Instructables

Two-speed bike without a gear shifter

Featured
This is the first version of a bicycle where when you pedal forward the bike moves forward and when you pedal backward the bike still moves forward, but in a different gear. No gear shifter or derailleur is necessary. Although the basic mechanism works in this version, it is not practical for an actual bicycle because of the high torques involved.
 
Remove these adsRemove these ads by Signing Up

Step 1: Designing the hub

Simplified schematic of hub. Roller chain transfers torque to the sproket. During forward pedaling, the roller-pin clutch on the left catches and rotates with the sproket. Torque is also transfered through the gears (not shown) in the gear box to the "anti-sprocket," which moves in the opposite direction of the sprocket. During backward pedaling, the clutch on the right catches and rotates with the anti-sprocket. Regardless of pedaling direction, one clutch catches while the other is free to rotate. By connecting the clutches to the spokes of the wheel, we have a wheel that moves forward regardless of pedaling direction.

Step 2: Machining the parts

Unfortunately, I don't have pictures of the machining process. Everything was relatively simple to machine using just a lathe and a mill.

Step 3: The finished product


Step 4: Problems with current design

The current design is fatally flawed in multiple ways. 1. All the reaction torque during back-pedalling is transferred through the axel causing it to snap in two. 2. Increasing spoke tension pushes the spoke hubs into the gear box which increases friction. 3. The gear box should be replaced by a planetary gear system.
try buying a titaneum( i think thats thats how its spelled )bolt its 3 or 4 times stronger then steel(and pricer too!)
Titanium is lighter as well..
thats why its used in military aircraft.
its a 'rareish, space-age' metal which is why its so pricey..
titanium itself is far from rare, smelting it is expensive, but can be done at home. the biggest problem would be the tools, most tools you probably have, would cause titanium to oxidise really fast.
jls622545 years ago
schwinn built a bike with this type of gear set up in the 1960,s
olmon jls622542 years ago
The Schwinn two speed rear hub shifted by 'slightly' back pedaling, but you still pedaled forward for motivation in both gears.
hockeyteeth7 years ago
That took some juevos to ride with that axle! I never would have ridden it... Why don't you try using an axle intended for punishing conditions - like a bmx axle? Also, would you be able to coast with that hub? I'm having difficulty understanding all facets of this monstrosity's inner-workings, haha.
mje7 years ago
The Bendix two-speed automatic hub was made from 1952 to 1961. It looked like a stock coaster brake, except for the three red bands. Backpedaling shifted from one ratio to another.
dikron7 years ago
Ok found one but more like a street bike.http://utica.craigslist.org/bik/220524171.html
Dikron
dikron7 years ago
I didn't have one, but I wanted one. Around 1960 they made two speed bikes that I rode here in california. The gear system was housed in the hub the size of eeen's bike. You just pedaled back a hair and then forward (low to high) .They were great I used to recognize them by two or three painted bands around the hub. I used to check out everyones bikes for that. Looking now on the net for one for my son.It didn't have the extra gear ahead of the hub like eeen's. They were cool, I'm sure huffy, shwinn, or a common bike company maded them. Dikron
In the late 70ies there was a two gear planet gear hub from Fichtel&Sachs, which was to be shifted by back pedaling. The name was "Torpedo Duomatic".

You start to pedal, then turn the pedals a few degrees backwards (not too much as otherwise back pedaling brakes kick in) hear a tiny "click" noise, and when you pedal on you will notice that you are on the higher gear.

Here is a link of a german site listing all planetary gear rear hubs, please choose your favourite online translator: http://www.3gang.de/3-gang/2-gang_naben_duomatic_seite4.htm

There was also a "Torpedo Automatic" which "shifted itself" by means of a clutch driven by centrifugal force. http://www.3gang.de/3-gang/2-gang_naben_automatic_seite3.htm

If you are lucky you can find one here in Germany or UK/B/NL, mostly on commuter bikes or those very heavy "folding" bikes in orange or golden bronce colours from the 70ies.
_soapy_8 years ago
I've ridden a bike with backwards pedal gearing, and it isn't that easy, plus it feels really weird. Customer acceptance might be hard to get. It's a neat idea, but I don't think a bike is the best place for it to go. Perhaps in a wave power generator machine, where the tide goes in and out, and the waves up and down, but the dynamo should always spin the same way?
2Short _soapy_8 years ago
I ride a bike with backward-low-gear/forward-high-gear pedal setup, of the "Hirondelle" design mentioned above by Eeen. I'm not sure why you say it isn't easy; everyone who tries my bike can ride pedaling backward (often while laughing hysterically) with no problem. Spinning backward or out-of-the-saddle sprinting take a little getting used to. "Customer acceptance might be hard to get." If this is being done for commercial purposes, it's about a century late :) But as oportunity for tinkering just to be different, I highly reccomend it.
Prometheus8 years ago
Erm...why not just lace-up a 3-speed hub available from a bike at your local thrift-store? While I like the creativeness of the idea, that axle in the pic above looks scary, and I'd dare not ride on it. That axle is simply not anywhere near large enough to handle typical loads you would expect on a bike, tensile strength aside. Not practical is right, but keep working on it, you may get something practical from this idea yet. Simply put for all who posted above me, the axle is not even close to the gauge sufficient for bicycle-duty. That is mild steel, at the least hi-tensile steel, 4 gauges heavier, is what you need to depend on. I'd suggest taking this idea and making it a part of an electric bike, rather than applying cyclist-torque to this mechanism. And is that a 28T cog on that wheel? I'd look into another means at this point.
Not to be nit picky... But shear strength is more important than tensile strength when it comes to bike axles.... I do agree that it looks a bit on the small side though :P In a botched HPV repair - we used 3/4" threaded rod to support a delta trike (bike alone weighed around 60lbs). Much better than the solid 1" alum 'beam' that was used (and bent) - yeah, we were pissed at the guy that did those calculations...
I think that with the hole drilled through it like that, the tensile strength of the lower side and the compression (or deformation) strength of the upper side will be the important ones. I would certainly be wary of such a big through hole in such a thin bit of steel, especially if it got a little hot whilst being drilled!
jtobako8 years ago
why not put the gearing inside the gear cluster? then you wouldn't have to drill threw the axel. why not use a washer welded to the head of the pin and put a nut on both sides or forget the single axel and use two bolts that screw into the gearbox.
Darcsky8 years ago
This is an awesome idea. Have you tried using a stonger axel material? From the picture it looks like a standard piece of threaded rod, maybe you would have better luck with a piece of hot rolled steel with only the ends threaded and a pin press fit for the gearbox fixation. Alternatively you could try using a higher grade of threaded rod.
argon (author) 8 years ago
Wow, thanks Eeen. That is a cool design. I had thought of something similar using two chains (one normal, and one in a figure eight) instead of the one with a winding path. I still think a completely encapsulated hub design would be ideal though.
Eeen8 years ago
There is a more simple and elegant method of doing this that has been in existance since the 1920's and probably earlier.
See http://lyxus.net/pb for details.
rs1.jpg
ryan Eeen8 years ago
Eeen, this looks great. can you post more info?
skookum8 years ago
Alternately, it may be possible to use a sailboat winch gearbox. Rugged and similar two-speed, bidirectional operation.
skookum8 years ago
Alternately, it may be possible to use a sailboat winch gearbox. Rugged and similar two-speed, bidirectional operation.