Technical Can Anybody See Why This Wouldn't Work? Suspension...

You will need to drop the front spring eye to install the slapper bar.
But once installed it will behave like a standard slapper bar.

Seriously consider the "Shelby traction override bars" which examples are already suggested in this thread [they work great in drag racing and road racing]


Axle tramping is caused by TWO forces acting together to wind up the spring [then the kinetic energy is released]
The 2 forces are
1: Axle thrust or forward thrust at the axle centreline [trying to accelerate the vehicle] This force tries to shorten the distance between the axle and the front eye.
2: Pinion torque reaction [the pinion tries to climb the crown wheel, which it is trying to rotate downward
The combination of the 2 causes the leaf to "S" shape itself. All you need to do is remove one of these forces from the equation.[which is how slapper bars work]

Axle thrust is always higher than pinion torque reaction by the factor of gear reduction [remember the forces and reactions come from the engine....not the tyre footprint]
Because of this ^^^ controlling thrust is more beneficial.

If you mount the [pivoting] bars directly in front of the axle centreline ,all the thrust is transferred down the bars.
The springs only need to support vehicle weight and pinion torque reaction. [example: 3rd Gen Camaro's and Lotus Cortina's]

Shelby mounted the bars above the axle centreline so they can also control brake torque [brake torque is far greater than pinion torque reaction]

 

The Camaro radius rod would work well, but it probably won't help as a sway bar much. Notice it is also attached to a bracket welded to the axle?
The reason traction bars worked was because they were either attached against the leaf springs and held in place by the 4 U bolt nuts, clamped on to the spring at both the front and the rear side of the axle, or they had a bracket that attached to the axle.

 

All ends up outside frame rails.

 

You've got that backwards; the force is coming FROM the axle pad/spring, the arm is transferring it AWAY from them.

 

Ok............................and still trying to rotate the lowering block assembly...........???

 

Try it now......................

Newton's third law is: For every action, there is an equal and opposite reaction. The statement means that in every interaction, there is a pair of forces acting on the two interacting objects. The size of the forces on the first object equals the size of the force on the second object.

 

I see little functional difference between a axle/spring/bar connection to a axle/bar/spring connection. Yes, with it closer to the axle the leverage on the bar is increased but unless the pad fails I don't see how it matters. Remember, this won't be seeing any rev-it-up-and-dump-the-clutch starts. If welded to the housing, then I have ladder bars and I certainly don't want that...

 

Remember, there is no separate block; the arm IS the block.

 

Your original pics.......

1). Under acceleration, the axle tries to rotate clockwise. This rotates your 'lowering block' clockwise and bends/bows the front half of the spring upwards. As everything is mounted solid, the arm swings upwards, and the saddle under the spring moves upwards to contact the underside of the spring. This will try to bow the spring more. This is why the saddle needs to make contact under the spring eye, not under the spring itself.

2). As the end of the arm contacts the underside of the spring there is a force exerted downwards on the arm (Newtons Third Law - equal and opposite reactions). This tries to rotate the 'lowering block' anticlockwise, while the traction force is still working to rotate the whole axle/block clockwise. This creates a twisting force on the 'lowering block', trying to rotate it within it's clamped space. Not a good thing.

3). If Shelby used his override traction bars in his track cars, I would assume the system works well.....

4). Lotus used a similar system in their Cortina's, and it certainly did work well......(bottom setup).
By the way, the top set up works exceptionally well also...........

 

Miss Steve’s escapades here also. For sure, he’ll know what to do, call him!

 

What if you made the traction “bars” with a pivot at the lowering block end then clamped the front of the bar to the spring? The farther forward on the spring would be ideal.
The optimum set up would be for the bar to be the same length as the spring from the center of the housing to the center of the bars front pivot point so the rear end and the bar swing the same arc. ( no binding)
When I designed the rear suspension on the Cyclone I fabricated the mounts and traction bars with the goal to have no bind, have the suspension work as it should, (ride good) and have no chance of wheel hop. The axle and traction bars swing the exact same arc. (The springs have been moved inboard 2 1/2” on each side)

 

The snubber hitting near the front spring bolt will work just fine. It’s the length of the spring that causes it to bend . Probably 18 inches between the axle and mounting bolt. That’s why it’s a spring. Having the snubber bumper hitting the spring a couple of inches behind the mounting bolt will take almost all the “ spring “ out of play.








Bones

 

I don't think that the OPs plan will work. The rear end of the bar is too close to the axle center line to have enough effect.

I would just add two or three half leaves and a few clamps to the front spring segments. That's what I did on my o/t Hemi four-speed GTX, and it launches beautifully and runs tens with no traction bars and no snubber. It's all you need.

 

You asked.
We made suggestions.
Its your car, do what you think needs to be done.
Let us know how its working in a couple years. Gene

 

I always find these types of threads interesting. A lot of the responses refer to race cars of various configurations. While these are made with good intentions they really don't relate to what Steve is trying to accomplish.
His parameters were:
1. Eliminate wheel hop under MODERATE acceleration.
2. Maintain as much ground clearance as possible while lowering the ride height.
3. Increase the roll stiffness with minimum increase in spring rate during straight line driving.

