Mortar Build Question - what type of metal?

[PBRstreetgang]

hello,

I'm thinking of have coehorn mortar made at my local machine shop and was wondering what type of metal I should use.  I read an interesting article on buckstick's website and basically want to duplicate his mortar, which shoots duckpin bowling balls.  He used Brass C360 which appears very nice but I really like the idea of using bronze...my questions are:

1. Exactly what type of bronze should I use?
2. Is bronze more difficult to work than brass?
3. Is there a structural benefit in using bronze over brass?
4. what would you estimate it would cost me to have it machined, assuming I supply the metal?
5. Anyone want to recommend a good place to buy metal online?

Thanks in advance
PBR

[Zulu]

What size mortar?
Who is Buckstick?

[PBRstreetgang]

12lb mortar that can shoot duck pin bowling balls which are 4.5". 

[dan610324]

whats a duckpin bowling ball ?? whats the size ??

why not make an wax master and have it cast solid and just machine the bore ??

sorry , you was quicker then me   

[Double D]

Buckstick website has been banned from this forum for a long time.  Let me remind every one of this rule.

Language.

 GBO is a family board. Anything you post here should be fit to say to your kids and your Grandmother. If not, don’t post it. Certain words and phrases have been banned.  The banned word or phrases if entered in a post will show as some other acceptable word, phrase, (censored word) or asterisks.  Do not post alternative spellings or formatting to avoid the banned word list.  Find a better word or accept the banned word list alternative.  If I find you are trying to use alternative spellings or formatting to convey the banned word I will remove your post and let Graybeard deal with you.

Buckstick's website is not banned for  bad language, but it was banned for extremely bad judgment in how he uses cannon's.  More than one time discussions here about his cannons have degenerated in arguments about that use.  After the last software change, access to the banned word list was reserved to Admin's only.  I can no longer access the list.

I have asked the Admin to remove Buckstick's web site from the banned list.  As soon as the ban is lifted references to his website will be allowed here.  

What will not be allow is any reference to how he used his cannons.  There may be a place on GBO for that discussion, but it is not and will not be here; it is just too disruptive and way off topic.  

In the mean time, the discussion of his building practices of both his mountain howitzer and his mortar are allowed.  There is something to be learned from what he built and it is a disservice to everyone to ban that information for his lack of good judgment in use.

For those not familiar with Buckstick, change the spelling of stick to stix and google the name to see his work.

So guys help PBRstreetgang  out here.

I realy don't see anything wrong with the build.  It is going to be expensive- material cost-machining cost, to have this done unless you have a good old boy connection connection to the local machine shop and can get it done on the cheap.  You might want to check with our sponsor's and see what they would charge you.

What do the rest of you think of Bucksticks build, in particular the method of attaching the trunnion?

[PBRstreetgang]

Didn't know about him being banned...sorry for the reference.

I've found some aluminum bronze (7"x12") for roughly $1200.00 delivered...the machining cost is a complete unknown to me.  I was hoping someone might have a rough idea of what a "reasonable" machining cost should be so when walk into the machine shop I'll kind of have a decent estimate for how much to spend.

If there's a better way to do this, I'd be happy to hear it...I'm always looking for the "easiest best way" to do anything.

Thanks,
PBR

Geoff Gleaton
FSA Orangeburg
803-534-2409 x 105

[dan610324]

start thinking safest way to do it insted , that should always be prio 1
it can save your life  
this hobby isnt only fun , it takes a lot of responsibility also


for $ 1 200  you can get a awful lot of bronze cast if you buy scrap copper and virgin tin
aluminum bronze isnt the material I would choose
but ok , just my opinion

[Zulu]

I Googled. 
Now I know who Buckstix is.
Good grief!
Zulu

[dan610324]

talk about overkill  

how will he tighten the scews when the trunnion bar gets lose ??
it would even been much better to soft solder the joint

[Double D]

Dan,

I agree with you, soldering would be better, no taper on the trunnion.

