Floor panel thickness?
Discussion
I will shortly be rivetting on my alloy panels and I wondered if 1.2mm (sides) and 1.5mm (floor) plain alloy sheet is going to be man enough for the job.
I have seen 'chequer plate' used - this is much thicker (2-3mm) but it looks really trick.
What do you guys normally use? Also, is 'double skinning' a good idea or not?
I have seen 'chequer plate' used - this is much thicker (2-3mm) but it looks really trick.
What do you guys normally use? Also, is 'double skinning' a good idea or not?
Sounds about the right gauge panels. The floor would be ok in 1.5mm sheet, as long as there aren't any large expances between the chassis rails being fixed to. 4mm rivetts about 50mm / 2" apart seems to be the norm - enough to stiffen up the chassis, and not enough to weaken the chassis through perforation.
As for double skinning, I suppose it depends on what the car is, and what it would be used for.
As for double skinning, I suppose it depends on what the car is, and what it would be used for.
If you havn't already started then consider welding in an 18g sheet steel floor. Ally floors save some weight but for a road car this is fairly trivial. Ally is more expensive and will corrode just as quickly as steel if road salt gets near it. Some kits are known to experience riveted floors falling out, usually because the steel frame they are riveted to is too floppy to support them properly.
A riveted floor only contributes to stiffness when a chassis is new, after that the rivets gradually work free enough to reduced this contribution. I recall a manufacturer of aluminium monocoques for race cars stating that their chassis lost a third of their stiffness in a seasons racing.
On a lowcost type of car the floor contributes very little to torsional stiffness regardless of how it is fitted, though it does stiffen the chassis against lozenging.
If you are determined to go aluminium then consider bonding as well as riveting and also consider riveting on a right angle section, either folded or extruded, of ally along the sides, to both the lower chassis tubes and the floor panel. This doubles up the number of rivets and supports the ally floor in two directions, by the rivets through the floor panel, and by the right angle strips. Stagger the holes between the two rows of rivets in the floor sides.
An alternative is to use big head rivets. I think the chap who makes the Foreman Ferrari P4 replica sells them but I may be wrong here.
A riveted floor only contributes to stiffness when a chassis is new, after that the rivets gradually work free enough to reduced this contribution. I recall a manufacturer of aluminium monocoques for race cars stating that their chassis lost a third of their stiffness in a seasons racing.
On a lowcost type of car the floor contributes very little to torsional stiffness regardless of how it is fitted, though it does stiffen the chassis against lozenging.
If you are determined to go aluminium then consider bonding as well as riveting and also consider riveting on a right angle section, either folded or extruded, of ally along the sides, to both the lower chassis tubes and the floor panel. This doubles up the number of rivets and supports the ally floor in two directions, by the rivets through the floor panel, and by the right angle strips. Stagger the holes between the two rows of rivets in the floor sides.
An alternative is to use big head rivets. I think the chap who makes the Foreman Ferrari P4 replica sells them but I may be wrong here.
I see your point but welding steel panels will take a lot of expertise and I am not a welder by any means, but I can wield a rivet gun pretty well 
. Anyway the chassis is already powder coated and I wouldn't want to have to get it done again (too costly)
I was going to bond the panels with Sikaflex or Tigerseal (along with the rivets) - the bond is so strong that the rivets are only really required while the goo sets but most people tend to rely on both anyway.
To prevent corrosion it might be an idea to spray underseal on the exposed panels (or maybe just Hammerite?), leaving the interior side all nice and shiny.
. Anyway the chassis is already powder coated and I wouldn't want to have to get it done again (too costly) I was going to bond the panels with Sikaflex or Tigerseal (along with the rivets) - the bond is so strong that the rivets are only really required while the goo sets but most people tend to rely on both anyway.
To prevent corrosion it might be an idea to spray underseal on the exposed panels (or maybe just Hammerite?), leaving the interior side all nice and shiny.
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