zlalomz Posted February 9, 2006 Share Posted February 9, 2006 If the slot doesn't slip then once you find a set up you like you could tack weld the washer to the box like I did on my old 510. I found a serrated plate with slot and matching bolt plate at http://www.ubmachine.com/rearsus.html Quote Link to comment Share on other sites More sharing options...
Jolane Posted February 10, 2006 Share Posted February 10, 2006 On my car' date=' which has longer arms than normal I have 9 inches of movement before the rod ends touch, and that's mocked without misalignment washers. What I read in my catalog claims 22 degrees of movement with them. On the back of my race car I typically only use about an inch to 1.25 inches of droop. I found it seems to work best by setting the rear limiter at the point where the spring just slightly touches (maybe 20 pounds preload) on a 450 pound spring. And for bump I have about 3 inches but it's really only using around 2. I think these numbers could easily be doubled and you'd still have no issues with clearance. But using some form of mechanical stop would be good so that you don't break the rod end. If that happens the outcome will not be pretty. These are all good things to think about though. And I think this only makes sense on a race/track car. Cary[/quote'] Having a longer arm actually reduces the angle that the rod end must articulate for the same given wheel travel (droop and compression). I am not sure I read your statement the way you intended it, so I thought I would point that out. As for shortening the distance between the inboard bushings (or rod ends), that certainly has an effect on a number of things stress wise. Even just a few inches could really change things. The wheel location in the wheelwell is controlled by the twisting (from a top view) of the LCA. The wheel is trying to move front and backwards relative to the wheelwell, and the only thing to counteract that is the LCA. Moving inboard now, the only thing keeping the LCA from twisting is the inboard pivots, whether rod ends or bushings. Terry's diagram shows the basics of the forces. A moment is created because you have a force (wheel accel or decel) and a moment (lever) arm, LCA. The moment arm length is the NOT the distance from the outboard pivot to the inboard pivots though. The moment arm is the distance from the outboard pin center to the inboard pivot pin, and the moment arm is perpendicular to the force. Sure you can use trig and figure it out a different way, but the simplest is the perpendicular line. For example (I don't have the actual dimensions on me, using round numbers instead): Assume Force = 100 lbs Assume distance = 18 in Moment on LCA = 100 * 18 = 1800 in lbs This moment must be resisted by the pivots, and each pivot must resist an equal amount. Ignore lateral loads for now. Assume original inboard pivot separation = 16 in Force on pivot = 1800in lbs/16in/2 = 56.25 lbs Each pivot must control 56 lbs of force perpendicular to its vertical rotation. Now say you move the pivots closer to each other by 3". New pivot separation = 13 in New force on pivot = 1800 in lbs/13 in/2 = 69 lbs This is an increase of 23%. It is linear actually with the separation distance. Linear increase = 16/13 - 1 = 23% Moments are easy to figure out because you can place them anywhere basically. A twisting force is a twisting force. You just have to make sure that the reactionary force is perpendicular to the moment arm. In the end does this mean anything in the real world? It might. I guess it depends on how close ou want to more the pivots. The lateral loads should not really be affected by the separation distance. A lateral load of 100 lbs will still add 50 lbs load to each pivot. Where is makes a difference is that it is additive. Now your total load for the front pivot (assuming accel) is 56 lbs + 50 lbs = 106 lbs, and the rear pivot is -56 lbs + 50 lbs = -6 lbs (direction of loads in each pivot is oppposite to resist twisting moment). I hope this makes sense. I see the distance as a big deal, and want to make sure that nobody assumes otherwise with negative effects. Joshua Quote Link to comment Share on other sites More sharing options...
tube80z Posted February 10, 2006 Share Posted February 10, 2006 Thanks for the info Joshua. On my tube car I widened the base by a fair amount. For the example about I wouldn't see changing this by more than a couple of inches. On the lateral load why can't you look at it like a triangle? It seems that I've seen a number of books show this for lateral force distribution it inner pickup points. Cary Quote Link to comment Share on other sites More sharing options...
