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Discussion Starter #1
Hey Guys,

I'm guessing that this has been asked and answered 100 times and I apologize if it has as my searches didn't bear any fruit.

Due to my frame geometry, a 3 link would be much easier to construct. I'm wondering what you guys feel would be the performance difference, if any?

FYI, 1970 Ford F-100, BB Ford (500-600HP), Mustang II up front, custom frame sitting pretty low on air bags.

Thanks in advance,

Wes
 

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Discussion Starter #5
Hey Billy,

I've been through your blog but am having troubles with terminology and such. I understand the physics pretty well (I'm an Engineer) but am still getting used to what's what. I'll dig into it this weekend and post back with any questions.

Thanks again guys,

Wes
 

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3 link

Hey Billy,
I'm building a Model A highboy style w/350sbc, 350 combo. probably a 9" or 8.8" rear w/stock transverse spring behind axle setup. Can I build a suitable 3 link with the stock trailing arms (maybe beefed up) as the bottom links and a tubular odd link on top? how long is long enough? It's just for street use..300to400 hp max. thanks, Mike
 

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Philippines Cowboy
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msherrow said:
Hey Billy,
I'm building a Model A highboy style w/350sbc, 350 combo. probably a 9" or 8.8" rear w/stock transverse spring behind axle setup. Can I build a suitable 3 link with the stock trailing arms (maybe beefed up) as the bottom links and a tubular odd link on top? how long is long enough? It's just for street use..300to400 hp max. thanks, Mike
Links must be pivotable at BOTH ends.
 

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3 link

so if I remove cast/forged piece on rearend side and replace with steel tubing welded to inside of tube to incorporate rod ends? and one on the front as well? won't the upper link take the abuse/torque and the lowers just for locating? do they need to intersect at a fictional point somewhere?
 

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Philippines Cowboy
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msherrow said:
so if I remove cast/forged piece on rearend side and replace with steel tubing welded to inside of tube to incorporate rod ends? and one on the front as well? won't the upper link take the abuse/torque and the lowers just for locating? do they need to intersect at a fictional point somewhere?
If it's just for street use, it would probably be best to simply adapt the newer axle assembly to the stock suspension.
 

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Discussion Starter #10
How does this look?



How does one go about deciding on what plane to put the 3 link on to counteract the differential rotation about the X axis?
 

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Philippines Cowboy
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Wesley J said:
How does one go about deciding on what plane to put the 3 link on to counteract the differential rotation about the X axis?
Quite impressive, but what has a 130 inch wheelbase and weighs only 3500 pounds? :)

Go to Page 6 of my blog:

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

for a spreadsheet on positioning for complete cancellation.

You might as well complete your EXCEL spreadsheet by copying the JavaScript calculations from my blog. Nothing's hidden, though the internal documentation is missing. Just view the source.

If you have the 100% anti-squat line passing through the rear tire patch, my results won't quite agree with yours. The line actually passes a distance rm/M below, where "r" is the effective radius, "m" is the mass of the rear axle assembly, and "M" is the remaining mass.
 

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Discussion Starter #13
I cant quite make an sense of your spreadsheet Billy. Riddle me this; can you describe to me what the distance forward from rear tire input fields for the Odd link rear mounting point and symmetric link rear mounting points are defined as? Are they distance from axle center line?
 

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Philippines Cowboy
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I agree, "distance forward from rear tire" is not as clear as it could be. Suppose I change it to "horiz. dist. forward from rear axle centerline"? I'll go change it right now.
 

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Discussion Starter #17
Not too sure. I get a result of the following

VERTICAL DISTANCES FROM SHOP FLOOR TO FRONT OF LINK
odd link = 9.67
symmetrical links = 1.95
instant center height = 1.54

from this:

 

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Discussion Starter #18
I've also been working on a triangulated 4 link as it fits pretty well. Because I really have no idea what my CG height will be, I did the following sensitivity analysis:

As a note, I have a lot of flexibility in my upper link frame mount height but not as much at the axle. So, I fixed the axle at 2 different heights and then calculated the frame mount height to attain a 100% anti-squat.

Looks as though 3 mount points up front should allow me to tune it to the required antisquat:

CG Height/Axle End Height (in)/Frame End Height for 100% Antisquat (in)
16 17 16.25
16 19 18
17 17 16.2
17 19 17.9
18 17 16.13
18 19 17.85
19 17 16.08
19 19 17.77
20 17 16.03
20 19 17.7
21 17 15.97
21 19 17.63
22 17 15.92
22 19 17.56
23 17 15.87
23 19 17.49
24 17 15.81
24 19 17.42
25 17 15.76
25 19 17.34
26 17 15.7
26 19 17.27
27 17 15.65
27 19 17.2
28 17 15.6
28 19 17.13
 

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Philippines Cowboy
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I'd stick with the 3link for the driveshaft torque cancellation. You just need more odd link offset. With 26.5 inches of odd link offset, the symmetrical links end up horizontal. The odd link would be angled down at only 5.1 degrees.

(Don't be frightened by the extreme offset. This is similar to the Jaguar C-Type and the first Ramchargers' car.)
 
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