Exactly , unfortunately he's already gone to a lot of trouble to build this . Should have done that with a broomstick or something before he started .
Huh? Looks like a symmetrical three link to me. With the lower links connected to the midline of the axle and the upper bar some 6" above that, I cannot see an issue with pinion rotation. The only "work" the spring will be doing is holding the car up. Geometrically speaking it may not be the best set up but should work.
Huh? Seriously? Man I was going to leave this alone but okay... For the record I was trying to be nice to the kid because you have to start somewhere and I respect his effort. I did not say it would not work, but I did say it was not safe (on any car) and I wished him luck. The spring will now receive twist with the torque tube gone and pivots points on both ends of the split bones and upper link. Regardless of the span between the upper link and the placement of the lower brackets in their current location. There is still no support to keep the axle from wrapping up under load or better yet when the spring perches break. This thing is like a table missing a leg. Unbolting the spring would make this concept almost as obvious as wrestling this setup into place. We have not even covered how much power the car may have added to it but it is now effectively degraded from stock capacity. Actually figuring out the correct length for the upper arm would help, tossing all those tin brackets, unsupported cross member, and dropping the lower mounts below the center line of the axle well I guess that is just my humble opinion. However, I see he claims to be a shop owner, professional ch***is builder and "Master Hot Rod Technician" like everyone else with a welder so I'm sure he'll figure it out eventually. Experience "usually" comes with time invested but sure why not. Long before his ripe old age I was working on stuff like this...so what do I know. That little there may be worth claiming came from doing this stuff to my own cars, reading up on a given subject, and most importantly having the ability to tell who was full of ****... So I'm fully convinced most of you guys are engineers or you just grew up without Model Cars, Slots, Lincoln Logs, Erector Sets or Legos to make something so simple this difficult. With a kid building a pile in his driveway for fun, it is a bit different, even commendable. Sometimes the best way to truly understand really is to try, fail and try again until you succeed. He is getting paid to learn very basic suspension concepts on another man's car and I hope that person is aware of this because it is not only very wrong but dangerous. My main concern here is some other "expert" will think this is the correct way to do it and cause harm to others. So you can correct me all you like but I can build a little bit more than a silly three link before I need help from any Google happy expert.
Ok Algon, you finally used words i can understand "table missing a leg". In backyarders terms; the spring is pushing down at the back of the axle due to weight of car. Then, you give it the gas and the pinion nose tries to rise up....and the way the bones are attached to the FRONT of the axle, there is really nothing holding the rear end from moving forward....actually the axle will be forced to move forward under torque??? because the top link has a better grip on the rear end. can anybodt follow what i have trouble explaining? i honestly think that each time you apply any torque to that rear, the axle will be foced to move forward slightly. And I am no engineer, so I don't know if that movement would be equal or if it would make the rear end "steer" during torque.
Let me rephrase that a little: The weight of the car is on the back of the rear end, causing a condition that would make the pinion try to rise, just sitting there. Now you apply driving torque which will want to rotate the rear end, and the way the lower bones are mounted, those bones mounts actually force the rear to "squat" and also move the axle slightly ahead? edit; like I said I am no engineer, but the more I look at it, I agree it is dangerous as is. I "think" that car is prone to torque steer??
Brother that sounds good enough to me. Steering would be limited by the amount each joint can index and the amount of triangulation in the bones or the upper link ( which there is none here). The best thing present is the fact that the points are all bushing mounts except for the tie rod ends up front which would help limit this action.
Something like that . It's messed up in a couple of ways but I don't feel like writing a book . The car needs ladder bars and the word " master " is one that no one should use to describe themselves .
