Monday, July 30, 2012

Equipment - Tsunami 1.1 (Ream/face)

The only real issue I've had with my frames has been the BB30 shell. It's a press-fit bottom bracket shell, and as such it needs to be exactly right. The spec states it should be 41.96mm in diameter on the inside (internal diameter or ID). This allows the 42 mm bearing to squeeze in there with a perfect balance of snugness and looseness. If it's too loose it'll creak (most likely) or move a bit. If it's too tight the bearings get squeezed. You may not think a BB30 can be squeezed but trust me, they can.

In the old days of steel and aluminum all frames had to be prepped before they were built. The brazing and welding would warp and distort the metal, leaving behind imperfect frames. Okay, they might have been pretty or whatever but you had no way of knowing if the bottom bracket shell's outside faces were parallel or if the threads were any good. Likewise the head tube surfaces were suspect, both in the inside roundness as well as the flat edges the headset cups sat against.

The problem with having unfinished surfaces is that the different halves of the bottom bracket or headset may not be in line with each other. The frame's owner will always have weird wear or adjustment problems with both areas.

Shimano addressed the bottom bracket issue a long time ago by selling a bottom bracket cartridge, a one piece insert that had its own "shell" if you will. The problem was that these things were heavy, and the current crop of bottom brackets returned to the "left side - right side" construction type of days past. This, of course, means that frame prep counts again.

It's easier for most shops than it used to be. With the advent of mass produced aluminum and carbon frames shops and suppliers have slowly lost the art of frame prepping. The big aluminum manufacturers will get a whole frame, sit it on a jig, and using a monster machine, quickly ream the insides of the bottom bracket shell and the head tube, then face the outside edges. This assures that the bottom bracket and headset will work smoothly on the assembled bike.

With carbon it's even easier - the frame molds are so precise that the manufacturers pull out a frame that's already "finished". They don't need to do anything else because it's all done.

Finally component manufacturers have done their best to enable their bits to work on roughly finished frames. I think of the Soviet approach to military machines compared to the American one. An old joke goes something like this:
An American pilot makes fun of his Soviet counterpart's coarse jet fighter. The Soviet responds, "Well, your planes are like fine ladies' watches. They are beautiful and work well but they are very delicate. Our watches are like Mickey Mouse watches. They tell time and if something happens and they stop you just shake the watch and it works again."

I really identified with this since at the time my mom had a precious watch that seemed very fragile, and 12 year old me had a yellow Mickey Mouse watch that was basically indestructible, even when I dragged the watch face along the sidewalk.

Nowadays there's a lot less adjustment (i.e. fine stuff) and a lot more "just replace the cartridge" (i.e. coarse stuff).

I say all this because a small aluminum frame builder (and steel too I suppose) needs to finish the bearing interface surfaces - the head tube and, if applicable, the BB30 bottom bracket shell.

(Regular bottom brackets get screwed into the bottom bracket shell, and many shops still have the tools necessary to chase/cut such threads. BB30 is nice because it allows a wider diameter bottom bracket axle and ultimately a very light crank/BB unit, but the problem is that very few shops are prepared to service the frame part of a BB30 bike.)

When I built my (then orange) Tsunami, I didn't have the luxury of a bike shop or even the big tools of a shop. I built it in a hurry before I headed out to California for a training camp and I took every shortcut possible. Therefore I never dealt with finishing the frame, either the bottom bracket or even the headset. Because of this I've had to deal with the resulting issues since - a headset that always had to be a bit too tight and a bottom bracket that was very, very tight.

In fact, in that SoCal training camp, I coasted down one of the numerous short but reasonably steep downhills at about 40 mph, shifted into the 39x23 or so, and spun the pedals. Since I wasn't pedaling fast enough to engage the freehub body I was still coasting even though I was pedaling. This meant that any resistance in the drivetrain (chain, derailleur pulleys, pedal bearings, and BB bearings) would result in a power reading on the SRM.

Unlike 99% of my riding time, I stared intently at the SRM as I spun down the hill. I varied the pedal speed, from about 60 to 90 to about 150 rpm. I saw about a watt of resistance for every 10 rpm (which I just realized now, since my benchmark numbers were 6, 9, and 15 watts).

Although it takes only 20 extra watts to see me off the back of a crit, I really focused on the sprint. And 15 watts (at most - if I was pedaling 150 rpm I was doing something wrong) is a very, very small part of the 1500+ watts I could hit at the time.

Therefore I ignored it.

The bearings got crunchy quickly, and I went through a few sets in the year I rode the orange frame. I got the black frame next and spent some time filing the shell by hand. Hopefully I didn't ruin it but on this frame I only saw about 4 watts, at most, doing the same kind of test. This seemed acceptable to me, even if my cranks don't turn more than a half revolution at a time if I try to spin it as hard as I can.

With the UsedToBeOrangeAndNowRed frame back, I decided that I'd invest in the tools necessary to ream and face the two bearing surfaces. With the help of the Expo Wheelmen's shop sponsor Manchester Cycle I went ahead and bought the business end of the BB30 reamer and headset cutting tools. (The cutting edges are what cost money - they sit in handles and Manchester Cycle has the appropriate handles for the cutters.)

I should point out the the FSA BB30 reamer alone lists for $400 (and that's without the handles!). The headset cutting tools were a bit more reasonable, but still, it's not a small thing. Neither are big sellers since most shops work on those aforementioned "fit and finished" carbon or aluminum frames.

All this took some time and I have to thank Bob at Manchester Cycle for all his patient work. Luckily he's a car nut too and used his 20 ton press to finish off the job (I'll explain below). Suffice it to say that I'm looking forward to building up this frame.

 BB30 shell, reamed, left side.
Bob reported that significant material came out of both sides.

 The headtube with the Crank Bros cups pressed in.
This is a simple result for a nightmare process.

 Seat tube - honed in prep for the seat post.
This is the cheapest of the tools needed for prepping a frame.

 Another BB30 shot, of the right side.

I mentioned a nightmare process? Well, I didn't know this, but when I jury rigged the headset press and jammed the cups into the frame, I was really, really lucky. The headset has an incredibly low stack height (i.e. it's not tall), the main reason for me purchasing it. It's also very light, a bonus (I'd have bought it even if it was heavier - I was only concerned with getting the shortest height headset within my budget.)

Well the reason the headset is so light is that the cups are extremely thin. They're so thin that if you try and press them in without a special thing holding the outside of the cup, the cup breaks.

 Special tool that surrounds the headset cup to prevent it from breaking.
Bob used a 20 ton press to press in the cups -  Press means lots of pressure, very easy to modulate.

This is an oops. Crank Bros sent a replacement. Thank you.

Now that the frame has its main bearing points finished, the seat tube honed, it's ready for the detail prep and then assembly.

Detail prep in this case means mounting the replaceable rear derailleur, cleaning out the cable housing anchor stops, and chasing the threads on the downtube barrel adjuster mounts (they got painted over/through).

I'll need to put the headset crown race on the new fork, make sure everything seems right, then proceed with the assembly. I won't be using new parts except for consumables, I'll just be rebuilding with basically the same stuff (which is currently sitting around my bike workshop). It'll be the Record/Chorus 10s stuff, a Cannondale SI SRM (my backup crankset will go on this frame), and a few experimental replacement parts.

Once the red frame is up and running I'm going to have Bob do the black frame - the reaming, facing, and honing. Yes, I already asked him if he'd do it all again (the black frame has the same headset). Yes, he agreed.

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