Does anybody know how to design sprockets? I would like to laser-cut some sprockets for turret rotation out of 1/16" acrylic, but I don't know how to draw them in CAD or vector format.
first off, get yourself a copy of the machinery's handbook.... you also might check this out http://www.gearseds.com/files/design_draw_sprocket_5.pdf you would want to verify it is correct, however, as I have not done that.
You can find tools to design them for You. Emachineshop has a wizard to help www.emachineshop.com/machine-shop/G...ge507.html Note : emachineshop is a proprietary design tool, and You would probably have to get the parts made through www.emachineshop.com. I just mentioned it to demonstrate that there are tools available. Eventually take a google tour, using search words "cad sprocket tool" could be an option. best regards Markus Andersen
Hey Carl, I'm really liking the idea of a sleeve type bearing, but I'm wondering how you held everything together. I'm assuming the flange on the bearing is held captive between the counterbore you machined and another laser cut acrylic part on top of it, but how do you keep it in the base, and where does it rotate..... in the acrylic plate it is counterbored into?? I have been considering something like this myself, since it seems to have numerous advantages, such as size and weight savings, simplicity, and cost effectiveness. Any insight you could provide would be very helpful. also, has this cannon been combat tested? Just wondering how the durability is as well. Thanks!!!
Hi Cannonman, the answers to your questions are 1) yes, it rotates in the acrylic plates 2) I have a pair of #4-40 setscrews going in the sides of the cannon vase, that grab the flanged bearing on either side. This prevents it from falling apart or blowing up or otherwise failing spectacularly. 3) no it has not been combat-tested yet, so I don't know how well it will handle that kind of abuse. I have run an endurance test, in which I fired an entire magazine (118 rounds, 59 volleys) without a problem. Other insight: the counterbore where the flange goes is the most important part of the entire piece. Too small and it will be stiff or won't rotate, too big and it will wobble all over the place and be inaccurate. Also, the flange bearings I have used have a tiny little fillet between the cylinder and the flange, that's barely visible but can affect rotation performance. Make sure you check for this and either remove it or compensate for it in your counterbore.
Thanks Carl, as usual, your insight has been very helpful. I did have another question - How do you retain the barrel risers in the bottom of the magazine, and have you seen different methods to do this? I am at a little bit of a standstill on this portion of my design....... Thanks Again!!!!!
Doh!!!! My bad, I just re-read your build portion of your initial posts, and see that you used ruberized ca glue to hold these in..... how is that working, and have you tried that on other cannons you have made???? I'm wondering about durability.... Thanks again
The ship for which these cannons are destined is still under construction. It should be completed some time next year. The only durability/endurance test I have done so far was firing one complete magazine of ammunition using a 3.5oz CO2 bottle and a regulator set to 130PSI. My biggest concern was that the acylic would crack or even shatter after the first few shots, since every time you fire the balls in the ramp go slamming back from the breeches. I have seen more weakly constructed guns fail because of that effect, but they always fail quickly or never. Since these cannons haven't failed quickly, my money is on never.
Thanks for the input Kotori, and the idea on the rotation. I've made the manifolds, rotation "bushings", and magazines for my cannons from aluminum, and it seems like it is going to work awesome!! I still have a bunch more parts to make before I'll have test-able cannons, which may or may not work, but the rotation portion seems like it will trouble free.
ok this is an old thread but after looking it over i am very interested in possibly using this. I do have a few questions though: 1) most important did these end up working very well for you? 2) when you sent your diagram to the company did you include any specific measurements as to how big the holes needed to be? 3) how much would you estimate the total cost of your guns ended up being? 4) did you ever get them up and rotating?
1) I have not tried them in action yet, the ship they are in is still under construction. Something about joining the Navy slowing things down... 2) When I sent them the drawings, I sent a vector drawing that included a precise 1"x1" square for them to scale off of. They were close enough that the width of the laser beam compensated for any possible scaling issues. If I ever need something super-precise, I'd laser-cut a pilot hole then ream it out to the correct size myself. 3)I don't remember, it was much cheaper than normal because I already had cannon bases ready. 4)Yes. It did take a little extra work, though, but they do rotate just fine now. Funny how everyone likes to use ball bearings for turret rotation, but it's not necessary so long as you precisely machine your rotation surfaces.
Very interesting design -- I have a couple of questions: 1. Where are the setscrews in the breech? I see the setscrews in the cannon base which hold the flanged bushing fixed in the base, but I don't see the other setscrews you mentioned. 2. Did you ever sketch a design for a lasercut cannon base?
1) In the disassembled pictures, you can see four screw-holes around the perimeter and then two setscrews side-by-side. Those two setscrews go into the breech, and the four outer holes are for holding the cannon together. Notice how all the other layers have larger 1/4" holes that line up with those two setscrews. 2) No, I have not sketched out a design for a cannon base. Real life has intervened, so I probably will not, either.
I see, thanks -- what exactly do those breech set screws do? Lift the ball towards the riser to help them get blown into the barrel? They are centred under the risers?
The setscrews are what controls the single-shot functionality of the cannon. It adjusts the overlap of the loaded round with the next-in-line round. Insufficient overlap and it'll fire two weak shots. Too much overlap and it won't fire at all. Several years ago I posted an article explaining the exact operation, but I think it got lost during maintenance or something, it was a really really old thread.
Not everything deleted is lost: http://web.archive.org/web/20071024171234/http://www.rcnavalcombat.com/rcnavalcombat/forum/topic.asp?TOPIC_ID=181
I've written an OpenSCAD program to produce a design for this type of cannon. The design is parameterised by diameter, number of barrels, riser diameter and separation etc. It's here: https://bitbucket.org/tdavies/lasercut-cannons/src Note that the length of the ramps has to be tweaked manually at this point. I intend to allow export of a suitable 2D laser cutter dxf I'd be interested in any comments.
Very cool. I don't have the software to view that right now, where do I get it? For now, a few questions: would you be interested in further developing the magazine design, if I design a standardized cannon base suitable for up to 1/4" quads that can be mass-produced from a CNC machine shop? There is a lot of interest in Big Gun cannons, but a lot of people need different sizes and shapes of cannons. I can point out a few design issues I had to deal with, and suggest improvements for ease of assembly and improved performance.
