All You Windage Guys

[brokenpole]

I have a mortar that shoots 6 1/2 oz juice cans.  I have took the mic to the muzzle and did the calculations for windage and came up with a size of 53.6mm.  I asked Fox what they have that is close and all they have is 50.88 mm. 

Is that too much windage?

[GGaskill]

They will launch but you will be wasting powder and maybe not get good accuracy.  You only need about 1.34 mm windage and 50.88 shot gives about twice that.

On the other hand, what's a little wasted powder?  Noise.   



Clarified as recommended below.  :-)

[Cannoneer]

Hi Brokenpole,
I think you meant to say that the diameter of the bore is 53.6 mm. Then a 50.88 mm diam. projectile would give you 2.72 mm windage.

[Double D]

Here is the K.I.S.S. formula to determine the proper size projectile for an existing bore using the basic 1/40 windage rule:

Bore diameter  divided by 40 equals windage.

39 times windage equals projectile diameter.

If you build a cannon to shot a specific projectile here is K.I.S.S. formula:

Projectile diameter divided by 39 equals windage.  Windage times 40 equals  bore diameter.
 

[Cat Whisperer]

There is an elegance in simplicity!

[brokenpole]

Sorry I didn't get back to this sooner.  Work has been a bear. 

In my original post I failed to mention that I had done the calculations as described in responses to the original post.  My bore diameter is a shade over 55mm so I just used that and calculated a projectile size of 53.625mm.  Only problem is the best fit I have been able to find is a 2 inch diameter ball. This works out to be 50.8mm.  I was concerned that the extra 3mm windage might create an issue.

Fox has 2 inch steel balls but they have a flat spot on them and are not perfectly round.  I have found other manufacturer's that make them and they are like $3.50 each. 

I have found a site that offers cast iron 2 inch balls for $1.19 each + shipping.

Other than the rust factor or cast iron, any other down side to using cast iron instead of SS as projectiles?

Thanks for the help.

[Double D]

Sorry I didn't get back to this sooner.  Work has been a bear. 

In my original post I failed to mention that I had done the calculations as described in responses to the original post.  My bore diameter is a shade over 55mm so I just used that and calculated a projectile size of 53.625mm.  Only problem is the best fit I have been able to find is a 2 inch diameter ball. This works out to be 50.8mm.  I was concerned that the extra 3mm windage might create an issue.

Fox has 2 inch steel balls but they have a flat spot on them and are not perfectly round.  I have found other manufacturer's that make them and they are like $3.50 each. 

I have found a site that offers cast iron 2 inch balls for $1.19 each + shipping.

Other than the rust factor or cast iron, any other down side to using cast iron instead of SS as projectiles?

Thanks for the help.

Lets use apple or oranges to figure this out, not both.

55mm = 2.165".
2" = 50.8 mm

Bore
Apples equal 55/40=1.375 x 39 = 53.625mm ball needed for 55 mm bore
Oranges equal 2.165/40 = 0.054 x 39= 2.11" ball needed 2.165" (55mm bore)

Ball
Oranges equal 2/39 = 0.0513 x40 = 2.051 bore needed for  2 inch ball
Apples equal 50.8/39 = 1.303 x40 =  52.103 bore needed for 50.8mm (2 inch ball)

2 Inch ball is to small.

Josh Madison's convert program sure helped figuring this out. http://joshmadison.com/software/convert-for-windows/

[thelionspaw]

Broken pole: Math isn't my thing but I found hot-stamped smooth texture steel spheres 1-15/16", 1.13 lbs @$1.99 ea.,  $1.79 (50+), $1.49 (100+). Is this closer to what you need?

rc

DISREGARD: DoubleD has come through again. I stand corrected.

r

[little seacoast]

Hi, This is exactly the problem that drove me to try sabots for my 2.25" gun.  A 2" Fox ball is the closest thing that I have been able to find in metal that is readily available cheaply.  Try a sabot and see if that works for you.

[Double D]

Sounds  like you guys need to visit or sponsor list  have them make a mold to cast some zinc.

[little seacoast]

DD, I agree a mold is probably the best solution, but that brings us back to the affordable-read cheap- issue.  A mold plus a supply of zinc and melting apparatus is going to run into a fair amount of cash. Particularly when recovering your used ammo is problematic, a  barren landscape would help.  
    What are you paying for zinc these days?  

[Double D]

Buy zinc? why, I just go get it and shoot it again...well okay some where up at Southpaws farm is 24 lbs that I can't find. Well 6 pounds is the pond.

I have been getting zinc mixed in with the wheel weights I pick up for bullet casting.

Pick up a an old cast iron pot and a turkey cooker at a yard sale. Or make your own pot out of a piece of pipe

Buy the mould!

[RocklockI]

FWIW you can go to any junk yard and pull out the burner for a water heater that has poopped out . They are a favorite source of backyard foundries .

Make , find or buy some suitable and stable stuffage to hold the burner with a rest on top for the cast iron pot , (use gloves )

This is not your fathers Lee melting pot ! Get a good mold with some resivour to hold hot zinc to feed the mold as the ball shrinks .

Many per hour . I know this because I watched George and Mike bust balls for an hour or so in Mont. at the DD gofor ranch   , but when they were done they had a bunch of 1.25" balls IIRC .

It was hot and sweaty work to be sure , but as Tracy and I both saw something up in the sky ....180 degrees in the opposite direction of any 'nearly heard' request for ....well , help .  It didnt bother either of us much   .

And Tracy and I agreed to have NOT heard the pleas for help . DD was in on the "I hear nothing " agreement ,in an unspoken way as well .

But George and Mike made some nice zinc balls .

There's really not much to it ,a propane tank and a burner . Also a couple freinds who wont just stare off into the sky blindy ,trying hard to look intent on ....well just busy all around .
Gary

[Double D]

Actually, I was inthe "get out of the way" mode.

[Zulu]

When you make a multiple ball pour, doesn't the mould get so hot that it takes longer and longer before you can open it?  That is the problem I had pouring lead.  If I opened the mould too soon the balls would sag out of round.  The mould got hotter and hotter with each pour and it became a guessing game as when to open it.  I use a steel mould for 2.95" balls and I could only pour 6 or 7 before I had to quit because it got too hot.  I use a crawfish burner and a piece of 10" pipe with a 3/8" bottom and handles welded on it for a pot.  It melts lead and zinc fine.
Zulu

[Double D]

Zulu,

We never seemed to reach that point with zinc.

[GGaskill]

We also weren't setting the world on fire casting.  We did 30 2.65" balls and I don't remember how many smaller ones in most of the day.  The mould spent a fair amount of time sitting open while we were messing around with something else.  Also, we may have been alternating large and small shot, which would have given each mould a little more time to cool down.

[MikeR C]

And we had to use a hand held propane torch to keep the zinc around the sprue molten while the ball setup. At least the top of the mold was to cool to keep the zinc molten. I don't recall waiting too long before we beat it open with a stick and they were pretty solid when they hit the ground.
The way I remember it the balls were cast by those MOST qualified to do precision work, eh George

MikeR C

[little seacoast]

Ok DD, 35lbs of zinc is on the way. Now  if I burn the place down or poison the neighbors my wife says she's comin' for ya.

[Double D]

 
The way I remember it the balls were cast by those MOST qualified to do precision work, eh George

MikeR C

Yes that the way I remember it also, yes that's it!!

Ok DD, 35lbs of zinc is on the way. Now  if I burn the place down or poison the neighbors my wife says she's comin' for ya.

Okay!!!  Tell her to bring it on, can she cook?