Suzuki Burgman modification (aerodynamics + gearing mods)

[SVOboy]

Originally Posted by cvetter

Hooray! I am so happy to find this site and to see that there are others interested in fuel economy. I must leave right now but I want to invite all with street streamliners to my first "Gathering of Streamliners" to be held in conjunction with AMA's Vintage Days in Ohio at the end of July in 2009.

Thank you, I will be back.

Craig Vetter

Yay! The master himself is here! We all love your work, hope you stick around!

[MetroMPG]

Craig - I'll second Ben's enthusiastic welcome to the forum!

As you've seen around here, you've sure inspired a lot of people to learn more about aerodynamics.

If I were near Ohio at the end of July instead of on Canada's east coast, I'd definitely be checking out your Streamliners meet.

[cvetter]

Originally Posted by MetroMPG

Welcome to the forum, Jan.

Interesting to see your mods. I've been following Vetter's latest project, and he also didn't achieve the large improvement he was expecting.

If I'm not mistaken, he blames it partly on the CVT on his bike: apparently the old Honda he's working with can't be geared any taller.

Please keep us informed!

Vetter here: I am not truly streamlined yet. I am not close to my goal of 100 mpg at 70 mph, into a 20 mph headwind. I am at 64 mpg in worse conditions. What I am learning is that covering over the right side, at least, has made a dramatic improvement. If the Helix could be geared higher, I have the feeling that it could top out at 90 mph or so. No head wind has been able to keep me from going 75 mph! And that is as fast as a Helix might go in no winds! I am not discouraged but the Helix is not up to 75 mph. Gotta start over and am soliciting suggestions.

[Otto]

Craig, why not start with the human-powered designs as seen at the Battle Mountain HPV competition. Last I checked, they were up to ~81 mph on human power, which reportedly can muster only about ~1/2 hp. Obviously, to get such results necessitates very good aero design. That said, seems to me even those streamliners are not the final word on efficiency.

[Geebee]

I second looking toward the hpv streamliners, fit bomb bay doors for stopping etc.
This is the Varna Diablo, they dont come much faster on limited power.

[janvos39]

Every body who works on modifying a two wheeler for more speed or FE has some things to consider. For me it is important to have a daily transport to work which allows me to travel under not optimal weather conditions. furthermore I like to sit comfortable upright so that no back pain or things like that occur during the ride.
Although I admit for best FE the solution for the shape will be close to the HPV streamliner. This does not fit in my specification for comfort.
So far I reached more or less the goal of comfort. The choosen shape also starts to work for the FE.
Still to be done for better Cd is the front wheel streamlining.
I am not sure if I best cover the whole wheel or do additions to the front fender to improve the streamlining.
For the longer run I want to use a modified Suzuki Burgman frame that gives me a lower seat position and a smaller rearend for better closing of the back side.

On the gearing part there is the question what is best rpm at the cruising (75 MPH in Eu) speed. With the standard Suzuki Burgman 400 this is 6550 rpm (for the Suzuki Burgman 250 this is even close to 8500 rpm)

With the new gearing for the Suzuki 400 this will be reduced to 5100 rpm at 75 MPH in the additional overdive gear . See what that will bring on the FE.

[Geebee]

I dont understand how a more upright seat is more comfortable than say a 40 to 30 degree's from horizontal fully supporting seat is? such as:


Cheap fairing that allows 85 kph where a normal bike does 25 kph, above 30kph aerdynamics are everything.

[Otto]

Originally Posted by Geebee

I second looking toward the hpv streamliners, fit bomb bay doors for stopping etc.
This is the Varna Diablo, they dont come much faster on limited power.

Surely, we can make a better way to keep the machine upright at a stoplight than bomb bay doors to put your feet on the ground. Actually, the Swiss Ecomobile of ~20 years ago did this, with automatically deployed trainer wheels. Perhaps something even simpler can be devised, such as cable-actuated trainer wheels where you keep your feet inside the fairing and push on pedals to deploy the trainer wheels, rather than putting your feet down through the bomb bay like Fred Flintstone. Whatever.

Think of a typical bike kickstand, but with a wheel at its tip, extended by cable. Put one on each side of the vehicle so it cannot tip to either side. This also helps to elevate the vehicle to change tires, which is always the problem at roadside when a motorcycle tire goes flat, if said motorcycle lacks a center stand.

As to comfortable position, the semi-supine position has long been shown in sailplanes (and fighter planes such as the F-16) to be much more sustainable and comfortable, as sailplanes have to circle in extended high-G turns while thermalling. This also makes for less frontal area, meaning a lower drag profile for the vehicle. It also puts your head and eyeballs in optimum position to look around.

So, mehinks take the drive system guts of a Burgman, and install them in an HPV stressed-skin shell. On reflection, and given the vastly greater aero efficiency of a Varna Diablo or similar enclosed design, you'd need only a fraction of the power of a Burgman, and therefore a fraction of the Burgman's propulsive and fuel weight.

Such a vehicle could probably be built at less than ~50-60 lbs. It would be much safer than a normal bike, as those HPVs have been dropped at max speed, slid quite a distance, but left the driver unscathed. The Swiss Ecomobile, btw, reportedly suffered a blowout at ~150 mph, slid on its side, yet the driver was untouched. This without benefit of an airbag.

Surely somebody has tried one of those tiny direct-drive-on-tire aux bicycle engines on a Varna Diablo type HPV machine?

[Geebee]

This chart will give an idea of just how efficient the shells can be, Worlds fastest human powered trans Canada record
The best of them can exceed 60 kph on 150watts!

This calculator compares wattage to speed for different bikes and fairings one of the faired bikes should exceed 100 mph at 2000w!
Bicycle Speed And Power Calculator
So even allowing for practicality the machines in this thread have a long way to go.

[janvos39]

Thanks Geebee and Otto for info. It looks like if I use as much as I can from the shells of a HPV Cd will drop. It is more a question of how much can I change and still feel comfortable in full traffic, riding between cars in two lanes, which I find one of the big advantages of two wheel riding. Even with traffic jams I loose only some minutes. The back rest riding position is about 20 degree from vertical. This gives me a good feel in the high speed curves.
Maybe in a new design I can try a little more to gain some cross sectional area.