wrongway
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posted April 13, 2007 05:22 AM
 Edited By: wrongway on 13 Apr 2007 06:31
aero drag
I graphed the aero resistance of a zx14 with a small rider and me on a my 14. I am wondering how much there would be with no fairing at all, since I have such a huge negative impact with the fairing.
  
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fastestbusaaround
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posted April 13, 2007 05:43 AM
How did you measure this? You use a wind tunnel?
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wrongway
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posted April 13, 2007 05:53 AM
I used the info from the data logger to calculate the drag from my runs at the maxton mile. then used that to calculate the Cd .
Roy
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flyboy
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posted April 13, 2007 06:45 AM
The difference at top end is approximately 25 mph.
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'There's more living in five minutes flat-out on a bike than some men have in an entire life'.
"The World's Fastest Indian"
One fast red ZX-14,
Three World and four National Land Speed Records,
One faster red and white Cessna Turbo 210
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shane661
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posted April 13, 2007 03:44 PM
Edited By: shane661 on 13 Apr 2007 16:55
I am curious as to how you were able to calculate this if they were two different bikes/setups, with riders of different weights?
With no fairing, the results would be very bad. Maybe just working on your tuck would help.
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wrongway
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posted April 13, 2007 07:50 PM
for my bike , I was able to calculate the drag on from the logged data. the drag numbers for the small rider was calulated fromt the info I saw from the 200 mph Brock's run. the number fit on the curve, so it should be really close.
I think that I screw up the aerodynamics already , being too large to hide behind the fairing. no fairing may not be as bad for me as it woudl for a small rider that could make good use of the fairing. I guess I just have to test it and see what kind of numbers I get.
Roy
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Ojref
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posted April 14, 2007 03:48 AM
Are your love handles flapping in the breeze?
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2006 Kawasaki ZX-14 Ninja, Red now with mo' Brock's in my lyfe
1991 Yamaha Vmax - Because I need a mule to carry the manhood
2002 Ford Lightning - Ford GT Aluminum block engined, 802HP 911TQ now WhippleCharged
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psycho1122
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posted April 14, 2007 06:15 AM
quote:
I am curious as to how you were able to calculate this if they were two different bikes/setups, with riders of different weights?
With no fairing, the results would be very bad. Maybe just working on your tuck would help.
Weight does not matter at top speed.
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You say PSYCHO like it's a BAD thing!!
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shane661
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posted April 14, 2007 06:20 AM
Edited By: shane661 on 14 Apr 2007 07:20
quote:
quote:
I am curious as to how you were able to calculate this if they were two different bikes/setups, with riders of different weights?
With no fairing, the results would be very bad. Maybe just working on your tuck would help.
Weight does not matter at top speed.
I am more interested in what data is logged to compare the drag, and what constants it uses. If the acceleration/deceleration rate of the bike is used at all, then weight would be an issue. Not to mention weather conditions at the time, and bike setup issues.
While one may say that "weight doesn't matter at top speed", the reality is that the heavier you are, the less quickly the bike will accelerate...and that is an issue at a one-mile event like Maxton.
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shiphteey
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posted April 14, 2007 07:16 AM
Edited By: shiphteey on 14 Apr 2007 08:19
While I can't say with 100% certainty you can expect a pretty big chunk of MPH taken off your speed.
20-25 mph seems about right if you have them both geared the same (meaning the naked bike is geared too tall for 1 mile compared to its faired set-up).
Best speed I have run @ Maxton is 202.9 with a fairing and 188.86 w/out.
However, gearing was altered because I knew I would be going slower. Also, my naked run there has the benefit of a more aero/lighter pipe and lighter wheels.
I will be running there in May WITH the same pipe and wheels and fairing so I will be able to follow up with you Roy on the difference. I'm guessing I'll run 205...so compare that to 188.8.....
Again I've heard as little as 10 mph and as much as 20....25 seems to be the upper limit.
