When using graphite for nozzles - keep in mind that it is a surprisingly good heat conductor.
Hans On 05/06/2014 02:39 PM, Steve Peterson wrote:
The Graphite Store (www.graphitestore.com). Right now, 2" rod, 48" long (medium extruded) is selling for $66.50. That much steel would be a lot more expensive. Unfortunately, I don't see any smaller diameters in the medium-grained; they do have smaller diameters in the fine-grained but it's more expensive--for instance 1" diameter by 24" long is $43.90. I would not recommend trying to machine away a 2" diameter chunk if all you need is 1" diameter--a vacuum helps control the dust, but it's still messy.I used 12L14 for years before I switched to graphite and I still make steel nozzles on occasion. I never saw any erosion with sugar propellant.If you do go with graphite you can make a "form tool" for the convergent and divergent sections which makes the turning go much quicker--just grind down a spade bit, it doesn't have to be that sharp to get the job done.--SteveOn 05/06/2014 03:59 AM, (Redacted sender monsieurboo@xxxxxxx for DMARC) wrote:Strangely enough, the mid-grade (medium-grained) graphite tends to do the job better than the high-end, fine-grained material. Less erosion, perhaps due to larger grains interlocking better and being ablated more slowly. And of course, less expensive.Graphite's definitely the way to go, but you don't want conductive, fine dust getting into any electronics (such as a benchtop mini-lathe) so try to capture the dust at its source.Cheers, Mark L. -----Original Message----- From: Hayk Azatyan <dmarc-noreply@xxxxxxxxxxxxx> To: sugarshot <sugarshot@xxxxxxxxxxxxx> Sent: Tue, May 6, 2014 5:53 am Subject: [SS2S-Main] Re: Material for Nozzle fabrication Thanks for your input Jeff. Where do you recommend I buy graphite from?On Monday, May 5, 2014 4:58 PM, Jeff Moore <tnetcenter@xxxxxxxxx <mailto:tnetcenter@xxxxxxxxx>> wrote: Graphite would probably be the most affordable of materials to use. We had a machinist in our local group at one point and he made a titanium nozzle as a proof of concept. That would more than likely be rather pricey for this project ( his was for a 54mm motor).Aluminum is a good material to practice on or do mockups with, but I suspect that it's melting point is way too low to be used as the actual nozzle. It might work as a carrier for a graphite or ceramic insert though.Jeff Moore Bend, OregonOn Mon, May 5, 2014 at 4:10 PM, Hayk Azatyan <dmarc-noreply@xxxxxxxxxxxxx <mailto:dmarc-noreply@xxxxxxxxxxxxx>> wrote:Hello all, Would you all happen to know where I can get my hands on some scrap circular steel bars for rocket nozzle fabrication?And if you have any suggestions on the material I should use please let me know. I have already started using the lathe, and currently I am machining a nozzle out of aluminum. Although I will not be using this particular nozzle for flight I figured I should practice making one out of some scrap metal that I found(in this case aluminium). I know that you guys make some of your nozzles out of graphite, but for now I am learning to machine metal nozzles just for educational purposes. Thank you guys! -Hayk Azatyan