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Discussion Starter · #1 ·
Nobody yet has discussed how to add sights to their cannon without altering it in some way. We believe that most of you out there have access to scrap aluminum and have a hacksaw, an electric hand drill, a coping saw and some sand paper. You also need a set of iron sights or a scope and mount, These can be removed from a rifle that you don't use much anymore, just like we did. We call this piece of sighting equipment a "Sight Base". Since everyone's cannon has a different profile, we think that detailed drawings of our sight base for the 100 Pdr. Parrott are simply a waste of time. If you see detailed photos of our sight base, we think you can make the necessary sketches to fashion one to fit your unique cannon configuration. Also, it's important to note that we copied this idea from several we saw being used in competition at the Casper, Wyoming Annual Cannon Shoot in June of 2005. As long as you use iron sights and do not exceed the length of your tube, they say OK to this type of sighting equipment.

We found, with more than 100 rounds fired, that this type of sight base repeats very well, indeed as you take it on and off your cannon. We measured less than .0001" positional deviation in a 25 repetition test. Some smooth-bores are very accurate, but you will never know if you don't have sights on your gun OR have the skill displayed by the members of the South African Cannon Club including our own DD.
 

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Mike and Tracy, I'm always impressed with your ideals and craftmanship!!! Having seen some of it in person, I know what i'm talking about. I will never forget those long range shots, very impressive!!!! when I get the time? i'll be making a small cannon and will copy your ideal for a removeable sight base. will probably use iron sights, I think a scope will be bigger than my cannon barrel,small lathe ya know ;D ;D ;D
 

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I went totally simple.... the rear sight from an '03 Springfield and some epoxy glue. Nowhere near authentic but works for me.

 

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Discussion Starter · #5 ·
Sure can, DD. We will find the right photos, resize them, upload them and post as a mod. to this post. Basically, the 1/4" ball bearings are placed where they will limit all four degrees of movement. Rotation about the -X- axis is stopped by a cylindrical bearing glued into a v-notch in the outrigger assy. which positions the bearing against the top of the right trunnion. Rotation about the -Y- axis and the -Z- axis is stopped by the fore and aft ball bearing pairs which bear on the tube's reinforce at the breech end and the cylinder shape near the muzzle respectively. Movement along the -X- axis is stopped by the ball bearing stop which contacts the forward reinforce face. Photos later.

Evil Dog, The first scope we ever mounted on a cannon was on a scope base that was J B Welded directly to the reinforce. As you said, it works for you. Well ours wasn't "authentic" either, but it worked just fine and never fell off!

Regards,

Tracy and Mike
 

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Discussion Starter · #7 ·
The original sights worked very well and our miniature sights are made just like them and they worked well on our 1/6th scale prototype rear sight along with the scale front sight blade, but on the prototype the rear aperture was .060" and on the production model it is only .010" which is impossible to see through. Those simple pin sights probably work, but we wanted absolute repeatability so we could test the accuracy of various forms of rifling. We eliminated all the variables that we possibly could in this effort, just like the competition shooters do.

Do you think certain dimensions are required here, or are these photos good enough??

Thank you,

Mike and Tracy
 

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I am always amazed at the amount detail and precison you guys work to. It is fascinating. I don't think detailed measurements are necessary as they would apply only to your gun. Any critical measurments in such a mount would apply only to the gun profile to be used. Anyone wanting to build a similar device should be able to copy from the picture and apply their specific measurments and build this mount.

Details about how you made the bearing points and came up with the measurements might be helpful however.

However, Don Quioxte must tilt at your windmill. Gray Duct tape? At what torque was it applied? Was it applied in ozF-in or mN-m? Applied over an unsupported section with only one right length like it is, Gray Duct tape will cause pitch and roll in the mount. Since you are removing and reinstaling the sight between shots the variation could be extreme. Everyone knows you should use green duct tape for precison work... ;D ;D ;D
 

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Discussion Starter · #9 ·
DARN!! I knew someone would spot that tape. A stiff breeze from 3 o'clock is our only excuse. The first time out with that big ole K-12, we were afraid it would act like a sail and blow away! Next time we will definitely use properly tensioned GREEN DUCT TAPE. Thanks for the word on dimensions; we believe you are correct here.

We made the bearing points out of standard hardware store 1/4" ball bearings which were J B Welded into drilled, 1/4" holes of a depth that would let the bearing protrude by 1/8". There are only two critical dims. on the whole thing. ONE, you must make sure that the top surface of your main, (longest), aluminum top plate is equidistant from the bore axis at both the breech AND the muzzle ends. To do this measure the breech dia. and muzzle dia. and divide by 2 at both ends. Subtract the longer distance by shorter distance. Now you know the difference in height of your front and rear supports. An accurate sketch is very important for constructing the sight base. You want your scope mounted parallel to the bore axis so you have all of the scope's adjustment to use for sighting. TWO, also make sure that the position of the -X- axis ball bearing stop is the correct distance from the center of the pin bearing on the outrigger so the pin bearing contacts one of the trunnions reliably each time you mount the sight base. We used flush mount, flat head, socket screws in various lengths to bind the pieces together.

