Mikelly Posted January 30, 2003 Share Posted January 30, 2003 Spoke with John Williams last night and it seems that the fellow he left the arm with decided to possiobly copy it and sell his own... John is getting the unit back and is gonna try and get another guy to take a look at it, but I told him if it takes too long that I'll just discontinue the line of rear arms all together. I'm now concerned about getting back my unit to complete my personal set... This brings up my frustrations over the lack of HONEST vendors support of our cars. I've dealt with a number of people over the years and it seems that most of my dealings with vendors and those interested in making stuff for Zs has been less than ideal. Actually, other than dealing with Ross, Mike G., and Scottie (And of course Jamie T. who was making the rear arms for me), I've had some pretty crappy luck. ...OH and ANYONE know where I can find Les Heath... Guy still has my Gnose... Any tips or contact info would be appreciated. Mike Quote Link to comment Share on other sites More sharing options...
blueovalz Posted January 30, 2003 Share Posted January 30, 2003 Sorry to hear about these arms. Honesty and reputation seem to have taken a back seat to the dollar any more. Quote Link to comment Share on other sites More sharing options...
Dan Baldwin Posted January 30, 2003 Share Posted January 30, 2003 Hate to have to say it, but the triangulation on those arms is wrong. It puts the long tube in bending, a BIG no-no, and not necessary. Also, I don't know about the threaded rods(?) in bending, particularly if a rear sway bar is used. I'm not saying the design is inadequate, I haven't done any analysis on it. But it looks bad. I've seen more than one aftermarket suspension component failure at the track (mostly Mustangs), and it AIN'T pretty. Not meant as an attack or anything, just an observation. Quote Link to comment Share on other sites More sharing options...
jeromio Posted January 30, 2003 Share Posted January 30, 2003 I'm not an engineer, nor do I play one on TV, so I'm not sure whatcha mean by that - "the long tube in bending". And by lng tube, do you mean the longest tube, the one that gets mounted in the bushings? From a layman's eyes, it looks plenty sturdy enough. Are you saying that there should be another tube in there someplace, or that one of the tubes should be removed (or both)? Here's another example: (Simon deGroot's car) Better, worse, the same? Quote Link to comment Share on other sites More sharing options...
Dan Baldwin Posted January 30, 2003 Share Posted January 30, 2003 Yeah, that's what I meant by the "long tube", the one that is axial with the inner bushings. The one you show *looks* (note emphasis, as in I haven't done any real analysis on either) better. For a strictly tubular one, I'd rather see something like this (here's hoping my ASCII art isn't too too horrible) for the inner part. This would be MUCH stiffer and stronger. .____| Rear Inner Pivot | / | .| / | | | | | | Forward Inner Pivot Quote Link to comment Share on other sites More sharing options...
Mikelly Posted January 30, 2003 Author Share Posted January 30, 2003 Not taking offense... I've got a number of folks here that are using them with GREAT success and ZERO failures... The threaded turnbuckle is not gonna fail. I had these units put into a hydraulic device that is designed to make parts like this fail, using four hydraulic pistons that push in varrying angles with varrying forces... at 78,000 pounds presure the only problem I had was one split tube. It was the longest tube, but then again, it was 78,000#. These units will NOT fail under normal conditions. This was with .130 mild steel tubing. Mike Quote Link to comment Share on other sites More sharing options...
Dan Baldwin Posted January 30, 2003 Share Posted January 30, 2003 Glad to hear it's been tested and that there have been no failures. Fatigue failures can take a while, though. I wish my ASCII art had come through. I still would much rather see it without the "node" at the midpoint of the long tube. Picture the rearmost diagonal tube going straight forward from its aft end, meeting the aft end of the forwardmost diagonal instead of angling over to the long tube. And then picture the inboard end of the middle transverse tube angling back to the aft end of the longtube (instead of joining it at its midpoint). That would be a more efficient structure, and wouldn't be much if any more difficult to produce, I think. Somebody makes them like this (don't remember who), I put a picture of one on my gallery at 240Z.org here: http://www.classiczcars.com/photopost/showphoto.php?photo=3164 For adjustability, do you have opposite-threaded rods coming out of the inner and outer welded pieces, with a turnbuckle connecting them? I just wonder about bending loads from a rear bar working those connections (same issue with the front arms). I wonder if there's an easy way to mount swaybar links to the bottom of the strut housing, or coaxially with the CA outer pivot? That would eliminate the out-of-plane bending load, and the turnbuckle would be loaded axially only (ideal). Note: These are my IMPRESSIONS based on what I see (and my experience in structural design and analysis), not the result of any analysis. Quote Link to comment Share on other sites More sharing options...
