Have the corner pots mounted like the front of Mysterion (to reference a HAMB car) or on the frame with a link bar acting on the axle, allowing length tuning. I'd conside torsion bars. They seem to provide a smoother ride, and could be packaged under p***enger area for low CG. Lots of bars to chose from using circle track parts, and adjustable links. https://wahlracing.com/product/torsion-bar-kit/ Could pair them side to side as you have, with the control ends vertical to help with bleeding. and servicing. Green is TB frame section. Brown are your control reservoirs. Black are torsion bars. Red are links. There is always room behind the seats for vertical stuff, and if a roll bar is part of the design, this could be part of that structure. This is true even in a single seater. The torsions are occupying exhaust space for a front engine design, but that could be outside the frame or careful packaging can work this out. I used 4 torsions in case you want to have individual controls (or rising rate or soft/firm springs), but if the arms and valving could be sized, just 2 torsions would work, provided the springs can handle one side's F and R weights.
Hey, Dawie; Thanks for posting. I read virtually everything you post here & elsewhere when I can find it. I don't comment much, since it's my consideration(s) that in order to ask intelligent Q's, you've got to understand the concept(s) to start with. You *always* cause me to think, sometimes to the point of headache... . You don't think outside the box, because around you there is no box, & not even much definable space... . Yes, I do like it... . I can see studying & using the Packard system under a ~'53-> Stude cpe/hrdtp. Since they have a very flexible frame, & a not-so-stiff body structure. &, iffen I'm reading correctly, there'd be no springs or shocks in the normal position(s), so that'd open that space up for other things, including suspension & steering changes. Am also thinking that adaptation(s) could get "interesting" - *if* the parts could be found anymore... I'm not so much interested in achieving a level-car-at***ude; as a really good ride or ever-increasing lousy roads(& then of course, there's ice/snow/gravel/etc conditions), cornering ability whether for fun or out of necessity, & just road-holding in general. I don't drag-race, but having the rearend loose is only fun to a point. I'm told the Panhard was great for lousy road surfaces(railroad crossings, potholes, washboards, etc) the faster you went. Same for the Citroen(Dm n SM ?). IDK, as I've never ridden in any of them. Thanks for the pics n drawings. What would help me, at least, would be some real-world calcs & dimensions applied to say a Tbucket, & also something like the Stude. I do have trouble w/visualization(s) of the hyd crossing concept(s). Incl body-roll(ing) thru corners(like say, auto-crossing events). I'm also not a fan of trailing-arm suspensions, at least when they're short n tight, like say an ACVW. Also applying this to different suspension-styles, like say a Jag ifs/irs or a typical american 50's front suspension & maybe the gm 2-link, or better a 3-bar type rear suspension. Have enough trouble & difficulty keeping typical suspension antics in mind, much less these. I have a very looong way to go, just to catch-up to the level of this thread... Again, thanks for the postings. Marcus...
I hit like to acknowledge your contribution, but I'm really not sure what I'm looking at here? I think the four torsion bars might be confusing me. The bars are longitudinal in the car? Are the brown the "slave" bags in my central unit?
The 2CV as produced in stock form couldn't/can't have a (numerically) high ratio because it is designed for relatively large and variable cargo loads. The suspension can't tell the difference between compression from a bump and compression from a large load. You don't want to force extend the front when a large load compresses the rear because that will just make it seem to sag even more. The advantage is that it allows various suspension bits to have arcs of motion that would otherwise be impossible given realistic packaging constraints. Spend some time playing with a 4-link calculator. IFS suspension design is basically the same but with more variables.
Yes, between the frame rails, under the p***enger compartment. Yes, the reservoir/main fluid cylinder is brown.
Loads are a matter of spring rates. The motion ratios are about fitting that lot within the alloted part of the frame. Achieving a "dampable" motion ratio around 0.66:1 would mean the "pots" would need to be three times the length they are on the 2CV, and move back and forth three times the distance. Finding room for all that would have been difficult. I think I've partly cracked that one, though, in Post 57. It comes down to very large-diameter dampers.
Are you talking about the ratio of force transferred from front to rear or ratio of motion of the wheel to the pot? I thought you were talking about force transfer.
