Kenny--Trials Posted May 27, 2015 Report Share Posted May 27, 2015 (edited) Right so, i haven had a trials bike in a while now (about 2 years) and since i have started a job doing aluminum/steel fabrication so naturally i want to build my own frame Im currently trying to draw up the frame design on solidworks 3d cad so i can make a jig from that and then get to putting it all together but just the cad drawings are proving impossible because i dont have anything to measure off. The tartybikes videos do help explain where the dimensions are from/to but im having trouble with things like: - the internal size of the head tube - bottom bracket cup length, thread size and internal diameter (without thread depth) - typical tube diameters for top tube, bottom tube, chainstays, ect everything else i could probably do, any help/advise would be greatly appreceated thanks edit: if anyone knows how the offset on forks work that would be handy too Edited May 27, 2015 by Kenny--Trials Quote Link to comment Share on other sites More sharing options...
isitafox Posted May 27, 2015 Report Share Posted May 27, 2015 Try having a play about on bikecad, that'll help your understanding of the geo dimensions a bit Quote Link to comment Share on other sites More sharing options...
Kenny--Trials Posted May 27, 2015 Author Report Share Posted May 27, 2015 Try having a play about on bikecad, that'll help your understanding of the geo dimensions a bit Thats a really good site but ive actually already decided on the geo, i just need the few lat bits of information so i can piece it all together and use it as and engineering drawing Quote Link to comment Share on other sites More sharing options...
isitafox Posted May 27, 2015 Report Share Posted May 27, 2015 edit: if anyone knows how the offset on forks work that would be handy too I meant more for this Quote Link to comment Share on other sites More sharing options...
Kenny--Trials Posted May 27, 2015 Author Report Share Posted May 27, 2015 I meant more for this Ahh, all i meant by that is: is the offset perpendicular to the axel to crown length or does it run parallel with the wheel base but im pretty sure its perpendicular Quote Link to comment Share on other sites More sharing options...
aener Posted May 27, 2015 Report Share Posted May 27, 2015 It's kind of neither, but I think you probably just used the "wrong" words for what you intended to mean with the first one. If you ran a line down the centre of the steerer tube and extended it all the way down past the dropouts, the offset is measured perpendicularly to that. The axle-crown length line would be the line that a straight-bladed fork leg very nearly follows. Standard headtube ID is 34mm, I think, and Euro BB ID is 33.5, again, I think. Tube diameter varies wildly from frame to frame, though for a rough guide: ~45mm downtube for a "regular"ish look, or ~50mm for one of those "wide" or ovalized looking ones, ~35mm toptube and 22mm for the back-end would probably not be far off. Quote Link to comment Share on other sites More sharing options...
Kenny--Trials Posted May 27, 2015 Author Report Share Posted May 27, 2015 Cheers man. The bottom bracket is the main thing thats confusing me because i will have to put threads in myself so i need to allow for the thread depth when im tapping it but does that 33.5 include the thread depth? I read somewhere that its 24tpi but im not too sure how that relates to the depth if at all. I think im going to try and use a 1"1/2 (39mm) tube for the downtube because otherwise it will be a pain to fit and get a nice weld on it Quote Link to comment Share on other sites More sharing options...
isitafox Posted May 27, 2015 Report Share Posted May 27, 2015 Try and get hold of a spanish BB with press in bearings? Quote Link to comment Share on other sites More sharing options...
Kenny--Trials Posted May 27, 2015 Author Report Share Posted May 27, 2015 Try and get hold of a spanish BB with press in bearings? I had thought of that but the inside diameter would have to be dead perfect so it wouldnt wobble around or wouldnt fit at all. might be easier though 1 Quote Link to comment Share on other sites More sharing options...
isitafox Posted May 27, 2015 Report Share Posted May 27, 2015 Thinking about it, wouldn't you just buy a standard headtube and BB? That way the BB will be pre tapped?? Quote Link to comment Share on other sites More sharing options...
bing Posted May 27, 2015 Report Share Posted May 27, 2015 (edited) Bb threads are 1.37"x24tpi. Don't forget the drive side is left hand thread. But as Dave says, Spanish would be better. If you get the dimensions any decent tool shop could knock you one up, it's just a stepped tube effectively Edited May 27, 2015 by bing 1 Quote Link to comment Share on other sites More sharing options...