blueovalz Posted February 10, 2006 Author Share Posted February 10, 2006 I'm not sure I understand the question, but...lateral loads will not be twisting the arm about a common point, but will instead introduce a compression/tension load (assumed to be equally distributed between bushings). His example shows how the lateral load was positive on both bushings. If there were no crossbar between the two sides of the triangle arm, then other loads would indeed be introduced onto the bushings/bearings during lateral loads; and then the wider the spacing, the higher the loads would be on the bushings/bearings. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 3, 2006 Share Posted August 3, 2006 I am back into this one again. I bought some threaded tube ends from Coleman and I'm thinking of just using these instead of trying to fit a monoball into the end of the control arm. I figure it will be cheaper than buying reams (the threaded tube ends were $4 each) and if nothing else I'll be able to adjust the rear track width. Got the idea from Ron Carter, who has something similar that Design Products racing built for him. I took an old control arm and cut the end off just to be sure it would work. I've got a lot of work in my rear sway bar and it would have sucked to find out that it wouldn't work after I cut the end off. Anyway, it looks like it will work fine, although the hole in the end of the control arm is more like 1 1/8" wide and 1 3/8" tall, so it will have to be closed up tight around the threaded tube end. I started by cutting the least amount of metal off that I could. It appears that I'll need to cut more, probably up to the sheet metal brace, because the rod end extends the length of the control arm. I was hoping to get the control arm length to stock, and then lengthen with the rod ends if I felt it necessary later on. To maximize rear roll center I'm going to mount the threaded tube end as low as possible on the outer end of the control arm. It looks as though there might be some clearance issues with the curve in the control arm on the left side as shown in the pictures. Looks like the tube end might hit the inside of the control arm before it slides all the way in. I'll have to deal with that if it is really a problem. I also figured I'd cut the corners off the control arm and then shape the end of the arm around the round tube end and weld them up. Any suggestions? I'd love to hear them. Here's pics: I'm stuck dead in the water on the inners. I sent some parts to a machinist to help him with fabbing the aluminum bearing retainers, and to make a long story short, I'm probably not getting the parts back, and I'm not getting any retainers either. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 3, 2006 Share Posted August 3, 2006 I got a little worried when I was looking at these pictures, so I went out and cut the control arm off at the flat sheet. Turns out you lose ALL of the straight part of the leading edge of the control arm. This means that the tube end needs to be set straight into a tube which isn't straight. Looks like I might have to trim the tube end by about 1/2" in order to get it to sit straight in the control arm. Then the issue is getting the control arm bent around the tube end so it can all be welded together. The rear section looks easy enough, but again this front section looks to be a problem. Thinking it might be easier to just keep the straight part at the end instead of cutting it off, the issue then becomes the increased track width. I suppose I could compensate for that with some different offset wheels, but the idea was to get more track width in the front, and hopefully to use the same offset wheels front and back. The front track was already increased by about an inch (total), and then another 20mm was added when I added 280Z front hubs, so this should be pretty comparable to the rear if I kept the straight end on the control arm. I'd just need to buy wheel spacers for the front I suppose. I can't really think of another way to get the control arm to accept the threaded tube end nicely. Maybe I should reconsider reaming the end and sliding the monoball in... Pics of the control arm problem: Quote Link to comment Share on other sites More sharing options...
veritech-z Posted August 3, 2006 Share Posted August 3, 2006 Jon, could you grind out enough clearance to let just the back corner of the threaded tube to stick out, and then make a plate to box in the front of the open control arm? I photoshopped (rather poorly I'm ashamed to say, I'm not really good with this program yet) this up to show what I'm talking about: Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 3, 2006 Share Posted August 3, 2006 Thanks, that's not a bad idea at all. The one thing that concerns me is that the end of the arm wouldn't be gripping the tube end. I had kinda figured on crushing the end of the arm to fit the tube end tightly. There is going to be a lot of lateral load, and if it's just welded to the plate that might not be strong enough. Interesting idea... Quote Link to comment Share on other sites More sharing options...
veritech-z Posted August 3, 2006 Share Posted August 3, 2006 What if you filled the hollow part with some of that structural foam, like they used on the Q45? Not stiff enough? Plus I rather thought you'd be welding the back of it too where it sticks through. Are these steel, or aluminum? (would you even be able to weld them straight to the control arm i guess?) Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 3, 2006 Share Posted August 3, 2006 I have no idea how to quantify what kind of difference that foam would make. You know, it would be welded around the triangular hole that would have to be cut in addition to the plate. Still seems like a weird way to put a load on that part of the arm. I suspect it would be OK, but I'm still a little wary about it... Quote Link to comment Share on other sites More sharing options...
veritech-z Posted August 3, 2006 Share Posted August 3, 2006 Yeah, that's not the place to put suspect fabrication, that's for sure. Is there any way to fab one up and have it load tested on a bench first? I assume like most people cost IS an object for you, but if it's not too much to have it tested in some way? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 3, 2006 Share Posted August 3, 2006 I thought I'd be testing all of my mods with a good season or two of autox... Seriously though, I really wouldn't want to hassle with that. If it came to testing or not doing it at all I'd just ream out the end and press in the monoballs. Taking whatever it was .008" off the end doesn't scare me in the least. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 3, 2006 Share Posted August 3, 2006 I wonder if I could just get a flap wheel and use that to open up the end... Quote Link to comment Share on other sites More sharing options...
