Hi Nicho, welcome to the site. I have sent you an email please contact me.
cheers

Steve 0427197267

As HK-T-G have the drag link assembly at the rear of the crossmember from factory, I would suggest that the preferred position of a rack would also be at the rear. The rack of choice would need to have the same dimension from inner tie rod end to inner tie rod end as the drag link has. The tie rod dimension will then also match the originals. Keeping those dimensions as factory was, will maintain the factory toe in/toe out around corners, the "ackerman principle"

Checkout this link for a simple demonstration.
http://www.davehaughey.ca/right_turn.gif

A front rack fitted to a front crossmember that was originally designed for a rear drag link system is virtually impossible to achieve the correct geometry.
A case in point is a HR crossmember utilising a front rack. I have one (not CRS) in an EH, 23 years now, and the geometry is incorrect. It toes in around a corner rather than toeing out. Dont believe people that tell you this is not the case. It is a fact. I built the car in the mid 80s, and still believe that front rack is simply a compromise to make a V8 conversion reasonably simple. Front racks on HR crossmembers are the easier option for a V8 conversion. Sump & exhaust clearances are the stumbling blocks for a rear mount rack with V8, particularly Chev. If this can be sorted, as guys have done, the rear rack is a far better option to achieve correct geometry.

The next point to consider is the height of the rack when fitted to the crossmember. As the control arms cycle up & down through the full suspension travel, the degree of steering, ideally, should not vary throughout this cycle of travel. At any degree of steering angle that the wheels are positioned in for this test, it should comply. If the rack is not at the correct height in relation the the steering arm & lower control arm position, the up & down cycle of travel will change the degree of wheel position. This will in effect, steer the car as the suspension goes up & down.
I suppose the only other point to consider is CRS & correct geometry, should they ever be used in the same sentence?

Utility8

Edited by user Saturday, 8 August 2009 2:09:15 AM(UTC)  | Reason: Not specified

Pinched from another forum.

Re: Steering Rack into HT-HG
UC Torana rack works well in front of the cross member. The width is good and bump steer is minimal. I had to knotch the cross member for the pinion shaft. I had to get tie rod adapters made as well. I used HQ steering arms to try and get the Akermans angle as close to correct. If you reverse the stock arms it is way out.

Castlemaine Rodshop make a kit that uses a Commodore rack behind the cross member. I prefer the front mount because the rear mount is a long way behind the x-member and limits sump size.

Re: Steering Rack into HT-HG
I had to cut into the outrigger. I bolted a plate to strenghten it after the rack was mounted. This is my old car. It was in Extreme Magazine last year. The photo shows it pretty well.

Edited by user Saturday, 8 August 2009 8:28:11 AM(UTC)  | Reason: Not specified

I found this on a simple Google search. Probably the easiest explanation I have seen.
If this doesnt make sense, its probably not worth trying to understand steering geometry, let alone re designing it.
If you follow how it works, then consider using a front rack on a frontend designed for a rear link assembly, such as a HR unit.
The outer tie rod ends will need to be where the front tyres are. Can that be done?
No, it cant.

Images 3 & 4 are typical of the problems created by a rack mounted to the front of a HR front crossmember. (HK-T-G are in the same boat)
Image 3 is what you have with a front mount rack.
Image 4 is what you get when trying to steer.
Image 5 is what you are unable to achieve as the front tyres are in the way.

As I said in my previous post, I have a HR cross member in an EH with a front rack. 23 years of it. It is a compromise at best. The geometry is not right & really, with what I now know, should this design of steering modification be able to be legally registered?

This information below was sourced from the following link. http://www.nationaltbuck...is/ackerman/Ackerman.asp



ACKERMAN STEERING

Maybe this will help some of you guys to understand the Ackerman principle and how it affects T-Buckets. The basic theory is that the front wheels of a 2 wheel steer vehicle with the steering on the front should remain tangent to the turning circles of each individual wheel. It is theorized that the center point of these circles falls on a line that is the same as the centerline of the rear axle housing projected out into space. The center of the both arcs is at the same point on the rear axle centerline. That centerpoint slides along that line as the amount of steering input is changed. In other words, on a small amount of turn the centerpoint is way out there, in a hard turn the center is closer to the car. In the straight-ahead position the centerpoint is at infinity. Thats way, way, way out there! Its time for a little drawing to keep from confusing you with this attempt at an explanation.



