1971 Experimental F750 Racer

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Someone is giving themselves way too much credit, after several days of being spoon fed .......... :lol: and continues to confuse with a simple chart.
 
pommie john said:
hobot said:
The chart must only show basic concept as not that close to reality. For instance it shows with .7 CoD it takes 50 hp to do the ton but we know we can sit bolt upright on about any C'do at 100 with less than 50 rwhp. CoD relates more to shape than frontal area so a dropped brick might hit the ground before a dropped faired cycle and rider. Also calculations of this sort are same fuzzy logic as engine power calculators.
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From a quick glance that chart shows CoD per Square metre ( of frontal area)

I imagine that you have to take into account the frontal area and apply that to the graph.
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The chart shows power versus speed and the lines are a cross product of frontal area and CoD (not CoD/Frontal area aka. CoD per Square meter).

Actually a pretty handy set of curves. If you know your rear wheel horsepower you can figure out and select cross product (colored) line that most closely matches your top speed. If you have a means to measure your frontal area, you can then calculate your CoD. There are always issues of gearing that you need to be cognizant of (ex are you achieving peak power at peak speed)

Hobot, as for fuzzy, it is precise. It becomes sensitive to error because the velocity is to the cube power so at speed things can swing wildly if your CoD or your frontal area are off.
 
!st off I want my tires to over whelm and twist the frame under me - rather than have frame resistance overwhelm my squealing conflicting tire patches, if that makes any sense to this knowledgeable bunch. Likely sounds crazy ignorant to those not knowing what they are missing out on a compliantly tamed isolastic C'do.

2ndly shape determines the slippery-ness ratio compared to a flat bluff brick and front area the multiplier of this slippery-ness ratio. Once shape is set by race rules or practical reasons then only thing left is make its frontal area smaller to gain any more. If only .5 mph faster advantage than the rest - it adds up over time with better mileage per fuel burnt. I think Peel will have to hit 160 pretty quick to stay ahead of my prey so drag and air pressure centers vs CoG on my mind. A flat face is more streamlined than basic motorcycle shape/clutter and reason the vintage full fairing had flat fronts, to pile up air to from its own streamliinging pressure hump. Also reason flat number plates on forks are considered streamlining feature on land speeder rules. The rear end is most dragy on most moving things, so exhaust plume aim can give detectable help.

I've put some thot into streamlining but not along the lines most are doing it.
Sperm whale flukes, bird feathers trailing edges and some wind mill design with vortex and anti-vortex generators with lift spoilers and rudder flaps and maybe some fur and carpet on helmet and jacket. I tease thee not.

Play with these for fuzzy math fun, The fuzziness part is not the definited equations but the generalized assumptions if not directly wind tunnel or roll down measured.
Power vs speed
https://www.google.com/#q=power+speed+calculator

Drag vs speed
https://www.google.com/#q=drag+vs+speed+calculator
 
A friend of mine was a senior research scientist at Aeronautical Research Labs in Melbourne and ran the transonic wind tunnel. Everything was done with models in a tube which narrowed down to give the velocity. Monitoring was done with pressure sensors. I think most incorporated pitot tubes.
 
Dances with Shrapnel said:
Someone is giving themselves way too much credit, after several days of being spoon fed .......... :lol: and continues to confuse with a simple chart.
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Thats funny !
Someone here was quoting dinosaur numbers.
And didn't know it /even denied it until repeatedly prompted !!
 
acotrel said:
A friend of mine was a senior research scientist at Aeronautical Research Labs in Melbourne and ran the transonic wind tunnel. Everything was done with models in a tube which narrowed down to give the velocity. Monitoring was done with pressure sensors. I think most incorporated pitot tubes.
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The problem with doing models is that the wind velocity has to be ramped up as the models get scaled smaller. ?
It needs something like a 600 mph windblast to simulate a 1/4 or 1/8 scale model in the real world, was it...
Which introduces its own problems
 
Rohan said:
Someone here was quoting dinosaur numbers.
And didn't know it /even denied it until repeatedly prompted !!
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So imperial units are dinosaur numbers. Your a laugh. So the best you got is demeaning remarks for a system of units and measures? Ha! :lol: :lol: :lol:

Who was lost until I spelled it out repeatedly that it was a reference from Phil Irving's and showed (reproduced the calculations and units were imperial (spoon feed) using imperial units. And me not knowing it / even denying it????, this is your construct of reality, I can assure you it is only yours. Clearly you were struggling to connect the dots and your statement quoted above is a case of projection if I ever saw one.

Sorry, didn't deny a thing. I thought you would pick up on the concept sooner so continued to spell it out but I was not concerned about it.

Dances with Shrapnel said:
Drag coefficient I referred to is from Phil Irving's book and probably some obscure imperial based unit, something like 0.0008. If you have his book, look it up. I am on the road so cannot help you in your quest.
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I am ok working in SI or imperial, seems someone was getting their panties in a knot; poor math skills? :lol: Couldn't even find the reference; fumbling around with the pages; forum member wakeup kindly spoon fed you. You don't even say whether you have the book or not; let me guess, Phil Irving is a dinosaur and you are so....beyond that.

I am still appalled at the dearth of reading comprehension and I can see someone here "struggling in vain".

Example: Your words.
Rohan said:
If someone reworks the aero so the drag coefficient goes from .40 to .30, and "0.0001 improvement yields a 12.5% reduction in drag",
does that mean they get a 12500 % decrease in drag ???
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Yeah, ah, ya getting close there, right 12500%

So after all the explaining we get:

Rohan said:
The penny has finally dropped.
You are using all imperial figures.
The coefficient of drag is different in imperial ??
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Bingo! A little round of applause for the gentleman. And how long into this thread was it before you realized? I see a light bulb just beginning to shine. I thought there was hope but I think the next phase, denial, has been reached.

