|Paul (V8Chevette) dropped round, and gave some great advice on how to strengthen and spaceframe the shell. Loads of food for thought there. Cheers Paul!
I've started planning exactly what needs doing to strengthen the shell. There are some fundamental weaknesses to the manta bodyshell. Structurally, the areas are:
Where the A pillar meets (but doesn't touch) the Sills Strange piece of design, it misses the jacking point too! Ideally these would all meet. The A pillar could also be a lot stronger. The pillar is covered with a thin metal skin, and rusts heavily from the inside.
Just below windscreen where the A pillar meets the strut going immediately under the windscreen The A pillar would ideally mount onto this in a much stronger way… it's not too bad. It'll need beefing up if the front end is spaceframed though.
the dash support strut under the windscreen (helps support the top of the steering columnEr… mine's now in the bin, and I'm hoping to replace this with box section which links to the rollcage.
Just below windscreen where the A pillar meets (but doesn't touch) small struts above the lower chassis legs going into the engine bay. Again, this isn't too bad, but will need strengthening and replacing when spaceframing the front.
where the b pillar meets the crossmember below the rear seat. Well, they don't meet directly, which is kind of a problem. I'm probably going to unpick this, and replace it with some box section. Arguably, this isn't necessary, but I think it'd buckle under a heavy side impact.
Corrosion also makes these areas weak.
The chassis legs under the feet of the front seatsRottastic! awful design as far as rustproofing goes. 2 sheets of steel folded together… no rust proofing, loads of holes for water to get in. chop out and replace with box section.
Where the B pillar meets the sill on the Coupe shell. The sun roof drains into the the sill down the B pillar, and this is usually shown as holes, or large amounts of patchwork.
Drivers and passengers floor, under the washer bottle, battery, and all the seams in the front footwells. Usual areas on the manta, stems from poor rustproofing and design.
Where the chassis legs come up to the engine bay big holes here for water to get into and help rot the car from the inside.
The sunroof Crap design, retains water in the foam used to bond/seal the mechanism to the roof, consequently, the roof rots! I've removed the whole assembley, and will rivvet an aluminum plate to the roof instead.
So, there's a little work to be done to sort this lot out. I'll take some photo's of the bits I mean, as it'll make it easier to show.
The spaceframe plans are to continue the box section chassis legs up and forward to locate the top of the subframe, and then to triangulate this onto the top of the A pillars, and also to cross brace between the two legs in front of the engine. The front end will also be binned, and replaced with a fibreglass front end with a box section chassis behind it. I'll sketch something when I've taken some measurements.
We also looked at the front suspension design, and specifically how to fit a coilover in place of the existing spring. This would mean the the subframe is completely self contained, and would similify the design for the spaceframing.
As far as the rear goes, as I have a good supply of manta axles, and an LSD fot it, I'm going to keep the manta axle, but ditch the torque tube, and 4 link it. I'll keep the panhard rod arrangement over a watts linkage, as it's already there and it works fine. To ditch the axle, I'll need to shorten the the torque tube to just be a 4" linkage which a longer prop can just bolt onto. I'll need to figure out the linkage arrangements, but can't see it being a big problem.
That covers some of the planning.
I did a load more welding on the floor plan, and plastered all the bear metal I could see with primer. It looks much better now, and I almost feel like I'm making progress now.