Martins 650b day 2...

One aspect of custom frame fabrication that many people do not realize is just how long some processes take.  For example, I spent 11 hours today in the shop working on the headtube and cable routing insert.  The time was interspersed with updating the blog, email, etc.., but this gives a good perspective of the time commitment involved with manually machining your own parts.

I started with the headtube, a 44id Paragon Ti stock.  The plan is to create an internal cable plug that will take the cables/hoses through the headtube and allow passage around the steerer and into the top tube/down tube.  I have the design I need completed, now just to create the parts.

To do so, the head tube wall needs to be reduced a few thousandths, so in and out of the lathe it goes for boring.

 

The insert starts off as a solid piece of 1.00" 6/4 Ti.  I measure it all out and then draw the basic design to give me a visual to follow.

 

 

The sides are machined off to give the correct profile...

 

Once the profile and width are established, I then begin drilling through the cable pass holes.  6/4 Ti is extremely tough stuff, so it takes 5 steps to get to the final profile for each hole.

Skipping ahead a bit, I've profiled the top and bottom edges to allow an index point against the exterior wall of the head tube and then cut a curved profile into the inside aspect to match the ID of the headtube.

The finished piece ready for fitting to the head tube...5 hours

Here's the waste material off the bed of the mill from all the processes...

 

Next, I have to layout and then machine the relief hole around the headtube.  This is a one shot deal, too big and it's on to a new head tube.  I spent a good 30 minutes setting up and double checking my math and layout before cutting...

 

After machining, its a perfect fit...

 

A view from the inside of the tube...

All washed, degreased, and ready for welding...

And with a little time under the hood, she's all welded up and smoking hot...

Add in lunch and about 25 emails between Christi and I, and a full day has passed.  Would like to see more progress, but the little touches take time.

cheers,

rody

Martin's Ti belt drive 650b

Martin is looking on from afar, so I thought I'd shoot some step by step pics of day one of his fabrication.

This will be a Ti 650b belt drive single speed with custom EBB, post mount disc brakes, internal cable routing for geared use, and use a curved seat tube and top tube for funk.

The first hurdle of this build is insuring that with a curved seat tube, that the end saddle position remains the same as it would with a straight post.  It takes a bit of math and some datum point fixturing to insure that the intended overall cockpit length stays the same with the curved seat tube, as the design angles the post further back. 

The math done, I need to move the post forward .66 inches or about a total of 1.25 degrees to retain my saddle position.  To double check my math, I set up the fixture with the desired measurements using a standard post, attach a quick extension bar, and mark the saddle center point on it. Then the fixture is reset to the adjusted angle and checked to insure the intersect point at the correct saddle height stays the same.  (sorry for the rotated pic, can't figure out how to turn this one and make it stay).  Here's a quick pic holding the straight post up to show the forward offset to compensate...

With the fixture position set, I began making the seat tube by turning down the top mast insert, creating a shoulder to press in and then boring out the ID to allow for welding shrinkage...

The top insert done, it's time to cut the seat tube to accommodate, face the top edge, then press the insert into place and weld it in.

 

The weld is sanded smooth so that no indication exists of the coupling, then I begin setting up the binder.  The tube is fixtured and the top cut at a 12 degree angle, then the center is found and marked for the binder placement...

 

 

The binder is machined to fit the seat tube OD...

 

 

And then everything is cleaned and the binder welded in place, carefully leaving the soon to be slot open so as not to dull my tools by cutting through the weld...

 

Once she's all welded up, the binder slot is drilled and slotted with a slitting saw...

 

With the seat tube mostly done, I prepped the custom EBB, the stock is cut on the cold saw...

 

Then turned and faced to get our desired width dimension...

 

The ID is then bored to fit our custom insert...

The insert is a custom aluminum piece that allows for over 1/2" of throw and can easily be adjusted on the trail using your crank arm and an allen wrench, simply loosen the pinch bolts, put the allen wrench in the recessed hole on the EBB face, then use your crank arm to push against the wrench and rotate the insert to loosen and tighten...

 I then turn down the OD to take some weight off then clean it up, fixture the pinch binders in place, and weld it up...

The EBB shell is then cut on the cold saw and the edges filed smooth...

Once the EBB is on the frame fixture, I can then miter the bb end of my seat tube...

With the seat tube all nicely fitted up, it's on to the down tube.  I cut in the bb end first, then fit the head tube end...

The next cut is the st/dt junction...one of the most difficult on this build as the curved seat tube enters at an acute angle and falls away, so the cut must be precise the first time, as there is no filing this one in if you miss.  I begin by setting the down tube adjacent to the seat tube and using a square, transfer across the front edge of the seat tube...

I then mark around the seat tube, remove it, and place the down tube.  I use calipers and basically connect the dots to see where my miter margins should be.

The head is tilted and the miter fixture is tilted to match the entry angle for the curve...

One shot to get it right, so I double check everything and then make a cut.  You just see the remnants of my lines...

Spot on, whew!  I'll have to be very careful with my heat control coming through the crotch as the angle provides a tapering wall, getting thinner as it approaches the seat tube.  Will probably use a bit larger diameter filler there to fight the edge's desire to pull away.

The front triangle coming together...

 

cheers,

 

rody

Reggies LD stem

A blow by blow visual depiction of the process...


I started off by machining the back plate to accept a 1.25" x .058" aircraft chromoly tube...

The stem has bee designed to match his current set up and marked appropriately for the center line and heights...now just to start cutting and facing...

The stem is rough cut to the required dimensions and then faced on the mill to insure it is straight and perpendicular to the center axis.

A quick peek to insure that the back plate machining and counter sunk relief match the tubing profile and wall thickness.

The binder is then cut on the mill to the OD of the stem tubing...

With everything machined and set, I insure the stem is upright and square to the table, then tack the faceplate on.  With a 6' tube installed, I then use the height gauge to gently align the orientation to insure the bar will be perfectly positioned in the stem.

 Once the position is set, everything is welded up and secured...

Next up, I drill and cut the slot for the binder relief, allowing the stem to tighten on the steerer tube.

Checking the new stem to see how it matches up with the original...although a different shape, all the important datum points match up.

 A little time in the paint booth and bake box and we have a graphite black ceramic coated beauty...

cheers,

rody