Author Topic: looking for suggestions for improved aerodynamics on a naked motorcycle  (Read 34815 times)

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Offline panic

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Re: looking for suggestions for improved aerodynamics on a naked motorcycle
« 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.

Offline speedrattle

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Re: looking for suggestions for improved aerodynamics on a naked motorcycle
« 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:



https://www.youtube.com/watch?v=zG8Htax6_Og
« Last Edit: December 16, 2018, 10:57:01 AM by speedrattle »

Offline tauruck

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Re: looking for suggestions for improved aerodynamics on a naked motorcycle
« 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.

Offline gowing

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Re: looking for suggestions for improved aerodynamics on a naked motorcycle
« 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 »

Offline gowing

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Re: looking for suggestions for improved aerodynamics on a naked motorcycle
« 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.

Offline speedrattle

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Re: looking for suggestions for improved aerodynamics on a naked motorcycle
« 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.

Offline speedrattle

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Re: looking for suggestions for improved aerodynamics on a naked motorcycle
« 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:


Offline speedrattle

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well, we'll see what the brandy-new aero wheels do in about a week, in loring, maine.



these are both front wheels off a 1990 GSX 750 suzuki, that came with dual disc brakes in the front. i have the front wheel mounted to mongrel triumph forks without a brake, and the rear wheel has a stock suzuki disc on one side and a sprocket bolted to the disc mounting bolts on the other.

the 17-inch suzuki wheels and goodyear front runner tires are set up to give a couple of inches of ground clearance at full bump, so frontal area is down a bit. the 2.5-inch tires also reduce the contact patch. dunno what effect the reduced volume under the chassis might have.

didn't have time to change the pipes. i'll make new ones for autumn that curve in and go under the motor.
« Last Edit: July 02, 2019, 05:29:54 PM by speedrattle »

Offline drc42

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well, we'll see what the brandy-new aero wheels do in about a week, in loring, maine.

And the results are????

Offline speedrattle

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Re: looking for suggestions for improved aerodynamics on a naked motorcycle
« Reply #54 on: September 18, 2020, 01:55:05 PM »
lol

i'm sorry.

this has been a hell of a year.

in july 2019 i blew up at the mile at 131 mph. one of the ARP rod bolts loosened up and let go.







the rod parting surface was . . . perfect, but three torques on the bolts were too many, even though i used a stretch gauge. never again.  once use only, from now on.

saved the billet crank with a 20-under regrind, new cases, new rods, new pistons, two new valves and a guide, some re-working of the combustion chamber on one side, then july was cancelled and back to the races in september 2020.

only 130 mph.

but nobody else at loring was fast either. the 200mph guys were shutting down at 175 because of a fierce cross wind that just wouldn't go away. i worked my machine pretty hard, but 130 was as fast as it would go this time around. so i'm back at the home ranch and looking for one percent tweaks.

but the daughter set a record in P/PP-250/4 on a 2007 ninja at 103:



and the other daughter came close at 102



but the chassis was perfect, hands-off at anything under a hundred. looking to clean up the rough bits now, oil tank and anything sticking out into the wind.
« Last Edit: September 18, 2020, 02:12:49 PM by speedrattle »

Offline speedrattle

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Re: looking for suggestions for improved aerodynamics on a naked motorcycle
« Reply #55 on: September 20, 2020, 05:49:11 PM »
acting on teh assumption that themotor is okay for the moment, maybe 60 horsepower, i'm going to clean up the chassis aero:

-- box in where the round blue oil tank is, maybe build a tank to fill that space and also fair in the front of the rear wheel, something like the old manx builders did.





except fold in around the front of the rear wheel . . .

-- bring the pipes into the centerline of the bike behind the front wheel, run them directly underneath and dump there. their length is fixed, really, two inches longer or shorter slow the machine 4 mph, and so i don't know what that turbulence will do directly under the motor.

-- tuck in everything that can be tucked in, cables in, number plates ditched (i'll just stick numbers on the box

-- anything else i can think of

a big lump in the front is my head. my helmet expeires after this coming year, and i'd like to try out a helmet that's built with aero in mind. lots of them claim turbulence reduction, and the one i have now is cvastly better than the bells i've been wearing for decades. but maybe something better is around.

dunno. but i have time to think

« Last Edit: September 20, 2020, 05:51:17 PM by speedrattle »

Offline speedrattle

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Re: looking for suggestions for improved aerodynamics on a naked motorcycle
« Reply #56 on: February 23, 2021, 06:21:31 PM »
. . . and install wheel covers. i can do the rear 100 percent, front needs to be 25 percent exposed, i think. easy to do because the katana wheels have a hole in each spoke.

Offline donpearsall

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Re: looking for suggestions for improved aerodynamics on a naked motorcycle
« Reply #57 on: February 23, 2021, 06:49:29 PM »
Speaking of wheel covers... Did you know that Amazon sells them? They advertise their wheel covers under the code name "17 Inch Pizza Pans". I have a 17" pan on the left and 18" on the right. Heavy duty aluminum too.

Don
550 hp 2003 Suzuki Hayabusa Land Speed Racer

Offline speedrattle

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Re: looking for suggestions for improved aerodynamics on a naked motorcycle
« Reply #58 on: February 25, 2021, 08:04:06 PM »
holy shit

ive been staring at those wheels trying to figure out the simplest way to cover them and i believe that you have the best answer. and they come in one-inch increments, too.

what are you using for fasteners on those? they look like a quick release
« Last Edit: February 25, 2021, 08:17:15 PM by speedrattle »

Offline donpearsall

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Re: looking for suggestions for improved aerodynamics on a naked motorcycle
« Reply #59 on: February 25, 2021, 11:41:01 PM »
The fasteners are merely stainless flat head hex screws. As you can see, I riveted reinforcement metal where the screw goes into the cover. The two sides are screwed into an aluminum threaded rod that spaces the covers so that they fit tight against the wheel. They will not slide around as the spacer rods go through a opening in the wheel spokes and are zip tied with SS zip ties. When I get to final assembly I will Locktite everything. I did static balance the wheel and it did not need much weight.

The oval opening is situated over the tire valve. I have an air hose extension that goes in there to fill the tire. Tape can go over the opening.

Don
550 hp 2003 Suzuki Hayabusa Land Speed Racer