Mikelly Posted January 31, 2003 Author Share Posted January 31, 2003 Dan, that arm is very similar to the Arizona Zcar arm. I can't speak about their product other than the differences in theirs and mine. The goal my customers specify is that it must be ON-CAR adjustable, and the AZ Car unit isn't. I have front control arms based on a male heim joint design like the AZ Car units and they were time consuming to adjust. Mine aren't. Also, I've sold 34 sets of fronts and over 20 rears with ZERO returns due to failure in workmanship. Mike Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted January 31, 2003 Share Posted January 31, 2003 Dan.. I really like your design could you type up a set and email them or can I just down load em now. How does the ink attach to the strut pin ? Quote Link to comment Share on other sites More sharing options...
Guest GaryZ Posted January 31, 2003 Share Posted January 31, 2003 Guys, this thread has changed from the original topic. Maybe it could be moved as I think others wouuld find it very interesting. Over the years, as a serious racer, I have asked the opinions of a number of local, but well respected chasis builders about the 'tube frame' concept AZ Z car design--with less than a positive recommendation. It's the kind of design and stuff one needs to be very, very careful about. What I like about Mike's design is that is it is variant of the OEM design. Maybe I am just overly conservative, but at racing speeds I like to see suspension components that have either: a) been around for a while or have been built by a well known shop. Quote Link to comment Share on other sites More sharing options...
Mikelly Posted January 31, 2003 Author Share Posted January 31, 2003 Gary, I appreciate the compliment. However, Dave at Arizona Zcar does build a nice piece. His tubing is cromoly which is stronger and lighter than mine. My ultimate goal was to have it made of cromoly and one upgrade I'm gonna make to my shop after I move in is to shop for a tig welder and then learn properly how to use it, which will require me to go BACK to school since I haven't used one in 18 years. I think my design (Jamie's design really) is strong, certainly functional, and on-car adjustable, which is important to my customers. If I can alter them slightly to add strength and to give more swaybar pick up point options, then I'd be happier. John and I actually talked about scrapping the outboard section the turnbuckle threads into (Where the spindle pin mounts) and use a female Heim joint there at that point for better geometry, but I'm a bit concerned about that since it hasn't been tested... This would allow me to run the sway bar mount differently though... Hopefully I can get some super smart guy like John Coffee involved in this piece. At this point I'd be willing to bow out of the production of this part as long as someone I trust could continue on with the intended goals kept: Reliability, Affordability and ON-CAR adjustability! Mike Quote Link to comment Share on other sites More sharing options...
Dan Baldwin Posted January 31, 2003 Share Posted January 31, 2003 Originally posted by Mikelly:at 78,000 pounds presure the only problem I had was one split tube. It was the longest tube, but then again, it was 78,000#. Just read this again. Was this test done at Boeing or something?! Seriously, 78,000 lb is, well, difficult to believe. How was it loaded? Potential problems with the Az Zcar rear arm and the rear arm I linked to a couple of posts up have to do with bending load in the outer heim joints, where they screw into the arms. The distance from those spherical joints to the arms appears small on those arms, but calculations show the bending moment and stress in the threaded section to be not insignificant. Mike's arms do avoid this somewhat, as the adjustable turnbuckle parts carry appear to primarily carry axial loads and shear, with bending pretty minimal (at least if there's not a sway bar involved). BUT, the triangulation is still FUNDAMENTALLY wrong. It should look more like the AZ Zcar and the arm I linked to. That would make me feel a lot better about this piece. The front arm, with big sway bar bending loads being taken by a threaded rod, I dunno. I guess if the rod is big enough, but has any analysis been done to determine how big "big enough" is? Brake brackets, suspension parts and the like should be subjected to analysis by qualified structural engineers, and an engineered structural test program. If only one of the two is done, factors of safety should go way up. There's a lot of stuff out there that looks right but is bad wrong, that has never been subjected to any kind of structural analysis or test. None of it goes on my car. So, anybody want to give me a consulting job? Quote Link to comment Share on other sites More sharing options...
