Aerotrunk project

Discussion in 'Street and Performance Bikes' started by low&slow, Oct 8, 2013.

  1. low&slow

    low&slow Well-Known Member

    Vetter Challengers seek to develop vehicles that get over 100mpg, can go over 70 mph into a 30 mph headwind and can carry 4 full paper grocery bags on board. My streamlined Ninja 250 can easily do this. (For more information on the Vetter Challenge check out motorcycle designer Craig Vetter's website at Craig Vetter, designer and inventor of the Windjammer fairing,Triumph Hurricane Motorcycle and fuel economy motorcycles )
    But streamlined motorcycles aren't for everyone so in my pursuit to show how to make motorcycles more efficient and useful I decided to work on another, less radical project. I decided to limit my modifications to a few simple tweaks and see if I meets the goals of the Vetter Challenge with my 2005 Ninjette.

    I started by raising the gearing from stock by installing a 15T countersprocket and a 41T rear sprocket ( vs 14/45). It has been my experience that the Ninjette can handle up to 15/37 pretty well. I then made a taller windscreen and fully faired in my front wheel. Now I was ready to make a detachable trunk that would further reduce my aerodynamic drag and give me lots of cargo capacity.

    First I cut out a 1/2" plywood base with slot for the rear grab handle to pass through that the aerotrunk can be clamped down by pushin some slats of right size to force the base down tight. I decided on a 29" for the length. The width was 16", a bit less than my shoulder width. The front bulhead is just under my seated shouder height at ~ 18" at the sides and arching up to 21" at the center. The rear bulkhead narrow down to 12" wide, 14.5" at the sides and arching up to 15" in the center. I then cut a loading opening in the front bulkhead 10" wide x 15" high. If you decide to make your own aerotrunk make so that it is just shorter and narrower than your torso as you seat on the bike. If it sticks out past your body profile it will likely increase the air drag rather reduce it.

    After attaching the front and rear bulkheads to the base with glue and screws, I skinned the aerotrunk sides with some very thin plywood veneer (~1/8", commonly called doorskin"). For the curved top I installed a wooden lath for a central spine. Then I hot-glued some treated sign paper to the spine and the top of the sides as a form for a layer of fiberglass. After glassing the top, I used some fiberglass strips to seal and reinforce the edges. Then I painted it and mounted on my bike using the inner wood slat clamps a long bungee cord hooked on the lower edges of the front loading opening, passing around around the foldout hooks at the seat sides.

    The aerotrunk easily holds over 3 full paper grocery bags ( probably could stuff in 4 ). I made a cover for the front opening out of some coroplast. Initial testing shows I'need to refine the inner clamp so that bouncing doesn't make the them come loose. Fortunately the bungee cord backup is very secure.

    I'll test out these mods soon and report how it does fuel economy wise. Previously I've done around 80mpg on my 100+ testing loop before the mods.[​IMG]

  2. Prozac

    Prozac Well-Known Member

    This would give the little Ninja something that it is desperately missing, storage. I would have probably fiberglassed the base in order to make it more form fitting to the bike, but it seems that you have other plans. Looks great!
  3. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

    How does it open? I would have thought the top opens like a lid, but that spine down the middle says otherwise.
  4. beatr911

    beatr911 Tightwad

    Trunks are one hugely handy device on a motorcycle. Making it also add performance to the bike by reducing drag is something that the aftermarket hasn't yet realized. Hopefully that will change.

    Vic, I'm just a little concerned that the brake light will be obscured to drivers by the trunk overhang, do you have plans to relocate it high on the trunk? Easier yet, just splice in an additional light(s) and mount them on the top of the trunk.
  5. low&slow

    low&slow Well-Known Member

    Prozac, Thank you!

    PM, the trunk is loaded through the opening in the front bulhead. I still need to finish the front cover and want to incorporate some foam padding on it so that I fill the gap between my back and the trunk.

