How to roll pyro-tubes

[dagabu]

I have been using a drying chamber fed from a ceramic space heater, about 95c, 200c is WAY to hot for me, that is only 40c from auto ignition!

 

Lots of air across them but I find the same thing internally, the interior is the last to dry out.

 

As far as voids and bubbles go, the only time I see that is when the dilution rate is too high with white glue, not enough solids or when I roll the snot out of the tube! I use e board to tighten the tube, if I go slow with little pressure, the sheets tightens up nicely. If I get impatient, I get wrinkles and voids after drying.

 

I also roll up 16 tubes at a time, I have a "rack" that separates the tubes and it will hold 16 of them at once. By the time I roll another 16, the single sheet I rolled up on the previous batch is ready to get the second sheet rolled up.

 

I do three batches in one day or 48 tubes. Yes, it does take a while but so what? I live in Minnesota, what else do we have to do in the polar vortex?

Edited December 6, 2018 by dagabu

[Mixer]

I only tried the 200c for the initial 2 minutes then I drop them back to 50c for a period - then I let them dry off at room tamp.

 

I think the main reason things work well for me is that when I double up my initial layers i work them hard with a flexible spatula to squeeze out every bit of excess glue between the layers and both sides before drying, thus avoiding any voids or wrinkles. Also I pull very tight with the roll up.

Edited December 6, 2018 by Mixer

[Col]

lol, nothing like working them hard with a spatula

[dagabu]

I don't have any excess glue while using the roller to dispense the glue, nothing off the end either but a thin line at the overlap, I am pretty happy with my work flow now but am still on the hunt for the 'perfect' adhesive!

 

Because I have so much of this paper, I am looking into making a simple machine to drive the casing former against two conveyor rollers. The strips are only 22cm wide and 92cm long so alignment is the single most important thing I will have to perfect.

[Col]

Should be easy enough as the rollers will only need to be 250mm, 300mm at most. Wouldnt take you long to knock some up on the lathe. When your rolling the first turn of the tube, do you fold the paper back on itself or just run it straight onto the mandrel?

[dagabu]

I have a 9x21 lathe but I only need to dress the ends of the former, I make 1 pound tubes so off the shelf 3/4" rough stock with a lite polish will come in at 0.755" or so depending on the material.

 

Great question, my experience says to never have any paper that is not sufficiently glued down solid. Fire will run between two sheets and CATO a rocket every time! This is also why spiral wound tubes are useless for good solid rockets, no matter how "hard" they are.

 

I mark a line across my rolling board that tells me where to start rolling the glue on the paper. Then I run the paper right into the mandrel (former) where there is glue on the paper waiting for the lead to come into it making for a 100% solidly glued tube.

 

I do really like the way the paper aligns when folding it back but I always get glue on the former or no glue on the paper, both cause big issues.

[Col]

i dont use the foldback method for the same reasons but figured if you normally did it that way it would make the design less of a challenge You shouldnt have any problem with alignment or tracking with a 220mm sheet width as long as it goes in straight

You could soon knock up some bespoke rollers on the lathe and make a smaller version of this one, 14 tonne chain drive is not essential

 

Edited December 7, 2018 by Col

[dagabu]

"As long as it goes straight" Famous last words....😂

[Col]

Ifs no different with hand rolling if you dont start with the paper level I use 475mm and 700mm calendered sheets upto 4ft long, 220mm is less unweildly and should be easier to position. I came up with an option that guarantees it will go on dead straight everytime but have to think of a way to test it without taking a saw to my machine

 

If you can find a ~40" chunk of ~64mm od pipe to calender the big sheets into 3-ply sheets, 201 mm wide x 2ft long.that would make it easier

Edited December 7, 2018 by Col

[dagabu]

Nope, the paper is 220 mm by 920 mm, not going to calendar it, single sheets only.

 

I am looking for an old laminator so I can try the calendar process but I just don't have the tooling to successfully do it right now.