Users of only Green Duct Tape,

Tracy and Mike
 

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Nice mount. How does the aluminum do with changing temperature? I'd think the expansion and contraction of aluminum would be somewhat undesirable and you may want to try an improved model using more stable cast iron. If you are only firing at pretty much constant temperature, I guess there won't be a huge problem.
 

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Discussion Starter · #11 ·
cannonmn, Nice to hear from you. We sure did like your display at the Mansfield Artillery Show. You know, considering that Mike and I have more than 56 years of Aerospace and Aircraft Industry inspection and calibration experience, we were a little concerned about the effects of thermal expansion on the main, lengthwise member in the Sight Base assy. We did a few preliminary calculations and decided to go ahead with aluminum because it is so much easier and cleaner to work with than cast iron which we also considered. We outlined several experiments to perform on the prototype sight base which is almost identical to the one we use today. We always go to the high plains north of Denver, Colorado to do our accuracy testing where the temperature can rise 20 degrees in four hours. From May to September, our shooting season, we can expect it to be about 70 deg. F. when we start at 7 o'clock and about 90 deg. F. when we halt our cannon testing at 11 o'clock. On average, a 5 deg. F. rise can be expected per hour. We are deliberate, methodical and slow in our cannon shooting. We shoot one 5-shot group per hour, that's all.

Our experiments duplicated these conditions as much as possible in our climate controlled calibration lab where we calibrated precision Gage Blocks for industrial customers for eight years. The tolerance on these blocks is plus or minus .000002" ( 2 millionths of an inch). The sensitive Swiss and German electronic indicators we used are the same ones we used to calibrate these measurement standard, gage blocks. We made careful measurements of the length expansion and the up and down deflection of the main bar, the height expansion of the support pieces and the side to side deflection of the main bar during a five degree rise in ambient temp. over one hour. Remember that the expansion ratio of aluminum is 13 millionths of an inch per inch per 1 deg. F.

Maximum length expansion was .00018", (one ten-thousandth, 80 millionths), a little less that the theoretical, .00025" possible.

The height rise or depression in the bar's mid-point was only .000017", ( 17 millionths of an inch), a minuscule rise.

Height expansion of the front support was .000026", ( 26 millionths of an inch).

Height expansion of the rear support was .000015", ( 15 millionths of an inch).

Side to side deflection was so small as to not be seen on the electronic indicator's meter.

So, the height expansion differential of the supports, a paltry 11 millionths of an inch, is divided by 19.5", the length of the main bar, and we get a result of one-half millionth of an inch per inch. No effect on target could be measured from this at all. Assuming you have wisely designed your base so as to rest each of the ball bearing sets on a non-tapered tube surface, this tiny length expansion will not change the way your scope is pointed or iron sights are pointed so there are no effects here at all. The only possible effect could come from a rise or depression in the middle of the main bar. So let's be really cautious and conservative here and say you got hold of a really bad piece of aluminum for the main bar which was .50" X 1.50" X 19.5", our bar's dimensions. Let's assume that it had four times as much deflection as our test showed in the middle of the bar.

Using these worst case numbers, we find that the worst aiming error you could possibly expect at 100 yards is a tiny .025", (twenty-five thousandths of an inch). Remember, our actual test results would only support one-fourth of that number, a paltry 6 thousandths of an inch. Hard to measure that effect when the winds can blow your bullet off target by whole inches!

Do the math yourself. 4 X 17 millionths is 68 millionths. That is the height of your right angle triangle. The base dimension of the triangle is 19.5" divided by 2 or 9.75". So, to find the deflection of your scope reticle at 100 yards we do a basic proportion formula. This is the one we always use, so we don't get confused.

The height is to the base dim. as X is to the number of inches in 100 yards or 3600"
.000068" : 9.75" = X : 3600"
This ratio formula is always solved this way: factor 1 x factor 4 divided by factor 2 = X, so we calculate it like this:

.000068" x 3600" = .2448" divided by 9.75" = X

X = .025"

Frankly, this result doesn't even register on our "Oh Crap-O-Meter" which accurately measures real problems we encounter in the shop every day.

Incidentally, less technical questions can be answered by much less blather!! :) :) :) :) :)
Best Regards,

Tracy and Mike
 

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Now i'm scared to even try and make a removeable sight base..........great big math formulas, two colors of duct tape, too much for me ;D..... I think i'll kinda just copy Double D's simple sight ideal and whittle out a stick and stick it in the vent ;D ;D ;D
 

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Ahhh but to have the OPPORTUNITY to say, "I missed that shot because my SIGHT was off by 68 millionths! - Well, back to the shop."

;D
 

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Thanks for the explanation. Just wanted to make sure you weren't cuttin' any corners on us!

We've used an aluminum dovetail mount held on with two large stainless steel hose clamps. It works well for us when we can keep it from moving during recoil, which we don't always achieve. We leave it on while firing since it takes a while to get on and off. We also use optical boresights we plug into the muzzle between shots. But basically we're not striving for extreme precision at all, we're happy if we can get rounds on a 4x8 plywood sheet at 100 yards.
 

