Hardtail 550t

[tone]

LOL Thanks for the bit of encouragement. I want to buy another gs soon and do it all again. As far as the tubing we used what they had at the chopper shop. I dont really know any of the specs on it. I would like to learn more though if you could send me a link or a book for reference.

Imo the best articles ever written on frame design are by tony foale & quick google session will bring up more info than you can deal with in a year lol, a lot of it is aimed at race frames but the same principles apply to any bike frame reguardless of type

For tube i would reccomend cds2 or the later equivelent cfs3 with a minimum wall thickness of 3mm unless you are an expreianced bronze welder then i'd go for chrome moly tube in the same size

Heres a link to another site i use that should provide hours of fun
http://www.britchopper.co.uk/forum/index.php you may have to register but these guys really know their stuff & have been doing this sort of thing even longer than me in some cases so the effort is worth it

hope it helps & if you need to bounce some idea's around i'm always around .... tone

[krsmetalhed1988]

I have recently attended an automotive school with classes in chassis fabrication. Most if not all shops here is the US us 1020 DOM tubing(Drawn Over Mandrell), meaning there is no welded seam on the inside of the tubing. .120 is the wall thickness. Cromoly is mostly used for racing and such. Expensive compared to 1020(mild steel). Dragbike chassis maybe, chopper chassis unnecessary.

Imo the best articles ever written on frame design are by tony foale & quick google session will bring up more info than you can deal with in a year lol, a lot of it is aimed at race frames but the same principles apply to any bike frame reguardless of type

For tube i would reccomend cds2 or the later equivelent cfs3 with a minimum wall thickness of 3mm unless you are an expreianced bronze welder then i'd go for chrome moly tube in the same size

Heres a link to another site i use that should provide hours of fun
http://www.britchopper.co.uk/forum/index.php you may have to register but these guys really know their stuff & have been doing this sort of thing even longer than me in some cases so the effort is worth it

hope it helps & if you need to bounce some idea's around i'm always around .... tone

[tone]

I have recently attended an automotive school with classes in chassis fabrication. Most if not all shops here is the US us 1020 DOM tubing(Drawn Over Mandrell), meaning there is no welded seam on the inside of the tubing. .120 is the wall thickness. Cromoly is mostly used for racing and such. Expensive compared to 1020(mild steel). Dragbike chassis maybe, chopper chassis unnecessary.

Cds = cold drawn SEAMLESS, cfs3 basically the same stuff with a name change to comply with euro standards, i would never reccomend any type of erw (electo ridge welded) or seamed tube for a frame

tone

[briyenkieth]

aren't our frames made from welded seam at the factory? Not that I'm disagreeing just curious. Minenlooked like seamed tube when I chopped it.

[krsmetalhed1988]

Yes the factory frames have a seam and are not .120 wall thickness. The smaller wall thickness is why they used more tubing and bracing for strength IMO.

aren't our frames made from welded seam at the factory? Not that I'm disagreeing just curious. Minenlooked like seamed tube when I chopped it.

[briyenkieth]

it's incredible how thin this stuff is. Even with suspension it seems like it's just to thin. Guess that's why I don't make the big bucks, not smart enuff to figure out things that complex.

[tone]

aren't our frames made from welded seam at the factory? Not that I'm disagreeing just curious. Minenlooked like seamed tube when I chopped it.

Hi, yes the stock frames are made from a good quality erw (seamed) tube & while this is ok on a stock frame with plenty of bracing & very short unsupported lengths with something like a hardtail where there can be up to 2' of unsupported tube its simply not strong enough, for example i can fairly easilly bend 2' of 1"dia erw with a wall thickness of 1.8mm round my knee (i'm not a big guy) all i'll get from trying to bend cds2 with a similar dia & wall thicknessis a hernia

Another problem with erw is the make up of the steel used its designed for chair legs & tables etc & while it will weld ok the heat & stress when in use can cause it to crack at the weakest point eg alongside your weld or on the original tubes weld, note the erw you can buy from your local steel stockholders in not of the same quality or composition as the original frame tubes

I'm not sure of how it works in the US but here in the UK a lot of our seamed tube comes in from spain & is of very poor quality & is best avoided for structural framework

I hope that explains my original post
cheers tone