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-   -   pic: 1251 Prototype v 1.2 (http://www.chiefdelphi.com/forums/showthread.php?t=41805)

Tom Bottiglieri 14-01-2006 22:47
Re: pic: 1251 Prototype v 1.2
 
Quote:
Originally Posted by Andrew Blair
The size of the wheel has nothing to do with the RPM of them (Unless you say that their mass slows down the system). If we know the output speed of the Kit gearbox, and we know the ratio to the the wheels, we can, with some error, find the RPM of the wheels. Now, if we were looking for the linear speed from a reference point on the wheel, then wheel size would matter.
Who says the trannies are running at full power?

i_am_Doug 14-01-2006 23:17
Re: pic: 1251 Prototype v 1.2
 
EDIT: im now guessing your team number ;p 1251.

Stephen P 14-01-2006 23:25
Re: pic: 1251 Prototype v 1.2
 
Quote:
Originally Posted by tkwetzel
Well...I finally made it back to Chief Delphi after being away for so long.

The sprocket size should not matter at all to answer their question. They asked how fast the wheels were spinning, not the motors. With an angle and distance you need the size of the wheels and possibly height of the arc of travel to find the rpm of the wheels to launch one of the foam balls that far.

Without calculations I will guess that the wheels are spinning at 1,900 rpm.
You couldnt find out the rotational speed from just projectile distance, becausethis would require the assumption that 100% of the wheels energy is translated into the ball (a horrible assumption).

tkwetzel 15-01-2006 01:42
Re: pic: 1251 Prototype v 1.2
 
Quote:
Originally Posted by Stephen P
You couldnt find out the rotational speed from just projectile distance, becausethis would require the assumption that 100% of the wheels energy is translated into the ball (a horrible assumption).
That is not true. You could assume whatever efficiency of energy translation you want, but whatever number you use would be an estimate without knowing other information. You also have to estimate a few otehr numbers. But tehy gave you the angle and distance traveled.

Andrew Blair 15-01-2006 12:17
Re: pic: 1251 Prototype v 1.2
 
Quote:
Originally Posted by Tom Bottiglieri
Who says the trannies are running at full power?
Thats one of the easiest assumptions. They're running the motors straight off of the battery, so the speed of the output is defined only by the battery voltage. Its rather easy to say that they were running a fairly charged battery; most people don't run a battery to nothing and then use it to power a launcher. An easier assumption than the estimation of the size of those two sprockets.

Andrew Blair 15-01-2006 12:19
Re: pic: 1251 Prototype v 1.2
 
Quote:
Originally Posted by tkwetzel
That is not true. You could assume whatever efficiency of energy translation you want, but whatever number you use would be an estimate without knowing other information. You also have to estimate a few otehr numbers. But tehy gave you the angle and distance traveled.
You could, but the easiest assumption to use is the motor/tranny speed to the wheels. Problem with using the ball's throw is that you must estimate he distance, then the power transmission efficiency, then backsolve for RPM. Lots of error, though either way. it's hard to guess.

SpaceBoy2000 15-01-2006 15:06
Re: pic: 1251 Prototype v 1.2
 
Based on my team's prototype, 2885 RPM

EDIT: I'm assumming 8' wheels too there...
EDIT 2: Whoops, forgot to add in sprockets

pakrat 15-01-2006 15:52
Re: pic: 1251 Prototype v 1.2
 
Well, I dont have a guess, But i will say that thing looks pretty sweet. Have you guys looked at the difference between running 2 spinwheels on each side as opposed to one?

David Guzman 15-01-2006 19:20
Re: pic: 1251 Prototype v 1.2
 
A couple of more hints.

-The wheels are 8 inches
-We assumed that only 75% of the distance covered by the spinning wheel gets to the ball. We were looking for the speed limit.

It's too easy now. ;)

Dave

nehalita 15-01-2006 20:19
Re: pic: 1251 Prototype v 1.2
 
2560 rpm?
Wait... does 37 feet mean 37 feet horizontally?

Smithvillefirst 15-01-2006 20:23
Re: pic: 1251 Prototype v 1.2
 
From the video sound it sounds as if you need to grease the gearbox ours was the same until it was well greased.

Anthony Peck,
Integration Manager
Team 1806

David Guzman 15-01-2006 21:36
Re: pic: 1251 Prototype v 1.2
 
The gear boxes are greased but haven't been checked since last year. Most of the noise is coming from the chain.

Yes, 37 ft horizontally.

cire 16-01-2006 11:10
Re: pic: 1251 Prototype v 1.2
 
Looks like 1269 RPM to me

gear ratio * free speed of kit transmisson
3:1 * 423 rpm = 1269 rpm

edit - I estimated that the larger sprocket was 36T and the smaller one was 12T by looking at the picture.

Rick TYler 16-01-2006 12:14
Re: pic: 1251 Prototype v 1.2
 
I know I'm coming late to the party, but 1,250 rpm, plus or minus two weeks.

(Bonus if you recognized the obscure movie reference.)


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