Community

Forum menu
Geometry. Can I do ...
 

[Closed] Geometry. Can I do this without learning bikeCAD?

Posts: 7998
Full Member
Topic starter
 

Already got a bamboo road bike, but feeling the urge to build a bamboo MTB too. Looking at the 29er build kits, the head angle is 69.5 degrees, which seems a bit steep to me. The rest of the geometry is in the ballpark for what I want.

If I were to slacken the head angle out to around 65 degrees, is there an easy way of working out how much that would drop the BB by? And could I compensate for this by just dropping the headtube by the same amount? I know I need to check the axle-to-crown the frame is designed for, but if all things were equal...

I know I could grab one of the bike CAD apps and learn that, but it seems a bit of overkill for a one off build if there's a more straightforward way to do it.


 
Posted : 01/10/2018 10:25 pm
Posts: 6926
Free Member
 

RattleCAD is really easy to use and make simple adjustments.


 
Posted : 01/10/2018 10:44 pm
Posts: 7998
Full Member
Topic starter
 

Had a quick look at that, but couldn't get it to run under Linux. Will have another look when I'm next in Windows.


 
Posted : 01/10/2018 10:48 pm
Posts: 2548
Free Member
 

It is easy to do with a spreadsheet if you know some basic trigonometry.


 
Posted : 01/10/2018 10:53 pm
Posts: 7998
Full Member
Topic starter
 

I used to know some very basic trigonometry. Now I'm an Art teacher...


 
Posted : 02/10/2018 8:05 am
Posts: 17388
Full Member
 

An art teacher? Then what are you doing worrying about geometry, hie yourself off toย Atomic Zombieย and don't forget to let us see the results. ๐Ÿ™‚


 
Posted : 02/10/2018 8:43 am
Posts: 5387
Free Member
 

Are you going to use a bamboo bicycle club kit or do it your self?

The bbbc kits come with a a0 printout which you could manually adjust or you can, for extra cost get them to do a custom geo printout.

Link to my current build....

https://singletrackworld.com/forum/topic/new-bike-day-just-need-to-build-it-mk2/

Bikecad is pretty easy to use iirc - type in the geo you want and it does the work......


 
Posted : 02/10/2018 10:37 am
Posts: 2294
Full Member
 

Go to this site and download the Bike Comparator file.

It's an Excel spreadsheet that lets you adjust the geometry and gives you a visual representation of how one looks compared to another. It might work for what you're after.

http://gearinches.com/blog/misc/bike-geometry-comparator


 
Posted : 02/10/2018 11:10 am
Posts: 296
Free Member
 

You might findย  https://bikegeo.muha.cc/ ย is just what you're looking for...


 
Posted : 02/10/2018 1:42 pm
Posts: 7998
Full Member
Topic starter
 

RattleCAD seemed to do the trick once I got into Windows.

Before.

[img] [/img]

After.

[img] [/img]

Best start clearing some space in the garage... Where's best to get something printed out at A0?


 
Posted : 06/10/2018 6:57 pm
Posts: 1917
Full Member
 

Loads of print shops in towns or city centres. There's likely a Hobbs reprographics near you, they've bought most of the competition now...


 
Posted : 06/10/2018 11:57 pm