1976 Autotune Gemini - ELVA MKI replica

[Darkspeed]

On the Blue Gem' chassis, you can see that the lower rear wishbone bracket is positioned above the lower chassis tube.









On the Red Gem chassis the bracket is below the chassis (shown upside down)





I also suspect that early on these chassis were fitted with Triumph Herald/Spitfire wishbone design with trunnions as the brackets are at an angle to provide Caster trail - There is no need for this angle when using a Cortina system as the Caster trial is provided by offset of the upper and lower ball joints.

Its also noticeable that the upper brackets are closer to the top of the chassis on the Red gem than the Blue Gem chassis further separating the inner bracket positions which make the wishbones more parallel to each other.

The suspension is very similar to that of a Westfield - The outer dimensions are fixed by the use of the same ball joints so are the same between the two vehicle - A Westy has the inner pick up points 207mm apart vertically - On the red Gem they are 240 apart vertically - I expect the Blue gem will be very close to Westy dimensions. As the Upper bracket is lower by about 10mm and the lower bracket 25mm higher.

My G27



The distance between the brackets is 210 and it also runs a taller upright giving a greater wishbone inclination.


The distance between the ball joints on a Cortina upright is 225mm - On the Blue Gem and a Westy the Wishbones are Convergent as you would expect - On the Red Gem - Divergent! - Not right....

[Darkspeed]

The worst aspect of working on this chassis is the time and effort required to remove all the factory mistakes and poor workmanship.
The original builders additions are thankfully few, and the welding is poor enough to make removal very easy. The factory work is unfortunately welded on pretty well, even much of it is in the wrong place.

Removing the engine mounts was a lot of cutting and grinding










Diagonal replaced - some silly thoughts about even more tubes.





I took some measurements of the distance between the inner suspension mounting brackets on the Blue Gem - 200mm.

Looking at this snap of Gem 1 the bracket position looks very much the same as Blue Gem





As Red Gem is going to get new brackets - I may spend a few hours with CAD and draw out the chassis, then transfer the dimensions to some suspension software I have to determine where to weld them.

[Darkspeed]

I think there may well be quite a few similarities to the G27 chassis .... I wonder how that has happened.

[Darkspeed]

More time spent grinding off the old engine mount plates, followed by welding up the holes that were drilled through the chassis for the engine mount followed by dropping in the tube diagonal.








I then had a think about the two other tube triangulations...




...and decided that will probably need the room that the side diagonal would take up - for minimal gain - but the lower tube triangulation should not be in the way of anything engine related, and will also provide a useful load path.





I think that's enough triangulation in the engine bay. There are now plenty of triangles connecting the front suspension load points to the rear, and it should now have have enough strength in torsion to deal with the loads from the V8.

Better picture required - the very front is now getting some work - A tube diagonal will be going in between the front suspension verticals and a few tubes plus an 'X' up front with mounts for the radiator.








The other job on the list is the Roll Hoop.

[Darkspeed]

Not much done today on the car as I had leaves to deal with, the F1 highlights to watch, A Mitsi ASX to repair a boot switch on and a 308 Pug to try and diagnose a non starting fault.

On the Gem I chopped the front "number plate holder" off the chassis, and cut the steering rack / suspension bracket support off (partly).

This allowed me to get easier access for a front diagonal and check to see if it will get in the way of rack mounts when I move the rack rearwards to keep up with the migrating suspension brackets.





The rack support / mount will drop between the chassis and not be on top of it - the rack will also be positioned central in the chassis not offset as standard.

There is clearance for the rack mounts. In the most part - the 2 x 1 vertical tube will probably need a nibble to clear the rack gaiters.








Really happy with the chassis mods.








Welded the diagonal in.





Almost called it a day at that point - final job was clamping the roll over bar on to get a visual on the various modifications that will happen at the rear of the chassis - the central section pretty well done.

Ordered up some suspension brackets to replace the standard ones that will get removed quite unsympathetically.

I see more cutting, grinding and cleaning up of factory welds in my future - a couple of hours in the evening through the week should get it sorted.