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 77 users online :: 5 registered, 0 hidden and 72 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

hybrid C:B ratio

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
Sponsored 
  • Author
    Message

hybrid C:B ratio

Unread postAuthor: FishBoy » Sun Sep 28, 2008 7:01 pm

ok, after getting bored going through 3 pages of searched results, it think it's semi-ok to ask. What are good C:B ratios for hybrids?
  • 0

User avatar
FishBoy
Colonel
Colonel
 
Posts: 575
Joined: Tue May 27, 2008 5:51 am
Reputation: 0

Unread postAuthor: Lentamentalisk » Sun Sep 28, 2008 7:23 pm

use HGDT (hybrid gun design tool, made by D_hall) and experiment around. It depends on just about everything. There is no overall good C:B ratio

linky
  • 0

Do not look back, and grieve over the past, for it is gone;
Do not be troubled about the future, for it has not yet come;
Live life in the present, and make it so beautiful that it will be worth remembering.
User avatar
Lentamentalisk
Brigadier General
Brigadier General
 
Posts: 1202
Joined: Tue Aug 07, 2007 5:27 pm
Location: Berkeley C.A.
Reputation: 0

Unread postAuthor: Ragnarok » Sun Sep 28, 2008 7:35 pm

As general advice, don't go below (0.8/X):1 where X is your minimum planned mix number for general use - these are still combustion based, so the same ratios apply in similar ways, remembering that hybrid gases are more dense.

So if you're working at 2x and above, stay above 0.4:1, for 4x and above, have at least 0.2:1 - you get the idea.

Extra advice of my own is don't go above about (4/Y):1 either - where Y is your maximum mix number - unless you're either a very long way from it, or being deafened is a hobby of yours.
  • 0

Does that thing kinda look like a big cat to you?
User avatar
Ragnarok
Chief of Staff
Chief of Staff
 
Posts: 5339
Joined: Tue Dec 19, 2006 8:23 am
Location: The UK
Reputation: 8

Unread postAuthor: DYI » Sun Sep 28, 2008 8:27 pm

Ragnarok's advice is quite accurate, including the bit about being deafened. If you think it's just paranoid, overcautious advice from someone with no real experience, consider this: From my experience, for a given mass of propellant, hybrid gas guns without barrels are significantly louder than any pyrotechnic or high explosive I've used - a 150ci volume, 2" porting hybrid at 20x was loud enough to make my ears ring slightly from 100 feet away in a completely open area, and the concussion from it was quite noticeable to everyone present.

The point? If you don't want to end up in a heap of trouble, be extra cautious about where you shooot big hybrids.

And of course, always do extensive fiddling with designs in HGDT before you actually go out and start buying stuff.
  • 0

Spudfiles' resident expert on all things that sail through the air at improbable speeds, trailing an incandescent wake of ionized air, dissociated polymers and metal oxides.
User avatar
DYI
Lieutenant General
Lieutenant General
 
Posts: 2861
Joined: Sat Jul 07, 2007 8:18 pm
Location: The People's Republic of Canuckistan
Country: Turks and Caicos Islands (tc)
Reputation: 9

Unread postAuthor: FishBoy » Sun Sep 28, 2008 8:31 pm

my hybrid will be similar in size to big bob's lieutenant johnson; i will be using 2x-6x mixes, what would be a good ratio for that?
  • 0

User avatar
FishBoy
Colonel
Colonel
 
Posts: 575
Joined: Tue May 27, 2008 5:51 am
Reputation: 0

Unread postAuthor: DYI » Sun Sep 28, 2008 8:36 pm

my hybrid will be similar in size to big bob's lieutenant johnson; i will be using 2x-6x mixes, what would be a good ratio for that?


Perhaps you should actually read me and Rag's posts in the topic. They'd do you a load of good.

