cutting the main triangle tubing

with the finished drawing, the frame tubes can be mitered to the proper lengths.

much like wood, metal tubing has its imperfections, so before the tubes are cut, i  roll each tube on my granite surface plate to find any bowing in the tub. i mark the high point in the tube and i make a scribe line down the entire length of the tube using a piece of 1/4"  aluminum angle stock as a guide and a sharpened tungsten electrode to make the scribe line. this gives a nice reference point for cutting the tube and for braze ons and bottle mounts. I do this to all of the front triangle tubes. When the frame is all brazed together, the bows in each tube will be aligned along the vertical axis of the frame.

One final thing before cutting the tubes is finding the depth of the tubes butting. some tubing manufacturers provide the butt length data for each tubeset, but others do not. i use a combination of sight and the depth gage of my vernier caliper to figure out the butting length. fancier measuring tools are out there, but not worth the expense in my opinion. you can generally see the line of where the butting begins when you look inside the tubing. i mark the measurement with a sharpie

now we can cut the tubes
a few methods for cutting miters in tubing

1. there is a program on the internet called Tubemiter, you enter the tube diameter, the angle of the cut and the size of the tube it will be jointed to. then the program give you a flat representation of the cut that you then print out and tape around the tube. then you can mark the cut and use a hack saw and files to make the miter.(ive never used this method by the way)

2. use the lugs as your template for your miter.  insert the tub into the lug to the point where you want to make the cut and use your scribing tool to mark the shape of the cut. once you do this, you make the cut the same way you did the cut on with method 1.

3.  cutting the miter by hand. this method needs a little more experience, but once you have done a number of miters by hand, you get the hang of it. pretty much, you make a rough cut with a hack saw, then finish it using files and an angle gage.

4. using a mechanical cutting tool like hole saws on a milling machine or abrasive disc tools. pretty much, this is the most expensive method, but it can also be the quickest and most repeatable. i really recommend cutting your miters by hand to understand the technique. the downside of using machines to miter is that its real easy to mess up a tube by cutting it off center or too short, with hand mitering, it can be much more forgiving. if you miter is a little off and you are taking your time to not file it too short right away, you usually have enough tubing to fix the issue.

with each of these methods, you goal is to get a perfect miter. first check that the angle of your cut is right by using a steel protractor. then use a machinists square to make sure the high points of the cut are square to one another, then use the tube that the mitered tube is to be jointed to, to see if light gaps can be seen when you stick them together, if there are light gaps, use a half round file to finish the cut.

i usually start with the seat tube because only one end of the tube needs to be mitered, so its the easiest tube to deal with. also the main cut is a 90 degree angle. i then make a compound miter for the downtube.

then i make the headtube/downtube junction miter followed by the downtube bottom bracket miter and finally the top tube miters(these are the hardest to get in line with one another, so take your time to get them straight)

Arnold's track frame day 1

finalized the geometry for Arnold's track frame. He wants a frame with steep head and seat tube angles(both 74 degrees), short rake(30mm), but a standard road bottom bracket drop(70mm). He currently rides a Surly steamroller, so the frame is designed to have the same fit.

here is a quick tutorial on how i  draw a frame to full scale, im sure other builders do it differently. some builders have access to a printer which can print a full size image, which would be nice.

things you will need:
-a large piece of paper (i use news print that is free from the local newspaper, it is large enough to draw any frame, although its quite thin)
-a meter(yard) stick with metric
-pencil(i use mechanical pencils to get a finer line)
-a protractor(a machinist protractor works best, but the cheap ones from math class work)
- a vernier caliper with metric( dial and digital work too, but i prefer vernier)

step one

Near the bottom of the page make a long straight line that is at least as long as the wheelbase of  the frame from the rear dropouts to the front dropouts) this is your wheel axle centerline. 
then measure and mark the bottom bracket drop below this line in at least 3 places.  connect the dots and this will give you a parallel line with your axle line. this represents your bottom bracket drop and i use it for some reference measurements for my Bringheli frame fixture.

step two
mark your bottom bracket on the lower line, i also have a neat circle making tool which you can get at an art supply store. for lugged frames, i use the circle that is the internal diameter of the lugged bottom bracket shell. for non lugged frames i use the circle that marks the outer diameter of the bottom bracket shell. make sure when you  draw in the bottom bracket you give enough room to draw your chainstays on the one side and the front end of your bike on the other.
You can now draw the seat tube angle with your protractor. then extend the line with your meter stick. this is your seat tube centerline

step three

mark your seat tube height(this one is 53cm from the center of the bottom bracket to the center of the top tube)  and you can draw in your top tube. this can be done in two ways: you can use the protractor by keeping the same angle you used for the seat tube angle and flipping it over to mark the top tube. if you remember geometry class, if your top tube is parallel, then the angle will be the same as the angle at the bottom bracket. then you can draw your top tube off of this line. the other method. i measure the imaginary perpendicular line from top tube to the bottom bracket line and then use this measurement to mark the line for the top tube. i use this method and then check the angle with the protractor to make sure its exact. its a good means to double check your work.

