JMortensen Posted December 8, 2003 Share Posted December 8, 2003 I've already asked this question of 2 people, and gotten answers. Mike Kelly was especially helpful. Thanks, guys. I'm asking for more because I'd like to get as many opinions as possible before I make a big mistake. I would like to try and make adjustable rear control arms. I have an extra set to work on. Here's the idea: cut the outer ends off of the stock control arms. Weld in "threaded tube ends" from Coleman, part #15587. These ends are about 1.5" long. I have yet to see if they will actually fit into the end of the control arm, but I don't want to buy any parts until I'm satisfied that I'm not going to kill myself. If I can get 1.5" of threaded tube, then I'm not really worried about the control arm side of the rod end. 1.5" should be plenty of meat. What I don't want is the rod ends to be extended more than a few theads out of the threaded tube ends, as that is where the bending load is placed on the rod end's threaded shaft, which takes a pounding. My theory is that if the AZC arms work, then using the stock control arm should too, as long as there isn't large amount of thread sticking out of the control arm. I suppose ultimately it would have to be mocked up to see if the track would be narrowed significantly by cutting the stock ends off the control arm. If not, then I could run the rod ends pretty well bottomed out into the control arm. I've got camber plates, so if I lose a little neg camber I can just adjust it right back from the top. My front adjustable control arms are basically done this way. A machinist made them for me, and he got a thick walled DOM tube, cut the control arm in half, welded the tube into the outer part of the control arm, and welded the threaded tube end into the outer part of the tube. I've got no qualms about the front, but the rear seems to be more iffy from the reactions I've gotten when telling people about this idea. Any thoughts/opinions??? I would like to try this, and I don't want to purchase other peoples' control arms, all of which seem to be controversial from an engineering standpoint and expensive. The stock control arms are obviously up to the loads placed on them, and I'd like to run poly and get rid of the G Machine bushings and still retain some adjustability. TIA, Jon Quote Link to comment Share on other sites More sharing options...
JMortensen Posted December 9, 2003 Author Share Posted December 9, 2003 50 views. No comments??? Quote Link to comment Share on other sites More sharing options...
blueovalz Posted December 9, 2003 Share Posted December 9, 2003 If'in you're wanting some comments, I'll throw a bone out. When I did my front control arms, I used two methods, of which I liked the latter of the two. These methods I feel could be used on the rear as well. One method was the threaded tube as you've mentioned. The other was a threaded stud (actually, a 3/4" bolt with the head cut off. I preferred the stud because They were very strong, long enough to thoroughly weld them to the arm, and any welding done on them would be away from the threads where as the threaded tube, if not careful, would end up having some of the threads ruined if the weld penetration went deep (I prefer good penetration in cases such as these). I've considered doing the same thing as you mentioned, and in the case of the rear arms, their larger cross-section of tubing (after the ends have been cut off) probably warrents the use of a threaded tube instead of the stud. I would like to be corrected here if I'm wrong, but the only thing that would cause the rod end's threaded shaft to "take a pounding" would be a stiff sway bar? I say this because all suspension side loading should be a tension/compression stress at the rod ends, but I am unsure about the torque loading upon acceleration. Does the movement of the wheel pulling the car forward cause the front rod end to compress while placing tension on the rear rod end, or does this action or force cause shear loads to be developed on the rod ends instead. In other words, does the wheel want to rotate about a point centered in between both of the rod ends, or does the wheel wish to simply roll forward placing shear stresses on the rod end shafts?. If it is the former only, then the sway bar will be the only factor in placing lateral loads on the threaded shaft of the rod end. Quote Link to comment Share on other sites More sharing options...
Dp351zcar Posted December 9, 2003 Share Posted December 9, 2003 Jon I have thought a lot about building rear control arms but have not tried it yet. If you want to meet me and maybe have a pizza and something to drink I think I can help you a little (but mabe I think too much about what little I know). Don Quote Link to comment Share on other sites More sharing options...
