RE: [CR]WTB: Campy Triple [and how to make one]


Example: Production Builders:Teledyne
From: "Mark Bulgier" <mark@bulgier.net>
To: 'Paulie Davis' <paulieflt@hotmail.com>, classicrendezvous@bikelist.org
Subject: RE: [CR]WTB: Campy Triple [and how to make one]
Date: Fri, 8 Feb 2002 22:53:15 -0800


Paulie wrote:
>
> Anybody want to part with a Campy triple (170 or smaller)?
> It doesn't have to be in beautiful condition, just halfway
> affordable. A private reply would be appreciated, especially
> by my knees.

Paulie, this isn't to talk you out of the Campy triple, but don't overlook the Stronglight 93 which is a lot more common and usually real cheap. It goes down to 38, vs. the Campy's 36, so it's almost as easy on the knees. The long chainring bolts that go through all 3 chainrings to make it a triple aren't so common these days, but I know someone on the list will have those - maybe I have some to spare (I'd have to root around a bit). Or you can run it as, say, a 38-50 double.

The Stronglight 99 goes to really low gears, 28 tooth minimum, but is harder to find. In the mid 70s to early 80s I used to convert Campy cranks to touring triples by drilling and tapping the 5 spider arms at the right diameter to bolt on a Stronglight 99 inner ring, using the Campy special adaptor bolts (#818). (See below if you want a description of how to do this). This made a real expensive crank that wasn't really any better than the Stronglight, but hey, it was Campy, need I say more?

Of course any number of modern (shudder!) cranks will get the gears you want, but I assume this is for a bike that wants classic stuff.

Mark Bulgier Seattle, Wa USA

P.S. - To convert a Campy or similar racing crank to a triple with a Stronglight 99 inner ring...

Short version: Bolt the Campy crank to a Stronglight 99, drill through the 99 c-ring bolts and on through the Campy spider, tap the holes.

Long version:

Skills you need: probably you should have drilled and tapped metal before, but if you're willing to try it for the first time on a Campy crank, well who am I to stand in the way of a madman?

Parts and tools you need: -a drill press. (I really don't think this can be done accurately enough with a hand drill) -a Stronglight 99 right crank as the drilling template. (Which leads to the question: if you already have a nice touring triple crank, why are you doing this? If you don't know the answer, quit now!) (The Stronglight crank is not harmed by this procedure.) -5 Campy #818 bolts. Last I heard Renaissance Cycles had 'em, and cheap too. They take normal track chainring bolts, practically any brand. -a Stronglight 99 inner ring, duh! Not impossible to find yet, I bought some last year. -several 3/16" drill bits, new or freshly sharpened. Center drills are best, see below, but you'd still need one or more regular 3/16" bits. -a metal cutting countersink - typically about 1/2" diameter, 1/4" shank, 90 degree included angle, though none of these are critical - just don't try to use one made for wood. -cutting oil, safety glasses. -a 6mm x 1 tap (a very common size), and a tap handle to fit it. -a 1/2" bolt or piece of all-thread, with nuts and washers, long enough to go through both cranks at the spindle hole. A carriage bolt is best, as the square head will keep it from turning. -5 normal single-ring (track style) c-ring bolts that are somewhat expendable - BMX maybe? (They aren't completely ruined by drilling through, but they'll be a tiny bit weaker, and they'll rust.) Double bolts can work too, you'll just need more spacer washers. -some washers (5, 10, 15? depends on how thick) with a 10mm hole. The c-ring spacers for Stronglight 99 triples and the like are ideal, but a big box of assorted junk washers will often suffice - or make a trip to the store.

OK, bolt the expendable c-ring bolts to the Stronglight crank, placing washers over the nuts (female part) as necessary so they tighten up against the crank and don't spin or wobble. If stacking up multiple generic junk washers to get the thickness you need, only the one just under the head of the nut needs to have an accurate size hole, the others can have a larger hole. You may have to flatten one side of the washer to a "D" shape to clear the shelf on the crank where the c-ring would normally sit. (A hand file and vise does the job, or hold the washer in locking pliers and grind with a bench grinder or belt sander.) (If you don't follow my description here just from reading it, don't worry, you'll see what I mean when you have the stuff in your hands.)

Now bolt the two cranks together at the spindle hole with your 1/2" bolt. The small end of the tapered hole is amazingly close to 1/2". If the hole is too small, consider enlarging it a tiny bit (won't hurt the spindle fit, as the spindle doesn't touch there), or filing down the bolt a tad. A very snug fit is best, no slop allowed, shim with cut-up pop can if necessary, but I haven't found it necessary. Pass the bolt through the Campy crank first, from the outside in, so that the head is inside the recess where the normal crank remover or crank bolt would go. You may have to grind/file the head down so it fits in the recess with none sticking out. The bolt then goes through the Stronglight crank, from the inside out, with the nut and washer in its recess. It's allowed to stick up out of the recess on the Stronglight, or even be entirely outside the recess with a big ol' washer covering the recess.

Don't tighten the bolt too tight - you'll notice that it springs (flexes) the spider arms of both cranks if it's too tight. But kinda tight. ;^)

Put a piece of paper between the face of the Campy crank and the drill press table to protect the finish. If the table has ugly scars that need more protection than a piece of paper, consider flat filing and/or sanding them down before going further; they'll throw off the accuracy as well as scratching the crank.

