Adjustable Rear LCA

[seattlejester]

So along with my rear end refresh, I would like to try my hand at building some adjustable RLCAs. I figured some input would be a good idea as I am new to rod ends and what specs to look out for regarding thickness of suspension pieces.

 

I will be copying myron's design that he used on his vq swapped z

http://forums.hybridz.org/topic/66749-home-made-control-arms/page-3

 

I am thinking a 1 inch ID pipe with at least a 0.95 wall So most likely a 1.25 OD with 0.12 wall or a 1.25 with a 0.095 wall.

 

The portion that attaches to the car will be salvaged from the donor control arm similar to how myron did his.

 

I am planning on using steel weld bungs that will press into the tube for welding for the female end

http://www.speedwaymotors.com/Steel-Weld-Bung-for-1-Inch-ID-Tube-3-4-16-LH,35663.html

 

I am planning on using chromoly teflon lined rod ends with the 5/8 hole and appropriate thread pitch to match thread of bung above

http://www.speedwaymotors.com/Chromoly-Heim-Joint-Rod-Ends-3-4-16-LH-Male-5-8-Inch-Hole,28919.html

 

I am planning on using a 5/8 bolt in place of the spindle pin

Fastenal part #15335

 

Anyone see any major faults off the bat?

 

I think Myron went a bit smaller with his pipe overall, but I'm not finding the weld bungs for the size he mentions (he says he is using 1 inch tube with 0.095 wall so maybe 3/4 ID weld bung?), I wouldn't mind down sizing if the 1.25 pipe is overkill.

 

A concern would be if I would need to index the 5/8 bolt to keep it from rotating like the spindle pin or if that matters at all. 

 

Another concern is the handedness of the thread, I don't think it should particularly matter except for when you have rod ends on both ends of the rod to accommodate for lengthening the arm without taking the arm off as in the bottom free floating arm.

 

Another concern would be if the rod end selected is adequate regarding thickness (3/4) or if that is overkill and I should just stick with 5/8 to accommodate more threads (thinner locking nut).

[seattlejester]

So more searching makes me want to lean more towards using a 3/4 bung in a 1 OD 0.095 wall tube. There will be a bit of slop, but not much and once welded it should be fine. It will weigh quite a bit less and seems maybe it will be strong enough.

 

I found some lower profile weld bungs in 3/4 that kind of prompted the change. 

http://www.ebay.com/itm/400624698645

 

They are half the price and have a lower profile which makes should in theory be even stronger. 

[JMortensen]

When I made mine I went with 3/4" rod ends, just based on some feedback from people who had used 5/8 and had issues. I do like having the fixed point of the A arm directly under the strut as opposed to in front, but I think it's a minor difference. If you have the fixed point under the strut  then you need a really short turnbuckle for the front. I had to have mine made by Coleman racing.

[seattlejester]

Hmm so maybe advisable to go with the original plan and stay at 3/4, may I ask what issues others have reported?

 

I see what you mean regarding the short turn buckle, that's not a lot of space there. The control arm looks really sturdy though. 

 

Is the sway bar attachment to come later?

 

And what thickness did you go with? That looks to be 0.12?

Edited July 23, 2015 by seattlejester

[Phantom]

I assume that you know that pipe sizes are based on nominal schedule 40 ID and tubing sizes on OD?  a 1" schedule 40 pipe is slightly over 1" ID.  A schedule 80 is slightly under 1" as the extra wall thickness is taken out of the inside.  Also, tubing generally tends to be a better material than pipe.

Have you looked at all your options on a pipe/tubing guide?  It can be a bit daunting looking at all the options and trying to get the ID/OD that you want.

[seattlejester]

Oh I think I misused the term pipe. The material I will be using is DOM A513? It is an actual tube from my metal supplier. The size I am looking at will be either 1in OD with a 0.12 wall (0.76 ID) using a 3/4 inch tube adapter (correct term for the weld in bung) and using a high strength 5/8 rod end, or a 1.25 OD with a 0.12 wall (1.01 ID) using a 1 inch tube adapter and using a more run of the mill 3/4 rod end (with a 5/8 hole). 

 

I have a local metal supply shop that I usually buy from, they have a pretty good guide, but yes it is quite daunting to read through.

 

The seller I am looking to buy the rod ends from says that the high strength heat treated chromoly rod ends should be more then adequate (they apparently use them on suspension and such for big off road trucks), and the weight savings appeal to me. However I think there would be some merit in just going big and not worrying about it down the road. I may just try the smaller ones and step up and modify the design when they start to fail as I doubt I would over build and build it smaller the next iteration. I am curious to hear what problems people have faced.

[makaofox]

My friend with his 2jz 240z made these. He believes hiem joints are a weakness (daily drives 100mi in his 240z). His 2jz z32 blows through them often, could be because of the weight? But He made these a few days ago, I helped him and they really are pretty sweet. The bushings are great and the design I like it, all home depot stuff not even $50 worth.

