4-link bump stops, opions please!!!
- Thread starter notaf-ingjeep
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- #22
Cool I may look into those, I've kind of decided to deal with my driveline first. It would be smarter.
You should heat treat the 4130 tube to a Rockwell of 38-42... however I have no idea about what to do with solid stock. I don't know if 1.5" solid round will through harden correctly or whether it will just case harden. Axle shafts are in that ballpark and they're case hardened. Maybe the yield strengths you're quoting are already for heat treated material, but you didn't specify. The reason I bring this up is that I thought the "T6" in 7075 T6 designates a heat treat spec. Are you guys comparing apples to oranges?
Also, shouldn't we be looking at a shear strength or elastic modulus rather than tensile strength? People bend links. They don't pop the ends off.
Also, shouldn't we be looking at a shear strength or elastic modulus rather than tensile strength? People bend links. They don't pop the ends off.
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- #24
I believe that the T6 is a heat treating, a critical factor in the strenth of the alloy. There is straight 7075, and 7075 t6 a stronger alloy. Even at that barely compares to the strength of 4130, which is considered a chrome alloy. I definently would not call it apples to oranges.
I know that I will never break one of my links, a bend is possible but never a total catastophic failure. The aluminum on the other hand has no fatigue properties, regardless of how strong it is. Once pushed past it's yeild point, the point where it becomes deformed, it will fail. No matter what, once comprimised it retains no strength characteristics and breaks. The 4130 when pushed passed it yeild point, where it also becomes deformed, it will be weakend, but will still retain a large majority of it's strength. It will not just fail in the same way the aluminum will. If you don't believe me talk to an engineer, I'm not, just machinist. I deal with engineers daily and it is my buisness to be aware of these things. Today I spoke with our engineer, he said he's has seen 4130 rated as high as 130ksi for a tensile strength. A far stronger rate then what I quoted earlier. That is not the yeild, or the factors of fatigue, just an overall strength rate.
Aluminum links are popular because aluminum possesses a larger spring back. Ultimate strength isn't really a concern when taking about the lower links. The required strength is not that much when talking the forces delivered from the vehicle, in that, the links aren't going to buckle from pure compression. But, they will from hitting them on rocks. Aluminum has some give which absorbs energy and keeps the link from kinking.
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- #26
Yeah, I agree good aluminum has really good qualities. It does have it's negative side, just the same as steel has it's negative. I think if you are aware of what your getting and any comprimises your making for weight, strength,ect.... There are many good choices, even if you did choose to build your links from 7075 as has been discussed. I think you will probably never break one, as long as you've "engineered" it well. Personally I used the solid 4130 simply because I was able to get the same amount of strength in a smaller package. 1.5" vs 2.5" 4130 tube, extra .5" of ground clearance. Also solid is never going to dent, and therefore never loose strength because of it. I however made a comprimise with weight, a big comprimise in the eyes of some. Both alum. and steel in solid form are going to be rigid, good for getting the power down. I would agree that a 7075 t6 would have "snap" more so than the 4130 does. All that in a lighter package and NO RUST makes for one of the best alloys around.
In my case my lower link brackets hang below the frame, so I built them from solid .625 or 5/8" plate. I machined a small step inside on both sides so the heim would clear, making the bracket overall no wider than the frame. They hang a bit low, around where my transfer case hangs, mostly because of extra material I left for bashing. They are going to take a beating, hence why I built them so strong. I was considering that when I built the links themselves, they also will take a hell of a beating in the rocks. So adding that to what we've discussed allready, should make it clear why aluminum is a poor choice in my application. I've just wanted to put what I've learned about these materials out there to benfit others. I would not want to make someone think that 7075 is bad. I think they should consider their application when choosing what material to use in their build. My advice to most would be to just use some good quality 4130 dom tube. Lb. for lb. tube is the strongest stuff out there and 4130 "chromo" is hard to beat. I haven't done the math, but I would say the tube is much stronger and even lighter than a solid alum. unit. I wouldn't advise someone to go from a dom "chromo" tube, to a solid aluminum because they think they are saving weight. You probably wont, your likely to get more weight and less strength. Alloys are cool, and each have special qualities that the others dont. So just be aware of what your needs are, and do your best to pick the right stuff for your aplication.
