Supermileage on a motorized bike

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skyl4rk

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Aug 14, 2008
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I am wondering if anyone has ever tried to get extremely high mpg out of their bikes. I know I got about 125 mpg on my Titan kit on one tank. I think 500 mpg is potentially attainable, although at slow speeds.

We are already set up with the right size motors for supermileage competitions.

The most important thing is that to get high mpg numbers, you need to pulse the motor to accelerate up to speed, then coast with the motor off as long as possible before pulsing again. So low friction coasting is very important.

Aerodynamics is also important. But at slow speeds you should be able to get very high mpg numbers with just a bike.

One thing that might be difficult is to figure out how pedaling affects mpg numbers. If I pedal 100% of the time, I get infinite mpg. If I pedal to start out, I improve my mpg by quite a bit, because the start takes a lot of power. If I lightly pedal while at speed, just adding a little extra power, I can still make a big difference in performance of the engine.

So for practical use, it is OK to use pedaling techniques, but for competition and comparison it is difficult to regulate how much pedaling the competitors can do. The more the better as far as I am concerned but then competitive people will just pedal all the time and not use the motor.

How would you set up a supermileage competition for motorized bikes? What rules would you make about pedaling? How would you set up the bike?
 

BarelyAWake

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Well, first off I'd say pedaling isn't as much a concern if the event is a combination of both efficiency and speed, thereby encouraging the use of both engine and pedals as much as possible & leveling the playing field with both ounces of fuel & time on the clock worth points.

A 9hp monster may finish first w/o any pedaling - but fail at the supermileage.
A 1hp "helper" may win at the supermileage, but even pedaling won't make it as fast.

Measured fuel allotment & timed laps, figuring who got the most outa the least I figure ;)



"How would you set up the bike?"
For this game? Oh... I might be workin' on sumfin' :D
 

happyvalley

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We are already set up with the right size motors for supermileage competitions.
Agreed, legal size MABs are right in the sweet spot.

So for practical use, it is OK to use pedaling techniques, but for competition and comparison it is difficult to regulate how much pedaling the competitors can do. The more the better as far as I am concerned but then competitive people will just pedal all the time and not use the motor.
Motor assisted bicycles by definition have pedals so what could be wrong about using them them? It adds fitness to the equation, a measure of man and machine. The other end of the competition spectrum is who is willing to throw the most money at strapping the biggest engine to a bicycle frame. As Grease Rat said: "Speed's just a question of money, how fast do you want to go"?

How would you set up a supermileage competition for motorized bikes? What rules would you make about pedaling? How would you set up the bike?
Pedals; use'em or lose'em, check this thread for some ideas being hashed over
http://motorbicycling.com/f35/what-id-love-see-mab-competitions-35306.html
and the link to Craig Vetter's site for his imput on MC comps.
 

skyl4rk

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So maybe a fairly long course (40 miles?) with a maximum time limit. Or maybe winners selected in categories based on elapsed time.

Example: 40 mile course
Elapsed Time Categories
Less than 2 hours (average 20 mph or more)
2:00 to 2:20 (average 17.1 to 20 mph)
2:20 to 2:40 (average 15 to 17.1 mph)
2:40 to 3:00 (average 13.3 to 15 mph)
Over 3 hours (average 13.3 mph or less)

The total distance needs to be well under one tank of gas for all competitors. Maybe 40 miles is too far.

An easy way to get a supermileage bike would be to add a friction drive with a 35cc four cycle motor. Power up to speed, kill motor and then lift friction drive to coast as far as possible. Repeat until finish.

Theoretically chain is more efficient than friction drive, but I don't know how to disengage the chain from the wheel for efficient coasting. Even a freewheel sprocket has friction. I'm sure some mechanical wizard could figure that out.