It's all there to read.

Good day.
 
Have it your way then.
Your suddenly fluent in SI and Imperial, but couldn't even see where the problem was when it was initially pointed out the numbers were way below the current system ?
It was evident you didn't even have a clue what I was on about.
Even after showing Wiki for examples.

And some folks cast nasturtiums on Wiki's knowledge and integrity along the way there.
Now that was ????
 
Perhaps we misread each other. I was not concerned as I did not see it as a problem as it was clearly the imperial system, you know, Phil Irving, Tuning for Speed , feet per second (fps), pounds force (lbf), british iron etc...

Not suddenly fluent but a licensed and registered engineer with 30 plus years of professional experience so no, not suddenly. Furthermore, SI is not the "current system", it is a system that is gaining general world wide acceptance. To me it certainly appeared you did not know what was happening (remember, who was asking all the questions?) or were you all the time leading me down the path of knowledge.

Regardless, I continued to explain with the intention of enlightening you and others with the understanding that you really did not understand and you were struggling.

Nuff said.
 
A simple question about what system of units was being used in the discussion might have helped ? What throws me is the use of the minus sign in American thermodynamics compared with the British methodology. It turns whole concepts upside down.
 
thermodynamics is a whole another field - lets not throw more confusion into this.. !
 
acotrel said:
A simple question about what system of units was being used in the discussion might have helped ? .
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I rather suspect that no-one on this forum was aware that metric and imperial had different values for the coefficient of drag. ?
I have only seen them done in metric for some decades now, and metric values quoted. And Mr dws initially refuted the metric values.
And we seem to recall you rubbished the whole Wiki concept !!

So we all learned something...
 
Rohan said:
acotrel said:
And Mr dws initially refuted the metric values.
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My are we thick headed today. Please, please show me where I refuted this. I was in transit and presented much of this from memory - no errors.

And this from someone who:

Confused units on a simple graph. :oops:
Confused while asserting my math is flawed based on citing an unreal CoD value of 5 when I was clearly writing about 5 Sq Ft. :oops:
Gets spoon fed the exact reference including page number (Phil Irving - Tuning for Speed - pg 224) and gets full of himself because he can't find the relevant information in Phil Irvings - Motorcycle Engineering pg 224 or any other page. :oops:

Hey Rohan - wrong book! :lol: Need another clue? :lol:


Some people hit rock bottom and some just continue to dig. Keep them coming buddy :lol:
 
Wasn't it you that quoted 'Motorcycle Engineering' book as the appropriate refence.
And P224 in Tuning for Speed is 2 stroke ports...

Hey, we can only go on what we are being 'spoonfed'.
And if that is all wrong, where does that lead us.

If you were teaching this, I'd be asking for a different class....
 
It appears you have gone back and re-edited a number of your posts.
And P224 takes me nowhere in anything I own or have read. (Clymer versions - criticism noted).
So its tough to see where we diverged.
 
Rohan said:
It appears you have gone back and re-edited a number of your posts.
And P224 takes me nowhere in anything I own or have read. (Clymer versions - criticism noted).
So its tough to see where we diverged.
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The post where I introduced Phil Irving's reference titled Tuning for Speed is not edited. :oops:

Well I never new of the Phil Irving book titled Motorcycle Engineer; my library only has Irvings Tuning for Speed in hard cover. I could not have made up the title Motorcycle Engineering barring some unusual random neural occurrence that just so happen to cause me to type Motorcycle Engineer. You were the one who introduced a different title...in confusion. I know, I know, you saw the name Phil Irving and ran with it. :lol:

Nice try or desperate try. :lol:
 
I'm glad he has found a new friend to irritate. Do you live anywhere near him ? For God's sake take him to a race circuit and let him ride a real motorcycle. So far everything about him has been interpreted supposition.
 
Yes, we have dws ORIGINALLY POSTING
Dances with Shrapnel said:
Using your more common units of coefficient, reducing the coefficienct from say 4.0 to 3.5 yields a 12.5% reduction in drag.
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and its now been amended to - something less confused.... ?

Dances with Shrapnel said:
Using your more common units of coefficient, reducing the coefficienct from say .40 to .35 yields a 12.5% reduction in drag. Phil Irving presented a coeeficient of 0.0008 and I arbitrarily picked 0.0007 (net 0.0001) which yields the same percentage reduction. I have a hunch Irving may have combined a few terms; don't know for sure without digging into an old fluid dynamics text and studying it a bit.

So design or redesign a complete bike for 2" lower and maybe 5-8% reduction in drag or reduce the coefficient by 10-12 or more percentage points. It could be be as easy as adopting a different tuck in riding position or a modified tail piece.

Irving was pragmatic. Testing to measure results could/would be done on a flat out and read the tach.
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acotrel said:
I'm glad he has found a new friend to irritate. Do you live anywhere near him ? For God's sake take him to a race circuit and let him ride a real motorcycle. So far everything about him has been interpreted supposition.
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In case you hadn't noticed Alan, I'm quite happy to challenge anyone who quotes "facts and figures" which don't tally with common knowledge.
Its just that you seemed to be particularly good at quoting some semi-nonsense now and then, which a quick google would have shown as plain ole WRONG !
You don't need to ride a race bike to know this stuff, just have a half-functioning memory....
 
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