Chad's road frame taking flight

It seems like this road frame has been more difficult to get started than corraling a bunch of cats with a hyena by my side, regardless, it's finally moving.

I had talked with Chad about the final geometry; he is a fast club rider in Texas who typically turns out 30-50 mile rides on flat to rolling terrain at a nice clip.  Hindered by standard geometry that allows for appropriate standover but extends his cockpit longer than desired, we've designed a position that will accomodate his long legs and shorter torso, position him balanced between the axels to provide both comfort and performance.  The bike is on the sporty side of handling, but will still maintain the stability he needs when he's turning mile 80 of the Hotter then Hell 100 and his mind is fried from the waves of inhuman heat rising from the pavement :)

The bike will be a titanium road frame with a slightly sloping top tube, oversized down tube for controlling the torsional twist put out by his powerful size, and utilizing smaller diameter seat stays for a bit of vertical compliance and comfort.  With the end goal in mind, here's the numbers we'll be working with...

So, let's get started setting up the fixture, shall we?

Some folks have asked to see more detail on the fixture, so I thought I'd share a bit of the set up/adjustment process...

To begin, the bottom bracket is in a fixed position, so the axel position needs to be adjusted front and rear to accommodate for the necessary drop, or difference between axel and bottom bracket height.  The fixture is designed so that each adjustment has a dedicated measurement point utilizing calipers, there is never any opportunity for variance from the actual position due to a visual scale and indicator arrow like many designs.  Here I'm setting the rear axel position to our intended 68mm of bottom bracket drop.  The "T" allen wrench in the bottom of the picture is moving the tower using an internal lead screw, so you are not fighting gravity or friction when trying to dial in the position.

Once the front and rear axels are in the correct position, the axel to crown and offset are set.  Here I'm setting the axel to crown...there are three pin placements for the blue pin from which to utilize dependant on the length of the fork you want to design around.  In this case, I need an axel to crown of 14.44".  The first pin placement has a value of 12 inches, so I need to add 2.44 with the caliper adjustment to achieve my correct dimension...

Once the atc is locked down, the offset is then adjusted...

Then I simply drop the main beam until the pin on the back side of the offset plate touches the top of the "L" which represents the axel centerline and those are all set.

I can then adjust my seat and head tube angles, once again utilizing the calipers and the degree equivelency chart.  Setting the head tube angle to 73.25 degrees...

and the positioning for setting the seat tube angle...

With those set, the last adjustment is to dial in the effective top tube length using the lead screw in the rear of the fixture and I'm good to go :)

So let's start cutting some tubing...here's some head tube stock in it's raw form, measured and ready for the cold saw.

and making the cut...

Facing the ends in the lathe requires three steps; facing, deburring the internal edge, deburring the exterior edge...

Then the internal diameter is bored out to accommodate the correct press fit for the headset.  As I'm using a raw stock, I then turned down the center outside diameter, leaving the ends thicker to handle the stress, to relieve a bit of weight and give the headtube a nice look...

Checking for the correct wall thickness...

In the true sense...matter never is destroyed, it just changes form ;)

Moving on to the main triangle today.

rody