History Rear suspensions (from the past)

Andy;
"With a little thought, you can calculate the offset required to cancel any driveshaft torque, yielding equal tire loads all the way down the strip"
How do you calculate where to locate the rhs ladder bar to cancel out torque-reaction(s)? & I'd guess the lhs locator bar is positioned the same distance away from center-line that the rhs is?

This looks different from the 3rd Gen F bodies torque arms location. Because of parallel leaf suspension w/o dbl-shackles?

I must be missing something easy.
TIA.
Marcus...

 

I guess the left side bar that GM used was due to space considerations.
I put the left side bar the same distance out so the front bushings would be loaded the same.
The length and off set of the bars is all a compromise an not that critical.
Having the spring behind the axle produces a lift on the right side without any engine torque.
The left wheel wants to unload some during braking.
The newer instalations have a bar from the spring to the pivot and the axle pivoting. This eleminates the above problems. I never felt anything odd with what I am running.

 

Can you describe a little more in detail how the above mentioned system works? I am having trouble picturing that in my minds eye. This all very timely as I am in the planning stages of replacing the torque tube drive in one of my old Buicks and was looking for alternatives to the GM truck arm system.

Thanks,

Ray

 

If you'll recall, the old Fords and Chevrolets had the torque tube drive and either leaf springs or a Panhard rod. What I wanted you to think about was an open driveshaft and a ladder (or torque tube or however you want to picture it) offset to the right of centerline.

 

Andy, I suppose this is true. You could offset so much that the LEFT rear was light, but anything's better than a symmetrical setup.

 

If this link works, you'll get a brief history of the Ramchargers, but no good picture of the suspension. I'll try to find a picture. http://www.shopeshop.org/ramchargers.swf

 

I´m just trying to understand your 3-link setup.
I have used a 62 Impala rear suspension to build a 3 link for my 56 Chevy. It has been working lilke a charm for about 15 years now. My 56 is not a drag car, but it hooks and handles pretty well, a lot better than with the stock leaf spring suspension.I added a subframe and made crossmembers to attach the trailing arms and the upper torque link...the upper trailing arm is not visible in these pics, but it´s in the same location like on 61-64 Chevies.

 

I'm not sure what they are called, torque arm or 3rd links, but most I've seen have the arm close to the diff on the right side of the drive shaft. But others are on the left. This version below (by BMR), uses a cage that holds the diff on both sides, a sliding link at the front, and a watts link at the back. I'm considering using this mostly for "packaging" - ie saves a lot of space that can be used for other stuff. Gary

 

Just think of (if it were possible) removing the torque tube, adding U-joints, and replacing the torque tube to the right of your now open driveshaft.
Your picture reminds me: I had a '53 Buick Super hardtop with the Roadmaster 4bbl and dual exhausts. It could outperform a '53 Olds. Beat a Ford flattie in a street drag and met the owner years later. He told me that was his last street race. Figured when he got beat by Buicks, it was time to quit!

 

"When better cars are built, Buick will build them".........Buick slogan for many years

Ray

 

This is a wholly different animal and a very complicated means of solving a very simple problem. But, it means some money for the outfit that sells them. A single ladder and a Panhard are all you need.

 

Remember gentlemen, they are not called "The Friendly Suggestions of Physics."

 

"In any conflict between Physics and Style, Physics always wins"

Ray

 

Still looking for your pix or drawing, Mr. Shope. Gary

 

I hadn't planned on going into it this deeply, but, if you're really interested in how much offset is needed:

All of the weight transfer is carried through the ladder. In addition, there is a force tending to accelerate the car upward. (This is characteristic of ladder bar cars.) In the side view, there are two triangles. One has a vertical side equal to the height of the front pivot of the ladder and a horizontal length equal to the distance horizontally between the rear tire patch and the front of the ladder. The other triangle has a vertical side equal to the center of gravity height and a horizontal side equal to the wheelbase. Determine the tangents (slopes) of the two triangles and divide the tangent of the triangle associated with the ladder by the tangent of the angle associated with the center of gravity height. The driveshaft torque, when multiplied by the axle ratio and divided by the rear tire radius, is the forward thrust at the rear tire patches. That forward thrust, when multiplied by the center of gravity height and the ratio of tangents and divided by the wheelbase, is the vertical load supplied by the ladder. When the ladder vertical load is multiplied by the offset and set equal to the driveshaft torque, it is found that the driveshaft torque appears on both sides of the equation sign. The offset, then, is equal to the product of the tire radius and the wheelbase, divided by the product of the axle ratio, center of gravity height, and the ratio of tangents.

 

Phew!!................I struggled in Algebra........did okay in Geometry.....but both were 60+ years ago

Ray

 

What happens in a hard corner? Let's say right around 1G.

 

Same here, with measurements, and angles.