katman Posted January 31, 2003 Share Posted January 31, 2003 Danno, being the typical paranoid structures engineer, has some valid points. My problem with all these aftermarket adjustable control arms (AZ car, ZFRacing, and the one Dan links a picture to, for which I actually did a quickie analysis for the guy who made it- very nice part) is they put the threaded shaft of the heim joints in tension/compression and bending. Maybe not too big a deal, but nothing prevents a guy from extending the threads out a pretty good bit to where the stress in the root of the threads is definitely non trivial. Not really a static problem, more of a fatigue problem. On a race car we inspect that sort of stuff every time the car comes off the track, and if it does fail we got a full cage around us. I don't expect "street" folks to be that diligent with inspections, or even know what to look for necessarily. Just some other things to remember- yeah the braking, accel, and cornering loads are higher for a race car but the number of cycles is way less, and the maintenance tends to be way more. The drag loads on this piece are reacted entirely by the front inner mount, so the forward heim joint gets near all the fore/aft load and hence the shear and bending. Threads are a nice little notch for cracks to start in, even rolled threads. The stresses in the minor diameter of the threaded heim is proportional to the diameter to the 4th power, so you can see it is very sensitive to what size thread you use, and the quality of the part. Analytically they may all be just fine, but I can see why Dan is "stressed". Quote Link to comment Share on other sites More sharing options...
Dan Baldwin Posted January 31, 2003 Share Posted January 31, 2003 Originally posted by Mikelly:This stress tester (He calls it is demolisher) actually has four posts with Hydraulic pistons that have steel inserts that can be swapped for differing sizes... We put it in this vise like contraption and load the part in opposing angles (We did 8 in all) and test welds and such. We didn't max the system out as he has done well over 100,000 pounds presure on stuff designed for special customers. Fun w/ hydraulics! That certainly does something to instill confidence. Would be nice to see pics of the tests if you have them. Were you able to hold the inner pivots and apply fore/aft thrust loads at the outer pivots? BTW, it looks like the threads on your rear control arms are only subjected to bending if there's a sway bar involved. Thanks for chiming in, katman. It looks like the arm I linked to does share the shear and bending between the two outboard heim joints instead of all of it going to the forward one. Looks like the longitudinal distance between them is fixed, right? Honestly, I feel a lot better about both the previously linked-to arms (who makes those?) and Mike's after this discussion. Eventually, I'd like to get some rear adjustability beyond what I've got with the Al/delrin eccentric bushings. Rear end is somewhat out of whack after last year's "incident" at Turn 6 at Watkins Glen. The eccentric bushings got me somewhat close, but both rears are about 1/2" offset to one side with the toe and camber set where I want them. Quote Link to comment Share on other sites More sharing options...
Mikelly Posted February 1, 2003 Author Share Posted February 1, 2003 Dan, it was at a machine shop in Stafford Virginia. The guy does specialty tooling for air craft parts and special tooling for people at Quantico, Va., FBI, DEA, Marines... He also used to be an engineer for NASA. I almost Married the guys daughter once and we hit it off. Anyway, he is somewhat the brains behind my engineering designs... I fly stuff by him and a few others. This stress tester (He calls it is demolisher) actually has four posts with Hydraulic pistons that have steel inserts that can be swapped for differing sizes... We put it in this vise like contraption and load the part in opposing angles (We did 8 in all) and test welds and such. We didn't max the system out as he has done well over 100,000 pounds presure on stuff designed for special customers. I'll try to get some pics of his contraption the next time I'm at his shop. I don't make this stuff up, and I certainly would not make a part and sell it if I didn't think it would survive on a ZCAR. Comments about the threads... I have recommended that adjustment on each end of the turnbuckles not be extended to show more than 3/4 inch. The threaded turnbuckles are 2.25 inches per side threaded into each rod. The rods are .130 thick and pretty strong. I had the square tube design tested without any failures. I had the front design tested without failure. I did have failure on the TC rod because we used an aluminum rod at first... Bad move. I never sold a part with aluminum, so that wasn't an issue, just added some excitement to our first MSA outing! The tubular arm split on a piece of tubing that was suspect from the beginning and I've not been given any tubing from SCP like it since. However, I'm open for options to look at. I'm also open for someone taking over the making of these parts if they can do it better/ cheaper/ faster! Mike Quote Link to comment Share on other sites More sharing options...
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