The Search for Fuel Economy

Pages from a Designers' Notebook

Dec.19, 2008

The goal: 100 mpg at 70 mph, into a 20 mph headwind, with four bags of groceries.
Chap. 23: Getting my feet in and out

All this time, I have been riding without floorboards. My feet have been resting on the engine radiator supply pipes. Once, while riding on wet grass, I had to get my right foot out fast to keep from slipping over. I almost didn't make it because my foot snagged for a fraction of a second on the junk inside. It was time for floorboards.

"Christmas Tree" push-in fasteners made it easy to take it apart

It is easy to work on: just peel the skin back
I enlarged the opening 2" for my leg to stick out and added aluminum strips behind the yellow plastic for structure and began work on a flexible door.

My plan all along has been to not use any outriggers to hold me up. My plan has been to use flexible, lightweight plastic foam for a smooth door. Such a door must be:



Rattle free

Not more trouble than it is worth

Fool proof

Absolutely non-impeding

(It must not slow down our reactions even by a fraction of a second or we might fall over)

Whatever works for the right side will work for the left side.

The first flexible, foam door

Hinged at the front on an angle, the rear is secured by magentic cabinet latches. It opens up and out, the same angle of my leg. Looks good, right?

It was unridable.

Here is what happened: I could easily poke my foot out to hold myself up. Overpowering the magnetic latches was easy. Motorcyclists know that we need to be able to put our feet down instantly. A fraction of a second off and and we might fall over.So far, so good. But getting my foot back in wasn't so easy. The foam door was rough at the bottom and caught my leg. The sharp edge of the aluminum floorboard caught my leg, too.

We cannot be distracted like this.

The solution will be to round out the edges so they did not snag me.

I wrapped the foam door with the yellow polyethylene skin material, which is very slippery. Think of polyethylene as "poor man's Teflon." I placed it only where my foot made contact, since too much tended to make the foam door stiff, preventing it from bending. Then I wrapped the floorboard with a matching piece of yellow polyethylene. The opening is now very slippery.
I attached the yellow plastic "slip panel" with lightweight plastic screws ... the same screws that I used to fasten windshields onto my Windjammers. Lightweight... perfect. You will notice the little plastic handle I installed to pull it closed if I needed to. It turned out to be unnecessary. By tweaking everything, I got the door to naturally want to stay closed. If it didn't, I found that by tapping it out, the "spring-back" would snap it closed.

I was prepared to add a flexible tab, sticking out into the wind which might blow the door closed. Oddly, there does not seem to be any wind sucking the door in or out in this region. I don't know if the tab would work or not.

It is time for tuft testing to get some idea of what is going on with the air flow. This will make a good movie. Next time.

Well, it ain't beautiful, but let me describe the ride

This is my first choice of machines to ride. I can carry lots of stuff. It is warm and comfy. But the little slip on the grass worries me. I have totally covered over the right side to make it streamlined and there may be a problem with that.

It turns out that we riders sometimes need to hang outside the area of our motorcycle.

I of all people, should have remembered this. Here I am outside Aspen in 1975, at Woody Creek Raceway, on my Rickman. Obviously, there are times when we need to hang outside the bike. We cannot do this with the sides closed in.

I am beginning to think that I will have to make the sides flexible in the area where we need to hang out.

Before I tear it apart, I will take a long trip to check mileage.

Hanging out... we can't do this on an enclosed bike

On one early trip with the right side foot door, it rained while I was inside running errands. On the way home, the inside of the cockpit began to fill up with mist. Was it coming from the front wheel? In a few miles, the cloud was gone... but it was still raining. Of course, the mist was steam from water burning off the engine. In later rides, I noticed that I could smell burning rubber which must be from the Helix' CVT drive belt.

The right side door had changed the internal airflow and engine smells were now being drawn forward. Not much of a problem but maybe I can keep it in mind as we progress.

This is what I see when I ride this thing. Most of this complication is to connect the rear streamlining with the front streamlining. I am beginning to wonder if this requirement is becoming "More trouble than it is worth."

My view of the cockpit.

More observations:

Because most of my riding has been around town, running errands, mostly stop and go, mileage is unchanged. Streamlining has no affect on mileage in these slow conditions. I have been counting stops and goes and it turns out that my typical "errand riding" averages between one to one and a half complete stops for every mile ridden. This must be why around town mileage is always worse than highway riding. Just as soon as we get up to speed, we have to slow down and come to a stop.

My next report will include a long, 70 mph road trip and tuft testing. I will put tufts inside and out.

In the mean time, this is the season when we celebrate the birth of Jesus our Saviour. I hope you have a wonderful Christmas.

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This page posted Dec 19, 2008