12 replies to this topic

[pyrotechnist]

I have just recently made two motor tubes out of 160gsm card, using 3 sheets of it, and PVA + wheat past mix for the glue and while drying they seem to be deforming a lot. I have the tubes laid down and somehow they are bending slowly to one side and the walls are closing in a bit causing the tubes to look slightly squashed. Does anyone know how to stop this problem occurring or what it may be? Keeping the former within the tubes is a no go as I have 78 tubes to roll and only one former.

[CanadianPyro]

When I roll tubes, I usually wrap a wooden dowel with a material that PVA glue won't adhere to such as thin polyethylene sheet, then roll the tubes around it and allow them to solidify on the dowel. This prevents deformation, and once dry, the tubes can be slid off the dowel.

[pyrotechnist]

Thanks for the info though I only have one dowel and 78 tubes to roll by 6 weeks time. I dont know how the Chinese can keep their tubes from deforming while drying then again I aint sure what type of glue they use neither.

[cooperman435]

Personally Id advise very little glue. If you apply the glue quickly to the surface then roll the tube it isnt actually wet throughout and dries much faster and without deforming.

If you wet your paper with glue it will shrink when drying causing some distortion and when wet will allow it to deform under gravity

[phildunford]

Sounds like maybe the paper is getting too wet.

I know traditionally you paste loads of sheets at once and let the paste soak in, but I get better results by pasting one sheet at a time quickly with only slightly dilute PVA and rolling at once. I paint or varnish wooden formers and cover them in glue so the case can slip off - rather the opposite approach of trying to keep the former dry!

[pyrotechnist]

Thanks for that ill try that out and see how it goes, I suspect the wheat past may be absorbing into the paper readily helping with the deformation though I will see how it goes with less glue.

[Mortartube]

Are you drying them at room temperature? If you apply heat they are likely to deform. I will also give opposite advice. Let the glue soak in. Uneven absorbtion may lead to uneven drying. As you are using card I think letting it soak is more advisable. With paper it seems less critical.

Have an experiment. Putting your tubes in a sieve or on mesh helps to promote even drying. Even one of those anti splatter screens for over frying pans, propped up on a couple of old books is good.

[RFD]

Perhaps hanging them clothes line style might help,good air curculation and possibly gravity helping to keep them straight,i think there is some good info in weingart that might help as well.

[BrightStar]

Well they do say 'ask six pyros, you'll get a dozen answers'!

Rolling with thin cardboard, I use undiluted PVA sparingly. I temporarily add some tape to help it hold its shape then dry it off the mandrel. You might get similar results using an outer wrap of thinner paper.

Edited by BrightStar, 18 November 2009 - 06:42 PM.

[portfire]

Stand your tubes up!

I use 125gsm and straight PVA. Once you've rolled the "inner" part of the tube, paste a couple more sheets, then roll. The probable course is the water content of the wheat paste, a thin layer of straight PVA is all thats needed.

As said dry them at room temp, then leave them a couple of days where you will be loading the tubes.

Theres a few more tricks, but I cant post them, as there for paying members, unless you visit the UKPS shop

[wjames]

i use Pva+10% water - heated up ( to around 40 degrees)

Wooden dowel as former - once ive got it started, i pour glue into the gap thats formed - where the paper begins to curl round the former, and, whilst applying pressure, roll the tube - gives a nice even coat of glue - and nice straight strong tubes. Dry them on an old ironing board, of the mesh type, with no cover on.

[pyrotechnist]

Tried standing them up and they seem to want to kink to one side though funnily enougth they kind of go back straight once fully dry but its weird as I end up with all sorts of weird angles while they are still slightly damp . Problem with straight PVA is that a big blob doesn't seem to go far and is really stiff to spread, well mine is anyhow. It is a similar effect to what happens when you stick your tubes in the oven to dry quickly, though they go rock hard they kind of deform a lot though I find bought tubes do not which is strange. I assume the chinese would use some sort of wheat type past still though I may be wrong. I did see a documentary about cardboard manufacturers using wheat past for creating corrugated card sheeting so this stuff may still be applied to tube manufacture and if that is the case theirs do not deform at all so its just my crap rolling.

Any great tube roller out there wanting to help a fellow pyro roll 78 1.7" I.D by 12" long motor tubes lol?

[portfire]

Any great tube roller out there wanting to help a fellow pyro roll 78 1.7" I.D by 12" long motor tubes lol?

At a price ya

Drop pyromaniac303 a PM if your after some 2" tubes mate, though 78 could be a push