Welding Required
 

What are the thicknesses of the steel required to be welded (im still waiting for WH Smith to deliver my build book)?

I know the chassis tubes are 1.6mm, can this thickness be changed? I know it will increase the weight and cost slightly, but im sure it would be cheaper than spending £200+ on a mig welder, would there be anything wrong with using 2.5mm box?

25 X 25 RHS box section
 

I would not even think of using 25X25 RHS box section to build a spaceframe chassis.

The weight gain would be unaceptable :eek:

Although I am not a race engineer, I can also forsee structural reasons as to why this material is not suitable.

If you really do not want to buy a MIG welder, why not tack your chassis with the stick welder, then hire or try and borrow a MIG to fully weld the chassis.
This will probably work out cheaper than the extra cost of RHS box. ;)

I've done a few calculations based on using 1.6mm thick box and 2.5mm box. Based on using 36m of box and 1.6mm thick it comes to 42.4kg and using 2.5mm box it comes to 63.67. This is quite a large % increase in mass but in the grand scheme of things it isnt much since someone of the larger build than me could easily add double that mass.

There isnt that much of a price change. 1.6mm box is £14 per 6 m, i havent got a price for 2.5mm 25x25 but 3mm 30x30 is £20 for 6m so im guessing 2.5 25x25 would be about £17-£18 so thats £24 more maximum for the steel used.

i understand in a way what you are saying but have to ask WHY? the design of the chassis has had structural tests etc & has no need for the extra thickness steel that you suggest :confused:
i,m not knocking your thoughts just not sure why change a working formula.

as for the welding required... the way i see it its part of the ethos of the concept "build your own sports car".

i couldn,t weld until i started a course at local technical college in january this year, my welding might not ( i know its not ) be to qualified cert standard but feel confident enough to build my chassis & drive it once completed, & if you build your own chassis you will "know every inch " of it which when its on the road is something to be very proud of.
each & everyone that is building a Roadster has put there own little "touches" into it whether to everyones liking or not, its your car that you built.:cool:

cheers
andy

Hi Andy,

The reason i ask is because i already own an arc welder and loads of 2.5mm rods and im reasonable at welding with them, but its difficult to weld less than 2mm thick, which im guessing is why everyone recommends buying a mig welder. Im trying to cut down costs and 1 of the major expeditures was on a mig welder, which would be £200+, i've tried to find a cheap one but to no avail.

So i thought why not get rid of it and just increase the thickness of the steel box meaning i can just weld it with my trusty arc welder since there dont seem to be too many downsides that i can see, 1 being it adds an extra 20kg to the chassis and the other being it will cost another £30 for the steel.

Im just wondering if there are actually any major reasons im missing as to why 1.6mm thick tube was chosen, which would mean that 2.5mm thick tube would not be appropriate.

ERW square tube, 1.6mm wall thickness, is the material required for the chassis.

By all means use RHS box to build you chassis. :rolleyes:

Sorry to put it bluntly but if you are willing to make bad choices in the name of cost at this early & critical stage, where will it end up :eek:

Ohh sorry i didnt realise it used ERW square tube, i've just been going on things i've read on the forum as i havent got my build manual yet. I'll give my local steel merchant a ring tomorrow and see what prices are like.

I have to say im not too much in the know about different kinds of mild steels, whats the difference between ERW and RHS?

my apologies i may have misunderstood your thoughts/questions.
i,m not the person to answer why 1.6 steel was chosen for the design ( maybe Chris will confirm the reason ).
i,ll be totally honest & say i had the same thoughts as you whereas i had the offer of free use of an arc welder ( my brothers ) before i started my build & asked the very same question... can i use an arc instead of a mig, i decided once i,d done more research into the building of the chassis that mig was the way to go,
i bought my mig off the "mig welding forum" second hand for £50, its a 150amp & came with 2 large pub style gas bottles so the bargains do come up now & again, guess i was lucky as it works perfectly.
i,m trying to build to a strict budget, ask Ash G :D ;) & as close to the book instructions that my ability will allow.
i think if you used the heavier gauge steel it may cause more probs than it alleviates at first.
best wishes for your build by the way.:)
cheers
andy

Don't use 2.5mm wall, not sure you can get the precision tube in that guage anyway. If not then it will be that black rubbish with only one square edge if you are lucky.
Why nost ask a forum member to make you one

I second this question, I am now concerned about using the wrong material.:( :confused:

I hate TLA's(Three Letter Acronym's)!:mad:

1.6mm can be stick welded if you are careful

ERW is the stuff to use rhs will usually be the black stuff and no good for a chassis as it isn't very square...

