Mumbles Posted March 13, 2012 Posted March 13, 2012 Part of the issue may have been the mallet you used. I understand the desire to not damage your tooling, but something with a rubber head isn't going to compact nearly as well as something that isn't as compressible. You really do not want any bounce in the whole operation. Many people seem to be fans of rawhide and rawhide faced mallets. I've also used a rubber coated deadblow hammer with success. Just as important as a solid hammer is a solid ramming surface. I took a class where we were ramming rockets on essentially a large log. It was clearly bouncing on every strike perhaps due to the state of the ground. Just about every rocket in the class blew up that was made at that station. When they switched at the end to an anchored solid ramming base the problem went away.
dagabu Posted March 13, 2012 Posted March 13, 2012 I have a Delrin hammer that puts down solid blows with no bounce, you can also look for Nylon hammers, they work much the same way. Rawhide is good too but it was 2-3 times the price of a good plastic faced hammer. -dag
PyroAce Posted March 14, 2012 Author Posted March 14, 2012 I will take a look at a new hammer when I'm at the hardware store next.
dagabu Posted March 14, 2012 Posted March 14, 2012 I will take a look at a new hammer when I'm at the hardware store next. You will need to look on line or in a wood crafting store for the rawhide mallet, I had to make my Delrin hammer myself since they do not exist in the marketplace currently. -dag
oldguy Posted March 14, 2012 Posted March 14, 2012 (edited) Dead blow hammers are what I use for some comps. http://www.harborfreight.com/catalogsearch/result?q=dead+blow+hammer I use Acetal/Delrin rod bought on ebay.They have rod about any diameter you want. Edited March 14, 2012 by oldguy
dagabu Posted March 14, 2012 Posted March 14, 2012 Deadblows don't consolidate as well as solid hammers though. I saw a side by side demonstration with 3# rockets two years ago with a rawhide v.s. deadblow hammers and both of the dead blow rammed rockets CATO'd, both of the solid hammer rammed ones flew wonderfully. -dag
oldguy Posted March 14, 2012 Posted March 14, 2012 Well, thats a learning lesson.How does your delrin hammer do?I have a block of it, that I could cut to size & insert a handle.
dagabu Posted March 14, 2012 Posted March 14, 2012 Well, thats a learning lesson.How does your delrin hammer do?I have a block of it, that I could cut to size & insert a handle. I would rather have a nylon hammer (I have a 4oz nylon headed hammer but it's too small for anything above 1/2") but a 2.5" x 4" long round section of Delrin has enough heft to pound a #3 BP rocket due to its ability to "shock" the powder into compaction. -dag
WonderBoy Posted March 16, 2012 Posted March 16, 2012 Dag, Thank you for the graphics. They provided needed context to my statement, From my experience, and what I have observed, as long as the tube is still attached to the stick, it is pretty likely to become a lawn dart. As for rockets flying into the crowd, this is always a possibility and an area where risks must be minimized. In general, I don't shoot good BP rockets with a small header, I try to match the motor to the header. To me, this means to have the motor lift the shell to an optimal display height and no farther. Granted there are times when a motor is simply designed to fly to high altitudes, e.g., a LWS. But in this case, any header other than a salute seems silly to me, because the rocket will be considerably higher than optimal display height for say a color shell. Since the header is a salute, then it negates the lawn dart issue because the salute will destroy/deform the tube and separate it from the stick. But as with any rocket it still has the potential to 90 degree turn into the crowd, where separating tube from stick will make no difference since it is already firmly planted in the grandstands. Have you seen this article? Newsletter277.pdf (does that link work?) It is an interesting idea which could potentially be applied to our rockets. How I imagine it could be used, the main downside I see is the addition of a metal component (wouldn't really want to get hit with that when a rocket CATOs), but maybe an alternative could be found. Also, it won't "bust the tube", just separate it from the stick, so a tube will still be falling to the ground. Ace, As others have said, a more solid mallet may help avoid CATOs and blown out bulkheads. I personally have had good luck using simple deadblow mallets, like those linked by Oldguy. I use a 2 1/2lb mallet for 1lb (3/4") and a 4lb mallet for 3lb (1") BP rockets. One drawback is that the face can get pretty torn up, but at $8 each this isn't a huge deal. One time I had the face start bubbling up, like a blister, after the second rocket. So, I took it back and they exchanged it for a new one without giving me any hassle. The best mallet I have used is a split head hammer with a nylon face like this: Split head link Another variable to consider is increment size; you want each increment height to be around 1/2-2/3 of your tube ID. I used to have problems when I would get in a rush and use larger increments to save time, CATOs and blown bulkheads galore. WB
gregkdc1 Posted April 24, 2012 Posted April 24, 2012 Ok do you guys have any BP formulas that you really like for effect when making a rocket? When I was a kid I made some BP rockets with a recipe that I came up with and by accident one of the batches had a really nice long tail. I don't remember the exact recipe but when lighting them they looked almost like a willow star. The recipe I was using was a simple black powder formula were some of the charcoal was replaced with a stoichiometric amount of powdered sugar. I would ball mill the propellant, then make a wet paste out of it and let it dry before ramming the motors. Anyways I have been lurking around this site for a while and I'm getting the itch to make a few rockets and I want to know what my options are for a good effect. I plan on making the rockets with sugar instead of black powder, because of tooling restraints and they will be small around 2-4 oz size. Currently I have carbon black, 200 mesh spherical aluminum (along with citric or boric acid to correct the ph of the KNO3) or I can just make up some charcoal. Would the carbon black survive the combustion process in the rocket to be expelled as sparks? What do you think? I guess there is only one way to find out. After reading about willow stars and tiger tail rockets I have found out the getting the comp wet is necessary to making a good long lasting spark. I am curios to see what effect the addition of sugar has if any on the rocket? I think that the lower combustion temp of a sugar propellant may help more of the carbon escape as sparks; at least this is what I hope.
