Ok . I have done a lot of searching on here and am thinking of making my own. I have found answers to a lot of questions ,but not all. I am planning on building them with 2x3 I beam ,but am not sure on the thickness of the steel. 1/8", 1/4"? not sure. I am not sure if there is an advantage to the mono ball set up I see on the nascar arms (I am not sure if its better). I just want a nice ride on my 53 belair. Cruising and lighting the tires up on occasion. Thanks..
GM used .120 wall C channels, back to back. I just added pics on another guys thread http://www.jalopyjournal.com/forum/showthread.php?p=7471406#post7471406
I think that most of the guys who run the swivel ball setup are probably more inclined to want to raise or lower individual corners on the car ala lowrider hydraulic setups. A lot more monkey motion if you will than a bushing setup will allow for.
thanks for the input. f&j I know gm used the channel like you stated back to back. maybe 2 pieces of c channel would save some time slicing
Use a bushing over a mono-ball or Heim joint on the street for durability and longevity. Open metal joint plus road grime = sloppy, noisy joints over time.
here's my old thread http://www.jalopyjournal.com/forum/showthread.php?t=144403&highlight=nascar+suspension
If you were going to mount the fronts together like a true wishbone with a ball, it does not matter if the the arms material is "able" to twist like the GM arms were designed.. If it is like a wishbone, then there is no twisting apllied to the arms as one wheel goes up/down.
i like the way Smart car has its rear suspension, one piece of tubeing bent into an A with a nice fat rubber bushing, it has struts but could be coils or a spring.
What about a torque arm along with truck arm? Im running a 47 Olds truck arm in my 33 p/u. The arms are a tapered hat channel. I don't want to box them, but I'm not sure their going to be up for the punishment I have in store for this little truck It's been suggested I add a torque arm to help with launch. Plan to race this truck, but want to keep it streetable.....any thoughts?
The I beam will work fine. I've done a lot of cars this way. The I beam allows twist. I think the web was more like 3/16 thick. I've used everything from stock GM bushings to eurethane bushings. The eurethane bushings have been from everything like springs to crossmember bushings. Go to a 4x4 shop and see what they have. Clark
I-beam may be too stiff. Square or rectangular tubing is right-out. The only way for this system to work properly is for the arms to be able to flex, period. If not, something will break, eventually. It is a physics problem, and you don't get to violate those laws. As I said on another suspension thread: Déjà vu. We keep having this argument. There are professional suspension engineers on this board. Please listen to them.
Those can't flex. All of the deflection would have to come from the bushing. This basically turns the rear axle into an anti-sway bar. ***SEE MY CORRECTION BELOW***
So far as I'm aware his kits use a standard-issue NASCAR truckarm. I once voiced the opinion that the arms didn't flex, but a friend who's a NASCAR crew chief informed me I was wrong. Monoball means more noise and drivetrain resonances passed into the car's structure, probably more maintenance too. I suppose if one is trying to do something creative in terms of packaging it might make sense to fab one's own, but it seems to me for most purposes off-the-shelf Cup arms are probably the way to go: http://www.circletracksupply.com/Truck-Trailing-Arms-for-Ford-9-Rear-Ends..html http://www.stockcarproducts.com/trkarm.htm
I have a set of the Stock Car Products arms, rubber bushings and axle pads. I am very pleased with the materials and workmanship of the parts. Very first rate fabrication, in my opinion. They are not "cheap", but quality usually isn't and is worth the price in the long run. Ray Edit: I neglected to say, the SCP arms duplicate the factory GM truck arms in that they are two "C" channels, back to back, forming an I or H shape and will, as GM intended, twist along their length. They only differ in minor detail at the ends to accommodate fabrication.
