Stiffened rear ARB

[GeoffBob]

I saw the bars that tie the strut tops into the cage, the problem is that they're pointing the wrong way to do the work of a strut brace.
Think about it like this : each bar looks to be about 500mm long. If you had that length of bar welded firmly to something at one end, you would still be able to move the free end sideways a few mm by hand - standing on it would displace it by 10mm or more.
This is comparable to the load this area would see during hard cornering, where 10mm of movement translates to 1 degree of negative camber lost

Handpaper. I'll make up and fit a strutbrace if I need to. But I really do think you'd need to see the construction of the frame in person to fully appreciate its strength. The bars are only 375mm long and run diagonal to the frame. Also, the strut towers are from 3mm plate. To push the two towers towards each other the front and rear plates of each tower would have to go into tension. Even without the EN36 pipes joining them to the frame, they are incredibly rigid. The main part of each strut tower is actually made from two plates, one either side of the frame rail. The photo below shows the right tower in the early stages of construction before the second plate was fitted. So these towers are very three dimensional in their construction.



I'm afraid that you're just going to have to trust that I know what I'm talking about and am well familiar with a) how to build rigid structures, and b) when and where a strut brace is required. And believe me, if one ever is required, I won't hesitate to fit it.



I'm glad that you have such a wide availability of springs where you are. Down here in the 3rd world we are not so privileged.

[handpaper]

OK, the strut towers are rigid, your last picture has convinced me Nice work on the engine pylon, by the way. I'd still contend that the best way to oppose a force is directly though.

Any criticism aside, it's a very impressive project and I hope to do something similar one day.

There may be some advantages to living in the 3rd world (not sure I'd count SA as such, though). I'll wager you don't get greedy stockholders trying to charge you over 500 ZAR for a 600x300x3mm mild steel sheet

[GeoffBob]

Nice work on the engine pylon, by the way.

So that's what you call 'em! Never knew their real name till now. I used to to just call 'em "them there metal bits atop the rubber disky things"

I'd still contend that the best way to oppose a force is directly though..

I agree. And I meant what I said, if she needs a strut brace she'll certainly get one. I'm no idiot (by my own retarded definition), I have all the space in the world to fit one in and I would be stupid not to do it - if she needs one.

Any criticism aside, it's a very impressive project and I hope to do something similar one day.

Many thanks. Not my first project car by any means, but certainly my most ambitious thus far. The fact that the R5Turbo and E30 have such similar track width meant that this car was just crying out to be built!

There may be some advantages to living in the 3rd world (not sure I'd count SA as such, though). I'll wager you don't get greedy stockholders trying to charge you over 500 ZAR for a 600x300x3mm mild steel sheet

Steel prices went through the roof a year or so ago, driven largely by the development in China I think. Things seem to have calmed down a bit now. Luckily I had already bought most of the steel for my project before the prices climbed.

BTW, aside from the engine and drivetrain, my frame is the only other really heavy item in the car. But don't let that deceive you, she's not much bigger than an old mini. To keep the total weight down I manufactured the firewall and floorpan from 2mm aluminium. Cutting out all the shapes and welding them together took absolutely forever. I'm lucky enough to have my own AC/DC argon TIG welder, good for both ferrous and aluminium. I get such a huge kick out of working with aluminium. Once you get the hang of it, it is such a wonderful material to work with. I often go looking for things to make from aluminium, just to give me something to do. I even went so far as to re-skin the doors in aluminium.

[caneswell]

Yours is an interesting build, though I would advise adding some form of strut brace. There doesn't seem to be mch preventing the front strut tops from moving together under cornering

Interesting thread guys!

I think strut tops are forced apart under cornering loads though. Do a free body diagram. If they did move together it wouldn't be a problem really, just some more camber gain

[handpaper]

caneswell - Yep, strut tops do move apart under cornering load. I corrected myself in my next post

Geoff, you're a bad man. You've got me looking at TIG welders now; my old MIG isn't good enough any more
I love welding of any kind, for any reason ("Dad, my bike's broken" "BZZZzzzssssTsssssTssssssst" "Done. Paint it before you put it away, or it'll rust"), but I'd like to be able to weld more stuff, more neatly.
I have managed to MIG Aluminum* successfully, but it wasn't pretty:






*It's 'Aluminum', OK? Not Aluminium. The oxide is Alumina, the metal is Aluminum. Just for once, the Yanks have it right. Now if they could only learn to pronounce 'nuclear'.....

[GeoffBob]

Geoff, you're a bad man. You've got me looking at TIG welders now

We use big MIG welders for welding armour plate here at work, and frankly they do an excellent job. They are also excellent for tacking small jobs together where you don't wan't to put a lot of heat in.

I almost bought a small MIG instead of my TIG machine. I am so glad I didn't (as my first machine) as the TIG can do so many other jobs the MIG can't. Plus, I didn't like the idea of having to go back to Licoln Electric every time I needed flux cored aluminium MIG wire. I'd still like to get a small MIG one day though, mostly for tacking sheetmetal, exhausts etc..

This is my AC/DC TIG Welder:



It's a 220VAC single-phase input with 5-200A AC/DC/pulsed output, and it wasn't that expensive. Maximum duty cycle is about 60%, so its great for home jobs, but a bit light for heavy industrial. I was so impressed with this machine that I bought its big brother, a 3-phase 350A machine, for our workshop at work. The bigger one includes a water cooled torch and is good for heavy industrial work.

The thing about aluminium welding is to keep the job absolutely clean. It's best to soak an oil fouled sump or tappet cover in Acetone for a day at least, else the weld could be porous due to spots of carbonisded oil. At least that's how it is with a TIG machine. I'm not sure about with a MIG.

FYI, I have posted some documents on welding aluminium here, here and here for you to download.

