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Author Topic: Team Go Dog, Go! Modified Partial Streamliners  (Read 682505 times)
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Interested Observer
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« Reply #3165 on: September 23, 2018, 05:16:41 PM »

Wobbly, what profile was used to determine the frontal area?  That is, what area was used to calculate the Cd?
Were there any comments about the tuft behavior?  Any tufts on the back of your leathers?
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stay`tee
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« Reply #3166 on: September 23, 2018, 07:06:27 PM »

This is interesting stuff Wobbles, thankyou for shareing  cheers

Yes, I would also be interested to know how the turf behaved,,

Regards the slot in front of the screen reducing turbulence,, on my 200+ passes (no slot) I have experienced slight pain in my ears, "vacume"
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First Australian to ride a motorcycle over 200mph at Bonneville,,,
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« Reply #3167 on: September 23, 2018, 07:36:44 PM »

The slot allows some air to go into the front of the fairing and it reduces turbulence behind the windshield.  It might reduce vacuum, too.

There is a picture of bike 7497 on Scooter's 2018 BMST website.  It is the faired version.  Bike 7498 is the naked version.  I am not sure if there are copyright issues with links so they are not attached.  Smoke tests showed power robbing eddy currents behind my lower back.  My back was not tufted so there is no verification from watching their behavior.  The higher tail top allowed by the earlier rules would have helped reduce turbulence in this area.

Frontal area is 6.45 feet and it is based on measuring a photograph of the front of the bike with me on it.  My helmet is at a typical position in the photo I measured.

My chest is on the tank and my head down in my dreams and in static situations.  In reality, the track edge marking has never been easy for me to see when my chest is on the tank.  I need to sit up like shown in Scooter's photos to get a clear view.       
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Old Scrambler
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« Reply #3168 on: September 24, 2018, 11:15:58 PM »

The CBR1000RR goes 4-mph faster when vents are added to the screen.............
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2011 AMA Record - 250cc M-PG TRIUMPH Tiger Cub - 82.5 mph
2013 AMA Record - 250cc MPS-PG TRIUMPH Tiger Cub - 88.7 mph
2016 AMA Record - 750cc M-CG HONDA CB750 sohc - 130.7 mph
2016 AMA Record - 750cc MPS-CG HONDA CB750 sohc - 137.7 mph
Chasis Builder / Tuner: Dave Murre
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« Reply #3169 on: September 25, 2018, 02:28:53 AM »

The CBR1000RR goes 4-mph faster when vents are added to the screen.............
Do you have any pictures or other information you could share about these?  It's something I've thought about trying but never gotten around to

Sent from my Nexus 7 using Tapatalk

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wobblywalrus
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« Reply #3170 on: September 25, 2018, 05:33:08 AM »

There are movies for the tuft testing and smoke with an excel data printout.  Possibly there is a way I can share these big files.  Maybe putting them somewhere and providing a link?  My next stop is Covington Indiana where my youngest boy is stationed.  Hopefully he or his wife will show me how to do it.

The staggered firing order crank with no counterbalancers worked great.  There was no excessive vibration up to the 8,900 rpm rev limit.  The same cam lobe profile was used last year and this year.  The peak power was at 10,000 rpm with a big dip in the middle of the power band last year.  The peak power was at 8,800 rpm this year with minimal dip in the middle of the power.  Plans are to split the differences in the cam timing and to raise the rev limit 500 rpm to 9,400.  This will give more power and have a power band with a dip in the middle, but not a big one.  This change, and adding a tooth to the rear sprocket to increase tractive effort, should optimize the engine.  Tightening up the leathers and lowering and narrowing the seat pan so I sit lower and tighter will help with streamlining.  The 150 mph goal seems realistic for next year.
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Stainless1
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« Reply #3171 on: September 25, 2018, 10:31:36 AM »

WW, does the motor pull well past peak power?  I have found that running closer to the engine rev limit in the lower gears places you closer to the powerband in the next gear and ultimately allows you to go faster. 
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Stainless
Red Hat 228.039, 2001, 65ci, MSA Bockscar Lakester with a little N20 
MSA Bockscar Lakester #1000 my fastest mile 245 and change, 84 ci turbobusa motor... but Corey's 233 MPH H/BFL record is still 3MPH faster than mine.
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« Reply #3172 on: September 26, 2018, 08:24:18 PM »