His method will work. Is it perfect? No! Can it be tweaked to be better? Yes!
Some of the other designs mentioned might be better. But, everything in the design of an automobile is a compromise. He only wants and needs a slight improvement in function of the existing design.
With that in mind, here are some points to consider.
If using the bar as the lowering block it might be best to keep it the same width as the leaf springs. That way nothing has to be shimmed and the u-bolts will tend to keep everything aligned.
It would be best to have the front contact point right above and below the spring eye. Being that we are talking 'moderate' it might not be as important as we might think.
Making the contacts adjustable would be desirable.
Be careful in de-arching the springs too much. If they are flat, the center to center distance will decrease on bumps. I'm not sure if that is acceptable or what other problems it might cause. I would not add leaves or clamp them as this increases spring rate.

My 73 year old $.02 Now worth $.22 in today's money.

P.S. I had to smile when I read this:

Mark, I can't believe you said this in your outside voice

 

While they look similar to the Traction Masters of the '50s they function differently through a pivot. John Calvert started in business in 1991, slightly after the 1965 H.A.M.B. cutoff.
Not trying to be a jerk, just struck me a funny.

 

I think the concept sounds great personally. The only real change to the original concept I would suggest is making the box section around the spring 2 piece with the bottom snubber hitting below the spring eye. 2 piece would allow easier installation without having to remove the spring or axle. It also allows the bottom part to jog forward to hit below the spring eye. I would imagine 1/4 or 3/8 plate for that bottom part would be plenty strong to jog forward a few inches without the extra support of the box section.

I am really not concerned as others are about the mounting method to the axle. The forces are not really any different than any other lowering block and slapper bar combo. Ultimately the U bolts take up this force. Just make sure your centering bolt locates things well, possibly even going through the whole traction bar and bolting it to the spring pack directly.

Your traction a could be a leaf spring such as a truck overload spring cut in half. Just need to find something flat, thick, and long enough. Not sure how to attach the box section because drilling into springs is no fun.

The other though on a different direction would be to use a sway bar. If located and attached right it could be used to control thrust and / or rotational forces, as well as function as a sway bar. Just need to package it out if your way.

Do you have pictures of what you are up against? I know you have mentioned exhaust and convertible bracing being a concern.

 

Don't know how much sway control is part of this operation, a dedicated sway bar probably a better option for that, or how much blocks actually increase spring wrap (about a billion vehicles use 'em, think I'd just put them in and see), but don't pinion snubbers do about the same thing as slapper bars and the like? Don't reduce ground clearance and not exactly visible..

I do find it an interesting idea, if really necessary. What's the time frame?

 

Studebaker also used the "above" the axle solid bars on some of their cars.

Whatever you end up with...USE THE SPRINGS PIVOT POINT CENTERS for your bars end points.
That is, the center bolt at the axle center and the springs front end eye bolt.

If you do not do this...you will either induce either a bind in the system, or if you are using the whole leaf spring, you will be bending the spring in a way in which is was not designed to be bent..!

It's all plane ol simple geometry..!

Mike

 

Finally, someone who gets what I'm trying to do! I'M NOT BUILDING A RACE CAR!!!

I will admit that my original somewhat crude drawing seemed to flummox a lot of responders, so here's one with more detail...

More than a few didn't take note of the fact that moving the axle centerline up 2-3" more above the spring would change the geometry of their solutions and a few to my thinking would be rendered ineffective. I don't see de-arching the springs as viable as they're nearly flat now. As to what I'm up against, no pics as I don't feel like crawling under the car in the rain so I'll describe it as best I can.

What's screwing me is the exhaust. Ford installed a welded-in hell-for-stout X-member on the 'verts, and this isn't some sheetmetal stamping, oh no. It's an actual I-beam, at least 3/16" thick in all webs and God only knows how much it weighs. The convertible weighs 200 lbs more than the hardtop, I'm sure this is most of it. Ford also re-routed the exhaust compared to their other models, bringing it in close to the driveshaft which is where the holes in the X-member for the pipes are. I'm assuming they knew what they're doing, so I don't really want to cut 'other' holes. I'll note here that headers for this model are also specific to it because of this (and I was a bit amazed that any were available!).

It's the tailpipe routing that's doing me in. As the pipes leave the X-member, after they clear the floor and the crossmember that mounts the shocks they turn up to go over the axle. Once they're high enough to clear everything, the next bend is rotated to point them outward, crossing under the frame at roughly a 25 degree angle right behind the axle snubber. It then immediately bends down/back to get into the space between the frame rail and the rear lower rocker panel which is where the muffler goes. There's no place to mount the mufflers under the passenger floors. I can't stay inside the frame as there's not enough room between the frame/fuel tank unless I hang it down and now I've got issues with dragging the exhaust.

