Spherical bearings 2g

[greengoblin]

I'm building a roadrace/hillclimb car and I'm reseaching as best I can my suspension setup. I plan on replacing all my bushings with spherical bearings.

I have seen this thread where it was talked about using spherical bearings in the control arms.

http://www.dsmtuners.com/forums/handling-tech/168643-lateral-grip-vs-weight-transfer.html


I have also read this DGs Autocross Secrets aka Autocross to Win - Suspension

As the grip goes higher, you need something stiffer than poly, so you do high-quality, Teflon-lined spherical bearings in every pivot point.

However I read here: http://www.dsmtuners.com/forums/handling-tech/260479-megan-racing-rear-trailing-arms.html from Charles that doing the trailing arms may not be such a good Idea.

So my question is:
Is there any place where you would not do spherical bearings? Is so why?


Any help links ect would be much appreciated.

I plan on posting pics and details on the install of my bearings once I start here.

Kevin

 

[ACM]

I think that if you replaced every bushing in the rear suspension with a spherical bearing, it may be OK.

The bushings are designed to flex under load, to change the toe as the car loads up laterally. There are flexible bushings at each end of every link, with the exception of the toe link, which has an outboard ball joint. Without modeling this (or physically doing it) I don't know whether the rear would work 100% with all spherical bearings - it presumably will. I do know however, that if you replace the bushing with a spherical bearing at one end of those links, then you've halved (very approximately) the stiffness of the combined bushings of that arm - so things will flex more, not less.

It is plausible that under certain circumstances (eg slaloms), the car may handle better, it is almost certainly the case that under most circumstances it will handle worse - otherwise Mitsu would have made the bushings softer from the start, to improve NVH.

It's unfortunate that DG's not around here as he would have considerable experience to add; I don't know how far he went down this road, but SM rules do allow all the suspension bushings to be replaced with spherical bearings - perhaps there's info on his site ?

One last point regarding the use of spherical bearings in place of rubber bushings. The inboard pickups were modeled using the loads produced through rubber; changing to a metal joint will increase the peak loads by at least an order of magnitude. It is probable that the mounts will fail if they are not reinforced - at a minimum large washers under the nut and bolt will be needed to spread the loads, and quite probably reinforcing plates will be needed to stop the mounts themselves being torn out of the shell.

Further, in the case of the front lower compression arms (the curved ones), these are mounted in single shear. Doubtless Mitsu modeled MTBF to infinity when spec'ing the bolt sizes and properties, but that will be completely insufficient when that inboard bushing is replaced with a spherical bearing. The simplest way will be to weld on brackets to put those bolts in double shear - but it absolutely will need addressing - the results of those bolts snapping (which they will) will be catastrophic.

 

[greengoblin]

I dug through DG;s site and What I found was only this:

"As the grip goes higher, you need something stiffer than poly, so you do high-quality, Teflon-lined spherical bearings in every pivot point."

This is why I opened this thread since some info on this site seems to contradict that statement.

However looking through his pics I only saw his front lower control arm done.

I'm really trying to see where spherical bearings will work and where not. Perhaps where the shock mounts to the front lower control arm? Would I want the inbord bearing to be spherical in this arm too.

Would a plain bearing would be a better choice in the upper control arms? Or maybe delrin or UHMW Polyethylene?

Where is poly a good choice? In the trailing arms? Or maybe use Delrin on the inboard bushing here?

And where if a soild bearing is gong to be used the mount would need to be reinforced. I have to say lookng around under my car it look like a lot of point cound use a bit more reinforcement.

I'd like to have all this info in one tidy place.

Also what does NVH stand for?


Kevin

 

[ACM]

You wouldn't want a plain bearing - a needle roller bearing would work there though. And on that subject, I'll revisit our experience with upper arms; in ESP, we have to use bushings that "have the same metal-to-non-metal ratio as OEM, and no more actual metal than OEM" - approximate wording, but the precise intent. Using Delrin for the upper A-arm bushings has resulted in multiple fatigue cracks radiating from the bottom fixture points of the tubes the eyebolts fit through. We have welded crack after crack after crack in these areas and it just cracks again. That's what you're up against. Mitsu modeled this area with the assumption of rubber bushings - even though there's very little rubber actually in them, so imagine the difference in loading the lower arm pickups will experience.

You want as many "non-compressible" bushing replacements as your rules allow, simple as that. Spherical bearings are much easier to deal with in the long term, as once you've accommodated the fitment requirements, you're - you just pop them out and replace them when they wear out. With custom plastic bushings, it's special machining every time they wear out - it's a pain in the @$$. And they wear out with infuriating regularity once you're pulling well over 1G.