OK. I think two torsion bars would suffice — or even only one. The only way I know of to do rising rate in a torsion bar is to have some kind of clamp or clamps somewhere along the length of the bar, which engages with a stop at some angle of rotation. At that angle only the free end of the bar is active i.e. the bar is stiffer. Using two or more short bars joined end to end would eliminate the possibility of clamps slipping on the bars, and enable the use of bars of different diameters for the respective stages, at the cost of not being able to move clamps fretlessly, as it were, along the length of the bar. Either way, because of the motion ratio (short link arms) and the fact that the damping is in the "slave" bag, a surprisingly small torsion bar should do the job — provided it doesn't break. So, we've got two bars, meaning they can be tucked up close to frame rails, out of the way. At one end they're anchored to the frame; at the other each has an arm, with a fulcrum on the frame, acting on a "slave" bag. All that would be redundant, as bigger ac***ulators could be plumbed in wherever we want them, unless we make a few modifications. Turn the arms into bell cranks, one with a short vertical arm pointing up and the other with a short vertical arm pointing down, and link these vertical arms with a diagonal link. That way, any motion of one bell crank forces the same motion in the other. And, because the bell cranks' motion will always be the same, there could technically be only one torsion bar for the two of them — though having two might be better for loads on the diagonal link etc. The diagonal link might again be in the way of drive train, exhausts, etc., but that can be solved by using a two-piece link with an idler arm. Or it might not be in the way, depending where it's located. The idea is to isolate roll motion and subject it only to the stiffer springs, while letting all the springs work in series (lower rate) in other ch***is motions.
Thinking about interconnecting torsion bars — and that's something I did a lot of when I had the Morris Minor, with its stock longitudinal front bars — a thought which occasionally snuck across was the idea of using an actual rearend differential between front and rear bars. It seriously flitted through because surely it can't work, what with partial rotations and backlash and what not, but mightn't it work? Torque-wise, that Stude is about 3000lbs and probably fairly well balanced, so something around 750lbs per corner. To keep it simple, let's ***ume 12" arms at the ends of the torsion bars, so the differential sees 750lb.ft. (static) on each side. Compare that to a typical rearend application where the differential might see 3000lb.ft. in first gear. Even with impact loads and lateral weight transfer, it's perhaps not that far-fetched. Still, the perennial problem with a torsion-bar-based system is damping, because the ends of the torsion bar are physically far apart, and having the end of the bar ordinarily anchored to the frame float on something else means the frame isn't an ideal place to mount the dampers. Notwithstanding that was how Packard did it. At the very least damping rates would be a compromise, which might not really be right for any motion mode, especially if you go chasing performance. It's solvable — at the cost of another parallel layer of complexity.
Think of the 'helper' or 'overload' leaf springs. But with torsion bars. One is light, handling empty car weight and 'soft'. another is staged so when a big load or heavy bumps are encountered, they are 'firm' and increase spring resistance to movement. Yes, a clunk at point of engagement. You seem to want a bag above and below so there is fluid displacement in each direction, but a cylinder with a rod through the center with fluid above and below (like a shock but without the valving) would package as easily if not more so.
I reckon moving a clamp or two up and down a torsion bar would be a compact and simple way to do that? The clamp would sit inside a cage or housing which allows the clamp to rotate a bit, until the clunk you mention happens. That could be cushioned with urethane pads etc. The cage could be movable along the frame rail etc. I need the "slave" bags to move in parallel, not against one another, which I agree would have been a lot simpler. If the left compresses, I need the right to compress the same amount, and vice versa. It's more ****ogous to an anti-roll bar of virtually infinite stiffness. The bags themselves are single-acting, because they are only net-loaded one way.
Fluid is acting simply as a force transfer, right? There are multipliers by sizing the corner cylinders and main cylinders along with the acting levers, with damping using the pressurized air above the bladder. Bladder at each corner or in the main? Having LF pressure (road bump) increase and wanting LR to decrease (fore/aft transfer), while RF also increase (antiroll), yes? Sizing would be critical then, so that both reactions are as planned. Would this be easier with a pair of cylinders at each corner, one connected fore/aft and the other connected side to side? Would the mains even be needed? Simply a large reservoir that is reserve and could be pressurized by a pump? Pressure to be weight of entire suspended load and 110% of any anticipated loads due to m*** and acceleration? Sized up or down depending on those multipliers? It would be nice to have the fluid circulate so heat from work and any nastiness in the system is returned to main reservoir for storage and filtering. So the springs are serving as additional load bearing and rising rate resistance? Can they be removed completely?
Here's a less-theoretical idea: there are several late-model US full-size trucks which have torsion bars around 55" long. Those trucks also tend to over twice the weight of a '53 Studebaker. The idea is, get hold of two complete front suspensions off such trucks, one 4x2 and one 4x4. Turn the latter back-to-front and use it as irs. The frame ends of the torsion bars get connected using the aforementioned differential idea: I'll elaborate on that later, as I might need to draw or model something. Those humungous torsion bars would be just the thing to get serious roll stiffness. Some models have different bar diameters on different versions. You want the fattest ones, the closer to 1¾"Ø the better. Of the SLA suspension you're primarily interested in the torsion bars and the lower control arms. You could either use the upper control arms or measure the geometry of those, plus the shock upper mounts, with a view to fabricating your own. Combining the 4x2 lower arms with the stock Studebaker front upper arms might produce a perfectly respectable SLA setup. To ensure decent hook geometry you'd want to alter the 4x4 (now rear) upper control arms' pivot axes to define a pitch instant centre somewhere below and behind the zero-squat line. In practice that'd mean tilting the upper control arm front-up by around 10°. The idea is that the pitch instant centre migrates under acceleration to sit on the zero-squat line after the rear of the car has risen an inch or two, and then stays there as long as you keep your foot in. You'd set up the now-irs for zero camber and toe under those conditions. Of course there would be a lot to figure out, like steering, brakes, wheel bolt patterns, etc. You'd probably get huge disc brakes with the suspension, which is good, though you'd need to rig a handbrake/e-brake. And those brakes might reflect a 6- or 8-lug bolt pattern, which might limit wheel choices to a look you don't want. The hubs would most certainly be bolt-on units, and there might be subs***utes which offer better bolt patterns. Damping: might as well use the shock mounts/locations provided, but ideally a custom damper system would be advisable. It's simpler than you'd think: I'll draw something.
