i have done mine in 2 pieces but simply because i purchased the precut chassis plate kit from 3ge. otherwise i would have done it all out of 3mm. i would suggest making the triangular bit with the hole for the steering colum out of 1mm though as i assume its designed to give a little should you have an accident.

so i,m not barking up the wrong tree then?? :D :D
guess what i,ll be doing tomorrow then ;)
cheers
andy

Looking on the dark side as Ash suggests,that plate is where your feet are should you be unlucky enough to get hit midships and it would go a long way in stopping the chassis deforming.
I am thinking of a full plate just because it can be cut in one piece easily and folded to fit,it also forms a firewall and possibly a little know fact about accidents is the cause of fires is attributed to brake fluid being spillt on hot surfaces and anyone who has done any heating or welding near a flexy pipe will understand exactly what I mean.:eek:

so a 1 piece 3mm pedal back plate/CP16 will be a safe & stronger alternative then? fully welded in into the chassis if i go this route?
it does make me wonder why its not been discussed before, thats why i thought it might be a dumb question to ask :o ;)
cheers
andy

Hello

Just a few thoughts to add to the discussion.

It has been suggested that the plate could flex if bolted in and that welding will prevent this. I don't see the logic behind this - the flex will be occuring due to the master cylinders being mounted in the middle of the plate and the plate will be deforming in the middle. Welding around the outside of the same plate will not help things. The plate can be thickened to stiffen it up, an alternatice would be to add a strengthening rib down the back to add some depth to the plate.

With regard to the accident side of things, in the frontal impact plane, a thicker plate will help the anti-penetration side of things from the front. In a side impact, the section will be stiffened because you have 'closed' out the section, a similar thing could be done with a diagonal brace. However, with a bolted in plate you have closed out the section - but with a different set of loads path, the maximum load being dictated by the tearing of the bolts through the plate.

I don't want to teach anyone to suck eggs, but people often think that making something thicker will make it stiffer. This is often not the case. It is down to the second moment of area and generally adding 'depth' in the direction the stiffness is required will have a much much greater affect.

i see where you are coming from david. the main flaw with the half section 3mm plate is that it is not actuallt bolted to the chassis. it is bolted through the upper half section 1mm plate and down to the 1.5mm floor. this is what is introducing the flex.

to remedy the issue i am suggesting the removal of the 1mm upper to which the pedal plate is bolted to.

the flex is not in the 3mm plate its self (this is very well designed as the 90degree bend on the bottom greatly strengthens the plate) its in the fixing points for the 3mm plate. by removing the 1mm plate and making a large 3mm plate you are removing the unbraced 1mm plate joint and by welding the plate to the surrounding chassis rails rather than fixing to the floor.

i,m seeing a greater info gathering from my original query, so if i were to brace behind (engine bay side) the 3mm plate across the uprights in drivers footwell will this greatly add structural integrity to the pedal box arrangement, as base of pedal box is angled with main chassis rails am i right in thinking that adding a 25mm box tube half way up would be a good modification on strength of the surrounding area ?
thanks for your input David/Ash.

andy

sorry for the crude drawing




left is book design right is rework all in 3mm

in the book design the blue areas are not fixed the red areas are either welded or bolted. when you press on the brake pedal it pulls up the floor and pushed out the middle on the 1mm to 3mm joint. this creates a rocking motion


in the right picture the 1mm and 3mm plate has been replaced by a full 3mm plate. this plate has been welded directly to the chassis rails rather than the floor and unbraced 1mm plate. it has also been welded in the blue areas removing the rocking motion created by the poor fixing points in the book design.

another solution would be to keep the book design with the bolt fixings but also weld the blue areas to remove the rocking motion. but to be honest if you havent made the plates already its faster just to fabricate one 3mm plate.

i am keeping the book design as i have already got the precut plates but the blue areas will be welded to stop the rocking motion.

nice explanation Ash, my original understanding was that the pedal box was bolted in so that it could be removed if need be, but i hardly think it ever will be,
today i made the back plate & pedal mounting plates, i have the 1mm cp16 cut ready but what i think i will do is use 3mm plate in place of cp16 so in effect as i,ve already cut the bottom plate i,ll join the 2 plates at the half way up position, similar to the 1mm plate join AND place a 25mm box tube at the joining face/edges on the inside of the footwell as that way i can fully weld the plates to box tube then fully weld the box tube to main chassis structure, this i think creates greater strength in the forward force of when you use the brake pedal hard & also greater structural strength in side impact of that footwell area.
would you agree?
andy

nope that wont work. :D if you weld a 25mm box section in the middle on the inside you will limit the travel of the pedals.

the only way to make it really strong is to have ribs pressed into the 3mm plate but to be honest thats overkill.