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Author Topic: looking for suggestions for improved aerodynamics on a naked motorcycle  (Read 5908 times)
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panic
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« Reply #45 on: December 15, 2018, 11:47:24 PM »

I agree, the teardrop requires greater transitional length to work.
IIRC the Kamm principle:
The rear extends back @ 14 degree angle until the X-area is 50% of the original cross section, then cut off flush. No radius, corner, reducing taper.
The flaw: Kamm uses the largest X-section of the car, not just the bike tail, so it can't be translated. If it work, it just reduces the drag of the tail, not the bike.
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speedrattle
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« Reply #46 on: December 16, 2018, 10:52:37 AM »

I agree, the teardrop requires greater transitional length to work.
IIRC the Kamm principle:
The rear extends back @ 14 degree angle until the X-area is 50% of the original cross section, then cut off flush. No radius, corner, reducing taper.
The flaw: Kamm uses the largest X-section of the car, not just the bike tail, so it can't be translated. If it work, it just reduces the drag of the tail, not the bike.

that seems to make sense. on a tucked-in rider, the slipstream detaches right about the middle of the rider's back. for the kamm tail to work, the air would have to remain attached to the rider all the way back to where the tail begins, else you would fair in to the rider's butt. not impossible on a partial streamliner, but harder on a naked machine:




« Last Edit: December 16, 2018, 10:57:01 AM by speedrattle » Logged
tauruck
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« Reply #47 on: December 16, 2018, 05:00:55 PM »

I did not know him well, but he was really nice and helpful to me.  My favorite memory:  I was in staging right behind him and had been struggling to get my 450 Honda above 120.  He asked what I was doing and I told him I had just geared it "too high".  I told him, "Don, dont fall down out there because if I cant get past 120 this time,  I am going to keep right on going and ride home to Colorado!"

He laughed and said, "Jim, I am going to go real fast, and if I fall down, I'd appreciate it if you would run me over right away."

My favorite pic is him sitting under his parachute sun shade, working on the single engine bike (which put up a very solid fuel record the next day).  Some folks don't know how tough those records we made were, back then.  First, you ran as hard as you could to qualify...and first thing next morning you made two more runs, back to back, with no repair time in between.  There were bikes that qualified ok, but didnt survive the actual record runs.

It was sure different.

He didnt fall down (close to 200) and my bike ran 124.65.  That was the day Bert missed a shift and spun the windings on his Indian's mag.  He and another fellow and I started up the mountain to strip "bell wire" from a plane crash magneto, but my little street bike couldnt make it up the silt.  They rewound the mag that night and my Dad stayed up all night watching. 

That week was a great experience for my Dad and I.  I had arrived home from Nam on July 17th and all you salt flats people yanked me right out of the war mentality, and planted me on the path to a better life.  Don is a small piece of the memory, but he was the right guy to meet, at that important moment.

Sorry for the long ramble...we get that way when we finally grow up and old.

Jim
👍👍👍👍👍
Great story. Thanks Jim.
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gowing
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« Reply #48 on: December 16, 2018, 05:58:40 PM »

Being a noob to LSR aero, but not totally lacking in analytical thinking,
I have a question:

In the Kolb 125 video, it looks to me like the helmet sticking up above the fairing is increasing turbulence.
wouldn't it be better to be tucked completely behind the windscreen?
would a taller hump on the leathers be a benefit?

If so..... why wouldn't they just build the bodywork tall enough to hide behind?
« Last Edit: December 16, 2018, 06:00:49 PM by gowing » Logged
gowing
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« Reply #49 on: December 16, 2018, 06:42:21 PM »

The rules state that streamlining is anything IN FRONT of the Rider that acts to guide the air around the bike. How about a nice belly pan that goes from the front of the engine to the rear where a batwing guides the air around the tire ?  NASCAR teams had lots of neat ideas such as oval exhausts and very wide flat bottom oil pans. Rules now do not allow anything. Much more fun in the old days .   LSL

I was wondering about rear wheel covers, do you think they might work better than 3 spoke?
I know that Ducati, and the World Superbike series have been testing them.
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speedrattle
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« Reply #50 on: December 16, 2018, 10:13:40 PM »

I was wondering about rear wheel covers, do you think they might work better than 3 spoke?
I know that Ducati, and the World Superbike series have been testing them.

some people running machines like mine use them



complete covers are legal for the rear, in front they have to leave 20 percent empty, i think

would be easy to adapt to the cast wheels, once they're fitted.
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speedrattle
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« Reply #51 on: December 16, 2018, 10:17:00 PM »

Being a noob to LSR aero, but not totally lacking in analytical thinking,
I have a question:

In the Kolb 125 video, it looks to me like the helmet sticking up above the fairing is increasing turbulence.
wouldn't it be better to be tucked completely behind the windscreen?
would a taller hump on the leathers be a benefit?

If so..... why wouldn't they just build the bodywork tall enough to hide behind?

i don't know why they left the helmet sticking up. if you look at the kolb video, there's quite a bit of turbulence all over close to the rider, maybe four inches everywhere. if they made the cutouts smaller all around there would be less of that. this 1950's triumph 650 goes 180, so far, and the rider is completely shielded when he's in position:

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