How Low Can You Go? Reverse-engineering for 30MPH

Discussion in 'Off Topic' started by augidog, Feb 13, 2010.

  1. augidog

    augidog Banned

    all politics aside, all speed aside...for the sake of the green door...if demonstrating "MB-efficiency" was your homework assignment...

    shift kits, cvt's, anything goes...let's say we wanna move 300lbs @ 30mph on the level...developers insight most-welcome...just how small an engine could we use if we exploited every innovative idea we have going for us, and what kind of realistic efficiency numbers could we produce?
     
    Last edited: Feb 13, 2010

  2. safe

    safe Active Member

    [​IMG]

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    There's a funny story attached to this one...

    Back around that time (about 1989) I was working at a software company that made a MAC based CAD program and I was a guy doing tech support. So I get this phone call and this guy starts talking about what he's doing and I realize that it's Craig Vetter on the other end of the phone. Small world. I tell him my interest in his work and how honored I felt to be talking with him.

    Anyway... sort of a "Forrest Gump" story I guess.

    At my old favorite racetrack, Laguna Seca they ran a competition back in 1980 - 1985 for this sort of thing:

    "The Freedom Machine would be any vehicle that gets 100 miles per gallon, at 70 miles per hour, carrying at least 4 bags of groceries."

    http://www.craigvetter.com/pages/470MPG/Vetter Fuel Economy Contests.html

    ...there was another inventor that was also involved in the Gravity Bikes that built a lot of stuff and for some reason I can't remember who it was that also built a motorcycle that had even longer range.

    Who was that?

    Gravity Bikes

    High Mileage Motorcycle

    ...and he had some sort of Balloon Tire Offroad bike that he sold too. He lives in Mammoth Mountain I think and he's more or less retired now and his kids are now running the business.

    Update: The answer is Dan Hanebrink with a motorcycle that got 557 mpg, but he seems to have slipped off the internet these days and images are hard to find.

    [​IMG]
     
    Last edited: Feb 13, 2010
  3. safe

    safe Active Member

    Attached Files:

    Last edited: Feb 13, 2010
  4. augidog

    augidog Banned

    hi safe.

    Mr. Vetter contacted me in MBc's early days to inquire into what we were up to, but i think he lost interest when he learned how far down the food chain we are...after all he's frying bigger fish...i sure do admire the man's legacy and his freedom machine efforts, it would have been a hoot to tie MB's into it all.

    but for us little guys...300lbs is a rider/bike/groceries, and 30mph works for a lot of us...and i wonder what MB-config would ultimately stand out if efficiency was the deciding statistic under controlled conditions.
     
    Last edited: Feb 13, 2010
  5. Drunkskunk

    Drunkskunk Member

    Just How Small?
    Thats not such a hard question, if you leave efficancy out of it.

    http://www.exploratorium.edu/cycling/aerodynamics1.html is a calculator that figures how much energy you need to go a given speed on a bike. for 300lbs, flat ground, and no wind I came up with 317 watts. Essentualy, 1/2 horsepower.

    Chain efficancy and gear efficancy varry, but generaly I've found 5% per stage gives me fairly accurate results. I wouldn't want to run a single stage, because getting the smallest motor means i would need to run through a derailer to get enough power to accelerate up to 30, so a 2 stage system would work. I figure 10% loss roughly 32 watts.

    Add a little extra wind drag from the motor, and I'll call it 400 watts power needed.

    At a basic level, a .15 RC glow motor puts out 400 watts, though good ones put out 1100 watts. Thats Just 2.5CC !!!

    So the smallest practicle I think I could go is 2.5cc
     
  6. augidog

    augidog Banned

    no sooner did i start reading your reply than i realized i'd left a lot of loopholes in the proposed homework assigment...

    you came up with a number uncannily similar to two different landspeed motorcycle racers...Rick Yacoucci & Derek McLeish...2.1cc RC engines and speeds of 20-30mph at the trap...i tried to find some details, maybe someone will have some luck with this, but i recall reading that one of them did this by towing the bike up to 58mph and releasing at the starting line, then downshifting to maintain speed thru the trap...there's actually a "category" for mph/cc at the Salt Flats...interesting...combining that info with your post suggests i could do the same with a low-drag single-speed belt drive and pedal-assist...and i suppose so long as i wasn't pedaling thru the trap & was under engine-power-only the "statistic" would stand.

    thanks for the input, Drunkskunk, and for pointing out that altho my proposal as is wouldn't lead to practical answers, it would lead to some fun answers :)
     
  7. ibdennyak

    ibdennyak Guest

    2.5 cc. Geez, gonna have to rethink some of my ideas.......Must be using NoS. :>)
     
  8. augidog

    augidog Banned

    then let's keep goofing around...anyone able to guestimate how many mpg's Drunkskunk's virtual 2.5cc multi-speed MB is capable of? is slightly larger gonna do better?
     
  9. Drunkskunk

    Drunkskunk Member

    Some of the guys I used to fly with could suck down 16oz of fuel in half an hour, running their stunt planes hard. That would work out to 1 gallon every 2 hours at 30mph, or 60MPG.

    But RC fuel is 20% nitromethane, and $20-$30 a gallon

    Not exactly efficent. But tiny!
     
  10. augidog

    augidog Banned

    doin' the math...did i miss something?

    at 16oz/half-hour or 32oz/hour i come up with 4 hours/gal...overall that's very impressive...

    still, the cost of that special go-juice pretty much kills the efficiency aspect...

    alright, then...how much larger would we have to go before we can use plain gasoline?
     
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