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Building a Titanium DJ frame. Help!

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Building a Titanium DJ frame. Help!
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flag dirtjumpdan
Posted: Sep 9, 2009 at 11:32 Quote
Hey. So my mate has been granted by our college the money to make a Titanium bike frame. He gets to design its geometry, and cut the tubes into shapes, then a nice man is going to be paid to weld it all up for him. Pretty sweet huh? Cool

Anyway, my mate used to have a 1995 DMR Trailstar, which he loved the geometry of, and he wants to base the frame around that, just with a lower standover height/shorter rear end.

I told him to base it around a Dobermann Pinscher.

So we kinda said a mixture would be good, but what would any other people have to say on this? We know our suff about bikes, but neither of us are the most knowledgeable with frame geo etc.

Basically, could anyone find the exact geo from a 1995 Trailstar, and would people be willing to give us an idea of ways to tweak the geo, eg. head angles, chainstays etc.

Cheers, Dan.
flag Giant-Rider-Sam
Posted: Sep 9, 2009 at 13:39 Quote
As its going to be a Ti frame...Id pressume its use will be 4x/dj? and not street?
Remember, Ti flex's...and it can be a slightly noticeable flex, therefore...i wouldnt use a Ti frame for street.

Secondly, a 1995 Trailstar runs on outdated geometry...Personaly, id replicat something like an NS sub etc...

To check out your geometry...Check out Bikeforest - BikeCAD...good CAD programme for checking HT geometry...

HTH
Sam
flag Edoubleb1
Posted: Sep 9, 2009 at 13:48 Quote
Thanks for that, I am not using the trailstar frame at the moment i have a newer dmr sidekick, but they feel simerler so i am only going to use it as a rough guide, Originaly i wanted to make it out of 4130, but my tutor said that he wouldnt pay for the materials if i made it out of anything other than ti, for some reason. So i thort i would give it a go if its free. I am also going to use slightly thicker walled tubeing to try and stiffen up a bit of the flex.
flag dirtjumpdan
Posted: Sep 9, 2009 at 13:55 Quote
Yea cheers for the input man. It will be mainly used for DJ.

And yeah, outdated somewhat, but Ethan rode it for like 3 years, and says he liked it. LOL.

I just have to download a newer version of java and il have a fiddle on bike CAD, it just makes my PC so fecking slow Razz
flag Metalzanna
Posted: Sep 9, 2009 at 16:55 Quote
The Atomlab TrailKing? it's like a 26" bmx
flag azonicstellhead
Posted: Sep 10, 2009 at 0:50 Quote
Commencal are releasing Dan athertons custom Ti hardtail for 4x & a DJ model for 2010, theres some info about the different way they had to be built. i thought this would help you a lot because obv like the guy bove said it does flex quite.
as for the geo ring DMR they're nice guys, i'm sure they'll tell you.
i know this is obv but put a fudge load of research into the geo because if you make it right once for free then you'll probably have a frame for life.
Look at the blkmrkt frames for clean lines etc (brake boss') that should help keep weight down

