The Search for Fuel Economy

Pages from a Designers' Notebook

Mar 2, 2009

The goal: 100 mpg at 70 mph, into a 20 mph headwind, with four bags of groceries.
Chap. 25: Tuft testing:

How does the air flow?

The answer is blowing in the wind. The Freedom Machine ready for a video run.
The streamlining is still rough and incomplete. But I need to see how the wind flows before I complete the tooling and make Streamliner kits for you. Tufts are an easy and dramatic way to actually see where the air goes.

Over the years, I have developed an easy way to mass produce tufts. For you experimenters, we begin with:

Tuft-Making 101:

Carol donated one of her plastic cutting boards. I wrapped yarn around it about 1" apart
I found yellow electrician's tape to run the other way, about 2" apart.
With a razor blade, I cut one side and then the other
Peel the completed strip up and stick it to the body
I apply the strips everywhere but I am particularly interested in areas where I believe the air is not well directed.
I made black and white tufts for the windshield since I am not sure which will be the most visible.
Getting ready to see where the air really goes
Tuft testing: The Movie

It may be easier for you to see a lower res version on


A "straight tuft" is good. A "wiggling tuft" is not good. In addition to showing the tufts, this movie is a review of this Freedom Machine to date.

Unexpected turbulance on the side
A lot nicer than I expected
Can you see the problem here?
Pretty smooth
I have a few more experiments to do on the Helix. Of course, you will see it all here.

Lets review and summarize:

The Helix has been a good test mule to develop streamlining. It has about the right horsepower (13-17, depending upon who is reporting. Nobody seems to know for sure). It is quiet and comfortable, cheap and reliable. I have been able to buy a second one for side-by-side comparisons. Both are stock and unmodified. Only the streamlining is changed.

The streamlined Helix goes faster and burns less fuel. But streamlining has allowed the Helix to go too fast. It easily travels at 75 mph, into fierce headwinds. This is like going 90 mph and way is too fast for this scooter. Maybe it is the tiny wheels... maybe it is the lack of gyroscopic effects we would be getting from larger wheels. Maybe it is the minimal suspension. All I know is that I don't want to be on the freeways with big trucks at 75mph on this thing. Honda engineers simply did not make a Helix for such speeds and conditions.

Therefore, I am almost done with the Helix as a platform. I will keep riding it continue my experiments. But, I have gone about as far as I can on the Helix.

Finishing the Streamlining.

My plan is to go back to the original foam pattern and make all my changes to it. I am pretty happy with the Dodge Minivan headlights (from 2001 02 03 04 05 06) They fit and can be purchased inexpensively on EBAY. These lights fit the shape, have running lights and turn signals. They solve a lot of problems.

After finishing the existing left side, I will do the tooling for the opposite side. My plan is make molds of the front only (where the compound curves are) and then make tooling for vacuum forming.

Vacuum formed parts will be very light weight and be easy to ship. I plan to design this to be a Streamlin Kit - like model airplane kits of old. The windshield and mid sections can be made from sheet plastic. All this will be designed to be easily shipped.

Rest assured that the final shape should easily fit onto any scooter or cycle. Remember, the streamlined body we have developed here is for a person. No matter which bike it goes on, it will be just big enough for the person.

I like kits.

What is next?
Fred Hayes' Diesel Cedric Lynch's Electric bike-Photo courtesy Paul Blezard

Diesel or Electric?

I want a fresh start, beginning with the streamlining I have developed. I want better suspension. I want less horsepower. I want bigger wheels. I want a chain drive so I can gear it up. I want to make a streamliner kit so we can all easily continue the experiment

Now for more of your questions and my answers
From Don Feb 27, 09: 1. Are you officially done and over with the Helix?

Almost. I don't like riding with the semi trucks at 75 mph. The Helix is not made for the speeds that the streamlining has allowed. I will still ride it around since it is my favorite ride in the garage.

Have you got a sq ft measurement of the storage (ie. bags of groceries)

Nine (9) Cubic feet of storage space

You might be interested in the frontal area: Seven 7 sq. feet

Has the 15 lbs in the nose been sufficient or will you reduce to the 10lbs

I think is is OK for the Helix. Note that the front tire seemed to wear out - on the sides . This may be because of the extra lead weight at the front. I decided to over inflate the front tire. It doesn't seem to be wearing any more and it feels better. When I build on another plarform, I will put existing heavy things up front instead of adding extra weight. Did you read my story about Joe Petrali?

Have you done a mpg test without the inflatable boat tail? No

Is there any way to eliminate that section and create a blade like edge on the rear instead? Would that be prudent to do so?

I don't think so because 1) it I don't think the air will stay laminar if the tail is shortened. 2 - If I brought it to a point at the end of the bike, I would have no storage inside. The storage is very important to me. The tail allows the extra width. As far as I can tell, the tail has no adverse effect at all on handling!

