Torque Arm, Watts Link, and Factory Lower Control Arms

[ProTouring442]

Thinking of making a change or two on the rear suspension for my '72 442. What are your thoughts on going with the factory located lower control arms, a watts link, and a torque arm? The car will be street driven, with no time on the track. How do I determine the proper length for the torque arm?

I am running a Ford 9 inch, and was thinking of starting with the torque arm from BMR or TCI, but I don't know how to make sure it is the proper length. Any thoughts?

Shiny Side Up!
Bill

[terryr]

I suppose it depends on the amount of AntiSquat wanted. Something like four feet-ish. Here is one program;

http://www.rossautoracing.com/antisquat.html

[JRouche]

I know you were asking about the torque link. Here is a nice link http://www.unbalancedengineering.com/Camaro/TA/

But Im more interested in the watts link you have planed. I just got done fabbing up the major parts for my watts link, its adjustable for RC, from about four inches off the ground up to nine inches up. Just curious to hear about what you have in mind. Id like to see the setup? Always wondering if I am going in the right direction, just like to bounce some ideas off other heads besides my own :) JR

[tomshouse516]

awsome. this is just what i needed to figure out the torque arm rear for my S-10.

[ProTouring442]

I know you were asking about the torque link. Here is a nice link http://www.unbalancedengineering.com/Camaro/TA/

But Im more interested in the watts link you have planed. I just got done fabbing up the major parts for my watts link, its adjustable for RC, from about four inches off the ground up to nine inches up. Just curious to hear about what you have in mind. Id like to see the setup? Always wondering if I am going in the right direction, just like to bounce some ideas off other heads besides my own :) JR

Well... erm... eh... seems your a bit farther along as compared to me! I thought I remembered someone making a watts ling for the A-Bodies, but I could be wrong.

Shiny Side Up!
Bill

[ProTouring442]

I suppose it depends on the amount of AntiSquat wanted. Something like four feet-ish. Here is one program;

http://www.rossautoracing.com/antisquat.html

Cool! I also understand the making the arm too long will cause hopping during heavy braking. Is this something I could run into with a street car, or is it more of something I probably wouldn't see on a car that will not get track time?

Shiny Side Up!
Bill

[Roadbuster]

I suppose it depends on the amount of AntiSquat wanted. Something like four feet-ish. Here is one program;

http://www.rossautoracing.com/antisquat.html

I just plugged in some numbers for my car and came up with a very long torque arm. Wheel base: 112 inches, Front tire radius: 12.5 inches, COG height: 18 inches (cam height from ground), Torque arm length of 72 inches gives me an anti squat of 108%. This seems like a very long torque arm and I thought it would be shorter. :confused:

Jon

[ProTouring442]

I just plugged in some numbers for my car and came up with a very long torque arm. Wheel base: 112 inches, Front tire radius: 12.5 inches, COG height: 18 inches (cam height from ground), Torque arm length of 72 inches gives me an anti squat of 108%. This seems like a very long torque arm and I thought it would be shorter. :confused:

Jon

Do you think the center of gravity is that high?

How would you figure out where the center of gravity is, anyway? :hammer:

Shiny Side Up! Bill

[The WidowMaker]

I also understand the making the arm too long will cause hopping during heavy braking.

my understanding is that the length of the arm (IC) doesnt matter, just the anti squat. if its above 100% the rear will want to rise under braking, so good front shocks are needed to keep the front from diving thus causing wheel hop. you can also dial out rear brake to keep it from hopping, but your losing potential braking ability which is counter productive.


heres a quick pic of mine. this was a few weeks ago, so some more has gotten done. its nowhere near complete in this pic, but it should give you an idea.

https://static1.pt-content.com/images/pt/2009/01/23712235018-1.jpg?1234929054

[Roadbuster]

Do you think the center of gravity is that high?

How would you figure out where the center of gravity is, anyway? :hammer:

Shiny Side Up! Bill

Yes I do. Here is why: My car sits about 4-5 inches lower than stock. I read somewhere (that I cannot find a reference for right now) that the COG height is about that of the cam centerline which on my car is about 18 inches. This is not too far out of expectation from checking Herb Adams' Chassis Engineering page 64: "Production cars usually have the center of gravity between 20 and 22 inches above ground. A typical oval short-track race car will have its center of gravity between 18 and 20 inches above ground."

You can measure the COG height using the method outlined here: http://www.longacreracing.com/articles/art.asp?ARTID=22

I have not done this. and it looks like a lot of work.

Jon

[JRouche]

You can measure the COG height using the method outlined here: http://www.longacreracing.com/articles/art.asp?ARTID=22

I have not done this. and it looks like a lot of work.