The front lower arms are prime candidates for spherical bearings due to their considerable 3D movement. Shock absorber mounts are a must, top and bottom. The bushings at both ends of the lower rear arms (outboard they're in the upright) as they're quite soft and designed with more flex in certain planes than others. The upper rear arms will probably benefit from a spherical bearing in the top of the upright - certainly something other than the stock bushing as that tears apart regularly. The inboard pickups for the upper rear arm could be needle bearings, spherical bearings, or Delrin/Poly to give the sheet metal a prayer of surviving.

Anywhere you can get a metallic bearing to function without damaging its environment will be a good candidate - any unintended, uncontrolled, or unpredictable changes in suspension geometry will move the car back from its maximum potential grip, and that's bad.


NVH = Noise, Vibration, Harshness.

None of the suspension mounts were modeled for metallic joints other than those using ball joints, so it's highly likely that every non-ball joint attachment will need reinforcing. Modern cars are totally modeled - once MTBF reaches infinity (or whatever the manufacturer deems appropriate) no additional strength is added beyond that. That pretty much guarantees the mounts will tear.

 

[greengoblin]

Charles,

Thank you for taking the time to give such a detailed answer. I'm going to really start digging into this area in the next few months. I'll come back here and post what I plan on doing. Then show what and how I did it.

If you happen to talk to Dg steer him this way too.

Thanks again,
Kevin

 

[greengoblin]

. Using Delrin for the upper A-arm bushings has resulted in multiple fatigue cracks radiating from the bottom fixture points of the tubes the eyebolts fit through. We have welded crack after crack after crack in these areas and it just cracks again. That's what you're up against .

Do you happen to have any picutes of the cracks. Also did you ever come up with a way to reinforce the fixture points of the tubes the eyebolts fit through.

Kevin

 

[greengoblin]

I have been doing some work on my rear crossmember to prepare it for the possible use of metallic bearing. I figure even if I end up using poly when it can't hurt. I'll be moving to the front crossmember and other points next. All input and suggestions welcome and appreciated.

So on to the pics.
Stock rear crossmember

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Holes cut to plug weld plate in place.

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Plate installed

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Boxed other side and added gusset.

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Stitched the seams

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Solid Bushing for crossmember to body.

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[ACM]

Do you happen to have any picutes of the cracks. Also did you ever come up with a way to reinforce the fixture points of the tubes the eyebolts fit through.

Kevin

I run SCCA Solo rules, ESP - I'm not allowed to overtly reinforce anything. Basically, we just kept on welding up the cracks until finally it stopped cracking.

Were I allowed to strengthen the area, I would use a 4"x4" or so plate shaped to fit, drill it full of holes and then weld every hole to the body and seam weld the edges, that should take care of the problem. This is for the underside, in the wheel well - I've never seen the upper mounts crack unless the lower mount has already broke loose.

Charles

 

[greengoblin]

Charles,

Is this the area where you had the cracks occur?

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I'm really interested in how these tubes are mounted to the body. I cleaned the seam sealer from the top and from what I can tell by probing with a wire along beside them is they are only supported/attached maybe 180 around. I really expected them to be supported from all sides. Have you actually seen this area pulled apart? Just curious.

Your plate idea was where I was headed as well. Thanks for all you input.

Kevin

 

[greengoblin]

Here a up close look at my front lower lateral arms loaded up with the spherical bearings and standoffs. I used a wide series number 14 bearing in the arms. The standoffs are made out of 4140 steel.

You can find it here:WPB-TG Spherical Bearing Series on QA1 Precision Products, Inc.

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Here you can see the groove I had cut for the retaining clips

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[99redgst]

Looks good. Plan on installing spherical bearings else where as well? Looks like I need to make some friends that work at a machine shop. Keep us updated on this project.

 

[greengoblin]

I'm going to be loading up the upper arms for sure . I'm starting to work on that right now.

I'll be posting my bearing info here. If you would like to follow the rest of the build it's here. Goblins AWD project - Mitsu-Media

I may do a blog at some point on here. At the moment I have to much going on to maintain two. Or you can call me lazy

I'll post more as a I can.

Kevin

 

[psycho]

Just curious...How would these perform on a street car? And what I really mean is, how long would they last?

