the tell all NO HOLDS BARRED alignment thread atmo -

[Craig Ryan]

I think it would be nice if someone made and marketed sets of very light cones and rods for headtube use. Something to minimize sag. I currently use an all steel unit and I have to really watch it.

[e-RICHIE]

I think it would be nice if someone made and marketed sets of very light cones and rods for headtube use. Something to minimize sag. I currently use an all steel unit and I have to really watch it.

to allay that, the tubes always have to have a jack beneath them atmo.
i have a bunch of campagnolo HT reamer/facer cones and had my Brown + Sharpe pal make an 18" steel rod to be a honeymoon fit.
i use it for all set ups and intermediary checks.

[e-RICHIE]

I check my frames rear end on the table with a wheel as Dave pointed out, but I also verify my seatstay length with my frame in the vise with the rear wheel in. I place a straight edge across the head tube and seat tube even with where it lines up with the top of the rear wheel. with the materials I use and wheel I build with, I get 4mm to the straight edge from each side of the rim at the wheel's top. I find it hard to measure the space between the rim and stay accurately, so I also have a Spudnik wheel checker.

i use an 8" warding bastard file and keep moving it between the stay and the rim, site the space leftover, and move it to the opposing side.
it's a surrogate interior depth gauge that's close enough for my government work.

[edoz]

Eric- If your rear end is out 1/8" each time my question is this. Are you fitting the chainstays with no gap using this error? If so the chainstays are being cut to two different lengths and you are fighting a downhill battle once you pull it out. This is why it is so important to have a good fixture. Do you have an accurate way to check chainstay length? Are you leaving one stay un-attached at some point to align before final tacking or brazing? Fix the fixture is my advice.

Cheers,
Drew

Good point Drew, thanks. I've left it that way because I can braze the chainstays and have them pull very close to centered, and with so many of my frames having adjustable dropouts it really hasn't been much of an issue. I fixed the offset in my fixture a little while ago, and I'm contemplating another revision of the dummy axle holder. That might be a good project for when I get my mill wired up.

[thegroundup]

Just for shits & giggles - check a frame, set it in the sun with one side out until warm & then quickly bolt it down & check it out - fun! - Garro.

We did that here at the tandem factory... we just rubbed one side of the top tube with hands while it was in the alignment fixture and that was enough to see a few thousands deflection as it warmed and cooled.

My big question now is bent Titanium... has anyone seen tubes lose some of their bend over time due to inconsistent stresses in the tubes or process of bending? Is there a known procedure for post bending stress relieving?

[suzyj]

I don't have an alignment table. I am thus clearly an object of ridicule and scorn. :P

I have a nice set of Mitotoyo calipers, but they're old fashioned vernier ones, accurate to 0.1mm, 0.05 if I squint. I also have a handy straight bit of aluminium extrusion (well straight within +/-0.5mm over a meter, anyway)

The things I care about are really quite simple. I want the head tube and seat tube in the same plane, I want the dropouts centred and parallel, and accurately positioned, and I want the head tube to be at the right angle to set trail.

In order to get things as accurate as I'm able, I leave my head tube uncut; a full 600mm long, until after the seatstays are brazed in place and the bridges added.

To ensure the head tube and seat tube angles, I measure with a big protractor, that's accurate to better than half a degree. Head tube to down tube angle, and seat tube to down tube angle, and finally seat tube to chainstay.

I check head tube and seat tube are in plane in two ways. Firstly, I sight along them. You'd be amazed at how little it has to be off to be quite obvious. Second, I lay my alignment stick (tm) across head tube and seat tube, at one end of the head tube, so it runs up between the dropouts, with a 1.6mm bit of sheet between it and the seat tube to account for differing seat and head tube diameters. I measure to the dropout faces, then realign my stick to the other end of the head tube and repeat.

I haven't worked out yet what sort of error is acceptable - on all my frames so far the difference has been under 1mm, and measurement uncertainties are most of that. This makes sense - the lugs are symmetrical left to right, so the heating should be approximately even one side to the other.

