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What material to make a strut brace
smart51 - 22/9/09 at 08:50 AM

I'm going to make a strut brace for my cappuccino. I'm debating making it out of 3mm mild steel plate and 16g ERW tubing and painting it or making it out of stainless, which won't need paint. Is there any reason why one material is less suitable than the other?

Mr Whippy - 22/9/09 at 09:00 AM

seen this one?

linky

Peteff - 22/9/09 at 09:32 AM

I wouldn't think either would cause any problem just the mild steel is easier to weld with no special gas or wire required and cheaper to buy.

smart51 - 22/9/09 at 10:01 AM

quote:
Originally posted by Peteff
the mild steel is easier to weld with no special gas or wire required and cheaper to buy.


Yeah, but then the mild has to be degreased and painted meaning the final cost is about the same. Is stainless actually harder to weld, even if you have the right gas and wire?

Thanks for the link Whippy. That particular one is made by cosco and is fitted to Jaik's car in the picture. They're about twice the cost of making one yourself, which I suppose is fair.

02GF74 - 22/9/09 at 10:21 AM

the properties of both materials differ - I would suggest you google the difference to see if stainless is a suitable material; from what I rmember, and it is not a lot, is that stianless is more brittle - whenter that is correct or not is for you ti find out.

read this for starters: http://www.euro-inox.org/pdf/auto/StructuralAutomotiveApp_EN.pdf

I am sure if the size/thickness is designed wiselym stinaless is ok.

oh, as you say, the prep for mild means final cost will be about the smae I vote stainless.

blakep82 - 22/9/09 at 12:17 PM

is 3mm plate enough? it just doesn't seem very thick to me?

oadamo - 22/9/09 at 12:33 PM

why not make the end plates out of steel and the bar stainless
adam

oadamo - 22/9/09 at 12:34 PM

something like this

http://www.strutbrace.co.uk/peugeot/206.htm

oadamo - 22/9/09 at 12:38 PM

or how about this badboy lol.

http://www.strutbrace.co.uk/subaru/Impreza%20(1992%20-%202001).htm

smart51 - 22/9/09 at 01:28 PM

quote:
Originally posted by blakep82
is 3mm plate enough? it just doesn't seem very thick to me?


Aren't locost wishbone brackets made from 3mm plate?

tegwin - 22/9/09 at 01:38 PM

Mig welding stainless is a bit of a PITA!

You need more current than for mild steel to get a good weld going...

The average 150 hobby MIG set is not really up to the job...

I have Migged some stainless and honestly, its not worth the hassle... you will end up with shagged rollers, torn liner and mediocre welds...

Make it from MS and paint it!

jacko - 22/9/09 at 03:38 PM

how about this on my son's car it may give you some ideas
r34engine /2
r34engine /2
Jacko

MikeRJ - 22/9/09 at 04:09 PM

quote:
Originally posted by smart51
quote:
Originally posted by blakep82
is 3mm plate enough? it just doesn't seem very thick to me?


Aren't locost wishbone brackets made from 3mm plate?


Strut braces need to be extremely rigid if they are to be effective, since the amount of movement between strut tops is pretty small. The majority of strut braces that have bends in them are pretty much decorative IMO.

smart51 - 22/9/09 at 05:41 PM

Thicker stuff is no problem, except for my little welder. My design doesn't put a bend in the tube but the result is that the webs that it bolts too are fairly tall (90mm). perhaps cutting out a piece of rectangular box section might be stiffer, with webs on the corners to spread the load onto the round plates.

Ivan - 22/9/09 at 06:29 PM

Slight hijack warning - why do some braces have hinged joint near strut mount and others not? When do you decide which is needed?

smart51 - 22/9/09 at 07:43 PM

Some come in 3 pieces. They allow small differences between cars to be taken up by the bolts. They shouldn't move when tightened but are more complicated and so expensive to make.

Solid ones are cheaper to make and you might imagine slightly more rigid, provided your car is straight and right on tolerance, you should be fine.

Mine will have a removable centre piece for ease of engine servicing. Easier to remove 2 accesible bolts than 6 nuts that hold your suspension on.

MikeRJ - 22/9/09 at 08:58 PM

quote:
Originally posted by jacko
how about this on my son's car it may give you some ideas


Decorative I'm afraid. Put any significant compressive force into that brace and it will just bend (and straighten out with tensile force). Just like you wouldn't use bent chassis members in a space frame unless you greatly oversize them to make up for the loss in strength.

Sadly it seems a lot of aftermarket performance parts like this have very little in the way of sound engineering behind them. I guess shiny parts sell a lot better than plain but functional ones.

smart51, you will definitely have to make the brackets quite sturdy if they are that tall, feed the loads as close as possible to the strut mounting bolts (or add extra bolts).

smart51 - 22/9/09 at 09:03 PM

quote:
Originally posted by MikeRJ
smart51, you will definitely have to make the brackets quite sturdy if they are that tall, feed the loads as close as possible to the strut mounting bolts (or add extra bolts).


Sound advice. I'm playing with cardboard models at the moment so will keep that in mind.

David Jenkins - 22/9/09 at 09:26 PM

quote:
Originally posted by smart51

Sound advice. I'm playing with cardboard models at the moment so will keep that in mind.


I don't think that cardboard will be strong enough...