1lb BP tooling

[MrCATO]

I just got a new set of tooling from woodys for 1lb BP core burner rockets.

 

There are two lines at the top of the big rammer and 3 lines total. I know one is the do not pass line and the one toward the bottom is the switch line. What is the other one?

Also I have the 6000lb ptf gauge. What indicated PSI on the gauge do I need to press the fuel to? 

[DavidF]

The third line is for nozzled BP rockets, for making the nozzle throat of 1/8" or so. 

'Traditionally', a pressure of 6500psi is used for BP rockets. On the P to F gauge, that's 2866 pounds. That's what folks use for nozzled and nozzleless BP rockets with dry propellant. I like to granulate my propellant with 2% wax, dissolved in naphtha to moisten.

IF somebody wanted to use a waxed tube and dampened (2-3% water, screened in and tempered) propellant, MUCH less force could be used. 2% would be good for nozzleless, 3% would be good for nozzled. The nozzle would be pressed dry, always. In this case, the propellant would not be granulated. This is not traditional and not popular. It's just the best way, in my opinion.

[MrCATO]

I seem to have more luck incorporating moisture (water) in the ramming process. I've also tried dissolving mineral oil in lacquer thinner and that seems to work as well, still using water with it. My torque wrench maxes out at 150ft lbs which seems to be just a hair shy of 2500psi on the gauge. Would this be adequate?

I made some changes to my 1 ton press because it was just adequate enough for the small motors I was doing before. I got a 25in breaker bar which I can get 2500psi at the gauge in my weak hand or 3000psi with my right hand. Anything beyond that requires significant force. I noticed the threaded rod legs I raised the press with were cracking/pulling through the bottom of the wooden base so I added large square washers/bearing plates and that seems to have fixed the problem. I made a mistake in estimating how high I needed to raise it so naturally it's too low and I have to do it again. Is PVC an okay material to use for this or is there something better?

[DavidF]

My memory isn't perfect, but I feel like we have been down this road before. Forgive me if I'm wrong. I don't know everything, but I think you are still confusing psi and p. The P to F gauge does not read in pounds per square inch. It reads in pounds. The pounds reading will represent different psi with different ID rockets. A 1 pound motor is 3/4" ID. That is .441 square inches. To press that rocket to 6500psi would be 2866 pounds on your gauge. That's well over the capacity of your press. You'll strip the teeth off of the spline by using a breaker or cheater bar.

If you wanted to press a 4 oz. rocket (1/2" ID) to the same 6500psi, you would only need 1275 pounds on the gauge. The surface area of the 4 oz. motor ID is only .196 square inches.

You CAN press 1 pound BP rockets on a 1 ton arbor press, although most pyros would say you can't- because they have no experience using water (or enough water). They do things 'the way we've always done it'. If you wanted to do this, you would use 2 1/2% water in 75-15-10 nozzleless propellant (no binder, potassium nitrate is the binder). You would temper the mix, preferably overnight after a couple of screenings- in a sealed container of course. You would set your torque wrench to 95 foot pounds. Check the gauge in your press. A SLOW pull should get you a reading of 1500 pounds. This will consolidate the propellant (75-15-10 only) to 3400 pounds per square inch. This is more than enough, and works within the capacity of your press. This will compact your propellant grain to 1.65 g/cc. It will NOT work with dry propellant. The tube should be waxed.

I believe you are pressing too hard, and that following the above will help you, without having to re-modify your press. 

EDIT: My apologies. It was someone else that had a very similar problem, which I attributed to confusing p with psi. 

Edited February 26 by DavidF
Correction

[Carbon796]

It looks like you have plenty of length left. On your all-thread. To increase the working throat height. 

You don't need the pvc tube really at all. It's just there to clean up/make the press nicer to use. It's really just cosmetic. You should not be relying on it for any of the structure.

You should have nuts/washers below the base of the arbor press and above it. Like wise for the platen (which it looks like you do ). It looks like you're using the pvc tube for stand-offs. I would bet the press will feel nicer to use, once it's bolted solid.

Edited February 27 by Carbon796

[MrCATO]

I just raised it. I'm still unclear about the lines. Is that line immediately below the do not pass line telling you you're about to hit the nozzle geometry? 2 tsps of nozzle was probably too much? 

