ST1DinOH Posted January 9, 2009 Posted January 9, 2009 so i'm going to have some tooling made and the first step in the process is to decide what material i want to use. the main concern i have is cost, but the next thought i had was interaction/compatibility. if cost were not a factor i'd go ahead and have everything made of brass or stainless, but i'm not a rich man, so i've been looking into a cheaper alternative like plastic/plexiglass. the thought of using some sort of lexan/luan or an HDPE type plastic to make the tools sounds much more cost effective but i worry about the solubility between the plastics and the solvents used in stars. i'd hate to get a block of something machined only to find that a few uses later the material becomes pitted and/or begins to absorb any material. this can obviously cause a contamination problem. i've had problems with acrylic before when mixing it with alcohol. i won't go into the details, but basically my brand spankin new clear acrylic "tube" became foggy and started to crack after one cleaning. this is something i'd like to avoid. so is there a perfect material to use for pyro tooling if one was trying to get under the cost of metal alternatives? anyone have any ideas or is it dependant on what i am using it for. i'm not thinking of using any high amounts of PSI here, such as with a comet press, nothing more than a human can exert without mechanical advantages.
tentacles Posted January 9, 2009 Posted January 9, 2009 (edited) Delrin is your best best if you can afford it. Nylon is a decent second choice, neither can be glued very well. What kind of tooling did you want to make? You could likely make a star plate out of something like HDPE. None of those 3 materials would be affected by any pyro solvents. Nylon *might* absorb a little water, but it would be negligible unless you store it in water or something crazy like that. Edited January 9, 2009 by tentacles
ST1DinOH Posted January 9, 2009 Author Posted January 9, 2009 thanks for the replies... basically just making a bunch of different pumps, rammers, and forms. nothing unique or new. so whats cheapest out of all the workable options? also, whats sturdiest. hdpe?
Pretty green flame Posted January 9, 2009 Posted January 9, 2009 My favorites when metal working are Brass and Aluminium (Non sprak bonus).
Brakkie Posted January 9, 2009 Posted January 9, 2009 I've had experience with Delrin and I'm not a big fan of it. Unless you're using large tools the parts will have a tendency to twist a little bit. They're far more flexible than metals although Delrin is pretty rigid. It kinda depends what kinda tooling you want, if you're making tools that will use Delrin for ramming you better get something that's thicker than 25mm or else it will flex which can result in cracked stars, motors, etc.
Bonny Posted January 9, 2009 Posted January 9, 2009 For low cost, you can use plastic pipe (HDPE,PVC,ABS) for the sleeve and the rammers can be made from hardwood and then coated with polyurithane to increase life.
firetech Posted January 9, 2009 Posted January 9, 2009 I bought a starplate from skylighter and although the actual price of the plate does not match that listed it is well worth the price. The plate provides efficiency, consistency and convenience. They are very durable and easy to use so i suggest ordering one. That would be one of the only things i would purchase from there in terms of tools because they are rediculously overpriced. www.onlinemetals.com could provide some metals for rocket tooling. For comet pumps i use pvc with a pounded aluminum foil plug. The plug is pounded in the pipe and the pipe is filled with composition and then a dowel is inserted in the non-comp end and the comp is pounded then ejected.
Swede Posted January 9, 2009 Posted January 9, 2009 Materials... one of my favorite topics! You've already found out that plexiglass is too brittle. Of the other plastics: Delrin - good stuff, overall high on the list. Nylon - Sleeter recommends nylon above delrin when it comes to ramming rockets, but sucks in the chemical resistance category. PVC/CPVC - often overlooked. Can be bought as standard pipe or solid round bar. Excellent machineability, good hardness, decent chemical resistance. Inexpensive. PET - coke bottle plastic. It too can be bought as round bar and sheet, and is opaque white. It is one of my new favorites. Awesome machineability, excellent chemical resistance. Stronger/harder than delrin PTFE/glass-filled PTFE - the ultimate in chemical resistance, but it's quite soft compared to the other plastics. It really does come down to what tool you want to make. I'd go with metal when I can. You're going to invest far more in labor and time than you are materials. Of the aluminums, 7075 is the strongest and machines like a dream. 2024 is next, then 6061. Bronze is an excellent choice for just about any pyro duty, followed by brass. Stainless steel is perhaps the best pyro tool material but is unpleasant in general to machine or shape. There it is, tradeoffs all. There's no perfect material. Look into the PET for rammers, it's good stuff. ALL of this (round, sheet, bar) can be purchased online at mscdirect.com or perhaps Grainger. MSC is my favorite. If you are in the U.S., order in the morning, it's at your door the NEXT DAY and you are paying UPS ground prices. I'm not sure how they do it.