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Discussion Starter · #15 ·
Lance, You don't have to use any math formulas to get this sight base made. Just approach it like one of your excellent, precise woodworking projects and we are absolutely sure it would turn out just fine. Hope you will do it some day!

CW, You know what, you're right. We will add that one to our own list of "reasons", not excuses, for missing a shot. We now have these: bumble-bee on the rear sight, fly on the front sight, excessive mirage, sudden lull in the 20 mph wind from 9 o'clock when you have the rear sight cranked way over to the left to compensate, piece of grit in my eye, not enough sleep, etc., etc.

cannonmn, Those optical boresights look like they work great; we saw one in use on one for your clips. As for the aluminum dovetail mount, may be a few drops of J B Weld would work. We found that a sharp whack with a plastic mallet knocked our mount off our cannon breech before we started using the sight base. All of the epoxy would pop off too. Just a possibility.

Regards,

Mike and Tracy
 

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Mike and Tracy, i'll build one with a scope, been wanting to try some experiments. I only need 3 things, a picture, an ideal, and time to do it. You've provided the first 2 things, many thanks!!! Don't be looking for any pics of my mount, untill let's say, early spring, maybe late summer..........
 

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Lance quite frankly for sighting like Mike and Tracy you could make a base out of wood. For what Mike and Tracy were doing their sight base precision far exceeds the precison they were trying to measure. They just worked in a medium they are familiar with, so should you.

For others this amount of prescision...


Produces this result...
[img]http://www.fototime.com/A02A0C7871330D8/standard.jpg

...and that is good enough.

But honestly I have my doubts how good my sighting method would be at a distance...but after March I hope to find out.
 

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I love that scope mount! I've had my eye on it ever since I saw it in the very first photos of the Parrott.

I started something similar not long after I finished my Napoleon. I was going to use aluminum barstock and a rifle scope on a Weaver-type base. I already had the aluminum and got as far as buying the base and rings (still in the package), then lost interest in the project because "no one else was doing anything like that."

I used the aluminum for another project and haven't really given it any more thought until now. This thread has kind'a rekindled the idea and I may yet build something but it probably won't resemble my original design. Now I'm thinking maybe a Red-Dot or a low-power pistol scope instead of the rifle scope. A high-power scope on this gun doesn't make that much sense now that I've fired it a few times and seen its limitations.

I know that there's potential there for more accuracy than I'm getting, but only so much. To put precision optics on this smoothbore could be an exercise in frustration.

M&T have the advantage of a gun that is capable of consistent long range accuracy.
 

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O.K. guys, here's what i'm thinking about doing. everybody knows i'm a big kid and likes to play all the time. years ago i had fun shooting iron chickens. well now i want to shoot iron IRONCLADS, maybe a bit bigger than the chickens, i can cut them out with a torch. anyway, been thinking about buying the 1/7 scale 9" Dahlgren with Marsilly carriage from South Bend Replicas. it's 1" bore,barrel length 19", and weighs 55lbs............... the CSS VIRGINIA {that would be me} wants to use my captured Dahlgren to knock over some ironclads- a bit bigger than chickens. i don't know how far or accurate the SBR 1" smooth bore will be good for, but i'm thinking it would be fun to play with. also thinking Mike and Tracy's scope mount would help to knock over those ironclads. what ya all think?
 

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Discussion Starter · #20 ·
Wow. We had no idea that such a simple idea could generate this many creative comments. Mike and I are not competitive shooters, buy we keep remembering what the late Ralph Bone, one of our gunsmithing school instructors said in 1976. "Tracy, I wouldn't give two pinches of sour owl "feces" for an inaccurate rifle". An extraordinary custom riflesmith and an accomplished knife maker, he also could artfully engrave all that he made. He also told Mike and I to read the books and articles by Col. Townsend Whelan. Col Whelan repeated many times in his writings that,"only accurate rifles are interesting." I guess our quest to find accurate shotguns, rifles and pistols, and now Cannons started with that bit of advice.

Don't forget that smoothbores can be accurate too. We have seen 6Pdr. cloverleafs at 100 yards and 15 inch groups at 200 yards with the same. Smaller calibers can do very, very well. Lance's 9" Dahlgren Shell Gun made by South Bend Replicas, is not only a great looking cannon, but can be expected to give our smoothbore 1/6 scale 100 Pdr. Parrott made from a 1/3 scale Parrott South Bend 10 Pdr. as our 2002 Prototype, a run for the money.

Strange as a wood base sounds, Double D is most likely correct here, If the humidity rises more than 20% in an hour you are being swallowed by a nasty storm front and you should leave the area quickly! Warping occurs over time, more than a few hours! Stable woods like oak, walnut, maple and mahogany would be our favorites.

Terry C. You should have no technical difficulty building a sight base; motivation could be provided by asking yourself the following question, "Without some form of sights directly on the gun or on a sight base, will I ever REALLY KNOW if my smoothbore cannon has some inherent accuracy?"

Good luck to you all!!

Mike and Tracy
Seacoast Artillery Company
 
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