stix Posted October 7, 2018 Posted October 7, 2018 Crimson. Forget about Kn values for now. Also forget about all the other calculated results above. I didn't bother to read it. I don't give a rats arse about those numbers. The numbers only really mean something when you have a successful motor. (which you don't). Otherwise we may as well be talking about the current density of popsicle sticks in the year 2018 compared to 1961. Some people might find that interesting, or even offensive, but I don't care. I mentioned earlier about starting small then going big. Perhaps that is best phrased as starting simple, then moving to more complicated. Try ONE single grain. When you master that, then move forward. You seem to have more than one issue: fuel, nozzle, bulkhead. Who the hell knows ....? Forget about the math for now, you just need to be a bit more systematic and rule out issues as you go along. If that sounds harsh, so be it. This is the second last time I'm going to bother to post in this thread
Crimson0087 Posted October 8, 2018 Author Posted October 8, 2018 Sorry Stix, I was actually wanting to know about that last post for educational purposes. I actually did have a successful motor tho and I believe that I solved my main problem. I believe my main problem was with inhibition of fuel. I wrapped the fuel extra thick in the paper and with 4 1.2 inch grains it was a success. Watch video. My delay charge however, was not a success. But I think I am going to keep trying to work the nozzle down before I worry about delay charges. Thanks again for all of your help. https://www.youtube.com/watch?v=6juF1QSZN64 1
stix Posted October 10, 2018 Posted October 10, 2018 Nah, don't be sorry Crimson - I guess I was a bit harsh. I was getting a bit sick of seeing numbers. For the record I get a Kn value of 218 for the data you posted above. So for all intents and purposes we have the same result. There must have been an error made to get 255. Your latest test looks pretty good. What is that device you have it mounted to?
Crimson0087 Posted October 16, 2018 Author Posted October 16, 2018 Stix I just had it mounted to a vice. Also I believe I finally have it down with a 7mm nozzle.
Crimson0087 Posted October 16, 2018 Author Posted October 16, 2018 Still need to work on delay grains though. I believe that the burn is getting around the delay grains somehow bc the BP burned and then it looks like the delay grain was still burning.....might try making the delay by casting it into the motor casing instead.
stix Posted October 17, 2018 Posted October 17, 2018 (edited) That last one looked pretty good - roughly what specs did you have with this motor? I gotta laugh - At first I thought in the background of the video was some special apparatus that you were using to mount the motor, only to realise it's a fold-up chair I don't know much about delay grains - a bit more difficult for bates grain sugar rockets than bp rockets I believe. The last sugar rocket I made was launched as a rocket rocket, not a pyrotechnic rocket. It had an electronic timer for the delay to deploy the recovery parachute. Sleek fins, body and nose-cone. It took off fantastic and soon disappeared into the sky. It was way too far gone to know if the parachute ever deployed. I'll never know if perhaps the math (delay time) was incorrect and instead of deploying at apogee, it was still going too fast and ripped the shreds out of the parachute. My brother and I spent a good hour trying to find where it may have landed, if indeed it had floated down intact. It was a sad day. In model rocketry, if you don't get it back (even in bit is acceptable) then it's an absolute failure. Sure did look good taking off though. Edited October 17, 2018 by stix
Crimson0087 Posted October 17, 2018 Author Posted October 17, 2018 I'm not sure how strong my motor was but the scale flashed 45lbs for a brief second. I guess it's important on how long it maintained that max pressure to actually figure how high it can go. Yeah I have a new idea for the delay to try this week. I'll let ya know how it goes....also my nozzle blew out. It still had the restriction from the washer but the divergent cone was gone instantly
Recommended Posts