One major difference between RHS & ERW are the edge profiles.

RHS has a very pronounced rounded profile edge. Using this material will lead to a greater risk of welding distortion.

ERW is a precision electro welded sqare tube & has a very fine corner profile ;)

Yeah i've researching into welding 1.6mm, it would require buying some more rods and require a lot of practise as i dont want to end up blowing holes.

So does anyone know why ERW tube is used for chassis and the like? Whats so special about it? Does it add extra strength?

I have learned that ERW tube is made by taking a strip of metal and then folding or rolling it to the shape desired and then welding down the seam and cleaning off the outside weld.

ERW electric resistance welded, RHS really horrible stuff.:rolleyes:

With a bit of practice it's a breeze to stick weld 1.6mm.

ERW is electro resistant welded tube RHS is rolled hollow section....ERW is better quality where RHS is not so clever especially for a chassis.

Right looks like i might go down to my steel stockist and get some 1.6mm steel bar and have a practise. Someone on the mig welding forum has shown me a pic of where he's welded 1.6mm tube together using the 2.5mm rods im using so looks like i might just go down that route.

Im still curious as to why ERW is better though, what is it other than the corner profiles that makes it so much better.

RHS is black and full of crap where ERW bright and a better quality tube, there is a lot of iffy rhs out there and doesn't weld very well..

If your square tube is 1.6mm wall thickness it is almost certainly ERW ;)

RHS is not what you would call square and usually twisted where the ERW is precision tube.

The 1.6mm ERW was chosen because it's strong enough to do the job and it's light. Using RHS would make a strong and heavy chassis but it doesn't deform in the same way as ERW in an accident, the progressive collapse by buckling is preferable to joints breaking and possibly pushing tubes into the passenger compartment.

Cheers

Chris :)

Thanks for clearing that up Chris. Whats the cost difference between ERW and RHS?

i paid £9.70 per 6mtr for 25x25 1.6 and
£7.40 per 6 mtr 19x19 1.6
plus £15 delivery , i think total was £115ish
this was ERW

andy

Talk about bargain prices. May i ask who your steel supplier is and how far a field will they deliver to?

i haven,t got the receipt with me at mo ( its with my chassis, being built at mothers place), i,ll get you the details tomorrow & post it on here, not sure how far they deliver but imagine they would to your area,
they don,t hold the steel in stock, they are like a stockbroker, you place the order & they get the best deal for you.
the above prices included VAT too, as i said i,m building to strict budget :D ;)

andy

ok guys im gonna throw a big spanner in the works. the book states 16gauge box section. 16gauge is 0.0598inch thick so actually its 1.51mm.

sorry just being silly tonight

i dont know what your faffing about my arc welder will weld up 16gauge no problem. the trick is to strike the arc on the corner as its the most heat resistant bit.

The more you buy the cheaper it will be so why not get a few of you and do a "group buy" on the tube?....:D

Ahhhhh..... That will be the nominal thickness :D :D :D :o

So just to make sure, it will be 1.6mm, not 1.5?

i,m happy to ask my supplier for a good group deal & see if they,ll do multiple deliveries, or if you are local to me have it delivered to me & you collect = 1 delivery charge of £15. also they will cut it into 3mtr lengths if you wish.

andy

its known as 16gauge when i queried the dimensions with my supplier, its fine.
andy

Im up for a group buy if it would be feasible as i wont have the money for a few months so we could hopefully get a few people interested.

just to clear this up RHS = Rectangular Hollow Section. you need square box section also called SHS = Square Hollow Section.

ERW = Electronically Resistance Welded. this is one of the ways RHS and SHS are made.


