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Old 01-11-2009, 12:13 PM
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Custome Urethane Rod Ends

Been designing a custom 4-link for my F1. Since a 4 link on a street truck seems pretty rare (due in large part to the binding issues when bouncing over uneven terrain) I have added provisions to switch the links to a parallel 4 bar setup. The bars are 21" center to center and can be mounted in every orientation imaginable. I may even go as far as to add brackets for a triangulated 4 link (lower links parallel to frame, uppers 45 apart from pig to frame). Since this is my 1st truck I'm not shooting for perfection, just trying to really understand as many aspects of the design as I can.

1. Most kits uses 3/16 HR Mild steel (1018) for the 4 link brackets and 1/4 CR for the $$ brackets. 1/4 CR seems a bit overkill for an LS1 (<500HP) street truck.

2. Whats the best way to mount the front brackets? The 4 link will be outboard of the frame. I was considering using a 2x3x0.188 wall tube crossmember extending beyond the frame rails 4 inches on either side then notching 2x3 out of the brackets and welding them in place. I have seen this done on many 4 bar setups, but wonder if there will be too much torsion on the 2x3 tube since the links could be as much as 13" apart vs the 5" normal to the 4 bar setup. The frame will be boxed in so I donít anticipate a 2x3 hole will be a problem. Comments?

3. Seems the most popular urethane bushings are the #1203 from TCI, Hortons, etc. I was thinking a Energy suspension ENS-9-9111G would work just as well. They measure 1.75" long vs 1.4". Both are 5/8 bolts. Any reason not to use them?

4. My links are also custom 1.188x0.25 wall 1026 DOM. Most 4bar kits use 1x0.156 wall 1026 DOM. So already my safety factor is a little better. But does it need to be. For offroad trucks the popular criteria seems to be 1/2 the trucks weight sitting in the middle of the link for bending. How about for a street truck.

5. Rod ends. I can purchase 3/4-16 studs readily online to weld to the tube. However, this seems to be the weak link. For all the trouble of using big DOM links, calculations, math etc etc, I now am going to use a mild steel threaded stud of unknown origin and manufactured to who knows what spec (I'm have seen so much fake Grade 8 hardware I know test everything myself). Machining and welding a heat treated Grade 8 bolt doesnít seem to make sense. I might be able to weld a Grade 5 bolt (this is probably just as good as using a stud). The last option would be to use some B7 (4140) threaded rod, weld bushing tube to 0.688ID tube cut at 45 degree, thread rod into 0.688ID tube, weld elliptical bead around rod, presto custom rod end. This is popular with off roaders, but I've never seen it done on a street rod. What I want to avoid is any form of post heating to temp xx for time xx then cooling in xxx procedure since there are far too many unknowns and I could just as easily do more harm than good.

Sorry if it seems like I'm overanalyzing things. I build dog houses with 2x12's.

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Old 03-03-2009, 08:06 PM
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Small update.

1. Decided to go with the 1/4" CR. 12' length cost $70US which is enough to machine all 8 brackets. I suppose 1/4 HR would have been fine as well but I wasnt sure so what the heck.

2. Ended up buying a length of 2 x 4 x 0.120 tube ($80US) for the rear subframe so I'll use that for the crossmember as well. 2x3 looked a little small but probably would have been fine.

3. hmm bushing... still no decision. See below.

4. Got a good deal on 1 3/8 x 0.120 DOM 1026. So 1 3/8 it is.

5.
Option 1: DIY with 1" grade 5 bolts and Energy Suspension bushing. Under $75 basically the cost of the bushings.

Option 2: Same as option 1 but with 1" 4140 B7 threaded rod with elliptical weld to tube. Elliptical tube to bushing tube. A little over 100$

Option 3: Chassiworks and Morrison have some very nice urethane rod ends. Roughly $300 for set of 10.

I'd like to build my own but question if they will be as strong as the Morrison rod ends. Anyone have experience welding up your own.

Anyone know what material the threaded weld in tube inserts are made of? Are they mild steel or 4130 (normalize, tempered and quenched..etc). If 4130 and heat treated will welding a bead around the perimeter void the heat treatment at the threads? What factors affect thread strength. Looking at the yield strength for 1026DOM it apx the same as normalized 4130N. That would seem to indicate that there is no real advantage to using a threaded insert vs just threading the DOM. On the other hand if the 4130 is tempered and quenched the yield strength is nearly double but is this lost when you weld the insert to the tube????
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Old 03-05-2009, 12:58 AM
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2) Just make sure you reinforce it like with a short angled tube going forward to the frame.

3) If you want the body to roll unrestrained or the axle articulate (like when taking a sidewalk ramp from the street into a parking lot) you don't want poly bushings at both ends.

4) My way of thinking is that any suspension member should be strong enough to jack the vehicle up with.

5) Take a look at these
http://www.speedwaymotors.com/Stainl...Ends,1584.html
http://www.speedwaymotors.com/Steel-...sert,1534.html
Use those on the frame side of the links and both sides of the Panhard while using some type of spherical joint at the axle.

