Mumford links & Mallock TAM info.
Mumford links & Mallock TAM info.
(OP)
Looking for any sites, books ect that will inform me of both Mumford type axle location and Mallock "trailing arm magic" theory.
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Mumford links & Mallock TAM info.
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RE: Mumford links & Mallock TAM info.
I cringe, however, when the word "theory" is used in regard to an engineering problem. Hopefully, by the time we engineers receive the problem, the theories have already been proven. As for trailing link suspensions, I would assume the goals are a minimum of links (while maintaining the requisite strength with minimum weight) and a minimum change in geometry within travel limits. (The strength/weight comment is necessary as someone is sure to point out that a Panhard, with a single trailing link solidly attached to the axle housing, is all that's required. True, but that single trailing link ends up being quite heavy.) So, I would recommend that which is commonly used with oval track cars (NOT NASCAR)in the US: 2 symmetrically positioned lower trailing links and a 3rd trailing link above, positioned as close to the car centerline as possible. If the 3 links are all parallel to the car centerline, in plan view (the desirable situation, from a weight viewpoint), a Panhard rod is also required, of course. The IC should be on the no squat/no rise line and all links should be as long as possible. This simple design was used on the Jaguar C-Type (early non-IRS versions), except that the single upper link was offset to the right to dynamically cancel the unloading of the right rear by driveshaft torque.
Why do manufacturers opt for more complicated designs for production cars? As Natalie Wood was told in that movie about the life of the famous American stripper, Gypsie Rose Lee: "You've gotta have a gimmick."
RE: Mumford links & Mallock TAM info.
RE: Mumford links & Mallock TAM info.
http://www.clubcobra.com/t41392--1.html
Personally, I don't see that much value in locating the rear RC any lower than that achievable with a simple Panhard rod. If the Panhard is long and nearly horizontal, RC height variation is minimal. And, of course, identical tire loadings can be achieved, in either case, with an adjustment of front/rear roll stiffness values. About the only argument I can see (for a lower roll axis) is that it can improve the driver's "seat of the pants feeling." This was the argument fifty years ago, anyway. But, with the high spring rates required by modern aerodynamics, I doubt if this is still a valid reason for such a small change.
In my Google search, I noticed that someone had been critical of a new edition of a suspension book because it didn't include the Mumford design. I would point out that the Millikens also didn't mention it in "Race Car Vehicle Dynamics." Rather than being critical of the omissions, I applaud them!
RE: Mumford links & Mallock TAM info.
Its's more of an interest thing than practical use, my car has four equal length trailing arms and a Panhard. I've seen the question on other forums and would like to know more, with a view to maybe using them in a future project. I've asked the question on here because all the other forums I have seen haven't been able to give any more information other than the above pictures.
RE: Mumford links & Mallock TAM info.
Dixon's book includes a description of the Mumford linkage. You should be able to find a shareware program on the web that analyses 4-8 bar linkages. Using this you should be able to invent a linkage with any desired RCH characteristic.
Cheers
Greg Locock
RE: Mumford links & Mallock TAM info.
RE: Mumford links & Mallock TAM info.
Perhaps you need to sit down with a 2x4 and whittle yourself another crossmember. (Hope you can take a joke about that wood frame in the Morgan.)
RE: Mumford links & Mallock TAM info.
How can optium link lengths / spacings be obtained to implement "TAM" or anti squat?
RE: Mumford links & Mallock TAM info.
I'll leave the "magic" to the magicians.
RE: Mumford links & Mallock TAM info.
Do you know of any diagrams on the web for reference to your description? I'm particularly interested in getting the geometry correct for a car with 4 trailing links and a panhard to locate a beam axle.
John
RE: Mumford links & Mallock TAM info.
Thought as well of having 4 links (forward), but on the same side of the axle, in this case below the axle.
What do you think guys?
RE: Mumford links & Mallock TAM info.
tommog: There's no requirement that upper and lower links be the same length. The general rule is that all links should be as long as possible (within the limits of practicality) to minimize IC movement with suspension deflection.
