|Dec 31, 2012, 09:39 AM|
I think you are right. The pre-loaded tube cartridges are the most sure way to go.
The load is enclosed, low chance of spill or contamination, high accuracy, etc.
I tried my old set of tube cartridges with this new igniter design. The tube wouldn't even get a mm into the barrel because the igniter wire runs right up to the edge of the muzzle.
So I did a Frankenstein - a bit of "spoon" and a bit of "tube cartridge" to make the new loader. It is a spoon, but only with a narrow slot at the top to clear the igniter wire. Hopefully, the very narrow slot will behave more like the enclosed tube cartridges than like an open spoon.
Also, it has a built-in rammer to positively slide the load into the barrel, rather than dumping like with a spoon loader. To load, the wood dowel rammer is pulled out and a foam wad inserted from the back end. The rammer pushes the foam just to the point that it is visible at the back of the spoon slot. Then the BP is dipped out of a small can. Loader is inserted into barrel, and holding the wood rammer in place, the brass spoon/tube is pulled backwards, leaving the BP and foam in place in the barrel. That's a pretty similar process to using the pre-loaded tubes.
It will be slower on-site and more likelihood of spillage, but no pre-prep necessary.
Not ideal, I agree. Biggest remaining problem though, with any reload approach, is that the barrels get wet after they are fired, and any reload into even a damp barrel results in a dud.
Best bet would be to have a gun base with a barrel "shell" and a plug-in barrel. Then have many barrels. After a gun is fired, pull the whole plug-in barrel out of the base and insert a new loaded barrel. I will probably try that after I get the new multi-shot guns done on the port side. I'll still have the current 9 starboard guns that do have pull-out barrels, and an extra set of 9 barrels as re-loads.
I'm waiting for somebody to come up with the ultimate multi-shot, scale-looking gun system.
|Jan 01, 2013, 02:32 AM|
Some pics of the latest gun mod's.
Have the new polypropylene plugs - very easy to cut and drill. Since the plastic is also an insulator, using bare 1/16" copper tube as the power terminal with 0.012 nichrome (28guage) as the igniter wire.
Fired about 10 times. Very reliable. Polypropylene easily takes teh momentary high temp burst from BP ignition (m.p. is 490F)
Will be converting all barrels.
Great source for all sizes nichrome wire: www.PNJresources.com
Source for plastic breech plugs shown in pic.
|Jan 02, 2013, 09:50 AM|
Sliding Servo - Followup Notes
No pictures, only boring details, but likely important if you plan on using sliding servos. Took me a lot of playing around, but when I got it set up right it works really well. Very repeatable rotation, almost zero play in rotation and very
full yard rotation.
1. After yards are fully rigged, sails in place, and all rigging is in place EXCEPT the braces, manually test the yard rotation over the full range of rotation. Be sure there is clearance and no hangups. Some fairly high tension to get to maximum rotation is OK as long as the servo is strong enough to handle it. Be sure foremast and mainmast braces will clear each other through all combinations of rotation. At this point, also adjust the length of the yard trusses to move the yard forward of the mast to allow more full yard rotation before hitting the shrouds (note that too far forward, the middle of the yard may jam on the stays in front of it). This manual rotation testing step is necessary before rigging and tuning the sliding servo and braces.
2. After Step 1 above is really the time to make the servo drums, because now you can get accurate measurements of required brace length and length of pull required. You can also "build-in" yard spiralling (each upper yard rotates sequentially a bit more than the yard below it) into the drum diameter calculations. Because of 3D geometry (braces are at both vertical and horizontal angles and pull though a complex arc), line stretch, hardware clearance, yard tilt, etc., calculating precise pull length is nearly impossible.
3. Build the drums in a way that allows modification of the inner drum diameters.
Syren fore topsl brace drum diameters were too small relative to the course yard. That is, the topsl yard rotated slightly less than the course at full rotation. Rather than make a whole new drum, I glued a 1/16" tall x 0.10" thick piece of strip styrene onto each of the two (stbd and port) topsl brace drum surfaces to increase their diameters. The topsl yard now rotates a bit more than the course yard - a really nice effect (and helpful when sailing). So when making drums, perhaps keep layer thickness such that a common size styrene strip can be fitted in the slot and used as a "filler" to add diameter to the inner drum surface. Or make the drums a sandwich structure that allows changing individual inner drums.
4. At this point, attach the braces to the drums and wind on more turns than the servo will rotate. I use 2.5 turns. The drum rotates about 1.75 turns maximum in each direction.
When rigging the braces, use a small block to jam the servo forward in the frame. Push the servo against the springs to the maximum desired point - I went very roughly about 90% of spring compression length. Attach the braces to the yards and adjust length to exactly square the yards. (With the servo jammed full forward, the yards should be squared). When attaching and adjusting, make thebraces very taught. They should all be equally tight, and tight enough that the sliding servo does not slide backward when the jamming block is removed.