A prone rider position would improve efficiency by quite a bit. Recumbents would have a big advantage. Fairings would be an advantage. But even the average motorized bike should be able to break 100 mpg easily.
 

happyvalley

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Thanks for the link. While certainly compelling reading and a completely worthwhile endeavor, the design parameters of the SAE collegiate competition are geared toward mechanical engineering departments at universities and sponsored by Briggs and Straton using their engines for fuel driven vehicles. The rules prohibit any added human power, sails, or other ancillary systems. A MAB would be ineligible under their format.
 

skyl4rk

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It is an example of another supermileage competition. They have a minimum (15mph) and maximum (25mph) speed per lap, and you are penalized if you go over or under.
 

BarelyAWake

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The only practicable solution I see for those that have expressed interest in this competition is if it's not a closed course race at all - but an endurance road rally containing time trial sections, to insure compliance with the chosen route & posted speed limits. How pedaling/physical fitness effects fuel consumption would still be an issue - but this could be offset somewhat by making the route far longer than the average pedal bicyclist would consider, by retaining a bonus for minimum times met yet still compliant for that area's posted speed limits, the motorization vs efficiency could also still retain some validity. From my experience I would think for a good, general test of both man and machine under these conditions, at least a fifty mile course would be required... less if it's in exceptionally hilly terrain or w/e.
 
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happyvalley

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It is an example of another supermileage competition. They have a minimum (15mph) and maximum (25mph) speed per lap, and you are penalized if you go over or under.
Right, and I am enjoying that site and agree that good ideas could be culled from there, plus the links to the design team pages are great.

A tight, closed course is used in competitions like the SAE Collegiate making the recording and monitoring processes efficient though perhaps somewhat stolid and leaning toward the academic. An open road rally would probably be more fun while being a bit more involved to monitor perhaps but then running the event completely on public thoroughfares might present challenges beyond the control of organizers and participants, depending on location and jurisdictions.

Perhaps a combination of closed circuit and open rally might be something to consider. The most popular event today in the bicycling world is cyclocross, by way of sheer numbers of participants taking part anyway, perhaps there's something to be learned from that. Typically cyclocross events are between 30 and 60 miles run with multiple laps on a fairly short course of 1 to 3 miles, over varying terrain, and will often include over the road sections, in addition to loops that organizers have established for spectators, start/finish, pits, parking, etc.

One further thought on the pedal question though, it seems given the fact that MABs have them by definition, their use would be entirely up to the digression of the participant. If I were interested say, in designing a vehicle for pure aerodynamics, for for top speeds either in a straight line or on a track with turns, pedals would only be a hindrance and liability, that's why motorcycles did away with them. In terms of fuel efficiency with MABs, that hindrance comes back into it's own as a potential asset.
 
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skyl4rk

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I would like to see a road rally competition in a rural area with not much traffic and with rolling hills to allow for pulse and glide coasting using elevation changes.

From my perspective it would be done mainly for fun and bragging rights, but you know as soon as you get two bikes together it becomes competitive.

One way to handicap a bike would be to not allow high gear pedal gears and make sure the pedal gears are low enough to allow for easy starts but not pedaling while at speed. In this class, it would be more of a test of motor, design and riding skills. The idea is that human power starts the bike from a stop and then the motor is engaged and there is no more human power until the bike stops again. I would encourage the use of human power from a stop because this makes clutch and gear design much easier.

Another class might allow unlimited pedaling and encourage "hybrid" use of human and gas power. This would start to encourage the athletic person to participate. Actually, a human only powered bike could win if the race was decided by max mpg. So this race would have to have a relatively high minimum average speed.

I think the most practical solution would be to make a rule (get everyone to agree) that pedal use is OK only when starting from a stop or from walking speed. Once you exceed 10mph or so, then no more pedaling.

How would you do the topping off of gas tanks? Start off with the judges filling the tank to a certain point? Use a measured flask of some kind at the end of the race?

I would not want to fill tanks all the way to the top. Maybe there is some gauge that could be put in the fill opening and tanks would be filled to a line on the gauge. Use a turkey baster for fine adjustment.

Then at the end of the race use a measuring flask to measure the amount of gas needed to replace fuel used.

What about bubbles in the gas tank? Maybe this would not be a problem.