BigPoser

So in my quest to try new things while building, I've been putting together a frame and TIG welding it this time around. I have the front triangle together with the chainstays. The front came out great but it's the stays that I have an issue with. While checking the rear alignment with a wheel, I notice that it's off. When measuring, they are off by 1 mm. Not sure how I missed this when welding it, but I did. When looking forward directly from the rear, the rear wheel points a bit to the right. Please see the pics for reference.

Is my frame now a large paperweight? If not, how can I fix this? Am I totally hosed on this?

All advice is appreciated because I need some help. Thanks.

Brandon

Doug Fattic 

Getting the chain stay lengths just right is about the hardest thing to do building a frame. A length difference of 1 mm results in almost 3 out by the tire. Therein is the problem tig welding with vertical dropouts because there is no room for any error. It is particularly problematic when hand mitering. The classic builders used socketed bottom bracket shells where they could slide the stays in and out to get them to the right length and wisely chose horizontal dropouts with long screw adjusters so the correct length was not an issue.

You are an excellent example of why if a builder wants to tig weld they need to machine miter the chain stays and have really good fixturing to get this part of the build right. One way I can think of doing it without those expensive tools is to weld the chain stays onto the shell 1st and then slot their ends so the dropouts with tabs can slide a little back in forth until the true build wheel is centered. If someone is using hooded dropouts it would take an incredible amount of patience and fussing to get the wheel to center properly.

In your case is it possible some part of the alignment is off which prevents the wheel from centering? Are you positive the dropouts are equidistant from the center of the frame? And also are your dropouts parallel to that plane? In other words are your H tools off because the dropouts are not parallel to each other or because the stays are a different length?

dsaul

Its certainly not time to trash it yet. Do you have room in your design to shorten the chainstays? You could cut off the dropouts, grind off the welds, adjust the lengths of the stays and re-weld the dropouts. If done carefully, you'll only lose a few mm of length. You could also switch to a plate/tab style dropout and keep the chainstay length you want.

If the dropouts are just tacked, you can easily cut the tacks and shorten the long side. I'm sure someone will comment about heat cycles, but I've never found that to be an issue. As long as you didn't cook the joint and introduce contaminants to the metal, it should be fine.

As Doug said, make certain it is not an alignment issue before cutting anything.

Andrew R Stewart 

I almost disregard the "H" tools till after the seat stays are attached. Sure I bend the drops to be roughly parallel but as Doug said these tools do nothing to tell you about a wheel's alignment, just whether the drops are parallel to each other.
Looking at the second photo with a wheel installed I see very little (hard to even say with this view) of chain stay length misalignment. I do see quite a bit of uneven "height" of the drops. So is there were seat stays attached the L:H SS would be shorter then the RH one is. I would simply bend the CSs to achieve the correct SS length and their evenness, as confirmed with a good wheel installed prior to attaching the SSs.
What type of tubing is this? Have you tried any aligning efforts yet? I find about every CS assembly I have done requires some amount of tweaking to improve alignment before the SSs are attached.
Last thing is if you decide that you have to remove and toss out the CSs and drops I would first take this as a learning moment and find out what it takes to end up with a well aligned situation. Bending to line up, filing slots to seat the axle so the wheel is on plane. Andy

Nessism

Even though it may be frowned upon by most pro builders I've found that a little rear dropout filing and filling can help correct rear end build errors. This assumes you have suitably beefy dropouts of course. File one side of the slot and fill the other as needed so the axle will be held tight. I don't recommend going more than 1mm or so using this technique but that will buy you a lot of alignment correction at the tire end of the wheel.

And BTW, if you aren't set up to check alignment of the rear end using your surface plate the string test is a pretty good ghetto test. A thinner string than shown and align off the face of the dropout is recommended. Use something more accurate than a tape measure to measure too.

unterhausen

are you sure one stay isn't just lower than the other? looks like that to me. If that's the case, it will probably submit to an application of force. Otherwise, file it.

Is the bike for you?

BigPoser

Thanks for the comments. So a few things. The dropouts are fully welded. I think I do have some wiggle room if I needed to cut the dropouts off and start again. I'm limited with my alignment tools, but I do have a table that, while the entire table isn't perfectly flat, I know where the flat areas are and aren't. I can use it somewhat with a BB post that I have. I'm working on getting a legit alignment table such as the Bringheli. I also have a Park ***-2 that I use and when measuring the dropouts they are extremely close. I will say though that with hooded dropouts it's a bit tougher to measure.

Regarding the alignment of the front triangle, I've put the frame in the post on my table (with the NDS facing down) and measured the center line of the frame all around. The worst spot is at the ST, TT junction where it is about 2mm low of center. The HT and DT are about 1mm low and get better the closer I get to the BB. My thought on aligning this would be to put a 2x4 or something through the frame and prop up one end and then apply some force downward, forcing the tubes to come up. If that even makes sense. Having said all of this, I should probably face the BB and then check it all again.

