The Search for Fuel Economy

Pages from a Designers' Notebook

Freedom Machine
The goal: 100 mpg at 70 mph, into a 20 mph headwind, with four bags of groceries.
Chap. 28: Show Time and then back to work

Posted Aug 1, 2009 revised Sep 6, 2009

The Vetter Display at the 2009 Quail Motorcycle Gathering

Friday, May 8 and Saturday, May 9, 2009 in Carmel, CA.

Upper right is a Triumph T160, containing my tank design of 1972. Then the 1973 Hurricane I designed. The red Series 1000 fairing of 1966 (to the right) is the first Vetter Fairing.

The Freedom Machine is the Last Vetter Fairing. We filled the Freedom Machine with ice and water for our guests.

Then it was off to Ohio and America's first "Gathering of Streamliners"

Motorcycle history was made at Mid Ohio at the AMA's Vintage Days July, 2009
There will be another "Gathering of Streamliners" in 2010. You are invited.

Much of the design process for me is using and operating what I design. This is where I learn what is good and what is bad. I have amassed a list of corrections and am anxious to get back to my shop to implement them.

How about some advice?
In the pics below I am determining where the Center of Area is on my Streamliner. I have glued a print of the Freedom Machine onto a piece of foam board. then I accurately cut it out. A push pin is stuck anywhere, a string with a weight is tied to the push pin and everything is hung. A line is drawn behind the string. This is done a second time. Where the lines cross is the Center of Area. If it was supported at this point, it would not rotate in the wind.
Below: I was balanced perfectly on a ramp which was supported on a steel roller. It was a Teeter Totter. I drew a straight line up from the center of the steel roller. This represented the Center of Gravity of me and my machine as I rode it.
The Center of Gravity is 11" ahead of the Center of Area. My understanding is that this is the right relationship. Question: Is the Center of Area the same as the Center of Pressure (Cp)? If not, is it usually close? Is 11" good? Would it be better if it were a different dimension? I will be starting over soon. These relationships can be changed. Don't be shy....
Ahah! You have ideas! Thank you. Read on:

Sep 3, 2009, Claude writes: Your calculations on center of pressure look pretty good. The center of area and center of presure are usually close enough, assuming a fairly uniform convex shape. More to the point would be the center of resistance. On a sailboat, the center of effort should be slightly behind the center of resistance so that in a sudden gust of wind the boat will weathercock, turning into the wind to relieve the pressure on the sails. A streamlined motorcycle needs a similar effect so that it turns slightly, causing the bike to lay over and heal into the wind. A well balanced bike does it automatically.
I think the relationship between the leverage of the overhangs and the contact patches of the tires would be the most important consideration. The tail section should be large enough to start a small countersteering action without making a sudden jerk that could cause an accident. Your description of the handling of the bike indicates that you have achieved a good balance between weight distribution, center of area and tire contact. Mostly, after the initial calculations, it just takes time and testing to make the adjustments

Craig comments: No matter how long the tail has been, I does not seem to have any detrimental effect on handling.

Claude continues: I still haven't come up with the perfect donor bike. There are some great chain drive engines that would be perfect if it weren't for the height of the frame, and some great scooters except for the difficulty of changing the final drive ratio.
After you have enough miles on the Helix to get a consistent average economy, I'd like to see what difference the Dr. Pulley wide range variator makes, plus maybe a HiT clutch afterward to reduce low speed clutch slip. That's about as far as the average owner would be able to modify the drive train on the Helix

Craig says: I am not going to put any more effort into trying to slow the engine down on the Helix. It still runs on wheels that are too tiny for 70 mph as far as I am concerned.

I'm looking forward to the next installment on this saga.

Sep. 5, 09: Grant says: The effective pressure center on your fairing is a bit further to the rear than the center of area. For fun make a 12" foam model of the body and mount it on a vertial car antenna. Let the antenna pass through the center of gravity and allow it to swing freely. Go for a ride and watch how well it points into the wind.

A freedom machine with a 50cc would have the advantadges of no federal emissions certification requirements and less weight than a larger engine. Torque, vibration, and economic life considerations might favor a larger engine.

Craig asks: What kind of 50cc engine is available with 12 hp, liquid cooling, electric start, 6 speed, in the US?

Back to work revising the tooling
The last time you saw this original streamlined foam shape was Chapter 7, May of 2008. In October, I installed Dodge Caravan headlights. They fit the existing plastic shape of the scooter but they pointed in the wrong direction so I really could not safely ride at night. I need to correct the headlights.
The first step was to establish a true horizontal reference line
With my laser beam I marked a true horizontal line to be used as a reference line for installing the headlights accurately.
Next I jigged up flat surfaces on a spare Caravan headlight (from EBAY) . Now I could set the Caravan light in place on the laser line, knowing that it would be pointing in the correct direction.
When aimed properly, the Caravan headlight does not come close to fitting the shape of my streamliner body. Well, it looked good. It is time to go headlight hunting.
I designed this "Aiming box" to hold in front of various cars to find a headlight unit that fits
All I have to do is to hold this box up to various cars until I find one that matches the curves. Not only do we need a shape that is going to fit the streamlined body, there are many other considerations:

Availability and cheap cost is important since I intend to offer this as a Streamliner Kit.

The light unit needs to include the turn signals into one slippery shape because turn signals that stick out are not streamlined.

Parking lots made finding the right light easy.

Holding the box level with the ground and parallel with the car.

I checked various cars out in the parking lot until I found one that fit. Then I ordered a set on EBAY. In this case, I was able to buy a set of new, Chinese-copy Prius lights for about $140. They are not the perfect fit but I could not find any car lights that were perfect. The price is right. Do you think you could find any streamlined motorcycle lights and turn signals for that price?

The big Streamlined shape is unwieldly and I no longer need it to be one big piece. It is time to cut it up into smaller chunks.
I also mounted the Prius headlight into a right angle flat so I can mount it correctly. The Prius light is really big! Will there be room for the front wheel? I have taken out a really big chunk from the foam for the light. Right angles and the laser line are my references so all the pieces can go back together correctly.
Here we are, roughed out. The top has been cut off at the plane of the fork head. The foam has been glued to fresh plywood. Everything is set at right angles. The Prius light looks promising. The next job will be to skin this with body putty then grind and sand it to perfection. Then I will duplicate the other side. I'll do all this by hand because it is easy for me. I have done this so many times.

My plan is to vacuum form the nose in two pieces, right and left. This would be the left side. Shipping big parts is always a problem. Now is the time to be addressing these problems.