Scratch builders

[Alex Evonosky]

Sharp 424
Actually you bring up a very good point, I like the tie rods to on top but when I was designing and thinking, look to me like the input shaft to the rack would be just about into the 1 1/2 " tubing cross member. I actually used the Flaming River rack with the 4" input shaft but had to exchange it for the short input so the swivle would be a lower to pass under the cross brace. It was quite a challenge as you know to keep everything in line as not to be too far off on bump steer and wheel camber when turning.
Screw in ball joints, yes, the same ones Pole Pos uses and yea, NAPA.
Good idea on the exploder rear. If I wasn't looking for a IRS quick change, I would take your advice and check that out.

[Three Peaks]

Is there really any advantage to the Flaming River OE type rack? I looked at that unit and the ATSCO 6804 unit at Autozone which I've heard good things about.
Only difference I can see is that the Flaming River unit is around $400 and the ATSCO unit is around $125.
Is the Flaming river unit a different style or length that makes it a better unit to use? I haven't purchased my R&P yet, so this question is pretty timely for me.
In fact, I have the Cobra Restorers R&P mounting brackets. Will these work for either of the units mentioned, or am I going to need to buy a different unit, or change my mounts for the ATSCO unit? Is anyone familiar with this?

Thanks, Bob

[mickmate]

Alex, you have the MII rack, Robert is talking about the MGB short shaft Flaming River rack at 24.9" between tie rod inners I believe. That was originally what they used made as a new one by FR. You guys had better cut it out, a bloke has to have time to work on it and sleep so he can dream geometry!!

[Alex Evonosky]

Mickmate
The rack I have from FR is about 24.9 between pivots.
The original rack mounts differently.
All I know is the FR rack is light and tight. Actually only about 275.00 I think. Non power.

BTW my BS is about 1/8th " or less over a total of 6" If you are interested. That was a rough check with a tape not dial indicator.

[Three Peaks]

Doesn't the original rack use U-bolts to mount? I think I passed up a great deal on a rack at a swap meet a couple months ago because I wasn't sure how it was supposed to mount. I hadn't received my frame yet at that point.

Alex, how does your rack mount and how difficult is it to make the new mounting brackets?

Thanks, Bob

[mickmate]

I've attached a pic of the brackets per CR prints with a mock up rack from an MGB. You'll notice I put the 5/8" "spacers" under it as they did originally to position the rack correctly. I read the tie rods should line up parallel to the lower a-arm looking at it from the front/back and the top. I have a good bump steer article from American Rodder by Wayne Scraba on original Cobras.

[Three Peaks]

Nick,
Where does a guy get these brackets? I didn't see them on the CR prints. Do they come with the R&P or can they be sourced somewhere?
What did you use for spacers? I was thinking of turning some delrin bushings to take up the space?

Thanks for the pic.- Bob

[mickmate]

Hey Bob, I'll have to check the part number on my prints. I can scan the drawing of that part for you if you need it. We can also have them CNC punched or laser cut if there is enough demand for things like this. I'd be interested in some pics of your frame to see what you actually have. My rack is just being tried in position with a few washers at the moment, I'll make some aluminium spacers when their length has been confirmed. I wouldn't mount a rack with anything less than solid metal spacers. If it can flex at all it will affect steering geometry.

[Three Peaks]

I'll see if I can get some pics of my mounting brackets and whatever might be interesting.

Thanks, Bob

[Alex Evonosky]

Bob,
Here are a few pictures of the original R&P mount with the spacers, the way it was in the 60's. These might be more clear show a little more than Nicks did.
As for the bracket, really easy to fabricate.
On the drawings, I think it was in the 2nd or 3rd page. Will have to check when I get back. As for the spacers, you can easily fab them out of 5/8" round stock or visit your local speed shop.

[Alex Evonosky]

Sorry, I thought I could post more than one.
Here is the other.

[Three Peaks]

Boy do I feel stupid. For some reason when I looked at Nick's picture I thought the part with the mounting bolts was a separate collar and needed to be fabbed. Alex's pictures make it much more clear from the different angles. I already have the mounting brackets on this frame, so I guess I'm good to go. Just the FR OE rack and some bolts and spacers and away we go.

What the heck did guys do before the internet?

Thanks again guys- Bob

[Alex Evonosky]

Bob,
To save you a little headache, try the following. (just a sugguestion) other guys may have a better waybut:
Get your frame level.
1. Set your bottom control arm at 0 degrees (level) Both sides.
2. Mount your rack loosely, plenty of room to raise it up.
3. Set up your laser level up and adjust the rack and ends so the red line runs thru the center of the rack and out to the rod ends.
4. After the rack and ends are level, measure the height between the bracket and bottom mounting plate of the rack.
Cut the spacers that length.
That should get you real close if you are concerned about bump steer.

Sounds a little long but real simple.
I basically used the laser level and a digital 90.00 level to set my whole frame and front suspension up.

Hope this helps.

