Monday, May 30, 2005

Photos to Follow

I worked on every day of this long holiday weekend. Despite this, I had time to get a little work done in the shop. No photos yet, but soon.

The first major task was to mount the left chain stay to the bottom bracket on Sarah's bike. I choose to work off my drawings and pin the joint. What made this difficult was that I had to bend the BB socket down 8.5 degrees. This is, after all, a kids bike on 20" wheels.

I wasn't too sure about doing this, and I'm still not entirely sure that the main shell of the BB didn't get bent (next time I'll have to get some old BB cups and mount them during the bending process). I began by elongating the socket with the die grinder. I didn't want to use this as my primary method, but did want things to be a little loose to begin. I mounted the BB in my vice between to pieces of 3/8" plywood and tightened it down. Then I put the stay into the socket and pulled down.

I was concerned about bending the stay instead of the socket, but needn't have been. The end inside the BB shell hit the top of the shell and bent down some, but that part needed to come off anyway. So, I worked the stay out, trimmed back the inside end, and set it back in place to check against the drawing. A couple of more smaller pulls and I had it made. Then I drilled the BB shell for two pins, close to 180 degrees apart, fluxed everything up, fit the stay back in, adjusted to the drawing, drilled the stay for the pin, fluxed a pin and set it lightly. I checked against the picture, made some adjustments, drilled for the second pin, fluxed the pin and set it. I checked against the drawing one more time, clamped the piece in my stand, and proceeded to braze it up with brass. I got a clear visual of the brass pulling through and the outer joint was pretty clean so I left it to cool.

When I checked against the drawing, I was spot on. I'm a little surprised by that one.

After this, I started work on a practice fork. Actually, if it comes out well it'll go on my current bike (12 year old trek w/ 3 main tubes in carbon and the rest including the fork in aluminum). I'm sure it's way overbuilt, but I've never fully trusted the aluminum fork. Forks are one of those things that I just don't think should be made of aluminum.

Anyway, I have a Walter (which I suspect is a Long Shin or Everest) crown. It's the ultimate cheater's crown. The rake is built in (7 degrees), the brake-holes are dimpled, there's an internal seat for the steering tube, it's hollow so the fork legs don't need a vent hole, and there is a hole on the underside which can be tapped for a fender or rack and which serves as an additional vent hole. Meanwhile I have some nice but problematic fork tips from Bringheli. They are stainless and look very nice. The fit internally to the tube and have a platform on the end above which a central stub projects. So, it's very easy to set a coil of silver on the end and push the tip into the tube for brazing.

There's just one thing, the tips are pretty big around. I trimmed the fork legs from the bottom exclusively and I still had to grind down the bore of the tip to get it into the fork. This is a slightly tedious process of checking and fitting and checking and fitting. It would probably be a great use for a lathe.

The tips have one other nice feature. On the inner side, there is a hole drilled through the bevel (or arch) between the tip itself and the body that goes up into the the fork leg. This hole goes all the way through the stub at the back end of the tip. So, there is no need to drill a lower vent hole either.

Assuming that one fits the tips correctly to the tubes, it should be a simple matter of checking the leg lengths for equality before brazing the legs to the crown.

Life, however, is not without its challenges. I'm not sure if the crown is straight. Its hard to tell because it doesn't have any straight surfaces on it. I tried laying the steerer on v-blocks, squaring the face of the fork into a vertical plane, and then squaring against the bottom tips of the fork leg sockets. This shows a discrepancy. However, I'm not sure that the crown is that precisely and symmetrically made. I think I'm going to have to face the crown and try to square against the face while holding the steerer in the v-blocks.

Meanwhile, a dry assembly of the fork w/ a wheel indicated that the legs were equal length. So, I thought I'd install the tips. All went well with this process until things were cooled down. Then I found:
  • 2 very small dimples in the fill between the leg and tip on one side.
  • 2 tips twisted relative to the leg, one slightly and one majorly, but both significantly.

This was after I'd finished filling down the first joint. I guess I'll have to reheat the joints and try to slip them into their proper position. First I'm trying to thing of some kind of marking I can use to sight whether the tip is straight or not.