step four

mark your headtube point on the top tube centerline. use your protractor to draw your headtube angle and use your ruler and draw a line all the way to the axle line. you can check the headtube line against the axle line and you should get the same angle(if your headtube angle is supposed to be 74 degrees, then the angle at the axle line should be the same)

step five

measure the fork rake distance from the  headtube line/axle line junction along the axle line and mark it. i like to put 2 lines, one perpendicular to the axle line and one parallel to the headtube line. the line just needs to be a few inches long for reference purposes. now you have your fork dropout mark.

 step six

from the fork dropout mark you can draw in your imaginary wheel. figure out the radius of your maximum wheel size you want to use(this frame will have 700c x28 tires and the radius is around 340mm). i draw it by hand, but there are a number of tools to make large circles. i just measure from the dropout mark out and make a number of marks and connect the dots. i then mark my desired fork crown/tire clearance with a line perpendicular to the headtube line, then make another line like it for the headset lower stack height(technical information for common headsets is readily available, you can also measure the headset with a caliper) then the last line marking the bottom of the frames headtube

step seven

now you have to add the tube outside diameter for the headtube. this lugged headtube is 31.7mm. i use the caliper to measure half that distance from the headtube centerline and do so on both sides and a few spots along the fore mentioned  line. then i connect the dots and go back and check to make sure its square and the right diameter(this is crucial) 

step eight

now that the headtube is drawn in, we can mark the downtube. if its a lugged frame, you must measure the backside of  the lower head lug to figure out the junction of the head and downtube. if its a welded frame there is a lot more play here and you can put this junction where you deem best. mark the lower downtube headtube junction. 

i have a few different yard sticks that i have found that are exactly the width of  the different downtubes(and seat tubes) i use. this makes it very easy to draw the downtube. i put a notch in the end of the stick to reference its center point and line that up with the center of the bottom bracket. then i line the other side of the straight edge with the downtube/headtube junction mark i just made and then draw the downtube outer lines(then you can go back and draw in the centerline for the downtube)

after that i do the same thing for the seat tube(this frame uses standard gauge tubing, so the seat and down tubes are the same diameter). for the seat tube i put marks for the width of the tube on either side of the seattube centerline  then i can easily locate the center point and draw the lines for the tube.

step nine

do the same thing for your top tube and you are done. if you dont have a straight edge that is the width of the tubing you intend to use, then you have to draw the lines by measuring half the diameter of the tubing from the center line of the tube. for instance, if you are using a 25.4(1 inch) diameter top tube, then you need to make marks 12.7mm( above and below) along the center line and then use the straight edge to connect the dots. this method can be used for all of the tubes.

now your front triangle is done. its important that you check all your measurements because this drawing will be the reference for cutting your tube angles and lengths

step ten

drawing the rear triangle is not as important in my opinion. at least for the way that i build frames(i also use bikeCAD along with hand drawing, so i know my designs are sound before putting them to paper), but i like to mark the rear dropouts and wheel diameter  to get an idea of what it will look line and they are helpful in locating braze ons, bridges, where to cut the stays and figuring the angle of the dropouts. 

measure from the bottom bracket  to the point on the axle line where you want your drop out, then from this point you can draw in your wheel and the seat and chainstays. 

final notes

i draw my frames facing left, but you can do the same thing in the other direction, this is because of the Bringheli fixture i currently use. 

the benefit of drawing the frame in this order is to figure out the headtube length and fork length. if you already know the fork you want  you can change the order you draw the frame.

Quill stem/bar combo

just finished this quill stem and straight bar combo(actually the bars curve back slightly)

it will be a prize for the Burro's 4 Year Anniversary Holiday Deliverycat & Party

i dont have any build photos because i just got a new camera, but this means that i will have more posts of my work with much better photos. 

about this stem:

i machined the quill tube from 4130 stock to get it down to the standard 22.2mm. then i machined the inside of the tube to lighten it up( i could have used thinner tubing, but its what i had laying around)

i made the extension out of 4130  and used some bars i found at Krank It Up community bike shop

i wanted the stem to have a classic look, so i cut the extension tube so that the quill could slide all the way through. i then fillet brazed the bars in place and then made stainless steel caps for the ends of the bars. i capped the back of the extension tube with a Florida quarter.

instead of powder coating or painting the bars, i thought using a gun bluing technique would keep it looking classic. the nice thing about bluing is that you can touch it up easily and you can see the bronze in fillets along with the grain of the metal. the quill and extension took the bluing solution well, while the bars came out a little splotchy.  I think that this must be due to whatever alloy the bars are made from or possibly due to the heat treatment that these bars may have gotten when they were made. whatever the case, i think it adds to the look. 

after the bluing process, i finished the bars with some boiled linseed oil to seal the metal.

more pictures of Matt's touring bike