Sounds about right even for the fastest of speeds. Jason McVicar has gone 236? or something naked, fastest turbo busa w/a fairing is about 260-261.
Did you have an MPH goal or were you just doing this for scientific purposes?
Oh, and Psycho is right, but as Shane pointed out Maxton is a 1 mile venue....hell if I could gear tall and spray only in 6th would end up with a faster speed.....1 mile is long....bu not long enough for MOST vehicles to TRUELY capture their flat-out top speed. Go -1 in the rear of most bikes and give em another 1/2 mile and I'm sure you'll see a bit more MPH.....how much of course is the big variable.
A.
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BobC
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posted April 14, 2007 07:48 AM
Drag is crucial but if you want to achieve maximum speeds then don't forget gearing. When your bike with standard gearing reaches it's top speed, if it's not revving at peak power in 6th gear you could go even faster with a gearing change.
Remember that peak power on a 14 is around 10000rpm and that's about 190mph on 17/41 gearing. After that the power is reducing the faster you go.
____________
Candy Thunder Blue 2006 ZZR1400
Stock wheelbase
Max: 205.4 mph in 1.25 miles
2012 ZZR1400 in Golden Blazed Green
Brock CT Full System. etc
Max: 203.1 in 1 mile (so far)
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wrongway
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posted April 14, 2007 08:20 AM
quote:
I am more interested in what data is logged to compare the drag, and what constants it uses. If the acceleration/deceleration rate of the bike is used at all, then weight would be an issue. Not to mention weather conditions at the time, and bike setup issues.
While one may say that "weight doesn't matter at top speed", the reality is that the heavier you are, the less quickly the bike will accelerate...and that is an issue at a one-mile event like Maxton.
data logged was time. speed , RPM, and AFR.
Roy
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shane661
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posted April 14, 2007 08:50 AM
quote:
Drag is crucial but if you want to achieve maximum speeds then don't forget gearing. When your bike with standard gearing reaches it's top speed, if it's not revving at peak power in 6th gear you could go even faster with a gearing change.
Remember that peak power on a 14 is around 10000rpm and that's about 190mph on 17/41 gearing. After that the power is reducing the faster you go.
Good point. I think that you definitely need to look at your gearing and the power curve of the engine. And remember, that curve can change drastically with just bolt-on modifications.
For an event like Maxton, your gearing is pretty crucial due to the limited distance. Because of my weight, I run lower overall gearing than stock. As an example, for my bike to pull evenly with Shiphteey's, on the street, I need about 3-4 more teeth effective gearing. With a 5 tooth difference I am able to pull away a little bit. I am 100 lbs. heavier than him, with a similar bike setup.
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flyboy
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posted April 14, 2007 09:31 AM
Edited By: flyboy on 14 Apr 2007 10:37
quote:
I am curious as to how you were able to calculate this if they were two different bikes/setups, with riders of different weights?
With no fairing, the results would be very bad. Maybe just working on your tuck would help.
Same bike, same rider, same +/- 500 density altitude-
With fairings - two way runs - 195.109 mph average
w/o fairings - two way runs - 174.669 mph average
Weight has little to do with top speed. More important is the frontal aerodynamics and the number of sq. inches in the windstream. Obviously a smaller person will have less frontal displacement than a larger person.
____________
'There's more living in five minutes flat-out on a bike than some men have in an entire life'.
"The World's Fastest Indian"
One fast red ZX-14,
Three World and four National Land Speed Records,
One faster red and white Cessna Turbo 210
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shane661
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posted April 14, 2007 09:37 AM
Edited By: shane661 on 14 Apr 2007 10:48
quote:
quote:
I am curious as to how you were able to calculate this if they were two different bikes/setups, with riders of different weights?
With no fairing, the results would be very bad. Maybe just working on your tuck would help.
Same bike, same rider, same +/- 500 density altitude-
With fairings - two way runs - 195.109 mph average
w/o fairings - two way runs - 174.669 mph average
Weight has little to do with top speed. More important is the frontal aerodynamics and the number of sq. inches in the windstream. Obviously a smaller person will have less frontal displacement than a larger person.
