Red Pepper Racing

Hello People,

i've been working on my suspension lately, and have all the parts just the way i want them, but im thinking of converting to a mumford type rear suspension because i have alway wanted to ditch the Panhard setup.

Ive seen that EPCRX has done the swap and maybe others ( Kirk ?? ) of you have also done it... so i was asking myself where can i get the stuff do do the conversion and what does it cost ? and do you guys have some info for me ?

for pictures of what i would like take a look at EPCRX's website:
http://www.shamrockm...crx_mumford.htm
( i hope you dont mind EPCRX ).
and info:
http://not2fast.wryd...s/mumford.shtml


Greetings Erwin.

I was debating on this type of setup also, but decided to try a modified panhard one.

yes i know ive read the post. i decided to try it

I know the Mumford likage is instead of a panhard rod. Does it also eliminate the need for a rear anti sway bar?

A sway bar is not required on any setup. The mumford linkage is a better way of locating the rear axle when it moves vertically, it eliminates the panhard bar.

how does that kind of setup react to roll or one side going over a bump with the other stable?

It looks like it will transfer that force to the other spring, basically always trying to keep the axle parallel to the frame.

I'm currently in the process of building one for my car. I have both bellcanks (almost) finished and hope to have it mounted in the car later this month.

Before I finalized the exact size and locations of everything I made a few line drawings on the computer and simulated a few movements like bump, roll, and roll & bump. I have always thought that this design kept the roll center from moving. Found out otherwise. I still think it's a lot better locater than a panhard bar by a long shot, even a little better than a Watts link from my point of view.

Basically, I found that the roll center will move. In a 2 degree roll it moved to the left 1.2" to the side and up 0.025", don't think I'll ever notice it. With 1" bump and the same 2 degree roll it moved less, only 1.07" to the side and less than .01" in elevation.

As for the links transferring weight, the only way they'll have any effect on that is depending on how high or low you arrange the roll center height.

Erwin, as far as who builds these, I've don't recall ever seeing any for sale. Best I could guess, so far anyway, is that every one is custom fabricated for the given application.

Jay

To the three guys asking questions about a Mumford device (above Jay's post), basically all it does is locate the rear axle laterally. It does nothing else. There is no change in rear roll stiffness. It doesn't take the place of a rear anti-roll bar. If the device was built properly, you could, in theory, jack up the car body, remove the springs, and either raise and lower the axle by hand, or tilt the axle up and down, and it should move freely, it just won't move from side to side.

There are three common devices used to locate a rear axle on a race car:
1) Panhard Rod
2) Watts Linkage
3) Mumford Device.

The advantage of the Panhard rod is that it is very light and simple, and it can be used to define the rear roll center height by having adjustable mounting holes to raise and lower the height of the bar. The disadvantage is that the axle will move laterally as the axle moves up and down in vertical travel. This can be minimized by having a rod that is as long as possible.

A Watts linkage gets around the problem of lateral axle movement, but has a draw back in that it can be heavy i.e. lots of unsprung weight hanging on the axle, plus you are limited in defining the rear roll center height (the roll center height is at the same height as the watts linkage pivot point?? I could be wrong, Jay or Kirk will correct me if that's the case.) 1stgen RX7's use a factory Watts linkage.

The Mumsford device is the best of both worlds. The axle does not move laterally when subjected to a bump or during roll, yet the linkages can be adjusted to locate the rear roll center height with a wide range of adjustment. The only drawback (that I can see) is the device has to be constructed very sturdy, with no binding of any of the linkages, or else it won't work properly, or you'll get snap oversteer from having the axle bind up solid. The unsprung weight is reduced since a lot of the hardware is connected to the chassis, not the axle.
Edited by Greg Gauper, 03 December 2006 - 11:48 PM.

Jay,
Ill try to fabricate my own mumford linkage the next couple of months. do you have dimensions and information about the fabrication of the link's for me ?
Or is it possible for you to build 2 sets? ill send you and PM about it today.

Greetings Erwin.



Thats what i have read about it online and i think that i could use a mumford link on my 1st gen before i finish the build and take it to the track.

Im building my CRX to have lots of fun and i want the best suspension possible on the car. Ive allready fixed the front end to its max using homemade tracktion bars and im currently building a lower control arm that's adjustable in lenght etc so i can move the Camber and Caster around. ( info on the front arms here : http://www.redpepper...ndpost&p=310709 )

Im waiting on my Tein SS Suspension from MR.D and ive adjusted the Brakes all around to fit my needs. Disks all around. ive stitch / seam welded the chassis and placed a 6 point cage in the car and i think that while im fabricating on the rear i could build a mumford link to really make the Car's rear suspension go into a new era of design and flexibility.

So im taking my time to build a car that fits my needs and will become exactly what i want ive started the build in 2004 and i still have lots of time to finish it

Greetings Erwin.
ps. thanx for all the greath help and info guys !!

In doing my research on this subject I think that one key is symetry about the centerline of the whole system. In the "static" position all three points along the bottom are horizontal to each other. The angles formed between the various pickup points and the center of each belcrank need to be the same from side to side. To establish the roll center, it is a combination of the height of the belcrank system and the angle formed by the two long rods that go to the axle.




This might be just a starting point. Others with one might chime in and we'll see if it is close.

Another link Here


Donnie

Thanks for the information and the drawing !! i think that it helps allot for the people that are trying to fabricate it and i allready posted the link on the first post yesterday eavening

annyone more info on the dimensions and angles etc ?

Greetings Erwin.

some info i found on a website by a guy calles mark fox about the roll center etc.



This scary looking contraption is a Mumford Linkage. A and E are shown attached to the axle, this time, and points F and J are pivots on the chassis.
AB, DE, DJH and GH are straight links. BFG is effectively a bell crank.

The beauty of this thing is that the virtual point C is your roll centre. The astute will quickly recognise that if you shorten the distance AE, the roll centre rapidly disappears into the ground and below... and you've kept a fair chunk of your ride height too. Actually, putting the roll centre below ground is a bad idea for a number of reasons, but it is feasible to lower it as much as you like as long as it is higher than the front roll centre, which feasibly can go to the ground or a little below. How much you want to play depends on all sorts of things like your effective spring weights, overall weight and weight distribution of the car, ride height, tyre widths and so on and so on.

that looks really heavy ,cool but heavy would it really make that big of a diffrence to do all this work and have all that wieght ???

I saw one that was NOT heavy, just triangulated enough to support the loads that were going thru it. Quite effective it appeared. And it was on a CRX. The mounting system was made quite rigid without being very heavy.

As far as where to purchase these, I'll have a little more snooping around to do to remember where I saw one.


Donnie

this kind of setup doesnt have allot of un sprung weight.. just some extra sprung weight and thats something i can live with. dont think it will be mucht more unsprung weight than the current panhardbar.

Greetings Erwin.