flux removal problem

[schollen]

I am currently finishing up my second frame/first frame on which i brazed anything. first frame was completely welded. when i made the rear triangle i welded the ss and cs to the frame first, then brazed on the dropouts. The vent holes i made in the bb and st are really small and i am not sure a good way to get water in them other then maybe sitting in the bath tub for a couple hours ....then getting water out will be just as difficult. i am concerned that this will subject the frame to water for too long and im not sure how i will even get frame saver into these tiny holes which seems extra necessary if i soak if for a couple hours. any suggestions. also any suggestions on removing the really hardened / somewhat burnt flux that is around the dropouts. Soaking for around 10 minutes removed most of the flux but there is still some really hard flux that needs to be filed off which is really difficult in the weird geometry type places.

Scott

[echelon_john]

drill more holes near/in the dropouts?

yes on the bath tub. dry thoroughly afterward. you can use forced air to against the holes you drilled (assuming second holes inside bb/at st junction) to vent/blow out excess liquid.

[Dancingbear]

A couple of hours soaking will not do anything to damage the frame, and to remove the remaining moisture just warm with the torch- once you cease to see any more steam come from the vent you are dry.

[PaulE3]

I had some tough spots that would not come off so I submerged that area longer, more like 6 hours... no remaining flux after the longer water bath. Torch dry.

[Mark Kelly]

An old chemist's trick for drying anything you can't reach: wash the water out with ethanol ("methylated spirit" will do), then wash the ethanol out with acetone.

[Boedie]

"Soaking for around 10 minutes removed most of the flux but there is still some really hard flux that needs to be filed off which is really difficult in the weird geometry type places."
It will usually take longer than 10 minutes, however this possibly suggests that your water is not hot enough. I use a crock pot that allows me to stick each joint into the crock pot to get the torch baked-on flux, then do a final soak.......yes in the bath tub, which the wife really hates- but at least it gets me to clean the bath tub after each soak. You can usually find a crock pot for $5 at a thrift store.
Chris

[Andrew R Stewart]

I, also, find that the hotter the water the quicker the flux removal. I use a bucket placed under my wash sink and dribble the hot water to keep it hot. Two vent holes that are large enough to let water flow (I use 1/8") at the ends of the stays/blades work for me. Any residual water is driven off with a torch or baked in the oven. (I placed my recently done fork in the oven after the pizza was done and while the oven was cooling off. After eating the pie the fork was dry.) I seal my vents in stays and blades with a nail brazed in place after I'm done with all brazing. The main triangle tubes are left open (and also vented at both ends).

What I don't do any longer is try to get fancy and hide the vents in unseen locations, but leaving them open. Inside the brake bridge, inside the seat tube are all spots to trap liquid and sand that will reemerge during the painting. I've pissed off painters before and now listen to their preferences. A happy painter is a motivated to do a nice job painter. Andy.

[schollen]

Awesome thanks for the help. Ill plan on trying to fill the stays with water in a tub tonight. I currently dont have any holes in the stays near the dropouts but i suppose i could drill a couple if i have trouble filling the stays. When you say you use a nail, do you just braze a steel nail in then grind it down to make if flush with the stay after your done the water bath? Also do you apply any frame saver right after the bath or wait until it is painted. I will be having my frame powdercoated and I am hoping to drop it off tomorrow assuming the soak tonight goes well so it will not be just sitting around too long rusting. Do you normally spray the frame saver into the ss and cs as well as the main frame tubes?

[Dancingbear]

Your frame saver is AFTER paint. Or you may have a grumpy powdercoater.

[druptight]

Your frame saver is AFTER paint. Or you may have a grumpy powdercoater.

Seriously ^^^^ You want to deliver your frame to paint with NO oils in/on it anywhere. I clean the daylights out of it with mineral spirits beforehand personally.

[schollen]

ok thanks, good to know

[echelon_john]

And yes on brazing the nail and filing/sanding it flush.

Generally the 2 schools of thought for venting seatstays is:
- Get as much flux out as possible, seal it up, no framesaver
OR
- Leave 1-2 escape holes, ensuring it 'breathes'/drains, and use framesaver.

- Chances are your fork blades have vent holes in the crown/steerer, so for forks it makes sense to have another hole at the bottom of the blade and use framesaver.

[emanuel]

We close off all vent holes here, then drill a BB drain hole.
For the flux, even cold water works,then dry off with torch as other have said, careful, I've had a fork explode and the blade fly a couple of feet due to trapped moisture. It was an old pressed crown that had let water seep in through the seams. makes quite a bang.

