pic: 1251 Prototype v 1.2
 

Re: pic: 1251 Prototype v 1.2
 

Phase two of the prototype. The ball went 37 ft and was at a approximately 30* angle. First one to guess (calculate) how fast the wheels were spinning within 50 rpm will receive a prize from the TechTigers.


Here is video of it.

http://media.putfile.com/Prototype-v12

Re: pic: 1251 Prototype v 1.2
 

1290 rpm? Looks good guys.

Re: pic: 1251 Prototype v 1.2
 

My Guess is ahh 1050 RPM, I think I'm closer than I originally thought.

Re: pic: 1251 Prototype v 1.2
 

I'm not a mechanical guy, so it's hard to pick out those sprocket sizes, but I'll go with about 1665 RPM. :rolleyes:

Nice prototype, remember safety FIRST!
(How about fuse/breaker and at least a switch away from the shooter)

Re: pic: 1251 Prototype v 1.2
 

What kind of accuracy can you get over that range? Can you make 10 in a row into the goal?

Re: pic: 1251 Prototype v 1.2
 

My guess would be around 1800 but its hard to tell becuase of the sprocket sizes, my guess would be the big one is around 40-50 teeth probably maybe even 60 and the small one around 10-20ish maybe....

Re: pic: 1251 Prototype v 1.2
 

1750ish...

Wetzel

Re: pic: 1251 Prototype v 1.2
 

We made about 5 or 6 shots and they all hit the ground in about the same spot.

In my opinion it is very accurate.

Re: pic: 1251 Prototype v 1.2
 

Nice shirt kid in the background ;)

Re: pic: 1251 Prototype v 1.2
 

Very nice idea. I think it might be a winner.

About 1775 rpm?

Re: pic: 1251 Prototype v 1.2
 

I have to say this seems to be the best way to shoot because the 4 wheels help guide the ball to the needed derection and the constant motion allows balls to pass though as fast as need. seems to be going 4m/s? maybe.... so i don't know any calculations for that but......2,329rpms?

Re: pic: 1251 Prototype v 1.2
 

really nice guys !! working pretty hard huh...

Re: pic: 1251 Prototype v 1.2
 

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.

Re: pic: 1251 Prototype v 1.2
 

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.

Re: pic: 1251 Prototype v 1.2
 

Who says the trannies are running at full power?

Re: pic: 1251 Prototype v 1.2
 

EDIT: im now guessing your team number ;p 1251.

Re: pic: 1251 Prototype v 1.2
 

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).

Re: pic: 1251 Prototype v 1.2
 

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.

Re: pic: 1251 Prototype v 1.2
 

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.

Re: pic: 1251 Prototype v 1.2
 

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.

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

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?

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

Re: pic: 1251 Prototype v 1.2
 

2560 rpm?
Wait... does 37 feet mean 37 feet horizontally?

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

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.

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.

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.)