Author Topic: final 16th century mortar design, to be started in a couple weeks (Read 2303 times)

Don Krag · « **on:** January 31, 2007, 10:07:58 AM »

A while back I posted several of the upcoming plans for cannons and such. As luck would have it, the one that I thought would be the last to be started, will be the first to be finished. After quite a bit of research and a stack of possible designs I drew up, I decided on the following:

This is based on a design from 1585. It's actually going to be a bastardized design from the original, but still using elements from several other morters of the same period. Not shown in the sketch is a hand crank to be mounted across the opening on the back of the base. This will have a large diameter hemp rope that wraps around the protruding section of the breech. Cranking the rope gives infinite adjustment on elevation. The trunions will be marked for verticle with degree increments as well for ease of adjustments.

The breech measurement labeled 4", should actually be 2", though.

The actual gun will weigh in the neighborhood of 225 lbs. Depending how much actual tension there is on the rope, I might have to work something out with locks the position. I'll probably use a lock-bolt on top of the trunions. I couldn't find any detailed enough pics or descriptions in any of my references. If anyone has any experience with a system like this...I'm all ears!

The breech section is on it's way to me now and a freind has graciously allowed me to use his shop where he has a 18 x 60 lathe. I'll be playing lumberjack this weekend and taking out a 50' black oak that died this August. This will be used for several carraiges as well as a new mantle for the fireplace.

I'll be taking lots of pics along the way and do up a whole "how I did this" photo essay. I'm hoping to have it done by the end of March. I NEED to have it done by the end of May so I can use it in a big medeival art/science competition.

GGaskill · « **Reply #1 on:** January 31, 2007, 10:10:12 AM »

Your drawing shows pretty small diameter trunnions. What kind of shot will you be firing? If it's heavy, I think you should have more robust trunnions.

Powder keg · « **Reply #2 on:** January 31, 2007, 12:03:08 PM »

I second George. Other than that Itlooks like Fun! Can't wait for pictures.

Wees

Don Krag · « **Reply #3 on:** January 31, 2007, 12:58:31 PM »

They'll be from 3.5" dia stock. Probably not to scale in the pic. Should they be wider? I figured 3.5 could handle the shock well. I might have some other thicker stuff laying around. If not, I could certainly find some at the scrap yard.

Cat Whisperer · « **Reply #4 on:** January 31, 2007, 01:17:51 PM »

Is not the rule-of-tumb that the trunion diameter should be about what the bore diameter is?

Two functions here - bending and attachment. Both are stronger with larger diameter.

GGaskill · « **Reply #5 on:** January 31, 2007, 02:21:17 PM »

OK, 3 1/2" should be OK unless you are launching lead shot. The size on the drawing looks a lot more like 1" than 3.5". Make sure you get a substantial weld joint.

copdoc · « **Reply #6 on:** January 31, 2007, 02:29:22 PM »

Nice. Can you show us how the elevation device works. I have had to modify some I built also. I usually did this to use materials I already had. In the 15-16 century almost all were different but similar so it does not matter.
Here is a pic of the first real cannon I ever built in 1975-76. I did not post it because it earlier because you might laugh at the crudeness of it. It works very well and has fired hundreds of rounds. The "caps" are handtruck wheel bases inverted. You lock the trunion with the bolt. I now know the trunnions are too small but we have shot about everthing you can stuff down a bore. In the eary proof testing days we shot charges heavey enough to flip it over backward. The bore is 2" trunnion is about 9/16th I think. I do not have a recent pic with a powder can but will add it later. The bolt through the trunnion cap works very well, it is just not authentic to the best of my knowledge. That is a wrench on the top of the cap. copdoc

Powder keg · « **Reply #7 on:** January 31, 2007, 04:47:58 PM »

3.5" should B OK. I think that is what my Bowling ball mortar is? I'll check tomorrow.

