Yankee Bicycle
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WANTED: Yankee Bicycle posted by: Carl Gromatzky
on 11/28/2001 at 10:47:05 PM
A friend of mine in Providence, RI found an old bicycle manufactured by "Yankee
Bicycles" of Chicago IL recently.
It has an extremely unique braking a gear system. We are looking for a new brake
cable. The bike has rear brakes only. The cable is a solid FLAT aluminum (about
3')with a stranded cable attached to the flat cable via a welded bolt. The
stranded cable then is bracketed in traditional fashion up to a single right hand
brake.
The flat portion of the cable is extended around an extension of the rear rim
allowing the cable to float freely while riding. When the brake is applied, the
flat cable clamps down on the extension of the rim to stop the bike.
I don't even want to begin to describe the gear mechanism!!
Has anyone ever heard of a braking system like this before, and know where we
can purchase a new cable?
http://www.halfbakery.com/idea/Continuously_20variable_20bike_20transmission
http://www.freethought-forum.com/forum/showthread.php?p=381538
There was a bicycle made in New England somewhere called The Yankee Bicycle. It featured an chain-driven automatic variable speed drive, as speed increased it changed the gear ratios. As you slowed going up a hill, the gear ratios increased, maintaining the same pedal effort or reducing it. They had other innovations on this bicycle such as the Kevlar-wrapped cable rim brake on the back wheel which actually became more efficient when wet, a lower frame to make it easier to mount, and high handlebars for comfort. The company was bought out by Nordic Track, which then marketed the bicycle as a Nordic Track bicycle. Apparently it didn't sell and is nowhere to be found now. I never heard of there being any quality problems with that bicycle, as is the case with Nordic Track products in general.
From E-Bay archive:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=230235555088
There was a bike transmission design that came out quite a few years ago, before the Internet. The "Yankee Bicycle" featured something called a "rim band brake", as well as an automatic transmission. I found a link partially describing this bike, of which one which was found in the trash, so you can be sure they were actually produced (search for the word "Yankee" at the linked page).
Anyway, at the rear wheel of this bike was a single sprocket, and a lever with a spring and a chain-tensioning sprocket.
The automatic transmission stuff was entirely part of the front sprocket. This mechanism was featured in an old article in Popular Science, and at the time I thought it was really cool, and wanted one, and so studied it pretty thoroughly, and can, I think, describe it reasonably accurately here.
Part of the front sprocket assembly consisted of a circular plate with six radial slots (straight from center toward rim), and an adjacent circular plate with six spiraling slots. I think there may actually have been two of the radial-slots plates, with the spiral-slots plate sandwiched between them, but it could just as easily work the other way, a radial-slots plate sandwiched between two spiral-slots plates. In this description I will assume the first sandwich.
When oriented properly, you will see six smallish holes through the three plates, where the spiral slots cross the radial slots. Rotating the spiral-slots plate, while holding the radial-slots plates stationary, causes the holes to move from the center toward the rim of the circular plates (and vice-versa if the spiral-slots plate is rotated the other way). The overall assembly keeps the two radial-slots plates fixed relative to each other, and a strong torsion spring is attached to the spiral-slots plate. The "default" position for the six holes is near the rim of the circle.
Through the six holes are placed six small axles, and on those axles are six small sprockets. If you wanted to draw a picture, just do a simple hexagon with a modest circle at each corner, to represent these sprockets. At least two of these sprockets (at opposite corners of the hexagon) must be ratcheted, so they can only rotate one way. The bicycle drive chain goes around the outer parts of some of the six sprockets, as well as the rear-wheel sprocket and chain-tensioner, of course. Note that the "size" of the "front sprocket" of this bicycle is the result of the chain going around the outside of several of those six small sprockets.
Are you ready to roll? When you apply force to the pedals, you will be applying twisting/torsional force to the radial-slots plate. The six axles and sprockets are carried along, and the chain starts to transmit power to the rear wheel (because of the ratchets). If there is little resistance, the rear wheel will start to rotate, and the bike will move.
f there is resistance, however, the spiral-slots plate will start to twist, tightening up the torsion spring. This twisting motion will cause the six sprocket axles, thanks to the radial-slots plates, to move toward the center of the circular plates, toward the center of the pedal axle. This effectively shrinks the overall diameter of the front sprocket! And slack in the chain, as that happens, is taken up by the rear tensioner.
The smaller-diameter sprocket assembly means that your "gear ratio" has changed, you have "increased mechanical advantage" in applying turning force to the rear wheel. And when the resistance diminishes, that caused the front sprockets to move closer together, the torsion spring smoothly (as in "continuously variable:) restores them to the rim of the assembly, once again maximizing the overall gear ratio. Vernon, Aug 21 2007
I wrote this to someone several years ago:
I bought my Yankee new [the one now for sale/trade here] and have ridden it a lot. Sort of retired it now. Popular Science mag had a feature article about it in August 1991.
I have some info on it as I kept everything. Instruction book, order form, retrofit of new brake cable..see below...The company/bicycle was later sold to Nordic Trac company and then fizzled out. Likely too advanced and 'strange' for the average American 'consumer'. ..and not hot enough for the serious bike riding enthusiast.
Seems to have dropped from sight. I never see anything about the Yankee. Should be a nice collector's bike for someone. I want to trade mine for a good regular bike. the Yankee is a great riding bike but I'm afraid to ride the Yankee because it has really irreplaceable parts all over it. That is I would ride it but want to avoid any damage.
Also [IMPORTANT] the glue holding the Kevlar sleeve around the original steel cable on the brake cable was glued only on a part, on one end of the Kevlar sleeve. If and when it fails, the Kevlar sleve itself will rumple up on the cable and jam in the rear wheel brake groove and immediately cause a total wheel stop and skid. While this is happening, there is no way to "release" the brake. This happened to me. Good that I was riding slowly at the time.... I hate to think of what would have happened in traffic or going down that very fast hill near my home. The company sent a replacement cable as a safety retrofit to those they knew who had the bike. The replacement cable had the Kevlar glued for the total length of the Kevlar sleeve, not just on the end as it was with the original cable that had failed Kevlar. The cable did not fail, the problem was with too little glue on the Kevlar. If you don't have the updated all-glued Kevlar cable, I'd say don't ride it.Just find a bike collector and sell / trade it. Don't ride it. if it is in really nice shape, you ought to get at least 600 for it, my opinion, from a serious collector who would want it. It is a rare high-tech bicycle.
Let me know what happens...