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 62 users online :: 5 registered, 0 hidden and 57 guests


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

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

The Team
Administrators
Global Moderators
global_moderators.png CS

"In the world of spuds today"

A place to ask general spud cannon related questions.
Sponsored 
  • Author
    Message

Unread postAuthor: Labtecpower » Wed Dec 21, 2011 4:00 pm

Started working on my new mini hybrid today;

Image

Churned out a very simple pvc back plug in a few minutes, wich is now epoxied in place.

Image

somewhat sturdier than my previous effort :roll:
I want to shoot this from my shoulder, so I cant afford blowouts. I will put some bolts in it. According to my calculations this will take about 5000 N of force at an ideal 12x mix.

Chamber material is seamless steel pipe, 25 mm id, 2.5 mm wall thickness.
I still have to determine the chamber size...

HGDT says a 15 cm chamber will give 488 joules, vs 575 joules from a 20 cm chamber....
makes it harder to supress tough :?
  • 0

"ñøw mÿ šįg šüçkś!"
User avatar
Labtecpower
Major General
Major General
 
Posts: 1267
Joined: Sat Feb 20, 2010 6:38 am
Location: Herb Island
Reputation: 7

Unread postAuthor: SpudBlaster15 » Wed Dec 21, 2011 6:08 pm

It's difficult to estimate the dimensions of that plug from the picture, but assuming a length of ~30mm and a tensile lap shear strength of 1KPSI for the epoxy, the joint should hold about 2.4KPSI. I would have went with more bonding area, but it should be fine at up to 10X or so.
  • 0

People should not be afraid of their governments. Governments should be afraid of their people.
User avatar
SpudBlaster15
Major General
Major General
 
Posts: 2385
Joined: Wed Oct 18, 2006 11:12 pm
Location: Canada
Country: Poland (pl)
Reputation: 3

Unread postAuthor: pneumaticcannons » Wed Dec 21, 2011 8:58 pm

Nice :wink: planning on using a syringe or more complicated means of metering. You seem to be moving out of the realm of mini hybrids :lol:
Back plug looks good, I would trust it, then again I made a hybrid out of plastic...
  • 0

ramicaza <- My Youtube Channel
User avatar
pneumaticcannons
Major
Major
 
Posts: 392
Joined: Sat Oct 30, 2010 9:45 am
Location: shite country in asia
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Thu Dec 22, 2011 12:26 am

Looks good, but what's that slot in the schrader? Won't it compromise sealing with the pump head?

SpudBlaster15 wrote:it should be fine at up to 10X or so.


*cough*

I would still put a couple of bolts in for good measure :)

HGDT says a 15 cm chamber will give 488 joules, vs 575 joules from a 20 cm chamber....
makes it harder to supress though


Depends what's most important, low noise and massive power are competing parameters, it's difficult to have both... but not impossible ;)

What calibre is this anyway? With those dimensions a 0.22" will easily be supersonic at 12x, I assume though you're going for something bigger and heavier?
  • 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: Labtecpower » Thu Dec 22, 2011 1:35 am

It's difficult to estimate the dimensions of that plug from the picture, but assuming a length of ~30mm and a tensile lap shear strength of 1KPSI for the epoxy, the joint should hold about 2.4KPSI. I would have went with more bonding area, but it should be fine at up to 10X or so.


The plug has a diameter of 25mm, and the bonding area is 25mm high.

planning on using a syringe or more complicated means of metering. You seem to be moving out of the realm of mini hybrids


Just syringe metering, cheap and reliable :wink:
It isn't clear to me where a mini hybrid turns into a normal sized one :roll:

Looks good, but what's that slot in the schrader? Won't it compromise sealing with the pump head?


It isn't a schrader, it's a dunlop valve.
I use it as it doesn't have a spring in it, and it doesn't leak air when disconnected.

Depends what's most important, low noise and massive power are competing parameters, it's difficult to have both... but not impossible

I'm going for the 20 cm chamber :)
Power is more important te me :wink:
I'm thinking of keep this unsurpressed until new year's eve, people don't pay very much attention to loud noises this time of year :)
especially not when they're my neighbours
I'm thinking of using a DWV pipe as the supressor housing, what size would be appropriate?
the barrel will be 1 meter long.

What calibre is this anyway? With those dimensions a 0.22" will easily be supersonic at 12x, I assume though you're going for something bigger and heavier?


I'm going for the largest one that fits :)
With a bit of luck it will be in the 16 mm range.
  • 0

"ñøw mÿ šįg šüçkś!"
User avatar
Labtecpower
Major General
Major General
 
Posts: 1267
Joined: Sat Feb 20, 2010 6:38 am
Location: Herb Island
Reputation: 7

Unread postAuthor: jackssmirkingrevenge » Thu Dec 22, 2011 2:14 am

Labtecpower wrote:It isn't a schrader, it's a dunlop valve.
I use it as it doesn't have a spring in it, and it doesn't leak air when disconnected.


Ah, right.

Image

I'm going for the 20 cm chamber :)
Power is more important te me :wink:


:D

I'm thinking of using a DWV pipe as the supressor housing, what size would be appropriate?
the barrel will be 1 meter long.


As big as you can manage :)

You can easily have a 50-60mm tube and still have an attractive launcher:

Image

Don't forget to be liberal with baffles and chambers.