JMortensen Posted December 9, 2003 Author Share Posted December 9, 2003 Terry, I honestly don't know the answer to that question. I know that rear drive cars toe out under acceleration, and I figured the stress on the rod ends would result from acceleration more than braking, which takes weight off the rear. Also going over bumps and turning would stress the threaded part of the rod ends (they're already loaded by the g force of the turn, then get sudden impacts from the road surface). I would plan to run about 3/16" total toe in, like I am with the G Machine bushings. That seems to be my happy place with regards to rear toe. Makes it stable under braking. Don't know if that changes anything drastically with regards to the rod ends. Unfortunately for me I'm only smart enough to know that I don't know on this one. Thanks for getting things rolling though! Jon Quote Link to comment Share on other sites More sharing options...
vashonz Posted December 9, 2003 Share Posted December 9, 2003 What about using turn buckles? Cut control arm, weld threaded rod into exisiting control arm, then install turnbuckle to connect them. Use lock nuts to keep from adajusting under stress. if you went further you could weld nuts in to support the all thread inside the control arm. I'm sure the turn buckles would be able to handle the compression/tension loads. I'm pretty sure it would handle the lateral loads too. If you want/need help with this I know people with tig welders and plasma cutters in the seattle area. I also have a couple extra sets of control arms to 'experiment' on. If you're new to the seattle area you might check out pacific industrial supply (near the stadiums, really cheap stuff), or boeing surplus (down in kent), also westmarine would be able to provide the specs for the turnbuckes. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted December 9, 2003 Author Share Posted December 9, 2003 I'll be interested to hear what people think of that Vashonz. Thanks for the supplier hints, too. Jon Quote Link to comment Share on other sites More sharing options...
blueovalz Posted December 9, 2003 Share Posted December 9, 2003 While it's on my mind, I would consider, if you can swing it, spreading the distance between the rod ends verses closing them in on the strut base. The closer these to rod ends are, the more leverage any torque or twist applied to these rod ends. My thoughts (thinking aloud here) are to space these rod ends away from each other to the maximum allowable. The OEM bushings are approximately 1.5" long. This would then mean you could use a 3/4" spacer between the strut base, and the rod ends. An unresolved issue was the spindle pin. Mine measured .780" when I was investigating this issue. The pin could be turned down on a lathe to .750" for the use of 3/4" rod ends, or another option of tapping the ID of the spindle pin receiver, and thus screwing some grade 8 bolts into the base as a replacement for the spindle pin, but once this was done, you would have to do it again if you were to ever replace the strut tube. They would need to be at least 7/8" or bigger to be able to tap out the threads to full depth. Quote Link to comment Share on other sites More sharing options...
Dp351zcar Posted December 9, 2003 Share Posted December 9, 2003 Jon I have tried to send to send you an email at attbi and comcast but both got returned to me? Don Quote Link to comment Share on other sites More sharing options...
260DET Posted December 9, 2003 Share Posted December 9, 2003 It is not that hard to make up replacement arms using the original inner threaded tube part and rod ends with the eyes fitted over the original outer spindle pin. I made a jig using some heavy particle board with big nails belted into it at the crucial points. Then it's just a matter of cutting and fitting the various pieces of tube in place ready to be tacked together prior to final welding. The threaded part of the rod ends go through holes in a piece of angle iron which forms the outer part of the arm, parallel to the spindle pin, with nuts on both sides of the angle iron. The outer nuts are half nuts, the inner nuts have a shoulder machined on them which fits in the hole so that the thread is protected. Easy peasy to adjust, using OE inner bushes it's quiet. One of my more successful mini projects. So Jon, you are obviously thinking your idea through and taking your time. But I must say a set of pretty fabricated arms will look a lot better than modified originals, which are none too inspiring in the first place. It is what you really want to do, isn't it. 8) Quote Link to comment Share on other sites More sharing options...
JMortensen Posted December 9, 2003 Author Share Posted December 9, 2003 OK, I did just have a glass of wine, but I didn't follow that at all 260DET. You got a picture or something??? Terry, I'm sure using a 3/4" rod end would eliminate the possibility of weak rod ends, but I don't think it would be easy to sleeve a 7/8 hole down to 3/4". That's a really thin sleeve, but it would be great if it could be done. I thought the holes were smaller, like 5/8". Guess I was wrong on that one... I have to wonder if the 3/4" rod ends would interfere with the brakes too. That's a pretty big end to have out there. Good idea, I'll have to look into it. Jon Quote Link to comment Share on other sites More sharing options...
