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PostPosted: Fri Aug 12, 2011 8:07 pm 
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I have a project in mind about building a dh frame.
My question is about the steel i should use.
Would stainless be the better option or 4130 cromo?
Also what would be the correct thickness and diameter of material?
What size tube would i need for the head tube 1.1/8" and what size would i need it machining out too?
Also can the headtube , bottom bracket shell and lugs for the 12mm rear axle be bought.

Thanks for the advice

Jay


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PostPosted: Fri Aug 12, 2011 9:13 pm 
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Joined: Sun Jun 27, 2010 9:37 am
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www.ceeway.com for frame bits

4130 is lighter and stronger than stainless, easy to work with too.

head tube wise not meaning to patronise but any tube with an id of 1"1/8th would do.

hardest bit would be building the jig. its taking me eons to build the jig for the hardtail frame i've designed, admittedly only doing 1 day every fortnight at the workshop....


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PostPosted: Fri Aug 12, 2011 9:28 pm 
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Ooooh jama your building a jig 8)

To add, why not go to a 1.5 headtube? Best of both worlds then (and possibly easier to source? im not sure)


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PostPosted: Fri Aug 12, 2011 9:53 pm 
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Thanks for the info peeps.
Also jamabikes yeah no worries , i just thought it would need to be a fraction smaller than the 1.1/8" to fit a headset , hmmm! 1.5 may be better.
Hopefully the welding course i'm going on will help me loads.
Also may get and old steel frame to play around with.

Thanks for the info and the site.

Jay


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PostPosted: Fri Aug 12, 2011 10:47 pm 
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Yeah try on a few old ones if you can
maybe source one for the dropouts and stuff and practise on the rest

Many welders and engineers on here :wink:


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PostPosted: Sat Aug 13, 2011 9:03 am 
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cyfa2809 wrote:
Ooooh jama your building a jig 8)

To add, why not go to a 1.5 headtube? Best of both worlds then (and possibly easier to source? im not sure)


yep building an adjustable jig, means i can make changes as i test the frames. also means i can knock out a few frames to give to mates to test.

a 1.5 head tube is a good idea as it totally future proofs the frame too.

practising on old frames is ok but wont give a true idea on how things go together, but cutting up old frames is good practice, as you see what kind of joins and mitres are used. welding wise, a tube isn't too pricey so practising on a new one is the best way imho


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PostPosted: Mon Aug 15, 2011 7:17 am 
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ramstein-dh wrote:
Hopefully the welding course i'm going on will help me loads.

Jay


A TIG welding course, presumably?


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PostPosted: Mon Aug 15, 2011 9:47 am 
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Quote:
but any tube with an id of 1"1/8th would do.


Um. 1-1/8th is the OD of the steerer tube, not the ID of the head tube. The OD of the headset cups for a 1-1/8th headset is 34mm.


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PostPosted: Mon Aug 15, 2011 9:54 am 
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MikeD wrote:
Quote:
but any tube with an id of 1"1/8th would do.


Um. 1-1/8th is the OD of the steerer tube, not the ID of the head tube. The OD of the headset cups for a 1-1/8th headset is 34mm.


Wouldnt that vary by manufacturer?


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PostPosted: Mon Aug 15, 2011 10:45 am 
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I cannot think of any bike frame made in stainless so there may be a clue as to why that is not a good choice. :?

from my limited knowlwdge, stainless is more brittle than mild steel hence maybe the reason why - you would presumably be using a tubing that is some fancy steel alloy since these are engineered for bike frame puposes - i..e have thin walls and correct properties, unless you want your bike to weigh a ton. .... but for downhill that is not so important (but remeber you still need to get it somehow to the top of the hill)

As mentioned, the time consuming part will be the jig so that the frame rides true and you'll probalby need to practise not only your weldig but maybe make a couple of frames on cheaper steel tubes first.

Makes sure you post photos of your progress :)


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