Healey Sports Cars

Update, Installed (3) X-members,engine room, cockpit and trunk, of 1" x .06" wall, square steel tube. This made a huge difference in beam/torsional strength. This allows cutting-off the integral fenders, without serious flex problems, resulting. Boxter 1/2 shafts are 1" offset on lengths, just like the "tunnel" is in the Healey,(good).Well maybe....Jensen Healey roadster is somewhat noted for being a bit "flexible", (cowl shake). Working from the MGB thread of how to limit engine torque reaction, using a longer lever, seems to be the consensus. Consider this in reverse, using a sturdy engine block,C5 torque tube and Boxter transaxle, mounted at four plus postions,spanning rail to rail and front to rear with the frame/unit structure. These would have perhaps tunable hardness isolaters for mounting. Not as rigid as metal to metal,(street car use), would none-the-less reduce torsional flex of the body. I think this makes a "ladder frame" from a flexi-flyer. Onward. roverman.



Edited 2 time(s). Last edit at 04/10/2012 11:43AM by roverman.

Art, the torque reaction will originate in the rear as the pinion tries to rotate the ring gear the drive line will try to twist counter to the pinion rotation. That twist will be carried up the torque tube to the engine block. Since the torque tube is rather small in cross section, it will still be up to the body to resist most of the torsional load. Spreading that load along the entire structure as you suggest would help, but still the basic body stiffness won't be improved much if any. Seam welding all the body structure would help, but I'd say if you really want a stiff chassis with a good street ride I'd look at installing some type of steel beam structure tied to all the drive line components, basically a seperate frame and then mount the body on that. Adds weight, but about the only way to really stiffen up a roadster.
My Lotus Europa has a central back bone type frame with a pretty good sized cross section, but even being a coupe it still has quite a bit of body flex which I can hear as squeeks and rattles on rough streets. Same for say a Triumph Sptifire, still a very narrow back bone type frame and a lot of chassis twist even with low horsepower and torque engines.
Considering the power you plan on having in the car and the handling you desire I think that building a new frame assembly and incorporating that into the body would be the way to go.

Bill and clan, I defer to the aluminum driveshaft torque test listed in eng./trans section. "3.5" dia x .125" wall x 55" long sustains 44k ft lbs of torque input. C5 torque tube is 5" o.d. x 3/16" wall and approx. 64" long. Healey has steel tub with full length unit frame. 10+ point cage will be employed. Is it possible your Europa is flexing because of the f-glass ? Cheers, roverman.

Can't argue with you, but then I don't understand your original post. If the body is that strong and the torque tube that ridgid then what's the issue? I realize that my Europa flexs because of the f-glass body, it was designed to a bit, but you seemed concerned with eliminating the cowl shake or flex. If the torque tube is that strong you shouldn't have any problem with torque reaction in the chassis as long as both the engine and rear suspension is mounted with the same type of mounts having matching flex rates. Should never impart any twist to the chassis, just drive the whole side of the car downwards or lift the opposite side. Only suspension settings could address that issue. Same sort of thing in a funy car or dragster where the axle and engine block are ridgidly mounted, no chassis flex parrallel to the engine rotation at all. It's the cars with suspension in the rear that start showing chassis twist and lift one front tire before the other.

Art, I think your attachment points between components of your torque tube assembly may be sort of critical as there are a fair number of joints and play can stack up. But aside from that, as between the engine and transaxle the entire output of the engine is between the pinion and the torque tube. Follow the flow. Diff housing to TT to engine block. Crank to driveshaft to pinion. Total output is between the diff housing and the pinion at this point, where the axis changes. So far we have no forces rocking the engine, the diff, or the body, other than inertia.

At the diff torque transmission goes transverse and exists only relative to the housing and output shafts until they connect to the tires. Still no longitudinal twist in the body, only a lifting force. Bill's Europa presumably uses the frame in place of the torque tube, subjecting it to twist.

In the real world will one tire plant harder? Probably has a lot to do with the inertia of the engine block. Maybe.

Jim

I feel there will be no measurable beam/torsional flex between t-axle and front of engine,(formidable rigid mounting throughout). I shall start the sorting-out process without LSD in the t-axle. With 11.5" of tread each side, might get by. I suspect bags all around and adjustable QA 1 inverted shocks, should speed the chassis tuning. I "may" start with just an adjustable rear anti roll bar,because of large tire advantage, in rear. Thanks, roverman.

I



Edited 1 time(s). Last edit at 04/18/2012 02:37PM by roverman.

Art,

Any progress pics to share?

DT

David and clan, fenders and rear quarters are mounted. I want the wheel/tire combo in there, for pictures. I must now learn "shrink, fit and upload" ? Cheers, roverman.