Brazing in chainstays with a t-tool

[Doug Fattic]

On the subject thread titled “a question about Doug Fattic/Johnny Berry’s t-tool”, Anon asked how to build a rear triangle using this t-tool. In case this question wasn’t sufficiently answered for someone before the thread got side tracked, I’ll give an outline of how to do it here. This method has been used for ages (I used one when learning in England and saw it in many other English shops) and can provide accurate results. I call it the Johnny Berry t-tool in honor of where I got mine. It is possible that somehow somebody might have gotten the wrong impression that it doesn’t work well. ☺

I assume Anon wants to build frames without pro fixtures as a means to make it more affordable. This approach can work if extra time and care is taken to get things right. It’s a kind of fuss and fiddle and double check short of way. Pro builders increase their speed and ease of use by using more expensive and sophisticated equipment.

I also assume that when Anon said he wanted to build “jig-less” he meant without mill and lathe made tooling. It is still necessary to hold things in position with something somehow. What a good fixture does is hold pieces exactly in the right place for brazing. It may even have calibration markings so rulers and protractors aren’t necessary. Then the pieces can either be totally brazed in the fixture or just spotted or pinned in place and then taken out and brazed free. But I digress.

The principle to use when not depending on fixtures is to braze only one joint at a time and then check to see if anything moved. If it has, it can be cold set it back into position before brazing the next joint. This limits and corrects small errors and prevents them from multiplying. If two things are brazed at once it may not be possible to reset something back to where it should be because one might now keep the other from moving. A brazed joint provides a more solid foundation for these accuracy checks and alignment moves. For example a brazed in left chainstay/dropout won’t move when sliding the right stay in and out to find the length that centers the rear wheel.

To start, the dropouts and chainstays are brazed together. Then the left chain stay is brazed into the bb shell. The T-tool establishes its position. The long stem is adjusted to hold the dropouts at the seat stay length. The axle is adjusted to the dropout width (or maybe a mm or 2 more because it tends to shrink in). And a straight edge with an adjustable pointer makes sure the dropouts are equidistant from the frame’s centerline.

This is the most likely place for an alignment mistake to creep in because there isn’t much to hold the dropouts equidistant from the frame’s centerline. One can use some more elaborate fixturing or spot braze the chainstay to the bb shell at its correct length. This will help stabilize it when adjusting the dropout centerline width with a straightedge.

After the left chainstay is brazed in place and realigned if necessary (so the dropout is on the wheelbase line and in the plane and half the axle width from the frame’s centerline), a true wheel establishes the right chainstay length. Once the length is found that exactly centers the wheel, it can be spot brazed in place. After it has cooled and checked again to make sure nothing moved, it might be wise to pin the two together so they won’t shift while brazing. Flux and heat are lubricants for a tube to move in a joint. If it did move then it either has to be taken out and redone or given a nudge with a small hammer while the spot is reheated. Keep in mind that small differences in chainstay length are magnified out by the tire. Of course the t-tool again holds the right chain stay in the correct place for brazing.

This is only a general outline of how to use a t-tool to braze chainstays into the sockets of a bb shell. A detailed step-by-step is way too long for an on-line forum post. Of course I’ll be happy to show this and other methods in one of my framebuilding classes. ☺

A builder needs to use a very well made fixture (like an Anvil) if they want to save time by brazing both chainstays to the bb without a wheel check in between. Cruder homemade fixtures and even some of the less expensive professional ones are just not accurate enough to insure a wheel will end up on the frame’s centerline if the position, spot, check, braze, check, align procedure isn’t followed.

I might add that an advantage for a beginner to braze outside of a fixture is that it is easier to see what’s going on without some part getting in the way. And the unit can also be placed in the most advantageous position and moved while brazing because the fixture stand/holder isn’t limiting motion.

[WadePatton]

Thanks Doug.

[Gregory Townsend]

Thanks Doug,
I found some photos of the legendary Ron Cooper using one.



Full set

Ron Cooper - a set on Flickr

[EricKeller]

I want to get me one of those lab jackets. McMaster-Carr has to have them

Yup, Flame-Resistant Lab Coat. Too bad the light blue isn't flame resistant

[datas_brother]

I want to get me one of those lab jackets.

I got one.

[Doug Fattic]

I visited Ron Cooper when I was learning in England in 1975. He was one of the many that generously spent time with me explaining how to build frames. Several of them told me they didn't mind sharing what they knew with an American since I wasn't going to be in competition with them. Mostly Ron talked about how he aligned frames with a device that allowed the frame to pivot around the bb. As the frame rotated, pointers near the other end of the tubes could show if they leaned one way or the other.

It is also interesting to see Ron's "measuring board" behind him on the wall. There is a clearer picture of it in that Flickr group. This was the British way of designing a frame (instead of a full scale drawing) which then became the template to miter tubes. It later becomes the device against which to set the t-tool. Each builder had their own variation. I brought Johnny Berry’s back. At Ellis-Briggs where I learned they had an old one hanging unused for many years on the wall (Jack Briggs replaced it with a really nice fixture based on a cast iron table). W. B. Hurlow (one of Britain's greatest ever) had two for different parts of the build. The London firm of F. W. Evans claims to have invented this type of fixture in an advertising brochure in the 30’s. You can find a copy of it on Mark Bulgier’s website where he has a scanned collection of old bicycle catalogs. Essentially it is a rectangular frame holding the four flat pieces that represent the main triangle tubes. The bottom of the frame is the wheel base line. The fixtures that I have laser cut and etched out of stainless steel are an upscale version of the concept. They are a bit more like what Alex Singer in Paris used on top of his alignment table. When not in use he hoisted it up towards the ceiling.

The methods these classic European builders used with simple tooling can be valuable to the hobby or part time builder today that isn’t going to shell out big bucks for the expensive equipment we pros now use in the States. Their livelihood depended on fast and reasonably accurate results. Over the years they had weeded out what didn’t work well.

By the way, we used lab coats at Ellis-Briggs too. They kept your work clothes clean and looked professional.

[pruckelshaus]

Personally, I think looking professional is important, otherwise people don't take you seriously. When I worked as a shop mechanic (I was a terrible salesperson, I couldn't sell a bucket of water to a camel) I was the only wrench who wore khakis (Dickies work pants, nothing fancy) and I would wear a polo or chambray work shirt. I found that customers took me a lot more seriously than the other mechanics who were running around in tees and shorts.