I would have continued working tonight to get the tips right, but I've finally run through my first tank of Oxygen. I'll have to get a refill this week. Meanwhile, I have time to consider how to mark the tip orientation.

Stay tuned for more adventures.

Wednesday, May 25, 2005

Falling Behind Schedule

Well, sometimes life gets in the way of work. Anyhow, I've managed to squeeze some framebuilding in since the last post but haven't had time for posting. Even this post will be without photos for the present - they'll come later.

I started Sarah's frame over from the beginning. After heating up the headtube joint it pulled apart easily saving the headtube and it's lug. Having already cut the BB off, the old downtube is now designated for use as the seattube (which is the same diameter as, but shorter than, the downtube).

After cleaning off the lug, I fit the new downtube to the headtube. Because the lug fit is now looser, I went with brass filler. All in all, I was satisfied with the way I flowed the brass, less mess and I could see it come out the far side of the lug all the way around. I'm a little concerned about over cooking the tubes, however, and will have to figure out a test for this - Freddy can probably tell me what to look for.

After mitering tubes, I fit the BB to the downtube and brazed it up again using LFBrass. I left the tube long in the BB so I could see the flow of brass come through. Then the same with the seattube. My available BB (cheap stamped type) has T-shaped windows in the sockets. Three of the windows came out perfectly clean - that is you can see the brass color where it flowed down through the window, but they have crisp edges all the way around. One window came out OK, but there's a spot where a little excess brass got into the window. I don't know if I have quite the right tool to clean this out, but we'll see.

While the flow of brass appears good throughout the BB, and the windows and edges look good, I'm again concerned about overheating. I work without shades to be able to look at the colors, but based on my color/temp chart, things aren't getting that hot. Also, the lug and tube never get hot enough to melt the rod without application of the flame, suggesting that they're below the melting temperature of the rod. But, call me paranoid, I'm just not sure. In part because there was a point where the flux wouldn't flow anymore. I was trying to draw the excess brass out of the one window with heat. It just wouldn't flow - which is what made me think the flux was cooked and that heat may have been excessive.

Anyway, I sat the head tube and seat tube each on a pair of v-blocks. Alignment was not perfect. Using the head tube as my baseline (using a flat table for my surface plate) the seattube rises 20/1000ths at the top (right side of frame down). So, here's another place where I experience don't knows. To wit, I don't know:
  • If 20/1000ths is significant.
  • If the tube warped, or if I did one of my joints crooked.
  • How to get this straight.

I'm playing with shimming the seat tube blocks to get the tube center the same height off of the table as the (larger diameter) head tube. Then I can use a square to test the BB to the plane of the headtube. I'm also working out a way to clamp the BB to the table top. The BB had been nicely faced prior to brazing, and is narrow enough that I'd like not to face it again. So, this seems like a good second test of the BB plane to the headtube.

If there is a significant alignment issue between the BB and the headtube, I'll just call this practice and cut the joints apart. Otherwise, I don't think a six-year old can feel a seat that's mis-aligned by 20/1000ths or less (the actual seat height will start about 10cm below the end of the rough seattube).

With this decision in place, I've gone ahead and fit and brazed the (mixte) toptube. The toptube is lugged at the front and filleted at the back. Both of these joints came out better than prior efforts with brass. The headtube came out clean and quick and I'm not worried about over heating. The fillet built up big - there's plenty of filing to do, but I will be able to produce nice radii for this angle.

Preliminary checking of the BB looks good, but more checking needs doing before attaching chainstays. Meanwhile, I started the process of fitting the stays in order to practice attaching dropouts, or in this case forks - single speed style because I want to use a geared hub.

The chainstays will be proportionately long - they're straight and need to accommodate a 1.5" diameter tire. This, of course, should also help the bike track straight. Small bikes turn so quickly that this shouldn't be a problem.

Freddy got my respirator and pin kit to me. Yea on both - highly recommended. Anyhow, the angle of the stays means that the fork (dropout) is at a distinct angle to the stay when viewed from above. I cut the left stay to approximate length, then cut the slots with a hacksaw and bent the tabs back so that they snapped off easily. While it was no problem to align the fork into the stay, it was loose enough to not trust gravity while brazing. So I used the first of Freddy's pins. Very cool. His supplied drills cut very well (better than my Hanson's but that set is a bit old and may be dull). Everything got a good coat of flux, especially the inside of the stay, then a tap of the hammer to set the pin and everything was lined up nicely.