Wes

Don Krag · « **Reply #8 on:** February 01, 2007, 06:05:29 AM »

The powder chamber "bore" will be about 2.5, so I used that as ye ol' thumb guidance. That and I have a section of 3.5" rod laying here handy.

Here's a very rough sketch of the crank. There's a pretty good pic od one from a treatise document showing a view from the rear of a period one.

It's pretty much just a winch like on a boat trailer, with a rod spanning the opening between the base sides where the rope winds as it's cranked. I'll scan in the actual pic from the book this evening.

The fun part about the 15/16th century is that they tried just about everything from laying the tubes on blocks, to very sophisticated mounts with all sorts of rods, ropes, thingamabobs and doohickies. Like Copdoc said...all were different, yet achieved the same thing. Pretty much anything goes. I ran across the winch pics and it seemed pretty basic, easy to install...and it actually should work well using historically correct non-stretchy rope. I should be able to hand-forge all the required pieces.

P.S. Looking at my sketch...the winch is pretty dinky looking. Obviously, the crank assembly would be larger to fit the scale of the mortar...but you get the idea.

copdoc · « **Reply #9 on:** February 01, 2007, 11:59:21 AM »

Very nice. Now I am looking for another piece of steel. I like this design. Where is the "original" or original drawing? It would be helpful to have someway to lift it. See if you like this.

Don Krag · « **Reply #10 on:** February 02, 2007, 06:30:57 AM »

Yeah, I was thinking about mobility last night. The whole thing will probably wiegh in around 275 lbs. It'll definitely need some eyebolts and such to rope it onto a cart!

Here's the originals:

Color illumination from Military Treatise by Wolf von Senftenberg, 1570, as shown in "Medieval Warfare, H. W. Koch

The sketch actually shows a rocker supporting the bottom of the mortar and the rope pulling that. That might be a better idea since it would take some of the force off the trunions and support structure around them. Plus, the rockers look kinda cool. Never rule out the "cool" factor.

copdoc · « **Reply #11 on:** February 04, 2007, 04:45:02 PM »

Quote

Never rule out the "cool" factor.

I agree 100%. I like this design a lot. How does the "rocker" work. It looks like the trunnions will be well supported by the steel sides. Are the steel sides to support the "rocker"?

Don Krag · « **Reply #12 on:** February 05, 2007, 06:32:31 AM »

On this type design, the rocker is pretty much a curved-bottom wedge that fits in under the breech of the mortar and contacts the base directly below the plane of the trunions and the centerline of the steel support. Some models show pins on very large rocker arms for setting the angle, others show smaller ones that look like nothing more than support btween the mortar breech and base.

Will Bison · « **Reply #13 on:** February 06, 2007, 07:02:21 PM »

Don;

I really like the looks of that design. A bit different from the norm.

Oh, BTW, I like your web site.

Bill

Don Krag · « **Reply #14 on:** February 10, 2007, 06:41:32 PM »

Thanks Will! It's in sore need of updating, though. Most of the pics are from over a year or two ago, and most of the techniques are 3-6 years old!

HTML-ing about it just isn't as much fun as actually doing it...so I tend to procrastinate.

The smoothness of the design is what caught my eye. It just looked cool, and wasn't what I typically think of when Ithink of medieval ordinance.

Well, the mighty oaks have fallen and the field closest to the shop is starting to get covered in sawdust. I'm using an 18" chainsaw to rip oak trunks lengthwise. I can usually cut about a total of 20 feet worth of 16" wide oak before the blade gets too dull to do a good job. I'm getting a crash course in chainsaw sharpening by milling down a pair of 40-50' oaks!

Here's some of the slabs off the one we cut this past weekend. The big ones are ~4" thick, 18" wide and 62" long and weighed a hair over 200 lbs each fresh cut! One will be a new mantle, the other will be carriage parts. The motar base will be cut tomorrow off another one that *should* be dried out. It was a 28" dia oak, so I'm hoping to get the base slab in one piece. Although only having an 18" chainsaw may result in it being about 4 pieces!