As you can see, the left wheel turns on a shorter radius circle and needs to turn sharper than the right wheel to remain tangent to its turning circle. Why do these wheels need to stay tangent? That places the least amount of side loading on the tires and suspension components. In other words tire and parts wear is going to be minimized. How do we get the geometry such that this desired effect is achieved? Fortunately Mr. Ackerman came along and figured out that if he arranged the mechanical parts of the steering system so that the pivot points of the linkage (tie rod) that connected the two front wheels were closer than the pivot points for the front wheel mounting assembly (spindles with their kingpins), it would affect how the wheels reacted when turning was occurring. He apparently noticed that if he made these points such that if you drew a line from the center of the kingpin to the center of the rear axle housing and placed the tie rod ends center on that line, it would give the desired change in the angles that the two wheels turned. Old Mr. Ackerman found that he had a principle that applied universally. I bet he was pretty proud!



Time for another illustration. O.K., automobiles steered fine and everyone was happy. And along comes Joe Hot Rod and he decides that his heap needs to be nice and low. Hey, no problem. Lets move the spring back behind the axle and down nice and low. Looks great, in da weeds! Oops, small problem, no place for the tie rod to run back there. Imagine that you can see a "great idea" light bulb over Joes head. Hey thats easy, just swap the spindles side for side and put the tie rod on the front. Look, the wheels still are connected and turn when you give the steering wheel a twist. That will cure all of my problems.



Well not quite Joe. You have just wiped out Mr. Ackermans principle. Your tie rod attachment points (tie rod end or heim joint) no longer fall on that imaginary line. So what happens now? Well, either the inside wheel does what it is supposed to do, or the outside wheel behaves correctly, but not both at the same time. So now old Joe has that nice set of new high dollar tires grinding themselves up on the local asphalt every time he goes around a corner. The car also has a tendency to get a little quirky because the wheels cant make up their minds which one is going to be in charge of where they are going to point.



Is old Joe just screwed on this deal now, stuck with this problem? Nope! He just needs to get those pesky attachment points back over on Mr. Ackermans imaginary line. It works just as well on a front mounted tie rod as a rear mounted one. Remember, Mr. Ackerman found out that it was universal. It depends on what he has for front-end hardware as to what he can do to correct this situation. Early Ford spindles with the built on steering arms can be heated and bent to get back out there where they should be. Just be darn careful doing it; if you dont know what youre doing find someone who does and have them do it. The aftermarket offers some parts that can take care of this problem. Sometimes special design parts will need to be made. A lot depends on the individual situation. Brake configurations (calipers and rotors mostly) can create some interesting obstacles. If you cant get out there where Mr. Ackerman says you should be, at least get as close as you can.



Lo and behold, old Joe made the changes and guess what? His lo and in da weeds bucket is cruising along lifes highway is fine style. Tire life is improved, steering is less quirky (still needs a little work on the bumpsteer deal) and he is all smiles.



Well, old Joe is not alone on this deal, hes got lots of buddies with the same problem and they havent done a thing about it. So what happens? Well they just go cruising alongof course they stop by the tire store a little more often than Joe and leave some of their hard earned. And they have to pay a little closer attention to where their missile is headed when all of the guys are out for a cruise and find that great little road with all of the curves that just beg for a guy to open it up just a tad.a tad? Yah right!

By George Barnes

Edited by user Saturday, 8 August 2009 9:35:08 AM(UTC)  | Reason: Not specified

Im afraid I dont totaly agree with Mr Ackermans theory...But then again I think the moon landing was fake!

"We are but a grain of sand on the beach of life"

quote:

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Originally posted by Utility8

Im confused GTS308.
Why would you try & get the Akermans angle as close to correct when I dont totaly agree with Mr Ackermans theory?

Utility8

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As I stated in the post I found that posted on another forum and just pasted it in...It aint my car or idea!

But getting back to the Ackerman linkage principle. Clearly this is beneficial at low speeds when your taking your car out shopping as the tendency to scrub the tyres is greatly reduced or even eliminated. However, at higher speeds and greater loadings this does not necessarily follow.

In a high speed corner, weight is transferred to the outer wheel thus a increasing the loading and therefore requiring a greater slip angle. It is, therefore, not uncommon for cars to employ a certain amount of "anti Ackerman". After all its tire slip angles that influence the actual turning radius.


"We are but a grain of sand on the beach of life"

Try www.rodsracks.com.au,they are in SE QLD.