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#16 bigtonyicu

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Posted 14 July 2008 - 06:22 AM

Hey guys,

I just built one of these lovely machines but I'm running into a slight problem, OK make that a big problem. They roll the most beautiful tube but I can't seem to get them off the darn mandrel. What am I doing wrong? They seem very damp, but I'm barely putting on any glue, I'm rolling with 40lbs Kraft and PVA glue.

I've tried lubricating the mandrel with Teflon dry film,... the mandrel is very slippery but the darn tube doesn't seem to agree. Am I tolling to tightly? (is there such a thing....

HELP

(incase it matters, I'm trying to roll Spolette tubes 3/8"x 18" (to be cut in 5 once dry))

Edited by bigtonyicu, 14 July 2008 - 06:24 AM.


#17 cooperman435

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Posted 14 July 2008 - 06:36 AM

first question that springs to mind is are you coating the first section of paper with glie Ie is it glued to the mandrel?

#18 phildunford

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Posted 14 July 2008 - 10:03 AM

Hand rolling tubes, one trick is NOT to keep the glue off the mandrel. If you make mandrel very gluey (!) the glue acts as a lube and lets the tube slide off easily. It also ensures you do not get a loose 'flap' on the inside of the tube which can allow fire to skip down the inside of the tube and cause unplanned explosions!

Don't know if this method would work on a machine, but might be worth a try...
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#19 bigtonyicu

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Posted 14 July 2008 - 01:57 PM

Hand rolling tubes, one trick is NOT to keep the glue off the mandrel. If you make mandrel very gluey (!) the glue acts as a lube and lets the tube slide off easily. It also ensures you do not get a loose 'flap' on the inside of the tube which can allow fire to skip down the inside of the tube and cause unplanned explosions!

Don't know if this method would work on a machine, but might be worth a try...



I'll give that a shot, the madrel was pretty dry just enought to be very tacky from the glue soaking through the paper

what kind of glue are you using Phil?

#20 Frozentech

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Posted 14 July 2008 - 03:59 PM

I agree with phildunford. I've had my best results hand rolling tubes, using PVA wood glue, with the mandrel liberally 'wet' with the glue. It's important to slide the tube off the mandrel before it sets up, of course. With a really thick ( 1/4") walled tube I rolled for a large star gun, I had to use a layer of parchment paper as the innermost layer. It was some white paper used to line baking sheets, I 'borrowed' a roll from my wife.
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#21 bigtonyicu

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Posted 14 July 2008 - 05:24 PM

I know I nagging to death the glue issue but someone also suggested I thin out the glue by adding 25% water.

Any thoughts?

I've just seen some people on youtube that are making rocket casing by just gluing the outside flap, I'm assuming the casing strength at that point would come from the papers tensile strength and the friction between the layer. Couldn’t we do the same with these tubes IE roll them dry and glue the final wrap?

Just thinking outside the box a little... trying to simplify things a little.

skylight has an article on tubes this week what a break (http://www.skylighte...le.asp?Item=130)

They use wood hardener... what is it? a low viscosity glue that soaks in the wood... if so could that be use with the above mention tube and use the wood hardener as a internal binder? (I just might try that in the next few days and see if what kind of burst strength I get.

Edited by bigtonyicu, 14 July 2008 - 05:31 PM.


#22 whitewolf_573

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Posted 15 July 2008 - 08:46 AM

When you roll tubes at home , if they are make well, they are enough resistant to use in maky king of pyro thigs like rocket cassigs,cardboard mortars,etc ?

Or for somethigs , in some moments industrial made tubes , bought i mean, could be better ?

Making your own cardboard tubes is one thing pretty interesting so i think this is a wonderful topic.
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#23 digger

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Posted 15 July 2008 - 09:21 AM

Interesting topic (esp about the mandrel fully covered in glue as this is something I have avoided when rolling tubes), there seems to be a few ways to skin the cat so to speak.

I assume that most of you have seen the tube rolling machines shown on youtube

vid 1
vid2

Now I would like to make a smaller version of one of those (maybe a little less automated).

Or for somethigs , in some moments industrial made tubes , bought i mean, could be better ?


I find that home made hand rolled tubes are far stronger that most commercial tubes by a long way (based on wall thickness).

I know I nagging to death the glue issue but someone also suggested I thin out the glue by adding 25% water


25% water sounds like a good place to start, after you have rolled a fair few tubes you will find a glue viscosity that gives you good results and is easy to use.

