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astroracer
02-03-2005, 02:38 AM
https://static1.pt-content.com/images/pt/2004/09/10951662912-1.jpg
What material should I use for the Lower Control Arm brackets? (the purple ones). I am thinking 4130 x 7ga. I know this will provide a lot of wear resistance but will the welding process hurt the material properties? Am I just being anal or would 1018/1020 be fine if it is braced as I show it in the design?
Thanks
Mark

JohnUlaszek
02-03-2005, 04:37 AM
What does your LCA bushing design look like?

parsonsj
02-03-2005, 05:39 AM
Mark,
If it helps, all my brackets (LCA/UCA in both front and back) use 3/16 material. Don't know if 7ga is 3/16, but that sounds close.

The difference between 4130 and 1018/20 is probably not worth much for strength or weight (unless you are going to use 1/8" 4130 material). Either can be welded easily. You'll find that the 1018/20 material is easier to work and fit, and is easier on your drill bits. If you do use 4130, weld it with the TIG processs, and use mild steel (or stainless steel) filler. Don't let folks kid you 4130 will crack or work harden. It won't if it is welded properly.

I have some of each lying around the shop and have used both on my project.

jp

astroracer
02-03-2005, 09:06 AM
John U.
Here is a pic of the intended Upper and Lower Bushings. Pretty straight forward with steel inner sleeves, Poly bushing and D.O.M. Tube outers.

JP,
7ga. is 3/16ths. I am concerned with hole elongation if the fasteners loosen up but, now that I think about it, the fasteners are never going to loosen up because I am going to be so freakin' paranoid about this whole suspension that I'll be checking it every time I hit a hard bump... :hammer:
I'll be milling the bolt holes to just slip the thread at assembly so I think I will go with the 1018 and just keep my eye on it...

Thanks guys. Just thinking and talking it through with you solves a lot of problems in my mind.
Mark

MuscleRodz
02-03-2005, 09:51 AM
If you control arm bolt will be subject to rotation I would use the 4130 for added wear resistence. If not mild steel should be fine. If you use 4130 and tig weld it, post heat it with rosebud torch to anneal the weld. It will relieve the stress risers in the welded area and should not crack.

Mike

parsonsj
02-03-2005, 10:01 AM
Check out this link (http://www.lincolnelectric.com/knowledge/articles/content/chrome-moly.asp) at Lincoln.

For our use in motorsports, annealing 4130 welds is usually unnecessary.

jp

sanddan
02-03-2005, 11:10 AM
astroracer,

What software are you using to design with? Just curious.

Dan

JohnUlaszek
02-03-2005, 11:45 AM
If the crush sleeve and thrust washers are sized properly the bolt can not rotate. I would be more worried about potential binding issues. I am assuming you will make a welding fixture or post-weld machine your LCA bolt holes?

I use Pro/E every day so I know how much work you have tied up into those models, and I also know what a tremendous tool the solid models are, nice work.

John

astroracer
02-03-2005, 03:17 PM
Thanks for your comments everyone. I really appreciate the help.

Dan,
I am using Unigraphics V18. I run this program at work 10 hours a day...

JP,
I think I will run with the 1018. I may redesign the width of the brackets to incorporate some hardened washers on the inside as bearing plates for the sleeves and bushings.

John U.,
Does that sound feasible? I could tack weld the washers to the inside of the brackets. I could possibly get away with 10ga for the bracket material if I did this.
I will be fixturing everything before it is welded and I haven't decided if I will post bore the bolt holes or not. Probably not because I can fixture it up easier and cleaner then it would be to try and drill the holes after the welding and keep everything square.
Thanks for the complement too....
Mark

JohnUlaszek
02-03-2005, 04:14 PM
Astro
The key with poly is to use the crush sleeve OD as the bearing sufraces for the ID of the poly bushing, this means your sleeve should have an overall length slightly longer than the bushing stackup.

The thrust load is where the problem comes in, you want to handle thrust without creating bind under braking which creates a non-linear rate of change in bump travel. This may not be a signifigant issue for most, but if you are going for an idealized setup, you will want to at least think about this.

Your right about the fixture, post weld machining does not make any sense.

John Or Paul, you want to correct or add to this???

John

ruggles
02-03-2005, 05:58 PM
astroracer

your setup looks pretty good. I have had some experience with poly bushings on jeep suspension(both leaf and 4 link). From what I have seen, poly is good as long as you have a way of purging out the old grease and adding new somehow. Alot of offroad poly bushings are fluted(grease grooves) and use a bolt with a zerk fitting on it. This works nice, but I am not sure how much weaker the greasable bolt is than a regular one. I am sure there are alot of people that will disagree with me (about poly being worth a crap) but I think it is good if you use it how you are intending. Good luck.