Ahh, I stand corrected. I was viewing on a small screen. Those arms appeared to be boxed. Now that I am on the big screen I see that they are NOT. They are close to the OEM GM design, and look pretty damn good. Carry on. My mistake.
wow, this topic is still taking a beating, best choice for homemade truck arms, 2x3x3/16 rectangle tube, split down the middle and placed back to back to form an I beam, how the stock car ones are made, and that nascar requires them to be made like that, not boxed.....full tube bars of any material will cause the front bushings/mounts to wear/break, using I beam allows flex in th beam and will reduce that, even if you arent racing or any of that stuff, going around a corner will cause these things to happen.....but, hey, what the helll do i know.....
i personally don't believe that you must run i-beam for this type of suspension anymore. i built my "truck arms" out of 1.5"x2.5"x.120" rectangular tubing with a 1" uniball in front. i of course was worried that they would bind and break and do bad things but i built it this way anyways. well i can tell you that i have about as much bind free articulation as a rock crawler. absolutely no bind and more articulation than i'll ever need. i think the key was keeping the front mounting points as close together as possible and of course using a big fat uniball that allows the arm to roll over instead of bind like a regular bushing would do. front view: rear view:
Two comments; Newsometravis......making the truck arms in the manner you suggest sounds fine, but 3/16" is thicker than Stock Car Products uses for actual racing components ........1/8" ( .120 ?) is what they use.... Beef Stew......I think you are 'getting away' with boxed arms because they are rectangular tube, thinner wall section, with the narrower dimension in the vertical plane and they ARE flexing ! If you had used heavier wall and/or square tube of 2 1/2" dimension I would think the articulation would have been more "stressful". Just an opinion....but I believe the GM engineers knew what they were doing when they designed the truck arm setup and nothing is improved when us amateurs substitute different cross section materials, or geometry, out of convenience or ignorance. Ray
The use of truck style trialing arms is preettty well tried and true, these have been gm designed and nascar tested for a number of years so the design flaws have been very well diagnosed. If you want to use truck style control arms copying a proven design is the best approach. The truck arm design is a back to back c channel. This allows the material to have a sufficient amount of strength as well as structural flex during operation to eliminate any fatigue stress that would accumulate at the connection points. The back to back c design spreads the torsional stress out over a longer twist span to limit fatigue. The more rigid that the control arms are made under the idea that heavier is better is not always the best route. One of the factors not discussed is that of unsprung weight, which should be kept to a minimum, and those control arms made from over kill materials do not accomplish that. Rectangular tube designs also have more torsional resistance so they should be avoided. Its not that they don't work , its that they place addition strain, which may create a fatigue factor on the linkage points or bushing ends. I beam designs concentrate the torsional twist in a smaller area and are prone to cracking in that area due to metal fatigue due to poor elastic properties of the material . If you are using a truck arm style locating linkage the flexible ends should be done in urethane or rubber bushing. The major reason for this is lubrication during operation. Monoballs or other steel bearing pivots need a source lubrication (greasing) and this is not always addressed on a street driven car on a regular basis. I realize that may people like to fab their own parts but as a hint, may parts like this can be purchased at the used racecar parts stores. I just purchased a new set of truck arms at the used parts store for less than $150.00.
Ok so how wide is an OE arm. You guys have me thinking of splitting a piece of tubing, but it would need to be the right width tube to start with. I'm thinking 2x3 might work if split down the middle.
No shit. Why do you think I DIDN'T use a heavier wall and/or square tubing? Oh and let me guess... if I had used a big fat wide bushing as the forward mount on my links it would have been more "stressful"? No shit. Maybe that's why there's a huge 1" uniball up there instead. Do you always allude to the thought that if someones alternative design actually works the way they designed it to that they must be "getting away" with something? As if I DIDN'T specifically design for these attributes? I guess all the time I spent consulting with people who design and build suspensions for a living is replaceable by your opinion that I just happened to blindly stumble upon this "substitute" design out of sheer convenience or ignorance.
Yeah, I think you summed that up pretty well ! Did you have breakfast this morning? Seems like your blood sugar may be a little low. Ray
Dick brings up a good point. Used NASCAR parts are available from Ebay, Muscle Motorsports (website doesn't list them but they have in the past), or the teams themselves. Richard Childress Racing just had an auction a couple months ago with PALLETS of truck arms for sale. Wish I had the cash to buy and resale them.
I knew this was a subject that has been beaten to death. My concern was the material thickness and I beam size. Also questioned the monoball or rubber bushings. I am now thinking it might be better to buy a used nascar set(I am pretty certain it will be a correct design) as they can be found pretty reasonable and just get them with bushings instead of monoballs. There are a lot of opinions on the make up of the arms on this set up and I am definitely no suspension expert. I plan to have my family in the car to go on cruises and hang outs and the last thing I want is a problem. Thanks for the advice everyone. Much appreciated
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