At the risk of sounding like a broken record, this was my best brass braze yet. It should be noted that the stay is fairly large around when the fork enters it and I wanted a good bond between the two, lots of brass went inside. This likely will prevent me from slipping the fork the way that Paterik describes to adjust the joint. This will drive the use of some kind of fixture to make sure that the stays and forks are in perfect alignment before brazing them to the BB.

Anyhow, why did I like this braze? Well, I filled the stay with brass easily without seeming to overheat. Recently I saw a cameo from a Paterik video. I've been moving my torch around but basically keeping it in contact with the tubes. In the video, Tim moves his torch around - then pulls it away from the metal for a moment - then returns to heating. I tried this method and it has some real advantages. 1) when the flame is away, its much easier to see how the joint is coming (maybe I can start to use shades and protect my eyes), and how the brass is flowing. 2) brass can be applied with the flame, then the flame is pulled away while adjusting one's hold on the rod - meaning less heat on the joint when its not needed. 3) its easy to combine this method with using the side of the flame to keep the brass in the flames cone without pointing the cone at the tubing - again controlling the heat while melting the brass.

Netting this out, I was able to better manage the brass to stay viscous rather than having melt to water - and the brass did a much better job of staying where I wanted it. I was also able to melt some of the brass for filling the stay from above. The stay and already placed brass were hot, but I could keep the cone of the flame and the rod 3/8ths to 1/2 inch above this and have it melt into the already deposited brass - rather than placing coagulated drops of brass on a coagulated mass of brass. So when filling started, there where no holes - yea!!!! Also, having filled the stay, it was easy to draw brass, using heat, down the edge of the joint between the stay and the fork - and this went cleanly - no slopping of brass around. Finally, the slot was too long on the bottom - probably very bad form, but the hole had to be filled. It was easy to keep the brass viscous and bridge the gap & tie it back into the end of the fork. Up until now, brass seemed like a necessary evil - but this time it was fun to use. All of this may seem pretty trivial to anyone reading this site, but for me it was a major accomplishment and I'm still enjoying that.

Well, that's about it for now. The description is now current with my work. I'll try to get some photo's posted on the site this week/weekend to show the work.

PS The post office is still no help regarding my BB taps. Renaissance has indicated that they get me some info to use, but they're mid-move across the Atlantic - so I expect this to be a long slow process. Ugh.

Monday, May 02, 2005

Post Office Problems

It turns out that Renaissance sent me three packages via the post office. The first to arrive was the last sent. I dutifully went to the Post Office for package two with my delivery notice - they handed me a package and took my receipt. Ok so far. But when I open the package - it only has the BB facing tool. So, I look at the notes from Renaissance and sure enough - two package for the facer and the tapper. And they were sent at the same time. So I'm still missing a package. Its not clear to me if the Post Office gave me package three in which case number two is still missing, or it they gave me number two and number three has never arrived. There's no way for me to check that now because they have the receipt with the tracking number. Luckily I saved the packages (with their tracking numbers).

I've shot an email to Renaissance for help identifying the tracking number for the BB tapper, but haven't heard yet. I guess I'll try again tomorrow. I hope the package shows up soon because I could use the tappers very soon.

Its clear that the Post Office is great with mail. But packages....I don't think so. The idea that they can (and apparently do) regularly return packages from a route (for example no one was home to sign for them) and have these packages go backout in the mail stream (to be later returned to the local post office) seems like a process nightmare. How can this weakness exist and not be fixed? How much does it cost them to accidentally ship packages out of the local office? There's handling, fuel costs, dealing with angry customers at the front window, processing through the various sorting machines, etceteras. One would hope that this sort of thing couldn't easily happen, especially if they want to compete with the DHL/FedEx/UPSs of the world.

Ya know, here's a problem G.W.Bush could sink his teeth into. Wish he would.

Sunday, May 01, 2005

Bottom Bracket Follow Up

Well, after Freddy pointed out to me that Allstate 11 isn't meant to be used in a socketed joint I asked if I could heat up the BB and pull the tube out. He responded that #11 has "....Eutectic qualities..." and wouldn't likely come apart.