Paul

astroracer
02-04-2005, 02:45 AM
Okay guys, sounds like I have a plan. :bananna2:
John U.,
The stackup over the inner sleeve is exactly as you mentioned. I have yet to check it with torqued fasteners in an installed position but I'll do that as soon as I have some brackets made. I will then build my welding fixture to suit.
I think I will use hardened washers on the inside of the brackets and plug weld them from the outside through holes drilled in the bracket. I can then finish off the welds to make them disappear. 7ga 1018 will be used for the brackets.
Ruggles,
The bushings have grease grooves and I will be adding grease zerks to all of the bushings after they are welded up.
Thanks to everyone who has jumped in to help. :worship: If anyone see's any problems with this plan please let me know your concerns.
Mark

parsonsj
02-04-2005, 10:53 AM
Mark,

One thing to keep in mind: hardened washers get that way via heat treatment. Welding them will affect their hardness ... you may be going to a whole of trouble only to ruin them by welding.

jp

astroracer
02-04-2005, 11:29 AM
Thanks John, you're absolutely right. If I keep the tacks to the outer edge and cool the washer between tacks I think that will leave the middle of the washer unannealed. If I can find a washer big enough in diameter I should be safe.
Mark

JohnUlaszek
02-04-2005, 12:10 PM
Astro,
I think the washers are overkill and you run the risk of the washer warping during welding and having to surface grind them to bring back the flatness. If you lube the poly on a regular basis I am sure you won't have a problem.

astroracer
02-04-2005, 12:25 PM
Well, I have been sitting here at work, updating some UG files and thinking about this problem. I have never seen any kind of hardened washer in a suspension of this type, OEM or Aftermarket. I think I am making this to difficult. Forget the hardened washer stuff. I'll use 7ga. 1018 for the brackets and grade 8 hardware to attach the control arms.
This is not rocket surgery so I am going to keep it simple... I just have to remember that when I start 2nd quessing myself...
Mark

Parts Abuser
02-04-2005, 02:22 PM
Mark,
I build all my suspension brackets out of 3/16" mild steel. I've never had a problem with hole elongation. I have seen a car built by another shop with brackets done in 1/8" mild steel -- the holes started elongating after only a few hundred miles. I believe the problem was a combination of the bolts not fitting snug enough in the holes and the slightly thin material.

On a really heavy car, like my 4000# el Camino, I use 1/4" mild steel but this is serious overkill on a car under this weight.
Vince

astroracer
02-04-2005, 05:22 PM
Exactly John...
I didn't see your response until I got home tonight but I guess we are all on the same page. Thanks for all of the help. I tend to get a bit "rectally retentive" if you want to call it that and start to over analize things. My wife wonders how I ever get anything done...
Anyway; I am good to go with this. I will be out working on the new bandsaw tomorrow. Changing the lube in the gearbox and getting it set up to start cutting. I ordered new bi-metal blades from Enco for it and have one of those in place. I don't think I'll have to do much tweaking to get it up and cutting...
Thanks again everyone and don't hesitate to make suggestions or critisizms...
Mark

Tig Man
02-04-2005, 08:39 PM
Major Trans-Am chassis brackets are .090 Normalized Chromoly. it cannot be broke to form 90 degree gussets. You could try Annealed stock but 8 out of 10 times it will fracture along the break line. I think you should make the gusset go all the way to the radius past the hole. We make a doubling washer out of the same material that the parent metal. It doesn't make sense to use chromo if the rest is mild steel. It's only as strong as the parent metal and the welds. Make the bracket flat then weld the gussets. Just my 2 cnts.


Mark

astroracer
02-05-2005, 01:44 PM
Major Trans-Am chassis brackets are .090 Normalized Chromoly. it cannot be broke to form 90 degree gussets. You could try Annealed stock but 8 out of 10 times it will fracture along the break line. I think you should make the gusset go all the way to the radius past the hole. We make a doubling washer out of the same material that the parent metal. It doesn't make sense to use chromo if the rest is mild steel. It's only as strong as the parent metal and the welds. Make the bracket flat then weld the gussets. Just my 2 cnts.


Mark

Thanks Mark,
I appreciate the insight. My plan is to make the brackets and weld on the gussets during assembly just as you suggested.
I will also modify the end of my brackets to run the gussets past the center of the bolt hole. Thanks.
Mark