2nd gen camaro and howe centerlink

[speedjohnston]

Just to keep this out of Brians build thread, I was going to use the stock centerlink and the Howe idler and pitman arms with there tie rod ends. the centerlink you can see is sitting a little funny when the wheels are pointed straight and wasn't going to work.
http://i175.photobucket.com/albums/w136/speedjohnston/DSC01183.jpg
I switched to the Howe centerlink and cut the front off the crossmember (still needs to have a plate welded on) and the centerlink sits very square with the engine now. My cut needs to be grinded a little.
http://i175.photobucket.com/albums/w136/speedjohnston/DSC01196.jpg
My question has to do with the Ackerman. The car is built for the street and high speed road racing, so the Ackerman under racing conditions if its not crazy will have little effect (debateably). I had the cars front wheels raised and turned the steering side to side and took some measurements. I realize this is not the most accurate method but for some using the centerlink the ackerman issue seemed obvious, but I seem to have very little difference one way or the other. This could be because of the pitman arm and idler I am using? How obvious is it when its out? Just looking for opinions while I finish figuring out the front suspension.

[pro-tour79]

using the Howe pitman arm is what caused the issue in the first place , it is like a Firebird pitman arm shorter and bent down, a Camaro used a straight flat longer pitman arm, but the Howe center link is made to work with that pitman arm.

[speedjohnston]

So is the ackerman issue only of concern when you mix the stock parts with the Howe parts?

[mfain]

You might want to look at Bob Bolles suspension article in the Feb 2010 Circle Track. He, and most others, now recommend zero or very near zero Ackerman. If you employ Ackermann at all, it will be in fractions of a degree, not whole degrees. The article briefly describes how to check the Ackermann. The old Woodward catalog used to have a good tech section on how to adjust Ackermann. It was related to rack placement, but the principle is the same for drag link suspensions. Moving the inboard tie rod static mounting positions (i.e. moving the rack or the drag link) forward will induce more Ackermann -- moving it aft will have the opposite effect. This movement can be done by moving both the steering box and idler arm mounts fore or aft, as required; using a differently shaped drag link that moves the tie rod mounting points fore or aft; or using different length steering arms (longer steering arms have the same effect on Ackermann as moving the rack or drag length aft). I assume that your Howe drag link was made for your chassis using the steering arm lengths you have, so you should already be in the ball park. Your car looks great -- best of luck with the build.

[mfain]

Another thought -- it is hard to tell looking at the photos, but it appears that your idler arm is longer than the pitman arm. If that is the case, the two outboard tie rod end mounting points will swing in slightly different arcs, which will make the Ackermann different when turning in one direction vice the other. For visualization, I have had good luck making scale models of the steering componenets (1/2 or 1/4 scale works) out of poster board and pinning them together at the pivot points with thumb tacks. Thumb tack the "fixed" points like the pitman arm, idler arm, and ball joint centerlines to a piece of wood (in appropriate scaled positions). You can then turn the wheels back and forth and measure each wheel's turn angle with a protractor. Its not super precise, but it will let you see what is happening to the Ackermann. You could also just draw it out on graph paper. Here is a quote from the Woodward catalog that may shed some light on your situation. You can replace the words "rack and pinion" with "drag link". "On frames based on the 1971 Camero, it was impossible to locate a rack and pinion far enough to the rear, so it became common to fabricate spindles with a shorter steering arm on the left side, and give a faster steering ratio to the left wheel." This was obviously to help a circle track car with left turn entry, but it gave toe in (negative Ackermann) if you turn right. Having different Pitman Arm/Idler Arm lengths will have the same effect to some degree. Just food for thought -- hope this helps.

Pappy

[speedjohnston]

Thanks for the replys, that deffinately gives me some ideas on how to check it. I will also look for that Bob bolles article. What I originaly tried to do was turn the wheel all the way in one direction untill it stopped on the lower a-arm, then measured tire to tire. Then I did it the other way and took the same measurement. I was hoping if there was a difference right to left I would find the measurement would change if the ackermann changed. It seemed to be within a 16th of an inch, but I just checked quickly since I didn't even know if this would tell me anything at all. I had all these other little issues along the way, I didn't even think about this untill it was mentioned last night in another thread. Thanks again for the help. :cheers:

[Cris@JCG]

I have a 70 Camaro that I am building for myself.. Please give me some more details about this front suspension!! Are those ATS spindles?? They look like the have extenders on them.. A-arms??? Details please!! I like this setup :thumbsup:

[speedjohnston]

They are the ATS AFX spindles, the a-arms are SPC with a tall Howe ball joint. I purchased and got help with this set up from Mark Savitske at SC&C.

[Cris@JCG]

Thank you!

