craig1410
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 posted on 19/7/03 at 07:04 PM |
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The Floor - Weld or rivet?
Hi,
I know this has been asked before but going back through the forum posts there are a variety of opinions as to whether to weld or rivet and whether to
use steel or ally and whether to have a single piece floor or a two piece with a "hatch" in the middle under the propshaft etc etc.
Until I read these posts I was just going to weld my floor using 16swg mild steel and using a three piece design. One large single piece bounded by
tubes A1, B1,A2,B2 and then two smaller pieces for the footwell's on either side of where the gearbox sits in the tunnel. I intended to weld in
the large squre section first and then overlap the two smaller sections so that the seam will be with the direction of travel and thus shouln't
catch on anything or encourage water ingress. The idea of using three sections instead of one large one is due to the fact that I couldn't
easily get a sheet of 16swg big enough to do it in one piece (46" wide chassis) and there would be a lot of wastage even if I did.
So....is my plan in line with current thinking or should I consider riveting? I need strength to cope with my RV8 engine so I'm not bothered
about a little extra weight. I want to seam weld the outside of the floor at least to prevent water ingress although I may just stitch weld on the
inside of the floor. I will of course take precautions to avoid distortion.
I'd appreciate your comments as I am keen to get the floor installed so I can make "vroom vroom" noises... 
Cheers,
Craig.
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Mark Allanson
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| posted on 19/7/03 at 07:45 PM |
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I plug welded (50mm apart) the floor in two sections, leaving room for an inspection/maintenance cover for the propshaft/brake pipes/loom.
I then reinforced this with 13mm ERW in such a way that at no revs would the floor be harmonic - it would be really annoying and probably induce
stress cracks. I used 18g steel.
If you weld, you will definately get distortion which you will avoid if you rivet. I have no confidence in rivets in any structural application as if
there is any movement, the rivets will loosten and possibly fail. Also alu rivets in steel with road salt and rain is a sure way to end up with you
bum on the road.
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Mark Allanson
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| posted on 19/7/03 at 07:47 PM |
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Oops, forgot the pickie!
 
Rescued attachment Floor.jpg
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leto
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| posted on 19/7/03 at 09:20 PM |
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On a locost chassis the floor is intended to be a stressed member. Much of the torsional stiffens depends on how well forces are transferred from the
frame to the floor (this may not be obvious but is the way things work, OK?). If you weld the floor you don't have to worry about this, it is
very hard to mess it up. That's probably why the book say you should use a welded steel floor.
You can rivet a aluminium floor, save allot of weight and still have good torsional stiffens BUT you have to know how to do it properly. What rivets
to use, what distant between them, who surfaces should be prepared and so on. If you get this wrong you will have failure and ware because of movement
between frame and floor plus a week chassises.
I don't know how to rivet a aluminium floor properly so I'm going to weld a steel floor.
Happy building
leto
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heyzee
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| posted on 19/7/03 at 09:42 PM |
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alloy floor
people are under the impression that alloy doesent rot away but it does.it doesent rust.alloy up against steel reacts and breaks down even quicker.to
get good results with alloy against steel there are certain precautions to take,from my experiance in useing these two together the steel has to be
painted and when dry mask off the frame work with duck tape to stop them rubbing together.or use a special type of chromate primer used in the coach
building industry and the two parts can be assembled wet or dry,but this is not your everyday primer and trying to find someone who will supply you is
another matter.as for the rivets there are some out there that are really good called mono bolts i think they come in 5mm and 6mm but you need a
special tool to fire the later ones.the 5mm you can fire with a good set of lazy tongs,as for spaceing them out i would say every few inches ,very
time consumeing and expensive
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Rorty
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| posted on 20/7/03 at 03:42 AM |
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"Solid" Monel structural rivets wont rust, won't react with FE, wont let water etc past, aren't as expensive as stainless, and
are v good at the job.
Set them every 50mm/2".
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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cymtriks
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| posted on 20/7/03 at 09:23 PM |
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I'd suggest welding in the floor in 18 gauge steel. Some stiffening may be required either longitudinal, as shown above, or lateral by adding a
tube across the floor at the front edge of the seats.
16 gauge is a bit heavy for a lowcost floor and though the floor does aid stiffness the actual thickness used seems to make very little difference.
I have heard of riveted floors working loose due to chassis flex on other kits so I'd suggest my high stiffness chassis mods which I've
described before and which I've posted a picture of in the photo section.
I suppose all this boils down to either weld in 18 gauge steel or do a decent rivet job on a stiff chassis.
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craig1410
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| posted on 20/7/03 at 10:10 PM |
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Thanks everyone, I appreciate the advice and most of it agreed with my own feelings to a large extent.
Therefore my car now has a welded 16swg floor. It's only tacked in place on the outside (every 2 inches or so) and I will now stitch weld the
inside (1 inch for every 6) before seam welding the outside fully. I know that seam welding is OTT for strength but I am doing it to avoid anything
getting into the seam and starting to rust. I will use seam sealer on the inside once all the welding is done. I decided to go for a single floor
right across the tunnel as well as I can always cut it back out later if I change my mind. I agree with someone who said that it will be a potential
water trap but I'll maybe work around that with some drainage holes. Basically I like the idea of a fully flat underside and the fact that the
propshaft and diff and all the pipes which will be in the tunnel are protected. I could have used a removable panel and may still do that but
hopefully it's not necessary.
