Either offset bushings or headset heatube.

i am very much interested in the calculation side of things in mathematical form or graph form.

for a project i am on with at the moment.

Sohcahtoa?

What is the question?

Sohcahtoa yes in that form would be a good start.

if i install some offset bushings how is the calculations worked out?

Draw a line along steerer, through hub.
Measure angle from vertical.
Or am I missing something?

Anyone interested in a works components +1 headset? Tapered HT type?

http://forums.mtbr.com/vintage-retro-classic/joe-breeze-otis-guy-head-angle-tests-5051.html

http://www.kreuzotter.de/english/elenk.htm

http://www.varg.unsw.edu.au/Assets/link%20pdfs/thesis_stevens.pdf

Bicycling Science goes into a lot of detail on the maths of head angles – the old edition especially.

Try this app:

Autodesk Force Effect

Take before and after photographs and measure the angle.

Doesn’t that assume your camera-holding skills are accurate? 😉

I just use an iPhone app to measure frame angles. Even made a special holder to use on tubes:

linkage

Not used it for what your after but may be of some use.

Ben, see what you are saying, but you trace over the photo in the app to form lines and intersections. The app then calcs the angles from your drawn lines.

I suppose you could set up a tripod and set the bike at a specific distance away for accuracy.

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

Bencooper, you were already quite high in my estimation even before I saw your Iphonespiritlevelthing, fab.

Doesn’t that assume your phone is correct? Mine often tells me im in Coventry, which is a couple of hundred miles away.

I did wonder about that, but tried calibrating it against various things, and also tested repeatability – accuracy seems to be less than 1 degree, repeatability about 0.2 degrees.

So perfectly good for my purposes, which is really double-checking frame angles.