They are the ATS AFX spindles, the a-arms are SPC with a tall Howe ball joint. I purchased and got help with this set up from Mark Savitske at SC&C.

[David Pozzi]

GM used 3 different hole spacings on the idler arm during the 70's. The 3rd gen Camaros have slots for the idler arm making it somewhat adjustable for height. If all else is OK on your steering, I'd consider redrilling the idler arm holes, or slotting them to get the center link level.
David

[speedjohnston]

GM used 3 different hole spacings on the idler arm during the 70's. The 3rd gen Camaros have slots for the idler arm making it somewhat adjustable for height. If all else is OK on your steering, I'd consider redrilling the idler arm holes, or slotting them to get the center link level.
David

The Howe idler arm I am using is completely adjustable for height and moves up and down quite a bit. The centerlink is also adjustable for height. Thats part of the reason I wanted to stick with the Howe centerlink and idler arms was for the adjustability. Its just loosely bolted together right now and will be adjusted after I weld in the adjustable spring cups. You can see how it (the idler arm) threads up and down better in this picture and then you tighten the set screw.
http://i175.photobucket.com/albums/w136/speedjohnston/DSC01254.jpg

[WSSix]

why is there not a build thread on this car? I searched for your screen name and unless I screwed that up, I'm not seeing one. You have me drooling all over myself with just these three pictures. Don't be a tease:lol:

[Cris@JCG]

I X2 on the thread build! Where is it??? This is looking like it is going to be a wicked ride :thumbsup:

[deuce_454]

DAMN that's a serious 2.nd gen camaro.... and how far is that engine moved back?? 14 inches??? its a front/center motor car... figures Marcus would have a hand in a car like that!

and please post some pics.. what are you doung to fit all that rubber in the front fenders? flares??

[70rs]

I have been asking for a build thread too. You have a fan club here. We really need more info on your car.....:yes: :cheers:

[tones2SS]

Car looks great. So doesn't the center link. We need a build thread on that bad boy please. Looks like a killer car!:thumbsup:
Looks like you are running a Pro-Charger?

[thedude327]

Steve,

You need a build thread for this project..............Oh and looks like you were not kidding about that top speed either. Those parts look very purpose built for performance. Nice work !!! :thumbsup:

Paul

[speedjohnston]

Thanks for the kind words. Its been a long process. The car has been apart for 4 years and is finally looking like a car again so I hadn't bothered doing a build thread with such a long time between any updates. Sometime over the holidays maybe I'll start one.
As for the supercharger, it is a prochrger F2, and the motor is set back quite a bit, probably about 10-11inches. The front of the car does have flares to cover all that rubber without affecting the turning radius.
I'll post a pic I took on friday. It still has its 'old school' paint job done a dozen years ago. I'll get it painted when the car is complete.

http://i175.photobucket.com/albums/w136/speedjohnston/DSC01264.jpg

[Cris@JCG]

Just get it assembled & running & start blasting this thing down the track :thumbsup: This car looks tough!


Thanks for the kind words. Its been a long process. The car has been apart for 4 years and is finally looking like a car again so I hadn't bothered doing a build thread with such a long time between any updates. Sometime over the holidays maybe I'll start one.
As for the supercharger, it is a prochrger F2, and the motor is set back quite a bit, probably about 10-11inches. The front of the car does have flares to cover all that rubber without affecting the turning radius.
I'll post a pic I took on friday. It still has its 'old school' paint job done a dozen years ago. I'll get it painted when the car is complete.

http://i175.photobucket.com/albums/w136/speedjohnston/DSC01264.jpg

[tones2SS]

Thanks for the kind words. Its been a long process. The car has been apart for 4 years and is finally looking like a car again so I hadn't bothered doing a build thread with such a long time between any updates. Sometime over the holidays maybe I'll start one.
As for the supercharger, it is a prochrger F2, and the motor is set back quite a bit, probably about 10-11inches. The front of the car does have flares to cover all that rubber without affecting the turning radius.
I'll post a pic I took on friday. It still has its 'old school' paint job done a dozen years ago. I'll get it painted when the car is complete.

http://i175.photobucket.com/albums/w136/speedjohnston/DSC01264.jpg

Very nice. Do you have any idea on horsepower/torque numbers?
That is going to be a kick ass car!!:thumbsup: :hail:

[WILWAXU]

Wow! That's a killer looking ride! :thumbsup:

[WSSix]

Love it! I'm going to have to see the panels all put back on before I comment on the paint fully but it doesn't look bad so far in all honesty. Old design or not.

[speedjohnston]

Very nice. Do you have any idea on horsepower/torque numbers?
That is going to be a kick ass car!!:thumbsup: :hail:

Yes I do, and its kinda stupid. :lol:

[mfain]

A couple of quick questions (not as sensitive as "horsepower?"). How "big" is the motor (cubic inches) and what are you planning on the car weighing? Again, that is a great looking project that appeals to the no-nonsense, high performance, semi-streetable crowd.