qwezxc12 Posted January 9, 2009 Posted January 9, 2009 I use schedule10 SS pipe and UHMW Polyethylene rammer for my 3" comet pump. Works great in a 6-ton press and the PE drills nicely (for cored comets). Details here:Comet thread - post#1Comet thread - post#2
ST1DinOH Posted January 10, 2009 Author Posted January 10, 2009 damn you guys are good. so if you had to find a balance between cost, and rigidity what would be the best plastic to use? i'm looking for something that can be milled. and for this particular application i think something with that "waxy" feel to it like HDPE would be perfect. is there something like that out there but it's called something else? like those white cutting boards everyone seems to have, is that HDPE?
Sambo Posted January 10, 2009 Posted January 10, 2009 I'm a fan of delrin, i have several comet pumps that use a delrin rammer and brass sleeve. The pump on the pic below has interchangeable heads that screw onto the top of the rammer, one is for crosettes and one for cavity comets. I also use it for the ends of rocket rammers, i use a stainless tube and press on the delrin former on the end; works perfectly.
tentacles Posted January 10, 2009 Posted January 10, 2009 Something that machines good? That would leave UHMW out - that's what most cutting boards are these days. HDPE mills okay if you can find the real stuff. Expect to have to trim off plenty of burrs and crap though, unless you mill it with a CNC router (high speed). I've heard delrin machines nicely, and I've seen evidence of that for sure, and as Swede said, PET is great - sheet may be expensive though. Try www.usplastics.com
crazyboy25 Posted January 10, 2009 Posted January 10, 2009 How would one machine the head of a crossette pump anyway? Everything else seems possible on a lathe but wouldn't a lathe only be able to make rounded heads?
Mumbles Posted January 10, 2009 Posted January 10, 2009 With a milling machine. Interestingly enough, I've just been theorizing about making my own crossettes just before reading this. Essentially I want to make a rig that can pump out a couple at a time. If they work well, and are easy to make, I'd make one of those poor-man presses on passfire and make a rammer for each one so I could make them in bulk. I have no machining skill or tool availability outside of a drill press and cheap tools. I'd stick with round hole, or a square hole with slightly tapered sides. One can buy delrin square rod. That would be easy enough to sand down slightly. From there, I would put a pin through the whole thing. This would form both the pin on the end, and a way to connect to the rammer. For me the rammer itself would probably be made from some sort of plastic, or wood. I would probably use friction fit to connect everything. Lloyd Sponenburgh gave this info on passfire a month or so ago:A 'basic' crossette design has a cavity width approximately 33% of the crossette's o.d. The cavity pin should be about 5/8 of the crossette's length, leaving roughly 2-3 seconds of solid comp below the pin. If it possesses one, the ''shot pin'' (that little 'tit' that extends past the cavity pin) should be very short; say, 10% of the length of the cavity pin, and less than 1/4 of its diameter. I helped a friend with some 6mm crossette tooling quite a number of years back. He was making film-canister shells with rings of crossettes! (and they worked) LLoyd Given this info, and availability of the square rod, I'd use 1/4" square for 3/4" and 1" tooling, and 3/8" square for 1 1/4", probably 1/2" for 1 1/2" and 1 3/4", and maybe go to 3/4" for 2.5" tooling. It's easier to tune burst to the cavity size than worry about exacts. http://www.usplastic.com/catalog/product.a...roduct_id=17278
psyco_1322 Posted January 10, 2009 Posted January 10, 2009 I would think at the price of plastics, you would just buy Al and be done with it. I bought a 6 foot long 1/2" piece of Al round stock for $5. It does get more costly if you start buying things 1" and over, since there is a lot more metal there. For forms, as in for shells, just use wood. Dan Thames had made some tooling from that grey PVC, or I think thats what it was. He had me made a few rockets on it. NOT FUN !!! That stuff bounces and just sends a crazy shock through your hands. So plastics for ramming = bad idea IMO.
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