Ok, first off the principle is sound. Symmetrical three links have been around for a while and are not considered unsafe by any means. Three links work no differently than parallel four bars or triangulated four bars concerning axle rotation. Three links in this case control axle torque identically to triangulated link systems. The only difference being where the roll center is. On a three link you can use a panhard rod or other means of controlling sway and thus lower your roll center. Triangulated four bars have the roll center at the convergence point of the upper angled bars. Don't even know where to start with your table leg ****ogy, ever heard of a tripod? I hear they are quite stable... take the time to look it up, I'll wait. /sarcasm There is actually a concern using this type of suspension and it is axle torque. But this can be compensated for by offsetting the upper or "odd link" to one side or the other. Billy Shoppe has set up some nice little calculators to actually figure out where these points need to be. http://www.racetec.cc/shope/tim.17.htm http://www.racetec.cc/shope/tim.39.htm Tin brackets? I don't know what material he used here but appears to be at least 1/8" mounted in double shear for the upper control arm. That tubular system "looks" pretty sound, although floor pan clearance will be a PITA. Without knowing the materials used it's kind of hard to snap to judgement on. Length of the arm has more to do with the geometry of the system and less on how to control axle torque. The lower control arm links in my personal opinion are a bit dodgy. They would work for a period of time but the end plate on the tapered tube is putting a stress ring around his four-bar type bar. And the X-member is great for supporting the ch***is on these cars but as the bracket is shown could be done much better. Most of these types of connections will span either the outer frame rail and the inner X or span between the two legs of the X. Are you aiming this insult at me or the OGP? It seems you are making a few snap judgments about the OP here. You should be careful of those, they tend to bite you in the ***. Yeah, those "experts" are all over the HAMB these days. But thank you for the hyperbole. It's brightening my day. In part I do agree with you. There are more than a few people here more than willing to offer their opinion. Some of these opinions are coming from the old guys that think they have the world by the balls via their experience. And then there are some guys that hang around here and try and help guys that have more than just tangential knowledge about automotive suspensions. Some of these guys have even read real suspension publications before the internet and popular search engines. Have a great day!
just unbolt that spring.. and watch it collapse. the brackets he made for the lower control arms (attached to the rear end), those need to be about twice as thick. i dont think the 1/8" material is gonna hold up that well. you could also box them in. anf maybe get away with using that. i would def get rid of the, looks like tie rod ends, on the oppsite part of the lower control arm.
I think pretty much everything has been covered here that I thought...and to be honest I skimmed this and am by no means an expert on this, but I have done quite a bit of reading and research on multi-link suspensions (mostly off road stuff). I do believe there are some issues with this setup, but I don not think it is a complete loss either. I think the lower links being mounted on the front of the axle, while not "ideal" will work just fine for this application, since realistically we are only talking about a few inches of suspension travel. The major issue I see with it is the angle of the upper link. Because from a side view the lower and upper links intersect behind the axle it will essentially rotate as a system behind the axle. Meaning when you nail the gas it will probably squat really bad (or jack it way up because of how steep it is), and it will llikely jack way up under braking. But like i said, I am not an expert and to be honest it is kind of hard to tell just from the pics. Generally (at least in off road trucks) you try to put the intersection of the upper and lower links right at the top of the bellhousing or so...which is usually a good approximation for the COG of the vehicle. This way under acceleration or braking the vehicle will behave well and not squat or lift too much. Of course you can adjust this depending on your taste and what you are trying to use the vehicle for. But basically what I am saying is that the upper link mount on the axle needs to sit off of the axle more to point the link more straight ahead. Or make the front mount lower...but I would go with option 1 if clearance will allow. I do like the design of the upper link mount on the axle...simple and strong, just slice it in half and add a few inches to the height. Now, like I said, I skimmed this, but I am ***uming you are not running the torque tube and upper link at the same time? I thought I saw this was just set up as a mock up until you go to open drive, but I am not sure. Here is a good starter for research on this, and I know that it is for trucks, but it still applies to this: http://www.4wheeloffroad.com/techarticles/suspension/131_0307_four_link_suspension_part_2/index.html . If I can say this without getting flamed I think more people need to look into truck stuff when when they are researching stuff for their rods...and visa versa. Pirate 4x4.com has been a very good source or information for me over the years for various projects. Ok, I'm done now.
Have a great day yourself. Rough maybe but there were no snap judgments, and other than addressing that I disagree with you more power to you. I do like the table comment pudding that made my day. I fix broken and twisted suspensions on a regular basis. Most are drag cars or wanna be G***ers but I dabble in road racers too and while I certainly can learn something... That person is A. holding back or B. not posting on this worthless thread. This is not the same as a four link, and will not work like a four link or even proper 3-link in its current state sorry not going to happen. Now if you corrected all of the wrong the basic idea is valid as you said . You are again trying to justify things I do agree on... I disagree with his product, the fact it is a customer paying for this, the actual parts and materials used and of course your ideas on this under the loads it will see even with a gutless flathead. Until I got the responses I did and saw the ****y posts to others trying to help I had no issues. I do tire of seeing fly by night ******** that people can get killed in so it struck a cord with me. Biting me in the ***? I think not, you see I fabricate my own stuff from scratch, I don't buy bolt on parts, or copy others. While my note of was of Jalopy Kids self proclaimed ***le that I found amusing, my comments before were general. I've read some articles too but that doesn't make me an "Expert". Building high horsepower cars that don't break however does make me rather more experienced than average. Now this thing is not vintage, and has a bit of room for improvement, but I was the kid's age then, and we were on a budget. It is a little more advanced than clip jobs, and bolt ons though. I do a little better now... That is directed at your kits and Dakota front clips so I'm clear. Which I can not say are all bad to be fair but they no ground breaking improvement world shaker here that you think I'll be humbled by sorry. The fact you do not think this suspension is unsafe amazes me. Positioning the links is major factor here and not something a few turns of jamb nut will fix. By all means copy it and see where it gets you.
