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Old 02-28-19, 11:41 AM
  #28  
Leisesturm
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Originally Posted by Ericoschmitt View Post
I know a smaller rear wheel won't change much aerodynamics, but the builder said the seat is fixed to the frame at 25 degrees, so a smaller wheel lowers this angle, then making the rider more aero.
I figured out that that was probably what he meant a few hours later. And, yeah, he's right, but the 700 rear wheel just 'looks right'. You obviously care about looks. I do too. Aesthetics matter almost as much as performance. And how much faster would you be with a few more degrees of recline? I also have to ask how much faster do you think you will be on a recumbent at all? I am not ANY faster on my highracer than on my roadbike. Somewhat slower actually. You are probably a lot younger than, I am with better reflexes, and will adapt to the recumbent position better than I have, but I am telling you now, unless you are on a track or some kind of closed course situation, you will likely only be as fast on a naked recumbent as you are on a standard bike.

The main reason non-competitive riders use recumbents is comfort! You said you don't care that much for comfort, you are about speed. When I want to go fast on just two wheels I ride a motorcycle. In the United States recumbent trikes outsell recumbent bikes by a HUUGE margin. Recumbent bikes fall over way too easily and older riders cannot take the risk. Competitive riders on race worthy recumbents ARE faster than roadies. They are not dramatically faster! Just a few miles per hour faster until you get out the carbon fiber and wind tunnel tested shells and and. The ultimate in linear motion is the sliding seat rowing sequence. This is impractical for a two wheel recumbent, but there are fixed and sliding seat rowing trikes (maybe bikes too, who knows). 40 ish strokes per minute is a very high stroke rate to maintain and the same is true for linear foot action. You can't do the 120 rpm craziness that you can do with pedal cranks because the pedals absorb some of the effort of decelerating your lower leg and getting it moving in the opposite direction. In rowing and linear motion, the mechanism does not help as much in returning energy for the return stroke.

The simplest linear (or rowing) action will be very much more complex than a conventional chain drivetrain. Simple works. It works very well. You have to work very, very hard to beat simple and efficient. It isn't usually worth the effort. I would have little to say about it if you were able to prove me wrong by building a prototype and putting a Youtube video of it online. If you have to sub-contract fabrication to people with specialized knowledge of welding or metalworking or framebuilding you are dead in the water. It won't be worth it. I approached a talented metalworker in my area to collaborate on an idea I had and he didn't want to have anything to do with it. Framebuilders are much braver than metalworkers. They know their creations will be used by humans in possible risky ways. I don't know how they protect themselves legally but they seem to have figured it out. In Brazil there probably aren't as many lawyers making anyone who builds something for someone else nervous about liability but you still have to weight the cost of their labor vs what you get in return. TL;DR: Buy that sweet lowracer you linked to (700C rear) learn to ride it, and enjoy riding it. Do that for as long as you possibly can.

Oh, the short cranks ... so here's the thing about that. The way you put it "when you shorten cranks you lower the gear to keep pedal speed the same" is not quite right. You don't lower the gear to keep pedal speed the same, you lower the gear to keep the perceived effort the same. Pedal speed in innate. A person's preferred cadence is like the speed they talk (or walk) at: very much built in. If you pedal 170mm cranks at 90 rpm you will pedal 120mm cranks at 90 rpm!! Well, you will want to. When you see your riding buddies disappearing in the distance you will start flailing away trying to get some road speed to catch them. If you have lowered the gears to match the percent reduction in torque of the shorter cranks you will have to speed up well past what is 'natural' to actually be fast. I wouldn't know, but I have heard that using cranks shorter than 140mm (found on bikes for children in the US) makes you feel like "your feet are tied together". That's just what I have heard. Maybe you will feel differently. Maybe you already have tried short cranks and like them. This is just what I've heard.
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