[427sharpe]

I like the oe style rack because the lock-to-lock is a bit more favorable...I THINK the oe was 3.25 turns and the M2 is 4.25 or some such...the info is on the flaming river site. As for control arms, I fabbed my own by setting the spindle in place and then making the arms fit the picture....worked well for me!
For the spindle mod, it was rather easy. I milled the steering arm on the spindle out to a 1 inch hole, than used my lathe to make a set of bushings with a 1 1/32 od and an internal taper to match the oe tie rod ends. The extra 1/32" makes for a tight press fit to retain the taper sleeve, and locate the outer tie rod. In reality, if you put a steel washer under the castle nut the squeeze between the joint and the nut would probably hold the taper in place just as well. I have been told that the M2 outer tie rods will thread onto the oe inner, but I have yet to investigate that......It would be nice, because the M2 outer tie rods are available anywhere for a very good price. I bought the ball joint threaded sleeves from stock car products... www.stockcarproducts.com
I like the Explorer diff because it is MUCH beefier (I broke 2 TBird diffs at the mounts) and it has a strong mount near the pinion flange for extra strength. The bolts on the rear of the diff are wider apart, and were easier for me to fab into a stock looking cradle. The axles on the Explorer have the small inner shaft and large outer (also on Mustang Cobra's) so the parts fell together rather easily. The large diameter of the axle tube itself made it easy to shorten as well..plenty of room for an internal steel rod to be rosette welded into a unitized structure for a very strong a dependable axle.

[427sharpe]

I dont know if this will work, but an interesting tech article on M2 design and layout.....Independent suspension can be very simple and very complicated at the same time. Success in making it simple is learning the rules. And it has it's own set of rules. Important, Rule #1: Unlearn everything (almost) you know about steering and suspending a car with a solid axle and 4-link suspension. That would be like trying to play football using baseball rules.

The first thing to relearn is the action of the front axle and spindle during suspension travel. There are three things to control in the front wheel: camber, caster and toe angle.


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CAMBER AND CASTER

In a solid axle the camber is built into the axle and the caster built into the 4-bar design. Both are constant (they don't change during suspension travel). A solid axle moves basically straight up and down therefore, so does the spindle.

On an IFS System, the upper and lower control arms, as well as the spindle and car chassis, form an uneven parallelogram, as viewed from the front (see Fig. 1 & 2). The spindle moves up and down in an arc or radius, which is determined by the length and placement of the two control arms. Their placement also determines the amount of caster and camber change.

Fig. 1 -- Click for larger image

This is a correct Mustang II front suspension in a street rod, when the stock Mustang II suspension locations are used. Notice the parallel upper and lower arms. Also notice there is minimal camber change and almost flat radius (1) in the movement of the spindle during suspension travel.



Fig. 2 -- Click for larger image

Now we have added the stock Mustang II steering rack in the stock Mustang II location using the stock Mustang II tie rod ends. Notice the radius of the rod ends (2) matches the radius of the spindle. Also, more importantly, see that the inner tie rod pivot (3) is IN LINE with the inner pivots (4) & (5) of the upper and lower arms. This is absolutely necessary. Ford Motor Co. did their homework.

Important Rule #2: If any of the four pivot points are moved in any direction, for any reason, the spindle swings in a new, unique arc which is different from the old radius. Usually the inner pivot point of the upper arm on the Mustang suspension is the one to be moved. The control arm is usually shortened and the pivot shaft lowered to clear fenders on some cars (see Fig. 3). As you can see, the spindle will now swing in a new higher radius. That in itself is not a problem. But, please read on, as it is about to get real interesting.
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TOE ANGLE

The paragraphs that follow explain why Heidt's Hot Rod Shop does not make Mustang Kits for certain cars.

As we mentioned, there are three things to control in the front wheel. Camber and caster we've already covered. The third is the toe, or steering angle at which the wheel is pointed, which determines where your car goes.

You can see that this means the spindle must always remain in the direction you have pointed no matter where the spindle is in the suspension travel. This is the job of the "Tie Rod". As you can see, the exact length and location of the inner pivot of the tie rod must be very carefully selected so the outer ends of the rod, which is attached to the spindle, swing in a radius which matches the spindle radius exactly. When deigning a brand new suspension system on the drawing board this determination is very easy to make, since the tie rods on the rack are actually designed to match the control arm and spindle radius. But on your conversion, this is where the problems start. So this is the next thing to unlearn.

When mounting a steering box in a solid axle installation, motor mounts, etc. usually dictate the location of the box and the pitman arm is modified to align the drag link with the tie rod. Selecting and installing a rack-and-pinion is nowhere near that simple or forgiving. When adapting an existing suspension design, such as the Mustang design, it is very important to keep every single mounting location and pivot point, including the rack, in their original designed places. As you have just seen, the Mustang rack, with a specific tie rod length, was designed by Ford to match the swing radius of the Mustang spindle using stock length Mustang control arms in the locations which were selected when the Mustang was originally designed.


Fig. 3 -- Click for larger image

This is a typical "modified" Mustang II installation in a '32 Ford type car. This first change is to shorten and drop the upper arm pivot (4) to clear the fender. This causes the much sharper radius (1) of the spindle and resulting increased camber change. Also notice that the two arms now intersect at a theoretical point (9). But this alone is not the bad part. The next step will show you why.

