Aluminum chassis thoughts?

"BaconSandwich is tasty." (baconsandwich)
08/27/2014 at 22:16 • Filed to: None

It's surprisingly difficult to find small amounts of rectangular aluminum tubing...

A few weeks ago I needed to re-build a fence for a table saw. I had to track down some rectangular aluminum tubing. Unfortunately the only place I found would sell it in 20 ft lengths, and I only needed 1.5 feet or so.

Instead, I went to Princess Auto (picture: Canada's Harbor Freight), got a 4 foot piece of steel tubing instead. I had to do a bunch more grinding, but it seems to have mostly worked.

I've been thinking it would be cool to eventually build my own locost with an aluminum frame. At least now I know where to get the aluminum tubing. I do wonder though, how well would aluminum hold up compared to steel? I'd be a bit more worried about stress fractures and the like.

Thoughts?

DISCUSSION (27)

Jeff-God-of-Biscuits > BaconSandwich is tasty.
08/27/2014 at 22:23

You might also try Home Depot, they usually carry 3 and 6 foot lengths of stuff.

GhostZ > BaconSandwich is tasty.
08/27/2014 at 22:23

I would think you'd have to change the shape of the frame in order to use aluminum. I'm not a mechanic or welder or anything, but despite its light weight, isn't aluminum's strength-per-volume lower than Steel? So if you copy a steel chassis over to aluminum without changing the shape, density, or volume, wouldn't it be lighter, but also noticeably weaker?

Arch Duke Maxyenko, Shit Talk Extraordinaire > BaconSandwich is tasty.
08/27/2014 at 22:23

Size your tubing appropriately for the stress it will encounter.

/goshi'msohelpful

tc_corty > BaconSandwich is tasty.
08/27/2014 at 22:24

Are you going to Tig it or use bolts? Ally is a bitch to weld if you're the self teacher, takes ages to master. I haven't yet, not even close. From what I understand is the strength of the frame comes from design as much as the material. You could build a chassis out of drinking straws if you designed it right. What are you wanting to make the chassis for?

Biased Plies > BaconSandwich is tasty.
08/27/2014 at 22:25

Definitely be worried about stress fractures in an aluminum chassis locost. You won't simply be able to replace steel with aluminum in the plans that are out there and unless you are an engineer and are able to calculate the appropriate tubing sizes and determine welding requirements I wouldn't recommend simply trying it.

Phyrxes once again has a wagon! > BaconSandwich is tasty.
08/27/2014 at 22:31

I"m not sure if they distribute to canada but onlinemetals.com is who i've used in the past.

Biased Plies > GhostZ
08/27/2014 at 22:33

Yes, it would be weaker. You'd have to step up the tubing wall thickness (if keeping the same external tubing dimensions) or increase the tubing size altogether. Welding aluminum is also a bit trickier than doing so for steel, I'd recommend (hiring or being) a professional welding with aluminum experience if you want to have a chassis built out of it.

Combine all that with a much shorter fatigue life and I'd probably just stick to steel and well proven plans that already exist.

Biased Plies > tc_corty
08/27/2014 at 22:36

Kinja'd!!!

He mentioned a 'locost', which is basically just a scratch-built lotus 7/Caterham replica.

GhostZ > Biased Plies
08/27/2014 at 22:37

I figure for the cost of an aluminum frame the car would be faster if you put the difference of cost for aluminum into suspension, engine, aero, and tires instead.

desertdog5051 > BaconSandwich is tasty.
08/27/2014 at 22:41

What is the alloy of the aluminum? This will make a huge difference. Why sacrifice strength of your chassis to go with aluminium. (oops, British got in the way). Save weight in other areas.

Biased Plies > GhostZ
08/27/2014 at 22:42

Yeah, especially if you were to have it professionally welded that money could definitely be better spent elsewhere. Plus I think I'd prefer to have the satisfaction of doing it all myself and not go too far outside of my abilities/knowledge.

tc_corty > Biased Plies
08/27/2014 at 22:46

ooooohhhh k haha I read it as a typo for low cost. Cheers for pointing that out to me :)

BaconSandwich is tasty. > desertdog5051
08/27/2014 at 23:12

Honestly, I haven't looked into it too much. I just like the idea. That, and saving weight right from the start would be nice.

BaconSandwich is tasty. > Phyrxes once again has a wagon!
08/27/2014 at 23:13

Unfortunately their shipping to Canada is crazy expensive.