Something else I didn't think of until now. My old smaller set of tooling had a non removable spindle so I just twisted the motor by hand to remove it from the spindle. The bottom of this spindle seems to interface inside the base. I don't want to run the risk of shearing it. Do I need to purchase the spindle puller as well or can I just twist this off?

[DavidF]

If the top line comes flush with the top of the tube, you are as far as you should go, before you bottom out the rammer. If you are pressing a nozzle, you press to the bottom line, and then you know that your nozzle has enough 'throat'. The throat is the area between the convergent and divergent angles where the nozzle aperture is at its smallest. It's the 'bore' of the nozzle, so to speak. Perhaps somebody else can word it better than I can. The bottom line should be completely showing when you are done pressing the nozzle. To be on the safe side, it should be completely showing when you are done pressing the first increment of a nozzleless rocket too. To make a proper nozzle with your small press for a 1 pound rocket, it's probably best to press the nozzle in two increments, first to the top line, then to the bottom line- to get the best compaction. Also, when I mentioned 75-15-10 earlier for nozzleless rockets, I meant ball-milled powder. A 1 ton arbor press will not be likely to make a good rocket with dry propellant being pressed.

You should take the rammer out of that tube and place it on the spindle. Then stand the tube beside it, and see where the lines are. Those lines are for 7 1/2" tubes. If you were to cut a tube too short and go by the lines when pressing, you would bottom out your rammer. Always be sure to have the right length tubes! 

Ned Gorski has videos on YouTube that would be very helpful for a newer rocket maker.

 

[MrCATO]

I noticed quite a few compression wrinkles despite using the support. Put a dummy heading on it. It went up with the utmost authority but didn't make it far before blowing the bulkhead out the top and launching the dummy heading.

75/15/10 ERC 100# screen granulated with +1% dextrin (I don't like granules turning into dust just from handling). I redampened before ramming at 2500 indicated on the gauge. 

I don't recall the delay thickness but it was weingart candle delay. I had plenty of empty space in the end of the tube. Bulkhead may have been thin. I used kitty litter for both noz and bulkhead (solid cap).

I watched probably all of ned gorskis rocket videos, that's where I got the idea for the press. How do I go about waxing the tube? 

[DavidF]

Some tips in case you don't know:

Smaller increments can help with the wrinkles. I use 3 increments per drift, and some would say my increments are too big. That's 3 increments above the spindle tip. 

The tube support should be snug on the tube. A really dry tube might be shrunk a little. Moistening the outside with a sponge prior to pressing might be helpful. Some folks line the support with thin tape to make a better fit on a loose tube.

I use a shotgun swab and super hot wax (almost smoking hot), and swab the inside of the tube as I hold it over the container of hot wax. Somebody recently suggested swabbing with Turtle Wax and letting it dry. Easy enough to try. There's lots of posts about waxing tubes here, IIRC. The newest way I've seen is 'frying' the whole tube in a pan of hot wax. That's not my favorite method.

Looks like you did the same thing I did my first few rockets- using too hot a propellant for a nozzled rocket. They call them black powder rockets. Well, the powder is black and they are rockets. Anyway- common advice is to just leave the nozzle out and try again with the same powder. A nozzled BP rocket would work better with commercial airfloat charcoal, fine powdered Potassium nitrate, and sulfur, screen-mixed. Granulated, if desired. 70-20-10 would be a good place to start. This will give a decent tail.

When dampening the powder, leaving it in a sealed container overnight and maybe screening it right before use would be better than using it right after dampening.

Using dampened non-granulated powder is best, IMO. I make sure to use a steep funnel so I don't have to tap tap tap it every increment. That gets old real fast.

Most rocket makers avoid using dextrin.

That rocket was way fast for a nozzled BP rocket!

[MrCATO]

I just made another one before reading your reply  The nozzle is smaller and I used a tad more water. It didn't seem wet but I noticed the pressure was going down slowly so I had to slowly pull harder when I got to where I wanted. The shrinkage in the tube was also somewhat significant. I'll definetely have to try your method with tube waxing. I pressed a bigger delay and bulkhead. If this fails I'll leave out the nozzle for my third attempt as you suggest. I have a decent bit of fuel left in this batch. As for the increments I'm doing 1 tsp which seems to be about ~1/4" on the rammer.