Jon

Hey Jon, thanks for the link. I have looked around for a way to measure CG and was not having any luck. Im half way there. I made some solid links to take the place of my shockwave springs while I fab up the watts link. They are at ride height. I may make some for the front too just out of curiosity. Been eyeballin longacre's budget scales (72595) and now I have a push over the fence to go ahead and get the scales. Always wanted some 1500lbs pads to weigh the larger ebay mailings :idea: Thanks, JR

[Roadbuster]

Hey Jon, thanks for the link. I have looked around for a way to measure CG and was not having any luck. Im half way there. I made some solid links to take the place of my shockwave springs while I fab up the watts link. They are at ride height. I may make some for the front too just out of curiosity. Been eyeballin longacre's budget scales (72595) and now I have a push over the fence to go ahead and get the scales. Always wanted some 1500lbs pads to weigh the larger ebay mailings :idea: Thanks, JR

Those look like a nice set of scales! What are you selling on ebay - Engines? :) Once I get my car finished setting the corner weights will be one of the last tuning things I do. Need to have everything in it first! I need to find a cheap way to get close for now.

Jon

[Norm Peterson]

Do you think the center of gravity is that high?
There's a nhtsa inertia database that also provides CG heights and fore/aft location for quite a variety of cars.

Most cars do fall in the 20" - 22" range. Hardly anything OE is less than 20", and nothing in that particular database is under 19".

There is another reference that uses the above data to come up with CG height = 0.39 * [roof height] + .01 (or thereabouts). For most purposes with a lowered car, 0.4 x [roof height] should be entirely close enough.


Norm

[terryr]

Torque arms do have high A/S. But that formula does have that warning ; "Torque arm height must be on or above line of action". But it doesn't say what happens if it's lower. I plugged in a 112 inch arm and it said 69 percent. That can't be right.

Here's something else from the same site which seems to contradict their program;

Torque arm length depends on rear weight percentage plus wheelbase length. If the torque arm is too short and the rear weight percentage is too small, the rear of the car will lift when the driver stands on the gas. The correct approach is to have a torque arm length that falls about 7 to 8 inches behind the horizontal center of gravity.
This horizontal C.G. can be computed by multiplying the wheelbase by the front weight percent. The rule of thumb is the larger the rears weight percent the shorter the torque arm, because the horizontal C.G. is located further behind the front wheels. For example, 53 to 50 percent rear (42 inch arm), 58 to 54 percent (36 to 38 inch arm), a Short track with traffic use (32"TO 38"), a long track with sweeping turns use (38"to 44").
Generally moving the panhard bar from the right to the left of the chassis will cause tighter corner entry, as will running the panhard at a downward angle to the right. Weight transfer, balance, spring rates and percentages are the key. (the process is to make both rear tires pull evenly and at there max determine forward bite.)

and;

The torque arm became popular with the '82 Camaro. While it may appear that the front attachment point is the instant center (IC), the reality is that a torque arm's IC is actually the intersection point of the lower control arms with the torque arm.

Here's some other programs to chew on. Page 14 is torque arms;

http://home.earthlink.net/~whshope/

[Norm Peterson]

There are at least two problems with that link, though you can work around them if you tell it the right lies.

#1 - given the drawing, that is not a torque arm, as it is indicating the chassis side pivot is a pin connection that does not permit fore-aft plunge of the arm as the suspension moves. What they are showing is a ladder bar, which is a different animal.

#2 - That program is making the assumption that the vertical coordinate for the chassis-side pivot is at axle height. Rt, actually, as it is not considering vertical tire deflection due to the weight being supported.

More generally, the antisquat percentage is related to the slope of the construction line that runs through the chassis pivot and the contact patch, not the chassis pivot coordinates themselves. The formula in the link sort of says that, just not very clearly if you're expecting to read this description as text.

I think you can trick the link into doing the correct math for a ladder bar if you enter the chassis side pivot height in the Tire Radius (Rt) field. Little white lie #1.


As terryr has mentioned, the IC for a true torque arm suspension is only partly defined by the TA itself. It's actually a line through the TA chassis pivot drawn perpendicular to a line through that pivot and the axle center. This perpendicular line is not quite vertical, but is close enough to that in most cases. The rest is a construction line drawn through the LCA longitudinal axis (think side view). Easier to draw than describe in words.

If you were to throw the vertical and fore/aft coordinates of the intersection of the LCA line and the perpendicular TA pivot line into the Rt and Lta fields respectively, the link will still give you a good answer. Little white lie #2.


Norm

[ProTouring442]

Damn... I think my head is going to explode!

I'm starting to think the easiest thing for me to do is to measure the length of a Camaro torque arm, then calculate the length of the one I want to run as it relates to the difference in wheelbase between the two cars. This should get me in the ballpark, and then I could play around with various lengths by making the arm/crossmember adjustable. As no track work is in order, I would think I could play around with the length until I find a combination that doesn't cause braking problems during a road test. Hmm...

Shiny Side Up!
Bill

[Norm Peterson]

It's a lot easier to understand if you have a picture to look at. Hope this works and that it doesn't overload Jon A's bandwidth, as I'm out of upload space here. It's originally from RCVD and the "Slider construction line" is what I called the perpendicular line. The roll axis line is not the TA line through the axle center or the chassis pivot.