Here's the "sawmill" area with a couple slabs in progress and one more big section about to get cut up.

This piece was cut up for project # 2, a small bombard styled off some Italian models. The wood has some nice grain. After drying a while, it'll get planed down using a draw knife, then scraped and slathered with multiple coats of linseed oil.

Some of the wood will go towards project #3 (hopefully this August), a copy of a Maximillian cannon from ~1500. Here's the small sketches for it. The bore length will be about 50". I'm sure some numbers might change based on materials and methods available at the time, but the basic carriage frame can be built!

The stump base will be a new 28" x 18" lx 2" end-table top...check out the cool spalted figuring! I try and make my wife furniture and such when I do things like this. A new mantle and some end tables was a good trade for three cannon carriages and wheels!

So who's humming: .....I am a lumberjack, yes I am.....?

CU_Cannon · « **Reply #15 on:** February 11, 2007, 04:49:51 AM »

It’s nice to see someone else who has a million and one projects going at the same time.

You have some great oak to work with. I would wait quite a while to do anything with it though. Oak that thick will take a year or better to dry and another 3-5 to stabilize. If you try to use it too soon it will shrink and split. At a minimum I would wait a year even then you will most likely have some movement still. For a bombard this might be ok but for that mantel I would wait a while.

I cant wait to see more building pics.

Don Krag · « **Reply #16 on:** February 11, 2007, 06:54:49 AM »

I use a greenhouse for drying...a makeshift wood kiln! It usually takes about 3-5 months for 2" thick slabs to dry out enough that they wont check upon further drying. Although I've noticed that they will warp slightly if used at that point. I keep everything stacked up with 1-2" spaces inbetween. Their own wieght keeps enough pressure to hold them to shape while curing an additional time.

For the mortar base, it'll get 1/8" x 2" steel banding in three places, so I'm not too concerned for it. I don't know that I would care if it had minor cracks all over for that matter.....gives it character.

Yeah, the mantle and table tops will be a while, though! Compared to oak prices for slabs this big and nice grain from commercial places...I can wait!

All my steel should be arriving early next week...I feel like our sons waiting on Christmas morning!

Powder keg · « **Reply #17 on:** February 11, 2007, 08:19:01 AM »

Quote from: Don Krag on February 10, 2007, 06:41:32 PM

Although only having an 18" chainsaw may result in it being about 4 pieces!

You might try a rental place? They might have a bigger Beaver?

Wes

dominick · « **Reply #18 on:** February 11, 2007, 09:33:14 AM »

Quote

Oak that thick will take a year or better to dry and another 3-5 to stabilize.

You can make a steel carriage in the meantime.

EL Caz 66 · « **Reply #19 on:** February 11, 2007, 09:53:49 AM »

Hey Dom, It's funny you said that, I was just thinking to myself I wonder if Dom could make that entire old 15th century cannon out of steel.. I might just add that one to my micro artillery collection... If you can swing me an email..

Later, Ed

EL Caz 66 · « **Reply #20 on:** March 16, 2007, 01:44:48 PM »

And here it is a replica of a 15th century maximillian cannon in all steel .50 cal. added video click on the link.

http://www.youtube.com/watch?v=QBPK3mpmZ6w

click on the link

Don Krag · « **Reply #21 on:** April 24, 2007, 05:37:28 AM »

Well, I finally have all the lumber rough hewn. I'm not quite sure how to work down/true-up 8" x 18" x 48" oak slabs with my limited wood working equipment, but it ought to be fun finding out! I got the arrangements made for the breech section to be bored out for me. I'll pick it up probably Friday. The next major task will be heating up a 170 lb, 10" dia cylinder and pressing in the 6" dia breech/powder-chamber! I'm thinking and engine hoist to hold it in my large crucible furnace will be the best bet. Take it up to 900*F or so and cool the breech down in a deep freeze or a cooler with dry ice. Don't worry...I'll video the whole episode.