BaconSandwich is tasty. > Biased Plies
08/27/2014 at 23:13

Oh, I don't plan on it. Just a crazy idea at this point.

BaconSandwich is tasty. > tc_corty
08/27/2014 at 23:15

Ideally TIG.

Another crazy idea: buy an old 1940's Chevy truck. Drop it on a new frame and make a hybrid electric small gas engine turbocharged drive-line. Because life isn't complicated enough already.

Phyrxes once again has a wagon! > BaconSandwich is tasty.
08/27/2014 at 23:49

What part of Canada? I can ask some teams that do competitive robotics in Canada who their suppliers are if you can narrow that down.

tc_corty > BaconSandwich is tasty.
08/27/2014 at 23:54

Ive toyed with ideas similar to that. Trade some economy for power though. Along the lines of that supercar that has that fuck off awesome set up, but not as extreme. Toyed with the idea of having an electric motor connected to the pinion on the diff. Without going through the head ache of joining it with the motor to go through the gear box. Sure it wouldn't be at it full potential, I don't even know if it'd work for all but hey. There's electric cars running some really decent times down the quarter. And the sparks that would fly out would be awesome. I think its a mx-5 or something. It would be complicated but fun complicated, not can't be fucked complicated.

Kailand09 > BaconSandwich is tasty.
08/28/2014 at 06:27

Using aluminum in a vehicle frame would be an extremely difficult feat, to be honest. It's simple to understand that for certain weight vehicles you can do simple calculations to figure out the OD and ID of a, say, DOM 1020 steel for a frame. This would all need to be done with proper design, putting the correct bracing where it is needed (and less bracing where you don't want as much strength or a crumple zone).

Aluminum would require more than just a simple tube, and if you look up what Ford does for just the doors on the new F-150 out of aluminum, it is a highly engineered design. Cool stuff though. Either way I wouldn't touch it on my own, at least not for a long time (in a car).

We used aluminum castings in a few structural applications, it isn't really the most trivial material to use... unfortunately.

Phyrxes once again has a wagon! > BaconSandwich is tasty.
08/28/2014 at 07:05

This vendor comes recommended, the person who suggested it is local to Toronto where they have many locations but they also have two locations in Alberta. I will update if anybody else makes any other suggestions.

http://metalsupermarkets.com/store-finder/

BaconSandwich is tasty. > Phyrxes once again has a wagon!
08/28/2014 at 23:20

Awesome. I never knew these guys existed. Good find!

BaconSandwich is tasty. > Kailand09
08/28/2014 at 23:21

Good to know.

I do find it interesting that Ford is using a ton of riveting rather then TIG welding. Maybe more time/cost effective?

BaconSandwich is tasty. > Phyrxes once again has a wagon!
08/28/2014 at 23:22

Western Canada - in particular Southern Alberta.

Kailand09 > BaconSandwich is tasty.
08/28/2014 at 23:35

Yeah. That and there's a huge shortage of skilled welders... I'm sure that is part of the issue as well (though definitely not a huge chunk). It becomes expensive and takes lots of time to get TIG welding done. Also, proper welding on aluminum isn't as easy as your regular old mild steel. Unless done by a machine (making things more difficult), a rivet could be more consistent. These are just guesses at this point though, as there are many scenarios that arise during the design phase that really only the engineers working on it will know about, leading to decisions like this. It could be that for whatever reason the geometry of the structural parts just wasn't easy to weld either.

The company I work for uses a LOT of welders. Definitely not the easiest and most economical way to go about doing things, but in some applications you have no choice.

Kailand09 > BaconSandwich is tasty.
08/28/2014 at 23:37

Now that I think about it, the weight factor could be part of it as well. They are probably quite thin thickness parts, and welding onto that may have complicated things further. A lightweight rivet is pretty strong, and then messing with the thin material by TIG welding is then avoided.

Thin materials will also have different behaviors to welding as compared to a thicker more dense material, so that could have caused mechanical property issues on the thin material. Again, this is all just guesses, but not unlikely scenarios they went through.

BaconSandwich is tasty. > Kailand09
08/30/2014 at 10:59

Those are definitely some valid points. I imagine getting a robot to TIG weld is quite a bit trickier.

BaconSandwich is tasty. > Kailand09
08/30/2014 at 11:00

That's definitely also a possibility. I do imagine it is hard to weld some of that thin stuff, as there'd be a lot of warping.