- #1
Tom Rauji
- 45
- 6
When I read pages or look at calculators for car suspensions it seems they have things wrong. They seem to consider both the upper and lower arms as a straight line intersection where the tire contact patch effectively "pushes" through the intersect point. I'm trying to understand the forces at work here. If the upper arms (UCA) had a net pushing force, I would agree. The UCA's however pull. Only the LCA's push forward.
Wouldn't both upper and lower arms have to push with equal forces to plot an effective single net force line crossing where those arms intersect? It seems to me since the upper arm pulls backwards, it does not have the same effect as the lower arm and cannot simply be plotted to a single point where they cross. They are separated a fairly large distance on the chassis and both ends swivel on joints.They do not joint at one point.
This is a rear axle in a car. The axle is driven by a ring and pinion gear. The axle is anchored only by four control arms, I'm looking at just one side. If I assign some arbitrary torque on the axle, like 1000 pound-ft, the upper arm would be pulling backwards and the lower arm alone would push forward. Wouldn't the forces have to be treated that way, instead of treated like a sum at a point where an imaginary extension of the lines would meet?
I can't get my head around this. Can anyone help me with the forces in this system assuming some normalized torque at the axle that is working against the housing along with the normal reaction to the tire thrust on the road?
This is a link to an Internet example of an instant center plot.
http://performancetrends.com/graphics/4 Link Plus Main.gif
Wouldn't both upper and lower arms have to push with equal forces to plot an effective single net force line crossing where those arms intersect? It seems to me since the upper arm pulls backwards, it does not have the same effect as the lower arm and cannot simply be plotted to a single point where they cross. They are separated a fairly large distance on the chassis and both ends swivel on joints.They do not joint at one point.
This is a rear axle in a car. The axle is driven by a ring and pinion gear. The axle is anchored only by four control arms, I'm looking at just one side. If I assign some arbitrary torque on the axle, like 1000 pound-ft, the upper arm would be pulling backwards and the lower arm alone would push forward. Wouldn't the forces have to be treated that way, instead of treated like a sum at a point where an imaginary extension of the lines would meet?
I can't get my head around this. Can anyone help me with the forces in this system assuming some normalized torque at the axle that is working against the housing along with the normal reaction to the tire thrust on the road?
This is a link to an Internet example of an instant center plot.
http://performancetrends.com/graphics/4 Link Plus Main.gif