Andy - I see what you mean regarding the height and I'll have a look at it this afternoon when I get home. Correcting the height would align the top of the wheel, but it would still be pitched to the right, right? Even if the stays are equidistant from center, wouldn't the wheel remain in the same direction? Just trying to wrap my head all of the alignment tips and tricks.

Thanks all!

Brandon

BigPoser

I'll have a closer look at the height of the dropouts when I get home today. Frame is actually for my wife, so I really want it to be correct.

Doug Fattic 

An easy way to check is by putting it on the post on your alignment table and use a machinist square to see if the vertical part touches the end of both slots equally. Bend as necessary .

BigPoser

Thanks Doug. I didn't get to spend much time on it this evening, but I did put up a square up to the drops outs and there is about a 1-1.5mm difference. When trying to bend them, I notice that the BB is twisting. I assume that the twisting is only a result of the forces that I'm putting on it and shouldn't be an issue. I still need to face the BB though and I'll check it out again.

unterhausen

you can get a rough idea of the height issue by putting the frame on a flat surface resting on the bottom of the bb shell. Then you can compare the relative heights of the dropouts

BigPoser

So after some further investigation it turns out that one of the chainstays is in fact higher than the other. Turns out they were welded on the BB about 1mm off. Rookie mistake. Of course I figured that out after I was trying to align the stays myself and ended up denting the under side of the DT. Yet another rookie mistake.

You live and learn I suppose and I def won't be make those mistakes again.

Time to order some more tubing I guess.

Thanks for all the help.

Brandon

unterhausen

sorry to hear that.

BigPoser

Me too! Don't think I'll get it done before Christmas now.

Cynikal 

For a 1mm difference in height, can't you just file .5mm on the low side and add .5mm on the high side?

Andrew R Stewart 

I believe the 1mm difference was at the BB end of the chain stays, not really a factor for the drop out end. How was the frame supported during the realigning of the stays? I also asked about the tubing used before, is it super strength heat treated stuff? Here's a opportunity to teach us what not to do. Andy

Doug Fattic 

Brandon, isn't it still possible to bend one or both stays a little so they are equidistant? Unless they are heat treated I would think that is possible. Also the down tube dent could be filled with silver (or brass) and filed to remove most of the dent. Of course it might still eventually crack there but this frame could be used as a way to check your wife's fit and ride. When I was learning in England it was routine to fill dents with brass when frames came in to be resprayed.

Another method is to round out the edges of the dent by squeezing it hard in a vise with an aluminum block. That will reduce the size of the dent a little. Then it can be filled with body putty before painting (and touched up again with spot putty after primering).

BigPoser

Andy, you are correct. The difference is at the BB where the stays meet so they are off the entire length of the stays. The tubing is Nova so not sure if they are heat treated but will say that they are pretty damn strong. I had the DT in some wood blocks in the vice and I had it set up so the stays were facing me at about waist level. I was then attempting to lift one stay while pushing the other stay down. In doing so, the DT was pressed against the slide of the vice and dented it. I thought there was clearance, but there either wasn't or there was initially and it disappeared while trying to muscle the stays around.

Could I still correct them using a lever of some kind?

BigPoser

That is good to hear. If you think the dents can be filled and cleaned up then I'll give that a go for sure. That would sure save me a lot of time and I'm thinking my wife really won't be putting the frame through any unnecessary stress since she's a total noob.

I just need to work on the stays.

Thanks Doug.

Andrew R Stewart 

The description of the dent suggests that I would do the same a Doug mentioned. Fill and move on. Taking care to avoid tube to hard metal (vice edges) contact is a constant due diligence. I've done this a couple of times too.

The small amount of stay length difference due to one stay being slightly higher up on the curve of the shell might best be dealt with filing the slot a tad. If the slot opens up a lot then braze in a this "shim" on the slot's back face (between the surfaces that the axle clamps onto) and reform the slot to fit and be aligned. I've done this more then a couple of times Andy

unterhausen

I have been trying to figure out how to bend the stays in this direction, and it's not particularly easy. As you discovered, there needs to be a secure way to hold the main triangle from rotating.

As far as bending, I think the gold standard of such things is the Park FFS-2. We used to straighten a lot of bent forks when i was a bike mechanic, the FFS-2 works great. Although I may have used the FFS-1, I don't see the difference.

dsaul

If it were mine, I would fill the dent with silver. As to the stays, you may not be able to bend it so it stays on its own, but a seat stay will hold it where you want it. If you have determined that the height difference is the reason for the misalignment of the rear wheel, put it back in a fixture that will hold the dropouts where they need to be and tack in some seat stays.

unterhausen

BB shells will bend more easily than you might expect. Put something in there to help it hold its shape, bb cups should work fine

BigPoser

A quick update: I've been recovering from a small medical procedure and haven't felt like doing anything. So today I was finally able to get in the shop and work on aligning everything. All in all, I was successful. A little filing here, and little tweaking there and got it all lined up. Damn near perfect. Finished the seat stays as well and now just need to have them welded in. I should be able to get it all done in about a week or so with work and all.

Thanks for all the tips and advice. I really appreciate it.

Brandon

Andrew R Stewart 

Sometime building needs a pause before going forward again. Andy