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Old 04-22-2014, 10:51 AM
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The_Aleman The_Aleman is offline
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Join Date: Jul 2008
Location: el People's Republik de Kalifornistan
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Default Re: Getting Aero - Speed Gains

Originally Posted by BarelyAWake View Post
Speed and efficiency are related, but not the same. Reducing load in any fashion can result in a faster build - or one that requires less to achieve similar results.

"Speed" is also relative - if someone had a motorized bike with a 30cc helper, they may be interested in areomods to go "faster" and that faster would very likely be on par with a 49cc build, without areomods.
Of course it's relative, and aero plays a huge part with low-power engines. But at legal speeds (<30), aero doesn't play as much a part as it does at above legal speeds (>30). You likely know this. The faster you go, the more aerodynamics matter. At the speed MaBs are legally limited to, with the fact we have a gas or electric motor attached, makes the point of having fairings and/or lycra/spandex rather moot for everyday riding.

You've quoted "pedaling harder is the cheapest speed upgrade" and while I agree to an extent, it too presumes speed is the outcome...
Understand this: it's open to many interpretations. Regardless of semantics, "speed" can be understood as acceleration, top speed, or cruise rate. I made that quote over a year ago when it seemed to me many people were putting increasingly powerful engines on their bikes while making pedals more of a "backup" thing to use only when starting their engine, running out of gas, or increasingly, just to be "legally" compliant on what is actually the illegal motorcycle they have built. People spending money on the "assist" part of their bicycle and making it the primary propulsion while neglecting what is truly the primary propulsion unit of a bicycle: chevrolegs. Not pedaling on a bicycle is completely silly to me - engine or not. Regardless of what I think tho, pedaling a bicycle produces more torque than many drivetrains people are bolting to their bicycles, yet they do so so they don't have to pedal anymore. I don't know about you but I see a lot of irony in that. When people are spending money to go faster on their motor-assisted bicycle, pedaling harder is still the cheapest speed upgrade. This is not my opinion, this is a fact. Most of us have no problem eating, but many here have issues with pedaling their bicycle.

but it's only one application, not the only application. To carry the example areomods to a chassis can be seen like pedal assisting to a motor, should you choose less work or go faster, it's your choice.
Again, this is your interpretation of my somewhat tongue-in-cheek signature statement. And I disagree with you about aeromods: they are _nothing_ like pedal assisting a motor. Not at all. Pedaling is adding power, aerodynamics reduce drag. Aerodynamics do not increase power. The end result may be similar in that both have increased speed and fuel efficiency, but at legal motor-assisted bicycle speeds, aerodynamics play a very small part in overall speed and efficiency compared to simply pedaling or adding more power. Sure a headwind will skew that in favor of being slippery in the wind, but again, pedal torque costs nothing but the rider's own energy. We all likely know the faster you go the more aero matters, but legally we are limited to speeds that aero does not matter so much.

I wouldn't have chosen a 49cc four stroke hybrid if my interests were pure speed, I could have halved the weight with three times the horsepower had I chosen a two stroke... a clear illustration that efficiency & speed aren't the same. I chose a four stroke for it's fuel consumption rate and torque, my build a comfy cruiser heavy hauler, trailer in tow. If I choose to aeromod, it'd be with the same goals as the entire build had - comfort and efficiency.
I can show you many instances where increased speed directly results in increased efficiency, but they all involve processors or certain jet engines. Apples and oranges here of course, but let us focus on your statement where you say you chose a 4-stroke: fuel consumption rate and torque. If you have geared your tadpole to have usable pedal gears at any reasonable cruising speed, you will reduce fuel consumption rate and increase torque by simply pedaling. Not only that, but you can also increase acceleration and top speed when you simply pedal. Potentially moreso than a standard bicycle even, because your tadpole has a seating configuration that results in higher average pedal torque when seated than a standard upright bicyclist can attain. Maybe less peak, as you can't stand on your pedals, but definitely higher average.

Now that you've given your ride's example, I'll give mine: my ride is set up so that peak pedal torque is at the same RPM as peak engine torque - in each gear. Peak pedal "horsepower" is at the same RPM as peak engine horsepower. My bike with me on it is neither light (305lbs with a full fuel tank) nor particularly aerodynamic (I'm 6'4" 225, wear jeans and sit upright), but it's capable of 0-30MPH in under 5 seconds when I pedal. It can cruise all day long at it's maximum legal speed. Without pedaling, it would be a lot slower in acceleration, although top speed wouldn't differ much (36MPH). Granted, if I had aerodynamic modifications I'd likely be able to increase my top speed and cruise speed against a headwind, but I rarely go over 30MPH anyway.

I'm not against aerodynamics or anything, I know first-hand they play a _huge_ part on bicycles. If anything, one will notice quickly any difference he/she makes in decreasing drag when it comes to bicycles. The first headwind you fight will make you a believer let alone speeds above 40MPH. It's just that if you have an assist engine on your bicycle, have pedalable gears, and aren't interested in exceeding the speed limit, then aerodynamic mods aren't really that important. Pedaling is still cheaper!
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