If you don't use a spherical joint at one end it will loosen the jam nut and rotate the threads. Something like a Currie Johnny Joint wouldn't be bad...but the smallest they make is 3/4" shank and they are wide.
http://www.currieenterprises.com/ces...nnyjoints.aspx

Most tube adapters are mild steel. If they are anything else they will be 4130 chrome-moly and will most likely advertise that they are. All the 4130 stuff I have come across were normalized but that isn't to say that will be the case with everything you might run across.
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Old 03-05-2009, 11:54 PM
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2) Yes. .

3) Hmm I hadn't considered using anything but poly bushings. I know binding can be problem with a 4 link on the street when the links are NOT parallel. However, I was hoping to minimize binding by running the bars parallel when on the street. That being the case why are polybushing so popular in all the kits? I'm just as happy using Heim joints but I thought they had a tendency to wear quickly (exposure to dirt etc). Obviously there's a trade off, poly=less articulation and less rode noise, Heim=more articulation and more road noise. Those Johnny Joints look like the best of both worlds.

4) Safety is number one. If 1 3/8 x 0.120 1026 DOM is not adequate for a 50 Ford pu please let me know. Most kits I'v seen online use tube around 1", the more expensive kits use 1"-1.25" 4130N. I'm not an expect but again I'll make the argument that Normalized 4130 and 1026 have pretty much the same Yield and Tensile strength so why pay more for the 4130N????? Is there something I'm not considering.

5) 5/8, 3/4 or 1 inch. 3/4" is about as big as I can go with 1 3/8 x 0.120 DOM and insert.. I too suspect that most tube ends are mild steal. There are many that look like they are made from stock HEX rod. I have yet to find a source of 4130 HEX.
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Old 03-06-2009, 12:30 AM
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How long are your links and how much will the truck weigh?

Think of the articulation this way. The axle will be at an angle with respect to the body. That angle will have to be taken up by the poly bushings. Poly bushings don't flex much. If your links are non-adjustable (welded on both ends) the bushings will flex. If you are using an adjustable link the jam nut has a good chance of being easier to twist than the poly bushings. It might work and you might never have any problems...or... The factory takes care of the twist using stamped steel control arms that are very flexible in twist and soft rubber bushings. If you use boxed aftermarket control arms with poly bushings on a factory 4-link car it essentially acts like an anti-roll bar. Some manufactures are now using spherical joint on one end for street vehicles.

I have found 4130 hex before (it was either 3/4 or 5/8 I don't remember) but it wasn't easy to come by.
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Old 03-06-2009, 11:21 AM
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The links will be somewhere between 20 and 24" long. I'v been using an excellent spreadsheet thats floating around to help calculate these numbers.

Thanks so much for the insight. That makes perfect sense. Thinking of every stock vehicle they all share two things in common.. Super soft rubber bushings (at least compared to poly bushings) and I-beam style or stamped steel links. Both link styles are good for supporting the weight of the vehicle but do little to limit twisting of the links. A tube link on the other hand is very hard to twist.

Thanks for taking the time to break it down for me Triaged. Saved me from having to drive around with an extra wrench in my pocket.
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Old 03-06-2009, 12:15 PM
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Your links will not be strong enough to take a floor jack to the middle. At 24" long it would take something more like 1.5 OD x 0.188 wall. Your links should be able to handle every other load other than a floor jack.
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Old 03-06-2009, 05:35 PM
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Hmm.. I though the 1 3/8 was overkill for a street machine. If I'm not mistaken the spreadsheet was originally geared towards off-road trucks (math is math regardless). In that application it seamed reasonable that the truck could rest on a rock and have half the weight if not more resting on the lower link. For a street machine the only time it would see that load is, like you say, when jacked up. Going back to OEM vehicles my gut tells me that if I tried to jack on the link it would probably bend.

That said I would rather be more alive than dead so 1.5" x 0.188 wall DOM it is.
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Old 03-06-2009, 06:12 PM
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I think most people would call 1.375x.120 more than plenty. In college I designed the suspension for a motorcycle powered race car (Formula SAE). I did all the math to figure out worst case loads on all the suspension. Then it dawned on me...what if someone picked up the car by grabbing the middle of the A-arms? I calculated that load case out and it ended up being the worst case load by far, so I designed around that and made it idiot proof. Those arms lasted a few years till someone hit a speed bump at speed in the school parking lot Maybe you (or the next owner) will take it to a shop to do the brakes or get new tires and someone will put a floor jack under the lower control arm? Maybe you accidentally drive off a curb and land on the lower links? For a race car, sure, make them small and light. For a street truck, that will be heavy with a bunch of stuff that wouldn't be on a race car, I don't see the problem with making something idiot proof by adding just a bit of extra weight. I'm sure my opinion is different than many. As long as you can justify it to yourself, run whatever size you want.

For what it is worth I'm the guy that made that spreadsheet and I have seen rock crawlers bend 2.5 OD x 0.500 wall DOM tubing lower links so maybe I'm just a bit jaded.
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Old 03-06-2009, 06:54 PM
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All hail the Triaged.. That spreadsheet is probably the single most valuable tool I have. Call me weird but I get some strange kick out of spending weeks designing and building something from scratch that, had I worked a little OT instead, could have bought. There's some sort of pride thing that comes with building it yourself (even if it doesn't work the 2nd, 3rd or 4th time).
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