Velomobiel: 214 mpg Recumbent Motorcycle (Honda 125cc with DIY aerodynamic fairings)

[PeterS]

Google Kamm effect .

[theo22]

Hi,

I'm Allerts college/friend. I'm als building similar bike like Allert.
I drove his several times, it's quite comfortable but very sensitive to sidewind.
It is not save to drive on a windy day, wich we have a lot here in Holland.
Probably that's why you don't see fully faired motorcycles more.
I'm planning to build mine more open like the german Evomoto
( see photo or Home )
This guy rides it allmost daily and does not have much trouble with wind.
He's getting about the same mpg as Allert.
Allert's fully faired honda has a better shape but more frontal area, Evomoto has a very small frontal area but not the best shape, this give the same mpg but is much less sensitive to side winds.
And you have to dress warmer.

Happy holiday's, Theo

[Frank Lee]

Thanks for chiming in; from Allert's writings I was under the impression that his bike was well behaved in x-winds.

[redyaris]

Originally Posted by theo22

Hi,

I'm Allerts college/friend. I'm als building similar bike like Allert.
I drove his several times, it's quite comfortable but very sensitive to sidewind.
It is not save to drive on a windy day, wich we have a lot here in Holland.
Probably that's why you don't see fully faired motorcycles more.
I'm planning to build mine more open like the german Evomoto
( see photo or Home )
This guy rides it allmost daily and does not have much trouble with wind.
He's getting about the same mpg as Allert.
Allert's fully faired honda has a better shape but more frontal area, Evomoto has a very small frontal area but not the best shape, this give the same mpg but is much less sensitive to side winds.
And you have to dress warmer.

Happy holiday's, Theo

What is the weight distribution on the front and rear wheel with the rider in place? The side wind problems are mostly due to the low mass of the bike and not I suspect due to the full streamlining alone. I think you need to do some dynamic testing as well to see what the weight is on the front wheel when going 80km/h. you may have a problem with lift at the front as well. the lower the mass of the bike the more critical is the design.

[PeterS]

Originally Posted by Frank Lee

Thanks for chiming in; from Allert's writings I was under the impression that his bike was well behaved in x-winds.

That is what his site says but it seemed hard to believe based on theory .The shape is so perfect aerodynamically that any apparent wind off the nose has to generate considerable side lift .Such seems to be the problem with a very good aero shape .

Spoiling that perfection seems the only way to get a rideable shape , something rideable in real world conditions .

[NeilBlanchard]

On cars, putting a vertical fin on the back can stabilize it in crosswinds. Maybe this would help?

[theo22]

"On cars, putting a vertical fin on the back can stabilize it in crosswinds. Maybe this would help?"

I have seen this done on fully faired recumbents. This can help to stop the effect of the vehicle wanting to steer away from the wind, but it creates more sidearea resulting in having to hang into the wind at an angle more and more chance of having the vehicle simply blown off its wheels. I have seen it happen.
Making the vehicle heavier helps a lot, but not for fuel efficiency. :-(

What PeterS says is sadly true. A very smooth aerodynamic shape will allways be more sensitive to x-winds. So I will go for reducing frontal area.

Greets, Theo

[NeilBlanchard]

Have you considered doing a reverse trike, like the Quest?

[theo22]

Originally Posted by NeilBlanchard

Have you considered doing a reverse trike, like the Quest?

Yes, ofcourse. And maybey someday we will build one. But getting a homebuild motorvehicle approved in holland is a long road.
Allerts Honda FF and mine are motorcycles with a licence simply stripped from all the plastic body parts and buddyseat, and then mounted with a new seat and fairing basically.
This requires no new approval, you can just do it and ride it.

explaining the police this is sometimes hard.

[BHarvey]

With regard to aero shapes being more sensitive to crosswinds-

In long range rifle shooting a bullet with a higher ballistic coefficient flies straighter, flies flatter and retains more momentum. It gets deflected LESS by sidewinds enroute to the target.

Now, two bullets with same BC, same velocity, but different weights-
The heavier bullet does shoot through wind better than the lighter one.

But since we live in the sub-sonic world I guess it doesn't matter.

I do remember all the MOTOGP racers saying they don't like the more aerodynamic fairings on their bikes. Makes them too sensitive to wind even though they have a higher top speed.