5. Be sure spring tension is high enough to bring yards all the way around. When yards are squared, all the braces should be very taught and the servo should be compressing the springs almost to the maximum. When yards are fully braced over, the springs should be pushing the servo almost fully backwards in the slide frame. (The spring length and strength need to be chosen to get the above action. Took me 3 sets of springs and some spring stretching to get it right.).
The unpulled braces should just begin to show slack as the brace pulling force starts to increase when the yards hit obstructions at maximum rotation. Additional rotation of the servo will actually start to pull the servo forward against the springs again and slack will develop in the unpulled braces. This is too far. So program the Tx jsut to the point of very slight slack formation.
|Jan 03, 2013, 01:55 AM|
Not boring at all!
Wasn't a cartridge-load brought up a long time ago? I was hoping to try this when I get back to the guns and my thoughts on multi-gun firing. The 6 pounders may not have large enough diameter to do it, but for the carronades, I wanted to try some experimenting with pre-loaded flash paper cartridges.
Not sure it's the ultimate solution but seems like it would work just fine. Am I crazy?
|Jan 03, 2013, 09:03 AM|
Paper cartridges, pre-loaded brass tubes for load insertion, drop-in powder loaders, etc have been tried. Have gone back-and-forth on approaches.
I built a 1/12 scale carronade model and use flash paper carteidges in that. The bore is 0.5". Flash paper is pretty delicate. It works well to make these bigger dia. cartridges, but it's really fussy to make smaller 0.25" ones, though I've done that too. Flash paper is pretty delicate - rips easily, etc. Cartridge dia. needs to be less than barrel dia. because the cartridges bulge significantly.
I've tried cigarette paper, wrapping tissue and TP. All leave residual unburned paper and result in a high number of misfires (the new igniter design may cure that)
Loading is still a big area of opportunity - still thinking separate pre-loaded barrels that plug in/out would be best. Once any barrel is fired when aboard, it's probable that some water will then get in, and likely prevent a successful firing of the reload.
With your gun design, with brass barrel liners, you could make the liners as self-firing plug-ins. The resin barrel would have the female connector and wiring molded in (or installed after 3D construction). Anyway, concept is shown in the hijacked drawing attached.
I'm now thinking this is the way I may go now....
PS - would be probably be best to use K&S thick wall tubing rather than the thin-wall (0.014") for longevity.
Edit - added thoughts...
Plug assembly should be symetrical so specific barrel orientation on insertion is not necessary
Tool to pull barrel, using a "pull-hole", is necessary
Barrel will be black very quickly with firing - no need to blacken barrel for appearance
Igniter wire is permanent type - your one-use rocket igniters could also be used.
|Jan 04, 2013, 07:54 AM|
Dan, the spiral bracing used by the grain ships, like Pamir, was the opposite of what you are suggesting. Namely, the highest yards of grain ships were braced *less sharp* than the lowest yards. The highest yards were braced closer to the run position.
This is the theoretical way to do it, following the maxim "the wind is fairer aloft." That is, on a beat, the wind aloft is not as foul as the wind near the sea. This is due to friction slowing the wind at the sea surface. This friction, coupled with the movement of the hull, yields an apparent wind that spirals from foul to fairer as you go up, away from the sea surface.
Perfect alignment of the yard to get the sail to fill and generated maximum lift thus requires that you leave the yards at the top of the mast closer to square (perpendicular to the hull).
I don't know if one could measure the difference in boat speed for a model using theoretically correct spiral bracing. I do know the "fairer aloft rule" exists for models, though; just look at the twist of a Marconi rig mainsail leach if the boom vang is not snugged: the sail at the top of the mast is not aligned with the boom, yet the sail is not luffing at either the boom or the head. In real boats, letting the sail leach twist (by slacking the boom vang) is used for de-powering the main in strong winds. But really, it could just as easily be called "upping the drive of the sail to make the boat go faster" :-)
There may still be operational advantages for a model using "reverse spiral", like you are suggesting. For one thing, if the wind heads you, the top sails will start to luff before the bottom sails, giving you a heads-up that you need to let the boat fall off a bit. If you use correct spiral bracing, on the other hand, you could get simultaneous luffing for the whole mast, making it more likely that you'd get caught aback.
|Jan 04, 2013, 08:59 AM|
Ooops. Major mistake on my part - thanks for noting it. I am absolutely not a sailor - hope to get there with more learning and experience.
Now I do wonder which way is best for a model. A couple of years ago, I took wind readings with a good anemometer at 2, 4 and 6ft above water. At 2ft, there was almost no measurable wind, and much more at 4 and 6. I thought then that was the reason I would usually see luffing first in the upper sails, especially the fore topsail. And the way the braces were rigged, the course yard on both masts always rotated more than the upper yards. That was the major reason, so I thought, for the first luffing in the upper sails.
So, with the new servo setup, achieving more rotation in the upper yards seemed a good thing - wouldn't that minimize the early upper sail luffing?
|Jan 05, 2013, 09:58 AM|
Reloadable Carronade Barrel Concept
In Post #200, a drawing shows a first cut at this concept. This post drawing has updated details. I tried to use readily available hardware store parts - brass tubing, small copper rivets, plastic plugs (from rod or plastic bolts) to make the barrels.