[tones2SS]

Yes I do, and its kinda stupid. :lol:

lol!!!!:lol: :willy: VERY NICE!:bow:
Is it a secret for now?:_paranoid

[speedjohnston]

A couple of quick questions (not as sensitive as "horsepower?"). How "big" is the motor (cubic inches) and what are you planning on the car weighing? Again, that is a great looking project that appeals to the no-nonsense, high performance, semi-streetable crowd.

Its a 581ci and the car with the nose, intercooler and doors on plus everything in the pic, but no transmission, rad, fuel tank wiring or any plumbing weighed just over 2600lbs. I'm sure it will be over 3000 in street trim because it will have a large fuel cell, big rad or rads etc. I can't see me adding a 1000lbs to so I would guess 3200ish?
And no the horsepower isn't a secret. I should save something if I do a build thread or we'll have to move this one into that section. ;)

[tones2SS]

Any updates?:thumbsup:

[70rs]

Any updates?:thumbsup:

I was just thinking the same thing Tony. I really want to see more on this car. I vote for a build thread. ASAP.:yes: :D

[speedjohnston]

I will start a build thread in the next couple weeks.... I think, maybe lol

[tones2SS]

I will start a build thread in the next couple weeks.... I think, maybe lol

With a build like this, you have to!!! lol:_paranoid :unibrow:
Looks like a killer project.:cheers:

[Mean 69]

You might want to look at Bob Bolles suspension article in the Feb 2010 Circle Track. He, and most others, now recommend zero or very near zero Ackerman. If you employ Ackermann at all, it will be in fractions of a degree, not whole degrees.

I'd be a little cautious with this as a general statement. What is good for a circle track car might not be good for a road race car, and typically, this is indeed the case. Ideally, adjustable Ackerman would be the best so one could alter dynamically to see the effects. I recall reading Carroll Smith's book, engineer to win, and he had the opposite comment on Ackerman that was derived in real world testing (open wheel car, road race....). For decades, the thought was that Ackerman wasn't a big deal, due to loading of the inside tire on turns (small) and therefore the anticipated effect was negligible. Turned out not to be the case after a few decades of assuming this, increasing Ackerman in particular helped intial turn-in, etc.

I too have the short Pitman arm and Howe link, and the measurements I took a few years back were all over the map left to right, independent of Ackerman (which in turn would be all over the map too as a result!). With Brian's work straightening the drag link out, using a stock style Pitman, it seems that this might work after all. I like the outer tie rods you are using with the adjustment threaded adjustments, and have thought about using them on the inners as well (space permitting) in order to facilitate adjustable Ackerman, assuming the left-right stuff gets sorted!

Then there's bump steer.... "ASSuming" the design of the Howe link to adjust bump really works......

With a rat motor and additional weight over the nose of an already nose-heavy car, I'd think long and hard about the steering...... By the way, I agree with the gallery, that is one cool looking machine. Have you measured scrub radius using the ATS spindles? Lots of tire on that car (mine will ahve the same....), you steering gear might not be too happy if it has to fight scrub.....

Mark

[speedjohnston]

I too have the short Pitman arm and Howe link, and the measurements I took a few years back were all over the map left to right, independent of Ackerman (which in turn would be all over the map too as a result!). With Brian's work straightening the drag link out, using a stock style Pitman, it seems that this might work after all. I like the outer tie rods you are using with the adjustment threaded adjustments, and have thought about using them on the inners as well (space permitting) in order to facilitate adjustable Ackerman, assuming the left-right stuff gets sorted!

Then there's bump steer.... "ASSuming" the design of the Howe link to adjust bump really works......

With a rat motor and additional weight over the nose of an already nose-heavy car, I'd think long and hard about the steering...... By the way, I agree with the gallery, that is one cool looking machine. Have you measured scrub radius using the ATS spindles? Lots of tire on that car (mine will ahve the same....), you steering gear might not be too happy if it has to fight scrub.....