I just noticed that B-S mortar has no windage.  His bore is 4.5 inches.  A candle pin ball is 4.5 inches maximum.  To use a candle pin ball you need a bore of   4.615 inch.

[Victor3]

1. Exactly what type of bronze should I use?
2. Is bronze more difficult to work than brass?
3. Is there a structural benefit in using bronze over brass?
4. what would you estimate it would cost me to have it machined, assuming I supply the metal?
5. Anyone want to recommend a good place to buy metal online?

1. Some brasses/bronzes are better for cannon barrels than others, but many here (including sponsers and professional builders) have used 360 brass, 464 "naval bronze" (actually a brass, not bronze) aluminum bronze, 90/10 "gun metal" bronze, Silicon bronze and others. If I were gonna machine a barrel out of solid bar I'd use 464 but that's just my preference because it's common in round bar form, stronger than 360, machines nicely and I have a small mortar made out of it that looks nifty

2. Generally speaking, bronze is more difficult to machine than brass. It depends on the alloy though. In my experience, 90/10 bronze has been tough to machine. Silicon and aluminum bronze I've worked with were easier to cut.

3. Yes. Historically, bronze has been used more often than brass because it's generally stronger. Again, it depends on the specific material. It's a good idea to look into the properties of the alloy you plan on using. I often refer to this website...

http://www.matweb.com/

4. Machining costs are highly variable and can be anywhere from 'wow, can I pay you right now?' to 'holy mackerel!' depending on many factors. Look for small shops with old guys in blue/white striped coveralls and matching hats operating large old lathes.

5. Shipping cost for a large piece is expensive so I always buy locally. www.onlinemetals.com/ and www.speedymetals.com/ are places hobby guys I've talked to have bought stuff from though.

 If you're not thoroughly confused yet, I can make it worse if need be. HTH 

[PBRstreetgang]

Thanks for the detailed answers and I sincerely appreciate your insight.

Thanks again!
PBR

[brokenpole]

I didn't remember the name of the individuals website but I do remember seeing it before.  I am sorry if I offend anyone and DD if this post goes away I do apologize but IMHO this guy is a loon.

I so enjoy manning the crew of a 12 pound 1841 Napoleon.  I also enjoy shooting my smaller juice can and golf ball mortors.  But I always remember while I am having fun that these things were used to take human life in a time of war.  So to see a person using mortors and cannons to attempt to hit a live animal just sickens me.

[irishman]

I've found some aluminum bronze (7"x12") for roughly $1200.00 delivered...the machining cost is a complete unknown to me.  I was hoping someone might have a rough idea of what a "reasonable" machining cost should be so when walk into the machine shop I'll kind of have a decent estimate for how much to spend.

If there's a better way to do this, I'd be happy to hear it...I'm always looking for the "easiest best way" to do anything.

Thanks,
PBR

Geoff Gleaton
FSA Orangeburg
803-534-2409 x 105

PBR,  My equiptment won't handle 7inches, but, other Sponsers here can do a Professional job for you. First, $1200.00 for 142 pounds is steep. Machine time will be less for someone who has done this before. Thirdly, and most important of all, my fellow GBO Sponsers understand what is safe and won't build something that isn't. (after the smoke blows away, you will have a safe, beautiful barrel for less)

                                                 Michael

[PBRstreetgang]

Good point...would anyone like to recommend someone?  Feel free to PM me if you wish.

Thanks,
Geoff

[Double D]

Go to the http://www.gboreloaded.com/forums/index.php/topic,2814.msg14083.html#msg14083 to find a list of sponsors.

Drop them an email and see what they can do for you.

You can provide a a machinist a drawing and he can make you a cannon.  A Machinist who knows how to build cannon will understand simple nuances such as proper windage, corner radius, vent diameter, trunnion size, etc. 

The B-S build is a good example of not recognizing those nuances.