The idea is to have the contact assembly a permanent part of the scale gun. The barrel assembly has a re-usable igniter (also easily replaceable if it burns out). Multiple sets of barrels are made. They are pre-loaded and can be quickly changed into a gun after the previous barrel has been fired.
The advantages over the current design are:
- An improved, full-barrel-length, fast acting igniter
- Can have as many extra re-loads as desired
- Wet barrels after firing no longer an issue. Every pre-load is dry.
- No flash paper necessary
- Barrels can be cleaned away from the scale guns and model.
- Igniter easily replaced. Just crimp into a copper rivet and push into base plug.
- Barrels can be very quickly, accurately reloaded with a BP auto-loader.
Hope the pics are self-explanatory. Plan to make a test assembly soon.
Autoloader pics from old ost also shown. Make to match size of barrels used.
Gary - this can be done to your guns. Just replace the current brass plug/igniter with a new plastic plug like this concept and make new barrel tubes. Call and we can discuss. For the 4V system we talked about, 0.012 nichrome would work
|Jan 06, 2013, 07:35 PM|
EZ reload carronade design
OK, built a test gun. Works great so far. All 18 guns will get the socket shown installed in the breech. The reloadable barrels just plug in and out. Will make a full set of extra barrels for very quick gun reloads.
|Jan 06, 2013, 10:20 PM|
Very clean. That makes for success. Can you do a short video of this? I would like to see how it looks when its working. A phone video would do if you have one.
|Jan 08, 2013, 02:58 PM|
Syren Gun Upgrade Modifications
This latest gun design is pretty uncomplicated to build starting with an intact resin barrel. But I had to jimmy the design to be able to use my current brass gun barrels and cast resin breech assemblies. More complicated, but same principle.
PDF has all dimensions and details if interested.
Again, this approach is specifically to mod my existing guns, not the simplest, most direct approach anyone else might use when starting with new barrels. That design is in Post #204.
Gary - some details here are applicable to modding you existing guns.
Didn't get your call yesterday. Call anytime...
|Jan 08, 2013, 03:34 PM|
Geat pdf. Many thanks for sharing your endless, creative ideas and solutions so clearly for the rest of us.
Now, about that broadside test video.
|Jan 09, 2013, 09:59 AM|
BP naval gun design
That PDF was for mod of Syren existing guns. Here's a PDF detailing what I think is the simplest and currently best approach to making guns with reloadable barrels.
After building 9 guns with this new approach, here are some observations:
- Make cutting jigs for the small contact pin tubing and cut with razor blade - fast and accurate way to make a lot of pins
- the socket plug holes and the barrel pin holes need to be carefully centered for alignment. A drilling jig and/or drill press should be used.
- the socket tube can be made longer than shown in the drawing, but you don't want it so long that the tubes jam under use conditions (slight dings, dirt, sand, water, corrosion)
- I'm making 40 barrels - 2 sets for 18 guns and 4 extras
- delrin (acetal) is better than polypropylene for the plugs. Polypropylene is sloppy to machine, delrin is excellent. PolyP takes higher temp, but I think delrin will be adequate. Needs to be seen with use. Another option is to cast the plugs in place with thinset mortar or grout, but don't know how to control plug size with that approach.
- crimp and/or glue the plugs pin and grommet ( both in the socket and the barrel) permanently and very securely. They don't need to be removed (even when replacing the igniter assembly) and you don't want them slipping during use. I used CA and crimping to set the plugs and pins.
- make sure the small hole for the loose end of the nichrome wire is well inside the end of the barrel, preferably just inside the point where the wad will be when the barrel is loaded.
- K&S brass tubing is sized for telescoping fit. The socket tube should be one size bigger than the barrel tube. That slip fit, combined with the slip fit of the contact pin tube into the socket grommet, will provide a good friction fit and electrical contact (since these things won't be perfectly concentric)
- lube the barrel rim and pins at contact points with an anti-corrosive grease. I've used a liquid called Bullfrog and also plain old white heat-sink grease (seems to really stop corrosion and is very water resistant)
- make extra barrels and spare/replacement igniters now. Past experience is that these components are "wear items". On tear down of Syren guns, the igniters still were all intact after many uses. But they do burn out at times.
- pre-test each assembled barrel to check for shorts and proper resistance. I get about 4ohms with the wire size I'm using. At nominal 4.8VDC, that should be about a 1.2A current flow, but I measure a surge current of 4+ amps on initial contact. Use high capacity, high C-value batts to handle numerous current draw peaks as guns cycle.
- I'm looking for thermal breakers to add to teh power circuit. With this design and 4-cells (nom 4.8V, max 6V), a gun stuck "on" does get very hot. It's not visible on ship, likely until too late.
That's it. Hope to have a vid this weekend, but weather is still too cold to take Syren (and me) outside.
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