It pulls good up to the rev limit.  The engine was kept at full throttle in 4th until it hit the rev limit and then it was shifted into 5th.  This seemed to work best.  Like you say, the late shift resulted in placing the shift into 5th gear higher in the power band.
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Stainless1
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Robert W. P. "Stainless" Steele Wichita, Kansas



« Reply #3173 on: September 26, 2018, 10:15:10 PM »

I would "late shift" them all... the faster you get through the front part the faster you will finish
We generally shift near the rev limit in all but first gear, first will generally break traction at peak power and zoom to the rev limit.
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Stainless
Red Hat 228.039, 2001, 65ci, MSA Bockscar Lakester with a little N20 
MSA Bockscar Lakester #1000 my fastest mile 245 and change, 84 ci turbobusa motor... but Corey's 233 MPH H/BFL record is still 3MPH faster than mine.
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« Reply #3174 on: September 27, 2018, 05:40:33 AM »

WW, does the motor pull well past peak power?  I have found that running closer to the engine rev limit in the lower gears places you closer to the powerband in the next gear and ultimately allows you to go faster. 

It pulls good up to the rev limit.  The engine was kept at full throttle in 4th until it hit the rev limit and then it was shifted into 5th.  This seemed to work best.  Like you say, the late shift resulted in placing the shift into 5th gear higher in the power band.

I would "late shift" them all... the faster you get through the front part the faster you will finish
We generally shift near the rev limit in all but first gear, first will generally break traction at peak power and zoom to the rev limit.

OK, here are some visual graphics on why this works . . . . .



A/   It is the AREA under the portion of the bhp curve BEING USED, that determines how quickly a vehicle can be accelerated,

2/   Every vehicle requires some "range" of useable rpm, say 1500 to 2000 or so, rpm.   This range can be "less" when the gear splits are closer together.    But it is the "width" of the power band requirement, that defines the area under the curve for that particular engine or "tune",

d/   IF, the engine can be safely and reliably operated several hundred rpm above the peak power rpm, the above graph illustrates how a net "power under the curve" increase can be achieved.   By shifting beyond the power peak, the resulting rpm drop then is higher on the power curve, resulting in faster acceleration, AND, potentially higher speed.   UNTIL, power available = drag power being expended.   Ie, drag hp in all forms.

z/   Obviously, taller, wider power bands should always be the goal.    It's called "flattening the aspect ratio".   Sometimes it is easy, mostly though, it is a challenge on reasonably well developed racing engines.

Bhp increases produced, are roughly equal to to the square of dollars spent.   Early bhp gains are always the most cost effective.   Later expenditures can become very expensive per bhp produced.   Just the way it is . . . . . .

 cheers
F/b
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« Reply #3175 on: September 27, 2018, 08:58:10 AM »

"Bhp increases produced, are roughly equal to the square of dollars spent."

Man, I need to take a closer look at how I do things. My bhp increases have been equal to the cube of dollars spent.

John
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Stainless1
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« Reply #3176 on: September 27, 2018, 09:07:58 AM »

"Bhp increases produced, are roughly equal to the square of dollars spent."

Man, I need to take a closer look at how I do things. My bhp increases have been equal to the cube of dollars spent.

John

I think that is part of the ways to make more power.... cubic inches and cubic dollars  cheers
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Stainless
Red Hat 228.039, 2001, 65ci, MSA Bockscar Lakester with a little N20 
MSA Bockscar Lakester #1000 my fastest mile 245 and change, 84 ci turbobusa motor... but Corey's 233 MPH H/BFL record is still 3MPH faster than mine.
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« Reply #3177 on: September 27, 2018, 12:08:43 PM »

Well . . . . yeah, it can be a "cubic function".

Sometimes though, costs can be "somewhat" contained by good planning, ie, not having to have the pistons (or other expensive parts . . ) made twice, because someone "overlooked" some small, but important detail . . . . .

 cheers  Dead Horse  cheers
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« Reply #3178 on: September 27, 2018, 12:14:41 PM »

Another example.   Stage of tune . . . . .   Cam & cam timing change . . . . .



Should make you think . . . . . .

 cheers  Dead Horse  cheers
F/b
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« Reply #3179 on: September 27, 2018, 12:38:40 PM »

WW: do you log speed versus time?  And I'm curious which course you typically use.  I wasn't there this year but I seem to remember options of about 1 mile or 3 miles last year that most folks used.  Do you use the shortest track because of your air cooling?
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