 

Edited February 28 by MrCATO

[MrCATO]

I waxed a tube with a block of parafrin and a 12 gauge bore mop I already had. In the meantime I launched the second. It went up without blowing up but it more or less turned the opposite direction shortly after going up. It landed about a hundred yards behind me. It's been quite windy the past few days, may or may not have a role.

I used two of the 1/4" sticks I had leftover. May have not been enough to stabilize the heavy dummy headings. I wasn't able to recover the rocket so I have no idea if the nozzle stayed in tact.

[DavidF]

I didn't notice any compression wrinkles on the tube. Did you get the weight on it? I find with a 1 pound nozzleless I can easily lift a 4" ball, even a 4" cylinder. For a nozzled variety (using slower charcoal and formula) I'd only put up to a 3" cylinder on it. I use 2 sticks as well, but I put them on opposite sides of the motor and tape them together in a couple of places on the bottom. Then I launch it out of a larger diameter tube so the sticks sit on the ground. They fly very true now.

I don't recall you saying if your 75-15-10 was ballmilled or not? The ERC passed 100 mesh, is that it? One thing I find is that most rocket formulas don't mention that the potassium nitrate has to be fine powder, not greenhouse grade straight out of the bag.

[MrCATO]

I screened the comp several times through a 100 mesh screen, no milling involved. The ERC itself was milled though prior to incorporating it in the mix. Probably a bit much for rocket propellent but I have this screen and another that's way too small to use. The nitrate was granulated when I received it but I milled it prior.

My third and current rocket (the waxed tube) was pressed without a nozzle. Zero compression wrinkles and it feels very nice and solid in the hand. I drilled into the bulkhead to make a passfire then added some blackmatch. I slipped a small header tube over it and put 1g of live powder in it. Then I just added some dead weight to the outside. I want to see what my delay is doing since this is the last of my sticks. Given how hot this fuel is nozzless may be the way to go with it like you say.

Do I need to raise force as I go up the spindle since it's tapered? I've heard people saying this before, I don't know if it's needed or not.

[DavidF]

Folks generally agree that adding force as you go up is not necessary. A few have bothered with it and saw no real difference. I'm assuming your powder was damp when you pressed? Waxing the tube allows more latitude when changing propellants/fuels with less worry of CATO. You could take your existing powder, add 15% of commercial airfloat or 40-80 mesh charcoal (if you have it), ALSO add a nozzle, and have a nicer tail. Just a suggestion. I found that making a few rockets with tests in between taught me more about rockets than reading a sea of information. Looking forward to the result of this one. I find that the bottom of the propellant grain is very hard to mark with a thumbnail when it's pressed damp. It's shiny when first pressed, and turns dull pretty soon after pressing. 

EDITED to add: The farther you stick the J-hooked visco up the core, the faster it takes off. An inch up inside is good.

Edited March 2 by DavidF
Additional content

[MrCATO]

I never press dry, I've had issues in the past with consolidation when water wasn't involved. Seemed to be more of an issue with my last set of tooling. I'm certainly going to continue using the wax. I've got some commercial airfloat on hand. Might have to try it.

I've noticed a difference with the fuse in the motor before. Does it matter if you cover the fuse so it doesn't light the motor at the open end?

Third times the charm btw, delay is way off though.

[DavidF]

Delay might have been a couple seconds too long, lol. When I mentioned 3 increments above the spindle, I was thinking of my delay, which is the same propellant but with a bit of Ti or FeTi or charcoal in it. My delay is my bulkhead, and I lay the match for the shell onto it. 

For transport, I put a piece of masking tape or furnace tape over the end of the motor. When it's time to light it, I just poke a hole through the tape and shove the bent visco in. I don't know what you mean about covering the fuse. You mean like a quickmatch tube going up the core so it lights the core at the top? Some folks do it with slow rockets but I have never needed to do it on mine. Ned did some tests with fuse placement, IIRC.

Doing what I mentioned with the sticks will get rid of the cork-screwing at the end of the thrust, if you care to try it sometime. 

[MrCATO]

Gotcha. I've had issues in the past with the tops blowing through I'm guessing because I didn't have sufficient covering above the core portion. I suppose a thick bulkhead won't be an issue as long as the spollette is timed correctly.

