Coupler Questions

[Andrew R Stewart]

Hey all- So my shop continues to get set up. Today I struck a flame for the first time (in my own shop) in a couple of years. I melted the end of a 6x32 all thread rod then checked all the torch fittings for leaks and such.

My question is this: How do others insure that a coupling (S&S) is brazed into the tube and the two ends of the tube are in line with each other.

Starting with square miters do you fixture the set up asnd fully braze? Or do you tack and free hand the finish brazing? Other methods? I've seen the CoMotion method of fixing the tubes to a length od Alu channel but was not able to ask further questions.

I know that it is not too important except to have the jointed tube look "straight". Miters and build alignment will ditermine the frame's final alignment.

Second on the question list is the place to miter the tubes. With the shorter "working" lengths of the TT and DT the miters are going to end up very close to the thin wall sections. Any suggestions or guides? I followed the recent "How Much Butt Is Acceptible" thread and assume the same holds true for the coupled tube.

[markbeaver]

On alll of my new-build S&S bikes, I build the main triangle as per usual and build the rear triangle as usual, then mount the frame in my jig, lock the jig, take out the frame and cut up the frame taking out the requisite 34.9mm of tubing where the couplers will go. I braze the couplers with the frame in the jig. I always get rear triangle alignment within 0.5mm with this technique so I'm most comfortable with it. Certainly others have built the couplers into a tube then built the frame but I prefer the former method.

Regarding the butt zone concept, I would certainly ideally like to use tubes with a really short butted section but have built S&S with pretty standard tubing as well - if you are really good at silver brazing I feel that the frame's strength isn't compromised - but ultimate durability might be better if you can get the thick butted section in the coupler zone.

[e-RICHIE]

atmo the most seamless way to build a coupled bicycle is the same way you would retrofit them.
take a frame, cut out the required amount from the first tube.
add the first coupler.
when it's coupled, attack the second tube and couple it.
don't couple the two tubes and then build the frame.

[Dave Anderson]

don't couple the two tubes and then build the frame.

To each his own, as my dad used to say....... but, this is exactly how I do it on new frames (as apposed to retrofits, of course, where I do it the "cut out a section of tube" way). It's just a personal preference on my part... I use a jig that I made for the purpose (see below....note: its a loose copy of one that Bob Brown uses), which keeps everything straight, solid and allows good access. Also, I like to keep the coupler in the butted section of the tube if I can and that 34.9mm of tubing can sometimes make a difference (in other words, I don't cut it out, but simply splice and therefore, "extend" the tube 34.9mm with the coupler). I am also only cutting the tube once and by using a Park cutting guide clamped in my vice I can keep the cut straight with good access.

Anyway...as I said...its just a personal preference on my part....

Dave

PS: I miter the tube after the coupler has been installed....the biggest thing is making sure that the tube is positioned when mitering so that the coupler lines up with the lugs properly when brazing the frame later...which, depending on your mitering set up, may not be as seamless, as e-Richie says, as simply cutting the tubes on a finished frame and sliding in the coupler.

[anthonymaietta]

I did a 4 (or5?) part blog series on this about a month ago. Here is my process in bullets for a top tube:

1. Miter TT/ST joint
2. Mark line to cut holding up threaded coupler lug
3. Make cut near ST end
4. Clean and flux little stub of a mitered top tube and threaded coupler lug
5. Orient the threaded coupler lug on the stub (I prefer points on the side, some lke them on the top)
6. Braze threaded lug to stub with the stub sitting in the coupler lug vertical
7. Dry fit the other coupler lug to the remaining long piece of top tube
8. Hold up to frame and mark were you need to cut to remove material for TT/HT to have some butt
9. Cut out section of top tube
10. Clean and flux long section of top tube and non threaded coupler lug
11. Braze non threaded coupler lug to the long piece of top tube (orientation does not matter)...I put the top tube in a Park stand and put one tack with the tube horizontal, then I rotate the tube to vertical with the coupler lug at the bottom and continue brazing
12. Hot soak everything to get the flux off
13. Install coupler nut
14. Thread the coupler together
15. Treat this as a "standard" top tube and make your TT/HT miter in phase with the TT/ST miter

Pictures and more words in my blog linked below.

Tony

[EnginCycles]

The issue with putting the couplers in before construction is the loading of tubes. I have seen so many bikes with couplers that when you take apart they spring away from the other half of the coupler. This is from the tube being joined after the coupler. Nobody installs more couplers than Bilenky and they add after construction. If you do it enough it is just as fast.