If you shorten or lower the inner pivot point of the upper arm, the spindle will now swing in a new, different radius which no longer matches the current tie rod radius. If you raise or lower the rack location, or change the tie rod length for any reason by using a longer tie rod end, the tie rod will swing in a new radius which does not match the current swing radius of the spindle (see Fig. 4).


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EXPLAINING BUMPSTEER

The bottom line of all this radius explanation stuff is this: Since the tie rod ends attached to the spindle steering arm, the tie rod controls the steering angle of the front wheels. If your car goes over a "bump" the spindle goes up and down in its swing radius, determined by the upper and lower arms (remember?). If the tie rod swings in a different radius than the spindle during this suspension travel it will push or pull on the steering arm of the spindle, changing the direction of the front wheel, "steering" the car. And that is how the term and the monster "BUMPSTEER" were created, where 95% of the problems with incorrect suspension design are found. It is from people not really understanding this most important relationship between the tie rod length (not the overall rack length) and the spindle swing radius. They feel that if they are able somehow with enough modifications to the parts to "physically assemble all the parts" that it must be OK. Then they pull down the driveway, over that first curb and low and behold: BUMPSTEER. When you drive a car with BUMPSTEER, the car tends to wander and hop around as you drive down the road over bumps and dips. You have to constantly steer the car to keep it in the lane. Not what you would call an enjoyable ride.


Fig. 4 -- Click for larger image

...it's all over by now. The other common modification/mistake is to widen the crossmember and use a long tie rod end. Ugh, as you can see, by adding the longer (incorrect) tie rod end, the inner pivot of the tie rod (3) now has been shifted way out of line by the dimension (6). Disaster! The flatter radius of the outer tie rod end (2) no longer matches the sharper spindle steering arm radius (7). This causes the spindle steering arm to follow the incorrect radius (2) and change steering angle, or "steer" as the suspension travels up and down over "bumps": more commonly known as "Bumpsteer". You can also see that the projected line from the tie rod does not intersect the intersection point (9) of the control arms. It should. This is why the only way the Mustang II system works correctly is the way Ford designed it, using all stock Mustang II parts, in the stock Mustang II locations.


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BUILT-IN ANTI-DIVE

Anti-dive is another characteristic required in an independent front suspension system. Anti-dive helps prevent the car from "nose diving" under hard braking conditions, hence the name. It is something which is found in every factory car manufactured, including the Mustang and Pinto, visible in the suspension design in the upper control arm. It is mounted on an angle, with the FRONT pivot higher than the rear, not level (see Fig. 5).

The actual description of how anti-dive works involves extensive vector force diagrams and is much to lengthy to describe here. Let's just trust the big three auto manufacturers on this one, because they all use it. The Pinto uses a 3° angle for their anti-dive in the upper arm. It may look funny only because you are not used to seeing it in a street rod. Look at your family car. Do things look more normal now?

Don't bother looking for it one somebody else's street rod, especially one with other Mustang kits on it. They don't always know why the upper arms are "crooked" and fix(?) them. But how funny would your car look with the bottom of the grille ground away from bumping the street?

Now for the real point of this whole technical explanation.

Fig. 5 - Click for larger image

This is the side view of a correct Mustang IFS kit. Not the angle of the upper control arm, that is higher than the front. This angle, through a lot of geometric forces in the spindle when braking, generates a lifting force on the frame at the inner A-arm mounts. This is the same angle as the Pinto, which gives the same amount of anti-dive force as the Pinto. Simply put, factory designs work the way they are supposed to in every respect, so why throw all their engineering and testing out the window?

This is the only way to incorporate this important feature, no matter what else you have heard. If you cannot see the angle in the upper arm, then the anti-dive is simply not there. Period.



Bahhh.. the pictures didn't paste! For a full view go to www.heidts.com and scroll to "other info", than 'tech info'...

[Morris]

The MGB rack is to long.....

And you should know that the bump steer on the standard set up is way off......

Morris

[mickmate]

Hey Morris, where is the link to that fantastic thread? OK....... how much too long and using what components etc? I thought that the rack spacers and tie rod extensions fixed that.........

[Morris]

Mick

http://www.gasholes.com/smf/index.php?topic=3232.510

There's the Thread .....and that is starting on page 35 at the bottom of the page ......

That's when we did the bump steer and found out the steering is not right on these cars.....

I think I even documented it with the camera......

But anyway.... the rack is to long for the Kirkham suspension .... and if they copied the original then it would be to long for yours...... but .... I would do what you are doing and then check it and then if you need to make a change...then make the changes that are needed.....

Ready the pages and it will take you thru what we found out and I haven't published what we are doing about it as of yet......

We have a fix and when I get it done and finished we'll publish it.....

Hope it helps

Morris

[Specialk]

I just uploaded an artical from a kit car magazine that detailed the underside of a Hi-Tech, and it has a lot of comments on the suspension they used. Maybe it will give some ideas, or at the least it is an interesting article.

It is in my photo gallery

[Specialk]

Another thing that may be of use, I also have some photos of a 427 Shelby chassis I built awhile back.

Chassis Photos Are HERE