> Anybody up to speed on Excell
>
> How do I subtract a couple of times formated
> as 3:33:53:454?
>
> hours:minutes:seconds:hundreads of seconds
>
> Paul Lamar ...No rotor no motor.
Hi Paul,
I can't say for sure if Excell is the same, but in the OpenOffice
spreadsheet I can format the cell as HH:MM:SS.00 When I subtract one
cell from another, it just does it. I notice you have 3 digits in the
last group. Did you mean thousands of a second?
You might consider donwloading OpenOffice. Version 2.0 is out. I'm
just now trying it. I have opened some fairly complicated spreadsheets
from Excell with OpenOffice 1.1 and 2.0 is supposed to have even
better comptatbility. The price is righ, and it runs on Linux as well
as everything else.
I've attached the spreadsheet in Excell format. You might load it up
and see how it responds in Excell.
Bob W.
Funny you should mention it. I am using Open Office :)
I thought I was the only person on here using it.
I figured they did things pretty much the same way as Excell.
Yes the time data is to the nearest 1/1000 of a second.
Here is the coast down data in zipped form.
The idea here is to subtract the the time increments.
Convert the MPH to feet per second 88/60 times MPH = FPS
Subtract the MPH increment.
Then calculate the instant decelleration (more or less)
in FPS per Second by dividing by the time increment.
Convert to G's by dividing by 32
Multiply the G's by 3300 pounds and that gives the drag
at that MPH number.
Plot the drag as a function of MPH.
There are two coast down data sets. One in each direction.
The zip file has the coast down data and some constant
speed data. I will get more constant speed data tonight
on my way home from the hangar.
Paul Lamar ...No rotor no motor.
Wow, what a mess. It would have been a little simpler if the time had
been in the HH:MM:SS.000 format instead of with the colon.
I imported the CVS file into the spreadsheet, cut the MPH and time
column into a new sheet called Calculations, split the HH:MM:SS data
from the thousands, converted the SS to seconds in a real number, did
the calculations as you outlined, and plotted the results. One
assumption I've made is that the actual time interval will never be
more than a couple of seconds. I haven't tested this to see what
happens if you are making these runs thru midnight.
I have included an OO 1.0 and an OO 2.0 version of the spreadsheet
since I don't know which you have. One other note, when I did the
graph, I got a message that said I had to sort the X data. I declined
to do so because I thought that might mess up the calculations. It
seems to have plotted anyway. This is just XY points, but it looks
pretty neat.
I zipped the files, but they didn't compress much
Bob W.
--
http://www.bob-white.com
N93BD - Rotary Powered BD-4 (projected engine start in November)
Custom Cables for your rotary installation -
http://www.roblinphoto.com/shop/
Great work Bob. Fast too. Thanks.
I think column H needs to be divided by 32 to convert to
G's deceleration. 4000 pounds of drag is a bit much.
More like 125 pounds of drag at 60 MPH --- 88 fps is 20 HP.
I am kind of disappointed in the scatter. Is that both runs
Bob? I think one way was slightly up hill and the other slightly
down hill.
Paul Lamar ...No rotor no motor.
Paul,
The whole problem with Excell is the last : between the seconds and the
1000this. It looks like Bob has already solved the problem this time. If you
do another run, can you save the time data formatted hh:mmm:ss.0000? Then
excell will work. If not, and you are going to do more runs, I'll figure out
the code to convert it for you. It isn't hard.
Chris
Unfortunately I think that time format was deliberately chosen
by the SAE in collusion with the EPA.
Is that correct Jay Horak?
I could write a DOS QUICK BASIC program to convert
minutes:seconds:thousands-of-seconds to minutes.xxxxxxxx
Not sure of the number of x's I would get :)
Paul Lamar ...No rotor no motor.
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