Cymtriks, I agree that 16swg is probably not much better than 18swg but it is what I had already bought for the job some time ago when I got the rest
of my steel. I have started to add triangulation tubes (TR5 and 6 so far) and will take account of much of what you have said already on the subject
of chassis stiffening.
Thanks again to all who have contributed here.
Craig.
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craig1410
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| posted on 20/7/03 at 10:14 PM |
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By the way, Mark, I like your skids on the floor and may well copy the idea if you don't mind.
You say your plug welded your floor. How have you sealed the seam? Have you just used seam sealer on the inside or have you used something on the
outside too? That's the only reason I have decided to seam weld mine.
Cheers,
Craig.
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Rorty
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| posted on 21/7/03 at 02:36 AM |
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Syd Bridge:
quote:
I don't know if I'm missing something,
Braincells? 
OK Syd, so I left out the word "pop" between "solid" and rivet.
As anyone with a brain cell would know perfectly well, the inverted commas around the word "solid" refered to rivets that retain the bulb
end of the stem, thereby making them more solid, and less likely to collapse and loosen.
quote:
Hope you're getting well Rorty ol' fella..
Thankyou.
quote:
..I'll be seeing you soon!
I hope that's a metaphoric reference to you visiting Australia shortly.
craig1410:quote:
..I like your skids on the floor and may well copy the idea..
It is an excellent idea, and goes a long way to preventing the floor from buckling from the heat of the welds. I once did a similar thing, but used
lengths of 3/4" angle iron welded on so that the "V" was pointing at the ground. Same old same old.
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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sgraber
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| posted on 21/7/03 at 04:36 AM |
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I am wondering if anyone on the forum has used the VHB 3M epoxy tape in lieu of welding or rivets. IMO the 1" wide tape should be a very
efficient method of bonding the panels to the frame. The bond is supposedly extremely strong and can be used in structural applications.... It also
provides a watertight seal if used in continuous perimeter and to top it off creates a boundary layer between dissimilar metals.
I am this >|< close to using the VHB with 14ga ali panels... or should I do 18ga steel with stitch welds... Opinions on that? 
I like those skids too. Very cool.
Graber
Steve Graber
http://www.grabercars.com/
"Quickness through lightness"
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leto
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| posted on 21/7/03 at 06:59 AM |
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quote:
Originally posted by cymtriks
...............
I suppose all this boils down to either weld in 18 gauge steel or do a decent rivet job on a stiff chassis.
Bracing the floor (and transmission tunnel) is an alternative. Lots of pipes in places you don't want them, yes. But it will keep the structure
stiff and the choice of floor is then free.
Leif
[Edited on 21/7/03 by leto]
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DaveFJ
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| posted on 21/7/03 at 08:22 AM |
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The essential when using rivets in this situation is to coat them with a good jointing compound before reactioning them. his compound should also be
spread on mating surfaces of the sheet and chassis, this all aids to prevet dissimilair metal corrosion.
as a general rule in the aircraft industry, for a structurally loaded component, we would be looking for a spacing of about 5d where d=the diameter
of the rivet head. Also you should look to have a minimum of 1.5d 'land' which is the distance from the rivet head to the edge of the
sheet metal.
I know this isn't always going to be possible on a lowcost chassis though.
The rivets mentioned are called 'Mono Bolt Concept' or MBC rivets and are a far superior rivet to monel 'pop' type. they do
require a special head for the rivet gun however. They are available in a huge range of sizes and grip ranges and can even be obtained in stainless
steel (although these are incredibly hard to work)
All rivets will fret, the key to a good rivet is to ensure that the hole is clean
,deburred thoroughly, tight, and perfectly aligned. it is a very good idea to get hold of some shett metal grips which are small thumbscrew like
devices that can be placed through the rivet holes to locate the material in plce whilst you continue drilling. also use the grips to hold the sheet
metal down tight to the frame either side of the rivet you are reactioning.
I know this is makes the job very long winded but it is the only way to achieve a really good joint.
HTH
[Edited on 21/7/03 by protofj]
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timf
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| posted on 21/7/03 at 09:26 AM |
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quote:
Originally posted by Syd Bridge
...See you soon----not metaphoric, got a cousin in the local constabulary claims he lives not a mile from you. I'll be 'round with a six
pack(or 2) of genuine xxxx.!
[Edited on 21/7/03 by Syd Bridge]
can we have a web cam at the meeting or will it be pay per view
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Mark Allanson
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| posted on 21/7/03 at 05:10 PM |
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Craig,
"By the way, Mark, I like your skids on the floor and may well copy the idea if you don't mind. "
Honoured! The skids add a little strength, hold solid any distortion and will protect the floor if I hit the top odd traffic humps (main reason),
they are alternatly stitched evey 3" and can be easily ground off if required and replaced if I crush one or all of them.