I'd also like to throw in those front TIE ROD ENDS on the lower arms look pretty feeble too. If you're going to use tie rod ends to control torque, at least make them beefy or better, use bushed ends like you did at the top.
Hey spinz, ever had one of these rear axles apart? If you did you would realize just how thin the material those axle tubes are made of. The 1/8" tabs, if that is what they are made from, would be just fine as the tube would surely give up before the tabs ever would. And tie rod ends have been used for this type of application for decades. It's the "traditional" thing to do. It works, period. Not a concern for failure. Skimming can leave out some critical info, for sure. He did mention that the entire reason for doing this system is because he is removing the torque tube and going to an open drive. What you are trying to get at is called Anti-Squat, oddly enough. And the conditions you are trying to describe are shown in percentages in how they relate to the vehicle CG. It's pretty common to see off-road guys use anti-squat ratings in or above 100% but on street it is way more common to have sub-100% anti-squat lines. Without setting the rear suspension up in the desired ride height it makes it much more difficult to determine these properties correctly. And Pirate4X4 is a very good website.
Thanks for your professional input Steve. I still say those tabs look thin, at least a tad thinner than I am used to seeing/using.
The biggest problem with your table ****ogy is that the table legs are bolted to the floor. Remove one and the table doesn't come falling down, you dig? Really? I build street driven cars and racecars too. Is your A B sentence going anywhere? Just what, and be very specific here, does not qualify this rear suspension as a proper three link rear suspension? Don't hold back and please use technical terms. So people agreeing with your ***umption makes you correct? Or are they equally incorrect? Do you need a gold star? If you can properly show how this suspension is unsafe then I will send you one. Don't hold back man. You do a lot of ***uming. I don't need to copy this, I built a system like this a few years ago. Works very well. Please, I'm dead serious here, show the HAMB your knowledge and prove that this system is unsafe. Do not use snappy ****ogies, use technical terms maybe even draw a picture or two. The burden is on you to show that this is a dangerous set up.
I agree with Elpolocko. This thing will work, the main problem with it being pinion angle change during suspension travel due to it being an asymmetrical three-link. There is a valid point made about squat and rise, but we don't know the intended use for the car. I do know how well a properly set up three or four link can work, and this set-up leaves a lot to be desired as far as geometry, it's probably OK though in a low or average power situation as there is most likely a small amount of suspension travel.
The table has wheels on each leg. On me I think not... You are the pro right? I should make a model for you ? Really you think what you are showing me here or have is more advanced than what a back yard builder would come up with or buy from Speedway? Fatman ? TCI? Or copy off a factory design really? I have to prove something to you? The best of the multiple ways this could be done "vintage or not" in either setup? Gold star no but will I ever, need to go to you for parts, help etc nope. Something snappy, okay? Good enough or it fits better might cut it for a parade car , street rod, or what ever you want to call it but I feel over built is a better bet. I'll gladly admit I'm more for the vintage side of things. However if I was ever at loss I'd buck up and ask a buddy at work. Him building supercharged warrior cars such as Mickey Hale's Warlock, the 14-71 PSI blown Aries Willys we have with the cantilever suspension, and the 429ci SBF Dastun 280 road car is quite more impressive in my book than anything you have posted that I can see but you never know...
You can't prove that the suspension in question is unsound so you are going to resort to an ad hominem attack. Nicely done! I'm not hear to ****spar, I was asked to review and comment about this suspension system. I have, while I don't agree with some of the OP's execution his fundamentals are sound. You have clearly demonstrated a lack of working knowledge about this type of suspension by omission. If it were unsound you should be able to demonstrate why quite easily. To wit you wave your credentials around to prove your worth. Fantastic, your floor. Carry on about yourself and your accomplishments.
Oh,I've had a change of heart. Lets delve deeper into your table ****ogy shall we? take a table with four equally spaced legs. Bolt those said legs to the wall so the table surface is vertical. Say the attachment point where the table leg meets the top has a certain amount of give to it. The table cannot be rotated to horizontal but can move up and down. If you remove one of the upper legs from the table the table is not any more prone to horizontal rotation than before the leg was removed. The one upper leg left does have to do twice the duty than before.
