There has been a bit of confusion as to how far along in the project we currently are, time-wise. I thought that Week 2 was drawing to a close, but looking at the calendar, it would appear there is less time than I had anticipated. Guess who's not going anywhere for spring break!
 |
| April Fools'! But no really, your project is due. |
But before I start to detail the more unfortunate circumstances of our project, let's start with an update on what I've been doing: Reading.
My first resource has been a website selling the "heli-chair", a product which apparently emulates flying a helicopter... from a chair (on the ground). I didn't really get it either. But it sounds really cool.
 |
| For those of us too scared to fly, heli-chair won't let you die! Unless you fly it into your face or something stupid like that |
Regardless of that, I'm not here to advertise RC helicopters. But they did have a very helpful guide on their website detailing exactly how to calculate the lift capacity of a helicopter. From this, I was able to calculate the approximate lift force of our quadrotor (once it's complete).
A = Pi * r^2 = 121pi/144 [ft^2] (Now convert it to radians! Jk. No more math jokes)
A= 2.880 (Hope I got my sig figs right! That was a science joke)
PL=Power/A
OH WAIT! I don't know the power rating of my motors noooo. Calculations=chalked
So then I realized that my the listing for the motors we intended to use did not include the horsepower produced. Sigh... if only I could convert rpm to horsepower.
DO NOT WORRY, WISC SAVES THE DAY!
WISC being the online database of the Wisconsin Technical College System.
They have some very convenient presentations about torque, horsepower, and rpm.
(Adds to list of reach schools).
So,
2pi(torque)*(RPM)/33000=horsepower
2pi(r*force)*(750rpm/v)/33000=horsepower
2pi(5.5*force)*(750rpm/v)/33000=horsepower
2pi(5.5*@#$*& I DON'T KNOW THE FORCE)*(750rpm/v)/33000=horsepower
And once again I don't have all of the information I need. But can I calculate the force?
According the the Bureau International des Poids et Mesures (or International Bureau of Weight and Measures, for us Americans), force in newtons is calculated as:
kg*m*s^-2 (more math? ugh #algebra2skillz)
N=kg*(m/s^2)
N=.01725*(acceleration)
N=.01725*(OMGWTFBBQNOTAGAIN)
Needless to say, I didn't have the figure for acceleration either...
According to engineeringtoolbox.com, centripetal acceleration is calculated as:
ac = (V^2/r)ac = (2*pi*r*rps)^2/r <-woot linear velocity
ac = (2*pi*0.1397*8250/60)^2/0.1397 WAIT I ACTUALLY HAVE ALL OF THE NUMBERS? HALLELUJAH
ac=104270 m/s^2
Who knew pre-calc would actually teach me something applicable?
I'm going to take a second to sigh in happiness that I don't need any more equations.
Now then.
V = (2pi*r*rps)
V = (2pi*0.1397*137.5)
V = 120.692
Ac = (V^2/r)
Ac = (120.692^2/0.1397)
Ac = 104270 m/s^2
N = kg*(m/s^2)
N = 0.01725*(104270)
N = 1798.6575
T = N/1.35581794833
T = 1326.6217 ft/lbs
HP = 2*pi*T*RPM/33000
HP = 2*pi*1326.6217*(750*11)/33000
HP = 2083.8525
A = 2.880
PL = (85%)*Power/A
PL = (.85)*723.560
PL = 615.0259
TL=8.6859*PL^(-0.3107)
TL=8.6859*615.0259^(-0.3107)
TL=1.1812
Total=1.1812*4 motors
Total=4.7248 pounds of thrust
Total=2143.13 grams of thrust
Our quadrotor is projected to weight around 1800 grams at this point.
Woah, so you mean this might work!? Hooray!!!
And that's all folks--
Wait I have to talk about stuff, right.
So anyway, things aren't going too well.
We have indeed ordered almost all of our parts (WHICH COST A BOATLOAD OF $$$)
 |
| Not quite a boatload, but still a lot. IM ON A BOAT AND, no |
I have learned that I am a very impatient person. VERY impatient. Like, counting the seconds until my parts arrive... 863998... 863997... 863996...
We have started hacking out a CAD model, but it's very slow going... neither Pratik nor I has any significant experience in using AutoDesk (a drafting program) which means that it is a process that involves lots of trial and error, and constantly combing the internet for answers.
 |
| Probably used these 500000 times |
So basically this week I've been trying computer modelling, and reading a poop-load of formulas and physics texts. And angrily staring at my shipping status report.
If anyone has actually made it this far, through the impassable desert of equations, leave a comment!
G$
Resources
Wikipedia (of course)
Google (I can't find my graphing calculator, so this will have to do)
Hobbyking (for most of our parts and technical specs)
Heli-chair (thrust calculations)
BIPM (newtons, and not the fig kind)
Engineering toolbox (centripetal force and acceleration)
WISC (Torque and horsepower)
Pratik (last name expunged)
Shoutout to Mr. Hill for teaching linear and angular velocity
For more ROFLs
heylookiwroteabook.blogspot.com (especially this one)
sundrew.blogspot.com
anniedrawspeople.blogspot.com
I think the greatest thing about your blog is your voice. I mean honestly, you made calculating horsepower interesting, and we all know how boring the previous unit in pre-calc was. It's great how you manage to get your information across clearly, but still be funny and entertaining.
ReplyDeleteNow about the actual project. It sounds like you've got your work cut out for you, since a lot more obstacles have been put in your path. And I guess the only thing I can contribute to that is... good luck!
But in terms of what to post on your blog, maybe screenshot some of the programming/pictures/idon'tactuallyknowwhati'mtalkingabout from the CAD model and try to explain it so we can see a little more deeply into the process.
And again, good luck!
Hey G$,
ReplyDeleteYour blog is very interesting, especially because I'm interested in this type of stuff. It was cool how you made all your calculations interesting, and you put in little jokes throughout that made it entertaining. You are definitely on the right track with this project, so continue to examine the details of your project and hopefully learn more about the science of helicopters, or quadrocopters, or whatever they are. Have fun!