125CC sufficient (for aerodynamic custom tadpole trike)?

[Christ]

The average street bike (that I've been looking at) has a Cd close to that of a full-size pickup.

[beatr911]

Doesn't Cd consider area though? Because motorcycles are comparatively small it doesn't take much drag to bring the Cd figure up pretty high. The total drag though is the number to watch.

Interesting article on sportbike aerodynamics. Note that airspeed is 62mph.
Sport Rider-Testing Suzuki Hayabusa and Kawasaki ZX-12R aerodynamics in the wind tunnel

"Eight years ago, when Kawasaki engineers were designing the original replacement for the ZX-11, the prototype resulting from wind tunnel testing was almost a carbon copy of the Hayabusa--only the company figured it was too ugly to sell. And a Kawasaki engineer has confirmed the ZX-12R was in fact "neutered" to a lower top speed in its final stages of development. "

I hope we can redefine what is "ugly" and not "neuter" our motorcycles so that they can become aerodynamic.

[thatguitarguy]

Cd is just the co-efficient. CdA brings area into the equation, and yes, total drag is the thing that matters. "Average" is pretty subjective due to styling differences between bikes. I don't have the science handy to back me up, but I'm pretty sure that my tourer isn't as draggy as a Harley with no windshield or fairing, and I'm pretty damn positive I'm not pushing as much air as a pickup truck.

What matters to me on that vehicle is smiles-per-gallon.

[The Atomic Ass]

Originally Posted by Christ

How much does your R1100 weigh? How's the aero on it? about 17 HP is all that's really needed to go 70+ comfortably in most all situations.. ask Craig Vetter.

It's a LOT less than that. My Ninja 250 hit 26hp on the dyno, and managed 104mph. It goes along fine at 7.5-8K at 70, (I don't remember the exact revs) which has about 14hp according to the chart, and accelerates rapidly when WOT is applied at that speed.

[Christ]

How does the 'Burg do?

[The Atomic Ass]

Originally Posted by Christ

How does the 'Burg do?

Not so much anymore. I reached a peak of 81.5, restricting my speeds to 40-45 indicated, (10% optimistic is the consensus), which after modifying my weights for quicker gear changes and higher ratios in the transmission that equated to 4K. The lack of a manual clutch hindered coast down.

That engine is nice, though. LOTS of low down torque. The numbers I most often hear, as I've not had it dyno'd nor have I seen an actual chart, put the HP peak at 5.5K, and it lays down around 30 at the crank. The engine is tuned for torque, and torque it makes a'plenty.

This engine really has more to offer than the Burgman chassis and transmission has to handle, I wish I could transplant it into the Ninja frame. It could stand to be geared for 4K at 60mph in top gear, were it not connected to so lossy a transmission. I think, doing the same duty as the Ninja is currently, I could see 90mpg.

Anyway, wheel bearings, and an engine main bearing that looks bad but still goes for some reason has me side-lining the Burgman for right now. Hence why it hasn't been filled up in 2 months.

On the other hand, check out my latest tank in the Ninja, you'll really like.

[Christ]

Here's an idea that I found that's actually being produced, and comes in 50 and 150cc versions. They claim 70-80 MPG.



I'd like to do something similar, but a little longer and more streamlined. I've decided that due to it's limited use in the area that I'll eventually be living, it should be OK with a top speed of 55 MPH, and no freeway capability. I'll probably put a moped/scooter plate on it, so that anyone I know with a driver's license can operate it.

[Christ]

This thing is pretty slick, too...

[Christ]

I'm thinking that I'll rigid mount the rear tire, so that I don't have to deal with a swingarm and suspension... this one doesn't need to be convertible from a bike to a trike, so that's less weight that needs to be there as frame sections. Hard mounting the rear wheel makes it easier to build a frame around the driveline without trying to build into the mono-tube frame that's already there, and leave the mono-tube frame and related parts intact for use on my TwinStar, should the need arise.

Man, I'm hoping this project gets off the ground once the TwinStar is running (Which should be fairly soon, actually. It only really needs a battery at this point, and to finish the handle bars and seat pan.)

[Frank Lee]

Yoosta hava Honda Big Red trike on the farm. Man I loved that 200 or was it 250cc engine!!! I always thought it would have made an excellent basis for a street machine; lots of power and it seemed very easy on gas.