veritech-z Posted August 4, 2006 Share Posted August 4, 2006 I thought I'd be testing all of my mods with a good season or two of autox... ] That is so gangster...TCB baby! (taking care of business) Quote Link to comment Share on other sites More sharing options...
tube80z Posted August 4, 2006 Share Posted August 4, 2006 Why not cut as shown and then mount the adapter in some squaer tube and mount it straight on the control arm. This could easily be welded up and takes care of the angle problem. I'd do something similar on the inside too. Cary Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 4, 2006 Share Posted August 4, 2006 I've got some larger 1.5" square tube I think. I'll take a look at that option tomorrow. I'm still not convinced that this will be easier than opening up the end of the control arm .008", but I think the larger tubing would work for this idea. Quote Link to comment Share on other sites More sharing options...
blueovalz Posted August 5, 2006 Author Share Posted August 5, 2006 Jon, I do not know what the relationship of the rod ends are as compared to the OEM bushing centerlines, but my thoughts on this are to take a piece of 1/8" thick (or thicker) steel strap (long enough to span both cut ends and wide enough to completely cover the square holes) that will be welded to the arm. The lengthy bead would distribute the load over a large area. BEFORE you do this though, you would take a hole saw and cut two holes in this strap for the threaded tube ends. These ends then could be inserted into these holes up to the stepped portion, and then welded in place completely around the tube (as it appears to be designed for). After the threaded tubes are welded onto the strap (or perhaps some modified angle would be even better), then weld the strap onto the cut ends of the control arm. A lot of welding, but you would have a definite idea of how well it would be welded this way. The roll center will not be affected by the positon of the sperical bearings in the ends of the control arm. The only way you'll be able to change the roll center back there is to lengthen the 2 bosses between the axle bearings and the arm bushings. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 5, 2006 Share Posted August 5, 2006 Jon, I do not know what the relationship of the rod ends are as compared to the OEM bushing centerlines, but my thoughts on this are to take a piece of 1/8" thick (or thicker) steel strap (long enough to span both cut ends and wide enough to completely cover the square holes) that will be welded to the arm. The lengthy bead would distribute the load over a large area. BEFORE you do this though, you would take a hole saw and cut two holes in this strap for the threaded tube ends. These ends then could be inserted into these holes up to the stepped portion, and then welded in place completely around the tube (as it appears to be designed for). After the threaded tubes are welded onto the strap (or perhaps some modified angle would be even better), then weld the strap onto the cut ends of the control arm. A lot of welding, but you would have a definite idea of how well it would be welded this way. I was wondering what you would say about this. I like the strap idea and I'll use it if I continue on with the tube ends. Thanks! The roll center will not be affected by the positon of the sperical bearings in the ends of the control arm. The only way you'll be able to change the roll center back there is to lengthen the 2 bosses between the axle bearings and the arm bushings. I have to admit, you've got me a bit confused here. I think I understand what you're saying, which is basically that if you don't change the pivot point locations the angle of the control arm doesn't matter. I'm not sure that this is correct though. Think about bumpsteer spacers in the front for a second. The pivots stay in the same place, and only the control arm angle is changed. Same deal here, but to a much lesser extent. The height of the outside edge of the arm could be changed about 3/8" on the outside by mounting the rod end in the bottom of the hole at the end of the arm. Changing the angle of the arm changes the roll center, just like in the front. Or did I get myself turned around there somewhere? Quote Link to comment Share on other sites More sharing options...
blueovalz Posted August 5, 2006 Author Share Posted August 5, 2006 Using the front arms as an example, notice that the spacers (roll center) are above the ball joint (pivot point). This lowers the connecting, (pivot) point in regards to the axle. In effect, it legthens the strut without moving the axle. Looking at it another way, if I were to add a 1" spacer in between the arm and the ball joint mounting surface (the four bolts), I have lowered the outside end of the arm itself, but not the pivot point. The ball joint (pivot) remains in the same exact position it was in prior to the spacer being inserted). In this example the pivot point remains the same regardless of how thick a spacer you add between the ball joint and the control arm. If you don't move the pivot point on the strut, or inboard at the inner bushing, you won't change the roll center or bump steer. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 5, 2006 Share Posted August 5, 2006 OK, you're right. I see now. Thanks. 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.