The IC vertical and length dimensions go in the linked calculator.

https://static1.pt-content.com/images/pt/2009/02/Ta-1.jpg


Antisquat stuff (the middle picture is for solid axles)
https://static1.pt-content.com/images/pt/2009/02/AntisquatJPG-1.jpg


Norm

[mugzilla]

Here is my idea for an A-body (olds 442) rear end locating assembly ...

Take the edlebrock hopper stoppers which has a good idea in relocating the upper link in the four link suspension ...

not much lateral control ...

Take a stamped upper rear end control arm of the jeep (#13) which should control lateral movement quite nicely and make an adjustable locating attachment for the upper arm ball joint #21...

The control arm would work well adjustable tubing arms

https://static1.pt-content.com/images/noimg.gif

[Norm Peterson]

Piece #13 is alternatively known as a wishbone, and it can be attached to either the top of the pumpkin or underneath it. Either can be made to work in various circumstances, but the lack of intermediate attachment points works against it. You have a choice between about a 6" rear roll center height and an 18" one with nothing in between. Can't go much lower than 6, don't want to go higher than 18. So yes, it's do-able. Just not very "tuneable".

It's been done in cars before - IIRC, it was Alfa-Romeo that used the upper mounting, and Lotus and at least one Camaro(?) race car have used the lower.


Norm

[shmoov69]

That is what my 58 Chebbie has under the rear. Don't think it would handle really well tho, but I could be wrong.
I think that "Chicane" had a wishbone in it too IIRC.


The other stuff.......Well, I guess I should've studied more in school!! LOL!

[mugzilla]

Piece #13 is alternatively known as a wishbone, and it can be attached to either the top of the pumpkin or underneath it. Either can be made to work in various circumstances, but the lack of intermediate attachment points works against it. You have a choice between about a 6" rear roll center height and an 18" one with nothing in between. Can't go much lower than 6, don't want to go higher than 18. So yes, it's do-able. Just not very "tuneable".

It's been done in cars before - IIRC, it was Alfa-Romeo that used the upper mounting, and Lotus and at least one Camaro(?) race car have used the lower.


Norm

I run a stock 442 that hooks up fine. I see this as a cheap replacement for a watts link.

I saw an off road unit that looked good ...

I be running in stock configuration. I wonder if I could run something to complement the stock control arms ...

[mugzilla]

That is what my 58 Chebbie has under the rear. Don't think it would handle really well tho, but I could be wrong.
I think that "Chicane" had a wishbone in it too IIRC.


The other stuff.......Well, I guess I should've studied more in school!! LOL!

It's like an Old Lady ...

She has a little wiggle in the trunk that I don't mind 'cause I know how to drive that stuff ...

I wouldn't mind if it was gone ...

[ProTouring442]

That is what my 58 Chebbie has under the rear. Don't think it would handle really well tho, but I could be wrong.
I think that "Chicane" had a wishbone in it too IIRC.


The other stuff.......Well, I guess I should've studied more in school!! LOL!

Actually, your '58 Chevy (car) would have had a 3 link, the upper being offset to the passenger side of the pumpkin, with a panhard bar.

Good grief, how do I remember this stuff??

Shiny Side Up!
Bill

[Norm Peterson]

I run a stock 442 that hooks up fine. I see this as a cheap replacement for a watts link.
Assuming that you can live with either of the roll center heights, it would be an alternative to a Watts link and either the upper or lower arms because you'd have to remove either of those as well.

A wishbone + mildly skewed lowers + 45° skewed uppers = a suspension that won't want to move at all.


Norm

[mugzilla]

Assuming that you can live with either of the roll center heights, it would be an alternative to a Watts link and either the upper or lower arms because you'd have to remove either of those as well.

A wishbone + mildly skewed lowers + 45° skewed uppers = a suspension that won't want to move at all.


Norm



I'm happy with moderate traction as I'd rather spin tires than shock the driveline . I could put in stiffer bushings but I thought the old stuff(100,000 mi.) would launch better.

I'll be happy to turn a 14 .

[shmoov69]

Actually, your '58 Chevy (car) would have had a 3 link, the upper being offset to the passenger side of the pumpkin, with a panhard bar.

Good grief, how do I remember this stuff??

Shiny Side Up!
Bill

Nope, that's a 59. My 58 has a stamped steel A arm thingy (wishbone) on top of the pumpkin that goes to two mounting points on the frame X.

[ProTouring442]

Nope, that's a 59. My 58 has a stamped steel A arm thingy (wishbone) on top of the pumpkin that goes to two mounting points on the frame X.

Damn.. I would have list a bet on that one... maybe I'm getting old?

Shiny Side Up!
Bill

[shmoov69]

Maybe the cars, but not the wagons