Making my own rear strut brace

[lolsteve]

So now I'm back at uni and what not I thought it would be a fun little side project to try and make my own rear strut brace. With the university having a machine lab I could get some dimensions drawn up and hopefully use the machinery there to cut out some brackets etc.

The shape seems fairly simple with a straight steel tube running between the struts and a simple enough bracket connecting to the two nuts.

My question is what kind of grade/thickness metal should I be looking to use, does it really matter or if I use too thin a sheet for the bracket could I risk it deforming somewhat. And what kind of welds should I be using? I'll have to go elsewhere for the welds since I don't recall seeing any welding equipment in the labs

[Piggy]

Ive made a few going back to ford/mitsi days.

a round connecting bar would be strongest as I found, but you need ideally a nice light alloy of some sort which is strong too. steel is more flexible than you think.

dimensions, if not making it adjustable, then ensure you make the cross bar slightly too small...thus tensioning it when you bolt it all in.

welding...has to be tig imo...keeps heat deformation to a minimal and looks the beesknees

[lolsteve]

Non adjustable, makes it a lot simpler. Steel is easier to get though and is it easier to weld? Thought ali couldn't be welded or is tricker?

This is the common shape people seem to make. Would it effect performance much if instead of a circle for the bolt to go through I have it so it could slide on
http://www.ebay.co.uk/itm/MG-Rover-REAR-...1c2c779866

There's also this one someone just put online, very basic looking
http://www.ebay.co.uk/itm/MG-ZR-ROVER-25...4ac9d6993d

[Piggy]

second one looks a bit useless to be honest.

box section wont be very strong either IMO.

dont mean to sound annoying...but that first one isnt that expensive

[lolsteve]

Was thinking the second looked crap, as a civil engineer I agree box sections aren't the best a nice I beam wouldn't go amiss

Oh I know it's not , its more of a I have free time/access to equipment and won't need it for a while now so might as well have a bit of fun designing it or whatever

[Martin306]

Make 2 brackets which go on the top of the struts, and a bolt on I beam between them?

No welding required easy as pie, and no weak spots.

Mig welding is fine, you won't warp anything unless you're using too much current. of course all welding creates heat and weak spots.

I'd stick to steel, when you weld alloys you need to use a feed wire which won't react with the alloy and weaken the joint over time.

[Rippthrough]

I beams don't have much torsional stiffness at all, they warp all over the shop.

[lolsteve]

Make 2 brackets which go on the top of the struts, and a bolt on I beam between them?

No welding required easy as pie, and no weak spots.

Mig welding is fine, you won't warp anything unless you're using too much current. of course all welding creates heat and weak spots.

I'd stick to steel, when you weld alloys you need to use a feed wire which won't react with the alloy and weaken the joint over time.

Not a bad idea, certainly easier but could look a little half arsed if it's just bolted together. That and I don't know how small an I beam I could get, structural sizes might be a little overkill/heavy
Going to have to see what the uni has in terms of welding machinery, otherwise might have to see if anyone on here will let me borrow/teach me to weld

I beams don't have much torsional stiffness at all, they warp all over the shop.

Not heard of I beams having torsional problems since although you have to test for torsional bending when you put a solid wall directly on one I've yet to come across an example where the beam passed deflection but failed the torsion. But then again I dont really design them for that purpose often, more deflection or compression. But its unlikely I'd actually use one in this project. Will just go for a circular cross section since it's easy and it works

[Rippthrough]

Most applications for I-beams see very little torsional stress, so the stiffness isn't an issue, for a strut brace connecting to one side of a tower, it very much is.

Just use some tube.
And don't do the normal trick (and the same as the first link), and make the transistion from your stiff beam to a weak, floppy plate happen in 1mm, all that does is concentrate the stress there and make it flex on the joint.
That why my braces run tube all the way to the bolts.

[lolsteve]

Most applications for I-beams see very little torsional stress, so the stiffness isn't an issue, for a strut brace connecting to one side of a tower, it very much is.

Just use some tube.
And don't do the normal trick (and the same as the first link), and make the transistion from your stiff beam to a weak, floppy plate happen in 1mm, all that does is concentrate the stress there and make it flex on the joint.
That why my braces run tube all the way to the bolts.

