Well.......
I managed to get a little done. Removed the gas tank, halfshafts, shocks, and that pesky leaf spring. Four bolts hold the leafs in place, mounted to the diff cover. First I removed the two rearward bolts, then I figured with the two front bolts loose. Figured I could remove one front and I can rock the spring out. Which worked very well BUT! Those two forward holes go all the way through the cover into the interior, gear lube all over, ouch!  Thank goodness I had just saved a bunch of old under ware for rags. Weighed the spring assy, 30 lbs. on the head, good bye.......

Also noticed in what are called the yoke mounts. halfshaft mounts. I noticed a seemingly large amount of play, app 030. to.050. Specs I have read should be app .009. Looking for options.

Edited and moved

I'll make my own. I'm not sure what material I will use yet however.

No, and yes. If your inner LCA pivot point is parallel to your hub pivot you will get no toe. But if you raise the front point and lower the rear point of the hub mount in relation to the inner LCA mount you will get toe/steer. The more you raise and lower these points  the greater the toe/steer. It will change the moment of arc between the front of the arm/hub and the rear of the arm/hub.

Imagine a loose loewer control arm and hub attached.The hub bolt is inclined at say 5 degrees and also say the front bolt (pivot) is 1" higher than the rear. Take the LCA and raise it straight up all the way 90 degrees keeping the hub in it's original plain parallel to the ground.  Now how would the hub be oriented? It will be angled in 1" at the front right? Then if you could  lower the LCA down 90 degrees the hub would be inward at the rear 1". Your hubs are are turning through suspension travel steering the rear of the car creating toe/steer.

Now my thinking is if you were to just angle a parallel LCA back. You will get increased wheel base during jounce and a bit of anti squat.

Last edited by Ralphy (7/02/2011 6:45 am)

Yeah, me too. But I think maybe you've got something there Ralphy. I'd like to help with it if I can just understand what's going on, but I'll probably have to mock something up before I can do any good with it. I'm sort of visually oriented that way.

Anyway, the Roadmaster will be done in about a month to the point where we should be able to start driving it and see how it behaves. My car has the same setup so if I make new LCAs they'll go on my car first. But I won't be able to do anything on the LCAs until probably spring. Have to get the car driveable first and there's lots to do.

JB

What sort of pics are you looking for?

JB

I would too. For my application I believe a new upright with a narrow modern cartridge bearing and a compact CV or other outer joint might allow the tires to fit under the stock fenders and still get the uprights outside of the frame rails for maximum lowering and/or suspension travel. At the same time an alloy LCA and tubular half shaft would greatly reduce the weight. With good reasons for those many changes it only makes sense to look at geometry changes at the same time. But I'm quite a ways away yet from understanding the pros and cons of the various changes that can be made. Pictures would probably help.

JB

The force is generated where the tire meets the road. Leverage pulls forward here (tire/road), pulling the LCA forward. If the LCA is mounted higher at the front \ the force equals an angle 90 degrees plus the added angle. Acceleration wants to raise the chassis, deceleration lowers the chassis. Overlooked is what happens if you have an UCA. The forces pull opposite on the UCA. So if you have two forward links as a C4 Corvette, on acceleration the  lower link is pushed and the upper is pulled. When decelerating the lower link is pulled back and the upper is pushed forward.

As to the toe steer it is very very little. Maybe a max of .3 degrees at 2" travel.  If you watch NASCAR if you see a car riding the white line have you noticed the rear tires tracking outside the fronts? Maybe 2"! I think the idea is to keep the front/rear on the same path a bit more. Remove any oversteer. Toeing out as the C3 Corvette is not good. You turn onto a entrance ramp to a freeway and stomp on it i the turn. The rear oversteers the whole car, then you spin! NASCAR actually bends a solid axle housing ever so slightly to get the right toe.

See how the rear is out?


Today look how much straighter they run.

Last edited by Ralphy (8/25/2011 11:06 am)

Jim Blackwood wrote:

As for the toe-steer, what you are saying is that it is desirable for the loaded wheel (outside) to turn in and for the unloaded wheel (inside) to turn out? Thereby causing an increase in toe-in to be induced by body roll, but wouldn't this also cause the toe to be all over the map on normal suspension movements? Sort of like an intentionally induced bump steer at the rear.  I'm not really sure I see this as a good thing. Sorry about that Ralphy, it's just the conclusions I've reached after thinking about it for awhile. Where have I gone off track?

