Pardon the sketchy drawing. I've been reading up on airbag set ups and the pros and cons of different rear suspensions. This popped in my head as a way to do a two link and allow the axle to freely articulate with relying on flexing arms. Basically just let the arm pivot at the axle with a long enough axis to prevent axle twist. I can't be the first person to have this thought and I'm sure there's some reason I haven't seen something like it. Thoughts? Suggestions? Links to "Simpsons did it first"?
Panhard bar is how most do a 2 link and get articulation, hell 50s torque tube cars were built that way with coil springs. Nothing really new. Watts links are the new thing... But if you were wanting to do away with the panhard bar, then you have to do a texas 2 link with the cross arm between the link bars. In doing that both bars move up and down with eachother.
This isn't intended to aid in lateral locating, just to keep the arms from binding when one wheel goes up and the other down. A panhard bar or watts linkage or such would still be needed.
The 49-50 Oldsmobile used rubber bushings and bolts on rear suspension trailing arms to allow articulation, simple and effective.
The bind is there but it also helps work as sway bar in some fashion. Without bind/resistance it would be like a rock crawler suspension. The 60-66 chevy trucks had the trailing arm suspension, it had links mounted to the frame, worked well and rode well. What made these work well is the length of the arm, so a few inches of movement of a wheel did barely anything to the trailing arms. Earlier types of cars, 1954 and down other cars all the way back to Model T's, used torque tube where all the articulation came from the torque ball and the links were fixed to the tube. This made no bind, the early traverse leafs did the work of panhard bar by using spring to locate the axle. This was actually one of the best articulating suspensions made hands down. Later style torque tubes used panhards and coil springs, still not a bit of bind anywhere to be had. If a full parallel 2 link was done, with these joints on the ends, the bad part is when one goes up it will pull the axle to that side of the vehicle, The other side must give a bit and go to the side also, that's where parallel 2 links get into a kink. Hence why no one puts them in for articulation. If you triangulate the arms, then you Aleve that issue due to arc of rotation. The link bars would almost need to float side to side travel at the axle attachment for it to work and not break things. Could this be done, yes, bearing trench and dovetail to keep the axle attached to the joint. Engineering this would be very expensive, but can be done.
From the Wiki "Watt's described the linkage in his patent specification of 1784 for the Watt steam engine." Like you said, nothing is really new. Mike
Where would the front ends of the bars be located? Straight in front of the axle brackets, or close together in the center?
I’m thinking close in the center. Basically truck bars but move the twist from the bars to the bushings. The Olds setup Junkman8888 referenced seems to achieve a similar goal. Also doing more searching I’ve run across the 2-links that have secondary links running from the main bars to the top of the axle, all with Heim type joints. I knew I’d seen something like that in the past but maybe it’s fallen out of favor as I only found one example? My search terms may need help too.
Basic thought on the 'big honking bolt'. No matter how tight you have them they would come loose with the twisting of the suspension.
If you have upper bars connecting all to the same forward pivots, you’ve built ladder bars. They are common and actually articulate well if the front points are close together. If wide apart you will have bind.
If the joints all have rubber bushings or Johnny joints or similar wouldn’t this style ladder bar allow axle movement without bind even if they were close to parallel?
This will still have a bind. A rear axle articulates beyond just rotating around a central axis that's parallel to the length of the car.
No. A rubber bushing will have some compliance to alleviate the bind, but it will still have more bind than a multilink suspension with compliant bushings at both ends. Parallel linkages will twist as the axle rotates around the longitudinal axis of the car.
Not a triangulated 4-link, still only two pivots at the frame. The axle brackets have one connection at the bottom and one on top. The bar that is connected to the top of the axle goes to a point on the main bar. You still technically wind up with four separate bars but the upper bars are connected to the lower bars instead of the frame. you’d still have the disadvantage of pinion angle changing but it seems it’d let the axle twist more longitudinally than ladder bars or a truck arm set up? Only advantage I can see over a four link is that it takes up less space.
lol. I had to do a three view sketch and sort out what moves where to get your point. My plan for my Chevy if I want to drag the bumper is either truck arms or triangulated 4 link since the car already has a g-body, I think, axle under it. Spring plates were added but the upper mounts are still there.
The anti-roll effect that you get with truck arms is actually a bonus. I can't work out why you would want to remove it.
My stupifyingly flexible Jeep suspension had front main lower links, with shorter links attached from the lower links to the axle top. It had rubber in all four positions on the axle ends, and Johnny Joints in the other four positions. It was easily able to drive past the 1000 mark on a 30° RTI ramp, and right off the end (which took a forklift to put it back on).
No parallel 2-link systems that have rigid connections belong anywhere but a drag strip. Truck arms only work because they almost meet each other at the leading end, have rubber bushings there, and the arms themselves twist substantially. Parallel 2-link systems with rigid connections can lead to exceptionally dangerous oversteer, as they turn the entire rear suspension into a rigid swingarm, and can leaf to bracket breakage over time.
I wouldn't even use them on a drag strip. Modern competitive drag cars, don't use Ladder Bars. Historical Reenactments don't count. Some people like doing things "wrong."
The rear under one of my parallel lower control arm cars has a fabricated torque arm with a shackle up front. Basically it's like two ladder bars so close together that minimal deflection allows plenty of articulation. Note it also acts as a driveline loop. Easy 1.30 60's and lots of pics with the front end about 3 feet in the air with this setup... Grant
This really works great. Simple, cheap, equal traction, and no bind. Anti squat and anti dive. The off center bar equalizes the frame twist and loads the right wheel. This is the latest version but I have used several variations. I did a thread on it.
GM truck arms are I-beam shape. Which allows twist without needing the full compliance from the rubber bushings alone. Tubular arms, either round or square/rectangular have significantly higher twist resistance. Forcing the compliance at the bushings. Rubbrr bushings can mask a lot of bad designs, especially if limited suspension travel.
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