I am posting this here because:

1) You guys are very knowledgeable

2) You won't flame me and/or treat me with disrespect

So here is my question:

I have designed a cool new frame, but it requires that the top of the fork (where the fork post (???) leaves the bottom of the headset) to be as thin as possible. I will post a few pictures of my design when I finish it in Photoshop . Anyway, I am looking for something either as thin as or thinner than what is circled in yellow below:





No, that is not my bike.

I *think* what you've circled is what I'd call the "triple clamp", it's better known in motorcycle speak. I have no idea where you can buy one off the rack as they are usually machined by the fork mfgr. and I don't think they scrimp on material (making them very thin) very often as it's a critical-strength piece.

Ummm, mountain bike forum?

If I were looking for this, I'd scour my area for a good machinist and ask him what he thinks about the load that piece has to withstand and how substantial it must be. You can probably get it pretty thin if you spec forged stainless (and arch it a bit) but it'll be good and heavy.

Prepare yourselves...for the unveiling of my latest (only) design. I don't have a name for it just yet, but I think I should focus more on building it. So what do you guys think of it?

Trust me: you don't really want to know
Now that I see this, what you really want is a thin fork crown, and the thinnest will be something like an old Schwinn fork from a Varsity you can get cheap and cut it up and weld into whatever you like.

Awesome. Thanks for the help Unworthy. I will search for one of those Varsity forks and chop 'er up.

There was this chick on tv when I saw your design, her swimsuit looked the same shape as the void in your frame. Well, except her suit was red, not white.

Well, I finally decided to change the design a bit, so here it is. I shortened the wheelbase and added tires (I made them blue so you can see them). I can't wait to build it.

You'll get pedal overlap. Heck cranks will be able to touch the front tire. And the shape still reminds me of women's undergarments.. maybe its just me.

You gonna make it out of Fiberglass or what?

Only problem I can see is you'll have limited seat post adjustment.

I have a fork from a wrecked '72 Varsity (fork wasn't damaged) if you are serious about doing this, PM me.

really now, whats wrong with that?

Please leave me off the list of prospective test riders. Handling on this will not be enjoyable.

Any reasoning behind the design? Kinda just curious

kinda reminds me (At least the downtube) of a local framebuilder in my area (Shorty Fatz) who recently created...

Wow. I have never seen a design like that before. My design was inspired by the Fuji Track Pro. That really is strange how similar the designs look, eh?

Aaah.. I think I have worked out most of the issues here.

I was trying to figure out what was wrong with the original design. It has an exceedingly long top tube. I think the Shorty fatz bike missed out by not putting a curved seat tube on it. It would then have a very short chainstay length. I recently saw a bike that had the curve going forward, which I though was a little silly.

Umm...yah. I think you just made my design look like a Fuji design. I have decided to space out the bottom of the frame a little so that the cranks don't overlap the front wheel .

From an aspiring framebuilder to a person who just wants to design something innovative, I have to ask, have you ever studied frame geometry? I ask because your angles are just all kinds of wrong. You can't have a well handling bike with a 90° headtube and VERY little fork rake. The steering will be sharp as a fine knife and lead to poor cornering ability. Rake is the difference (in parallel lines) from the center of the headtube to the center of the fork dropouts. It, and your headtube angle create fork trail, which is the difference between the contact point of the tire and a theoretical straight line from the center of the headtube to the "point" where it theoretically contacts the ground. Trail IS how your bike handles, low trail usually leads to more stable, predictable handling. While higher trail is usually quicker. Why? Low trail puts the wheel further from the frame, extending the wheelbase and spreading the load. High trail does the opposite. For a track bike you usually want high trail.
-Gene-

Also, your seatube angle looks appropriate, though your Bottom Bracket drop is extreme. For a track bike, you want a high BB and little (1-2in.) drop (though I've seen bikes with even less).
You've definitely got the idea, though it seems derivative of a Cervelo P2T and P3T in overall frame design.
Read up on frame design before you go building a jig for this. You don't to get hurt getting thrown off of an unrideable bicycle.
-Gene-

Also, track dropouts...

I was aiming to make this a track bike. I did not know about the geometry and fork rake before your post. Thank you for taking the time and effort in posting that. I appreciate it. Since you are a frame builder, what would you do to make this bike more user friendly while keeping the curved tubes as close to the tires as possible?

P.S. What is the correct tubing I should get for this build? I was going to try to make it out of aluminum. Thank you.

Aluminum really would work best for your design, though having it hydroformed to your specs would be expensive. You could look up how to build your own carbon fibre frame and while it is labor-intensive to do so, you could get a frame more built to your specs and design.
I'm not a framebuilder, sadly. Just an aspring one. I know ALOT but have no practical experience.
As far as tips, don't have a wheel cutout for the front. There's simply no real aerodynamic benefit to it. The shorter the chainstays, the better ( though they can only get so short before you have clearance issues with the bottom bracket and also maintain a high, low drop, BB).
And keep your seat tube angle pretty upright 77-79° I do believe is an appropriate angle for Track /TT bikes. Also with such an upright seat tube and high saddle/bar drop, a shorter top tube is necessary to maintain a proper stretch for the rider, maybe a cm or two shorter than usual (maybe more, maybe less.)
Hope all this helps.
-Gene-

Now you may laugh and flame me for this, but what do you mean by hydroformed? If you are talking about the curved tubes, I was going to see if one of my local metal working shops could bend it for me. One of my uncles offered to weld it up nicely for me, so I have that part covered

aluminum does have special requirements for welding that steel does not. If you are planning to use aluminum check with your Uncle and see if he is equipped for that.

I have already done so. Thank you for warning me though. My uncle actually welds stuff for a living, so he has all the right equipment. I wonder if he has a tube bender...

How expensive is it to make my own carbon fiber frame?