Hi all im in the process of making some room and getting some funds together to start my haynes roadster. Ive been having a good look around the forum
and some great info but one thing i have noticed is that all the pics i have seen on peoples chassis is that they have been made out of mild steel box
section. Has anyone used s/s box section instead (just thinking about corrosion over time) are there any potential issues with using s/s box section
over m/s box section.
Simon
Hi,
There has been a discussion about that on the Haynes forum :
http://forums.haynes.co.uk/showthread.php?t=8504&highl
ight=stainless+steel+chassis
If you're afraid of corrosion with mild steel, the best thing is to have your chassis powder coated when finished. It is a bit costy, but really
worth it.
quote:
Originally posted by Simon1979
Hi all im in the process of making some room and getting some funds together to start my haynes roadster. Ive been having a good look around the forum and some great info but one thing i have noticed is that all the pics i have seen on peoples chassis is that they have been made out of mild steel box section. Has anyone used s/s box section instead (just thinking about corrosion over time) are there any potential issues with using s/s box section over m/s box section.
Simon
. There have been successful builds but
it's unusual and I would not recommend... quote:
Originally posted by voucht
If you're afraid of corrosion with mild steel, the best thing is to have your chassis powder coated when finished. It is a bit costy, but really worth it.
quote:
Originally posted by Bluemoon
quote:
Originally posted by voucht
If you're afraid of corrosion with mild steel, the best thing is to have your chassis powder coated when finished. It is a bit costy, but really worth it.
Be careful with powder coating, look very nice but only good if done well, water can get traped under the coating..... Also difficult to touch up.
Thanks for the reply's guys, mild steel it is then.
As some of you know I'm not too happy with the powder coating on my car which has an old Luego chassis . Have just spent the last few weekends
stripping the car down so that I can sort it out and have found the problem is even worse than I thought. The powder coating is pulling off in sheets
and the chassis under the coating is badly rusted. Going to get it shot blasted and use something like POR15 . Don't know if this problem affects
any newer than old Luego chassis's but worth checking especially you guys that took advantage of old Luego's show deals where they powder
coated the chassis for free. Suspect had the chassis's been shot blasted before powder coating there wouldn't have been a problem
something I posted about 8 years ago, food for thought?
[Edited on 26/1/17 by rusty nuts]
quote:
Originally posted by Bluemoon
If your worried about rust investigate "hot zinc spray", basically galvanization by spraying molten zinc a the steel chassis (conventional galvanization in a bath of zinc will likely distort a space frame chassis). Something I considered but this causes difficulty with some welding I wanted done latter in the build.
Dan
I've had a (mild steel) Haynes chassis sitting in a damn, half underground, 'garage'-like building after painting it with POR-15 and
Blackcote for the best part of 3 years. No signs of rust. Drilled holes a few weeks ago for panels and a small amount of watery rust came out of a
couple of tubes which up until then had been sealed since the chassis was welded (pre 2012!)!
Incidentally - the POR paint has been OK but, despite careful prep, has not adhered 100%. I suspect other paints would have done as good a job -
without the faff involved with the POR.
I am debating whether to Waxoyl (or similar) inside the tubes before I rivet everything up - but not sure if that is overkill.
If the car is for dry weather use only I would suggest that a well painted surface with whatever metal paint you are sure is going to put up with
knocks and scuffs should suffice. You may need to maintain / touch up - but it sounds as though there is no real 'fit and forget' solution
here!
If you plan on the car getting wet a lot I guess there should be more work to ensure it's watertight wherever it needs it than just the outside
covering: e.g. a nicely powdercoated chassis with a floor riveted on with 100 unsealed rivets will probably be at most risk from rust from the
inside?!
So what would people say is a average / good price for getting the chassis powder coated?
I paid 300 to have mine sand blasted and powder coated. The quality is absolutely spot on. I've had suspension bits done for my other cars by the
same company and they've lasted incredibly well over the years.
That 300 was for full chassis with cage.
[Edited on 27/1/17 by Daf]
Nice one cheers for that
quote:
Originally posted by Bluemoon
quote:
Originally posted by voucht
If you're afraid of corrosion with mild steel, the best thing is to have your chassis powder coated when finished. It is a bit costy, but really worth it.
Be careful with powder coating, look very nice but only good if done well, water can get traped under the coating..... Also difficult to touch up.
Dax had loads of issues with powder coat quality over the years (several different companies doing the coating)
I've got a few bits done by them which are pretty shocking - were as the stuff I had done myself is 1st class but twice the price.....
If your looking for a reasonably affordable DIY solution then good chassis paint in the answer (POR15 gets a good name even if its a faf to do it
right) - and paint is easy to touch up / repair if you realise you want to weld on another bracket too 
quote:
Originally posted by alfas
more expensive way...but lasts for ever and no paint needed at all: hotdip zinc, done right with the correct preparation of the chassis in advance, it will NOT harm the chassis nor warp it.
i had it done with a tubular seveish chassis...the holes where not that big...definately not that big to weaken the chassis...and the result was
spot-on.
even 20years after built the chassis wa slike new
please also check this TVR chassis:
http://www.garagehofmann.ch/pages/tvr3000s1978.html
Just going back to the steel to be used I have the opertunity of some 25 x 25 x 3mm mild steel box section, is that the right one to use?