Mark

Thanks for your input Mark.
I talked to some guys that specialize in race car alignments and they told me the Howe center link, tie rod end adjusting and adjustable idler arm will make the bumpsteer relatively quick and easy. They have used it many times before.
I have been doing lots of research and had lots of help from Mark Savitske over the phone. When the car is finished and has all the weight in it, it will go to a proper race car alignment shop and have it done properly before I start making any changes to it. Between there experience and me learning as much about what I need for this specific car, I think we can make it work well. If the ackermann becomes an issue, at least we know where to start for a fix.
I would say roughly scrub radius would be about 2 1/2 inches maybe more... I can measure it more accurately if you wanted to know for yourself if you plan on using those spindles. I put a very safe fitting offset in the wheels knowing I can change the inner and outer shells after to move things around. I can also add an inch or so to the wheel width. The plan was to use these tires for some initial testing and fine tune from there.
Hopefully the nose weight won't be as high as it would have been, with my engine set back so far. It looks closer to the front then it is because of the blower belt. I'll be working hard to balance it out as well as I can, but I have been thinking a lot about steering, thats why I have my crazy questions.
All the input is greatly appreciated, it makes my brain work harder. :)

[lhkustoms]

we need a build thread that is an awesome car! we need some details :thumbsup:

[mfain]

I joined this website for one reason -- great dialog from smart people on the one thing that is important here -- lateral g. Mark makes some excellent points regarding Ackerman, especially regarding "adjustability". Ackerman is very vehicle and use dependant, and is therefore dependant on dynamic, not static situations. Ackerman is slow to build (needs lot of wheel turn to be significant), so it is generally more useful for slow speed, high steering angle turns such as in autocross or high wheel angle turns that dirt sprint cars employ. It is less of a player in low steering angle, high speed turns -- like a 160 mph sweeper -- especially with today's tire technology. Carroll Smith's "Tune to Win" was published in 1978 (I can barely spell bias ply). His follow-on publication, "Engineer in Your Pocket", 1998, makes no mention of Ackerman as a tuning tool. Today's tires, especially race tires, operate at very high slip angles that tend to mask small Ackerman effects (at high speed/high g). Positive scrub radius can produce the same effect as pro-Ackerman -- increased "drag" on the inside tire promoting turn-in. Of note, dynamically, scrub radius of the heavily loaded (and deflecting) outside tire in a turn decreases while the inside tire's scrub radius increases as the effective center of the contact patches move laterally. Running zero scrub radius could actually give you negative scrub under heavy loading. As Mark points out, the better balanced your car is and the more the inside tire is contributing to the turn, the more this dynamic is altered. I guess my point is that there is no one textbook answer that applies across the board. Each vehicle's suspension characteristics are generally unique and a balance of compromises, and it takes real word testing and "adjustments" to optimize them for the particualr dynamics to which the vehicle is exposed. Just an opinion, and food for thought.

Pappy

[Mean 69]

Very nice, Pappy! I like the threads that address things that make me think, so this is one that I like a lot!

Carroll mentioned the Ackerman "thing" in the book called Engineer to Win, which was the last of his three main books (Prepare, Tune and Engineer to Win). I don't have the "Engineer in your Pocket" book, I'll have to grab a copy because I have mearned a lot from all of his books, as well as many others by other smart folks. As you implied, no one answer, many opinions and strategies on any given theme. That's what makes it so interesting.

Agreed on the low speed implied "benefit" of the Ackerman, at higher speeds/smaller turn angles it won't be nearly as noticeable, unfortunately I don't have enough time or money to live most of my life in a pure race car on fast tracks, so this is an important aspect for my current cars which I drive on the street and limited track time. I am really glad that others are working this steering issue on the second gens, I am pretty confident I could "solve" the issue, but I just don't have the time so stealing shamelessly from other smart folks before is a fine strategy as well! We all learn faster together.

I am not too concerned about the scrub radius for my own second gen using the ATS spindles, I have a set of these that I am currently installing on my 69 convert and compared to the factory second gen setup. No question it will increase scrub, so that's not a direction I personally want to go with my own project, as I am going to run a lot of rubber up front and wish to keep it lower rather than higher. If it comes out at 2 1/2 inches, that doesn't seem too bad to me at all, maybe a little higher than I'd start a paper design after but not as bad as I thought it would be. I am a glutten for punishment sometimes, and I am jones'n to make my own spindles, and probably will for this car....

Great work and input guys, thanks a million!
Mark

[mfain]

Mark,

Thanks for the kind words. Measurement info for you and Speedjohnston -- I have ATS spindles on my car (C4 Vette lower control arms and Lefthander uppers w/roller bearings and Torrington thrust bearings. At 13 inches below the hub center (the radius of a 26 inch tire), the scrub radius from the spindle ball joint line (looks to be about an 8 degree kingpin inclination angle) to the wheel mounting flange is 2.875 inch. I am running a 10.5 in. wide wheel with 6 in. backspacing, which gives a tire scrub radius of 2.125 in.

Pappy

[Mean 69]

Pictures of said car, please.... And yes, I believe the KPI is 8 degrees for those spindles if my (failing) memory serves me.

Cheers,
Mark

[mfain]

Mark,

Don't want to hijack Speedjohnston's thread. The link below has some pictures. I will take pictures of the front suspension for a project update.

Pappy


http://www.lateral-g.net/forums/showthread.php4?t=20865&page=3