I would really like to see your concise explanation of how the spring is now under more stress than before. Explain it like I am the idiot you think I am.
Bored/stuck at work on a Saturday morning, wrapping my head around it. Here's what I can see happening.... The lower bars being angled slightly to the center of the car would put some bind in the setup so there would be some resistance to this happening. But...the spring (and the weight of the vehicle) is behind the axle and puts leverage on it. The upper and lower links of the suspension on the axle are not inline and the upper mount acts as a pivot for the housing. The axle folds up and stresses the spring and shackles. If the lower pivot was underneath the rear axle I don't think it would be an issue. Or if the spring was mounted to the top of the axle there wouldn't be any leverage. But this is just high school level geometry I'm talking about, and I didn't pay that much attention in cl*** anyway....and greatly respect anything El P has to say about anything suspension related.
correct me if I am wrong but if it becomes apparent that there is a problem because the third link is too short can it not be corrected by putting a bend in it so that as it arcs, the arc of the third link will directly relate to the stabilization of the rearend pinion angle? As the rearend goes up the bar has a bend which brings the pivot point forward maintaining the pinion angle, simple solution, however I am sure that jalopy kid has tested this theory already. I agree with El Polacko in what he has brought forward on the board. The reason I ask is that I am not a suspension guru but I work with industrial process equipment and in some of the material transfering machines the basic theory is essentially the same.
Damn and I thought seeing is believing. So actually building this stuff and making it perform to this level has no merit without a how to manual for others? That's a forum for you.... I have already addressed this suspension, should that not be enough or too simply put oh well. I have real cars that need time in working models and testing so you keep the floor and the three link. Oh and if anyone needs a NHRA legal sub 6 second car or wants to set record sixty foots in any cl*** without the Bickle price. We'll build you one, we will of course gladly hide behind our experience and we are *****s so we'll keep to ourselves how it all comes together.
Forget the upper link; the real issue has been said many times here, it's the way the lower bones attach at the axle facing front. That is now acting like part of an "over center" device like an old toolbox latch or a pair of vicegrips. ...stay with me here.. .. When you operate a over center device, and when you get very close to "center" (like vice grips or a latch) you reach a point of no stability in controlling when it snaps closed. that's when it is near "center" So, with the lower bone mount at this theoritical "center", the bone is at it's least stable position for doing anything. If that mount was pointing down under the tube, you now are no where near center, and lots of force would be needed to have the axle rotate even a little. That's what i thought algon was referring to as a 3 leg table. That bone mount not only does not keep the axle from rotating, it actually encourages rotation when combined with the car weight pushing down on the spring mount....and ANY torque applied in accel or braking, and the bone mount adds NO anti-rotation resistance. i'm working on open drive ford bones right now today, that's why I am reading all this stuff. I don't build tons of cars..so I read hamb.
What is left out of the second drawing is rotation of the upper link mount, it should have rotated with the rest of the housing. For the axle housing to move this much the upper link would have to strech quite a bit, or the lower link would have to compress. Chris
The drawing isn't perfect (a quick MS Paint sketch) and I didn't re-draw the top mount. The upper doesn't stretch, the lower doesn't compress, but what would happen is the spring mount on the rear end twists counterclockwise and moves forward, twisting/stretching the spring and shackles.
The upper doesn't stretch, the lower doesn't compress, but what would happen is the spring mount on the rear end twists counterclockwise and moves forward, twisting/stretching the spring and shackles.[/QUOTE] ***uming the axle doesn't move up or down, how can it twist with solid links holding it in place? It may twist a tiny bit due to the bushings compressing, but that wouldn't be much at all. If the axle rotates, either the to mount has to move to the rear, or the bottom mount has to move forward, or a little of both. Chris
Only issue with your drawing is the upper bar attachment point did not rotate with the housing. If you plot it correctly the pinion points down (clockwise) under compression not up (anti-clockwise)
Seeing what? You haven't proved or even explained how your position on this system causes the load on the spring to increase. Or how this is not a true three link system. Come on man, dish out some of that awesomeness you are throwing around. I mean to say, a man of your fantastical accomplishments should be able to thoroughly trounce me. I'm even leaving myself wide open to your humiliation. Show me the theory and stop puffing your chest!
Just out of curiosity and for the sake of K.I.S.S., why not parallel leaf springs for this particular application? Larry T
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