Two-speed Bike Without a Gear Shifter

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Introduction: Two-speed Bike Without a Gear Shifter

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.

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.

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22 Comments

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.

schwinn built a bike with this type of gear set up in the 1960,s

The Schwinn two speed rear hub shifted by 'slightly' back pedaling, but you still pedaled forward for motivation in both gears.

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.

user

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.

Ok found one but more like a street bike.http://utica.craigslist.org/bik/220524171.html
Dikron

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.