I've got a bunch of spollette tubes and tooling sitting around I'd like to make spiked reports with. I've made these reports in the past but the motors I was using them on were inadequate to properly lift them. How would I properly interface one of these with a rocket like this? My pasting is sloppy so it's hard to cleanly glue/mount these.

[DavidF]

Hmm. Those won't suit the way I do it. Instead of a spolette, I use a few strands of match in the spolette tube, taped back onto it on the inside of the shell and with the other ends of match touching my delay/bulkhead. I wouldn't want to advise on something I don't do myself. I'm sure (I hope) somebody else will have a workaround for those. How much do they weigh?

[MrCATO]

These are old pictures, I no longer have these but they had a quarter pound of powder in them so they were pretty heavy. 

[DavidF]

In that case, here's what I do. I glue the matched spolette tube into the shell casing, with some of it sticking out. I use wood glue. When it's dry and the shell is loaded, I wood glue the poplar spacer onto it. Then I hot glue that into the top of the motor so the match touches the delay, trimming the match as necessary. Then I'll glue the outside where the shell meets the motor, let it set and attach the sticks. I make sure the hot glue gun is unplugged around pyro stuff.

[Carbon796]

Rocket headings don't need to be paste wrapped. Since they are not subjected to pressurized lift gases from a mortar launch. If that helps at all, on your future reports.

Edited March 4 by Carbon796

[MrCATO]

11 hours ago, Carbon796 said:

Rocket headings don't need to be paste wrapped. Since they are not subjected to pressurized lift gases from a mortar launch. If that helps at all, on your future reports.

The idea was to clean up the shell (bottom) where the motor mounts so I can have a solid joint between them but naturally it didn't work well with the bunched up paper and string. I think David has a good idea about using a poplar spacer thats the ID of the motor with its center fitting around the spollette tube. That's great if I don't have to do it, make it easier on myself lol.

[Carbon796]

That's my mistake. I assumed you were talking about the pasted crown on the spolette end. For a flatter/smoother bottomed shell. You'll want to use the offset spiking method ( if you're not ). And from the pics of the pasting. The crowns looks like they are a combination of pleated/folded. And some of them twisted.

Not to criticize, but, the paper doesn't look like it was broken in well enough. And not enough paste was used. Or it was too thin. This will help on both ends to get the paper to lay down flatter and smoother. 

Typically the paper over the ends will be torn in to strips, and laid down one by one in a spiral fashion. ( Not folded/pleated. That is just for the inner rolled case. ) this will give you a smoother finish on the bottom also. If you are similarly folding/pleating the bottom. The twisted method around the spolette is common with smaller inserts. But, the overhang looks like it was too short to properly form them. If the spolette OD is close to your rocket ID you could also paste a band wrap of 70# kraft around the spolette. To bring it up to size. Or an appropriate thickness of tube slit down its length. 

Edited Tuesday at 07:18 PM by Carbon796

[MrCATO]

Yeah I gotta work on the pasting. I made another batch of nozzleless BP without the dextrin this time and put quite a bit of water in it, had to let it dry it for a bit. Seems to be pretty powerful in a burn test but I haven't actually tested it in a motor yet. I just pressed a nozzleless motor with it with 3 delay increments (3 tsp) of delay with no bulkhead. The dowel idea didn't seem to pan out because I can't realiably drill out the center so I found these nylon spacers instead. Is it safe to use these instead around the spollette? Midwest Fastener® 1/2" ID x 3/4" OD x 3/8" Nylon Spacer - 15 Count at Menards®

[DavidF]

I can't comment on what 'quite a bit' of water will do. I weigh a spray bottle and spritz it into the powder, so I get exactly the 2-3% water that I want. The 3% is only for nozzled BP motors, for me. A couple pyros tried using too much water and too much pressure (6500psi?) and broke bolts on the tube support they used. Water was blamed

I would just use wraps of paper or tape like was mentioned before I bought those. They need a wrap or two of tape for a friction fit anyway. My spolette tubes are only 3/8" OD, so it's easier to drill (near) the middle. It's not that critical. I found out once by experience what forcing an over-sized spacer into the end of the motor would do- CATO!