But running at Maxton...with only a mile to achieve top speed...weight will affect things greatly.
If I am not mistaken, your #'s are from the salt flats, correct? How long of a distance did you have to achieve top speed?
As far as frontal displacement vs. rider-size, that also has a lot to do with the fairing design of the bike. Obviously with the miniscule fairings of a liter bike, a larger rider will take a larger hit in aero's than when on a land-yacht like the 14.
As shown in wind-tunnel testing, a larger rider can be more aerodynamic overall, than a smaller rider. It depends on the machine, and rider tuck.
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kspz3
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posted April 14, 2007 03:37 PM
quote:
quote:
quote:
I am curious as to how you were able to calculate this if they were two different bikes/setups, with riders of different weights?
With no fairing, the results would be very bad. Maybe just working on your tuck would help.
Same bike, same rider, same +/- 500 density altitude-
With fairings - two way runs - 195.109 mph average
w/o fairings - two way runs - 174.669 mph average
Weight has little to do with top speed. More important is the frontal aerodynamics and the number of sq. inches in the windstream. Obviously a smaller person will have less frontal displacement than a larger person.
But running at Maxton...with only a mile to achieve top speed...weight will affect things greatly.
If I am not mistaken, your #'s are from the salt flats, correct? How long of a distance did you have to achieve top speed?
As far as frontal displacement vs. rider-size, that also has a lot to do with the fairing design of the bike. Obviously with the miniscule fairings of a liter bike, a larger rider will take a larger hit in aero's than when on a land-yacht like the 14.
As shown in wind-tunnel testing, a larger rider can be more aerodynamic overall, than a smaller rider. It depends on the machine, and rider tuck.
Can you point to any wind tunnel testing with differant size riders - I would like to review the information.
Kevin
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kspz3
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posted April 14, 2007 03:38 PM
quote:
I used the info from the data logger to calculate the drag from my runs at the maxton mile. then used that to calculate the Cd .
Roy
What did you run at Maxton....... and what type of data logger did you use?
Kevin
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shane661
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posted April 14, 2007 05:17 PM
Edited By: shane661 on 14 Apr 2007 18:48
quote:
Can you point to any wind tunnel testing with differant size riders - I would like to review the information.
Kevin
Sport Rider Magazine, October 2006.
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wrongway
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posted April 14, 2007 07:52 PM
quote:
quote:
I used the info from the data logger to calculate the drag from my runs at the maxton mile. then used that to calculate the Cd .
Roy
What did you run at Maxton....... and what type of data logger did you use?
Kevin
I went 179, 2 other 14's went 178 and 184. I have an accel wide band O2 analyzer/logger.
Roy
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nightmare
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posted April 15, 2007 01:59 AM
What do you call a smaller rider? I am now 137 suited?
____________
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60ft 1.23
8th Mile 5.16
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wrongway
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posted April 15, 2007 05:52 AM
someone who can fit behind the fairing and add no frontal area....
Roy
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kspz3
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posted April 15, 2007 06:13 AM
quote:
quote:
Can you point to any wind tunnel testing with differant size riders - I would like to review the information.
Kevin
Sport Rider Magazine, October 2006.
Shane,
Can you post a copy of the article - I could not find it on their site.... or do you know of any links to it?
KSP
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shane661
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posted April 15, 2007 06:19 AM
I only have the magazine...in fact, I borrowed it!!
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wrongway
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posted April 16, 2007 07:43 AM
were there any Cd or Cx numbers given in the article?
Roy
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shiphteey
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posted April 16, 2007 08:42 AM
I think the point of that article Roy was that Lee Shierts was less aerodynamic on Dave O's Busa than Dave O was on his own busa. However, since Maxton is still somewhat of a 1 mile drag race, Lee will usually net a faster MPH than Dave holding all other variables constant because of their difference in LBS.
A.
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