Archive for February, 2009
…whenever see a nice bike, the first thing I look at is the dropouts. Actually what I look at is the dropout/stay junction. I’m obsessed. Unfortunately, because of this I spend waaaayyyy too much time on getting my dropouts to look just the way I want.
Here’s some pics of some dropout goodness. These are Columbus Life stays paired up with some stainless steel Paragon Machine Works sliders.
This is the stay after braze, just out of the soak tank to remove the flux:
These are the dropouts after a bit of finish filing. Once the stays are on the bike and the seatstays are on, I ‘ll spend some more time polishing these up. Then they’ll get covered in about 3mm of powdercoat and you want be able to see any of it!!!
Currently playing in iTunes: Khanyange by Dorothy Masuka
Michael, you called but the number you left must have been written down wrong ’cause it no worky. Give me another call or drop me an email.
Sorry about that.
There’s some discussions on framebuilding mailing lists and forums at the moment concerned with mitering tubes and what the best set-up is.
A couple of people have asked me how I do mine and if I use a fancy jig or not, so I thought I’d post a quick run down on how I miter my chainstays.
Firstly, I need to know what the actual length of they stay is, measured from axle center to center of bb. This is the actual length and not the horizontal length. My drawing shows the stay length as the horizontal length and the actual length. I double check the actual length by physically measuring it on the jig.
This picture shows what I mean. The number I’m interested in is 455, the other number is what I use to set up the length on my jig using the built in scale.
I normally tack the dropouts before I miter the bottom bracket end. My drawings give me the dimensions I need to cut the stay at the dropout end and once I’ve done that I slot and tack braze the dropout in place. See earlier post for more details on how I do this.
This is a pic of the tacked stay:
This would actually be pretty strong as it is (you can maybe see the nice internal fillet) but I’ll fill the void later ’till it looks something more like this:
Next, I lay the stays out on the alignment table and bolt them to a dummy axle. I then use a normal engineers square and steel rule to measure and mark the length of the stay, in this case 455mm. I also mark the vertical centerline of the stays at this point too.
Once I’ve marked the stays, I take them to the lathe and bolt them one at a time in the milling vice. I again use a square, and a straight edge to make sure the milling vice is at the correct angle to ensure the cutter will miter the tube exactly perpendicular to the dropout (or parallel with the axle if you prefer). You can buy all sorts of fancy jigs for holding stays for cutting in the lathe or a milling machine but I find this works fine. Keep a slow feed rate and even the thinnest tubing is easily cut. I can’t really believe a fancy jig would be much quicker for me to set up but if someone wants to send me one, Ill try it out!
Here’s a pic of the stay in the vice.
You might be able to make out a cross marked on the stay. This is the 455mm length and the centerline. I line this up with my patented centerpointerometer.
The centerpointerometer is just a pointed stick shoved in a hole but in a kinda precise manner. I’ve center drilled and reamed all of my hole-saw arbors to take a 6mm rod with a ground point. This allows me to precisely set up tube lengths for mitering. This is used for all my tube mitering not just for stays.
I don’t change the angle of the milling vice between stays and this makes it really quick to create a nice matched symmetrical pair.
Depending on the tube wall thickness, I’ll either hand feed or use the powerfeed. Here’s an action shot!
The result, one nicely mitered pair of stays. Couple of swipes with some shop cloth and we’re good to go.
That’s all for now.
Currently playing in iTunes: Katie Belle by Steve Earle, Townes Van Zandt & Guy Clark
view from the workshop backdoor
Currently playing in iTunes: State Of The Nation by Deltron
Wow, things have been very slow in the workshop this past few days. It’s been about -68° out there, Jane’s now 11 months pregnant and Jack (our 3 year old) has chickenpox. Hopefully this weekend will see more progress.
Currently playing in iTunes: Blow Wind Blow by Kenny Roby