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Holy Sphericals Batman!


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#16
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While some of the technical terms are a little over my head, I really like the idea of this. I have seen it in some local track cars and will be looking forward to some prototype results.

Great work David.
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#17
firstgencrx

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QUOTE (EPcivic @ Oct 31 2009, 03:16 PM) <{POST_SNAPBACK}>
My guess is that if you were to fab up a quick bushing to hold the torque arm to purely rotational motion, you could check the resulting path at the other bushing location pretty easily.


Now that's an excellent idea Chris! Let me see what I can piece together. I'll mock this up on one side. Then I can just articulate the whole thing and get a real idea of what is really happening. What I'm hoping is that with the non-rubbery flexible temporary joints, I can compress and extend the front lower control arm and torsion bar arm assembly with little binding or effort. I'll leave the torsion bar in the assembly, but release it so it's just going for a ride. I'll try and do a test tomorrow.

I did take some twist angle measurements this afternoon on the side that is still mocked up in rubber. I installed a torsion bar into the system, and compressed the system under load so it was as real as possible. I took angle measurements with an electronic level that has a not so impressive accuracy of +/- 0.1 degrees. I adjusted the arm assembly from full drop, to full bump plus 2" of additional bump travel for the folks who run shortened bodied struts. The angle measurement was done right between the two bolts that hold the lower control arm to the torsion bar arm.

The torsion bar arm twisted between plus 1.9 degrees, and minus 1.9 degrees of twist. I hope that made sense. I set the level to read 90 degrees in the center of full travel. Below and above that position, the level read +/- 88.1 degrees at the extremes of travel. The arm also did not appear to be twisted in the center of travel.

I also pulled a straight string across the bottom of the front sub-frame, just over the torsion bar arms (remember, my car is upside down). I was trying to detect any bending of the torsion bar arms at the different positions. As you can imagine, the lower control arm swings so there is a sort of arc that makes tiny changes in both camber and caster as this assembly is compressed and released. The caster changes are what I'm interested in. The amount is so small, I couldn't really tell any differences just by looking at it with my eyes. I'll try and devise a better way to measure any bending that is happening to the torsion bar arm.

Again, I will measure the differences between both systems. One system with factory rubber, and one system with spherical joints.

David
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#18
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QUOTE (firstgencrx @ Oct 31 2009, 06:34 PM) <{POST_SNAPBACK}>
Now that's an excellent idea Chris! Let me see what I can piece together. I'll mock this up on one side. Then I can just articulate the whole thing and get a real idea of what is really happening. What I'm hoping is that with the non-rubbery flexible temporary joints, I can compress and extend the front lower control arm and torsion bar arm assembly with little binding or effort. I'll leave the torsion bar in the assembly, but release it so it's just going for a ride. I'll try and do a test tomorrow.

I did take some twist angle measurements this afternoon on the side that is still mocked up in rubber. I installed a torsion bar into the system, and compressed the system under load so it was as real as possible. I took angle measurements with an electronic level that has a not so impressive accuracy of +/- 0.1 degrees. I adjusted the arm assembly from full drop, to full bump plus 2" of additional bump travel for the folks who run shortened bodied struts. The angle measurement was done right between the two bolts that hold the lower control arm to the torsion bar arm.

The torsion bar arm twisted between plus 1.9 degrees, and minus 1.9 degrees of twist. I hope that made sense. I set the level to read 90 degrees in the center of full travel. Below and above that position, the level read +/- 88.1 degrees at the extremes of travel. The arm also did not appear to be twisted in the center of travel.

I also pulled a straight string across the bottom of the front sub-frame, just over the torsion bar arms (remember, my car is upside down). I was trying to detect any bending of the torsion bar arms at the different positions. As you can imagine, the lower control arm swings so there is a sort of arc that makes tiny changes in both camber and caster as this assembly is compressed and released. The caster changes are what I'm interested in. The amount is so small, I couldn't really tell any differences just by looking at it with my eyes. I'll try and devise a better way to measure any bending that is happening to the torsion bar arm.

Again, I will measure the differences between both systems. One system with factory rubber, and one system with spherical joints.

David

Sounds good.
In addition, you might consider leaving the radial arm bushings off, but still have the radial arm connected to the tbar arm. That way you may be able to see how much the end of the radial arm translates as you move the tbar arm through the arc.

EDIT: Ok, I just realized that's what Chris was suggesting:
QUOTE
My guess is that if you were to fab up a quick bushing to hold the torque arm to purely rotational motion, you could check the resulting path at the other bushing location pretty easily.

...sorry, I'm slow.