The floor. I put a small bead of 3M Structural adhesive on both the inner and outer edge of the chassis and clamped the steel to the chassis. I then
cut 8mm holes in the steel with a spot drill and when the adhesive had cured, I plug welded the holes. Some of the adhesive burned where it was close
to the plug weld, but most is in place and squidged out to form a watertight seal both inside and out. I sprayed weld thru primer on both surfaces
before bonding to minimise corrosion.
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craig1410
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| posted on 21/7/03 at 05:33 PM |
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Mark,
Sounds like you have covered all the bases then eh?
I wish I had discovered weld through primer before I fitted my floor but I did thoroughly clean all of the steel before assembly so hopefully as long
as I get a good continuous seam weld on the outside and a nice seal with the seam sealer on the inside it should be okay. I now have weld through
primer which I got from Halfords so I can use it for the remaining panels. At the end of the day it's not going to be all that much hassle to
replace a flat floor on a Locost even if I do have it long enough to rust.
Do you intend to drill some drainage holes in the floor? I though it might be a good idea to have two or three large holes with grommets installed for
those days when the weather is very unkind. There were a few very nasty showers of rain today which made me wonder what would have happened if
I'd been in the Locost with no cover!
Cheers,
Craig.
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Mark Allanson
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| posted on 21/7/03 at 06:45 PM |
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I think I will leave drainage holes until I feel the need for them. I will have a tonneau cover and when in motion I intend driving that fast that the
rain will eventualy come to earth in another county
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Rorty
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| posted on 22/7/03 at 01:21 AM |
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Syd Bridge:
quote:
Rorty...See you soon----not metaphoric, got a cousin in the local constabulary claims he lives not a mile or two from you.
Ah, thank God, you did mean it metaphorically. You just don't know what it means or where I live.
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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eddymcclements
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| posted on 22/7/03 at 01:12 PM |
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Just to clarify the "solid" blind rivets issue, I believe that some are guaranteed to retain part of the breakstem within the rivet body.
Without this, the rivet is a hollow tube and doesn't perform too well when there is a shear loading between the joined components. With the
breakstem retained, the rivet essentially becomes solid and its shear performance increases massively. This is particularly true of aluminium rivets
which are fairly soft; the steel breakstem adds a great deal of shear strength.
FWIW, I used 4mm sealed-end aluminium rivets which retained a portion of their breakstem (or mandrel if you prefer) to retain my 2mm aluminium floor,
spaced at 25mm intervals. Clecos were used while the holes were being drilled to stop panel creep, then the floor was removed and all the holes
deburred, then a bonding & sealing compound was applied before rivetting. Pic here.
Cheers,
Eddy
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DaveFJ
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| posted on 22/7/03 at 02:30 PM |
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Sounds just about perfect.
did you consider riveting to cross members as well as around the edge ?
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leto
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| posted on 22/7/03 at 04:36 PM |
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The weight benefit of a aluminium floor is big and I would like to be able to consider it an alternative. The only way to get there is to understand
how a riveted bond is supposed to work in this application. So please excuse a very theoretical question.
Is the rivet supposed to transfer any sheer loads at all, in theory?
Leif
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ProjectLMP
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| posted on 22/7/03 at 07:45 PM |
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Structural rivets are designed to carry sheer loads. Generally this is the kind of load they handle best. Using them in tension for highly stressed
joints is not a good idea.
Home of the Astronomicalcost Mid engined LMP project
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craig1410
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| posted on 22/7/03 at 07:57 PM |
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quote:
Originally posted by leto
The weight benefit of a aluminium floor is big
Leif, The weight benefit is not that big IMO. I'm even using 16swg steel where I could have used 18swg but I can still easily lift a 6ft x 3ft
sheet myself without breaking a sweat. Surely you would have to use ally sheet thicker than 18swg to get enough strength and then the weight advantage
will be reduced.
Does anyone out there know just how many Kg's a "suitable" sheet of ally is compared with 18swg steel? I'd be surprised if you
save more than 10 or 15 Kg's. Remember to add the weight of all those rivets... (I suppose you'd need to subtract the weight of the holes
you drilled though to be fair... )
Anyone?
Craig.
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ProjectLMP
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| posted on 23/7/03 at 03:31 AM |
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A 4' by 12' sheet of 0.063" ali weights about 42.5 lbs (19kg)
The same size and gauge steel about 125 lbs (57kg)
0.050" steel same size weighs about 102lbs (46.5kg)
[Edited on 23/7/03 by ProjectLMP]
Home of the Astronomicalcost Mid engined LMP project
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Rorty
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| posted on 23/7/03 at 04:26 AM |
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eddymcclements, your description is more eloquent than mine, and is what I was getting at.
I've just been looking at my 2003 Gesipa catalogue (Gesipa Blind Riveting Systems Ltd, Keighley, W. Yorks. Tel: 01535 212200), and they make
"Bulb-tite" rivets with "superior clamping power", which are "perfect for securing difficult or dissimilar
materials."
They also do all the regular stuff, including the rivets I was alluding to; the "high clamp up, high strength, weather tight, flush break
mandrel, hole filling, dual lock design, structural G-Lock and MegaGrip rivets"
Don't believe me? Give them a call!
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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