[Col]

The thing with single sheets is it always the 2nd last sheet that decides to track off line

[dagabu]

Sadly, I have a meter tall stack of paper, 24" x 36", uncut, that I need to use up. It is 0.003" (0.0762 mm) thick and it takes 108" (274 cm) of it to make a tube with the NEPT standard wall thickness of 1/8" (3.175 mm). I am not going to be using anything but that and only in the cut dimensions of 8.5" (22 cm) wide and 36" (92 cm) long.

[Col]

A bit of side by side testing.is on the cards. I could only find a 60mm od x 1m former but it`ll do to make a 190mm.x 3ft long (3-ply) sheet to compare against the 3 strips 190mm x 3ft long. I`ll use a brush for the glue (slowest method possible) and roll both tubes by hand onto a 19.15mm od former. I`ll time roughly how long each tube takes and do some burst tests once dry.

 

Notched sheet (570mm x 3ft) for calendering and 3 strips (190mm x 3ft) for single sheet rolling.

[Mixer]

You guys do make it hard for yourselves! good luck!

[Col]

I think both methods are pretty quick and painless. Once the paper is cut its just a case of applying glue and rolling. The single notched sheet gets glue on 2 sections and then its rolled onto the 60mm forner (3 turns). After a few minutes its cut lengthwise, glued and rolled into a tube while its still "green".. its done. The 3 strips are glued and rolled one after another, no waiting time between strips. I cant see how it could be any quicker or easier

[dagabu]

I suppose so but it's an instinctual path to hunt and problem solve until the quarry is bagged.

 

I have an entire winter to gnash my teeth and knead my hands over tube rolling, to search for the best possible solution for me with the materials at my disposal.

 

My wood shop is stuffed to the ceiling with supplies and I can hardly open the door so no making machines or other hobbies can be worked on until we move.

 

Looks like it's all tubes all the time this winter!

 

You guys do make it hard for yourselves! good luck!

[Col]

The stuff i`m using for the test is pretty basic, a 40" x 24" piece of mdf, 1m x 60mm od tube, paint brush, glue and 12" of 19.15mm od solid ptfe rod.

Edited December 8, 2018 by Col

[dagabu]

What is the 60 mm tube for?

[Col]

The 60mm tube is a former which converts the big notched sheet (in the paper pic) into a 3-ply 3ft x 190mm single sheet with feathered ends, 60mm* Pi is 190mm ish per turn . The first turn is not glued, the 2nd and 3rd turns are glued. After rolling, its cut lengthwise at the paper`s start/end point (exactly 3 turns) and opened out. Note, the grain direction is shifted automatically. It goes onto the former in this direction: IIIIII and comes off in this direction: ===

Edited December 8, 2018 by Col

[dagabu]

I am missing something here, you calendar it up on the 60 mm tube then roll the calendared paper on the 19.15 mm rod?

[Col]

Yep, exactly that, roll a 3ft long 3-turn 60mm id tube using a 3ft x 570mm sheet of kraft. Cut it lengthwise along the line where the first turn starts and the last turn ends. Use the 3-ply sheet to roll the 3/4" tube. A metre of 2.5" od tube would`ve been a better fit (200mm per turn) for the 3ft x 2ft sheet but 60mm is all i had on hand.

 

Marking a line on the former makes aligning the sheet easy, attach it to the former with 2 small tabs of thin tape on the corners of the kraft sheet. Those points will become the ends of the final tube. Attaching the sheet to the former makes applying the glue easier, cos the paper is pinned down by the former and it has half of the 1st turn on it. You can roll the tube without worrying about aligning anything so there`s no delay or panic. The 3 x 2 sheet will take 15 seconds or less to roll onto the former.

Edited December 9, 2018 by Col

[dagabu]

I am very disappointed with the overall OD of my wallpaper paste tubes, I will be using the calendaring idea to roll one up that will hopefully fit in the support like the PVA rolled ones.

[dagabu]

Looks like my new confection of two adhesives is working fine to make tubes!