#19
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QUOTE (kakabox @ Oct 31 2009, 10:24 PM) <{POST_SNAPBACK}>
Sounds good.
In addition, you might consider leaving the radial arm bushings off, but still have the radial arm connected to the tbar arm. That way you may be able to see how much the end of the radial arm translates as you move the tbar arm through the arc.

EDIT: Ok, I just realized that's what Chris was suggesting:

...sorry, I'm slow.


Will do Chief! laugh.gif

D.
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#20
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Interesting as always. My interest in this is not necessarily for the CRX but for my Mini build. For those of you that don't know I will be using the complete front suspension from the CRX in my 61 Mini conversion to Honda power! But I have the luxury of mounting the top of the strut wherever I deem fit and am not constrained by pre-existing mount points.

So my question to David is the following. If you get this to work properly can I remove the T-bars completely? This revolves around the fact that I could then use coil overs on the front and eliminate the T-pars completely or if necessary combine the two in some fashion. I'm basically asking if where the T-bar is located can it have an attachment that will only hold the arm in place? JS

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#21
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QUOTE (strudel @ Oct 31 2009, 11:32 PM) <{POST_SNAPBACK}>
Interesting as always. My interest in this is not necessarily for the CRX but for my Mini build. For those of you that don't know I will be using the complete front suspension from the CRX in my 61 Mini conversion to Honda power! But I have the luxury of mounting the top of the strut wherever I deem fit and am not constrained by pre-existing mount points.

So my question to David is the following. If you get this to work properly can I remove the T-bars completely? This revolves around the fact that I could then use coil overs on the front and eliminate the T-pars completely or if necessary combine the two in some fashion. I'm basically asking if where the T-bar is located can it have an attachment that will only hold the arm in place? JS


Technically you should be able to. The end of the original torsion bar arm will be attached to the front sub-frame through the spherical bearing. I'm planing on parts that are pressed together or bolted together. Some kind of safety system as insurance to keep the arm from coming out. But in your case, with no torsion bar, it would be easy to improve on that.

You need to think about using some kind of wheel with less positive offset. The knuckle is designed such that with a standard wheel offset, the strut body is very close to the tire. Once you wrap that strut with a spring, you might not have enough room between the tire and the spring.

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#22
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QUOTE (firstgencrx @ Oct 31 2009, 11:55 PM) <{POST_SNAPBACK}>
Technically you should be able to. The end of the original torsion bar arm will be attached to the front sub-frame through the spherical bearing. I'm planing on parts that are pressed together or bolted together. Some kind of safety system as insurance to keep the arm from coming out. But in your case, with no torsion bar, it would be easy to improve on that.

You need to think about using some kind of wheel with less positive offset. The knuckle is designed such that with a standard wheel offset, the strut body is very close to the tire. Once you wrap that strut with a spring, you might not have enough room between the tire and the spring.

David

I probably never thought of that but there are other ways to mount a coilover rather than the oem position.

But on reflection this is not a strut system so I may have to re-evaluate my thought process just a bit. By using the CRX suspension with this type of a coilover I still have to consider that the upper part of the mount has to be able to twist and in this orientation it may not work. See, I always get insight from you by asking the silly questions. Now find me a solution! wink.gif JS

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#23
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Jerry,

It's simple! tongue.gif

Send me your Mini, with the engine and trans you want to run, and I'll put it together for you. cool.gif

You consistently seem to have a thing for cantilever shock set-ups, so that would be a must. I would most likely fab-up something out of DOM and thin sheet for the frame and suspension.

Why is it again you don't live in Colorado?

David
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#24
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QUOTE
Why is it again you don't live in Colorado?

Because they keep losing kids in balloons in your neck of the woods! ohmy.gif OK, back on topic since I have digressed it somewhat. JS

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#25
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QUOTE (strudel @ Nov 1 2009, 10:59 AM) <{POST_SNAPBACK}>
Because they keep losing kids in balloons in your neck of the woods! ohmy.gif OK, back on topic since I have digressed it somewhat. JS


Very funny smarty pants. tongue.gif It's embarrassing to get phone calls from everyone we know asking about it. Even from out of the country! blink.gif laugh.gif

It's dying down now, finally. dry.gif
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#26
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OK, I did some testing based on Chris and J's comments. I was able to spend a few hours late last night working on this. And I got up early this morning (only because we got an extra hour of sleep last night! laugh.gif ), to finish the mock-up off. Here are my results.....

