History Rear suspensions (from the past)

There seems to be too much emphasis [on this thread] about torque-arm torque reaction.

This torque reaction is Pinion torque reaction which is far less than Axle torque reaction due to gear reduction.

Axle torque reaction is "thrust" [the force that drives the car forward], When you get x amount of torque at the tyre footprints you get the same x amount of thrust driving the car forward.

The same goes for pinion torque trying to rotate the crownwheel, you get the same amount of torque reaction trying to rotate the axle housing upwards [this is always less because of gear reduction]

Please note that brake torque reaction is greater than pinion torque reaction due to the brakes being mounted directly to the axle and transfering down the torque-arm

In drag racing the problem of the RR tyre spinning is caused by driveshaft torque not torque reaction. The driveshaft tries to spin the whole rear axle like a propellor.

Getting back to the the subject of axle thrust, 3rd Gen Camaros have the trailing arms mounted directly in front of the axle centreline. The height of the front of the trailing arms dictates whether there is anti-squat or squat. If you look at the setup in the photo on post #38 the trailing arms are mounted below the axle centreline, therefore axle thrust vs resistance would cause the pinion to try and point downwards creating dive in the torque arm .If the trailing arms were mounted above the axle centreline the thrust will try to create lift in the torque arm [often mistaken as torque reaction]

The best way to tune a single torque arm suspension to counter-act driveshaft torque is to dial more anti-squat into the RH side. This is easily achieved by raising the front pivot on the RH trailing arm. [The Thrust will try to push the rear end into the ground on that side]

 

Ned, I don't know why, but they have refused to change the link to my new home. I've narrowed it to only the drag racing section, so, perhaps, they'll change it. If not, the full URL is http://www.shopeshop.org/ and the drag race section is http://www.shopeshop.org/contentsDrag.htm I've learned some things over the years and it shows. My 3link derivation in my Ramcharger years required a few pages to develop. Now, I've realized that some valid generalizations allow a lot of simplification. Even the old high school maxim that parallel lines meet at infinity allows some interesting options.

I just noticed you're not located in Britain. Shouldn't have allowed your British spelling to cause me to jump to conclusions. I'll be mowing the lawn next to the "pavement" today.

And, the link to your blog doesn't seem to work.

 

I thought I made it clear that it's the DRIVESHAFT torque that causes the problems. Sorry if I didn't.

And, I like your last paragraph. Those with 4links, for instance, can simply add a little antisquat on the right and reduce the antisquat on the left. I've suggested this in the past, but I don't know if anyone noticed it.

 

Welcome aboard! We appreciate your experience. Now, try to visualize a single ladder on the right and consider the possibilities. Realize, of course, that the old Fords and Chevrolets used, in effect, a single ladder with the "tube" of their torque tube drive.

 

I really like that mount for the 36 bones.

 

You made it quite clear. some replies were worded to be confusing [eg: post # 31]

Antisquat can also be added to a 3 link [3rd Gen Camaro] by raising the RF pivot. The problem with too much anti-squat is it promotes roll-oversteer [caused by wheelbase change/lengthening during suspension compression]
You end up with a lot of Forward Bite but the car can be very twitchy on uneven surfaces.

This is why modern drag racers prefer to preload the RR with ladder bars or use an anti roll bar on 4-link

 

Kerrynzl;
The reply in post31 was not worded to be confusing - the poster was confused & worded the Q as best he could, in an attempt to become unconfused. He stated he did not understand - & still doesn't. It's all ok. If needed, I'll go directly to one of the helpful sources, & ask via PM.
Marcus...

 

What about this old formula to calculate the length of ladder bars?

 

That is the one that I was taught.

 

Great thread.
Is there any advantage of a 3 link system over a 4 link?
I realise 3 is old skool and the 4 is probably considered modern, but technically how do they compare???
With a 3 link does it matter which side the top arm is attached to?

 

I, for one, would like a better drawing, please! I'm warming up to the math, but the exact design of the right side link is still unclear to me. Gary

 

A 3-link with a lateral-locating device has true free articulation in both the degrees of freedom required of a rear suspension system. So has a triangulated 4-link.

A 4-link with a lateral-locating device has true free articulation in either vertical motion or roll motion, and two conditions of one of them for every condition of the other. In other words it can only work in practice by binding slightly.

 

So do all of these including the 3 link still require a watts linkage or a panhard rod?

 

I have posted all I know about this design.
See post #64 for the spring options. They are at the bottom right of the calculation sheet.
Torque arm design is shown in post #15
Post #24 for construction layout and details for coilover springs. Notice the long and low panhard bar. I think a watts linkage is neadlessly complicated and offers no benefit.
See post #84 ,first picture, for 40 front spring installation. No panhard bar.
There was a suggestion about angling the right bar up to give some anti squat. I think that is a pretty crazy idea as you would induce rear steering. From the math sheet, #64, you can calculate the lift and it is significant and has no roll steering induction. You want the links parallel to the ground or angled down in front like I have them.

 

I see for sale on ebay those ladder bars that have that rear adjuster gizmo, are they helpful at all or just a novelty?

 

I don't know which ladder bars you're referring to [without a link] but there are ladder bars that can be adjustable for pinion angle.
A common drag racing set-up is to adjust the LH ladder so the front pivot on the bar is approx 3/4" lower and use a jack to help install the front pivot bolt.
This preloads the RR to help counteract driveshaft torque.

If you dont have adjustable ladder bars, you can get similar results by dialing some wedge into the front suspension [either add load into the LF or unload the RF]

 

Great info and thanks.

 

The 3 link is gonna require a panhard bar or watts linkage. At least it does on the 3rd and 4th gen F-bodies

I thought angling one side only sounded kinda goofy, too. Glad I'm not the only one.

 

It requires a panhard bar with coil spring like the GM cars. A 40 Ford cross spring does not.
The design as presented works fine.

 

Please help me understand.

If you counteract the driveshaft torque on acceleration, won't it have the opposite effect upon sudden, hard braking?Wouldn't that cause the rear axle to go from evenly loaded to exaggerated unloading on the other side?

I was watching a compilation of drag race crashes. I noticed, on some, when the rear wheels started to spin, or especially when it looked like they let off the gas or were on the brake, the body of the car would suddenly rock slightly right before they really lost control.

Maybe it's not a problem because the torque of an engine slowing down isn't as much as accelerating - so it's not a great enough force to upset the suspension?

What about the brakes? Does the arm being off to one side rock the rear axle when braking?

Instead of counteracting driveshaft torque, why not eliminate it with a strong ladder bar on each side that forces each rear wheel to rise and fall at the same time? (For drag racing only)





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

 

"If you counteract the driveshaft torque on acceleration, won't it have the opposite effect upon sudden, hard braking?Wouldn't that cause the rear axle to go from evenly loaded to exaggerated unloading on the other side?"

It might have an effect something like that when engine-braking, but as the rear brakes are attached to the rear axle, it wouldn't apply in actual braking.

 

Still looking for some good drawings or a lot of great pix, please, please, please. Gary