I had to look up Eutectic. couldn't help so I went to Wikipedia. I will summarize here my layman's understanding - so if you're an engineer or scientist, don't hold me to a precision definition.

Eutectics appear to generally be made of two substances - in the case of metals they are a type of alloy. One characteristic is that in their liquid state, the parts blend but in their solid state they tend to separate. If there is too much of one element, it will start to harden and sort of precipitate out as the liquid cools. If there is too much of the other element, then this one is the one to first harden come out of suspension. However, there is a balance point between the elements where solidification can maintain the blend of elements. Further, at this blend, the melting point is lower than for either of the elements individually.

So, what may happen is that in the course of brazing some separation of elements can occur. If so, this should mean that re-melting the filler requires a significantly higher temperature - which would be difficult and could damage the tube and BB.

Because of all these factors, I decided to cut the tube out of the BB. I'll reheat the headtube joint and remove the tube which will be shortened and used for the seattube. Meanwhile, the blank from which I was going to make the seattube will be now used to provide the downtube. Net of this, I'm only sacrificing the BB.

I've cut it up and found that the #11 did flow through the joint well. Because the BB is of pressed steel, it has large radii where the spigots join the cylinder of the BB. The #11 didn't fill these (which is as I expected), but did a great job of filling all of the normal gaps. Fred says it is possible to use #11 this way, but the characteristics that allow it to be controlled for a fillet (that it can work in a plastic state that isn't totally liquid) make it less than ideal for the socketed joints.

I'm pleased that the #11 drew through the joint so well. It makes me increasingly confident of my ability to make a sound joint. And the setback of time gives me the opportunity to try better changing the DT angle on another BB.

Some pictures will be posted, probably later in the week.

Meanwhile, I'm waiting for some of Freddy's special aerospace rod. Its supposed to work much like #11 but at lower temperatures. Should be fun.

By for now.

Loutish Lugs

I'm trying to build a kiddy bike for the kids. I wanted to adjust the lower head lug and the angle between the downtube and seattube spigots on the bottom bracket.

I'm better equipped for this now, having found a small anvil and some heavy (very heavy) pipe I can clamp in the vise as an anvil. Hence it should be possible to restore bent lugs to roundness.

The BB shell went into the vice between to pieces of 1/2 inch ply (to protect the faces). I got out some drifts and a 32 oz ball peen hammer and went after it. It moved some, but not very much, and not as much as the design called for. That said, the design had the BB on the low side so on real damage is done if it has to be a little higher. I just hope to figure out the right way to shift these joints. Maybe its just a matter of patience and continuing to pound. Maybe it would help if the drift had a different shape head (mine is round, perhaps oblong would help). I need to get another length of very heavy tubing so one can go into the downtube spigot and one in the seattube spigot and try levering things around.

Anyway, things are laying out pretty nicely to the drawing with the exception of BB height and that doesn't seem like a big problem. The next big challenge will be the fork. I wanted to use a crown with built in rake, but it isn't really wide enough. The wider crown doesn't have any rake. So, I'm going to have to build a bender and rake the fork legs. Oh-boy.

That's all for now.

Bottom Bracket Blues

Last night I tried brazing up a downtube to a bottom bracket. I was hoping that it would be the basis for a kiddy bike. That was probably ambitious because I haven't done a bottom bracket before, plus I went with Allstate 11 bronze and I haven't used bronze before on a lugged joint. Oh well, sometimes you just have to jump into the deep water and swim.

My problem is, it felt like plenty of rod was used (up to my handhold on one rod), but I didn't see a lot come out on the bottom bracket side. And, I couldn't get more to flow into the joint (probably had used up the flux at that point). I know the joint got hot - the BB was glowing. And, the tube got warmed up, but didn't see to over heat.

So, I have an inquiry into Freddy Parr. He'll be able to best diagnose whether I should just cut the BB up, or keep going.

I should have taken pictures as I went, but didn't. I will post some soon of the effort to date.


Freddy got back to me. Allstate 11 is only for fillet joints. ah-ha :) So, on to the next step.