Author Topic: Long Cecil (Read 12673 times)

Double D · « **Reply #30 on:** October 25, 2011, 05:03:41 PM »

Never heard of that before but it's reasonable. Illustrators are known for getting threads wrong, draftmens get them right.

Cannoneer · « **Reply #31 on:** October 25, 2011, 10:05:46 PM »

This may be one of the miniatures that KABAR made reference to. I've seen a couple of these 'Long Cecil' all steel models on the block at different auction sites.

shooter2 · « **Reply #32 on:** October 26, 2011, 01:44:35 AM »

These are photos I took of the Long Cecil Model at the Watervliet Arsenal. It was listed as 1/12 scale and one of 360 made by the Pratt and Whitney Company in 1903. Enjoy.

shred · « **Reply #33 on:** October 27, 2011, 05:00:09 AM »

Quote from: Double D on October 22, 2011, 05:14:57 PM

There is available on line a book that also includes a good description of how the gun was made. The Diamond Mines of South Africa: Some Account of Their Rise and Development http://www.archive.org/details/diamondminesofso00willrich/cassellshistory00danegoog

It is an interesting book covering the era of the start of diamond mining in SA. I ordered a print on demand copy...

Another online source about this gun is from the South African Military history Society. http://samilitaryhistory.org/vol041dp.html

Wow, I just read through the parts on Long Cecil and the siege of Kimberly. Amazing piece of history I had no idea about until now. Kind of the ultimate home-build

Double D · « **Reply #34 on:** October 27, 2011, 05:23:17 AM »

Quote from: Double D on October 22, 2011, 03:19:51 PM

Long Cecil-Williams-727 [Public domain or Public domain], by Book: Williams, Gardner Fred, 1842-1922, Photos not attributed, from Wikimedia Commons.

Look again at those breech threads...they are not left hand, they are right hand....that is a cut away drawing of the breech plug and the threads are on the back side of the breech plug.

Double D · « **Reply #35 on:** January 27, 2012, 10:04:03 AM »

The obturator pads in the Long Cecil were rings of sheet asbestos soaked in tallow. Any one have any suggestion for obtruator pads for this build?

Thread pitch. The breach plug thread is listed 3/4 inch pitch, The Elevating screw is listed as 1/4 inch.

If I understand this correctly a 1/4 inch pitch would be 4 tpi. My mind keeps 3/4 inch pitch would be .75 tpi. Is that correct...geez what number do I hit on the thread dial for that?

Zulu · « **Reply #36 on:** January 27, 2012, 10:39:04 AM »

DD,
If 1/4" pitch is 4 tpi, wouldn't 3/4" pitch be 1 1/4 tpi?
Zulu

Cannon Cocker · « **Reply #37 on:** January 27, 2012, 01:03:51 PM »

Quote from: Double D on January 27, 2012, 10:04:03 AM

The obturator pads in the Long Cecil were rings of sheet asbestos soaked in tallow. Any one have any suggestion for obtruator pads for this build?

What about the obturator that Moose53 uses for his breech loaders. The tapered rubber stopper sandwiched between steel discs. A photo is shown in his 40mm breech loading build and another time under Whitworth or Breech loaders I think. I liked it so much I am copying it for a Whitworth style gun I am building right now. Sure beats greasy pads, not to mention trying to get a hold of real asbestos. If you do have to have asbestos, look on ebay for a heavy glove used for ceramics and kilns etc. I have one that's 50 years old, but you can't cut it up for your gun. I use it for casting lead and zinc.

GGaskill · « **Reply #38 on:** January 27, 2012, 02:08:29 PM »

Invert the pitch to get TPI. 1/4" pitch is 4/1 TPI; 3/4" pitch is 4/3 TPI (1.333 TPI.) I think you would need a special gear for that. In metric, 4/3 TPI is 19.05 mm pitch. Not sure whether your lathe does metric or if that is a choice on your gear box.

Zulu · « **Reply #39 on:** January 27, 2012, 02:14:19 PM »

Quote from: GGaskill on January 27, 2012, 02:08:29 PM

Invert the pitch to get TPI. 1/4" pitch is 4/1 TPI; 3/4" pitch is 4/3 TPI (1.333 TPI.) I think you would need a special gear for that. In metric, 4/3 TPI is 19.05 mm pitch. Not sure whether your lathe does metric or if that is a choice on your gear box.

I really wasn't sure I was right. Obviously, I wasn't.
Thanks for setting me straight.
Zulu

Double D · « **Reply #40 on:** January 27, 2012, 03:05:16 PM »

Thanks. My lathe will only cut down 4 tpi.

The minor internal thread diameter of the breech for long Cecil was 4.25 inches. I am going to stick with standard for this thread. I haven't decide what caliber I am using yet. Still looking for a barrel

50 cal breech plug 5/8"-11tpi
20 mm cal breech plug 1"-8tpi
30 mm cal breech plug 1 1/4"-7tpi

Cat Whisperer · « **Reply #41 on:** January 27, 2012, 04:27:28 PM »

Quote from: Double D on January 27, 2012, 10:04:03 AM

The obturator pads in the Long Cecil were rings of sheet asbestos soaked in tallow. Any one have any suggestion for obtruator pads for this build?
...