Overall I feel I've made a good choice only time will tell. My only regret is my heims. I had bought them long before I actually got started building. At the time I didn't want to spend more $, in case my project turned into something like the titanic. They are 3/4" x 3/4" rated for like 16,000 lbs each, and were cheap. I hind sight I would have gone for 5/8" x 3/4", the 5/8" bore makes it a much stronger unit will hold 40,000lbs for a reasonable price. I'm comitted now, I can easly get a unit that will take like 28,000 lbs. Even what I have will take almost 4x the weight of the cruiser each. But there will be some incredible forces created when the hammer is down and you slamming into stuff. At 16,000 lbs I fear they will explode, once again only time will tell. I think that I may redo at least my lower links, if not all 4, but wish I didn't have to. I'd drill them out and re thread them to except a 7/8"-14 thread. I can get heims for a reasonable price that have a 3/4" bore and a 7/8"-14 thread, they should hold 40,000lbs. That thick shank would be sick for adjustment as well, I'd feel pretty comfortable extending them out a bit for some extra length. Anyway I'm rambling on
Do you get your 4130 heat treated? Do you buy heat treated material and then cut/weld on it?
My understanding is that it's characteristics for links are better when it's hardened to a Rockwell C scale of 38-42. That's my plan for my 2" .250 wall 4130 tube links.
However, I have no idea what happens when you harden solid stock. I could believe that it actually sets up internal stress if the outer layers quench and the inner section does not.
My understanding is that it's characteristics for links are better when it's hardened to a Rockwell C scale of 38-42. That's my plan for my 2" .250 wall 4130 tube links.
However, I have no idea what happens when you harden solid stock. I could believe that it actually sets up internal stress if the outer layers quench and the inner section does not.
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- #28
I didn't heat treat them, I didn't feel concerned with it. Never even considered it really, I think that they are more than adequate as is. I don't know what effect it would have on a solid bar compared to a tubing. I'd like to find out though.
I think that internal stress is actually what would make it stronger and far more rigid. Give it some more "snap" or "spring" in the bar. That would be the idea of it all if you ask me but I can't say for sure. Being harder also would make it more brittle, like a 5 grade bolt to an 8. I would think no worries on that though. I would say it's more beneficial for tube, as you could likely run a smaller diameter in the same application. I would be interested to know if there were any kind of noticeable effect when you heat treat them. I would be interested in the cost of the procedure. In any case with a material like 4130, it would only make it better.
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- #29
I talked it over with some of the guys at the shop and thought to add a little more. I'm not exactly familiar with the rockwell scale, or exactly what changes are happening at what point. As you harden it, the more of the fatigue characteristics you give up. With 4130 I wouldn't be concerned as much for my application, as with alum. The strength would be soo much greater, but like a grade 8 bolt if it decides to fail it just does with little or no warning. So it's all what you want, I'd love to try it out on both solid untreated and hardened. You will get more traction with links that better resist flex from the forces acted upon it. But one might consider that puts more strain elsewhere on other components also. It sounds pretty sweet to me and something that could be toyed with until you find what is ideal.
As far as what would differ from tube and solid when heat treated. I would say that there would have to be a small variance between them. Most of that would lie in the processing of it, clearly the 2 would have to be treated different. It would take longer to properly treat the solid because of the time heat would take to reach the core. Therefore the outer layers will get hotter, and then it would take longer for the center to cool. So it may be done in stages or there could be some limitations there on what levels of hardening are possible.
Solid may have no choice but to except more hardening than is possible with the tube. Meaning tube might be capable of being hardened less than solid.
I would be curious to see what effect it would have on my machining. If I make tight, precise threads will they shrink passed the point of being correct? I would assume that it probably would. I would most likely have to compensate for it. I've never machined something then had it hardened. Machining hardened material can be a nightmare, tears up tooling, and can quickly become not worth the cost. I have done no welding on my links, all simple machine work. I think if you went with a hardened material you'd be better off using tube with welded bungs. You would reap more benefits, twice as light as a solid piece of equal strength.
lowenbrau
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Air bumps iz the shiznit...
