Nozzle vs Nozzleless

[NeighborJ]

I wonder then, so as not to remove material, if it's just as simple as using a nozzle forming rammer the entire way up the spindle. This will at least ensure that it won't have a strait line to crack along?

[dagabu]

That's a poor solution as well as the face is about 1/3 the tube ID and pushes out more than down. Best fix for the glassy surface is a rammer with just a few teeth and turn it in the tube to break the shine. Drawbacks? Friction...

[NeighborJ]

OK... the few teeth thing wins out. My next option was going to be a waffle pattern face on the rammer but I can see where this will lead. Stuck rammer pain to clean out. I'm just worried about friction and that twist motion.

[dagabu]

Waffle iron face = shiny, hard waffle face to overcome with the next increment...

[joeyz]

i assume this "crack grain" concern is more for whistle mix than bp rockets. wouldnt a more damp fuel avoid this from happening? i would think that after compressing a rocket, the moisture in fuel would travel between the press marks creating a better bond/link. what about less fuel more press repitions or vice versa?

[NeighborJ]

Yeah, and these are just the ideas that have made it thru the filter. Trust me, you wouldn't want the job of sorting out the ideas running thru this head.

Damn it, now I've got to make a hollow and flat rammer for every size. I think I'll call them "west Virginian rammers" because they only have two teeth on their head. 🤐 sorry the filter must have been on break.

[joeyz]

soccer shoe with cleats lol

[OldMarine]

Steve LaDuke (and now Caleb) send fuel leveling tools with each tooling set to level the fuel at each addition. I don't see why these can't be used to scuff the face of the previous increment as well.

 

Edited August 4, 2016 by OldMarine

[Mumbles]

With regard to the fuel cracking or boundaries between increments, have any of you noticed this getting better or worse with particular phlegmatizer or fuels?

[NeighborJ]

With regard to the fuel cracking or boundaries between increments, have any of you noticed this getting better or worse with particular phlegmatizer or fuels?

[NeighborJ]

I haven't had any Catos but the cores I make are short with hot sali and I usually set them off the same day. I am doing a test with some 2oz. I have 2 motors sitting in the trunk of my car and I've been making 2 every day since monday. My intent was to set them off on Saturday to test short term storability and see if and when they start failing. Do you know what Caleb's fuel leveler is made from? It looks like plastic but I can't see him selling anything sub-par.

[dagabu]

Yes, plastic, certainly not sub-par for just a leveler.

[NeighborJ]

I think these toothed rammers are going to need a little more thought. I made one for the two oz and it plugged up 4 times before it started to take the glassy Finnish off. I only left two tits on the end. I think it will need a double helix flute cut in the sides, almost like a drill bit, in order to remove enough comp. And I will need to make it slightly thinner than a normal ram to reduce friction. I had to push hard and twist at the same time, this puts the thing in front of my chin. Not exactly a position I would want an accident to happen at. I'll try to figure out a safer way to hold the motor tomorrow. Mabe cut a square hole in a 6x6 to set the tube support in.

[Maserface]

With regard to the fuel cracking or boundaries between increments, have any of you noticed this getting better or worse with particular phlegmatizer or fuels?

I can't say for sure, because I haven't cut into enough types of rockets, but my whistle propellant with wax is very solidly combined at the increment boundaries. I had a tube split on me and I decided to extract the grain.

 

 

You can see where the tube split, and also the spiral pattern of the tube, but only faintly (if at all) the increment boundaries

[Mumbles]

I asked because I was curious if there was some sort of thixotropic property at play. Thixotropic materials thin or flow under stress or sheer like pressing, but return to a more solid state under static conditions. The fuels for whistle mixes are already sort of waxy or plastic on their own. The variety of additives may make or break certain properties as well, or at least modify them.

 

I've heard people say the same things about some clays, which are also known to be thixotropic.

[Maserface]

Well I have seen pictures of "extracted" black powder propellant grains, pressed dry, and the increment boundaries are very pronounced.

 

A good test would be to examine the impulse of end burner motors with variable "lubricants", you can see bumps in the impulse where the increments are.

 

Another thought I have is increment size, the larger relative increment, the bigger disparity between densities at the "top" and "bottom", this is explained in FAST.

[NeighborJ]

I have found an alternative solution for the prevention of the glassy built-up. Instead of reading it off it was simply to scuff up the polished rammer end with 120 grit sand paper. This caused that hardened layer to remain stuck to the rammer. I only cleaned out the spindle hole and left the stuck comp alone. I've not even seen a hint of glassyness since. I know it is not a perfectly flat pressing surface but it is no less flat then if I use the reaming rammer.

[dagabu]

Great idea! Yes, if you pull that top off the layer, I believe you end up with a very rough surface. Way to think on your feet!