Login    Register
User Information
Username:
Password:
We are a free and open
community, all are welcome.
Click here to Register
Sponsored
Who is online

In total there are 66 users online :: 5 registered, 0 hidden and 61 guests


Most users ever online was 155 on Mon Aug 15, 2016 1:40 am

Registered users: Bing [Bot], Google [Bot], Google Adsense [Bot], MSNbot Media, Yahoo [Bot] based on users active over the past 5 minutes

The Team
Administrators
Global Moderators
global_moderators.png CS

Is my chronograph having issues?

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
Sponsored 
  • Author
    Message

Is my chronograph having issues?

Unread postAuthor: High-PSI » Wed Oct 20, 2010 1:51 pm

Hey Guys,

I have been doing a bit of velocity testing lately and I have a question for you (those who understand the math far better than I).

I have gotten some odd readings from my Chrony. The gun I am firing is a 1 and 1/4 inch (nearly 1 and 3/8 inch bore) barrel, 4 feet long with a 2 to 1 tank to barrel ratio. The gun uses a 1 and 1/4 inch brass Granzow diaphram valve pilotted with a 1/2 inch bore diaphram valve. It is a very fast acting valve with a good flow rate. Firing a 25 gram slug (hollow plastic bottle wrapped with black duct tape) at 210 psi, my Chrony recorded a 1,179 fps reading, the next shot showed only 162 fps. I know the 162 fps was incorrect. However, I am not sure the 1,179 fps reading was right either. Honestly, the recoil was freakin VIOLENT! HOLY COW! Also, the stop I was using (carboard box with a couple loose towels inside) could not stop the slug. It went right through. So, I know my velocity is high, but from a previous thread, it has become clear my Chrony numbers may be off a bit.

So, who can crunch some numbers for me on this?

Oh, by the way, this stuff is ADDICTING!

Matt
  • 0


High-PSI
2nd Lieutenant
2nd Lieutenant
 
Posts: 231
Joined: Sat Oct 09, 2010 7:43 pm
Location: Nothern Illinois
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Wed Oct 20, 2010 1:57 pm

What model is your chrony, and how far away is it from the muzzle? Sometimes muzzle blast can interfere with the ready if it's too close.

Oh, and videos please!
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24225
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 66

Unread postAuthor: jimmy101 » Fri Oct 22, 2010 4:58 pm

Like jack said. Not only can the concussion affect a normally operating chrony it can really mess with one that has a bad solder joint, or wimpy battery connections, or ...
  • 0

Image

jimmy101
Lieutenant General
Lieutenant General
 
Posts: 3128
Joined: Wed Mar 28, 2007 9:48 am
Location: Greenwood, Indiana
Country: United States (us)
Reputation: 7

Unread postAuthor: High-PSI » Fri Oct 22, 2010 5:20 pm

Gotcha.

I guess what I am looking for is the engergy I have available versus the slug weight and barrel diameter. I am not a physics major. I have no clue how to calculate that. I used to have the link to a spreadsheet that would give rough data like this.

Matt
  • 0


High-PSI
2nd Lieutenant
2nd Lieutenant
 
Posts: 231
Joined: Sat Oct 09, 2010 7:43 pm
Location: Nothern Illinois
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Sat Oct 23, 2010 1:04 am

These are the online calculators I use:

This one gives you instant results in Imperial/metric etc.

This one allows you to plot a graph of velocity vs muzzle energy for a given projectile.
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24225
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 66

Return to Pneumatic Cannon Discussion

Who is online

Registered users: Bing [Bot], Google [Bot], Google Adsense [Bot], MSNbot Media, Yahoo [Bot]

Reputation System ©'