The purpose of the additional central unit is not to provide additional spring rate under load, but a much-reduced spring rate whenever the left and right wheels are moving in the same vertical direction, i.e. under all conditions except roll. It doesn't kick in under load; it kicks out under roll. The springs are soft, far softer than the ac***ulators at the corners. The reason I incorporated rising-rate springing into my illustrative model is that the opportunity to separate out roll allows the remaining modes to be as soft as we want, which opens up a number of possible practical problems, from a low stance being impractical due to anticipated drop under load, to frequent bottoming-out over bankings and whumps, etc. It makes sense to have the overall spring rate rise rapidly after the first inch or so of travel.
Thanks, Dawie. Appreciate the time, response, & answers. I gotta do some serious "cyphering". . Right now I got too much on my plate, & am happy to ponder this for abit, as a break. Eventually, also gotta dig out my suspension/handling books to review(again & again). I'm familiar w/the Cad Eldo IRS front torsion bar system, although I don't have one laying around anymore. Also the front IRS from my '99 ford ranger 4x4 pu, which still could be cutout/hacked-off for future use. Got a lot more Qs about this, but want them to sound almost intelligent, if possible. So's I'll have to ask later, to try to build a foundation of (my) understanding(s). & expectations relative to hoped-for results. ??? Also gotta go back to the 1st Packard illustration & study it some more. Torsion bar twists/reactions don't look right to me, yet. My eyes might be in backwards... . Beginning to think hydraulics would be easier to fab-up a system from scratch... Marcus...
Here's a way to do interconnected damping, should the need arise. It becomes an issue with torsion bars, for the reason I mentioned in Post 71. This might also be of use with interconnected leaf springs, depending on how the springs are configured, as well as interconnected air. It isn't necessary with hydraulic interconnection, as we can stick valves in wherever we want, nor with most coil spring arrangements. This would also allow silly motion ratios to be entertained as regards the springs, whatever they might be. In fact this might be the simplest way to damp a 2CV or Torsion-Level Packard properly.
I just can't leave this stuff alone. It's been a year since I posted Post #58. I'm back to chipping away at that idea. As I said, the problem always tends to come down to damping, and one of the situations where that is an issue is where the motion ratios are extreme, as is the case with the 2CV's pots. In Posts #35-38 I had got into the idea of designing with separate damper components like shim stacks instead of complete damper units. So now the idea is conceptually turning a coilover shock inside-out, by putting a spring inside a large damper. It starts to look a lot like a 2CV pot turned into a damper: As this is ****ogous to the roll-control interconnection shown in Post #58, the requirement was for a high spring rate and small spring deflection. I require a wheel rate in roll of 260lb/in over a one-way wheel displacement of about 1½". At a ***ulative motion ratio in roll of 0.25, that means a spring rate of 4160lb/in over a spring stroke of about ⅜" in each direction. Though that can be achieved with a coil spring, the spring on its own might be almost 10" long. By contrast, a stack of off-t******lf Belleville washers less than 2" tall could provide the same rate and stroke. The entire ***embly is about 8" long, or 13" including the rubber pitch-control springs — which are off-t******lf rubber helper springs modified slightly — significantly smaller than the Citroën pots. Damping: Taking a common Ø46mm high-performance monotube damper as a baseline, doubling the piston diameter, i.e. quadrupling the piston area, would produce the same oil displacement over a quarter of the stroke. The damping force over that stroke would however be halved, and so the unit would need to be shimmed quite stiffly. The rubber springs would seat against successive frame members and resist pitch only. Due to the motion ratio they would effectively be very soft. Moreover, rubber springs have the advantage of self-damping via material hysteresis, so soft ones wouldn't need additional damping.
"Lateral" interconnected suspension has been around for over 60 years in Formula Vee race cars They used this mechanical system to prevent "Jacking" from swing axle suspension.
A Z-bar is basically half of a Packard Torsion-Level setup turned 90°. I believe that's whence the irascible Australian I mentioned in Post #12 derived his username. Mercedes-Benz used a horizontal compensator coil spring on some swing-axle models to the same end, before developing the low-pivot arrangement which was their mainstay into the '60s.
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