 

Thanks for the info so far.

I actually was interested in the layout dimensions, & esp why they were where they were, & how to figure out where they needed to be, including lengths, to be able to adapt to different car/trucks.

I think this might be easier than I'm imagining it, but some pics, w/some drawing labels/descriptions, & then an working-thru example of the math, would help me a lot. Only got through calc 2, but that was 30+ yrs ago. & never even got close to an engineering degree, just an industrial tech.

The chev truck arms make sense, as does the 3rd Gen F bodies torque arms layout, so do some variations of 3-links, but I'm having trouble here. From your description, this may be a lot easier, & more adaptable to, a couple of upcoming projects. I'm also very interested in how this version works in hard/tight twisties (read: auto-cross, or haulin' thru country back road twisties). Also, it appears like this could be discretely added/hidden in a 20's->30's dirt-track/2-man-indy-type re-creation. Gotta admit, there were a lot of really neat (looking, anyways) oldie suspension systems in use.

Since we've waded in, we may as well go swimming into the deep end... .

TIA, for further info.
Marcus...

 

Mr Shope.
I think you are getting into weight transfer and thrust loads. I sure would like to stay just with the original post subject. These subjects are more for drag racing. We are mostly looking for street suspensions
I was thrilled that anybody had any knowledge of the design that I have used for decades. I did not think it up. I have had a 60 Chevy since new. It has the same rear suspension design. It is just hidden. The intersection of lines drawn thru the little upper link and the bigger lower link determines the end position of an imaginary torque arm. It is just a very mild version.
The suspension can be used for serious road race applications as there is no binding and you are not relying on bending suspension parts. It would be hard to set up a suspension if the parts are in a bind. I have the roadster driving nearly like my old XKE series 3 Jag. Jag actually has a patent on a version and used it under the C Jag at LeMans. I keep tuning the roll bar to get very light understeer. The decent into Death Valley from the west was a ball. Accelerate to the next turn, brake, corner, accelerate. Great fun. It is a great road car. I have alway driven straight thru to Kerrville from Phoenix after LARS. That is 900 miles.

 

Lets hear more?

 

This is a very good and interesting topic that has a lot of potential. I am very interested to see some setups with said ladder bar set ups and some pics that people are having good results with.



Sent from my iPhone using H.A.M.B.

 

Im in, need to reread to get my head around it. I posted in your last thread and I am happy this is where we are headed with the discussion

 

Yup, Andy; this is what I was kinda after. Just was hoping for some pic/drawing/math-displayed examples. I doubt technical answers would get the thread de-railed or shut down. & I'm sure it'd help at least one guy... .
Marcus...

 

Sorry. Should have said more about handling characteristics. First, we have done nothing to affect maximum skidpad speed. However, the length of that single ladder has other effects. First, the shorter the length, the greater the antisquat, or, in other words, the shorter the ladder, the more the car looks like a giant frog on launch. The front pivot point should be at least at the rear of the transmission, as in the early Fords and Chevrolets. Which brings me to the other effect. The shorter the ladder, the greater the roll oversteer. The rear wheels naturally tend to follow a smaller radius as you take a corner. As you increase roll oversteer and cornering speed, the rear wheels tend to take an increasingly larger radius. Although this is, to the driver, largely psychological, extremes can be very disconcerting. If you copy the lengths of the early Fords and Chevrolets, you will have no more roll steer than they had.

 

As for pictures and such, I've posted a link to a Ramchargers history which I made for my blog. I'm pretty certain I had, at one time, some pictures of the suspension, but I can't find them now. Anyway, it looked like any other 4link, except the front eyes were the rubber bushings from leaf springs and not Heims. As for the '59 Nationals, we were bolting parts on the car as it went through Inspection and there was no opportunity for link adjustment. As a result, we were so out of adjustment that, on the first hard pass, the suspension was overcompensating so badly that it bounced both right side tires completely off the strip surface. "Soup Up" magazine captured the moment and it appeared as their cover picture. Very embarrassing! As a result, NHRA officials made us put a bolt through the telescoping upper left link and the car became a simple 4link. I went back to graduate school shortly thereafter and no one picked up my work.

 

Yes, I have CAD on my computer, but there's a limit as to what I'll do for a forum. You'll have to do your own sketching and substitute your own numbers in my example. I've retired three times and I thought that was it. My last job was lecturing at UCF. Hadn't thought about it, but, if someone wants to hire me as a consultant and my funeral doesn't occur first, I suppose anything's possible.

 

Finally, I must emphasize that. if there are any other links extending forward from the rear axle...other than that single ladder bar..., that is not...I repeat NOT...that which is under consideration here.

 

A picture is worth a thousand words...and we've had a lot of them.

 

A full CAD rendering isn't needed to build a traditional hot rod.