Blackthumb Posted May 3, 2012 Posted May 3, 2012 IMG_0380.MOV small 3" nozzled rocket w/BP header to gauge height. Mix is 10:1 BP/sawdust w/spher. Ti added
PyroAce Posted September 28, 2012 Author Posted September 28, 2012 Well after having a break from making rocket failures (even though I only attempted 2) I decided to have another go after taking on some advice from the APC forum members and I am happy to say that my 1lb rockets are now a success. So that other members don't make the same mistakes I did, here is what I did differently. When I made my first two rockets I would just get an unmeasured scoop of rocket fuel and dump it down the funnel into the rocket tube, Wolter Pyro tools recommend that the compacted fuel should rise in the tube the same height as the I.D. of the tube, so I would use a measured teaspoon scoop for each increment. Secondly, when I was ramming my first two rockets I did so on a bench, even though the bench is made from timber the ramming force of my mallet would not transfer all force into the tube but rather spread it out onto the bench, to fix this I just got a post which I sat on the concrete floor and rammed on top of that, I think this was the biggest factor in stopping my rockets from CATO, I also made sure I rammed the clay plug nice and hard as I also did the nozzle. Wolter pyro tools also state that for the nozzle you must add the full amount of clay (in my case 1 3/4 teaspoon) and ram as one unit with 6-10 blows of the mallet, do not layer the clay. Also note I used the extract same batch of fuel that I made for the original ones that failed so the error was definitely not the fuel or the fuel being too hot, it was the ramming procedure. And if anyone ever wanted a comparison between a nozzless and nozzle rocket I posted the 2 videos below, the first one is the nozzless the second one is the nozzle rocket as you can see you just can't compare the thrust generated by the nozzle rocket, you can hear my friend who is filming laugh because he didn't expect it to launch so hard and fast. http://www.youtube.com/watch?v=2eECesVN-aE http://www.youtube.com/watch?v=9_NAuPypU9o
Col Posted September 28, 2012 Posted September 28, 2012 The nozzled rocket seemed to have a slight speed advantage to me, but both were fairly swift
PyroAce Posted September 28, 2012 Author Posted September 28, 2012 The nozzle one had a quicker launch, the video is probably deceiving, in person you could witness the thrust generated.
dagabu Posted September 28, 2012 Posted September 28, 2012 The nozzle one had a quicker launch, the video is probably deceiving, in person you could witness the thrust generated. I think you would be interested to know that the nozzless rockets have way more thrust then you would think. They also make for great lifters due to the gentle lift and predictable height of apogee. I will see if I can get side by side curves for you all to see what the real numbers are for nozzled vs nozzleless rocket motors. Just a plug, we are weeks away from releasing the ACME Rocket Test Stand to the public, this will be the only all in one solution for real time, real life rocket motor testing and will come with a built in e-match ignition system, software tools to show you how high your rocket will go with a shell (really) and even the speed that you will achieve with the motor. -dag
Col Posted September 28, 2012 Posted September 28, 2012 It`ll be interesting to see some definitive test results. It might be fun to compare nozzleless curves for piped top fusing versus non piped too.
dagabu Posted September 28, 2012 Posted September 28, 2012 I agree, that is part of the long term plan, to do exhaustive testing on all configurations and ignition methods. -dag
PyroAce Posted September 29, 2012 Author Posted September 29, 2012 This could be the case, the nozzle one just appears to launch quicker, I wouldn't mind doing a similar comparison.
PyroAce Posted October 4, 2012 Author Posted October 4, 2012 Just a plug, we are weeks away from releasing the ACME Rocket Test Stand to the public, this will be the only all in one solution for real time, real life rocket motor testing and will come with a built in e-match ignition system, software tools to show you how high your rocket will go with a shell (really) and even the speed that you will achieve with the motor. -dag This rig seems to measure: http://www.youtube.com/watch?NR=1&v=KRYtPmmxb-0&feature=endscreen
Trippiej! Posted November 20, 2012 Posted November 20, 2012 Hello there, I'm kinda testing out some rockets since do not have any relevant experience lifting one with good results.This is my latest design and eventually i want to lift 4" headers or at least 350-400 grams of total payload. Click for the design and imaginable result. Although the lift was very poor, the delay seemed to be alright. Now the mix i've used is slightly different, it was an old batch containing <5% sgrs so i didn't moist the mix while processing.I think this is one main variable i want to take along in my next design, dampen the mix, but wait, there is more: - Lengthen the motor from 15cm to 17.5cm- Smaller the nozzle from 7.5mm to 6mm or 5mm- Changing the fuel to 75:15:10 I've seen some decent 75:15:10 25mm ID coreburners lifting a 5" header to respectable heights, they seem to be very agressive and tend to CATO very quickly. So I rather stick to the 60:30:10. I'm going to test out some new designs within a week or so and post my results later, but i'm also curious about the input you could give me.These are some of my new designs: Design 01Design 02Design 03 Greetings!
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