Aerotrunk project

[Grant-53]

Having a tight fit to the rider is key and fairing behind the helmet helps too. The body sock has been tried on bicycles and a Kevlar fabric will give some protection from road rash. So far the advantage is with the partial panels used on Alan's fairing. The issue of safety and body work is beginning to be examined. The slide for life is acceptable at a race track as long as no one runs over you. On the street the body needs to be stiff enough to protect you if you slide out. A front crash requires some crush energy and an inertial reel lap belt so you can still knee drag but not get launched over the handlebars.
To keep the tail box short we are working with a 5:1 foil shape cut to 50% of length.

[sendler]

We all need to keep this aero trunk project in the context it is intended which is not a full out assault on aerodynamics such as a full Vetter streamliner. This is supposed to offer a quick and cheap way to add a trunk and gain some aero improvement of whatever it will be along the way.

[low&slow]

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.

[low&slow]

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.

[renault_megane_dci]

I was under the impression that aero improvement such as your aerotrunk should only show when you ride on the motorway ?!

[low&slow]

The aerotrunk should make a bigger improvement at freeway speeds (65-75mph) but it still should help boost fuel economy at medium speeds as well ( 45-60). This tankfill had several issues: all short trips, lots of stops and starts, cold and cool weater, winter blend gasoline and it was over 2 months between fill ups. Now that I'm done for a while with changes on the bike, the test run results will be better measurement of the benefits of the aerotrunk.

[low&slow]

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 errand. 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.

[renault_megane_dci]

I don't know about you guys but with my car I always seem to do better in the first quarter of the tank.

This is not about how fast the gauge goes down but about but what the car computer tells me.

[American Viking]

Originally Posted by 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).

Not quite, I know of a few Buell riders that have changed their final drive ratios without having to convert from belt to chain.
First you have to find the next higher count belt. Its not like a chain where you just add even numbers of links. These belts are extruded from a mold as a tube, then sliced to form the belts like Calamari rings or rubber bands.
Once you know how many more teeth you have to work with, you can now measure the available space front and rear. Add as many cogs to the front counter sprocket as you can, for two reasons.
i. on additional cog on the front makes a larger change then one less on the rear.
ii. adding cogs on the front moves you away from minimum tooth/wrapping issues.
Just make sure that you don't end up with the count on the rear being a multiple of the front, as that will accelerate the wear. so no 15/45 counts.

After that it is just a matter of finding a fabricator to make the cogs

Originally Posted by alvaro84

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

Short of having the rider always laying on the tank, adding anything behind the rider will likely have to extend past the normal end of the bike.
Also any device added there will have issues with moving both the center of mass (which will effect handling, depending on how heavy it is) and moving the center of pressure (which will effect aerodynamic behavior).
The best aero device for reducing drag behind the rider would be what I can only call a cape attached to both the rider and the bike.

[American Viking]

Originally Posted by Grant-53

Having a tight fit to the rider is key and fairing behind the helmet helps too. The body sock has been tried on bicycles and a Kevlar fabric will give some protection from road rash. So far the advantage is with the partial panels used on Alan's fairing. The issue of safety and body work is beginning to be examined. The slide for life is acceptable at a race track as long as no one runs over you. On the street the body needs to be stiff enough to protect you if you slide out. A front crash requires some crush energy and an inertial reel lap belt so you can still knee drag but not get launched over the handlebars.
To keep the tail box short we are working with a 5:1 foil shape cut to 50% of length.

As an avid rider of 30 years, a former road racer and an urban road warrior (Moto-courier in a major city), I've done my share of crashing at the track and had a couple of street wrecks. BTDT-GSTPI. I disagree with you on your safety points.
1. High-side, low-side, over the bars or washed out doesn't matter, The best chance you have of surviving a crash is to get flat and slide. Balling up = Tumbling = Impacts = broken bones, severe bruising and other impact traumas. Assuming you don't slide into anything, Getting flat = Sliding = dissipating energy = possible road rash and friction burns. Wearing the right gear will absorb the first impact and nearly eliminate road rash or friction burns.
2. The last thing you want in a crash is to be tethered to the bike. If it tumbles (which seems to be about 95+% of the time) and your tied to it either you tumble too with all those bone shattering impacts, or the bike tumbles on top of you and you experience different bone shattering impacts. Trust me, the first thing you want to do in a crash is get the heck away from the bike. Let it dissipate its kinetic energy on something other than your body.
3. A really hard tough shell is a bad idea. A hard shell is going to slide forever compared to a leather or textile skin. Its not going to absorb the Kinetic energy as well, so when you hit something because of the longer slide, your going to slam into the hard shell and its not going to absorb the energy. Better to have some textile skin with padding behind it. Its safer on the street if the body shell breaks up on the impact, expending as much energy as it can. A fiberglass/Kevlar shell is going to be much safer than say a steel skin.