The Search for Fuel Economy

Pages from a Designers' Notebook

Freedom Machine
The goal: 100 mpg at 70 mph, into a 30 mph headwind, with four bags of groceries.
Chap. 33: New gears for the Helix

(The impossible just got possible)

This is what the Helix final drive looks like
Jan Vos of Belgium is well known in fuel economy circles as the machinist who made a new gear set for his Burgman to slow his engine down. He presented his work on ecomodder .

My Helix Streamliner project is stalled out because I need new gears. I don't know how to make them because I am not a machinist.

You can imagine my delight a couple of weeks ago when I received this E mail:

What a gear cutter looks like
Hallo Craig.

I still follow your progess with the Honda Helix. The looks getter better with latest modifications.I think you need for improvement of the MPG a higher gear ratio at least 20% higher than you are using now.I am willing to make that for you against a cost that you cannot refuge.I made a big jump in MPG with my Suzuki Burgman when using the new ratio.It will be spur gears, that is the only type I can make.What do you think?


Jan Vos
What did I think? "Its a miracle" is what I thought! Just how many people are there in world who can and are willing to do this? Jan and I exchanged E mails. All I had to do was send him a set of gears from a Helix and he would do the rest.

I knew where there was a set of gears.

My old friend, Ernie Buckler in Spokane, Washington is an eclectic fan of FF (feet forward) machines. He once mentioned that he had a spare trashed Helix engine. But the drive train was good.

He offered to send it to Belgium. It got there in 3 days! As I post this page, Jan is cutting new gears to slow my Helix engine down 20%.

Feb 19, 2010: Jan is making gears faster than I can put them up on my web page!


As of Feb 19, 2010
Feb 24, 2010

I received the gears today from the wire EDM shop. End of this week the gears go to a shop for hardening. Typically this takes a week and a half. When they are back they can be finished in one day.

Sharp readers will observe that Jan has made two primary output gears, a 34 and a 35. I don't know why. Not only that... I wondered how two different diameters could mesh together. He said either one would work and explained:

"It looks like you are suprised by the possibility of using both 34 and 35 teeth gear with the 16 teeth of the input shaft. I use the possibility of so-called positive correction on the tooth shape to match the clearance . This is only possible with official teeth cut machines. So not more noise for the 34 gear."

Regards, Jan

March 11, 2010... The new gears are here!

Carol is so excited! Thank you, Jan. Now I must finish up the Alcan Fairing on my KLR so I have something to ride when I take my Helix apart. Then I can swap out Jan's new gears and we will all see what happens. These new gears are designed to slow the Helix engine down by 20%. Since they are "straight-cut" we can expect them to be noisier.

March 31, 2010... Time to install the new gears

I am always shocked when I remove the streamlining exposing the little Helix powerplant underneath. There is nothing there! Over the years of development, I have made removal of the streamlining easy... 5 screws. Access to everything is easy. Not so the way Honda made it.

A couple of weeks ago, the Helix did not fire. No spark. I ordered a new starter/stop switch and installed it with the body off. It was harder to install than Jan's gears. But when I pushed the button, it started right up.

Swapping the gears was a whole lot easier than I had expected. Small parts dog, Willie, looks on
I chose Jan's most radical gear... the 34 tooth one. It will slow the engine down the most. I have great confidence in what my Helix can do, streamlined. Next step... button it back up and go for a ride. Stay tuned.

Well, it may not be today. The Helix does not fire again. I took it to my friend, Randy. He can make anything run. (He helped raise out two boys, too.)

The problem was "no spark." The problem was intermittent. Randy soon discovered we needed a new Pulse Generator. When it arrived, it started right up.


But just before replacing the streamlining, I checked again to make sure it started. It did not. Back to Doctor Randy who now diagnosed that the Ignition Control Module had failed. More waiting.

Dr. Randy and bad pulse generator
Many have suggested that I may have caused the problem by overloading the electrical capacity of the little Helix with the Prius headlights. Good thinking but, that was not an issue. Only one of the Prius lights is hooked up and it has the same 60/55 watt halogen bulb that was in the Helix scooter.

Finally, April 25, 2010, we were ready for a test ride. Just in case there were more ignition issues, I decided to do a shorter, 130 mile round trip from Carmel to King City. Same Highway 101... same awful winds. You will be stunned at the results. Click to Chapter 34

Master Index to the Last Vetter Fairing Story

Page posted Feb 17, 2010

Updated April 25, 2010