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Old 04-23-2014, 12:36 AM
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BarelyAWake BarelyAWake is offline
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Join Date: Jul 2009
Location: Maine
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Default Re: Getting Aero - Speed Gains

Originally Posted by The_Aleman View Post
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.
I had just posted this, I just can't agree a "25% reduction in power required to maintain 20mph" is moot;

Originally Posted by BarelyAWake View Post

It's the "HP required" percentile difference that's simply stunning and as that's only at 20mph, remembering wind resistance is exponential (double the speed, wind resistance increases four times etc.).

Touring 100% @ 20mph
Recumbent 75% @ 20mph
Equals a 25% reduction in power required to maintain 20mph... & that's even unfaired, just rider position.

There's precious few engine mods that'll boast such massive differences

Originally Posted by The_Aleman View Post
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.
Be it a result of pedaling, aeromods or gearing tweaks - faster is faster & I'm failing to understand why areomods in particular have drawn your ire. Builds utilizing engines grossly in excess of legal parameters can be a hazard to our activity and in many ways I share your concerns, despite stickers & claims otherwise, overly large displacement engines are an obvious violation of size and/or power restrictions (state dependent). Yet, there is no region I'm aware of that prohibits aeromods, or pedaling for that matter. What states have a speed restriction it's up to the operator to obey, the occasional "not capable in excess of" a bureaucratic impossibility.
Originally Posted by The_Aleman View Post
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.
"The end result may be similar in that both have increased speed and fuel efficiency..." - is the bit I meant.

"...but at legal motor-assisted bicycle speeds, aerodynamics play a very small part in overall speed and efficiency" - is the bit I disagree with, as previously exampled.

Originally Posted by The_Aleman View Post
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.
You've presumed I haven't availed myself of my build's pedal gearing to assist, odd given I've spent so much effort extolling the virtues of efficiency, torque & reduction of fuel consumption - or even that we're running the exact same engine type & displacement. I'll spare you the details of my build's specifics save to say, I've 21 gears available to both the engine and my pedal drive so yes, I do have a range appropriate for my needs.

Originally Posted by The_Aleman View Post
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!
This is where the misunderstanding stems I suspect, you've presumed the thread title 'Getting Aero - Speed Gains' to be referencing "speed" you don't approve of, most likely in excess of your stated "36MPH" top speed... yet this is a presumption based on "aerodynamic mods aren't really that important" below that speed, which if you'll forgive me is flawed in both presumptions.

Importance and speed both are comparative, relative terms, even 20mph "fast" to pedalists, I consider 25% a considerable percentage, important enough to me to choose a recumbent over another upright anyway.

Point being, you've jumped into a thread casting aspersions based on presumptions with only a vague "You know who you be" in lieu of any credible context... highly unfortunate as you and I share similar interests & build dynamics, lowracer & I happily sharing primarily HPV aero data, lowracer offering numerous examples of his pedal-only recumbents & velomobiles. I would have thought you would have accepted, if not embraced this legal method of increasing efficiency, reducing the HP required for even legal speeds, or whatever speed you think appropriate - even contributed as you say, you've done this before. Interestingly, aside from a mention of human powered records you're the only one that's made any top speed claims to date in this thread.

I fear you're mistaking advocates for enemies, even when they could be allies - I would strongly suggest reevaluating the context of your complaints and finding a more suitable venue, of which I'm sure you're keenly aware of in both propensity & popularity, even in this forum if not this thread. I personally would like very much to cease quibbling over semantics and resume the sharing the technological details of aerodynamics & construction techniques, the results of which like any other - up to the operator to utilize in whatever fashion they deem fit.
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