It's 'Aluminum', OK? Not Aluminium. The oxide is Alumina, the metal is Aluminum. Just for once, the Yanks have it right. Now if they could only learn to pronounce 'nuclear'.....

Yeh, Like Barum, Strontum, Uranum, Magnesum, Potasum, Chromum, Helum, Lithum .......

Sorry, I'm stuck in my ways - It'll always be Aluminium to me. I used to work for the Nuclear Energy Corporation. We used to call it the Unclear Energy Corporation.

[UweM3]

GeoffBob, that welder looks exactly like one I was tempted to buy when I bought my made in china TIG welder, just yellow insted of green. They are quite good machines for the money I am really really happy with mine and wish I would have bought the model you have. There is a lot of stuff I would like to make in ALUMINIUM, but have to use Stainless or Mildsteel because that's all I can weld at home.

[GeoffBob]

GeoffBob, that welder looks exactly like one I was tempted to buy when I bought my made in china TIG welder, just yellow insted of green. They are quite good machines for the money I am really really happy with mine and wish I would have bought the model you have. There is a lot of stuff I would like to make in ALUMINIUM, but have to use Stainless or Mildsteel because that's all I can weld at home.

Thanks Uwe. I'm told its an American design mass produced in China. The instruction manual is written in Chinglish. I was initially very cautious about buying it, but I've had no problems thus far. Its about 1/4 the price of an equivalent Licoln Electric machine.

[UweM3]

GeoffBob, that welder looks exactly like one I was tempted to buy when I bought my made in china TIG welder, just yellow insted of green. They are quite good machines for the money I am really really happy with mine and wish I would have bought the model you have. There is a lot of stuff I would like to make in ALUMINIUM, but have to use Stainless or Mildsteel because that's all I can weld at home.

Thanks Uwe. I'm told its an American design mass produced in China. The instruction manual is written in Chinglish. I was initially very cautious about buying it, but I've had no problems thus far. Its about 1/4 the price of an equivalent Licoln Electric machine.

LoooL, mine says it's a german design made in China!!!!

Have you seen the combi machines they do? AD/DC TIG welder AND a plasma cutter!!!!

[handpaper]

What's the issue with welding other metals, Uwe? If you're welding stainless you should be using CO2/Argon mix, so just swap to pure Argon and you should be ready to go. Or am I missing something?

I agree Geoff, sometimes MIG fits the bill very nicely. It's perfect for a quick and dirty job, but capable of much more in the right hands. Occasionally it produces good results even in my untutored mitts

flux cored aluminium MIG wire

Gasless MIG? For Al?

Have you seen the combi machines they do? AD/DC TIG welder AND a plasma cutter!!!!

Very tempting! Would also need a compressor, but I still think the neighbors would prefer it to my current 'weapon of choice', the 9" angle grinder
Plus, of course, it cuts curves

My (SiP MigMate 100) welder cost me 50 quid plus two pizzas and was carried 30 miles home bungeed to the back of a motorbike
That was ten years ago, I think it's paid for itself now (two gates, one towbar, one trailer, a set of coilovers, numerous car and kart repairs and endless little as-needed fabrications).

[billgatese30]

My brother has a rehnmann (or however you spell it) DC TIG from eBay which is a "german designed" chinese welder, it sounds very similar to what you guys have.

Its awesome for stainless/mild but we would love the ability to do Ali.


The good thing about welder/plasma cutter combos is they use the same technology, but instead of letting the weld pool cool and fuse, it blows it away with compressed air, leaving the cut, thats next on my list and should hopefully let us contend with any possible manufacturing/fabrication problem we may encounter.

[UweM3]

What's the issue with welding other metals, Uwe? If you're welding stainless you should be using CO2/Argon mix, so just swap to pure Argon and you should be ready to go. Or am I missing something?

Argon/CO or "Argomix" or "Argoshield" is only good for mild steel.
Stainless/Aluminium is always welded with pure Argon.

To weld Aluminium you need a different Tungsten and AC current.

Mildstee and Stainless can be welded with DC.

I agree Geoff, sometimes MIG fits the bill very nicely. It's perfect for a quick and dirty job, but capable of much more in the right hands. Occasionally it produces good results even in my untutored mitts

A good MIG weld starts with the preparation. Not only talking about the cleaness of the metal, it's the size of the gap or chamfer. MIG can produce nice welds if handled right.
One of the most common mistakes I see is that inexperienced welders "pull" the torch when welding. Your welding direction is always to "push" along the weld. This also allows you to see WHERE you weld

Have you seen the combi machines they do? AD/DC TIG welder AND a plasma cutter!!!!

Very tempting! Would also need a compressor, but I still think the neighbors would prefer it to my current 'weapon of choice', the 9" angle grinder
Plus, of course, it cuts curves

Only downside of a plasma cutter is the need to "clean" the cut edge (grinding it to bare metal) because the plasma cutting process deposits a layer of carbon on the cut edge and thats no good for welding with out little machines

My (SiP MigMate 100) welder cost me 50 quid plus two pizzas and was carried 30 miles home bungeed to the back of a motorbike
That was ten years ago, I think it's paid for itself now (two gates, one towbar, one trailer, a set of coilovers, numerous car and kart repairs and endless little as-needed fabrications).

I think mine is same, just different name. Bought it from a friend for pennies and never thought it would be any good. But the little thing has surprised me more than once. It's just the lack of different settings what lets it down.

[GeoffBob]

LoooL, mine says it's a german design made in China!!!!

Have you seen the combi machines they do? AD/DC TIG welder AND a plasma cutter!!!!

Probably is a German design - I'm not sure the Yanks design too much hardware for the continental curent, although Lincoln Electric have a 220V 50Hz AC range, so maybe .. ?

Yeh, plasma cutter would be real handy to have.