THE "SINGLE SPEED" CRANK/RING SET

Most vintage road bicycles were equipped with dual, or even triple ring crank sets.  A "Single Speed" bike needs only one crank ring and with this need comes a choice.  Purchase a track crank set at considerable expense or modify the existing one, for little or no cash outlay at all.  Since I do my best to build bicycles on a budget without sacrificing safety or dependability, I usually choose to modify a dual ring set to one of single ring design.

Modifying the crank set for "Single Speed" application is really not the least bit difficult to do.  The tools are simple and inexpensive to purchase.  So too is the conversion procedure.  And the results, in my mind, are pretty good and certainly presentable on just about any converted "Single Speed" that I have run across so far.

Some crank sets can be converted quite easily while others cannot.  I always go with tapered alloy cranks and alloy rings.  Steel is too heavy a material and far more difficult to work with, when compared to aluminum.  And the tapered crank is far more versatile and available than its predecessor, the cottered crank. Once material has been considered, turn your attention to crank and ring design.  Some crank sets have the big ring integral with the crank spokes.  In other words, the ring cannot be removed without permanently altering the crank set itself.  The second style does allow for both rings to be removed.  With this style, only the big or small ring need be modified.  The integrity of the crank itself goes untouched.

Now either design will work just fine and end up looking very nice, however; some crank designs do not lend themselves well to conversion.  Consider these two crank sets.  The crank set on the left is a great candidate for "Single Speed" conversion.  The one on the right would be a nightmare for the average person to rework.  Not only that, but the crank on the right also has steel rings.  Trying to convert such a crank set would likely end in failure.

Once you have decided on a crank set to convert you need to accept that part of the set will be altered permanently.  Once the first cut is made, there is no going back.  but there is lots of room for error built into the procedure and, as was the case in learning how to paint a bicycle frame set with a brush, tons of opportunity to learn and improve as you go.  That said, let's get on with converting a dual ring crank set to one of "Single Speed" design.

In this exercise we will be working with the "both rings removable" style of crank and it will be necessary to cut one ring or the other.  Generally, I prefer to use the smaller of the two rings with hopes of having 40 - 42 teeth.  This front ring tooth count, when driving a 16 tooth single cog freewheel works well for a guy like me.  Gear ratio is choice is, of course, a personal thing but a good place to start from is the 42/16 combination.

If the smaller of the two rings is to be retained, then the spokes of the big ring will have to be cut free.  The result will be five tab washers, each counter bored to fit a speciality fastener - the crank ring bolt.  It is necessary to use these tab washers to help located the rings in the proper position once the crank/ring assembly is complete.

Before making any cuts, do your best to determine exactly what you want to keep.  Install the big ring only on the crank and ensure that all crank ring bolts are in place.  The bolts might not be too tight but they will help to properly locate the big ring on the crank arm spokes as you etch target marks.

With the big ring installed on the crank arm spokes, carefully etch five lines.  Etch as close to the end of the spoke as possible.  These etched marks will become targets to work towards.  DO NOT CUT TO THESE ETCHED MARKS!  Leave about an eighth of an inch or so clearance.  You will file to each target mark, not cut.  Said another way, cutting to the target mark is dangerous.  Too much cut and the piece is ruined!  Leave plenty of clearance!

When rough cutting the tab washers, I simple mark a line with a felt pen and ensure that the pen line, the line I intend to cut to, does not come too close to the target line.  With the big ring clamped in place, use a fine tooth hacksaw blade to cut completely along the penned mark.  Set the washer aside and repeat the process for each of the other four tab washers.  You now have a set of rough cut tab washers that need to be finished off in an effort to ensure safety and impart pleasing aesthetics.

Using a couple of different small files, slowly and with care, file away metal until the etch mark is met.  By going slow and watching what you are doing you will be able to work right up to the etched mark.  Doing so will create a tab washer that looks as good as it works.

When filing the tab washers to the target etching, file two at a time.  Fit two washers together with a proper chain ring bolt.  Loosely secure the pair and then do your best to line up unaltered surfaces.  Once lined up, snug up tightly and file the pair together.  Doing this will help to establish uniformity of all five washers, making for a more aesthetically pleasing crank set.

With the tab washers cut and filed to the target position, spend a bit more time and round off any obvious little eyesores.  Blend each surface into the one following it.  Round corners off a bit more if you feel that doing so would improve the appearance.  Try to keep the filed edge square to the face of the tab washer face.  Finally, slightly round the square edges just enough to take away any sharpness.  The last thing you want is five knife edges going round and round right next to your foot.

Once the tab washers have been cut and polished to your satisfaction, it is time to assemble the newly converted crank set.  Once again, take your time ensuring that each crank ring bolt is clean and as free of oxidation as you can get it.  The little brass brush that is used for chrome cleaning is a great tool to use when cleaning up the crank ring bolts.  As you fit the crank ring bolts into position be prepared for the now individual tab washers to move around slightly.  This is normal and all that you need to do is ensure that the washers look uniform once all five are secured into place.  This might take a wee bit of fiddling but you will get them all mounted just right if you take your time.

The result, a nicely cleaned of and converted "Single Speed" crank and ring set that is ready to install along with all of the other components selected for your "Single Speed" conversion project.  There are many different ways to finish off a converted crank set.  Time spent hand polishing the cranks and rings will pay off big time in the aesthetics department.  The Bianchi cranks used to demonstrate some of these procedural steps could use a bit more hand polishing.  If you look closely, you can still see a wee bit of the laser etching on the face of the crank arm.  A bit more time with the soft brass brush will make fairly short work of the lazered mark, leaving a gleaming crank set that will look just great on your "Single Speed" road bicycle.

NEXT - ASSEMBLING THE "SS" FRAME SET