JMan Posted July 6, 2017 Share Posted July 6, 2017 I've found great help on here before and have been working on very successful and powerful rcandy rockets (with nozzles). But I've been trying to make some nozzleless rockets and simply can't get enough thrust no matter how long I make the core. I cast the rcandy directly into the tube (1in diameter 3/16 in core). No matter how long I make the core it just seems to have more weight and not lifting off (or extreamy low thrust to weight 1.1 or 1.2). My next idea is a wide core (I'm not sure it's real name but instead of a circle it'd be like sticking a ruler in the cores place) but I've had explosive results with that due to too much surface area but I'm going to try again. Any suggestions would help and are greatly appreciated. Link to comment Share on other sites More sharing options...
lloyd Posted July 6, 2017 Share Posted July 6, 2017 Since it's long been a standard practice with R-candy nozzled rockets, I would suspect that a 'burst diaphragm' might help getting the chamber pressure up in a nozzle-less version, also. LLoyd Link to comment Share on other sites More sharing options...
JMan Posted July 6, 2017 Author Share Posted July 6, 2017 So essientaly put layers of tape over the bottom? How might one make a "proper" diaphragm? Link to comment Share on other sites More sharing options...
lloyd Posted July 6, 2017 Share Posted July 6, 2017 (edited) I always used 1/32" Bakelite sheeting... sometimes doubling-up to 1/16", depending upon the motor. It's advantage is that it holds until its breaking pressure, then fragments easily, passing through the nozzle without obstructing it. With a nozzle-less design, it's only important that it blow away, not fragment, per-se. So I'd say any stiff plastic would work. Eh... maybe even an aluminum disk strongly affixed to the bottom end... but tape? Nah.... (Except, perhaps, for aluminum HVAC tape, which can stick securely, isn't 'rubbery', and can be layered to increase its bursting force.) Lloyd Edited July 6, 2017 by lloyd Link to comment Share on other sites More sharing options...
dagabu Posted July 7, 2017 Share Posted July 7, 2017 I always used 1/32" Bakelite sheeting... sometimes doubling-up to 1/16", depending upon the motor. It's advantage is that it holds until its breaking pressure, then fragments easily, passing through the nozzle without obstructing it. With a nozzle-less design, it's only important that it blow away, not fragment, per-se. So I'd say any stiff plastic would work. Eh... maybe even an aluminum disk strongly affixed to the bottom end... but tape? Nah.... (Except, perhaps, for aluminum HVAC tape, which can stick securely, isn't 'rubbery', and can be layered to increase its bursting force.) Lloyd I have had luck with wood disks. I have to say though that a nozzleless R-candy motor leaves much to be desired IMHO. Link to comment Share on other sites More sharing options...
JMan Posted July 8, 2017 Author Share Posted July 8, 2017 How would I secure it to the bottom of my rocket while keeping it airtight? Or does it simply act as a "temparory" nozzle Link to comment Share on other sites More sharing options...
dagabu Posted July 9, 2017 Share Posted July 9, 2017 I have epoxied them inside the tube, below the grain. The disk is drilled for the wires for an e-match and its also epoxied in so its moisture proof. Link to comment Share on other sites More sharing options...
JMan Posted July 10, 2017 Author Share Posted July 10, 2017 About how thick are you making yours less than a 64th an inch right? I'm thinking about just using coke cans as my burst diaphragm. Either the sides or bottom Link to comment Share on other sites More sharing options...
dagabu Posted July 10, 2017 Share Posted July 10, 2017 Wood? No, almost 1/8" thick. The pressure it takes to knock the disk out is pretty minimal, I haven't had a tube split on me yet. Link to comment Share on other sites More sharing options...
JMan Posted July 10, 2017 Author Share Posted July 10, 2017 Sorry I'm talking about aluminum dagabu but I'll be certain to try out wood next time I get the chance (I'm not home a lot of the summer) Link to comment Share on other sites More sharing options...
dagabu Posted July 11, 2017 Share Posted July 11, 2017 Sorry I'm talking about aluminum dagabu but I'll be certain to try out wood next time I get the chance (I'm not home a lot of the summer) An aluminum can, can be produced with a wall thickness of 0.097 mm – as thin as a human hair. Link to comment Share on other sites More sharing options...
mabuse00 Posted July 12, 2017 Share Posted July 12, 2017 I had the same problem in the past, using sorbitol fuel.Even when lit at the top, some rockets where just smokebombs on sticks. I've never tried plugs though. You might want to take a look at pirotex2005's channel at you tube, he's in the forum also.He has some examples of nozzleless KNSB rockets that seem to work astonishingly well. Link to comment Share on other sites More sharing options...
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