What you want to order is SHS ERW bright mild steel 16gauge 25x25mm. which in simple terms is a shiney square metal tube with a weld all the way down one side of it.

Simples :D

Yes 1.6 ERW square tube is the material to ask your stockist for ;)

I believe that this tube has been made in both metric & imperial sizes, hence the 16 gauge 1" X 1" & 3/4" X 3/4"

My steel buyers guide lists only metric sizes for ERW. :)

Handy little snippet if you fancy a read.



Cold formed, electric resistance welded tubing can be produced in round, square or rectangle shapes. ERW tube is produced by processing a flat rolled steel into strips which are cold-formed, welded and seam annealed or normalized (depending on the manufacturer). You can usually identify ERW tube by the blue strip down one side of the tube (which is the welded area). The ERW process can guarantee the weld to be as strong or stronger than the rest of the tube body. The origin from a flat strip results in a more concentric product than Cold Drawn Seamless (CDS). ERW can also be known as CREW (Cold Rolled Electric Welded).
Typical Applications:
Structural columns, beams, supports, heavy equipment frames with 58,000 PSI tensile.

Cold Drawn Welded (CDW)
Produced from a steel strip by cold forming, electric resistance welding (ERW) and cold drawing to finished dimensions, CDW is the most versatile and widely sold mechanical tubing grade. A variety of thermal treatments can be applied to alter the mechanical properties and machinability. CDW is used for a tremendous variety of machine parts where close tolerances and higher mechanical properties are needed.
Typical Applications:
Automotive components, shock absorbers, hydraulic cylinders, sleeves, bushings, axles and shafting.

Drawn Over Mandrel (DOM)
DOM is formed from strip and Electric Resistance Welded (ERW) then cold drawn through a die and over a mandrel resulting in improved inner surfaces and dimensional quality. This process, called cold drawing, may be repeated more than once to reach the planned OD, ID, or wall dimension. Multiple draws can also be used to increase the strength or improve the surface finish of the tubes. During the drawing operation, the tubes may be process annealed to increase the ductility of the material. Lower cost alternative to CDS with equal or superior physical properties.
Typical Applications:
Machined parts, rollers, shafts, sleeves, steering columns, axle tubes, drive shafts, bushings and is most readily adaptable in cylinder applications with a 80,000 PSI tensile.

Cold Drawn Seamless (CDS)
General purpose seamless tubing, which is a solid bar of carbon steel drawn over a mandrel to form the tube section. CDS allows selection of chemistry and rough tube size. Cold drawing produces higher physical properties without heat treating. Offers widest range of sizes and chemistries in mechanical tubing. Better tolerances and reduced machining allowances over Hot Finished Seamless (HFS).
Typical Applications:
Machined parts, bushings, spacers, bearings, rollers, shafts, sleeves and cylinders with a 75,000 PSI tensile.

Cold Rolled Electric Welded (CREW)
Cold rolled steels are steels that are shaped by high pressure rollers at normal temperature in the steel mill. Cold rolling work hardens the material substantially. The steel is then welded by the electric weld process. A cold rolled steel can be either a mild steel or a high carbon steel. Can also be termed as ERW (Electric Resistance Welded). See » ERW

Hot Rolled Electric Welded (HREW)
Hot rolled steel is steel that is rolled to size in the mill while red hot. Hot rolling steel does not work harden it as much as cold rolling. For this reason, hot rolled steel is more easily machined than cold rolled.

What's the difference between Tube and Pipe?
The general term for pipe was that it was primarily used for carrying gas or liquid. It was not intended for structural use because the dimensions used in describing pipe was not dimensionally accurate. Measurement was referred to its inside diameter and wall thickness. The inside diameter was a true dimension, but over the years had become "nominal" (in name only) so that when pipe size was referred to, it was an approximate inside diameter measurement with the thickness described by the term "schedule".

shaved chicken legs and hairy mole ears

and breathe :D

Cats ears make nice comfy pads where bits on the chassis might rub you..:confused:

Ash, did you type that long thread or pasted it????:eek:
how,s the build?
andy