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  #31  
Old 28th May 2009, 02:09 AM
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AshG AshG is offline
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p.s godforbid if you are involved in a side impact. but honestly the foot well strength will be your last concern the side rails in the seating area will deform and crush like a tin can well before you worry about your feet.

i put my seats and harness intoday and thought oooo. i really would be buggared if someone hit this thing in the side.

rite time for bed gotta be up at 7am
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  #32  
Old 28th May 2009, 02:11 AM
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i was looking at the plan in the book & thought the box tube would just fit, did think it would clear the pedal travel, i,ll have a look tomorrow & see what will fit/work, but basically i,m intending using all 3mm plate & bracing it some way to reduce forward flex motion & side structural strength.
i,m no mechanic/engineer but i do enjoy the learning of what improvements/ ideas i get from building my chassis.
like said earlier i,m surprised this area (of this discussion ) hasn,t been discussed previously???
andy
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  #33  
Old 28th May 2009, 02:18 AM
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i bet you sat in the chassis & put harnesses on & thought..... hmmmmm not long now?????

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  #34  
Old 28th May 2009, 09:18 AM
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yep most definatly did

once you have welded in the 3mm plate you will see how strong it is. i would then work from there.
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  #35  
Old 28th May 2009, 09:07 PM
flyerncle flyerncle is offline
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David,your thoughts please.
Full pedal box plate in 3mm plate to cover the complete section of that part of the bulkhead or the plate with 3 folded edges to fit inside the frame welded and the original folds on the floor.
Ash's comment is very interesting with regard to side impact and bears some thought,I am know thinking of cross bracing the floor and seat area.
I think Ash is also on the ball with 1mm plate for the steering support to stop the column moveing rearward in the event of an accident,something else to bear in mind !

Last edited by flyerncle : 28th May 2009 at 09:09 PM.
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  #36  
Old 29th May 2009, 12:05 AM
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davidimurray davidimurray is offline
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Hello everyone

Firstly, I was thinking about AshG's point regarding welding and I must admit he is right. Think about a drum skin. If you apply a load in the middle, previously it would be transfering the load at the top and bottom - by welding the sides you reduce that load and distribute it around more - you also now have the drum skin affect.

With regard to the stiffness of the plate. The best way I can think of describing it is to get a piece of of strip 1mm thick and 30mm wide. Holding the strip across two benches with the wide side up, press down in the middle and watch it bend. Now rotate 90 degress and try and press down and bend again - it's a hell of a lot stiffer. For the maths a simple example here -http://physics.uwstout.edu/statStr/statics/Beams/bdsne47b.htm

If you look at the equation for a rectangle then the moment of inertia is
3
bd
12

Where b is the 'breadth' and d is the depth. Hence by making the section deeper you stiffen it by a cubed factor.

In the case of the pedal box you could add some form of strengthening rib across the back. However, by adding a narrow rib across the back you willl produce a stress raiser.i.e. a point or line where stress is concentrated. Hence it is better to add either a wide rib (such as a piece of box) or lots of smaller ribs. Flyerncle, your idea will add some strength to the plate, but not a great amount for the weight you will add. For a n interesting play - you could try taping a piece of card across the opening and try addining different forms of strengthening. I personally would look at some form of cross brace in the engine bay, this could be braced above and below to feed the load into the tubes either side.

Side impact is an interesting one. In this case stiff may not be the best. The obvious thought is that you don't want the side of the car to be 'crushed' but there are actually two things to consider - one is energy dissipation the other is penetration. You could make the side impact area extremely stiff, but what happens to all the force when you are hit. If you had a 'solid' chassis and you were hit then all the force would be transferred through the car and into you. 30 or 40G in a very short period of time can cause some serious damage to the human body. Your better off trying to disspate that same energy over time, some some flex and bending in the chassis can be good. Think of modern crumple zones. The guys I use to work with designing racing monocoques used to allow about 20mm of bending over a typical space frame. The idea being that the driver might get a little squashed and bruised - but the severity of his injuries would be less.

That's some food for thought!
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  #37  
Old 29th May 2009, 08:04 AM
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I agee that the plates in this area are for protection,
but I thought it was to protect your feet from an exploding flywheel.
Is this not the case?
also is flex in this area a real issue most pedalboxes in pruction cars have a certain amount of flex and use steel brake pipes and can run for hundreds of thousands of miles without pipes fracturing and causing accidents.
Or am I missing the point?
Ray
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  #38  
Old 29th May 2009, 06:22 PM
flyerncle flyerncle is offline
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Thanks David,all makes sense.
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