To get the dropouts centered wrt the head tube/seat tube plane, I just repeat my measurements having flipped the frame over. Again, difference from one side to the other has always been less than 1mm.

That gets the dropout faces lined up. I use a wheel to measure the position of the dropout slots, by just measuring the distance between chainstay/seatstay to rim, then flipping it over and repeating.

I haven't done a frame yet that didn't require a little bit of filing of dropouts to get that one accurate - again, to within a mm at the rim. they've only been out by a mm or so to one side, so a few strokes of the file have been ample.

The final arbiter is whether it rides well no hands.

[EnginCycles]

It seems Suzy, Eric and many others use a beam or a Park FAG style tool. If I was using this method I would use the string method as it allows adjustment while the tool is in place and allows checking along the way. All it requires is 2 rubber bands, fishing line and a caliper. Clamp the frame by the BB in a solid vise and put the string in place with the rubber bands both exiting the inside face of the drop out and have the string wrap around the HT. Measure the gap at the seat tube to the string on both side and adjust accordingly. It is rather easy and effective. Even better is this method while using a Park BB alignment stand (I have some of the Cannondale pneumatic ones) that has a beam rotating around the plane of the BB shell. I have 2 for sale but that is another topic.

-Drew

[steve garro]

The thing with a FAG tool or a string is that it's hard to tell if it's the ST or the HT that you are seeing as "out" - Garro.

[e-RICHIE]

when we were at witcomb and witcomb usa, front triangle alignment was check with a 3' section of aluminum stock - the kind the hardware store sells - that was about 1/4" thick by 1" wide. we'd have the frame in the vice so some of the shell was exposed, and we'd lay the 1/4" edge of the stock against it and measure the space between it at the bb end and site it until the end of the seat tube (or down tube). iirc the part had a pointer rigged at one end so that it could double as a depth gauge from the aluminum stock to the pipe O.D. over its length. the very same part also doubled as a rear triangle T tool; we'd hold it against the head tube and seat tube and site it against the inside area of the rear tips. this was how things were monitored. for both the front tubes and the rear triangle, when something was off, we had near to no issues showing it who's boss. as mentioned above, i used this procedure on at least the first 600 frames with RS stickers.

how was head tube twist checked? we'd hold the frame up, site behind the seat tube and head tube while looking at a white wall, and slowly hone in on the space showing as the tubes would seemingly overlap each other when we moved the frame or our eyes. the punch line is that whatever the results of the eyeballing were, we never developed a way to change them.

[anon.]

FWIW, my system (such as it is) goes like this:

- Roll fresh tubes on a-table, mark the apex of the bow.
- Tack ST to BB shell (I do a single tack at the rear and a smiley face in the front where the DT overlaps) using calipers to make sure there's an equal bit of shell sticking out top and bottom.
- Check the ST alignment along one side, nudge it straight if it needs it, then check the other side. Note offset for later so I can adjust via facing.
- Put the rest of the frame together, tack on the table, let cool.
- Check front end alignment Taylor Bros-style.
- Check front end on the a-table by putting it back in the blocks.
- Tack CS #1 on the table, checking the inside face of the DO all around (with my stuff, 193mm is the magic number).
- Nudge CS #1 if it needs it.
- Set up CS #2 using The One True Wheel and the park FAG. Tack.
- FIx up the CSs and DOs using the FAG and the FFG
- Let the SSs fall where they may, trying to keep them in plane with one another but not stressing about it too much.

This works for me because I trust my 'fixture' (tube blocks w/ 5" standoff sitting on a full size drawing sitting on the a-table) and because I've learned to force myself to not rush through the process. Every once in a while a DO needs to get filed a smidge to make sure the wheel is sitting straight, but most of the time the bikes are straight enough without much fussing. I've tried a bunch of different build sequences over the last year and this is the one that i've settled on. Ideally, I'd like to get a CS mitering fixture but I'm not sure about the ROI at this point.

[steve garro]

FWIW, my system (such as it is) goes like this:

and bottom.
- Check the ST alignment along one side, nudge it straight if it needs it, then check the other side. Note offset for later so I can adjust via facing.
- Let the SSs fall where they may, trying to keep them in plane with one another but not stressing about it too much.