Kenny--Trials Posted May 27, 2015 Author Report Share Posted May 27, 2015 i didnt even know they sold them separately? But the first concern that comes into my head is then how it would weld up as the welds would be stronger if they were made from the exact same material Bb threads are 1.37"x24tpi. Don't forget the drive side is left hand thread. But as Dave says, Spanish would be better. If you get the dimensions any decent tool shop could knock you one up, it's just a stepped tube effectively oh i could probably make it up at work but i have no idea how they fit in haha Quote Link to comment Share on other sites More sharing options...
isitafox Posted May 27, 2015 Report Share Posted May 27, 2015 http://www.paragonmachineworks.com/ http://www.2soulscyclesen.blogspot.co.uk/ http://www.ceeway.com/ http://www.henryjames.com/ http://www.bikelugs.com/ Quote Link to comment Share on other sites More sharing options...
sstein Posted June 2, 2015 Report Share Posted June 2, 2015 Here is a suggestion. Go to any bike shop (including Hellfrauds), ask for one the scrapped frames (there will usually be a couple sitting in the metal bins). cut the head tube and bb off. Weld into your new frame. 1 Quote Link to comment Share on other sites More sharing options...
Ash-Kennard Posted June 2, 2015 Report Share Posted June 2, 2015 Thinking about it, wouldn't you just buy a standard headtube and BB? That way the BB will be pre tapped?? Just make sure it is welded the correct way round or you will be undoing the bb with every pedal stroke Quote Link to comment Share on other sites More sharing options...
Kenny--Trials Posted June 3, 2015 Author Report Share Posted June 3, 2015 it is rh thread on rh side right? Quote Link to comment Share on other sites More sharing options...
Ash-Kennard Posted June 4, 2015 Report Share Posted June 4, 2015 Normal threads on RHS Quote Link to comment Share on other sites More sharing options...
Ali C Posted June 4, 2015 Report Share Posted June 4, 2015 normal thread is the left side Quote Link to comment Share on other sites More sharing options...
Ash-Kennard Posted June 4, 2015 Report Share Posted June 4, 2015 normal thread is the left side Wouldn't that loosen when you pedalled? You're probably right, meh Quote Link to comment Share on other sites More sharing options...
Mark W Posted June 4, 2015 Report Share Posted June 4, 2015 Ali is right on that front. All about precession I think? Quote Link to comment Share on other sites More sharing options...
Kenny--Trials Posted June 5, 2015 Author Report Share Posted June 5, 2015 i thought it was normal thread on the right so that with each pedal stroke it couldnt come undone both sides? Quote Link to comment Share on other sites More sharing options...
aener Posted June 5, 2015 Report Share Posted June 5, 2015 Ali and Mark are right: non-drive side is standard, drive-side is reverse. Quote Link to comment Share on other sites More sharing options...
Kenny--Trials Posted June 5, 2015 Author Report Share Posted June 5, 2015 (edited) either way im still trying to find someone to tap the threads for me. ive messaged a few companies but they all said that they either dont have the taps or wont do it because they only use them for chasing the threads Edited June 5, 2015 by Kenny--Trials Quote Link to comment Share on other sites More sharing options...
Mark W Posted June 5, 2015 Report Share Posted June 5, 2015 It was bearing precession I was thinking of... I don't know what stage you're at, but you could maybe just try buying some pre-built BB shells? Companies do sell ready-made parts like that which might help you out if you're struggling. Quote Link to comment Share on other sites More sharing options...
Alex Dark Posted June 5, 2015 Report Share Posted June 5, 2015 Would be pretty difficult to tap a thread that large nice and square , as above get hold of a bb she'll or ask a machinist to screw cut one for you Quote Link to comment Share on other sites More sharing options...
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