Mortar Thoughts and Opinions.

[Doc Brown.]

So I made the thunder mug and it was kinda lame. So I threw this mortar together for fun and was wondering if you guys can tell me if its a ok design. A little under 4"dia Breach with a 1.5" diameter Powder chamber and 2 3/4" deep. I know its not 3 caliber so no need to point that out to me.  My biggest concern is the powder chamber is to small for a 3.5" bore. I haven't tried to shoot any thing out of it except foil and im wondering if it could shoot something heavy out of it.  What would be good to shoot out of it that is heavy and a little under 3.5" diameter?
 

[GGaskill]

Looks like your chamber will hold about 3 oz of cannon grade.  See what you can find in pipe (both iron and plastic) couplings to fill with concrete.  Start with 1 oz.

You say it's 1045--check the weld to see how hard it is.  I think 1045 will get hard from welding unless you preheat it.

[Victor3]

 Taking various design/construction features of your mortar into account, I wouldn't use more than 1/2 oz of Fg nor a projectile over 2# unless you're prepared to repair some cracks in the wood. Even at that light of a load, I imagine it may flip over backwards. 

[Doc Brown.]

Taking various design/construction features of your mortar into account, I wouldn't use more than 1/2 oz of Fg nor a projectile over 2# unless you're prepared to repair some cracks in the wood. Even at that light of a load, I imagine it may flip over backwards. 

 
I agree the cheeks might break and it might flip. In this picture im going to attach. What makes the cheeks stronger than mine?
 

[Double D]

I think you are firing blank loads in the video.   If those are blank loads you are firing they scare me.

When you fire a projectile that mortar will most likely flip on its back.   The bed should be roughly twice as long as the barrel with the trunnions centered front to back.

Oops Victor already said that.
 

[BoomLover]

Doc, that was one mighty blast...your video skills are as impressive as your smoke and fire....thanks for posting! ( I checked out some of your other videos, nice work! ) BoomLover

[Doc Brown.]

I think you are firing blank loads in the video.   If those are blank loads you are firing they scare me.

When you fire a projectile that mortar will most likely flip on its back.   The bed should be roughly twice as long as the barrel with the trunnions centered front to back.

Oops Victor already said that.

 Thanks boomlover. 2X centered thanks.  Yes they are blank loads of 3F. I don't know know how to put it in grain form. I used 1 full Shot glass of 3F and Fired that thing now about 5 times. My brother and dad just bought 5 pounds more of 3F and are going to be shooting this at a family pic knick this fourth. It is kinda scary and theres a ringing  that takes place after a shot. Kinda like if you would knock a piece of silver ware off of a glass of water. Im defiantly not going to use the 3F when I shoot a block of cement out of this.
 
I think im going to call this an economy base skid for signaling only. Im going to have to build a better bed for it to launch a brick out of.
 
 

[Old Nukee]

If your shot glasses are the same size as mine, that's 2 full ounces of powder. Ay, caramba! that's something in excess of 800 grains.
If you want to confirm, find a safe place to pour out a can of powder into shot glasses, and see how many you can fill. Divide 7000 by the number of glasses to give you your charge in grains.
I'll bet you'll find yourself a smaller measure!

[Old Nukee]

Update:


Rummaging around, I did find a shot glass that held an ounce and a quarter. Maybe no need to panic.


Also, you can find the volume of your glass by using it to fill a measuring cup with water. Much safer than handling powder.

[Double D]

You guys are really scaring me now.

A fluid ounce is not the same unit a an ounce  by mass or volume. 

Get a scale or a volumetric powder measure and weigh your charges.  Leave the kitchen utensils in the kitchen for baking cookies.

You may wonder why some of us, particularly me gets naggy about safety. When someone does something stupid and gets hurt it reflects badly on all of us and threatens the futures of our hobby.

I call you on safety and that pisses you off, that is too bad.  I would rather you were you were mad at me than dead or injured. 

You need to pay attention to what you are doing, one careless moment can injure or kill.

Sadly before next Monday we are going to have a cannon accident reported here, I just pray and hope it is not someone who came here to find an example.

[GGaskill]

The main difference between the above mortar bed and yours it that the line of the recoil force goes through it into the ground while on yours, it goes behind the back edge.  With minimal recoil from blank loads, yours stays upright, but once you put a shot in there, it is going to roll around the bottom rear corner and at least flip over.  You can prevent this by extending the rear of the existing bed. 

Or aiming the barrel the other direction so the current front extends behind the barrel.  But that may not prevent it from tipping over from imbalance.

[Victor3]

Taking various design/construction features of your mortar into account, I wouldn't use more than 1/2 oz of Fg nor a projectile over 2# unless you're prepared to repair some cracks in the wood. Even at that light of a load, I imagine it may flip over backwards. 

 
I agree the cheeks might break and it might flip. In this picture im going to attach. What makes the cheeks stronger than mine?

 First of all, I don't want to come off as throwing dirt on your mortar. You've obviously put substantial time into making it.
 
 However, I do have a little experience with wooden 'sled beds,' not all of it good. 
 

[Doc Brown.]

Taking various design/construction features of your mortar into account, I wouldn't use more than 1/2 oz of Fg nor a projectile over 2# unless you're prepared to repair some cracks in the wood. Even at that light of a load, I imagine it may flip over backwards. 

 
I agree the cheeks might break and it might flip. In this picture im going to attach. What makes the cheeks stronger than mine?

 First of all, I don't want to come off as throwing dirt on your mortar. You've obviously put substantial time into making it.
 
 However, I do have a little experience with wooden 'sled beds,' not all of it good. 
 

Don't worry I don't think you are throwing dirt at all. I appreciate everyones input. The last bed I made blew into a million pieces after firing a blank load of a half pound. That was a bigger mortar though. Still the only difference really with this is I put steel bands under the trunnions and on top.

[Zulu]

This carriage fell apart also.
Zulu
http://www.tudorcook.co.uk/gallery/main.php?g2_itemId=4229
 

[KABAR2]

This carriage fell apart also.
Zulu
http://www.tudorcook.co.uk/gallery/main.php?g2_itemId=4229

  And that my friends is why we do not make cannon barrels out of sugar......

[GGaskill]

One other thing I should add; be sure that the bed is tightly engaging the ground, especially along the centerline of the barrel, so that you are not bridging the ends.  That way the force will be transmitted into the ground by compression of the wood rather than bending it.  Wood resists compression much better than bending.

[Artilleryman]

Properly supporting the mortar bed is good advice.  I saw a mortar platform that was unsupported by ground contact broken into firewood.