Originally Posted by gtflash
good job as always! like the upper backrests! what sort of size did u decide on for backrest width.... my next job is to fabricate somet as i hate my seats and particualr upper support(or lack of)!
The upper back support to me ages to work out what I wanted……if you look closely at the picture of the rear backrest you should see it taper out wider the higher it goes ….i studied as many high speed boat pictures as I could find and noticed all the racers etc upper body moved considerably more than the hip area …the taper was added to still allow for some slight movement just under the shoulder socket.
The seat base at the widest part on the rear is 400mm …the inner size of the lateral is also 400mm at its widest point …..this allows me to put in upto 50mm cushioning either side and still allow wet weather clothing. I am also looking at putting in airbag bladders on the laterals ….same as the new Audi R8 …. I have built the backrest to allow for movement but could be wrong in doing this …by having blow up bladders I can determine exactly how much movement (if any) I need
There is a lot of trial and error involved, the suspension parts I know work ….the backrest might work great but also might not work…. but is removable and its back to the drawing board ….Ullman has done a PHD on shock mitigation …..he hasn’t gone for laterals so there might be a reason not too that I have missed.
For the backrest I used 3 layers of fibreglass then used Kevlar hybrid ….I layed it out in the cross design …same as kart seats and formula 3000 …this gives considerable strength but allows flexibility …..also how many of us actually use the backrest …apart from handholds for rear passengers ……..most drivers and passengers will be in the slightly forward position holding steering wheels and handholds …this was the reason I went for a lower back support that will used and such deep laterals.
Speaking with JW last night and I think I should finish 2 ….fit and test then anything that needs changing I can do on the other 4 …..sounds like a plan!!!