Make a "spider spacer": Take a piece of metal, wood, plastic, anything, and saw/grind/file/whittle it down 'til it's just the right size to fit under the Campy spider arm, at the end where the two larger c-rings bolt on, and hold it up the right height from the drill press table. Take some time to make this spacer well, it'll partly define the accuracy of the whole job.

You can just hold the crank and spacer with one hand, while pulling the drill press lever down with the other hand to drill.

The first time you drill through the Stronglight c-ring bolts, you'll take a little metal off the bolts; how much depends on the brand. It's important for them to not spin at this point; make sure they're tight. Then after the drill passes through the bolt, you're ready to drill the Campy crank.

A word (or several hundred) about drills: The very best to use here (at least to start the hole) is a #2 center drill. These have a smooth, unfluted 3/16" shaft, with a little 5/64" drill point just at the end, and a brief taper between the two diameters that cuts like a countersink. The smaller drill point cuts quickly with very little "wander", and makes a pilot hole that the larger drill will happily follow. The trick is to get a center drill that's long enough to go through both cranks - most center drills are too short. Many sources exist for this perfect drill, but your local hardware store may not have it. It might be worth placing an order to a tool supply mail-order catalog operation or web merchant to get it - buy a few while you're at it. Some sources might call it a "combined drill and countersink" but I believe "center drill" is more correct.

Here's one place to buy: http://www.mscdirect.com/MSCCatLookup2.process?MSCProdID=01044247 They are $5.30 each, 4" long.

If you want to use a regular 3/16" drill, make sure it's new or nearly so - very sharp. A split point sharpening job may be good here - I'm not a machinist so I can't say for sure, but they look good. The "point" of being sharp is to reduce the cutting force required. Even though it's only aluminum, it's good hard aluminum! Excess pressure will make the spider arm flex and/or make the arm rock on the table, and make the drill more likely to wander, any of which can blow your accuracy.

Maybe your machinist friend can give the perfect speed (RPMs), but I've always just used a speed I'd call "medium" - I don't think it's too critical. Use very light cutting oil - kerosene is good (called paraffin in England I believe), or use a formulation made for aluminum. Regular cutting oil made for steel is probably OK too. Use safety glasses, and be aware that if the drill catches, the crank will try to spin around - you might want to hold it with a leather glove on the holding hand. Press down hard enough that you're making a chip - it's bad if the bit is just spinning around not cutting. Not too hard though.

If you start with a center drill as I suggest, you'll have to switch to a regular 3/16" after making the pilot hole - don't go past the top of the tapered part.

After you've made the first hole, drop one of your extra drill bits through the Stronglight and Campy cranks to keep those holes aligned. Handle the assembly gingerly at this point, remembering that you didn't tighten that 1/2" bolt too tight, and it's essential that the two cranks don't move relative to one another until all 5 holes are drilled. Clean the chips off the table before drilling another - they'll blow your accuracy.

Place your spacer under the next spider arm, drill another hole, drop another drill bit through to align, and move on. When all 5 holes are drilled, take the 1/2" bolt out - we're done with the Stronglight crank.

Getting the tap started straight is the hardest part of the job, but here's a technique that I've found to give adequate results: Chuck the bare tap (no handle) in the drill chuck. Don't start the motor, just bring the spindle down with the press handle, and apply a steady down pressure while turning the chuck by hand. You're just trying to start the tap enough that it'll stay straight when you take the tap out of the chuck, attach the tap handle, and tap the rest of the way "freehand". Getting the tap *more* started is safer than less started, so drive it in as far as you can before taking it out of the chuck. Tap a quarter-turn or so forward, then back up to break off the chip, then go forward again, adding more cutting oil frequently.

When all 5 holes are tapped, don't go putting the #818 bolts in yet - it's important to countersink the holes. Look closely at the #818 bolts, where the 6mm thread ends before the larger-diameter part. See how that will stop it from threading in all the way? I've seen people do this crank project only to have the bolts break in no time, because they didn't countersink the holes.

Lay the crank face down on the drill press table again (wiping the chips off first), piece of paper to protect the finish, put your spacer under a spider arm, and bring the spinning countersink down on a hole with light pressure, watching carefully to see how much you're taking off. A bit more than the minimum needed is your goal - make sure the #818 bolt will thread all the way in, but don't countersink much more than you need. It's a surprisingly large chamfer needed though (I was surprised anyway) - over 1mm, maybe 2mm.

The countersink may flatten or burr the first thread of the hole, making it not "catch" on the #818, so you may need to run the tap through again to chase the thread before testing with the #818. Look very carefully, make sure the #818 is tight against the spider arm all the way around - hold it up to a strong light source (no pun intended) to make sure it's "home"

When all 5 #818 bolts are in, let's have a drumroll please, now we get to find out if you were precise and accurate enough - will all 5 holes in the c-ring match up with the #818 bolts? (Mine always did, but I had a nice shop, and lots of practice.)

If one or more of them are a little out, it may be possible to spring the ring to fit, but don't be too discouraged if you have to file the hole in the c-ring with a round file. If the head of the bolt then won't fit in the counterbore of the c-ring, you can file the bolt head down a bit, or better, "mill" the counterbore over a tad with an appropriate metal cutting burr in a Dremel, a die-grinder or similar rotary tool. Soon as it gets a little dirty no one will be the wiser.

To anyone who has read this far - you are a very strange person. I like that!

-M