Aerotrunk project

[low&slow]

[IMG][/IMG]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. http://[URL=http://s1066.photobucket.com/user/Vic_Valdes/media/Aerotrunk/006.jpg.html][/URL]

[Xist]

That looks pretty good! Does it taper?

[alvaro84]

I would be curious about the effect of the trunk itself, without the effect of the gearing change. Because making a trunk for Teresa is possible (it's just a differently shaped top case, after all), but gearing change would mean a complete rebuild of the final transmission (from belt to chain).

Something extending so much behind the vehicle's normal dimensions is still illegal here, but...

[euromodder]

Remember you must now load the bags in under 45 seconds to meet the Vetter requirements.

[low&slow]

Originally Posted by Xist

That looks pretty good! Does it taper?

Thanks! yes, its about 15" wide at the front and tapers down to 12" at the back.

Alvaro, we'll see what the change is after I complete some testing; though it should be a noticeable improvement. I need to make sure I fill in the gap between my torso and the front of the trunk.
Have you tried a taller rear tire on your bike? I did that with my shaft drive Vision for a small gain.

Euromodder, bag loading is very fast and easy with this trunk, no problemo!

[sheepdog 44]

On most of the Vetter style streamliners the seatback, or in this case the front of your trunk, is always flat and square like a box. I would think rounding the front of the trunk like a half circle would be better aerodynamically.

[Xist]

Originally Posted by sheepdog 44

On most of the Vetter style streamliners the seatback, or in this case the front of your trunk, is always flat and square like a box. I would think rounding the front of the trunk like a half circle would be better aerodynamically.

It would be in the wake of the rider.

[jkv357]

Originally Posted by sheepdog 44

On most of the Vetter style streamliners the seatback, or in this case the front of your trunk, is always flat and square like a box. I would think rounding the front of the trunk like a half circle would be better aerodynamically.

That bulkhead always catches my eye also, but as noted, it would be in dirty air anyway.

I would think it could still be flat as long as it was smaller than your body so there were no flat forward surfaces protruding outside of your outline.

[low&slow]

JVK and Xist are correct, thanks for jumping in!

I do need to work on filling the gap between the trunk and my back to eliminate the resulting turbulence. I'm thinking some foam attached to the front cover. I'll post some pix after I make it.

[Xist]

Originally Posted by low&slow

JVK and Xist are correct, thanks for jumping in!

I do need to work on filling the gap between the trunk and my back to eliminate the resulting turbulence. I'm thinking some foam attached to the front cover. I'll post some pix after I make it.

I know even less about this topic than most, but I have seen the spandex "socks" used to enclose the sides of streamliners. Why not make a spandex vest that zips to the trunk, you put your arms through the holes, zip up the front, and just like that, no gap!

That sounds all kinds of awkward!