[Double D]

http://www.buckstix.com/MortarBarrel.htm

[grymster]

While not quite as machinable as brass, most bronze alloys machine pretty well, with the exception of those with high nickel content.

Cost will likely be high. If your barrel were to be machined in the shop I manage, you'd be looking at something on the order of $2,500 or more, but we're definitely on the high side and other local shops charge as little as half as much. 

[dan610324]

is that only the machining cost or does it include the needed bars ??

[barefiel76]

I asked a similar question recently for a Howitzer build. Speedymetal appears to have the most affordable metal. It doesn't seem to matter where you go, brass and bronze are pretty expensive. I think Rocklock suggested gold as a cheaper alternative. It was also around $100 shipping.

[grymster]

is that only the machining cost or does it include the needed bars ??

You talkin' ta me?  

That would be machining only. We're dang expensive.

[RocklockI]

BR Streetgang ! My Dad was The OG .... I'm an old G . Rednecks ,white ,socks and Pabst Blue Ribbon Beer .

I'll stay out of this as you got plenny of suggestions .

Welcome aboard !

[GGaskill]

I don't know where you potential metal buyers are located but your best bet is to go to a metals dealer in a big city and look for some rems (remnants), drops, etc.  These are all names for pieces left over from long bars used for some other project.  Since the metal is dense material and you are buying a fairly large piece, ordinary shipping will be high, so the best way to deal with that is to make your buy while you are in the city for some other reason.  That way you can charge the travel to the other reason instead of your cannon metal.   

[dan610324]

grymster
yeah I was talkin to you
wow you ARE expensive , what do you charge per hour for a small lathe or milling machine ??
no Im not a potential customer , just curious 
would be interesting to compare to swedish prices

[Double D]

There use to be a big difference in shop prices between a job shop, a shop that does small and repair work and a production shop a d shop that takes on design and production work...the production shop was always the more expensive shop for one job.

[grymster]

We're a captive shop in a government institution. We do mostly one-off R&D work. We have some very nice equipment and some of the best machinists (and other craftsmen) I've seen in my 35 years in the business. For the most part, we only work on really difficult or sensitive projects. We're very careful not to compete with private enterprise and with our high cost it would be difficult anyway. With the high cost of our people and equipment, plus the overhead for environmental services, security and facilities maintenance, we're charging a minimum of $135/hour. But there are plenty of local shops that charge half of that.

I'm wandering far off topic here, so has the OP considered steel for his barrel? Much cheaper and I think some of the steels appropriate for barrels are not much more difficult to machine than brass.

[Victor3]

 PBR,

 I was thinking the same as grymster; if you could live with a steel mortar you could save quite a bit of money. You'd probably pay only 20% as much for steel as you would any bronze/brass stock of the same size. Machining costs should be similar.

 Just as an example, I estimated what I think it would cost me (Machining + welding trunnion on & 1018 steel material) to have a mortar similar to what you want made locally. I came up with ~$800. However, this is considering material with no markup over a supplier's cost and free delivery to a friend's shop, where he would do the work at the buddy-buddy discount rate. I'd expect it to cost at least 2x that if you came in off the street asking for a one-off to be made by the average 'job shop' not already involved with making cannons. 

 One of the sponsers could probably beat the cost of what I could have my friend make one for, and you wouldn't have to explain to them how to make it. Shipping cost is one consideration if you go that way though.

[RocklockI]

Also IF you went with steel you could have it bronze plated .....?

[tombstone270]

If you did go to steel would 1080 be a good choice???



tomb

[Cat Whisperer]

If you did go to steel would 1080 be a good choice???
tomb

In a word, no.  1018 has less carbon (hence lower strength, BUT less susceptablity to becoming brittle).
It may be common old cold-rolled steel (sometimes looked down upon because there are much 'stronger' steels), but it's 'strength' in the application of cannons and mortars is proven in the long run.  Do your own research - check out the charpy notch test for both 1018, 1024, ... 1080 steels.  See which is most resistant to cracking!