Caterham A Frames - check them as part of your annual maintenance

[CarlB]

I haven't modeled the Mumforf link either, but it looks like the roll center is fixed to the two bolts on the car. The two bell cranks allow the differential to roll but not move laterally. It would be very interesting to have a suspension design that allowed equal lateral roll center movement towards the inside of a turn.  

[MV8]

The articles mention of "nil vertical loads" makes a good point. The Mumford does not generate a vertical lifting force on one rear corner the way a panhard does under load whenever the chassis end is higher than the axle end. I think any RC movement should be minimized (practically with the overall compromise) for more dynamic stability/feedback to the driver. Lateral RC migration typically increases the distance to the CG (RC shifts inboard/away from the corner and CG), decreasing roll resistance as the cornering load increases because the CG has more leverage to act on the RC.

[EdWills]

Hello Gents.

 

Although this design is perhaps not very practical for a Lotus Seven due to the cost and complexity of the system, this drawing of a De-Dion rear suspension by Len Terry would have complimented his other arrangement for the rear suspension of the Lotus Type Three Seven race car. The Terry design in the attached drawing is still in the  Lotus vein with the small diameter tubular frames for the De-Dion suspension (as opposed to the large 3 inch? diameter tube used on cars such as the Lotus 11 and the Seven Series IV Clubman car). Note: Regarding the drawing, unfortunately, my copier doesn't work that well, and although I tried to eliminate light, it didn't work - my apologies.  The 3rd picture should read 'FULL ROLL' and it looks like 5 degrees?  I really like the look of this layout, and it would be an interesting project if time and money allowed.  Cheers,  Bill

[MV8]

I've not seen that before; a telescopic upper link. I assume the thin diagonals off the lower uprights are the coilovers. The wheels would move laterally. Reminds me of a formula vee "zero roll" resistance system where the rates are just enough to keep it off the ground, though I'm not saying it would work that way.

Edited January 16 by MV8

[EdWills]

Hi MV8. Correct, the thin lines are the coil overs.  Len Terry was quite a character, and I had a few emails back and forth with him before he died. Regarding the layout shown in his book, he advised the following: "It comprises two simple frames, each forming a triangle with its 'upright', connected to a sliding joint. Each frame is located by a parallel-arm lower link, as shown, and by the usual top and bottom longitudinal radius arms which are not seen in this view.  In the drawings the body is depicted purely diagrammatically to indicate the attachment points.  This system keeps the wheels perpendicular to the road under any combination of bump, rebound and roll, and the lateral sliding travel at the central joint is less than half an inch.  Unsprung weight is clearly rather higher than for a conventional rear suspension, but the advantage of no camber change could well outweigh this, and the structure does fit surprisingly well into the layout of a normal open-wheel racing car".  Apparently, Len Terry did not incorporate this design into any of his cars, or those for Lotus (too bad!).  Just an aside.  Way back when Lotus was going up-market, they would sell off many of their sports and racing car spare parts at the factory.  They would bundle them into wooden tea chests, 2 feet x 2 feet x 2 feet or so, and you purchased the tea chests more or less items unseen, not knowing what was in the middle and bottom of the container (you were not encouraged to dump the contents out at the factory apparently!).  A friend of mine purchased one of the chests from the factory, and inside were a pair of new cast alloy rear uprights, drive shafts, brake parts, wishbones and lots of other assorted bits and pieces from their Formula Ford cars and other G.P. cars.  The price, according to him, was quite reasonable, and he planned on using some of them on a couple of Lotus formula cars that he owned, as well as a Seven.

Best, Bill.

[MV8]

I don't see any down side to Terry's design.

I like what I've seen with some Cats having a watts trailing arm system on the de dion for zero roll steer. For a live axle, I'd like to see three watts or two and a mumford with a sliding torque link next to the trans slip yoke, with the lower coilover attachments offset to the front and rear and lower for longer coilovers and springs, all attached to axle tubing with a hand full of bell cranks and a dozen sphericals. Definitely not as elegant and clean as the cortina trunion or spherical A frames though.

[CarlB]

Len Terry might not have gotten a chance to build this suspension system, but he did design the 1965 Indy 500 winning Lotus with Jim Clark driving.