Mumford Linkage

[rcr286]

In another thread someone pointed to suspension software that has a link to the Mumford linkage on a Mallock. It states that this linkage allows one to locate the roll center of a solid axle "even underground". I have seen these before and understand how they locate the axle, but the last statement is new to me.

Can someone explain this one? If you could include a 'string computer' drawing of this I would appreciate it.

-Roger

[retro_msport]

I must admit i've had a little look at this, but as it sits to low for use on an escort i've stuck with the low RC kit that i make... but looking at it, i always figured the RC was along the length of the connecting bar between the two pivots

[breezeblock]

does anybody have a link to pictures of this

[retro_msport]

Originally Posted by breezeblock

does anybody have a link to pictures of this

Do a Google image search for "mumford link" I tried pasting the image on here but couldnt get it to work

[rcr286]

I am learning more, but I still have not found how one would locate the roll center underground.

This is a pretty good image:

http://not2fast.wryday.com/chassis/mumford.gif

[zefarelly]

If I had half a day to spare I could draw that in solidworks and you could move it to demonstrate travel etc. one day I'll get round to all these things !

[rcr286]

I don't need to see how the linkage works, I would just like to know the method for finding the Roll Center on it. With a-arm suspension it is easy to draw lines until they intersect then draw a line from the intersection to the contact patch center, or Strut design to draw a line from the control arm and perpendicular to to the KPI until these intersect and then a line to the center of the contact patch. It is easy to visualize and understand the dynamics of the Roll Center in these scenerios, but with a solid rear end, the classic RC location is at the center of the axle...which is easy to understand. I just don't know the proper way of finding RC with Mumford and Watts linkages. Do you draw a line through the rods, is the RC simply where the links are mounted to the chassis (RC could not be below ground), or is it something completely different?

Another question...is a Mumford is appropriate on a rally car that requires a fair amount of travel? Should this really only be applied to a circuit car that has very little travel and possibly a sway bar?

I have a rally car that needs good axle location and I would like to design and assess whether this setup will work well for me or not. A panhard would be fine, a Watts link might be better(?), but if nothing else a Mumford would be kind of fun to develop.

[zefarelly]

if you can apply loads to points ( ie the pick up points of the suspension to the car and weights) themn theoretically shouldn't you be able to work it out, Solidworks will calculate loads, CoG etc. I f I knew how to do all that I wouldn't be on here though in all honesty, I'd have a proper job at prodrive or something

[rcr286]

Oh fer sher...I just thought that at this point that is a lot of work to extrapolate the function of roll center. As you said, "if I had a day to spare"... I hope I did not offend, as I did not intend to blow you off. I am simply hoping that someone already knows and can describe the method or send me to a resource that can.

[zefarelly]

ahh . . . 'free' developement . . . it does happen on here, although usually we just give up and stick to our cart sprung beasts !

[ian_w]

Originally Posted by rcr286

I don't need to see how the linkage works, I would just like to know the method for finding the Roll Center on it.

There was an article in Racecar Engineer a long time ago about it. I used to have one on a 'Mallock' type clubmans car. The roll centre is at the intersection point of the two diagonal links from the ends of the axle.

By necessity, the 'rocker' parts of the linkage need to be below the axle centreline which is no great issue on a racing car but may be prone to getting wiped-out on a rally car. It may also be difficult to engineer a sufficiently rigid mounting point for the rockers on a saloon car as it will be some distance away from the floorpan.

[rcr286]

Thank you Ian,

I knew I had to consider the framework, but did not realized that the rockers had to be below the axle center. This does present a challenge in a rally car...