Monday, January 10, 2011

Yao MIng Part 2 - Steve Chimes In

My good friend, studly Crested Butte local, and fellow frame builder Steve (who also builds a lot of wheels for me) inexplicably bothers to read the blog and was excited about the Yao Ming post - so he decided to do a *proper* design for the big fella.

First, here's the print:

And here's what Steve has to say about it:
I was reading your blog the other day and saw the Yao Ming post and you were so right! That bike was down right dangerous and Gunnar was smiling about it. I know there arent that many people in the world taller than 6'10" but clearly none of them are riding bikes. Talk about a frame building niche. So when I saw your post I just wondered to myself...could Yao Ming at 7 feet+ tall make a 36er wheel look small?

Combining this curiosity with my frame building partner telling me how good Rattle Cad is (another free bike design program), I decided to kill two birds with one stone so to speak. It turns out that Rattle Cad really has come a long way since it was released as open source code. When it was first released it made nice pictures but was useless for frame building. There are still a few things BG101 does that I find useful that Rattle Cad doesnt but it is just a matter of time (toe overlap plot, drivetrain plot, general printing is terrible, and lack of BB junction (three tubes intersecting) miter template.

As far as the design of the Yao Ming 36er goes, I didnt get too deep. I located the three contact points in space like I said in the first email. I gave him 225mm cranks (arbitrary number) and compensated the BB height for equivalent pedal/rock clearance as my hardtail. I messed around with the head tube angle and fork offset to get (maybe?) toe clearance for a size 25? shoe (about 200mm). I also shot for a trail number between 70-80mm because I thought that is what other 36er builders did. I included a suspension corrected fork (100mm) because, hey, you never know.

The tubing selection and chainstay length were just picked by eye. I tried a 2.5 inch down tube as you suggested but it just looked too fat (aluminum). So I matched it to the oversized headtube at 44mm. In the end I think Yao would approve. He is right at the cusp of making a 36er look too small, which is saying something, but I bet it would be the best riding adult bike he has ever owned.

See? Not very scientific but there it is.

Edit: here's a version with water bottles (the big kind) for perspective. From Steve:

Im sending another version of the bike with water bottles this time to give some perspective on how big this bike is...they look like Barbie water bottles. Also, I contradicted myself, the down tube is 2". And Rattle Cad only displays 175mm cranks in this type of view. So those arent really shown correctly but the overlap I mentioned is right.

Edit 2: For those who are interested, RattleCAD can be downloaded for free here. It will run on basically any Windows machine or Mac running Parallels/virtual Windows.


Anonymous said...

That looks shockingly normal.

I imagine this would require custom chainstays and possibly other unique tubing, but it would be great for someone to build a 36er for a 7'+ individual.


StanleyJ said...

Yeah, I had a little play in the free BikeCAD applet and came to the same shocking conclusion... a 36er for someone of Yao's height looks shockingly normal... even with the oversized tubes it looks like an oldschool skinny steel framed MTB.

However, where can I get this mysterious Rattle CAD? It's not a very Google friendly name, though I did find the BG101 spreadsheet... heh.

Walt said...

Stanley -

Added a link for you, but here it is again:

Anonymous said...

RattleCAD runs on Mac OS X without Windows/Parallels/virtualPC since it is tlc based program.

To use it simply download it to your desktop, unzip it, open terminal application and type sh ~/Desktop/rattleCAD_3.2.32/3.2.32/rattleCAD.tcl

Walt said...

Anon -

Are you sure that's the right path? It does not work for me...


Walt said...

Whoops, figured it out. The link I posted is to an old version, so the path is incorrect.

StanleyJ said...

Ah, thanks Walt! Actually, the official project page is here:

... didn't think to look on SourceForge as a search on bicycle related CAD stuff whilst a little while ago yielded nothing... now I know better! ;)