What's new
  • Please do not post any links until you have 3 posts as they will automatically be rejected to prevent SPAM. Many words are also blocked due to being used in SPAM Messages. Thanks!

Gallery Supersonic ping pong ball

BrainEater

Well-known member
Joined
Mar 19, 2007
Messages
2,820
Location
Calgary
Try it with a golf ball muhahaha

I can suggest crazy $IIi7 cause I'm miles away.

A golf ball would not move.

This only works because it's a ping pong ball.It's a thrust thing.This is pure physics.

When the vacuum is going it's about a 15 psi differential.A ping pong ball has a diameter of 1.57 inches.That's an area of ~ 3.8 square inches.15 psi X 3.8 square inches equals 57 pounds of thrust on an object that weighs 2 grams ! (yea my maths bad but...)

That over 10,000'G's of acceleration.

:haha:
 
Last edited:

IRQ Conflict

Well-known member
Joined
Mar 27, 2009
Messages
1,806
Location
Drayton Valley, AB
46g for a golf ball which is 23 times as heavy. I'm not sure but the outside circumference is close is it not? So 23 x 15 = 345psi or more properly 2.42 inches of mercury.

For you to get a golf ball to do roughly what you did with the ping pong ball it would take compressed air @ 345psi or a vacuum @ 2.4in mercury @ 0c. To get it supersonic, well that's a whole other ..ahem ball game.

I was thinking, we could rent one of these for an hour. :biggrin:
 

BrainEater

Well-known member
Joined
Mar 19, 2007
Messages
2,820
Location
Calgary
Ah shitballs !!

My Vacuum pump is only doing -0.75 bar right now......that ain't good enough.

The vacuum thang is very important in this experiment.The terminal velocity of a ping pong ball is really slow.Low mass , high drag.......The only way it'll go 500 mph is in a vacuum....

The vacuum pump is going in for service monday , but really it's not good enough......it's right on the cusp.......The first shot I did that worked was -0.82 bar.For this to work properly you really want -0.99 bar.

I'm messing aroung with making ABS c-d nozzles.

:thumb:
 

IRQ Conflict

Well-known member
Joined
Mar 27, 2009
Messages
1,806
Location
Drayton Valley, AB
I dunno. Maybe the trusty potato cannon would be a better/funner project?

Edit: I tried converting barometric pressure to inches of mercury with negative values. If you'll forgive the pun, it doesn't seem to add up. -0.75 bar = -22.15 inHg ?

Isn't vacuum better expressed as a positive rather than a negative? My brain doesn't want to go there I guess.
 
Last edited:

Father Fuzzy

Well-known member
Joined
Jan 7, 2012
Messages
502
Location
B.C.
Not sure what your doing Braineater(as usual)

but you got my interest(as usual)
Subbed!
 

BrainEater

Well-known member
Joined
Mar 19, 2007
Messages
2,820
Location
Calgary
I dunno. Maybe the trusty potato cannon would be a better/funner project?

Edit: I tried converting barometric pressure to inches of mercury with negative values. If you'll forgive the pun, it doesn't seem to add up. -0.75 bar = -22.15 inHg ?

Isn't vacuum better expressed as a positive rather than a negative? My brain doesn't want to go there I guess.

Yep......looks about right.

Bars are a depreciated unit , we're not supposed to use that unit anymore , it's just that it's how a lot of vacuum equipment is labled.

1 Bar ~ 1 atmosphere at sea level on Earth...
It's 14.5 psi and /or 29.5 inHg.

-1 Bar is perfect vacuum......so like -30 inches of mercury.....

:thumb:

ps :

this project appears to require more suck... and less blow. :ph34r:

Absolutely.The pump is sucking at sucking !

:rofl:
 

clshades

Well-known member
Joined
May 18, 2011
Messages
4,348
Location
Big White Ski Resort
a perfect vacuum is only theoretical anyway... -.99 will do donkey :)
What you need is a quick release valve on the back end so you don't have to keep taping it. I would suggest solid core ABS too that cellular stuff is garbage... either that or use steel or copper pipe :)

I have access to a threader if you need.

-speaking of which we should run a pipe for your BBQ and turf the propane tank ;)
 

Stukka

Well-known member
Joined
Feb 26, 2012
Messages
57
Location
Surrey, BC
The solid core ABS clshades is talking about is called abs dwv. You may or may not be able to find it at home depot though.
 

Latest posts

Twitter

Top