So make sure the tube overlaps the plate somewhat? and up to the top bit as much as I can like this? It's crude but the idea is there . What thickness plate as a minimum would you recommend if it was just a cheap steel grade?

[tigerstyle]

Thought ali couldn't be welded

as a civil engineer

Jesus wept.

[lolsteve]

Who uses aluminium or at least in thin quantities for construction? Only ever had to do steel frame building.
If it's construction it's either concrete or steel anything else not my business

[John1.4]

imo if you're definately going to make one rather than buying, then i'd personally go for stainless tube / plate, tig welded,

   

bit overkill maybe but you get the idea

[Piggy]

^^^^ spot on info and design imo

[Rippthrough]

Who uses aluminium or at least in thin quantities for construction? Only ever had to do steel frame building.
If it's construction it's either concrete or steel anything else not my business

I know where there's plenty of aluminium bridges. Like dozens of them...

[swampy]

Who uses aluminium or at least in thin quantities for construction? Only ever had to do steel frame building.
If it's construction it's either concrete or steel anything else not my business

I know where there's plenty of aluminium bridges. Like dozens of them...

Yep plenty of bridges made from ally!!

Search br90 I worked on that project for vice years!!

Amazing bit of kit!!

Vickers engineering in Wolverhampton were trying to replicate the bridge but using carbon fibre for the majority of it

[lolsteve]

Who uses aluminium or at least in thin quantities for construction? Only ever had to do steel frame building.
If it's construction it's either concrete or steel anything else not my business

I know where there's plenty of aluminium bridges. Like dozens of them...

Well in the three years of uni not once has the use of ali been suggested, I assumed it was due to steel being more cost effective.
It's just "use steel and if you're not using steel why aren't you using steel? are you a poof or something?!"

Who uses aluminium or at least in thin quantities for construction? Only ever had to do steel frame building.
If it's construction it's either concrete or steel anything else not my business

I know where there's plenty of aluminium bridges. Like dozens of them...

Yep plenty of bridges made from ally!!

Search br90 I worked on that project for vice years!!

Amazing bit of kit!!

Vickers engineering in Wolverhampton were trying to replicate the bridge but using carbon fibre for the majority of it

I guess mobile bridge systems are a bit different, in the sense I'm guessing their budgets and specifications required are different to a standard steel truss


But anyway enough about bridges, thinking john1.4's design is looking pretty spot on. Simple enough but looks strong enough

[Scott]

It's just "use steel and if you're not using steel why aren't you using steel? are you a poof or something?!"

[cjm_harris]

Need to get acquainted with peoples usernames and cars I think. Opened this thread thinking "wtf, rear strut brace... hmm"



Edit: Whats worse is I've met Steve, dammit!

[THE_Liam]

Who uses aluminium or at least in thin quantities for construction? Only ever had to do steel frame building.
If it's construction it's either concrete or steel anything else not my business

Fill the boot with concrete? Stiff as f*ck!

[Jenkosowls]

Who uses aluminium or at least in thin quantities for construction? Only ever had to do steel frame building.
If it's construction it's either concrete or steel anything else not my business

Fill the boot with concrete? Stiff as f*ck!

Structural foam.... Some ones done it!

[Rippthrough]

Yeah, me, my sills and a-pillars are full of it

[lolsteve]

Currently making up some bracket templates, in regards to welding how much space should there be either side of the tube. Going to go to the university labs Monday and see what they can do for me

[cwspellowe]

Who uses aluminium or at least in thin quantities for construction? Only ever had to do steel frame building.
If it's construction it's either concrete or steel anything else not my business

Fill the boot with concrete? Stiff as f*ck!

Structural foam.... Some ones done it!

yeah and what an impressive job of it he did too. Shame he had no boot space left after..

[Jonny b]

Fill the boot with concrete!!!! Lol ιts not a Capri
( oldies will know)

[lolsteve]

Fill the boot with concrete!!!! Lol ιts not a Capri
( oldies will know)

rear wheel drive + snow?

[devils_fuel]

Fill the boot with concrete!!!! Lol ιts not a Capri
( oldies will know)

Yeah they were a bit tail happy..

[samass]

Fill the boot with concrete? Stiff as f*ck!

Structural foam.... Some ones done it!

yeah and what an impressive job of it he did too. Shame he had no boot space left after..

Or wheel arch space! Think of all the weight I saved when I cut it out tho....