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Old 04-08-2011, 05:40 AM   #1
jtwind OP
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Airhead subframe tubing ??

I need to make some new main braces on a /5 dirtbike subframe. They will curve around the shocks so will need to bend them alittle. Any ideas/suggestions on what to use. I assume the airheads just used mild steel, but frankly don't know much about it all. I looked at some carbon steel tubing online and lots of wall thickness etc. Thanks.
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Old 04-08-2011, 07:47 AM   #2
Airhead Wrangler
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I know that the R80G/S subframe (and the GS as well, I'm pretty sure) used 18mm OD mild steel tubing. The wall thickness on the GS subframe is 3mm (very beefy) whereas that of the R80G/S is much thinner, but I don't have a number.
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Old 04-08-2011, 09:14 AM   #3
jtwind OP
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Quote:
Originally Posted by Airhead Wrangler View Post
I know that the R80G/S subframe (and the GS as well, I'm pretty sure) used 18mm OD mild steel tubing. The wall thickness on the GS subframe is 3mm (very beefy) whereas that of the R80G/S is much thinner, but I don't have a number.

That helps, I like beefy, thanks much!!
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"Between two explanations, choose the clearest; between two forms,
the most elementary; between two expressions, the shortest."
Between two motorcycles the simplest (DW)
Eugeni d' Ors (1881-1954); Spanish writer.


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Old 04-08-2011, 09:40 AM   #4
Airhead Wrangler
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Beefy, but not unbreakable

http://www.flickr.com/photos/colinseven/4303231223/

Actually I was wrong about the 3mm part. It's thicker, but I can't tell for sure without cutting my subframe open. 18mm OD is correct.
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Old 04-08-2011, 10:32 AM   #5
supershaft
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Use 1018 or 1020. Sometimes it is hard to find thin walled tubing in mild steel. 4130 usually has the best selection of sizes. It will work too.
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Old 04-08-2011, 11:32 AM   #6
zenben
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My 2c:
I'd go 4130. Better strength to weight. TIG, braze, or O/A.
If you must use a lesser welding process then go with the 1020 CRS. If you plan to add bends then I'd choose DOM.

On the whole, I think you would be shocked by how much lighter and stronger the 4130 is. Worth the cost difference IMO.
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Old 04-08-2011, 11:49 AM   #7
supershaft
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1020 is sometimes hard to find. 1018 is much more plentiful and specs out nearly the same as 1020. I use to like 1020 because it cuts easier. The aircraft I use to work on you could use 1018 or 1020 interchangeably. 1025 called for different applications but . . . .

The problem with 4130 is that most people don't like working with tubing thin enough to really take advantage of its greater strength. It's trickier to weld and especially trickier to bend.
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Old 04-08-2011, 12:18 PM   #8
jtwind OP
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Weight isn't too critical as it's just a few short pieces. I've found some 1026 that I think will fill the bill. Lots to learn, wow!
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"Between two explanations, choose the clearest; between two forms,
the most elementary; between two expressions, the shortest."
Between two motorcycles the simplest (DW)
Eugeni d' Ors (1881-1954); Spanish writer.


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Old 04-08-2011, 07:41 PM   #9
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Quote:
Originally Posted by Airhead Wrangler View Post
I know that the R80G/S subframe (and the GS as well, I'm pretty sure) used 18mm OD mild steel tubing. The wall thickness on the GS subframe is 3mm (very beefy) whereas that of the R80G/S is much thinner, but I don't have a number.
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