[schollen]

do you close off the vent holes for the ss and cs at the bb? or do you just have vent holes near the dropout that you close off. currently i only have two small holes in the bb that go to the cs and two small holes in the st that go to the ss.

[Andrew R Stewart]

do you close off the vent holes for the ss and cs at the bb? or do you just have vent holes near the dropout that you close off. currently i only have two small holes in the bb that go to the cs and two small holes in the st that go to the ss.

I'll leave the chain stays open at the BB. If the Shell is a fillet or welded one then I'll make the vent holes big (for all 4 tubes), maybe 3/8". Big enough to let water and air pass through at the same time. Or a red spray tube and air... As i mentioned before I stopped doing vent holes in the ST for the SS.

I agree with echelon j in there being two choices. 2 vents big enough to drain water from or none. Both ways should get internal cleaning before sealing off vents or painting.

AND NEVER USE OIL OR RUST INHIBITOR PRIOR TO PAINTING OR BRAZING.

emanule- Did the blade that blew up freeze? If the tube and brazing were good this is the only way i could see the blade or joint failing due to internal pressures. Andy.

[emanuel]

It was an old stamped crown, the seam let water in when soaking, then when heating it contracted and trapped the vapour in. I thought it had all come out. It was one of the first times handling the torch...my ears were ringing for a few days.

[G-reg]

My rookie opinion on vents:

I'm in the vented with frame saver camp.

TT/DT at HT, smallish vents in the HT. No sense in getting cute or over sized.

TT at ST, smallish hole low in the joint so water in the TT has a chance to drain.

I tend to offset my chainstays and downtube "down" on the BB, and occasionally the ST "forward." Like with the TT/ST, the vents are placed low in the joint so they are at the bottom of the joint when the bike is built up.

I vent the seat stays at the dropouts only, and the chainstays only at the BB. It takes some work in the tub to get water in those single vent tubes, but just fiddle with it until bubbles stop escaping. A kiss with the torch will dry it out, a good Powdercoater will pre heat a frame to cook off water/oil/solvents before the powder steps.


If you overheat the flux, it's not going to soak off. Don't use your good files to try and get it off. And don't worry too much about leaving a tiny bit of flux in the stays. You obviously don't want clumps rattling around. But the potential for extra corrosion from flux remaining in the tube is not going to be the limiting factor the lifespan of frame #2

[Curt Goodrich]

My rookie opinion on vents:

I'm in the vented with frame saver camp.

TT/DT at HT, smallish vents in the HT. No sense in getting cute or over sized.

TT at ST, smallish hole low in the joint so water in the TT has a chance to drain.

I tend to offset my chainstays and downtube "down" on the BB, and occasionally the ST "forward." Like with the TT/ST, the vents are placed low in the joint so they are at the bottom of the joint when the bike is built up.

I vent the seat stays at the dropouts only, and the chainstays only at the BB. It takes some work in the tub to get water in those single vent tubes, but just fiddle with it until bubbles stop escaping. A kiss with the torch will dry it out, a good Powdercoater will pre heat a frame to cook off water/oil/solvents before the powder steps.


If you overheat the flux, it's not going to soak off. Don't use your good files to try and get it off. And don't worry too much about leaving a tiny bit of flux in the stays. You obviously don't want clumps rattling around. But the potential for extra corrosion from flux remaining in the tube is not going to be the limiting factor the lifespan of frame #2

Regarding your placement of vents in the bb shell, I'd abandon that approach. Bontrager and others have shown vent holes too close to the edge of the tube can lead to cracking. Also, on the seat stays if you're going to have only one vent hole you will have rust problems that could be avoided. Put in a second hole and the water will drain out nicely after the bike has been ridden. Or seal them up.

[G-reg]

Thanks Mr. G,

That all makes sense, I should have phrased it "low-ish."

[schollen]

thanks everyone for the good input. I was able to get a 1/8 drill bit into the bb and st to open the two existing holes so that i could fill the stays with water. i was a little nervous about drilling a hole near the dropout...i dont know why, just did so i left that area alone. soaked for about 1.5 hours then drained. i noticed that one of my braze joints at the dropout had a tiny pinhole in it so i rebrazed that joint. the frame is off the the powdercoater today so cross my fingers and hope i got everything...good enough. and i agree that if this frame is going to fail it will probably be at the patched weld job from where i burnt a tiny hole, or combo weld/braze joint at the ss st junction because i didnt have the skills to weld the ultra narrow gap between the two ss...not from some tiny amount of flux left in the tubes. Anyway here are some pics before painting. thanks again for all your help. going to start planning frame #3 and do some more practice welding on tight spots.

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