been dreaming of an a arm/ford beam hybrid

[englertracing]

Just a little day dream I had.


A few years ago I saw a playtech offroad car which used an I beam like a Ford truck but fabricated from tube. Kind of the start of the long travel sand car craze.

I looked at it and thouht.
Hmm what if you built an a arm setup right weels lower controll arm starting left of the cars center line. And upper arms starting in the center of the car.

Then I was talking to someone who thought a single long arm with a very low pivot could be the ideal road car suspension (i think not because cambere gain isn't great enough.

Anyways It made me think what a crosses lower and center pivot upper would do on a road car.
So I ran it throuh a suspension analyzer program (that I don't really know how to use yet) and it seems the instant centers stay more stable than a conventional setup. When making a left turn the right wheels instant center raises with body roll and the left wheels instant center falls. Opposite of a conventional sla. I guess typical of an I beam single arm?

Anyways what would any of the effects of a rising outside wheel and falling inside wheel instant center be good bad or unknown.

[flyingwedge]

>>Ok, it woun't have enough roll camber gain, "but" if it had more roll caster gain, this woul help accomplish a better tire footprint. Aluminum construction and perhaps a "Vette" composite/transverse leaf ? A leaf is easy to make "rising rate". Because they load as an "S" wave, in turns, they reduce roll. Onward, flyingwedge.

[englertracing]

Okay I hear you on the cambered gain because the ratio of upper arm to lower arm isn't enouh Imagine the Lower pivots were Verry far to the opposite sids like.... Almost in the way of the other wheel when turning.

Still not enough cambered gain
And what about the effects of the roll centers
Please excuse the terrible spelling at work and posted on phone.

[flyingwedge]

Okay I hear you on the cambered gain because the ratio of upper arm to lower arm isn't enouh Imagine the Lower pivots were Verry far to the opposite sids like.... Almost in the way of the other wheel when turning.

Still not enough cambered gain
And what about the effects of the roll centers
Please excuse the terrible spelling at work and posted on phone.

Seems like the single, extra long, lower arm would have minimal roll center migration. These theories can be checked-out with a string or paper template mock-up. What if the lca pivot was hooked to a torsion bar ? This should generate high roll stifness. Onward, flyingwedge.

[englertracing]

Okay I hear you on the cambered gain because the ratio of upper arm to lower arm isn't enouh Imagine the Lower pivots were Verry far to the opposite sids like.... Almost in the way of the other wheel when turning.

Still not enough cambered gain
And what about the effects of the roll centers
Please excuse the terrible spelling at work and posted on phone.

Seems like the single, extra long, lower arm would have minimal roll center migration. These theories can be checked-out with a string or paper template mock-up. What if the lca pivot was hooked to a torsion bar ? This should generate high roll stifness. Onward, flyingwedge.

I don't follow... Do you mean this would some how increace chassis rigidity? Or do you mean high roll spring rate to spring bump rate?

[flyingwedge]

Okay I hear you on the cambered gain because the ratio of upper arm to lower arm isn't enouh Imagine the Lower pivots were Verry far to the opposite sids like.... Almost in the way of the other wheel when turning.

Still not enough cambered gain
And what about the effects of the roll centers
Please excuse the terrible spelling at work and posted on phone.

Seems like the single, extra long, lower arm would have minimal roll center migration. These theories can be checked-out with a string or paper template mock-up. What if the lca pivot was hooked to a torsion bar ? This should generate high roll stifness. Onward, flyingwedge.

I don't follow... Do you mean this would some how increace chassis rigidity? Or do you mean high roll spring rate to spring bump rate?

>> I suspect negligible on increasing chassis rigidity, but I see high roll rate to spring bump. This should allow a very short torsion bar, per the leverage ratio. I like the concept of transfering most of spring load to opposite side of vehicle, without an anti roll bar. Also, add positive caster angle at the inner pivot, for enhanced roll caster gain. What if ? Cheers, flyingwedge.

[englertracing]

Im thinking I might try this If I can't find any more cons to a setup like this. If nothing else than to do something different.

[flyingwedge]

Im thinking I might try this If I can't find any more cons to a setup like this. If nothing else than to do something different.

>> For a "cleaner" look, you might put the torsion bar inside the frame. As I recall, sprint cars used to do this-eons ago. Good Luck, flyingwedge.

[englertracing]

Most Sprinters still run torsions!
The drivers seem to like it better.
Around 3/4 of the cars in the field will be torsion on asphalt and about 90% torsion on dirt.
Sometimes you see a mix of torsion and coil on diferent corners of the car.