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Discussion Starter #1
It appears that on many bikes a windscreen angle of 60 degrees is optimal for preventing wind buffeting at speed.

Two motorcycles that have this or very close to this are the HD Softail Heritage Deluxe and the Indian Chief Vintage. Both have very quiet wind management.

Note that both have open screens without fairing surround part of the screen.

Without the above a double windscreen, as offered by MadStad for many models, works well.

They also offer single screens for many models that allow adjustment to the 60 degree attitude.

YRMV
 

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Discussion Starter #2
Well, I'm going to try and adjust my K12RS screen attachment so the screen is at 60 degrees...


AND


Is moved forward, away from the headlight/fairing by a couple of inches.


MadStad doesn't make a kit for the '02 K12RS.


A follow up post is planned.

:glasses
 

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Discussion Starter #3 (Edited)
So the sport screen in the high position is at ~ 53 degrees.

And there is insufficient clearance from the headlight/fairing to allow theoretically optimal airflow smoothness.

A bracket will be made between each pair of the upper and lower windscreen attachment sites with the brackets extending beyond the upper attachment sites.

Then a pair of secondary brackets will be attached to each primary bracket.

The lower pair will extend at a 90 degree angle.

To move the screen forward 2 inches, the lower secondary brackets will be located 1.4 inches from each windscreen attachment site creating right triangles with 2x2=4 and 1.4x1.4=2 and 1.4x1.4=2 such that the hypotenuse squared equals the sum of the two legs squared.

To achieve an attitude of 60 degrees, the upper secondary brackets will have longer lengths to move the upper screen forward relative to the lower screen. The lengths will be determined after attaching the lower screen brackets to the frame based, moveable, screen attachment arms.

Bolts and nuts will secure the plywood to the screen attachment sites and the primary and secondary brackets to each other (allowing for initial adjustment of the prototype as needed), and the secondary brackets to the frame based, moveable, screen attachment arms with the OEM, BMW pop-in plastic pins.

The initial prototype will be of thin plywood pieces.

Testing results to follow....

:glasses
 

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Discussion Starter #4 (Edited)
Windscreen Buffeting and Screen Angle.

Got the extended brackets attached to the sport screen.

The screen angle was adjusted to an attitude of 60 degrees as measured half way up (the screen is slightly convex in the vertical axis).

A test ride this afternoon had a lot of buffeting.

My impression is the gap at the bottom of the screen is not large/high enough.

So the next test was after inverting the primary brackets.

This change resulted in raising the screen by 2.8 inches while keeping the attitude at 60 degrees.

The follow-up test ride indicated reduced buffeting but still less than optimal.

The apparent flaw is the headlight produces laminar flow that passes over the gap beneath the screen as the bottom of the screen. The screen does not protrude sufficiently forward of the headlight to capture air coming up off of the headlight.


:glasses
 

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Discussion Starter #5 (Edited)
Windscreen Buffeting and Screen Angle.

Success!!!

Last prototype iteration significantly reduces buffeting and wind noise while providing good rider wind protection.

Components include BMW tall (touring) windshield, aluminum stock (1/8 x 3/4 inch aluminum flat bar), hex bolts, aluminum washers, nylon lock nuts, and BMW windscreen-snap-in-quick-release pins.

At this stage, the upper-secondary brackets are fully extended so there is no windshield attitude adjustment for a steeper angle. Current angle is less than 60 degrees.

Longer upper secondary brackets will be installed.

Test results to follow....AGAIN

:glasses

And DIY specs!
 

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Discussion Starter #6 (Edited)
Not much improvement with the longer, upper, secondary brackets.

Will tried a pair in between the first and second lengths.

Better than with the longer brackets but maybe about the same as with the shorter upper brackets.

Evaluation is taking a while as I often take a long ride when testing different configurations.

The current components may stay at the same dimensions with further testing just of different windshield angles.

Comparison is complicated by wind strength/direction, humidity, and air temperature. So it's important not to make too many changes at one time between test runs.

:glasses
 

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Discussion Starter #7 (Edited)
So as cold weather approaches, the windshield protection will need to be higher.

My double windscreen design will be assembled with specs to follow.

