Monday, April 30, 2012

A personal masterpiece: Raleigh Sprite 3-speed conversion with retro lights!

This is it, my most finicky and obsessive bike project thus far: a 3-speed conversion of a 1980s Raleigh Sprite with LED-equipped vintage lampset. My Motobecane city bike project was considerably higher end, but it wasn't done by my hands and, crucially, doesn't have a lighting system.  It's been a full year in the making (I ordered the wheelset on April 27, 2011), but most of the time was spent developing the LED lighting system.  First, a bit of history:

Canadian-made Raleigh Sprites are quite a common sight on the streets of Toronto. The most popular colour seems to be black, but there are gorgeous candy apple red ones that I see quite often as well.  The ladies Sprite had a true double-toptube Mixte frameset, very elegant and in contrast to the single sloping toptube of earlier Raleigh ladies models.  The original configuration of the 1980s Sprites was a 5-speed complete with matching fenders and a classic Pletscher CS rack.  This particular Sprite was my mom's, purchased sometime in the early-mid 1980s.  She didn't ride it much and it spent most of its life in the musty basement of an old stone shed.  It had some regular use sometime in the late-nineties to early-naughts by a family friend, who treated it to its only tune up.  Sometime in the last decade the front wheel got smushed and it became officially derelict.  I've had my eye on it for a couple of years as a new bike to build up for my wife.

Last spring, I pulled it out of the damp basement, stripped it of its old wheels, handlebars, brake levers, pedals and saddle, gave the frame a good cleaning and polished up the Shimano Tourney brakeset, SR Stem and Silstar crank arms with Simichrome.  I then set to work with converting it to a 3-speed.  I'm particularly fond of the Raleigh Superbe, and it is the Superbe's 3-speed/Dynohub combination that served as my inspiration for upgrading this Sprite.

First, I ordered a wheel set from Longleaf Bicycles, who provide a very high quality and inexpensive custom wheel building service.  A Sturmey Archer SRF3 three-speed hub and Sanyo H27 dynamo hub are laced to Velo Orange 36 hole PBP rims.  The only problem is that the original wheels were 27", causing a problem with brake reach for the handsome Shimano Tourney callipers on the rear wheel; they barely had enough reach with the original wheel diameter.  Not wanting to have to purchase new longer reach brakes, I had my first part CNC-machined: a drop bolt to lower the rear brake so that its arms have enough reach:

Brake drop bolt for mixte frame

It works nearly perfectly and is very discrete:

Inconspicuous drop bolt

The only problem is that it takes up a bit of space that the fender could have used, resulting in a really tight fit. A future revision would have beveled the edge that comes into contact with the fender.

With the brake reach problem sorted, I went about setting up the handlebars (VO Tourist) with the 3-speed trigger shifter and brake levers. I tried the original levers but they didn't fit with the shifter. I had a pair of ridiculously expensive Paul Love Levers lying around from another project that fit perfectly:

3-speed trigger shifter with Paul Love Levers

The new Sturmey Archer 3-speed hubs feel and shift much better than the originals. I was able to run the shifter cables using the original bosses and did away with the plastic cover that comes with the new hubs:

The last thing to do was set up the lights. After developing a standlight circuit, I had to figure out how to mount a LED on a heat sink and fit it all in the housing of an original Sturmey Archer headlamp and develop a LED bulb for the taillight.  I discovered that the original Raleigh lamp bracket didn't work with the SR stem, so had a new longer bracket fabricated and chromed:

I spent an evening mounting the lights and wiring them up.  The matching taillight for the Sturmey Archer headlight was stolen, so I had to settle for a vintage Luxor taillight, which polished up to a near chrome-like finish.  It's a surprisingly good looking match considering the Luxor is meant for a different era and style of cycling.  In anticipation of using an original Sturmey Archer taillight, I made a wedge-based LED bulb, complete with copper heat sink.  However, I decided to save that set for another project. The Luxor uses a threaded bulb, so I just made up an E10 copper-topped LED bulb with a red Cree XP-E.  The XP-E, driven at ~500mA from the dynamo, is extremely bright, easily rivalling the current batch of boutique super bright battery taillights.

Luxor tailight takes an LED E10 threaded bulb

Here are a few more photos. The complete set is on Flickr.

Now it's just a matter of putting some miles on the bike (ideally at night!) to see what comes loose and to work out any gremlins in the lighting system.  Inevitably, there will be some...


Anonymous said...

I'm probably breaking some rule of etiquette here by going off-topic, but, WOW! that is one gorgeous bicycle! You are totally justified in calling it a masterpiece.

I wanted to rebuild a mixte for my sister and found an old Raleigh Sprite. Upon searching the web for info, I came across your blog. This is my inspiration for updating the old green Sprite I found.

Thank you for the great photos, and congratulations on such excellent results!

Anonymous said...

I've also added a modern high-output LED to a NOS Sturmey-Archer headlamp and taillamp set. I did not upgrade the magnets. I wired the headlamp and taillamp anti-parallel, with no other circuit modifications. This gives a strobe effect at each end - probably excellent for being seen, although the headlight is still a little dim for lighting the road. (The red LED in the taillamp may actually be a bit too bright!)

My LED adaptor for the headlamp is a three-piece assembly of aluminum, not solid copper. I'm sure it doesn't sink or dissipate heat as well as yours; but the bike is used for only short rides around town, and it's done well for a couple years now.

A comment on headlamp optics: You're right, there doesn't seem to be an off-the-shelf way to throw the lumens properly onto the road. A kludge I came up with was to use a tiny bit of shiny aluminum sheet as a sort of "eyebrow" over the LED itself. Trial and error allowed me to set its angle so most of the light that would have been wasted upward at least makes it onto the road somewhere. Also, I fixed a thin bit of translucent (nearly transparent) plastic in front of the LED. Its image is, I believe, what gets projected by the convex center of the SA headlamp lens. These features seemed to improve the distribution of the light, although since it's a one-off attempt, I couldn't do and A vs B test to be sure.

All this is on a custom Reynolds 531 frame I got for cheap in a junk shop, and fitted with a NOS SA 3 speed, old Brooks leather saddle, etc. Almost all the parts came out of my junk boxes, so very cheap. It's a classy-looking, fun bike.

So, you're not alone in experimenting with these things! Nice work!