[JMortensen]

Cheap heims are an issue for sure, but good ones last a long time. I had probably 30K miles on my front LCAs when I took my car apart for the current never-ending build. The old ones were still tight, but they were expensive 3 piece rod ends. 

 

The problem with makaofox's friend's solution is that poly has a lot of friction, doesn't really allow for the angle change that comes with caster sweep, and he has a ton of threads in bending with that design. Looks similar to the Modern Motorsports rear arms, which I never liked for those same reasons.

 

According to this thread I went with 1 1/8" .095 wall DOM: http://forums.hybridz.org/topic/62776-yet-another-rear-control-arm-design/

[seattlejester]

That....was a good thread.

 

Seems really nerdy, but I'm kind of out of breath reading it.

 

The rod ends I was looking at were the 5/8 XM rod ends and seems like Cary wore those out pretty quickly. Stepping up to 3/4 isn't a huge deal since I haven't ordered anything and seems like the style of tube adapter that I want also comes in the larger size. 

 

So current plan...

 

3/4 shank 5/8 hole rod end

 

3/4 thread 1 in OD Tube adapter

 

1.125 Tube with 0.095, this brings the ID down to 0.935 I'm not sure the 1 in OD tube adapter would fit with these. Is there enough slop for that to work? Or did you get custom fit tube adapters? The tube choices that are close to fitting with me are 1.25 OD with 0.95 wall (1.06 ID) or a 1.25 OD with a 0.12 wall (1.01 ID). 

[JMortensen]

I had my tube adapters turned down in a lathe. If you look around there are racing suppliers who will sell you both the tubing and the adapters that fit it. I believe http://ubmachine.com/lowerparts.html has both.

[makaofox]

Cheap heims are an issue for sure, but good ones last a long time. I had probably 30K miles on my front LCAs when I took my car apart for the current never-ending build. The old ones were still tight, but they were expensive 3 piece rod ends. 

 

The problem with makaofox's friend's solution is that poly has a lot of friction, doesn't really allow for the angle change that comes with caster sweep, and he has a ton of threads in bending with that design. Looks similar to the Modern Motorsports rear arms, which I never liked for those same reasons.

 

According to this thread I went with 1 1/8" .095 wall DOM: http://forums.hybridz.org/topic/62776-yet-another-rear-control-arm-design/

Hmm noted. On another note my z used to be tracked in the 70s-80s and still uses a few heims for the sway and strut bar and after 40 years still in great condition. Granted its not on the LCA but still impressive. I have no need for an adjustable set up yet but all good information thanks jon!

[seattlejester]

Ah gotcha, I was not having any luck finding a 0.935 insert that makes sense.

 

I plan on ordering the tube from a local steel supply shop. Their prices are good and I think the metal cost will be 50-60$ for both sides + I have a coupon . I may just step it up to 1.25 OD x 0.12 wall and have super beefy lower control arms.

 

Although I am still tempted to try the smaller diameter with the thicker wall. I know Myron used chromoly, but his tube was only 0.095, I would be stepping up to 0.120. It seems the capacity for even the higher quality ones are 18k at most and at 10% that would only be 1.8k lbs that it could support. Not a problem static, but probably becomes a problem as it is loaded.

 

Bah I'll just build it with the bulky ones and one day when I'm bored and have lots of time and money I'll mess around with 3 piece rod ends and smaller OD tubing.

[JMortensen]

The difference in weight is pretty minimal, not that much tubing here, really. I'm guessing you'll use www.onlinemetals.com. On their site they have weight by foot and you could calculate it out. Probably a lb or two difference.

[seattlejester]

That is exactly who I'll be using, I'll have to go take a few measurements and find out the footage I'll be needing. Pretty excited it's been a while since I've done any welding really.

[tube80z]

I personally wouldn't use the tubing thicker than (0.95).  My reasons are that I'd prefer the arm to bend rather than the frame to get bent.  Same argument for CroMo tube.

 

The 5/8 rod ends that wore out were Auroras.  The liner was pounded out of the fixed end of the lower control arm.  Stepping up to 3/4 ball/race cured that.  For a street car it would be interesting to try and use ball joint style ends.  One of the local hot rodders uses Ford tie-rod ends for all his axle linkages.  He said they were cheaper than rod ends and last about 5X longer.  Only downside if you need to change the mounts.  Rod ends are much nicer in that regard and you don't lose any alignment when taking it apart.

 

Hope that helps,

Cary

[seattlejester]

Thanks for the reply.

 

Are Aurora rod ends of lower quality? Would perhaps a better quality one suffice instead of stepping up to a 3/4?

 

How would one use a ball joint? They don't really allow for a bolt to pass through. I'm struggling to imagine it correctly I think.