I made a temporary bushing for the torsion bar arm that would only allow it to pivot on the torsion bar axis. Managed to find a 2.5" diameter scrap piece of Delrin in my junk pile:




Turned it into a bushing (pun intended...) making sure the forward elevation of the arm was correct. Did this with a small step machined into the bushing:




Bushing press fits into the front of the sub-frame torsion bar tube:




Tap, tap, tap with a hammer and she's in. Perfect fit:




Torsion bar arm stem also inserted with a slight press fit. Rotates easy enough, but not enough clearance for the stem to rock in the bushing:




Now onto the rear stem of the lower control arm. I don't have my larger spherical bearings yet that I'll use in this location, but I have a smaller one I can use just for this mock-up. I machine a spherical bearing housing out of mild steel for this job. This is not the finished design, but it'll be close to something that I'll end up using. The spherical bearing housing is machined so it press fits into the back of the sub-frame rubber bushing pocket.

Back side of spherical bearing housing:




Front side of spherical bearing housing:




Trial tap it in with a hammer to see if the housing fits before pressing the spherical bearing in. It's a perfect press fit:




I made the decision to place the rear lower control arm spherical bearing as far back as possible. This will result in the least amount of caster change when the front suspension is compressed. You can just barely see the spherical bearing pressed into the housing behind the spacer sleeve in the image below.

Assembled with a spherical bearing installed, and the arm installed with stem spacers and a nut:




Next post continues this thread.......
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#27
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The first thing I noticed when I articulated the system is how smooth it is. There is no binding, and almost no effort to move the lower control arm at the ball joint up and down, even when I move the arm inches beyond the normal range of motion. I took some torsion bar twist angle measurements, and they're exactly the same as the side with the rubber bushings.

The torsion bar arm twists as we know, but it does it so easily, that you can't feel it. There is just enough friction in the slight press fit of the torsion bar arm stem into the Delrin bushing, that the assembly will "Stay" where you put it. It almost wants to drop from the weight of the arm. This is what I mean:

Arm positioned up (farther than normal travel):




Arm positioned down (again, farther than normal travel):




Top view of arm in down position:




Top view of arm in up position:




It really looks good to me. I can't see or feel any kind of binding or unwanted loading. No odd bending of the torsion bar arm or excessive twisting. It moves smooth as silk with almost no effort. You can adjust the assembly with the tip of your pinky.

Now, I did one more test. I removed the nut from the back of the lower control arm stem, and measured how far the stem would move axially in it's bushing when the lower control arm is moved into full bump and drop position. You can imagine that when the torsion bar arm is level, the stem is positioned the farthest rearward. Pushing the arm down and up, makes the stem move out of the bushing, or forward because the torsion bar arm pulls it out due to the fact it doesn't want to bend.

What I found is at full bump, the stem moves 0.020" forward. At full drop, the stem moves 0.18" forward. Less axial movement on the drop is probably because I move an extra 1.5" at full bump to compensate for shorter bodied struts. This make the distance between a level arm to full bump farther, than a level arm to full drop.

Well, that's it. I think something like this is going to rock. I can't find anything wrong with a setup like this.

I should see my new spherical bushings by the end of the week. At that time, I'll try and do some kind of post with the real bearings and their holders.

Take care all.

David
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#28
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What do you think about just leaving the Delrin bushing like you mocked up for the T-bar arm and just using a spherical for the control arm?

Seems like that would be the easiest to fabricate (gotta believe Delrin machines like butter) and also be the easiest way to make a conversion kit.

Or will the Delrin extrude out over time and get sloppy?
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This looks like a good project and one that would eliminate fwd/bkd movement of the lower control arm under hard acceleration. I can remember watching stock Civics with rubber bushings roaching the front tires coming out of sweeping corners and the unloaded wheel moving back and forth by several inches. Keep us posted. I would be interested in purchasing a completed set for my CSP/GP Civic.
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#30
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QUOTE (Greg Gauper @ Nov 1 2009, 03:48 PM) <{POST_SNAPBACK}>
What do you think about just leaving the Delrin bushing like you mocked up for the T-bar arm and just using a spherical for the control arm?

Seems like that would be the easiest to fabricate (gotta believe Delrin machines like butter) and also be the easiest way to make a conversion kit.

Or will the Delrin extrude out over time and get sloppy?


I knew it! laugh.gif Someone would ask that question. wink.gif I would love for it all to be that simple. smile.gif

As you see it, the bushing wouldn't last very long. The stem on the back of the torsion bar arm is something like 1.05" long. That's just not enough surface area for the loading it sees to last very long. A bronze bushing would do better, but that stuff in 2.5" in diameter solid bar is super expensive. If we make a sleeve that extended the length of the torsion bar arm stem to say 2" or even 2.5" long, then that might start to get closer to something that would hold up. I've already thought about pursuing a longer, and larger diameter stem. Something worth looking at.

A more robust retaining system would be needed with a bushing system. I wouldn't trust that wimpy little snap ring out on the end of the torsion bar to keep that arm in there. blink.gif

David

Just a note, the Delrin is about $25 to $30 per foot.
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