I looked at and discarded any upper link system because I have no place to attach a bracket on top of the axle housing. Over the spring, it hits the snubber. I can't go outboard, the tire is in the way. Move it inboard, now it's the frame. Inboard more, it hits the exhaust. Re-routing the pipes would require square bends, not so hot for flow, and notwithstanding that it would put the pipes closer to the fuel tank than I like. I thought about rotating the bracket so it faced forward, not up, but I don't like the geometry changes that introduces. Mind you this is with 1 3/4" pipe, I'd like to go bigger and this will require some very careful fitting that may need to be flattened in a few places. Pointing the bracket down initially looked feasible, but if I put the pivot in line with the spring as a few showed I wonder about it's effectiveness with the axle raised with the blocks. Moving the pivot up closer to the housing again introduces geometry changes that could cause binding. Hopefully this brings some clarity...

So this brings me back to my 'slapper bars'. All these issues disappear, and these are proven performers. No, they're not as good as other designs, but they should be 'good enough'. As you can see from the new drawing, I've addressed most concerns, and this was more-or-less the plan all along. The 'loop' in the front was always going to be removable, I just didn't show it in the original drawing. The main tube will probably be 2X2 1/8" wall square tube with the 'lowering block' fabricated/welded to it to get the desired drop. I may use 1 1/2 round tube if I can find any with 1/8" wall thickness as it is a bit less rigid and might help with ride quality while still limiting wind-up. I will need to angle the bar 'up' slightly towards the front to clear the spring arch and leave room for the braking snubber.

One point that came up I will address; contact of the 'traction' snubber against the spring. I can't get to the spring eye without a total rebuild of the front spring hanger, so instead I can adjust the length of the contact area on the lower loop, spreading the force over a wider area. Any pre-load may need some experimentation to find the best compromise between effectiveness and ride quality.

 

If you can get the bar end 'saddle' to contact under the spring eye, or close to the spring end, your design will work much like a normal, basic 'slapper bar' system. The only problem I have with it is that you are trying to use the part that is increasing the spring wrap (the lowering block) to do the job of negating it. This will really load up this area. With low HP, and sensible launches, it may be fine...................fingers crossed.

 

I vote yes, get the same results of a traditional traction bar as far as spring control, plus lowering block, and ground clearance. I think it's a great idea

 

Post #33 gets my vote.

 

I get what you’re trying to do here. This drawing is better than the first one, but that one was good enough.
Will it work? Yes, probably, and with moderate torque and reasonable expectations, it’ll probably be fine. As you say, not a race car.
But, that’s also kinda where you’re losing me. This is not a race car. So is spring wrap actually a problem that needs solving? Are you going to have enough torque, and enough traction, and a heavy enough foot, that this is actually going to be a problem?
Is there enough room for this device between spring and frame rail? Will it fit?

 

Here is one of the sites that might be helpful. Shelby used the top axle mount on the GT 350's
for corner braking purposes. The single top axle link will dynamically unload the downforce
applied as the axle tries to counter tire rotation at launch. Anyway this site will help calc the
antisquat w/ any trial design.

https://www.crawlpedia.com/4_link_suspension.htm

 

A few years back I set up a dirt car - >500hp limited late model. Rules allowed only leaf springs, no sliders and max 2 inch lowering blocks. No added suspension bars allowed. I used 2 inch lowering blocks with wedges to set pinion angle and half leafs cut from a couple random sets that matched the width of our Camaro springs. One was about a sixteenth of an inch thicker and it went on the left. We never had wheelhop issues, but occasionally it would slip the left rear tire on the wheel - traction wasn't a problem.

Have you experienced and wheel-hop in your car, or is this in anticipation?

In your mild street car with limited tire size, a new set of shocks is likely all you need to control possible wheel hop.

 

Leaf springs have a life cycle. Your sixty year old springs are dead.

Go to your local spring shop and have them build you a new set with less arch and stiffer front halves. I'd figure the arch to where you still need an inch or so of block just to give yourself some adjustment.

 

Won't fit, the axle pivot hits the snubber/frame/exhaust.... and offers no antisway function. That actually seems to be another issue, I didn't find anyone offering a rear sway bar for this car, probably for the same packaging problems I've mentioned.

Well, to be honest I don't know if spring wrap will be an issue. But past experience with these era Fords says I very well may have an issue (particularly with lowering blocks added) so I'm being proactive. I'm installing a TKX 5-speed and will (budget allowing) put in a 445" FE at some point along with a 3.5 posi rear. The springs are outboard of the frame so this is the one place I do have room which is why I chose this solution. And while I'm not as speed-mad as I once was, I still like to have a car that will move when I want it to. At 4000+ lbs, that takes a lot of power. Drag-strip-style launches won't be on the menu however...

They sure don't seem dead. The car sits dead level like it's supposed to and rides like I remember (when these were much younger). The springs are pretty flat already, so de-arching doesn't look like it's a viable option. And these will be a lot cheaper than having new springs built...