Components: OEM tall windshield; OEM sport windscreen; BMW windscreen-snap-in-quick-release pins (4); thin aluminum angle iron stock (create custom angle brackets connecting the tall and sport windscreens), 8mm hex head bolts (4); 8mm nylon lock nuts (4).

I have assembled and used this before with temporary parts. It results in the windshield being ~ 4 inches above that of the OEM tall windshield and works well at all speeds.

As the double windshield adds weight, the sport windshield will be shortened by removing a top section from the sport windshield.

The double bracket system described above may be of use on the OEM tall windshield mounting to the front of the OEM sport windshield.

:glasses
 

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Discussion Starter #8 (Edited)
Best Windshield for Warm Weather--None!

If you want clean air flow, the best windshield for my K12RS is none!

:devil:

This is true for all speeds I've tested up to 80 mph.

I would not try this at higher speeds but someone else is welcome to.

YRMV.
 

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Discussion Starter #9 (Edited)
Drilling Lexan Windshield

The BMW windshields are made of Lexan polycarbonate.

When creating a "Double-Windshield" to lessen wind buffeting, you may need to drill some holes in the leading or trailing windshields.

Here are some tips for drilling Lexan and other plastics:


1. Drill bits (use one of the following):

a. Use a step drill bit.

b. Grind standard drill bits to a sharppoint bevelling the point (presents less cutting edge as material is started and entered.

c. Use diamond coated bits made for drilling plastic.

d. Start with a very small drill bit and gradually increase the sizes as you make the hole larger.

2. Avoid heat build-up as this will melt the Lexan and cause the bit to stick and the Lexan to chip and crack.

3. Use Dawn soap as lube/coolant.

4. Use low RPMs.

5. Secure Lexan with a clamp.

6. Backup Lexan piece with wood (allow for depth of penetration, especially with step bit).

7. Keep bits cool during drilling.

8. Smooth the edges of the hole, both sides, to reduce chipping/cracking with use/load.
 

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Discussion Starter #10 (Edited)
Up and forward Sport Windshield...

Another iteration tested today with good results. This time the sport windshield was used alone.

Components: OEM sport/short windshield; BMW windscreen-snap-in-quick-release pins (4); 1/8 x 1 inch flat aluminum rod, 8mm hex head bolts (4); 8mm nylon lock nuts (4); 1/4" hex cap bolts (4); 1/4" nylon lock nuts (4).

The brackets result in the windscreen being raised and moved forward when attached in the "high" position.

I'm planning on adding a small, trailing, supplementary "screen" to see if a double windshield configuration will produce even cleaner air.
 

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Discussion Starter #11 (Edited)
And yet another iteration of the double windshield configuration to be tested today.

Touring screen mounted on front of sport screen with sport screen in low position, touring screen raised up and forward about 1 inch such that its lower edge extends beyond the upper edge of the headlight and even with the bottom of the sport screen.

I'm beginning to feel like I'm tilting at windmills (windshields).

Obviously my posts are a personal record of the different configurations and results for my future reference.
 

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Discussion Starter #12
Another iteration of the double windshield...

Touring screen mounted on front of sport screen with sport screen in low position, touring screen raised up and forward about 1 inch such that its lower edge extends beyond the upper edge of the headlight and even with the bottom of the sport screen.
Tested yesterday on a ride to the Hopewell National Historic Park in Ohio (free admission, museum with burial artifacts, recreated 22 mounds on original sites).

Double screen does better in the high position.

While the double screen adds weight, the lack of buffeting makes the bike more aerodynamic and probably get better gas mileage.
 

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Discussion Starter #13
Tested yesterday on a ride to the Hopewell National Historic Park in Ohio (free admission, museum with burial artifacts, recreated 22 mounds on original sites).

Double screen does better in the high position.

While the double screen adds weight, the lack of buffeting makes the bike more aerodynamic and probably get better gas mileage.
Added winglets to the trailing shield and air management even better.

Adjustable winglets may allow use of the double shield even in hot weather.

Will have to wait to test that one.
 

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You're quoting yourself and then linking to your own thread and then that thread links back here but there is still no picture.

This is really confusing.

All of it.
 

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Discussion Starter #18 (Edited)
See picture at the link listed in post #16 above.

It's just a thumbnail.

Point and click the thumbnail for a full size picture.

Sorry for your confusion.
 
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