 

The thickness being a bit on the thicker side is a fair concern, I just imagine that if the load was enough that it would have broken that it would twist out the bent sheet metal brackets that clamp the control arm to the chassis. The problem is that it seems the tubing adapters are almost tailored to fit those sizes specifically. I suppose I could just use thinner wall and have the tube adapter a little loose prior to welding without much problems. 

 

I would hate to cause frame cracks in my pursuit of tubular control arms. It seems like another vote for the 3/4 thread rod end and another vote for a 0.095 wall tube. 

[johnc]

NHBB and FAG are about the best spherical bearings you can buy. Tubing wall thickness depends on the load. If you're building a autocross/track car that weighs 2,000 lbs you'll run a thinner wall tube. A 2,800 lb street car that hits potholes will need a thicker wall tube. .095" wall is a good place to start.

[tube80z]

Tube adapters can be had in any size for most thicknesses in the 0.065 to 0.120 range.  I'd agree with John that 0.095 would be good here.  Very successfully used on a 2600 pound car with 474 WHP and huge slicks at hillclimbs, track days, and many autocrosses.  

 

To use the tie rod end you have to build a mount that is thick enough to have the taper needed.  Then the rod end is inserted into this.  Take a look at BMW lower control arms inner joint to get an idea.  In the case of the Z it would be a bracket bolted to the strut housing.  Myself, I would opt for using rod ends.  Aurora, NHBB, FAG as John mentions all make quality products.  The Auroras that died were the top of their line and their engineering department was sent the rod end.  All I got back as that the surface area of the ball must have have been two small for the load, which is ludicrous if you look at what's listed as acceptable loads in their catalogs.  All I know is the larger size worked fine for a long time.

 

 It may seem like these are a waste of time to build but changing from polly bushings to rod ends and the extra floating link helped the car put power down better.  And not just in rough areas.  All I figure is that a lot of friction was reduced.  It also made changing the strut out very easy.  One thought on the arms I forgot to mention is that using left right in 5/8 or 3/4 threads changes the toe very quickly.  It might be better to use the same handedness and 3/4 on one end and 5/8 on the other.  This would allow for smaller increments of change per turn.  

 

Hope this helps,

Cary

[seattlejester]

I think I am getting a clearer picture. I think I'll just stick with the rod ends for this iteration as it seems the road is paved and it works well.

 

Regarding the thickness I was thinking, and there is no reason that the V portion of the A arm would need to be the thicker 0.12 wall thickness.

 

So the current plan is to use the 1 inch OD thickness tube adapter in a 1.25 OD x 0.12 wall tube for the actual rod end and the toe link and use the thinner 1.125 OD x 0.095 wall for the V portion of the A arm. That means it will be easier to weld to the factory control arm bit (reusing the portion like Myron did) and similarly not a stretch to weld to the 1.25 OD tube. In case of something tragic like a bad off, the A arm being made of the thinner metal could yield before starting to twist the frame.

 

I am adding NHBB and FAG rod ends to my list to look at. 

 

That is an option to use a smaller rod end for a toe link to get the 18 threads per inch vs the 16 threads per inch of the larger one. I think I want to buy the same size just for consistency and if the larger bearing surface assists with longevity, I would rather stay away from downsizing just to gain a little more toe adjustment.

 

Gaining a real clear picture now, really appreciate you guys stopping in and sharing!

[seattlejester]

Oh my, is the prices I am finding correct for the manufactures?

 

~200 for a NHBB rod end

~50 for a Aurora rod end

~100 for a FAG rod end

 

And I thought I just needed the bore and the thread pitch, but they have all these categories for lubrication and material. For this application what should I be looking for? It doesn't seem like anyone is using a grease fitting, so self lubricating? Or just metal on metal?

 

Head is beginning to spin.

 

Edit: Found a nice article on rod ends from aurora

http://www.aurorabearing.com/pdf/rod-ends-what-you-need-to-know.pdf

 

Quite a good read. So definitely want a lubricating lining from what I can tell. 

 

Still having trouble finding prices for the rod ends from the recommended brands.

 

A friend just contacted me and asked if I needed anything from summit for a summit order. I have found some here

http://www.summitracing.com/parts/hal-xml10-12/overview/

and these

http://www.summitracing.com/parts/hal-hml10-12t

that look somewhat promising.

 

Also sold from the same supplier of the tube adapters are

http://www.barnes4wd.com/Heat-Treated-Chromoly-34-16-X-58-Heim-Joint_p_153.html

I haven't heard back if they are lined with a lubricant of sorts, but price wise they are affordable and spec wise they seem good. 

 

Any thoughts? I don't want to cheap out on suspension bits, but I also don't want to spend more then what it would cost to buy an arm from TTT (although of a different design).

Edited July 27, 2015 by seattlejester