Do you have HGDT yet?
  • 0

Spudfiles' resident expert on all things that sail through the air at improbable speeds, trailing an incandescent wake of ionized air, dissociated polymers and metal oxides.
User avatar
DYI
Lieutenant General
Lieutenant General
 
Posts: 2861
Joined: Sat Jul 07, 2007 8:18 pm
Location: The People's Republic of Canuckistan
Country: Turks and Caicos Islands (tc)
Reputation: 9

Unread postAuthor: Ragnarok » Sun Sep 28, 2008 8:37 pm

FishBoy wrote:what would be a good ratio for that?

I'm by no means a hybrid expert, but I'd say 0.5:1 would be acceptable for all of those, not have power problems at the low end, and not be uncontrollably noisy at the top end - but still use ear protection regardless!

Like DYI says, it's worth reading posts and working out yourself though, otherwise you won't end up learning!
  • 0

Does that thing kinda look like a big cat to you?
User avatar
Ragnarok
Chief of Staff
Chief of Staff
 
Posts: 5339
Joined: Tue Dec 19, 2006 8:23 am
Location: The UK
Reputation: 8

Sponsored

Sponsor
 


Unread postAuthor: FishBoy » Sun Sep 28, 2008 8:41 pm

thanks a lot, I just downloaded HGDT. I like it so far :D
  • 0

User avatar
FishBoy
Colonel
Colonel
 
Posts: 575
Joined: Tue May 27, 2008 5:51 am
Reputation: 0

Unread postAuthor: DYI » Sun Sep 28, 2008 8:52 pm

0.5:1 at 6x shouldn't have any huge problems with noise or power. My ME20H-41 had a ratio of about 1:1, and wasn't even that badly noisy at 20x (although different ranges affect this, it sounded like the end of the world when we set it off at 20x on my friend's farm, but was nearly silent on a windy day at my main shooting range).
  • 0

Spudfiles' resident expert on all things that sail through the air at improbable speeds, trailing an incandescent wake of ionized air, dissociated polymers and metal oxides.
User avatar
DYI
Lieutenant General
Lieutenant General
 
Posts: 2861
Joined: Sat Jul 07, 2007 8:18 pm
Location: The People's Republic of Canuckistan
Country: Turks and Caicos Islands (tc)
Reputation: 9

Unread postAuthor: Lentamentalisk » Sun Sep 28, 2008 8:57 pm

The key there is the wind. Wind has a very unexpected effect on noise level. Where I live there is a bike path that goes right along the freeway, right by the bay, so there is a fair amount of wind. On the bike path, the noise from the traffic, not more than 20' away is minimal, but on the other side of the freeway is tremendous.
I would expect it would have similar effects on explosive shock waves.
  • 0

Do not look back, and grieve over the past, for it is gone;
Do not be troubled about the future, for it has not yet come;
Live life in the present, and make it so beautiful that it will be worth remembering.
User avatar
Lentamentalisk
Brigadier General
Brigadier General
 
Posts: 1202
Joined: Tue Aug 07, 2007 5:27 pm
Location: Berkeley C.A.
Reputation: 0

Unread postAuthor: jimmy101 » Mon Sep 29, 2008 2:11 pm

FishBoy wrote:thanks a lot, I just downloaded HGDT. I like it so far :D

OK. Then pick either a barrel (length and ID) or a chamber (length and ID). Go to the tools menu and pick "Sensitivity Studies". If you decided on a particular barrel then tell the sensitivity study to vary the length of the chamber. (IF you picked your chamber then tell sensitivity to vary the length of the barrel). Enter starting and stoping values for the study (try 1/3X and perhaps 3X what you think the length should be.) Click the "Calculate" button.

You now have a graph of the affect of the particular variable on performance. You'll probably see that there is no optimal chamber size for a fixed barrel. Bigger chamber gives better performance. You'll also notice that after a certain point you have to make large changes to get even a small increase in performance. Double the chamber size and the performance only goes up by 10% in velocity.

Bottom line for hybrids, for a fixed barrel there usually isn't an optimal chamber, bigger is almost always better. For a fixed chamber there is an optimal barrel but it is often impractically large. You can get very near maximum performance with a chamber (or barrel) much shorter than the optimal.
  • 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

Return to Hybrid Cannon Discussion

Who is online

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

Reputation System ©'