 

[greengoblin]

The SPC front upper control arms have crappy vulcanized rubber bushings in them that are not going to cut it. So I went ahead and load the inboard pickups with spherical bearings. To do this I had sleeves built for the bearings and cut grooves for the retaining ring. The circle clips had to have a bit of the edge ground down where the pliers engage them but the dremel made short work of that,

I'll post the specs soon.

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[greengoblin]

In case some one want to make a set. I recommend you verify your specs but this will get you well on your way.

This is the bearings I used: Part Number WPB10T, WPB-T Spherical Bearing Series on QA1 Precision Products, Inc.

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[snowborder714]

Thanks for posting the drawings Kevin!

How do the ones in the drawing compare to the standoffs needed for the lateral arm? Do you have separate drawings/specs for those?

 

[eclipsh]

Interesting project. I've been debating which way to go with my bushings. Now I can watch you and see what the results are

 

[greengoblin]

Front Lower Lateral Arms (lLower Control Arm)

You will need to make 4 of each standoff.

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[greengoblin]

Right now I'm looking into tackling the compression arm.

Kevin

 

[turbosax2]

Kevin, I'm so jealous! Your project is looking absolutely amazing. Good work, and the best of luck to you! Thanks for the specs too.

 

[greengoblin]

Kevin, I'm so jealous! Your project is looking absolutely amazing. Good work, and the best of luck to you! Thanks for the specs too.

Thanks for the kind words. I'm glad a few people are interested in what I'm doing. You keep up the good work too.

More to come soon I hope.


Kevin

 

[eclipsh]

I'm glad a few people are interested in what I'm doing.

I read through your build thread on the other site. If more people knew about that I'm sure you'd have a huge following over here on Tuners. Incredible work I wish I had the equipment/knowledge to do what you are doing.

I am curious how your front end will hold up with the spherical bearings. Are you replacing the bushing in the rearward, curved arm as well? If so, rumor has it the 2gb arm is stronger than the 2ga. It might be worth switching out to this stronger arm since so much more stress will be placed on it.

Also, can you let us know in this thread when the other one is updated?

 

[deth2u]

Those are pretty hot. I have a question though. Both lower arms have torsional movement on the end bushings as the toe changes (steering). When you turn the rack, this seems to pick up most of the turning motion from the knuckle. Obviously not good for performance.

If you had solid bushings, I'm pretty sure you're putting a lot of stress on the front crossmember and the ball joints on the end of the arms, as well as turning them quite a bit in their sockets.

Am I wrong here? I plan on switching out my polys for solid someday, but this has kind of irked me.

 

[greengoblin]

Those are pretty hot. I have a question though. Both lower arms have torsional movement on the end bushings as the toe changes (steering). When you turn the rack, this seems to pick up most of the turning motion from the knuckle. Obviously not good for performance.

If you had solid bushings, I'm pretty sure you're putting a lot of stress on the front crossmember and the ball joints on the end of the arms, as well as turning them quite a bit in their sockets.

Am I wrong here? I plan on switching out my polys for solid someday, but this has kind of irked me.

By know means is this for the everyday car or even the average enthusiast. I'm not saying you are either just putting that out there.

Yes the do move alot. This is why the bearings are needed. IMO I would not put them a stock crossmember. I'm going to modify mine quite a bit to handle this. I think the ball joints will be fine. It should be noted that I said think. I'm not an engineer.

I'm basing this off what Dg has done this with good results and also have the help of my good friend. He has built sprint cars and street rods for 40 years. I'm going to give it a try an give my results.

I will and do inspect my car all the time for cracks slop ect. I recommend anyone who tries this to do the same.

 

[deth2u]

By know means is this for the everyday car or even the average enthusiast. I'm not saying you are either just putting that out there.

Yes the do move alot. This is why the bearings are needed. IMO I would not put them a stock crossmember. I'm going to modify mine quite a bit to handle this. I think the ball joints will be fine. It should be noted that I said think. I'm not an engineer.

I'm basing this off what Dg has done this with good results and also have the help of my good friend. He has built sprint cars and street rods for 40 years. I'm going to give it a try an give my results.

I will and do inspect my car all the time for cracks slop ect. I recommend anyone who tries this to do the same.

If you decide to box the front crossmember up, post some pics when you get a chance. I'll be reinforcing it in a couple days also--it's pretty much the only thing in the front right now. Hard part is making it strong and having clearance for everything that's supposed to be there.

I was asking because when I was inspecting it, the lateral arm mounting point looks extremely cheesy from the factory. It's all rolled over sheet metal that's been tacked together. Doesn't look very robust at all.