Scratch Built Tricycle Maximizes Fuel Efficiency

While the bicycling community is welcoming an influx of electric bikes, there’s a group of tuners on the fringes that are still intent on strapping gas motors of all sizes to bicycles and buzzing down the roads in a loud and raucous fashion. Kits are readily available and are much cheaper than comparable e-bike kits, and with a little bit of work it’s possible to squeeze a lot of excitement from these small motors. With a lot of work, though, you might end up with something like this incredibly fuel efficient and fully customized reverse trike from [Paul Elkins].

The entire goal with this build was fuel efficiency, so the plan is to eventually enclose the vehicle in aerodynamic fairings, most likely using his favorite material, Coroplast. The frame itself is completely hand-made from square tube and welded by [Paul] himself to his own custom specifications. He bolts on a suspension and custom steering rack with levers to control the two front wheels, and the small engine and gas tank are attached to the back above the single drive wheel. The engine hadn’t been started in ten years, but once he got it all put together, it started right up and he was able to take his latest prototype out on the road for a test drive.

While the build isn’t completely finished, the video below (eleventh so far in the build log) is far enough along to show the fruits of years of [Paul]’s labor. It’s taken a while to get a design that worked like he wanted, but with this iteration, he finally has what he was looking for.

27 thoughts on “Scratch Built Tricycle Maximizes Fuel Efficiency

  1. Now we only need to know how fuel efficient it currently is. And how much more fuel efficient it gets when it is finished. (If project vehicles like these ever really get finished…)

    Though, to be fair, fuel efficiency should probably be somewhat in regards to passenger/cargo capacity.
    A bus for an example isn’t particularly fuel efficient for 1 person, but cram in 80 people and suddenly it is a different story.

    1. If you want to go down that road, you should also look at the average ridership, or passenger miles per actual miles, and the number of starts and stops per mile.

      When estimating bus efficiency, you have to notice that the fixed bus routes are almost never the optimal route or shorter than the route taken by the passengers themselves if they went directly from A to B. At best the difference is negligible, such as between two cities where there’s essentially just one way to go, but within the city and the sub-urbs you start to lose efficiency for 1) going around the longer way by taking detours to serve more customers, 2) starting and stopping to pick up passengers, 3) running an empty bus on the off-peak hours, 4) transits to/from the route.

      Even though a bus fits 50, the average ridership throughout the day might be under 5 because it still has to go around every 20 minutes whether there’s anyone on the stops.

    2. A vehicle like this can get an estimated 100mpg tops at 35-40mph, depending know the engine used.
      If this guy is smart, he’d equip it with a 125cc, which may seem like overkill, but running at 1,5-2k rpm it will do 30-40MPH much more efficiently than a 50cc running at 5k rpm.
      A 50cc with a tall gear ratio is good if he wants to do no more than 25 mph on it, using pedals to kick start it (go from 0 to ~10MPH), and then let the engine take over.
      The only way to really use a tall gear on these things.
      If it has no pedals, he’d at least need a low speed gear for starting, and a high speed gear for efficiency.
      The gear spacing may be very wide (low speed gear doing 5mph at 2k rpm, high speed gear doing 20mph at 2k rpm for a 50cc).

      1. The motor and rear wheel/swing arm are from a 1981 Yamaha 185cc street bike. I will be cruising in this rig going no more than 65 mph. The front suspension was gleaned from the record breaking ‘California Commuter’ fuel efficient trike from the early 80’s.

    3. Around here the buses carry “ride the bus” promotional greenwash advertising, showing a cartoon of a bus (with bus exhaust), a big equals sign, and 48 cars (with 48 car exhausts). I suppose the implication is that a bus has only one exhaust but can replace 48 cars.

      But I always see it as a bus emitting as much pollution as 48 cars. I’ll bet that’s not far off the truth either.

      1. Easy math equivalent here would be semi trucks. 7 mpg hauling 80,000 lbs is far more efficient than a 55 mpg Prius with it’s 800lbs rating. Google be saying buses get about 6mpg, which divided into ridership gets you 330mpg/ person when fully loaded.

      2. If your talking about american buses, your right. Old, noisy, dirty, takes you no-where. Most every out side of the USA, that’s not true. Dirty on the Inside, outside, and exhaust. Most everywhere else, even in less well off countries then the USA, buses, are clean and packed.

  2. I believe ‘Reverse’ trikes are called a ‘tadpole’ configuration in the light trike world. I think with the single wheel in front they call it a ‘delta’.

    1. Is there a name for the two types of tadpole steering? As in maybe car versus forklift? Or the rear wheel steering is call taildragger in airplanes. Gokart versus taildragger?

  3. These bikes get you into so many debates with people who don’t have a good grasp of physics.

    The basic question is, why is the reverse trike still very dangerous? It apparently solves the tipping and running yourself over problems of the regular trike.

    Answer: look at where the center of mass is, then look at where the center of “drag” (braking) is. When you have to do a hard brake, the center of force or where the equivalent braking force would appear is in front of the center of mass, so the whole thing wants to spin around if there’s any difference between the two front wheels. In other words, in an emergency situation, this vehicle tends to take a random duck-and-dive off the lane, or if it’s slippery then it spins out.

    1. So, how is this different from any other wheel configuration?

      If your center of mass is between the front and real wheels, and above the road surface (so, *every* road vehicle), then the available front-wheel braking force will *always* be greater than the rear wheels’ (or wheel’s).

  4. The ending reminds me of a time 50+ years ago when my friends older (hippie) brother came roaring into the garage on his trike and quickly pulled the garage door down, just before a cop slowly cruised down the street looking in every driveway.

  5. We built similar tricycles in high school as part of metal shop. We took them to an endurance racing type competition which had a limit not only on time, but also on total amount of fuel that could be used. It was a nice added wrinkle because you had to balance getting the most laps possible in the time frame allotted while also not running out of fuel. Most of the vehicles were reverse tricycles, but some did have some weird layouts (motorcycle with side car, bike with training wheels meant to lean back and forth in turns). There was a very minimal ruleset mostly based on safety.

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