The Search for Fuel Economy

Pages from a Designers' Notebook Readers comments P3

Chap. 9: Rear Bulkhead and truck bed

A brief narration regarding where we are going

With tail for cross country
Without tail for the city
As I build and ride this thing, solutions to problems emerge. For example, where will I put the license plate, tail light and turn signals? They cannot go on the point because it is a point and there is nothing there to put them on! The solution appeared when I realized that I could not completely streamline the area around my head. The air will be "Dirty" (unstreamlined there). I will mount these components in the headrest. Better to have just one area of "Dirty-ness" than many small ones. Actually, the lights will be more visible up there, thus we will be safer.

In addition, we don't need the tail in the city. So, I will make the tail go on for cross country cruising and go off easily for inner city riding. This means that, with the tail off, my Helix will be the same length as stock.

Quick! Name me any 2-wheeler than can carry 3 bags of groceries.

I see this thing as a "two wheeled truck." If it cannot carry at least 3 bags of groceries, what good is it? The next step, then, is to make a "truck bed" and be sure it is streamlined.

My friend, Carl is building a 2 door 1948 Lincoln. He also has a sheet metal shear and bender and kindly agreed to make my "truck bed"
Fits me perfectly
Too low for Zak
We have a problem
With the bed and bulkhead finally in place, a serious problem shows up. I made the streamlined body to fit me. (Top, left) My son, Zak, sits 4" higher, from his seat to his shoulders. Top right. Zak won't be able to ride this thing because he won't fit into it. Many of my friends won't either. If I raise the top line 4", frontal area goes up too and I won't be as streamlined as I want. The solution?

Reluctantly, I raise up the rear line 4" by adding an extension to the loop. I will make the seat with a 4" removable cushion for the big guys. This is better for me because a higher seat is more comfortable. Compromises, compromises. This is what design is all about.

"You want this? You gotta give up that"

Vetter Design Truth

Next: making the rear bulkhead:

If you look closely, you can see the 4" extensions in the loop in the background.

Making the rear bulkhead is just like making the middle one. Using CAD and a hot melt gun, I generate the shape and transfer it to a piece of plywood.

Template for the rear bulkhead
Around the plywood I make a cardboard ring and then one made of aluminum, just like before. Oh yes... I added 3" to the rear bulkhead, too. These two rings will serve as mounts for the center portion of streamlining.
Making the rear bulkhead
At this point, all this body assembly can be removed with three nuts for maintenance to the scooter. I am a lazy motorcyclist and have no patience for a machine that is hard to work on.

"A good design is not more trouble than it is worth"

Another Vetter Design Truth

A nightmare of holes and screws
The 4" extensions are clearly visible in this shot. Also, you can see all the extra holes I have drilled and not used. When we make a prototype, we have no printed plans to work from. Everything is made by trial and error. I make a lot of errors. If this ever turns into a kit, you will know exactly where the holes go before you drill them.
Before I can wrap the bulkhead hoops with streamlining, I must tuck in the things that are in the way of the streamlined surface
The Helix engine is its own swing arm and rocks up and down. I must account for this. In addition, the air intake snorkle is in the way. I must make a new airbox cover to relocate the snorkle. All these things take time. (by the way, the engine hardly runs with the snorkle off)

It will not being able to perfectly streamlined at the very bottom because the swing arm has to bounce up and down and the wheels stick out.

The air intake snorkle must be moved
Where we are as of June 8, 2008
There is still another week of boring detail work... mostly focused around the bouncing engine. I want the streamlining to be as close and tight as possible. Soon, I will wrap this and the rear section will be pretty much complete!

And you thought I was going to have to make molds and fiberglass parts.

Next step: Wrap it in a streamlined shape
This page updated June 8, 2008
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