And, yes, the "lower" link could actually be above the axle centerline (or the "upper," below). It's only necessary that sufficient vertical spacing be maintained for structural integrity.
Finally, I've got to ask a question that's been bothering me throughout this thread: Why fool around with these "trick" suspension schemes for an antiquated rear drive (the beam axle) when, for the same fabrication effort, you can have an IRS? I consider the early Jaguar C-Type to be the ultimate in beam axle competition car suspension, but even this was quickly replaced with the IRS C-Type. Unless the sanctioning body requires the beam axle (e.g., NASCAR) or IRS components lack the required strength (e.g., NHRA Pro Stock), I see no reason to fool with the beam axle.
RE: Mumford links & Mallock TAM info.
I gather Mallock used their "TAM" theory to adjust link bar location points to good effect. Its this theory that I am ytying to discover.
All suggestions welcome.
RE: Mumford links & Mallock TAM info.
RE: Mumford links & Mallock TAM info.
tommog, the upper links can be quite short, actually. Perhaps the solution would be to determine the maximum jounce/rebound which would accompany fuel load variations, etc., make a drawing with a proposed upper link length, and then see if the rear U-joint angles fall within acceptable limits. The other consideration, of course, is whether there is sufficient length to reliably locate the IC, given foreseen ride height variations.
RE: Mumford links & Mallock TAM info.
BTW by how much does the pressure on the coil spring rise when you move it 1 inch to the inside (direction differential).
Billy, actually I put roughly 350 BHP and 400 Nm through the axle ... hence, everything must be rather solid
RE: Mumford links & Mallock TAM info.
And, I'll bet you're running either a spool or a limited slip. Right?
RE: Mumford links & Mallock TAM info.
Or is my conception of the C type beam axle layout completely wrong?
John
RE: Mumford links & Mallock TAM info.
Many of those who post here have mentioned that they own a copy of the Millikens' "Race Car Vehicle Dynamics." There is a companion book for RCVD, a student workbook. As you might imagine, RCVD is often used as a college text. I used it when I taught a graduate level engineering course in vehicle dynamics. This workbook includes contributions by myself and a Norman Smith, who was employed by Jaguar at the time of the C-Type development. Mr. Smith provides the setup equations for equal tire loading and explains, also, that much of the suspension work was empirical in nature, which would account for the multiple adjustment holes you describe. My contribution was to take Jaguar's work a step further and provide equations that would allow both equal tire loading and no squat or rise on acceleration.
Unfortunately, the student workbooks first published did not contain the answers to the questions posed. These were reserved for a "teacher's copy," which was published in very limited quantities. Now, however, when you order the student workbook (more correctly, "Race Car Vehicle Dynamics; Problems, Answers, and Experiments"), the answers are included and errata corrected. Unfortunately, my note to the Millikens for the addition of a multiplier, to my equation, to account for unsprung weight, did not make it into print. The final term of my equation, at the bottom of page 204, should be multiplied by M/(M-m), where M is the sprung mass and m the unsprung.
I strongly recommend the purchase of both books. (No, I don't make a penny out of this.)
RE: Mumford links & Mallock TAM info.
Many thanks.
Regards,
John
RE: Mumford links & Mallock TAM info.
Would something like that help?
Norm
RE: Mumford links & Mallock TAM info.
BTW Bill I run a limited diff. , but the major problem with the back axle remains the limited axle travel. Actually an other one for the experts in math.: When the engine churns out 400 Nm, how does this divide on the upper and lower links under acceleration (to make the bracketts with the correct material and size)?
Take care
RE: Mumford links & Mallock TAM info.
RE: Mumford links & Mallock TAM info.
Reading about spherical joints and PU bushes it seem to makes sense to use one end PU and in-line spherical (what ever it means) joints (I think the English say as well 'rose joints') on the other side. Does it matter where you fit the PU part -axle or chassis? What do u reckon is the mimimum size you need in my case.
Thanks guys