal a little when I see people try to make something like this. Especially at the rear control arms for several reasons. I've also commented off line to some folks who've done this sort of thing. Race cars get away with it because we inspect them all the time to catch fatigue problems, and a threaded bolt in shear and bending is gonna be a fatigue problem. Plus we have a real cage for when it breaks.

 

That said, the stresses involved are generally below the endurance limit of the steel, even when you consider the threads etc., so I can't really say it ain't safe if the quality of manufacture is up to par.

 

However, I gotta ask why? Have yet to see one of these lighter or with more damage tolerance than a stock part. Don't we usually adjust camber with camber plates? I've considered this for my project but I keep coming back to "why change from stock?"

 

Now for the rear it'd be nice to have toe adjustability. But depending on where you locate your bolts you could have some real bolt bending problems in the design of a rear control arm. But for the front I'm missing why we need threads.

[CruxGNZ]

Katman asks why? I was bored. I've seen adjustable control arms done before, so I figured I would try and make one myself that retained the stock bushing, so it kept a great ride around the city (around here the roads are very crappy and I didn't want a solid mount). I guess some of you were wondering how it worked, well the bolt that screwed into the remaining stock control arm was left hand threaded and the inside of that left hand threaded bolt was right hand threaded, meaning that it would be on car adjustable, really neat for only $23 worth of stuff for both control arms. I did NOT want to put this on my car before I let some more people look at it. Like ZROSSA said, I don't want my bloody wheel flying off. This car will see some serious street use, so the parts need to be strong. I made the gussets to go around the black pipe and almost started welding, but then I started to think, "what if something was to break?" I have nobody to blame except myself. If I was to crash and hurt or worse yet kill somebody, because my adjustable control arm failed, I couldn't live with myself. I am going back to stock front control arms and camber plates. I still think this adjustable control arm design has potential, but I completely forgot about the bending loads of the front sway bar. This fatigue in time may cause a failure. I am going to stick with what works, camber plates. The only thing I DON'T want is camber plates for the rear of the car. I don't want noise transmitted into the vehicle via the camber plates. What have you guys done to keep it quiet? I have coilovers if that helps and nothing is put together as of yet.

 

Thanks guys,

 

!M!

[pparaska]

I also hate to see threaded parts in bending - threads are stress concentrations, especially when bending is involved. It's good to see practicing mechanical engineers like Dan and katman comment on these things (I is a M.E., but hardly "practice" the stress weiner stuff anymore - unfortunately).

 

I think providing 1-7/8" of adjustment is overkill anyway. If you made the threaded part shorter, it'd still have adjustment, and it'd be farther away from the large bending moments near the center part of the arm.

 

The black pipe doesn't bother me that much. The gussets sound like a good idea.

 

Pete Paraska

M.S.M.E

[Dan Baldwin]

To get more negative camber at the front, I lengthened my control arms 9/16". Used rectangular section tubing on top and plate on the bottom, all suitably scarfed in to avoid an abrupt change in x-sectional stiffness. Went from ~1.5 deg to ~2.5 deg negative. Big improvement in front grip, and 225/50ZR15s stilll don't rub anywhere (on zero offset wheels). Changed my caster a bit, though, now it's like 2.5. I know, that's supposedly WAY too little, but I like the way it handles and the light effort required at the steering wheel. It feels like I've got servo-assisted steering, kinda neat. Just think at the wheel and you've rotated the car. Wheee!

[ZROSSA]

Mat, How about using the strut to take the roll bar loads? Then there is no bending on the lower arm and you would probabley get a more direct responce to the roll bar. All the opels/holdens i have seen do this. It would mean that you would get more leverage on the bar so it would apear softer. You look very handy with the welder so it should be a piece of piss.

 

Douglas

[blueovalz]

I thought I'd share this with Katman. It's my experimental version (not quite finished) with an adjustable toe-in rear arm. The threaded tube portion of the rear arm was removed (on the rear only), A grade 8, 3/4" fine thread bolt (with head removed) was pressed into the tube (perfect fit) and then spot welded into place at two places. Then the female Heim joint (which is not the one shown here) in screwed onto another 3/4" bolt attached to the plate (via a block that allows the bolt to turn for adjusment of the toe-in) that originally held the OEM bushings. That block piece required some machining which is being done at this time.

[johnc]

Adjstable toe rear control arms don't have to adjust very much. I get all the toe adjsutment I need with offset Kevlar rear bushings. I might even install a set of offset monoballs if I ever run out of things to do to the car.

 

Schedule 40 black pipe? On a car? Ya haulin' moonshine with the thing...

[blueovalz]

Yeah, currently I am using a "cresent moon" piece of schedule 40 1-1/4" pvc pipe 1" wide to push the bushing over the correct amount (the bushing was shaved on the opposite side to allow the "push". Unfortunately, when I removed the crossmember the other day, the PVC had broken up and fallen out onto the floor. That's when I decided to try this option. If testing it works to my expectations, I may attempt a repeat on the front bushing change too that will thus allow camber adjustments too.

[260DET]

What DAW said re the fronts ie use eccentric camber adjusters and retain the light stock arms. Best to remove the X member to do this so that the weld on lipped plates can be inset, then welded into the X member. At the same time, you can raise the pivot points, if you are going to lower the suspension, so that the arms will still be around parallel with the ground under static load.

 

Use other stock eccentric adjusters as DAW suggested, or maybe a suitable aftermarket kit from a suspension upgrade place. I'm in the process of doing this, waiting at present for the correct pivot relocation measurement details so camber will be adjustable up to 3.5 degrees negative.

[CruxGNZ]

Douglas, that sounds like a pretty cool idea! Using the strut to take the loads of the sway bar would help out a lot. I'm going to search for some suspension photos of the Aussie cars to get a better idea of this.

 

Hey John, I'm sorry, but I have no idea what you meant about haulin' moonshine... was the black pipe a bad idea? I just used it, because it was pretty thick and it was the perfect size for the stock bushings. I really didn't think it was very soft, because it was a bear to cut with the chop saw. I did notice something that I didn't like with that pipe though, after I cleaned it up to weld on it, I noticed little lines going through it horizontaly, kind of like it was put together with two pieces.

 

I do have to mention something that I forgot, the way the left hand threaded bolt attatches to the remaining stock control arm is by means of welding two jam nuts together, then welding those to the plate that I made to attatch to the remaining stock control arm. I found a left hand threaded tap to use in a block of steel instead of using the two nuts and a plate, but the tap was about $40. Then, if I WAS to use a block of steel tapped out instead of the two nuts welded to a plate (I used 2, because the extra threads did sound like a good idea), I would have to make sure I got the right kind of steel, so the bolt wouldn't just pull out of the block. You guys following me here? Hope this makes sense to you all. I had no idea what kind of steel to use. Maybe you guys can comment on my nuts idea, no pun intended . Even though this design may be dead, I would still like to know what is right and what is wrong.

 

Terry, that's a cool idea for some toe on the rear control arms, I like it.

 

DAW, I just can't picture your idea. I know what you mean, but I can't picture it. Would you or someone else be able to maybe draw a picture for me and possibly others that are more visual learners? I know it's asking a lot, but it would help out. Or, anyone have any photos of something similar?

 

This post is really fun, I'm learning a lot, thanks guys!

 

!M!

[ZROSSA]

Mat, Have a look for opel or holden vectra or astra. Its pretty easy though, just weld on some brackets to the bottom of the strut for the link from the roll bar to pick up on.

 

Douglas