JB

I came to the same conclusion and said basically the same thing in another thread

Daze wrote:

so correct me if I am wrong... as I often am but is the "rear steer" nothing more than built in bump steer???  and being built in the wheels react is a specific way given cretin suspension travel??  If that is the case I can see how that would vastly improve cornering, BUT would it not be problematic on bumpy roads when attempting to go straight??  Not trying to be critical at all, just trying to fully rap my head around it.  From my point of view everything in life is a trade off and I am just trying to see the trade off in this particular situation.  If I have totally missed the point pleas educate me

Since then however I have thought about it a lot.  I have researched it some and rear steer has been a common part of MOST IRS designs since Arning invented it so I am beginning to believe that the prows must outweigh the cons.  Also my biggest hang up was I kept comparing it to bumpsteer, And I don't think we can do that because as Ralphy said the amount of toe in is minimal so it would not be nearly as aggressive as what you see with typical bumpsteer in the front.  Which brings me to another point, front steering and rear steering are two different things.  Ever try to push a welding cart or shopping cart backwards with fixed caster at the front and swivel casters at the rear??  When things are set up that way it takes a lot of steering from the back half to get much steering in the front.  I can assume the the same would be true in the situation of our cars where the front is doing 90% of the steering and the rear steer is just a helper.

Here is another thought what if the rear steer was more about controlling suspension movement???  Think about it this way the rear tires are going to try to stay in line with the fronts so if the fronts are cornering the back tires will attempt to corner as well and that force that is turning the rear tire should be translated in to the suspension moving toward the position that would induce the same tire positioning.  same would be true when going strait the tires will try and remain in a forward position and will try and get back to that forward position after going over something that caused suspension travel which should in theory improve suspension reaction times and be some what self correcting.  thoughts???

I love thinking things like this out.  As I was comparing rear steer to bumpsteer the paragraph above just came to me and the more I thought it through the more it made sense.  what do you think??

I just figured the early NASCAR racers were hanging the tail out just a little. Maybe I was giving them too much credit, I just allowed as how maybe that was  the point at which the tires were just starting to slip sideways a bit. They were real ballsy guys you know.  ;-)

I'm getting a little confused here. If the suspension compresses it toes in and if the suspension droops it toes out right? The end result is that the rear end goes to the inside of the turn? How much change in the mounting points does it take to get that sort of action out of the Jag IRS? Can you just move one point and get the toe-in/out and also the anti-squat?

Then what happens when you hit the brakes? They are inboard, but the wheel is now trying to move backwards. If it's set up to counter squat on accel by creating a jacking force then wouldn't that tend to lift the wheels when braking? I realize this keeps the tail down but is the net result more or less braking force?

JB

1. NASCAR is still hanging it out, you just don't see it.
2. Paragraph 2, YES and YES.
Then anti- squat is typically done with the lower forward link angled upward. However KLM250 says his LCA's are angled back and I think it is seen in a pic of his. Trying to explain the toe is hard, if you have two links parallel free links I I = // or \\  you will get no variation if you move one end. But if you set them up like this \ I one link moves at a different arc in relation to the other. Even further if you set both like this \  / you will get even more change. My point of showing you this last one \  / is that is similar to the mounting points of the Jag  dogbone.

Now braking or anti-dive, when you accelerate 100% of the force comes from the rear wheels providing anti-squat. But when you brake approximately 35% of the braking force comes from the rear wheels. So the amount the rear will stay down is minimal. Your wheels should not be leaving the pavement, but the anti-dive should help hold the rear down and the anti-dive on the front should hold the front up. Reducing weight transfer to the front during braking.

Last edited by Ralphy (8/25/2011 4:40 pm)

Ralphy wrote:

Daze nothing would hit!

sure it would if you look at the pictures of Arning set up the LCA parts are centered on the diff and would be trying to occupy the same real estate as the rotor.

oh, I didn't realize you were departing that far from the arning design.  what did you think of my "improved suspension response time" theory???

OK, let's go another direction. Back to Arning, why does the pivot point have to be centered? Can't they be fore or aft of center?

Day that's frikin funny!

Again why does the pivot point need to be centered? I don't think it does!

Last edited by Ralphy (8/25/2011 5:12 pm)