I totally disagree with these steps, esp. #1. - Garro.

[anon.]

Well, my thinking is that i'd rather have the ST square to the BB all the way down its length and adjust the .25 mm or whatever through facing rather than cold set a misalignment into the first joint of the frame. I'm talking >1mm adjustments at this point. I'm always looking to improve the way I go about things, so any insight past knowing you disagree would be appreciated.

As far as the SSs go, I don't really have much in the way of options. I don't build with a jig and can't tack the frame as a single piece (which is your method, iirc). If the frame up until that point is straight, the SSs will come out straight.

[steve garro]

Well, my thinking is that i'd rather have the ST square to the BB all the way down its length and adjust the .25 mm or whatever through facing rather than cold set a misalignment into the first joint of the frame. I'm talking >1mm adjustments at this point. I'm always looking to improve the way I go about things, so any insight past knowing you disagree would be appreciated.

Yeah - no worries. The ST is the "spine" of the bike - get it straight, nuts-on straight.
Don't face to mimic this - it's two different things, Facing & ST alignment.
Maybe {I have been thinking about just the right setup for this myself} build a dedicated BB/ST sub-fixture........Vulture has a great/simple one.
Also, you are taking in any discrepencies in the tubing into the mix by checking both faces. I read off the driveside face, all the time. YRMV.

Seatstays Make The Man. That's my personal view & the 1st thing I look at on frames, because I think builders think people won't notice that one is a little higher, ect........
I think everyone needs their own seatstay treatment as a kind of signature, but again, that's opinion.
We *could* get into the differences in Asymmetry v. Straight.... - Garro.

[steve garro]

If the frame up until that point is straight, the SSs will come out straight.

maybe straight ones....... - Garro.

[steve garro]

Maybe {I have been thinking about just the right setup for this myself} build a dedicated BB/ST sub-fixture........Vulture has a great/simple one.
- Garro.

here is one. bb to seat tube fixture | Flickr - Photo Sharing!

[anon.]

Cheers, Steve - I think we're on the same page. 100% in agreement about the ST/BB being the most important piece of the puzzle. I didn't mean to sound laissez-faire about the process, just accepting that this is not a digital process and nothing's ever going to come out 100% bang-on to the thousandth of a mm - you can't get tolerances in a frame that is built out of parts that aren't made to even remotely the same tolerances. Like everyone else, I try to get the miters as close as possible, the set up as close as possible, and everything else as close as possible.

w/r/t a ST-BB fixture, I sort of have one in that I trust the table, blocks and post I use to be straight. In action:

[anon.]

here is one. bb to seat tube fixture | Flickr - Photo Sharing!

I think I've seen pictures of a similar get-up in UBI class pictures - pretty similar in practice to how I roll, but you don't have to lean sideways. Before I got the BB post, I just did it upside down in a vise with a piece of round bar in the shell and checked everything with a machinist's square and calipers.

[steve garro]

Cheers, Steve - I think we're on the same page. 100% in agreement about the ST/BB being the most important piece of the puzzle. I didn't mean to sound laissez-faire about the process, just accepting that this is not a digital process and nothing's ever going to come out 100% bang-on to the thousandth of a mm - you can't get tolerances in a frame that is built out of parts that aren't made to even remotely the same tolerances. Like everyone else, I try to get the miters as close as possible, the set up as close as possible, and everything else as close as possible.

w/r/t a ST-BB fixture, I sort of have one in that I trust the table, blocks and post I use to be straight. In action:

I totally concur. The only thing is that you are fighting gravity in a 1-way battle there. Not dismissing your technique, just an observation - Garro. PS - I like your drawings! I give mine to the clients, they dig them.

[EnginCycles]

This is my surface plate:



I have added info and notes on the actual flickr page here.

-Drew

[Archibald]

This is my surface plate:



I have added info and notes on the actual flickr page here.

-Drew

Drew, did that plate have divots in it that weren't able to be ground out or is something else going on with its surface? What I'm talking about is mostly in the near right corner, but it looks like it's elsewhere too.