-Drew

[e-RICHIE]

The issue with putting the couplers in before construction is the loading of tubes. I have seen so many bikes with couplers that when you take apart they spring away from the other half of the coupler. This is from the tube being joined after the coupler. Nobody installs more couplers than Bilenky and they add after construction. If you do it enough it is just as fast.

-Drew

actually, it's also faster atmo.

[anthonymaietta]

The issue with putting the couplers in before construction is the loading of tubes. I have seen so many bikes with couplers that when you take apart they spring away from the other half of the coupler. This is from the tube being joined after the coupler. Nobody installs more couplers than Bilenky and they add after construction. If you do it enough it is just as fast.

-Drew

To me that is physical representation of the builder adding stress to the frame through poor tacking and joining technique; not the sequence of coupler installation. Adding the coupler after the fact does not give you any opportunity to choose how the couplers, joints and butts interact.

[Dave Anderson]

To me that is physical representation of the builder adding stress to the frame through poor tacking and joining technique; not the sequence of coupler installation. Adding the coupler after the fact does not give you any opportunity to choose how the couplers, joints and butts interact.

Agreed....I've never had one of my bike's "spring away" when decoupling after it was built. Also, I've seen Bilenky do it before as well.....


Not to mention...if the bike is built such that the tubes spring away when its decoupled, they are going to spring away when they are cut in half to install the couplers as well....there is no right way or wrong way...both methods work.

[e-RICHIE]

Agreed....I've never had one of my bike's "spring away" when decoupling after it was built. Also, I've seen Bilenky do it before as well.....


Not to mention...if the bike is built such that the tubes spring away when its decoupled, they are going to spring away when they are cut in half to install the couplers as well....there is no right way or wrong way...both methods work.

work on creating the structure such that it would not spring apart if cut apart up atmo.
it's the little things.

[Dave Anderson]

work on creating the structure such that it would not spring apart if cut apart up atmo.
it's the little things.

+1

Dave

[Andrew R Stewart]

Thanks all- I'm leaning towards the "install the coupler first then miter the tube" method. It is interesting to read of other's experiences though.

Dave- Thanks for the jig shot.

[Dave Kirk]

I always install the couplers into tubes that I then miter and install in the frame. This allows me to closely control the butt lengths to be sure I have the thick stuff going into the coupler.

I also have a different, and some might say, less compelling motivation. I learned during my production days to do tasks in a sequence such that the riskiest tasks come at the front end of the procedure. This limits the possibility that you will invest a considerable chunk of time into a frame than then make a mistake and have to scrap it or at a minimum do a bunch or rework. In this case, with regards to couplers, you install them into a tube and if you eff it up you toss just a tube and nothing more. if it's a built frame and something goes wrong you at a minimum have to replace the top and down tubes if not more.

By following this philosophy one does some things in an unusual order sometimes during a build but when you make that one in a 1000 mistake you pay much less for it. As an example I always do the machining and alignment of a frame before I do the finish work. No sense is putting in the finishing labor into a frame that does not meet alignment standards.

Risk assessment and minimization are the new black.

dave

[e-RICHIE]

i always add braze-ons to the tubes and then make a frame from them.
otoh, coupler brazing (and even taking out the requisite 1 3/8" or whatever it is) is beyond easy for a skilled brazer atmo.
sweating in some filler metal in a part designed as simply as the S+S couplers are is simpler than adding any other small part.

[e.Gellie]

......Second on the question list is the place to miter the tubes. With the shorter "working" lengths of the TT and DT the miters are going to end up very close to the thin wall sections. Any suggestions or guides? I followed the recent "How Much Butt Is Acceptible" thread and assume the same holds true for the coupled tube.

Andy,
earlier this year I asked a US retro-fitter of couplers with the most extensive experience this question:
Q: have you had success retrofitting SandS couplers and straying into the thin part of the tube butt instead of replacing the whole tube?
A: We have had very good sucess with retrofitting into the taper section and thin wall of most tubes.

Cheers,
Ewen

[steve garro]

I guess I will chime in. I just free hand them in a vise after tacking both of the tips of the "lugs" - I have done 4-5 this way. no alignment issues {but, that doesn't mean it's possible} then miter as usual. just treat it like a tube. as for tubing: there are tubes like the HOX2TT and the HOX3DT2 that have butts of 200mm+ = good for couplers. *however* - I have a slightly different take after my last bike. it's a touring/travel bike, after all - so I did it out of .028"/.035" 4130 for dent resistance/less whippyness while loaded with gear {or, just plain loaded, I guess - that shit happens on tours :} .....} . all the ones I have done were to be ridden with baggage, not "day rides" - YRMV. - Garro.