The Efficiency of Bike Engines

By Deane Barker on August 29, 2006

Golden Eagle Bike Engine: Neat article about a little engine for your bike.

I eventually found a 4-stroke motor and belt drive kit from Golden Eagle Bike Engines that weighs very little, operates quietly, and gets me to work and back for about 45 cents a day in fuel. […]

Top speed with 26×1.95 dirt tires is about 25mph on flat pavement, or 23mph on flat dirt. Wind, inclines, sand, and other factors significantly impact the top speed, but it will even typically maintain 18mph under most typical adverse conditions. I know from prior experience with the same bicycle that I can sprint it up to 24mph without the engine, so having the engine on is equivalent to being able to sprint all the time.

These are a good thing, even though purists probably abhor them. The simple fact is that biking everywhere under your own power is just not feasible for a lot of people.

I know very few people who can show up at work sweaty and smelling like a goat, and I know fewer people who have the facilities or organizational wherewithal to delay their shower until after they get to work. This is a good option with a lot of benefits that brings fuel-efficiency into reach for a lot more people.

What I like is that the power used to push the source of the power around — the “meta power,” if you will — is very small. The engine is essentially just pushing…well, you.

My mountain bike weighs about 20% of my body weight, so that means that it weighs 16% of the combination of me and it. This means that only 16% of this engine’s power would be lost to pushing the bike itself.

Compare this to my Nissan Altima. It weighs 1,100% of my weight, or 92% of the combination of me and it (I’m a big guy…). So 92% of the engine’s power is being spent just pushing itself around. With numbers like that, I’m practically an afterthought. What a huge waste.

I’ll never forget a secretary that used to work at my firm. She weighed about 80 pounds soaking wet, and she always rode around alone in her GMC Tahoe XL. Fully 98.7% of that Tahoe’s energy was spent moving itself.

I question the sanity of moving three tons of rubber, steel, and glass for the sake of 80 pounds of anything.

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  1. My thoughts have been going down the same path, and I’m considering something very similar, but leaning toward electric power. There are some very nice kits available, like the GoHub, with the motor built into the front wheel hub. Cost is about the same as the Golden Eagle, and gives you 20mph with about 30-mile range.

    One needs to tread carefully in these waters though; there is some garishly geeky company in that realm.

  2. I love new technology, but I would also like to save money on gas and not contributing to pollution. Instead of a car, I use something called a Trikke, that needs no pushing, no pedaling, just rock and roll with this technology called “cambering”. I can easily hit 20mph and go more than 30 miles if I want to, and at the same time get fit. If you have never rode one, it is great!

    Don’t get me wrong, love cars and all that, but I try to save money, gas, and not to pollute the air, trying to get more vehicles that are enviro-friendly. Plus, Trikke folds up and goes in your trunk.

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