From Andy: Hi Craig I am sorry that you have decided that this is the end of the line with the Helix, I have collected a small heap of Helixes (three) in the hope that at some point you would be making a body mould that I could fit onto mine. I really liked your other streamlined body shells (blowmoulded?) that you were offering for sale in two halves, left and right.

Do not dispair, Andy. I need this streamlined body, too. I intend is to make the very parts you need, not blow molded but vacuum formed (above)

At the time you said that this particular body would need a lot of extra plastic to stretch it to fit over a Helix, which would upset the wonderfully smooth skin of the original moulding.

My hope was that as a result of the Helix project you might end up with a blowmould shell Mk II that would fit more or less straight onto a Helix. However I am only one customer and of course the economics of mould making are that you make one mould and then you need a bunch of customers to amortize the costs. I understand that.

I also understand that with standard gearing the Helix does not like going much above 70mph even with the new body. Also that it is difficult to change the gearing and possibly even unhelpful, as you need the standard gearing to accelerate the machine away from standstill at a reasonable pace, and the bodywork may make it heavier.

However here in the UK at least I can see a future in which the opportunities for exceeding 70-75 on the public road are very limited. Our motorways (freeways) are covered with thousands of speed cameras and the number is increasing all the time. The monitoring techniques are becoming more sophisticated with more 'average speed' devices, which read your plate at one point and then again later on, and check your speed between points. So I believe we are much converging on the policeman's dream future where almost everyone drives inside the national speed limit (70mph) with gaps between vehicles set by forward-looking sensors. (This development in the real world is not reflected in motorcycle sales in which every second bike sold here is a high-powered fantasy racer). Therefore the target we should be looking for is to go up to 70 and then cruise at that speed with the greatest comfort, minimum fuel use and minimum wind noise. I find the Helix really comfortable once it has a backrest. (You have not mentioned wind noise in your reports so I don't know how well the new body achieves that.)

There is no wind noise. The only noise comes from the engine and CVT. There is no wind inside this thing. I hardly need a jacket or gloves. With my foam lumbar support, this thing is as comfortable as my Lexus car. And more fun.

I do hope you get a lot of messages from other potential customers asking for that Helix sized blow mould!

Finally, if I buy that mould from you I will not be taking the rubber tail, so don't mass produce that as well. I would just stop the body where it is and rely on the Kamm effect. I would exchange slightly less good aerodynamics for the ability to fit into a bike parking space (I know it inflates/deflates but that is another task). Personally for some limited experience I do not like tails that extend beyond the rear wheel because I suspect that, far from steering the vehicle into a crosswind, they have the opposite effect.

The truth is, it does not have the opposite effect. The tail makes the Helix more stable at speed. Did you read my story about Joe Petrali? There are a lot of myths out there. The tail makes it more stable at speed. Even though I don't need the tail in town where I hardly ever get up to speed, I leave it on because 1) I live in a small town and parking is not a problem and 2) I think it is cool. You are right about parking... I have to be careful so it isn't hanging onto the sidewalk.

Arnold Wagner's ecomobile runs without a tail for that reason (though this is my private opinion)

Well, Ecomobiles are long to begin with. (and really streamlined, too.. round at the front... pointed at the rear) The length is necessary to bring the rear to a point to keep the air moving smoothly.

Another factor is the effect of crosswinds while standing still. If you have a 90 degree crosswind, there can be a stressful moments as you have probably found when you are simply holding the machine up at a standstill.

This is a good observation, Andy. I have felt this too. Also, I am very careful about parking it so there is no possibility of it blowing over, which it did in an Illinois storm last summer.

I certainly get this on my Quasar. At several points in London traffic jams form on bridges, where there is a set of lights at the far end of the bridge. Once stopped in traffic, with not much room on either side, the wind blowing down the river really rocks any high-sided vehicle. It takes both feet to hold the Quasar up. Of course once standing still the wind force is proportional to the entire side area (including any tail) and all steering effects are lost.

Yep... I know what you are talking about

I hope you don't mind this long note, I am suffering from a cold and am probably slightly feverish. I hope to catch up with you when you visit the UK in August.

Best regards


PS I look forward to seeing which slightly more powerful vehicle you will use as a basis for the next stage. The Helix of course has a wonderfully low seat height, and a low seat is an important factor in reducing frontal area. Several people here have lowered the seats on the Yamaha TMax but I don't think that machine is imported to the US.

I look forward to my visit to the UK this summer, too.

Meet the "Pioneers in Feet-Forward Design"

The Helix has served me well. I will continue to ride it until I build something better.

Really, of all my bikes, this streamlined Helix is my first choice. It gets the best mileage at speed of any machine I have ever ridden. It is warm and dry inside. It carrys a lot of stuff. It makes me grin everytime I go.

It has spoiled me. But I can do better.

Master Index to the Last Vetter Fairing Story

This page updated Aug 19, 2009