pyrokid Posted October 18, 2010 Posted October 18, 2010 Hey guys, I have been having the oddest problem when trying to make my rockets. I have a 1 lb. core burner set from Rich Wolter, and some NEPT tubes from hobby horse. I cut the tubes with a generic yellow miter box. It appears to give a nice straight cut. The problem is this: I will set the tube on the spindle, ram the nozzle, and a few increments of fuel. Then, when it is time to change rammers, the next rammer will grind the spindle enough to make me not want to ram it. The spindle is obviously off center. What am I doing wrong? The very first rocket I made worked beautifully.
NightHawkInLight Posted October 18, 2010 Posted October 18, 2010 Is it possible you bent the spindle when removing the first rocket from the base?
dagabu Posted October 18, 2010 Posted October 18, 2010 It may be the sleeve that is pushing it off from center. The tube in the support should sit square on the base when just sitting there. BTW- Offset holes in the fuel grain is one way to cheat the fuel bur to extend the burn and lower the thrust. It takes quite a bit of offset to get that to happen though.
Mumbles Posted October 18, 2010 Posted October 18, 2010 Have you tried one with one of the factory cut ends on the bottom vs. the miter box cut end? The factory cut ends should be good and square.
KruseMissile Posted October 18, 2010 Posted October 18, 2010 Have you tried one with one of the factory cut ends on the bottom vs. the miter box cut end? The factory cut ends should be good and square. Miter box's make square cuts and it's hard to mess them up.
mike_au Posted October 18, 2010 Posted October 18, 2010 Miter box's make square cuts and it's hard to mess them up. That depends on the quality of the box. I have a cheap plastic stanley thing. When I cut my tubes the results are good, but certainly not as square as the factory end.
Richtee Posted October 18, 2010 Posted October 18, 2010 Miter box's make square cuts and it's hard to mess them up.IF properly set up. And solid enough not to need re-setting after a few cuts. This would be the first thing I'd look into.
dagabu Posted October 18, 2010 Posted October 18, 2010 If the tube is square and the support is square, the spindle may be bent. Place the tapered end on the edge of a table and roll it slowly by hand, the base should no wobble. I have a 1# UT set that has 3° of tilt on the base from an over-ram.
pyrokid Posted October 26, 2010 Author Posted October 26, 2010 (edited) First off, thank you all for your informative answers, I couldn't have asked for better. Thank you mumbles, the factory cut end works perfectly. Fuel is drying as we speak. Looks like I need to buy a new miter box. Edited October 26, 2010 by pyrokid
pyrokid Posted October 28, 2010 Author Posted October 28, 2010 Okay, this just got more odd... After ramming the nozzle, I withdrew the first rammer. I slid the 3rd rammer (the last one with a hole) into the tube, and it fit all the way down to the no pass line. After 5 increments of fuel, the 3rd rammer would not fit in at all. The first and second ones still fit, but the second one ground on the spindle when I tried to insert it after 5 increments of fuel. What is the deal? I tried dagabu's suggestion to roll the spindle on a flat surface, and I didn't notice any abnormalities. This is killing me.
dagabu Posted October 28, 2010 Posted October 28, 2010 Hmmmm... When pressing the rocket, is there ANY movement side to side of the rammer in relation to the base? I didn't align my press once when I got it back from PGI two years ago and it shifted on me and did the same thing, it took a week to figure it out. The only other thing I have seen is a bent spindle, I have one of them sitting on my shelf of shame right now though I will be turning it down to a BP spindle and reuse it.
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