We used a silicone rubber sheet for high-temperature applications - very durable. You could use layers of it (about 1/4" thick). McMaster Carr.

seacoastartillery · « **Reply #42 on:** January 27, 2012, 06:37:54 PM »

Quote from: Cat Whisperer on January 27, 2012, 04:27:28 PM

Quote from: Double D on January 27, 2012, 10:04:03 AM
The obturator pads in the Long Cecil were rings of sheet asbestos soaked in tallow. Any one have any suggestion for obtruator pads for this build?
...

We used a silicone rubber sheet for high-temperature applications - very durable. You could use layers of it (about 1/4" thick). McMaster Carr.

Double D., Cat Whisperer, Why the heck would you want to re-invent the wheel on this technically difficult area of function, the propulsion gas obturation? Why not use the same materials and proven design used by Moose53 in his 40mm breech loader, the build of which is described in his thread on that rifle posted sometime last year and which he will use again on his recently described Bowling Ball breech loading mortar, an expansion of the 3.6 inch rifled mortar of 1890. His 40mm breech design is a DeBange variant, and, as such, works very reliably.

Tracy

Double D · « **Reply #43 on:** January 27, 2012, 07:45:23 PM »

Who is reinventing the wheel, I asked for suggestions.

Do you mean the rubber plug?

So if I make de Bange washers from the silicone rubber sheet as Tim suggests of the correct thickness what is the difference between that and Moose's plug.

So here's what I need.

.50 cal .244 thick use .250
20 mm .384 thick use .375
30 mm .488 thick use .500

http://www.rubbersheetroll.com/silicone-rubber-high-temperature.html

Stuff ain't cheap.

KABAR2 · « **Reply #44 on:** January 28, 2012, 03:19:48 AM »

DD as far as the threads go I am not sure the drawings show the threads in the rear as a cutaway, look at the last drawing it also is sectioned near the debange ......... the threads are a gost image to allow you to see under them....
also http://i.imgur.com/PiT2J.jpg as to photo's negitives many times are reversed by accident..... I don't know howmany times I have seen left handed guns in old photo's many times the film or the negitives were sent on to the newspaper and they had no refrence as to right or left they sometimes were reversed....... I have also seen this even in recent movies..... a good example was the "Rough Riders" movie with the left hand feed maxims.......
.
.
Sorry if I am opening a can of worms again with this........
Now I had mentioned a long time ago that it may have been theaded opposite of the twist of the rifling...... depending on the direction of twist on the barrel you use right or left hand you may wish to thread the breech opposite to the rifling...... the British had a funny way of doing things in custom sporting guns you could get either right hand twist (north of the equator) or Left hand twist (south of the equator) did not translate to military arms and not sure if the engineer knew about this little quirk in English gun making and would have bothered to apply it to artillery.... but it is another possible factor in the equasion.....

Double D · « **Reply #45 on:** January 28, 2012, 04:19:02 AM »

No, looking a the drawings and other photos it is very clear these are right hand threads. The threads in all the drawing I have rounded up so far very clearly drawn as hidden lines.

Thanks to Shooter2 I have a copy of Edward Goffe's August 1900 article in American Machinist Magazine describing the construction of the gun. Goffe was the chief draftsman on the project. In his description of the breech plug he does not mention direction of thread. That seem to me to be significant issue and would have been noted. The article did not the gain twist.

It is a good though Allen.

Cat Whisperer · « **Reply #46 on:** January 28, 2012, 06:48:06 AM »

Quote from: Double D on January 27, 2012, 07:45:23 PM

Who is reinventing the wheel, I asked for suggestions.

Do you mean the rubber plug?

So if I make de Bange washers from the silicone rubber sheet as Tim suggests of the correct thickness what is the difference between that and Moose's plug.

So here's what I need.

.50 cal .244 thick use .250
20 mm .384 thick use .375
30 mm .488 thick use .500

http://www.rubbersheetroll.com/silicone-rubber-high-temperature.html

Stuff ain't cheap.

That's the stuff.

If I remember correctly, the 155mm Self Propelled (M109) used a stainless disk with about an inch of neoprene showing between it and the breechblock.

Here's a link to Wiki: http://en.wikipedia.org/wiki/File:M109BREECH.JPG

Double D · « **Reply #47 on:** January 28, 2012, 07:28:09 AM »

Thanks Tim for the confirmation,

I can't really see any reason to not just duplicate the final version of the breech block used on Long Cecil. It is what they came up with after two other designs failed.

After looking at this project for a while it looks like logistically (lathe size) and financially(big stuff is expensive) I am am limited to maximum size of 20 mm.

Anybody have a 24 inch piece of 20mm barrel for cheap!

Thanks to Shooter2 and the PDF he sent me I have enough info to draw up this gun.

Once I get the barrel, I'll work some drawings and send my letter off to ATF for permit to build.

