Porter Bicycles – Made in New Mexico, USA

Picture 1: When doing a fillet joint (BB) I cut the ST miter and using a machinists square adjust plumb. I then install BB shell and center using vernier caliper (pic #2). Keeping the seat tube vertical I then braze to shell. You can use the movable distance gauge (Delrin spacer) to assure plumb.
I then rotate BB/ST to desired angle using the angle finder. Note: Seat tube offset can also be measured to determine the angle (thanks Omar). I then miter chain stays with dropouts already installed. Set your BB height and braze to BB shell.
Pic#4 shows the relative axle position if the wheel was installed. This for setting/marking the nominal bottom of the head tube.
(Click on pictures to enlarge)

In this set of photos, I’ve set the top tube height and top tube length as per design drawing. The miters are cut and the head tube angle is set. At this point I’m doing a cold fit to make sure that the miters are correct and nothing is binding. Last I’ll cut length and miters for the down tube. I’ll finally disassemble, flux everything up and reinstall in the jig for brazing. Presto-change-oh. I have a nice, straight, and fully brazed frame ready for any necessary cleanup of the welds.

(Click on picture to enlarge)

In these three above I’ve reinstalled it in the jig, fluxed up the joints and brazed up everything. Tomorrow the seat stays and dodads, a little clean up and it’s off to the paint booth. This is the first time for using Fred Parr’s Brazage Pro silver for lugs. It’s also the first frame since I lost an eye a year ago. I’m getting better at putting the rod at the right spot at the right time, but as you can see I did get a couple spots a bit hotter than I needed to. I’ll soak it over night and see how it looks in the morning.

(Click on picture to enlarge)

Well, after an overnight soak and a few minutes with a stiff wire brush the frame is ready for a little dressing around a couple spots on the lugs and a bit of radius clean up work on the fillet. I said last year about this time that I didn’t think I’d be able to build bikes with one eye.  I wouldn’t call it a miracle by any means but, the progress has been good. However, this little article was about the Morroni jig and  as you can see after a days work and little fuss  I have a fixie I can sell.

I spent a day on the fork, mostly fretting over what to use and dinking around with the blade length cutting fixture (scroll down) and another with the frame assembly and a third (today if I remain engaged) to do the seat stays and braze-ons.  I’ll put up a picture or two when its got the next day into it just to make the process complete.

dave

We’re having a great mid November weather weekend for riding so I haven’t been as diligent as hoped finishing up this frame. As promised here’s the finished basic frame, except a couple braze on bits still to add.  I haven’t decided if this will go out as a plain vanilla variety or if I’ll doll it up with some silver smithing adornments.  In the mean time..(Click on Pic to enlarge)

Here I’ve coal slag blasted the raw fillet to expose any gaps, pockets and wrinkles, then I shape and file to taste. This is like blocking done on body panels. The change in color helps to show high/low spots when a file is pulled across the dull surface.

Here is the last set of Zeus track drop outs in the world..maybe? Dave Bohm at Bohemian Cycles tells me he has near copies available. Thank God for artisans.

Here’s the head tube detail. I used an old Columbus groove tube. It may end up as a brake less fixie but I’m not going to mess around with liability issues by not making it brake compatible.

Here it is.

The crown is an 7mm offset Cyclo (?) for track blades. Old GPM brake bridge re-enforcements. MAX chain stays

and I don’t know what the seat and down tubes are.. Hey, it’s a mutt, but I love it so far.

Specs. are 54.5cm seat tube; 55cm top tube; 73.5 degree seat angle; 74 degree head angle; 5.6 cm drop; 95cm wheelbase; fork rake 32mm plus offset

DP

And here is the frame painted, decaled and awaiting it’s new home..

(Click on photo to enlarge-click again to zoom in

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Fork blade length gauge fixture (click on picture to enlarge)  This is one I’ve had kicking around forever. I never used it much because the 2 added barrels at the drop out ends won’t allow the fork blades to lay flat on the bed after they’ve been raked. So, I just used it as a gauge to insure that the dropouts were inserted exactly the same. I guess I’ll scrap that idea. I hate to take any fixture apart that is functional even if it is not used to it’s potential. Perhaps I’ll add some eyelets that allow the barrels to slide in and out of use. The next step is to add a cutting guide to assure a good straight hack saw cut or to mount the whole fixture to a chop saw such that it is adjustable for the forks intended use. For the math challenged, I’m told by Keith Anderson www.keithandersoncycles.com that he merely adds a centimeter to the unbent blade length, assembles the fork and bends both blades at the same time. Andy Newlands at Strawberry sent this catchy little “equation” for cutting blades prior to raking. Andy, by the way, bends both blades at the same time too. The straight blade length is equal to the “M” design distance from axle to race minus the fork crown dimension “H” (crown race to bottom of fork crown casting) plus the dimension (L-y) which is the difference in length between the chord length (bend) to the axle centerline and the straight length to the intersection of a perpendicular from the axle to the fork centerline.  L equals two times the bender radius times the radian quantity inverse sine of the square root of the product bender radius times fork offset divided by two all divided by the bender radius and y equals fork offset divided by the tangent of the same quantity inverse sine mentioned before. A table of L, y and fork offset can be developed for each bender radius and then you just determine the straight blade length from the design length M minus the fork crown dimension H plus the (L-y) value.  Once the tips are brazed, the blades are cut to length and brazed into the crown/steerer sub-assembly (pre-brazed) and then bent on my old Marchetti bender then aligned.  Works for me – may not work for you. However, once you get it down it’s pretty quick. Andy N. www.strawberrybicycle.com Thanks Andy!

Here are some links to Richard Sachs home made measurement device:

here1 http://www.flickr.com/photos/9866331@N08/750318950/in/set-72157600706479896/ here2http://www.flickr.com/photos/9866331@N08/750319044/in/set-72157600706479896/ here3http://www.flickr.com/photos/9866331@N08/749461097/in/set-72157600706479896/ here4http://www.flickr.com/photos/9866331@N08/749461257/in/set-72157600706479896/ here5http://www.flickr.com/photos/9866331@N08/749461363/in/set-72157600706479896/

Richard quipped:  “i used a chopped and channeled 1970s fixture to get this done. not fancy, but dedicated, accurate, and fast atmo.”  here6http://rscyclocross.blogspot.com

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