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PostPosted: April 27, 2022, 12:17 pm 
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Joined: June 28, 2016, 9:21 pm
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I found some sources of aluminum square tubings. Anyone has tried building frame out of alumium tubings? Is welding aluminum more difficult than steel? Can it be done by a welding layman? What kind of welders to use?


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PostPosted: April 27, 2022, 1:44 pm 
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Some good reading:
http://locostusa.com/forums/viewtopic.php?f=39&t=13092

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PostPosted: April 27, 2022, 2:51 pm 
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yuta wrote:
I found some sources of aluminum square tubings. Anyone has tried building frame out of alumium tubings? Is welding aluminum more difficult than steel? Can it be done by a welding layman? What kind of welders to use?


Consider using steel square tube that fits snuggly inside (or outside) the aluminium to make the joints with, rather than welding the aluminium. Use epoxy and rivets for the joints.

I'll maintain that you can build a steel frame that is barely heavier a lot easier and cheaper at the end of the day, unless you are getting your aluminium for free or something.


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PostPosted: April 27, 2022, 3:17 pm 
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yuta wrote:
I found some sources of aluminum square tubings. Anyone has tried building frame out of alumium tubings? Is welding aluminum more difficult than steel? Can it be done by a welding layman? What kind of welders to use?


MUCH more difficult IMO. MIG welding steel with shielding gas is about the easiest method for beginners to use and still get strong joints. It may not be pretty, but strong enough. IT takes a lot of practice to weld aluminum. I am still scared to trust my aluminum welding.

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PostPosted: April 29, 2022, 11:13 pm 
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In my opinion, threefeatures weigh against an aluminum frame

1) Fatigue limit. Aluminum has no fatigue limit. That is, after a number of cycles it WILL fail. Imagine the Golden Gate bridge made of aluminum, and a single fly lands on it, then takes off again, then lands again. Eventually, over time the bridge will fatigue fail. Most probably not in our lifetime, but it will fail. (No it didn't say how big the fly was... but that's irrelevant.) Fatigue life is based on the level of stress the material sees. Do you know what the stress will be in your aluminum structure,and repetition frequency? To quote Dirty Harry- Feel lucky punk? :D

Steel, in contrast, does have a fatigue limit. If stresses are kept below a certain level, the structure will never fail in fatigue

2) Elastic modulus. Aluminum is 1/3 as stiff as a similiar cross section of steel. Sure,you can upsize the tubing the recover the structure's stiffness,

3) Ease (or lack thereof) of use. If using MIG, you need either a push-pull system w/ teflon cable liners or a spool gun. Use Argon rather than C25. If using TIG, the system must be capable of A/C welding current. Many economy systems aren't. Also need to know alloy composition of the base and fill metals. As a ferinstance, 6xxx series aluminums are prone to silicone nodule cracking when the weld refreezes, so typically something like 4047 filler is used to move silicon concentration out of the zone of succeptability. Nothing insurmountable, but... Feel really lucky, punk?

Was it Chapman that said "Mild Steel is the sportsman's friend"?


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PostPosted: May 1, 2022, 5:45 pm 
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Porsche saved a few kgs making the 917 spaceframe out of aluminium. They pressurised them to ensure that there were no cracks and watched that gauge during the race. The frames were lifed for one race and they had to make 6 to get a good one. Lotus do pretty well with bonded chassis for the Elise, I would research that technology as it's fairly well proven. If you are building a road car choose durability.


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PostPosted: May 2, 2022, 8:25 am 
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You would just not make a stick frame out of Aluminum. AL open the door to the monocoque chassis because it was the best uses of the properties of AL, Lotus pioneered the extrusions and glue technique. Carbon Fiber has lead to the another style of construction to use the best properties on CF. You would not make tubes out of CF and use plugs to build a stick chassis, you could, but it makes no sense.

Graham


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