Cat Whisperer · « **Reply #48 on:** January 28, 2012, 08:05:12 AM »

Since it's right-much small - let me send you a few scraps of the red silicone rubber sheets. Shall I send them with the boring bar?

Double D · « **Reply #49 on:** January 28, 2012, 08:22:30 AM »

Tim,

I'm going to take take you up on both offers.

Doors do not seem to be opening for the bowling mortar, but tooling is the issue. Perhaps If I had tooling in hand I would get a better reception.

Let me know the cost of postage...

Thanks!

GGaskill · « **Reply #50 on:** January 28, 2012, 01:15:25 PM »

So if the original was 4.1", a 20mm one would be about 1/5 scale, so the threads should be 6 2/3 TPI. Can your lathe do 7 TPI?

Double D · « **Reply #51 on:** January 28, 2012, 03:04:38 PM »

Yes very close to 1/5

I can do 7 tpi. I also have an internal threading tool for .75 bore I could use.

Might even be able to put the chamber in with 20mm neck and throat reamer. Any body know where I might borrow one?

GGaskill · « **Reply #52 on:** January 28, 2012, 06:48:25 PM »

Should be able to bore the chamber unless you are doing something tricky.

Double D · « **Reply #53 on:** January 28, 2012, 07:23:21 PM »

Quote from: GGaskill on January 28, 2012, 06:48:25 PM

Should be able to bore the chamber unless you are doing something tricky.

Nothing tricky, but I will probably need to put in a throat. I suppose I could just use some sort of taper reamer for throating and just bore a chamber, as you say.

KABAR2 · « **Reply #54 on:** January 30, 2012, 08:37:36 AM »

What are the specs on a 12 ga. reamer? it might be close enough for what you are doing I doubt the are too many people that have something in 20mm.......

GGaskill · « **Reply #55 on:** January 30, 2012, 12:27:13 PM »

I would think you could just set the compound rest at 2° and at the end of the chamber boring, feed in the compound until it's clear of the rifling.

Double D · « **Reply #56 on:** January 30, 2012, 01:40:52 PM »

That's an Idea George.

It's looking like this is going to be a 20mm barrel project.

Double D · « **Reply #57 on:** January 31, 2012, 09:21:27 AM »

Well the check is in the mail so to speak...sent this letter this morning.

January 31, 2012
Bureau of Alcohol, Tobacco, Firearms, and Explosives
Firearms Technology Branch
244 Needy Road
Martinsburg, West Virginia 25405 USA

Dear Sir or Madam,

In 1899 during the 2nd Anglo Boer War, the Boer Army laid siege to the town of Kimberly, South Africa. The British army forces defending the town were out ranged by the Boer Artillery and could not return effective fire. The engineers of the De Beers Diamond Mine used common materials found in the mine engineering shop and in 22 days built a 4.1 in breech loading field gun to engage the Boer guns. This unique historic gun became known as Long Cecil.

I wish to build a scale model replica of this gun. The gun will be built as a hobby project and will be used to shoot blanks for signal purposes and projectiles for target shooting.

The gun will be built as close as possible to the original.

•   It will have a miniature screw breech with an 1877 de Bang obturation system.
•   Loading the gun will be via loose black powder. For safety purposes the powder will be contained in tin foil packets.
•   Cast lead or standard surplus projectiles will be used for target shooting.
•   The original gun used typical mid 1800 friction primers for ignition. This model will not have sufficient mass to safely use friction primers so ignition will be via common black powder cannon fuse.

I am aware of the Antique replica provisions of GCA and NFA and since the original gun was made 1899 to 1900 I know it will not qualify as an antique. It may qualify under the antique ignition provision.

Please advise what if any permits are needed to build this model gun in either 1/5 scale using a surplus 20mm barrel or 1/8 scale using a surplus 50 BMG barrel.

Sincerely yours,

Douglas B Dickens

Cut Bank, MT 59427

Cross your fingers.

jamesfrom180 · « **Reply #58 on:** January 31, 2012, 10:17:48 AM »

Very nice letter, good luck with it.

One questions DoubleD, how much compression is the obturator in? I am actually at a loss on how to describe it but as the breach "plug" has threads and is threaded in, what is the linear length between the pad coming in contact with the breach's sealing edge and its final "closed" dimension?

Reading Colonel D.E. Peddle's article, he states that the obturators was a standard service pattern. It appears this is one of a couple factors in deciding what bore to build. Have you found that the long Cicil used surplus pads?

Double D · « **Reply #59 on:** January 31, 2012, 01:04:23 PM »

As I understand it the de Bange obturator pads are not compressed by screwing in the breech plug. The pressure of firing, forces the mushroom shaped obturator bolt rearward, compressing the pads, which seals the bore.

From the literature it appears the De Beers engineer s made their own pads from sheet asbestos and tallow.

Long Cecil's pads were 2 inches thick. Strict scaling says my pad in 20 mm will be .384 long by .816 diameter. Any body have any 9.75 mm high temp rubber sheet scraps. Like the engineers at De Beers I will adapt and adopt.