I've just seen some people on youtube that are making rocket casing by just gluing the outside flap, I'm assuming the casing strength at that point would come from the papers tensile strength and the friction between the layer. Couldn’t we do the same with these tubes IE roll them dry and glue the final wrap?


As mentioned earlier in this thread this can cause you to have a passfire flap. This would not be a problem in a pressed rocket application. You will also find that fully glued tubes are far stronger than this method.

Edited by digger, 15 July 2008 - 09:22 AM.

Phew that was close.

#24 portfire

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Posted 15 July 2008 - 10:12 AM

I'm not sure about completely gluing the first strip of kraft. As Phil said, this would act as the "lube", but this would obviously be no good when using wooden formers, so (again obviously) Aluminium or Brass formers would be needed. I do see a couple of drawbacks with this though, 1 being cleaning, 2 this could cause problems when ramming/pressing comps i.e. The ram scraping the glue off and taking some of the kraft with it, possibly causing a week point in the tube. This is probably just me over thinking though :rolleyes:

Regarding the inner "flap". What I do with the first strip is roll it over the former exposing the inner edge, I then apply around a 30mm strip of glue, roll the kraft back, then around the former. This glues the inner edge down, then I paste the rest of the of kraft and proceed to roll. The trick is not to roll the first part of the strip too tightly around the former, but just enough so it will slide with little force. Remember, the tube will shrink slightly on drying.

Hope that made sense, and helps in some way

P.S. Happy Birthday Phil

Edited by portfire, 15 July 2008 - 10:35 AM.

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#25 Pretty green flames

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Posted 15 July 2008 - 10:51 AM

One thing I've been wanting to ask. Everyone talks that the inner flap, when not glued, might cause blowthroughs. Did something like this ever happen to anyone?

If i'm honest i've never seen this phenomena. The rammed fuel or clay, with sufficient ramming, will seal it pretty darn well. Unless your tube rolling skills are non-existant, and you don't roll the paper tightly enough, I think that chances of this happening are rather slim. And besides, if you glue the mandrel you will just make an unholy mess and prevent the tubes from beeing dried on the former, which may lead to deformations. You don't even need to make a whole turn of paper before applying the glue,half a turn is plenty. With any other technique you are, in my opinion, just making your lives misserable.

#26 digger

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Posted 15 July 2008 - 10:56 AM

So (again obviously) Aluminium or Brass formers would be needed.


Or even stainless steel, that what I use as virtually every size is available from my local stockholder for a contribution to the tea fund if I go in on a Friday lunch time.


And besides, if you glue the mandrel you will just make an unholy mess and prevent the tubes from beeing dried on the former, which may lead to deformations. You don't even need to make a whole turn of paper before applying the glue,half a turn is plenty. With any other technique you are, in my opinion, just making your lives misserable.


You dry your tubes on the formers?
Phew that was close.

#27 Pretty green flames

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Posted 15 July 2008 - 11:04 AM

You dry your tubes on the formers?


Well I have Polished brass and aluminium formers for rolling, the tubes are dried on a wooden former, most of the tubes dried of the formers get deformed.

#28 digger

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Posted 15 July 2008 - 11:10 AM

Well I have Polished brass and aluminium formers for rolling, the tubes are dried on a wooden former, most of the tubes dried of the formers get deformed.


That sounds a bit of a bugger. I have never needed to dry tubes on formers, all of mine seem to dry fine without them.

What type of paper do you use for your tubes and what type of glue do you use?
Phew that was close.

#29 Pretty green flames

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Posted 15 July 2008 - 11:21 AM

Up to 20mm I use 50lb Craft paper, above 20mm I use thin recycled cardboard, I believe 250g/m2. The glue is PVAc Wood glue thinned with 30% water. Anyway, this is not really a problem as the ammount of tubes needed is small so I don't mind drying them on the former.

#30 portfire

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Posted 15 July 2008 - 12:01 PM

IMO thinning the PVA causes deformation. When I started rolling tubes I used to use 25%, and found alot were deforming, I then droped to 5-10% and still had the odd one. I now use neat PVA, and with the amount of tubes I roll don't get any. This is using 125gsm kraft BTW, which is the only paper I use for tubes now.

Good tip there Digger, with the stainless steel :)
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