25 X 25 1.6mm ERW square tube is the correct one to use.
Plenty of builders have used the 3mm box section to good effect.
That said, the chassis will end up a lot heavier than need be.
quote:
Originally posted by Simon1979
Just going back to the steel to be used I have the opertunity of some 25 x 25 x 3mm mild steel box section, is that the right one to use?
"25 x 25 x 3mm mild steel box section"
^^^but also that in itself doesn't tell you what kind of steel it is.....
"mild steel" is not a grade of steel in itself and covers a huge range of grades - in this country that normally means S275 for structural
steel (which is what most places sell), but European S235 has become very common too - and who knows what fell off the boat from china....
the difference is the yield strength - literally 275N/mm² or 235N/mm² - they are the same weigh, same stiffness, look the same - but one will fail
at a significantly lower load
but even that is not the whole story - structural steel tubes / boxes can be made 'cold formed' or 'hot finished' in the same
sizes - these are totally different !
cold formed ones have bigger corner radii (which can give you practical issues when welding) and the seam is dead centre on one side, otherwise the
look the same as the hot ones - but cold formed ones have no stress relief, so the buckle much more easily, they have residual stress concentration
at the corners which makes it more likely to distort, crack and is just a bad idea for welding in general (at least anything that expected to carry
any load)
cold formed sections are made and sold to EN10219, hot finished are to EN10210 - check the paperwork !
It doesn't apply so much to sections less than 3mm thick, but there is also the subgrade for all of the above as well - this is the toughness of
the steel at low temperatures - any decent steel should be tested (charpy v-notch at +20, 0 or -20°C normally) - but cheap nasty steel will never
have been tested and could be very brittle
the certificate that you SHOULD get with any steel will tell you what grade, to what standard and what tests it passed (and by how much)
if a steel supplier can't give you this then I'd have to assume they are selling doggy steel (it happens a lot)
and while were on the subject - none of the above matters unless your buying appropriate welding wire to match the grade you've got....
[Edited on 12/2/2017 by mcerd1]
Thanks for that info. I have a feeling it is the s275 grade as it is the steel that we buy through work for our fabrications. Would have to find out if we can get the 25 x 25 x 1.5mm. Our thin walled box section all comes in 3mm thickness.
stainless welding is more problematic that mild steel....it can be brittle at the weld sites, it also is less flexible that mild steel (not
necessarily a good thing )
your car if built properly from mild steel and rust proof it correctly it will out last you.....so whats the panic about? ;-)
as a side note my chassis is 39 years old on my phaeton......still rust free, looks like it only got painted with ordinary metal paint.....and looked
after. should last another 20-30 years so 60 -70 years......thats a long time to own a kit car.
[Edited on 12/2/17 by snowy2]
Theres no panic mate. When i started this thread i was thinking about using stainless steel as i was thinking about corrosion, but also the reasons why people dont use it.
My home made locost chassis will be 20 years old in June this year, its mild steel, and all as per the original book,in sizes etc
when it was finished, it was painted in red oxide, and then hammerite, and 99% of the paint is still on the chassis
Imho, no need for stainless or zinc coating, as its just adding unnecessary weight,
steve
cheers steve
Great thread very useful for me right now!
My build is a re-body of a land rover discovery. I've built body that would usually bolt to the floor section and bulkhead of a land rover
discovery. After much though I have decided that trying to save the solid rust free bits of this is likely to be less rewarding and fit for purpose
than building a replacement. There are roll cage regulations that give guides on the size of the main bulkhead members (50*50*3mm) and any required
chassis outriggers (100*50*3mm, using chassis spreader plates.). There is already substantial frame work in the body, and there is the chassis, so
I'm thinking that 25*25mm section should be plenty to make up the floor, tunnel, and foot wells.
So am I asking for ERW EN10210 section with a strength grade of S275, or does the presence of the chassis and the body (motorsport spec tubing) reduce
the strength requirements for the box section?
Would it be sensible to drop to the 2mm section for the section that is mainly being used for tunnel shape and seat/seatbelt (with suitable spreader
plates) mount points, or would that make the welding tricky?
I've asked a local supplier for some prices and I will be drawing up the floor and bulkhead in FreeCAD soon. The floor section will bolt to the
sills of the body (100*50*3mm section sills) and will most likely be in one piece with the bulkhead that will most likely bolt to the body somewhere
around the tube that goes bellow the windscreen. For the panelling what is recommended most? Tack welding in large sheets or riveting? This is likely
to get wet on a regular basis!
[Edited on 23/2/17 by WesBrooks]
I can't tell you if en 10210 are really your best choice (I design structures' not cars) but you'll probably struggle to find S275 box
section these days - Nearly all the mills only make S355 now...
If you do get this stuff go for S355-J2H to EN10210
Fair enough! I think it's time I RTFM on chassis design. I'm happy that for this project it isn't especially critical as the rest of the structure is over engineered. I'd like to think there is a possibility of a Mk2!