Using a model a rear spring on a early ford rear with typical shackle arrangement. This is on a car racing with a prewar group in sportscar events. The driver feels like the rear is moving side to side under the car. The axle is located with the spring on top and wishbones from outer end of the axle to the frame with spherical bearing ends. A couple years ago when I was the driver...I thought the same thing. I put on a panhard bar as level as possible and admittedly it was short. It went from a bracket on the dif. to a bracket on the frame, not really as long as would normally be the case. It felt like it bound up the axle and had no suspension. I took it off and now the new driver wants to try it. Does anyone have an idea why it might bind up the rear? Or if a panhard bar will work at all? Thanks in advance!
As long and low as possible and you'll need to do more than use convenient bolt-on locations. Fabrication and welding will be needed. A panhard is always a compronise. A watts link would be better. The really short bar and tight arc of movement causes your problem.
Panhard should work with a properly loaded rear spring, i.e. 45° shackle angle. Bar should be as long as possible, pivot points level, bar can have bends to get around stuff. Left side of frame to right side of axle. On the other hand I don't see why the short bar would hinder as I don't think there is that much suspension travel ?
A 48 banjo had a panhard bar from the factory. Ive got one sitting here so if the engineers then thought it was beneficial theres certainly some merit to running one. I never have but I'm familiar with the side to side sway feeling
What they said... As long as possible, and parallel to the ground, at ride height (with driver, and fuel). Mike
With a deep arch rear spring it would be easier to mount a "Woblink" on the upper crossmember and it would operate better than a panhard bar. You can reverse it so the Ch***is mount is where center of the rear end is mounted instead. Arthur Mallock mounted it this way ^^^^ because his minimalist under-slung frames had no upper cross member. The bell crank must be vertical. You could safely use longer shackles with this method [too lower the car] as the shackle angle is not needed to locate the rear axle.
Many roundy round cars have a jacobs ladder sway bar mounted to and axle end. The short links are attached to the frame while the outer end attaches to a bracket near the wheel bearing. However, now that I look at it, it would be hard to mount on an original frame. A Watts link would be a better bet.
These only work on Left turn only [oval tracks] when mounted on the RR axle. Body roll from lateral acceleration pulls on the top arm and pushes on the lower arm. This converts "overturning moment" into downward forces on the RR tyre [increasing side bite] Turning Right would lift the RR type off the ground [not a good scenario] In normal suspension movement the Jake acts like a panhard bar BUT with a dynamic pivot point [Instant Centre] at the frame.
Most roundy round applications are not designed for and do not apply to the street, where a vehicle has to go in all directions equally well.
Totally agree with all points. That being said, if a panhard is set up to span the majority of the width of the rear, if you calculate the actual amount of lateral movement through the arc of suspension articulation, it's very negligible. Given the small amount of lateral motion, coupled with the realities of tall sidewall tires, primitive suspension and ch***is design, etc.... it has always struck me as a problem that exists in theory only.
Wow. Thanks to all that contributed to this post. Lots to consider as I never heard of the "Woblink" and will do some research. Some location devices are best for circle track racing only. I think due to existing restraints I will try a longer bar and see what happens.....Still not clear to me why a short bar locked up the suspension tho.
On the contrary, when using a Panhard bar the spring shackles should be as close to vertical as possible. The spring shackles already define a roll centre w.r.t. self-correcting roll motion unresisted by the spring, as I showed here. Adding a Panhard bar imposes another roll centre in a different location, leading to a conflict which can only be resolved through additional spring deflections.
This image is from Ned's original post mentioned above and I think it provides a great example of what's going on when the spring/shackles swing through their movement. Now, imagine you're looking at the back of the car going into a hard right turn. In addition to all that's going on with the suspension, I imagine the high roll center of the Model A axle is going to exacerbate the rest of the car pushing on the rear end towards the left. I would think this would result in an oversteer situation which might feel like the rearend is moving around, which it probably is as well. That said, you might be able to tune this to your benefit if you want a little oversteer to get the car into a turn, but that kind of advanced stuff is out of my pay grade! If it was me, I would want to lower the roll center as low as possible, which is counter intuitive with a buggy spring-style suspension. But that's way more work than it sounds like you'd want to undertake. I would study Ned's image and make some notes regarding your car and fab up a longer panhard bar. I missed any mention of shocks, but location, angle, etc could help/hinder your situation as well.
The Woblink is basically a Watts linkage. [where the arc of 2 arms cancel each other out] The problem with the conventional watts is usually clearance needed for the bell-crank so it is difficult to get a low RC [I have seen a watts mounted horizontally underneath a diff and work perfect] The Woblink "watts" uses the arc of the short arm to cancel the arc of the long arm so the bell-crank pivot moves vertically. The Woblink can only be mounted vertically, but it allows for low RC's and high frame mounts [which would be perfect for a Model A cross-member with deep springs. Do some research on Arthur Mallock [of the Mallock U2 fame] he managed to build the only compe***ive "front engined" Formula Ford. He has probably forgotten more about suspension design than most of us "mere mortals" would ever know.
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