I've already started doing the iron hardware parts with some wrought iron strapping and old wagon wheels I have. I still have a few construction kinks to work out...but nothing too major. I'm still hoping to have it done by memorial day!

Don Krag · « **Reply #22 on:** April 25, 2007, 02:16:51 PM »

Here's the breech section after putting in the powder chamber. The chamber was first drilled to 2" dia, 3.25" deep, then chamfered at 30*. I've smoothed the top and chamfered sections, now I'll clean up the inner chamber. The block is 6" dia by 6" long.

Hopefully I can get most of it done for a display piece over memorial weekend, if not fully functional by then.

Don Krag · « **Reply #23 on:** May 14, 2007, 02:48:04 PM »

Woo Hoo! One hurdle down! I got the breech section inserted. I had to take it back and turn it down another 50/1000ths. I ended up with 8-10/1000ths over. It slid in with no problems and even a bit of "rattle" with the breech cooled with ice and the tube up around 800*F. My wife graduated with her teaching degree this saturday so I had three of the brothers-in-law handy to help....one to man the video, one to help lift, and one to dial 911 if needed!

The video is quite funny. I'll try and get it uploaded in the next day or so. Only a few fingers got singed. It turned out the main tube was 1" larger in diameter than my furnace opening. We had to improvise on the spot and a 170lb steel section is difficult to manhandle when heated up! It's been welded up and pinned and will still get a couple enforcing rings added for show. next up will be the trunnions, but those will be fairly straight forward.

Cat Whisperer · « **Reply #24 on:** May 14, 2007, 03:42:53 PM »

Don -

Thanks for posting the pix! It's great seeing how others fit things together.

AND jogs the thinking processes - like - I've got a few pieces of steel like that!

Rickk · « **Reply #25 on:** May 14, 2007, 04:07:32 PM »

Hey Don,

You mentioned your crash course in chain saw sharpening.

Here is a link to a book that changed my chain saw sharpening life:

http://www.oregonchain.com/tech/ms_manual/ms_manual.pdf

It shows the part of the saw blade that actually does the cutting, which I think most people (myself included) do not intuitively know. Once I realized what part does the cutting, all that worrying about angles went away and I just held the file (no guide or jig or handle needed) in the correct angle without any effort at all.

I cut about 12-15 cords of wood a year, to heat with wood. I have other things in my life to do as well, so I try to make it as quick and easy on myself as I can. I did get an Oregon chain saw grinder, which I use maybe 2-3 times during the life of a blade to fix it when it really gets messed up. I sharpen it with a file between gas fillings.

Before I "read the book", there were times when I sharpend it with a file, a fancy jig and a handle and made it cut worse instead of better.

Now the chains seem to last much longer with very little effort at all. If they are sharp, they don't get hot, and if they do get hot, they won't stay sharp.

I can tell btw that you do seem to have a handle on your sharpening technique as there are no obvious burn marks in the wood.

I think for cuttings like what you are doing a brand new bar would be appropriate. Personally, I am hard on bars. I have a 20 incher on my 73 CC saw and a 24 incher on my 100C saw. The nose sprocket gets replaced after two chains are worn out, and after two more chains are worn out the bar is pretty much toasted. I can usually cut about 4 cords of wood with a single chain. MOst of the bad things that happen to a bar seem to happen when taking trees down, not cuting them up.

The sprocket gets replaced after every two chains as well, as a worn sprocket will stretch a new chain.

Long before I give up on a bar it is no where near perfectly straight (slightly twisteed) and the rails are not close enough to being even that they can be filed flat, so there would be no way to cut a straight line that long with them. For firewood a bit of a curve never mattered. A brand new, perfectly straight bar is definitely the way to go for board makin'.

Also, fresh cut logs are way easier on chains than stuff that has dried a bit.

You maybe already know all this... anyone who uses a saw can benefit from checking out the Oregon book though. They have a hard copy of the book that is free for the asking... great reading material for the "boy's room"