Mikelly Posted April 26, 2001 Share Posted April 26, 2001 OK guys, I need help... I need honest feedback from the racer types out there. I bought some T6061 aluminum stock and started playing around with it for making mockups of my control arms. Stuff is strong as hell, and Coleman can cut to my specifications any length of the tubing in either aluminum or mild steel. The new contorl arm design has a threaded rod coming out of the contorl arm box just past the Sway bar end link point. That rod will screw into a 4 inch long threaded tube, of course threaded right on the CA end and left on the inboard end (Towards the Rodend). It is my believe, based on the fact that I drove on the old Zdr control arms for 7 years with aluminum rod ends in them, that using the T6061 may be all I need in this design. What do you guys think? There is no performance gain, or (About $.62 price difference) price break going aluminum or steel. Obviously the aluminum comes anodized and would look sharp. I'm just trying to get your honest feed back and thoughts.. The new design does away completely with the female heim joint and turnbuckle. This newer design uses high stregth threaded steel (Grade 8 or higher), and based on the lack of load on the part, I think this new unit will be bomb proof even with aluminum. Feedback please... Mike Quote Link to comment Share on other sites More sharing options...
Dan Baldwin Posted April 26, 2001 Share Posted April 26, 2001 I'd like to see the design. Load from the sway bar is not insignificant, and it sounds like you may be relying solely on a threaded rod for bending strength near the point that probably sees a pretty big bending moment during hard cornering. I'm assuming the 6061 is T6 heat treated. No welds on the part, I assume? If so, the Al is T0 around the weld (much weaker). Probably already considered by you, but worth mentioning: 6061-T6 has a tensile strength of 42 ksi, vs. ~55 ksi for mild steel Al doesn't have a definite fatigue limit like steel does, and fatigue cracks can develop over time even though applied stress is low. Design should minimize stress concentrations and not give cracks any excuses for forming. Dan Baldwin M.S., B.S. Aerospace Engineering Quote Link to comment Share on other sites More sharing options...
Guest scca Posted April 26, 2001 Share Posted April 26, 2001 Mike. i had TC rods like you are talking about making on the 510. there is a LOT of stress as Dan says on the area where it changes from a rod to a threaded portion. i have actually bent mine before and those were out of steel. - alum i would think would be OK but best bet would be hex stock in steel and powder coat it. if you choose alum make sure the transition is 2-3" of thread min. inside the alum. so that there is enough length. Quote Link to comment Share on other sites More sharing options...
Mikelly Posted April 26, 2001 Author Share Posted April 26, 2001 Excellent points. I was hoping both of you guys would weigh in! Just trying to play around with all my matterial options... Mike, I think the TC Rod sees a lot more stress than people think, based on the TC Boxes I have seen seperated over the years. Keep the points coming guys... I have added more thread to the TC rod, based on feedback from Port City Racing on parts they have scene fail in similar situations. I also Agree that adding the steel vs. aluminum will probably be cheap insurance in the long run. Never sceen a TC rod fail, but I've seen some bent control arms... John, the control arm (I'll have pics up on my site tonight) will have a tapped steel block with a threaded steel unit coming out of it. Thread length will be two inches internal, and two inches exposed. The adjuster rube will be bored and tapped 3/4 16 right on one end, 3/4 16 left the other. Thread will be 1.5 inches each side depth. This allows a minimum 3/4 inch of thread (Heim joint or threaded rod) to remain within each end at all times, more for less negative camber. Mike [ April 26, 2001: Message edited by: Mikelly ] [ April 26, 2001: Message edited by: Mikelly ] Quote Link to comment Share on other sites More sharing options...
pparaska Posted April 26, 2001 Share Posted April 26, 2001 Mike (Kelly), I agree totally with Dan on the steel vs AL thing. That's sprung weight anyway, and AL and fatigue issues always gives me the willies (no fatigue limit). I'd say go with the steel one and powder coat or POR-15 the steel body black. As for the bending loads on the threaded rod, that is a concern. I'd like to see an analysis of the bending and shear loads on that rod. Since it starts near the sway bar mount point an the arm, the bending moment will be high at the root of the threaded rod where it comes out of the tapped welded in block. I really like Mike (scca)'s idea of a piece of hex threaded where the threads only need to be - this gets the threads away from the root of the clamped end near the sway bar mount - a good thing. Shear loads will be present, and I'd like to see an analysis of that also. Dan, do you have any ballpark for the vertical load that a hefty sway bar imparts to the CA, for turning a Z at 1g? I'd imagine the dynamic load would be of little consquence in this case, unless you hit a big sharp bump during a turn. Pete Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted April 26, 2001 Share Posted April 26, 2001 Wow Dan, I guess your one of the few people who doesn't have to say, "I'm no rocket scientist but...". Thats pretty cool, I agree with the use of aluminum, you guys have it handled from a science perspective, I've seen aluminum failure caused by stress cracks and such. I know thats one of the reasons they say Aluminum rods are not suggested for street cars is they're fatigue after a while. Ok on a race engine you're going to be into and probably replace them from time to time. Regards, Lone Quote Link to comment Share on other sites More sharing options...
Mikelly Posted April 26, 2001 Author Share Posted April 26, 2001 Well I'll explain how I plan to combat this when I'm in Cali, but I already know that, based on conversations I had today with our local Race Fabricator, I'll be doing chromo tubing for the strut tube and the control arm tubing, and I'll be using Chromo threaded rod stock for the control arm. This will impact cost, but I was planning to lower the price by Approx. $50-75, but I suspect (Amd I need to get exact prices..) that the $400 price will not go up. Stay tuned.... Mike Quote Link to comment Share on other sites More sharing options...
Dan Baldwin Posted May 1, 2001 Share Posted May 1, 2001 As far as sway bar load goes, one way to measure it would be to jack up one side of the car and measure the spring's compressed length on the lifted side. Then lift the front of the car and measure the spring's free length. The difference multiplied by the spring rate gives you the compression introduced by the sway bar when one side of the car is lifted by a jack. Double this to get the compression caused by a car cornering fast enough to lift the inside wheels (this should be conservative for steady cornering, maybe about right accounting for bumps, undulations, etc.?). Then you'd have to work the geometry to get the sway bar load, which will be greater since it has less leverage on the control arm than the spring does. Quote Link to comment Share on other sites More sharing options...
clint78z Posted May 2, 2001 Share Posted May 2, 2001 A good suggestion is to find someone with Mechanical Desktop or better modeling software. Get them to do a 3D design, this will show you things that you would have never thought about. It allows optimization quickly, and you can cut material costs. I imagine his services could be traded for a pair of control arms. I would volunteer to do this, however our company is limited to 2d modeling FEA structural analysis. If you want I could draw you parts in 3D autocad solids, I just can't do the analysis in 3D. Remember shock loading can stress the part 3-8times as much as normal loading. Quote Link to comment Share on other sites More sharing options...
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