Buying a bike for MPG/Vetter Challenge, what would be your favorite?

[alvaro84]

I don't think that ergonomics have anything to do with engine displacement. I know that manufacturers usually make their big bikes more comfortable, but I don't see a comfortable 250 impossible at all. Then it won't be a problem to go thousands of miles on such a bike. Iron butt days is another question. 1000 miles one day have to be fast. In my normal pace it's nearly impossible, even without stops if any cities or even villages are involved (ummm... I'd need a bigger tank to do it in one go, and indestructible nerves). No matter the engine displacement in my case, but bigger ones can naturally handle high speeds better.

[DoctorM]

Originally Posted by alvaro84

I don't think that ergonomics have anything to do with engine displacement. I know that manufacturers usually make their big bikes more comfortable, but I don't see a comfortable 250 impossible at all. Then it won't be a problem to go thousands of miles on such a bike. Iron butt days is another question. 1000 miles one day have to be fast. In my normal pace it's nearly impossible, even without stops if any cities or even villages are involved (ummm... I'd need a bigger tank to do it in one go, and indestructible nerves). No matter the engine displacement in my case, but bigger ones can naturally handle high speeds better.

A lot depends on your personality, your body size, and the environment your going to be riding in. If you are in a small town (especially a small college town), you are pretty light weight, and you are only taking short rides, and you aren't a throttle popper, then a small displacement motorcycle of 250cc are less may be just great for you.

But for long rides (and I have been not only coast to coast and back, but from the top of Virginia to Mexico and back) a small bike is going to be very uncomfortable. It can be done, but generally the bigger and plusher the bike, the easier and more pleasant it gets.

As far as a 1000 mile day, it takes about 24 hours straight through to do it at normal highway speeds. Motorcycles have to fuel up much more often than cars, but the break in riding is also very welcome. Rides that are comfortable enough for ten miles become increasingly more uncomfortable as the miles drag on, and your legs get cramped because they can't move around much.

On my 700cc ride, I could change my seating position from front seat to back seat, and stand up on the pegs to get some blood circulating back in my legs. That was when the bike was new and tight. I couldn't do that today -- too much wear and wobble.

Anyway, good luck on whatever you pick. In my opinion the decisions are always more emotional than rational, although a lot of rationalization is done in the name of "logic."

[sendler]

The goal is 100 mpgUS lifetime and 100 mph air speed capable into 30 mph head winds.

[alvaro84]

Originally Posted by DoctorM

In my opinion the decisions are always more emotional than rational, although a lot of rationalization is done in the name of "logic."

I made an absolutely emotional choice from a rationally filtered selection of bikes

[Michael Moore]

alvaro84 @ post #114 makes an excellent point. You need to distinguish bigger bikes from bigger engines.

Yes, a 100cc bike with a 47" wheelbase would be pretty cramped for a long ride, and a small engine is usually coupled with a physically small OEM chassis (at least for the street). Touring bikes often have a 58-62" wheelbase to give you room to move around and stretch out a bit.

So if you want a small high-mileage engine but wish to go long distances couple that engine with a chassis sized to give you long-distance comfort.

cheers,
Michael

[DoctorM]

Originally Posted by sendler

The goal is 100 mpgUS lifetime and 100 mph air speed capable.

Well. I could get 60+ mpg on a unmodified 700cc street ride, but only at about 45 mph in top gear. The trick was to ride as slow as possible in top gear, without lugging the engine. So I think 100 mpg on a smaller displacement bike is achievable without a lot of modification, if that is your only goal. I don't normally ride like that, but I have on couple of occasions done it at night when I was low on fuel in rather remote and desolate places, far from any open gas station.

You would probably want narrow, very hard, high-pressure tires to minimize rolling resistance - maybe racing slicks (no tread.) Maybe even solid rubber tires. So you might want to look only at bikes that have the same wheel size as available racing slick tire. And you might want to fill them with nitrogen instead of air. If you do that, don't ride in the rain.

Reaching 100 mph on a small engine will require a very efficient fairing, and likely wind tunnel testing, as aerodynamic drag force increases as the square of the velocity. This might be much harder to achieve than getting 100mpg at slower speeds. The honest sustainable top speed on my un-faired 700cc ride was only about 95mph. Of course, I could go faster than that down hill, or with a strong wind at my back.

I think you might want an aerodynamic consultant like Burt Rutan, or at least look at his work, and maybe write him for ideas. A few decades or so ago, when I was still an active airplane pilot, He designed and built a 20 hp airplane that could fly a single person at 100 mph and get around 100 mpg. Burt Rutan is a genius, and I don't know that anyone has duplicated that, so it is not such an easy thing to do. Somebody may still sell his kit, If you could get one of his fuselages without any wings, maybe you could stuff a small motorcycle inside it

If you are designing your own, I'd go for the ultra-reclined position to minimize frontal area. For a long ride, that would be far more comfortable that the tucked-in, crouched position motorcycle racers use.

If you are going to design and build your own fairing, you might also want to consider "dimpling" the surface, as on a golf ball, rather than a smooth surface. I think Mythbusters (on TV) did some half-assed testing on that concept.

Sounds like an interesting project for a group of aeronautical engineering students.

[sendler]

You are coming in at the end of a very long thread and a very long project. You have some reading to do. On Ecomodder and here:
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Craig Vetter, designer and inventor of the Windjammer fairing,Triumph Hurricane Motorcycle and fuel economy motorcycles
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