 

[dagabu]

Thanks to a good friend, I was able to get a fantastic deal on some virgin (or mostly so) bleached kraft paper in 36" X 24" sheets, white in color and about #40 (0.0040") thick.

I wanted a placeholder to record my progress and review where I need to go back to if I run astray. It's not a how-too as much as it is a record of my experiences collectively so please comment but the adhesive has been worked to ad nauseum and I like it right where it is now.

Also, no need to comment on the paper, it's a fixed quantity as is the adhesive. I am working through getting the paper to roll tight and make solid tubes with no gaps.

Come along and join me on this journey, maybe we will see your tubes fly this summer at PGI?

Lets start with the glue/s I am using for this project, this is a combination of two adhesives:

Amazonbasics Washable School Glue diluted with filtered water to a 60:40 ratio. I am doing this because the initial tack is too great and the viscosity is so high to roll out well so there was a lot of loss due to it being pushed out while rolling.

At the time of this writing, this glue was only available in a 2 gallon purchases and looks to have been discontinued. I found Elmer's to be insufficient and lacking. You may have to search for a good white glue that will dilute this far and still have good tack.

The other is PRO-880 clear wallpaper paste by Roman mixed with filtered water to a 50:50 ratio. This paste has the viscosity of Crisco! It has to be diluted to roll onto paper so that it spreads out.

At the time of this writing, this was purchased through Home Depot online for $11.99 a gallon. They carry several Roman wallpaper pastes, this one seems to work well.

Both of these adhesives are then mixed together in a 50/50 mix and agitated carefully so as to not foam the liquid. I find this to pour well like a good Egg Nog! It does not taste anything like it but with some nutmeg, it may improve some.

I then pour enough of the adhesive into a 4" mini roller pan to fill the well and roll in enough adhesive to saturate a 3/8" nap roller cover.

The paper is cut into strips 8" wide and 36" long. The grain of course runs across the short way making it very easy to roll up on the former.

I lay a single sheet out on my PTFE board, it has a clip at the top that has an aluminum flat bar with a 1" closed cell foam pad glued to it to hold the paper while still allowing me to pull it out of the clip without tearing it, even if the paper is wet.

Once the roller is mildly saturated, I simply draw the roller down the paper to a line pre-drawn on the rolling board signifying the glue line. The remaining paper remains dry so the former slides off easily.

The former in this case is a section of aluminum 9" long and 0.775" OD, it does have packing tape on it to help keep any stray glue from getting a good grip. It seems to work well and give me just enough over size to allow for shrinkage of the paper.

Once rolled up, the rolling board is used to tighten the tube and align all the fibers. This works so well that even with wrinkles, (as you see in the picture above) the rolling, pressure and tightening make the end result smooth and even.

This leaves me with ragged ends that need to be trimmed, this pile of 16 shows the paper up close as well as one tube that has wrinkles inside that I will have to watch closely.

Two more layers, a drying cycle between each layer, trim both ends and this will be the pile tomorrow (I subbed in tubes trimmed last night to show the difference).

This batch ended up at 1.010" OD, 0.076" ID and a wall thickness of 0.122". These dimensions change from tube to tube, lot to lot and end to end. I am very happy with this batch, the large rolling board (10" X 21") sure helps a lot in the endeavor. Waxing the board also helps keep the glue from pulling the paper off the tube when "back rolling" the board to loosen the tube up a bit so it will slide off the former.

Next Up: Spolettes

Edited January 3, 2019 by dagabu

[Col]

Hey Dag, happy new year!

Glad the 50/50 glue is working well for you. I discovered the wickes wallpaper paste will mix with my high solids glue to produce a 39.5% glue which is more useful than 19%. I figure your paper must be 4 thou (0.004") thick cos 0.04" (1mm) would be more like cardboard which is tough to roll Greaseproof / baking paper (0.02mm thick) is quite useful for increasing mandrel diameter by a fraction, paste the full sheet and stick a strip of the greasproof paper to the glue, it`ll hold while you roll but will come away as the tube dries. Looking forward to seeing your progress.