    Garth, Thanks! excellent point! I was thinking the same thing and will add a brake light to the back of the trunk.

    all the best , Vic
  6. Prozac

    Prozac Well-Known Member

    Just remember, if you do decide to go all out with fiberglass, use the expensive painters tape. You can always add layers of cheap tape, but the initial needs to seal well. Otherwise, have fun figuring out the design. Fiberglass isn't that hard to work with as long as you have good resin. Look forward to seeing your next iteration of the project.

    Oh, and I love those little ninjas. It is definitely more fun to ride a slow bike fast than a fast bike slow. Keep up the great work!
  7. low&slow

    low&slow Well-Known Member

    Thanks for the tips , John . The Ninjettes are a lot of fun, but also very practical for regular usage.
  8. low&slow

    low&slow Well-Known Member

    I refueled today after hitting the reserve position; I went 362.8 miles and need 3.99 gallons to top off the tank for 90.9 mpg. Not bad, I did one longer trip and the rest was just running errands. I did close up the gap between between the front of the aerotrunk and my back by adding some stryofoam padding. I also added a brake light as the aerotrunk partially blocks it.
  9. EdwinTheMagnificent

    EdwinTheMagnificent Legend In His Mind

    Nice tank , Vic.
  10. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Low&Slow:

    have you done any back to back lengthy rides with and without to get empirical numbers for the actual benefit the tail provides yet?


  11. low&slow

    low&slow Well-Known Member

    Hi Wayne,
    I need to do the testing as you suggested to confirm the benefit of the aerotrunk. So far looking at past tankfills, it appears I was getting around 80 mpg with out the aerotrunk so the aerotrunk apears to offer around a 10-12% boost. I recently raised the gearing to 15/37 from 15/41 so that is an additional change. I'm very much into making modifications not as much into testing. But I do need to quantify the benefits of my mods to win more support for motorcycle streamlining.
  12. low&slow

    low&slow Well-Known Member

    Today it was time to refuel: 330.2 miles/4.05 gal.= 81.53 mpg. This tank I didn't go on any longer rides, just running errands with it. I redid my front fender and and extended the front edges of the aerotrunk to close up the gap between my torso and the trunk. I need to do some more test runs to show the difference between having the aerotrunk on vs. off.
  13. low&slow

    low&slow Well-Known Member

    Since I'm not riding as much due to the weather I decided to start fueling more frequently to get a better assessment of the fuel economy of my motos. I recently adjusted and lubed the chain after running some errands. I refueled after going 173.7 miles using 1.80 gallons of fuel for 96.5 mpg. This was all with the aerotrunk mounted. I still need to do a run on the test loop that Alan and I use but this looks very promising.
  14. low&slow

    low&slow Well-Known Member

    I still need to do the A-B-A testing to define the exact benefit of riding with the aerotrunk but in the interim I'll be comparing the difference between with aerotrunk and not. Today I refilled after traveling 106.9 miles, using .957 gallons for a result of 111.7 mpg. This is the best tankfill so far with this moto's current configuration ( 15/37 gearing, enclosed front fender, aero windscreen and the aerotrunk ). I'm done with modifications for a while so I'll just ride with aerotrunk off and see what the difference is.
  15. EdwinTheMagnificent

    EdwinTheMagnificent Legend In His Mind

    111.7 MPG is a lot better than what I'm getting !

    Good work, Vic.
  16. low&slow

    low&slow Well-Known Member

    Thanks Edwin!

    I did a ride today with a buddy into the Delta ( aerotrunk removed) and topped off after getting back: 113.7 miles/1.549 gal.= 73.4 mpg . There were a lot of hills and the pace was somewhat spirited but it does seem to show a marked difference without the aerotrunk. I may run another short tank to see what it does during more normal conditions. I think my worst tankfill with the aerotrunk on was around 85 mpg so compared with this one ( 73 mpg) it shows a difference of about 16%. More testing to follow.

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