260DET Posted December 9, 2003 Share Posted December 9, 2003 Have another glass of wine, or two, instead of pictures. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted December 9, 2003 Author Share Posted December 9, 2003 It would be pretty easy to spread the rod ends away from the strut. Just use spacers like you find in bump steer spacer kits from Coleman. Jon Quote Link to comment Share on other sites More sharing options...
katman Posted December 10, 2003 Share Posted December 10, 2003 I would plan to run about 3/16" total toe in' date=' like I am with the G Machine bushings. That seems to be my happy place with regards to rear toe. Makes it stable under braking. Jon[/quote'] Nothin' like dragging the tires around all the time. 3/16 is a LOT. On the ITS cars we get away with zero to 1/32 total toe in. Perhaps a change in some other part of the setup would allow you to reduce that and still be "stable under braking"...... Of course any rubber you still got back there changes everything. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted December 10, 2003 Author Share Posted December 10, 2003 I've tried a bunch of different settings from 0 toe to 3/8" total toe in (yes really), but I turn the fastest times with that setting. I'm sure that there are more suspension tweaks to do, and this is just one more step in getting them all done. Thanks for the input. Jon Quote Link to comment Share on other sites More sharing options...
blueovalz Posted December 10, 2003 Share Posted December 10, 2003 Jon, I misled you on that pin dimension. The spindle pins are about .630" and not the larger dimension I stated earlier. It would appear a 3/4" bolt would work in threading the spindle pin receiver. There is gobs of room in this area to install rod ends far away from any brake components. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted December 10, 2003 Author Share Posted December 10, 2003 Well thanks again Terry. I'm going to have to pull my spare control arms and rear struts out of the attic and get going on this sometime this winter. It definitely seems doable, from all accounts. I do like the idea of the 3/4" rod ends too. That would pretty much alleviate any of the concerns that I've heard with respect to the strength of the threaded portion of the end. Jon Quote Link to comment Share on other sites More sharing options...
JMortensen Posted December 10, 2003 Author Share Posted December 10, 2003 Another thought occurs to me. Run rod end reducers on 3/4" rod ends and use a 5/8" through bolt. That would be easier. Wouldn't be able to bolt to the strut housing, but it would make swapping a strut housing less difficult if I were to bend one. Jon Quote Link to comment Share on other sites More sharing options...
blueovalz Posted December 10, 2003 Share Posted December 10, 2003 Another thought here as well. Adjustability: Using any rod end in this manner, the smallest granularity acheived will be 1/2 the pitch of the threaded rod end (1/2 turn of the rod end in or out) and then this must be used in relation to the distance between the rod ends, and the tire size. For example, a reasonable distance, with spacers, between the rod ends will be about 7". If one were to use a NF 3/4" thread for adjustment (16 TPI), then the finest increment of adjustment is 1/2 turn, which is 1/32". A 32nd of an inch, separated by 7" will give the finest increment of adjustment at the tire (assuming a 24" diameter tire), as far as toe-in or out is concerned, of between 3/32" and 1/4". I feel this is much too coarse of a "minimum" amount of change for any single "half turn" adjustment. This then brings in perhaps the use of a counter threaded rod or tube using left/right hand threads, at least on one rod end only, to give the infinite adjustment needed for proper set-up (unless toe adjustment is not critical for what you are striving for) Quote Link to comment Share on other sites More sharing options...
JMortensen Posted December 11, 2003 Author Share Posted December 11, 2003 Welcome to the World of High Performance. Well, infinite adjustability would be nice. I'm trying not to reinvent the wheel here, but as vashonz stated earlier a turnbuckle in the back would be nice. Lots of cars have rear toe adjustment there with a turnbuckle, and a lot of the front drivers with that type of toe setting have a really spindly looking turnbuckle. Maybe I'll just stick to 5/8" rod ends, which with 18tpi would give a little finer adjustability. If anyone who has AZC arms could shed some light on this, I'd appreciate it. Not sure that I have the skill to mock them up well enough to insure the 3/16" total toe that I would like... hmmm............ Jon Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.