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flag yo13bo
Posted: Sep 10, 2009 at 3:30 Quote
for dj try to make the bottom bracket a bit lower for stability, just dont go too low. i think a 10-20mm drop would be nice. head angle would need to be slacker than a street bike, definitely under 70 degrees. for me 69.5 feels really good but i think a 28 would still feel nice. chainstays probably shouldnt be slammed because it makes the bike less stable, but it makes the bike alot more flickable, so try a 390 or 400mm chainstay if you like your bike to be stable, go 380 if you want spins to be effortless. my advice would be try riding alot of test bikes and look up the geometry too see what you like and dont like, id say try an ns, dobermann, specialized or the likes just to see what the bikes you like have in common eg. slack/steep head angles, chainstay length etc. even though this makes the first bit of my post rather useless id say dont liten to anyone about what specific specs you should use, but just make something that you would enjoy riding
flag timbostp
Posted: Sep 13, 2009 at 8:57 Quote
hi, like the idea. Just a thought but why not consider building it out of carbon. This would be excellent for street/dirt jump applications due to the stiffness and superb crash resistance of the material. Have fun.
flag Edoubleb1
Posted: Sep 13, 2009 at 9:13 Quote
timbostp wrote:
hi, like the idea. Just a thought but why not consider building it out of carbon. This would be excellent for street/dirt jump applications due to the stiffness and superb crash resistance of the material. Have fun.
Hi timbostp by the sounds of it you are a mechanical retard Facepalm
flag timbostp
Posted: Sep 13, 2009 at 11:11 Quote
Allright Barney you engineering fail. I know, let's take some titanium, a material renowned for its light weight and trail enhancing flex, and make it stiff and heavy. Hmmmmmmmm......even to a mechanical retard, the idea of taking a high end, expensive material and producing something displaying many characteristics of a much cheaper and more readily available material such as iron does seem somewhat preposterous. Maybe i'm missing something but this seems to be one of the most stupid and pointless projects that man has ever undertaken and is, in my opinion, a crime against the cycling world.
flag mikedjumpin
Posted: Sep 13, 2009 at 11:16 Quote
Giant-Rider-Sam wrote:
As its going to be a Ti frame...Id pressume its use will be 4x/dj? and not street?
Remember, Ti flex's...and it can be a slightly noticeable flex, therefore...i wouldnt use a Ti frame for street.

Secondly, a 1995 Trailstar runs on outdated geometry...Personaly, id replicat something like an NS sub etc...

To check out your geometry...Check out Bikeforest - BikeCAD...good CAD programme for checking HT geometry...

HTH
Sam

ti is flexible however, with the metal being so light you able to use tubes with bigger diameter which makes it alot stiffer. also my friends ti frame had dropouts that were twice as stiff as a grim reaper(not the greatest frame to compare to but thats all we had). basicaly ti doesnt exactly break on big impacts, more less if the metal gets a tiny fracture your whole frame will go at once
flag dh-pete
Posted: Sep 13, 2009 at 11:19 Quote
timbostp wrote:
superb crash resistance of the material.
Facepalm
flag Th3Fr33r1d3r
O+
Posted: Sep 13, 2009 at 11:37 Quote
timbostp wrote:
Allright Barney you engineering fail. I know, let's take some titanium, a material renowned for its light weight and trail enhancing flex, and make it stiff and heavy. Hmmmmmmmm......even to a mechanical retard, the idea of taking a high end, expensive material and producing something displaying many characteristics of a much cheaper and more readily available material such as iron does seem somewhat preposterous. Maybe i'm missing something but this seems to be one of the most stupid and pointless projects that man has ever undertaken and is, in my opinion, a crime against the cycling world.

Yes, making a sweet ass custom Ti frame for free sure is a crime against the cycling world...

MASSIVE FAIL Facepalm
flag markbatt
Posted: Sep 13, 2009 at 11:44 Quote
timbostp wrote:
Allright Barney you engineering fail. I know, let's take some titanium, a material renowned for its light weight and trail enhancing flex, and make it stiff and heavy. Hmmmmmmmm......even to a mechanical retard, the idea of taking a high end, expensive material and producing something displaying many characteristics of a much cheaper and more readily available material such as iron does seem somewhat preposterous. Maybe i'm missing something but this seems to be one of the most stupid and pointless projects that man has ever undertaken and is, in my opinion, a crime against the cycling world.

Carbon is incredibly hard to work with when building structures like frames, it is often much more expensive, and it is not ideal for a frame that will undergo direct impacts. That is because carbon does not show damage after an impact even if it is severely structurally damaged. This is the reason why if you crash a carbon fiber frame, you often have to send it back to the company for analysis.

As for the Ti frame, sounds like a good idea. If you build it right it can be just as stiff as a 4130 frame, so do your homework. As for geo, if it is a strictly dirt frame, look into blk mrkt geometry.
flag timbostp
Posted: Sep 13, 2009 at 11:50 Quote
Epic international humour gland FAIL
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