I'm going for the largest one that fits :)
With a bit of luck it will be in the 16 mm range.


Can't argue with a bigger bore :) and since you can machine sabots easily, smaller projectiles or even shotgun rounds remain an option.
  • 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: Labtecpower » Thu Dec 22, 2011 3:12 am

50 mm is what I was aiming for :)

I hope I can find some time to machine baffles and end caps for the supressor...
550 joules from a relatively small bore shoulder fired gun sounds like a lot of fun to me :D

I don't think I will spend my precious machining time on making sabots :roll:
  • 0

"ñøw mÿ šįg šüçkś!"
User avatar
Labtecpower
Major General
Major General
 
Posts: 1267
Joined: Sat Feb 20, 2010 6:38 am
Location: Herb Island
Reputation: 7

Sponsored

Sponsor
 


Unread postAuthor: mark.f » Thu Dec 22, 2011 8:46 pm

Hmm.... how much are those PCB companies charging these days? :roll:

EDIT: and unsurprisingly, it doesn't work. I double checked my wiring, though, and I think the likely culprit is that I fried the power switching transistors with my 75-watt howitzer/soldering iron.

It was supposed to be a PWM circuit with a 12 and 3VDC output, but all I can measure at the emitters of the switching transistors is 0v.

<div align="center">Image</div>
  • 0

Attachments
IMG_0216.JPG
User avatar
mark.f
Donating Member
Donating Member
 
Posts: 3464
Joined: Sat May 06, 2006 11:18 am
Country: United States (us)
Reputation: 21

Unread postAuthor: dewey-1 » Thu Dec 22, 2011 11:07 pm

Mark;

post the schematic you used and the component side of that board.
  • 0

User avatar
dewey-1
Major General
Major General
 
Posts: 1298
Joined: Wed Mar 28, 2007 10:24 am
Location: NE Wisconsin USA
Reputation: 0

Unread postAuthor: mark.f » Thu Dec 22, 2011 11:41 pm

As you wish:
  • 0

Attachments
IMG_0218.JPG
scan.jpg
User avatar
mark.f
Donating Member
Donating Member
 
Posts: 3464
Joined: Sat May 06, 2006 11:18 am
Country: United States (us)
Reputation: 21

Unread postAuthor: dewey-1 » Fri Dec 23, 2011 1:32 am

mark;
I do see some problem areas.

What are you trying to achieve with this circuit design?
A DC motor control and 3 VDC charger?

Why such a high Astable frequency? 68KHz

What kind of motor?
  • 0

User avatar
dewey-1
Major General
Major General
 
Posts: 1298
Joined: Wed Mar 28, 2007 10:24 am
Location: NE Wisconsin USA
Reputation: 0

Unread postAuthor: mark.f » Fri Dec 23, 2011 3:17 am

It's basically just to provide two switched power sources without ohmic losses as involved with linear regulators. This is sort of a "proof of concept" circuit.

I suppose I could go lower with the frequency. 68kHz is just one of the "standard" 555 frequencies (made with a 1kohm, 10kohm, and 0.001uF capacitor).

The motor is brushless.
  • 0

User avatar
mark.f
Donating Member
Donating Member
 
Posts: 3464
Joined: Sat May 06, 2006 11:18 am
Country: United States (us)
Reputation: 21

Unread postAuthor: JDP12 » Fri Dec 23, 2011 3:24 am

ITWOST, been working frantically on my semi-auto pneumatic rifle. had my barrel sealing valve working with a 100% seal, then i added a vent hole to fill the chamber so it would actually fire, and found out an epoxy job i did SUCKED so I i had to redo it... waiting for epoxy to cure.

Tomorrow I'm actually hoping to test it (free of epoxy leaks and just having to deal with thread leaks). After that there isn't much I can do until i get all the parts in the mail and my machined block from ramses.. But I can work on my dart design!
  • 0

"Some say his pet elephant is pink, and that he has no understanding of "PG rated forum". All we know is, he's called JSR. "
User avatar
JDP12
Major General
Major General
 
Posts: 1943
Joined: Fri Mar 30, 2007 8:34 pm
Reputation: 0

Unread postAuthor: mark.f » Tue Dec 27, 2011 4:24 pm

ITWOST, I just bought one of these.

Apparently somebody thought I would use that TSC gift card to quietly buy a new set of socket wrenches or something. :roll:

Only niggle is the 1-1/8" opening, but I can't really complain, as it already has a very redundant set of static seals pre-installed. :wink:
  • 0

User avatar
mark.f
Donating Member
Donating Member
 
Posts: 3464
Joined: Sat May 06, 2006 11:18 am
Country: United States (us)
Reputation: 21

Unread postAuthor: Gun Freak » Tue Dec 27, 2011 4:27 pm

Why would you buy that :lol:
  • 0

OG Anti-Hybrid
One man's trash is a true Spudder's treasure!
Golf Ball Cannon "Superna"M16 BBMGPengunHammer Valve Airsoft SniperHigh Pressure .22 Coax
Holy Shat!
User avatar
Gun Freak
Lieutenant General
Lieutenant General
 
Posts: 4969
Joined: Mon Jan 25, 2010 4:38 pm
Location: Florida
Country: United States (us)
Reputation: 11

PreviousNext

Return to General Spud Cannon Related

Who is online

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

Reputation System ©'