Standard tube sizes?

[Arthur]

In reality tubes don't vary much from nominal, but they are made of paper so there is some dimension change with the weather -especially humidity.

[DavidF]

Oldmarine, one experienced rocket maker uses cylindrical shims under his spindles to press different length rockets of the same ID in a single clamshell support. Of course, that means the spindle base must fit up inside the support. Getting that done is still cheaper than having multiple clamshells! With his 10" support he can use stinger tooling, whistle, universal, and BP all with one support. I'll see if I can find a picture he sent me.

 

I make my own supports cheaply enough that I can have supports in various lengths. The ID's of my supports are adjustable too, so tube OD is a non-issue for me. I can and have pressed 1# and 3# rockets with the same support if the lengths of the tubes are similar. I have now pressed several hundred rockets with my homemade supports.

 

You can make anywhere from a 6" long to 12" long support for anywhere from a 1# to 3# rocket for 60 or 70 bucks. My 6" long support that I use for 3# strobe rockets took minutes to make- 20 bucks. No toolmaker has yet tried or commented on my cheap supports.

 

I developed my supports to deal with problems of OD variations from batch to batch and also within the same batch, of NEPT tubes. I have previously worked with split PVC supports, a clamshell support, and also a collette-style support. Split PVC supports are annoying to use but work very well. They also adapt to minor variations in tube OD.

 

The people that sell tubes don't sell tube supports. The people that sell tube supports don't sell tubes. So, if your tubes fall through your closed support like mine did, it's your problem, and nobodys fault. It would be ideal if either the tube seller or the support seller would sell both items and accept responsibility for fit. But, they don't. And they don't make the tubes either! So, if you have a problem with fit, the best you can expect is a sympathetic ear, and suggestions on how to make your poor fit "less poor".

 

My involvement in the so-called 'pedantic' discussion about tubes relied on specific statements, measurements, and verifiable facts. Those things were based on my experiences with the subject at hand. My statements were certainly considered unpopular and unwelcome- but not incorrect. I hope this post doesn't open another can of worms. I have no problem demonstrating the veracity of any statement I make, if asked. Just my take on this sometimes irksome issue. Please don't stone me;)

[OldMarine]

I'd love to see some pics of those supports. I don't have an opinion as yet and am so open minded I have to wear screen earmuffs to keep the flies out. Caleb says shims just like you mentioned can be made for my support. So far I have Wolter gerb tooling and the support. As I graduate to rockets I'll get him to hook me up. Who am I kidding, I'll get'm as soon as the funds are available. Edited November 17, 2015 by OldMarine

[DavidF]

http://www.pyrobin.com/files/brass%20tube%20supports%20022.JPG

 

Here are a bunch of my supports. I have nothing to sell. I give the ideas for free to anybody with interest. In my opinion, they are better than anything available for purchase in many ways- Not ALL ways, many ways. They are inexpensive, fairly easy to make, and adjustable to suit varying tube OD's. They are ideal for rockets from 1# to 3#, the most popular sizes. For smaller rockets, I would not use this type of support.

 

The brass shim stock is readily available. I use .005" material. I have tried thinner and thicker. Don't bother. It may seem that the only thing that holds these things together is rubber bands and tape. That's because it's true. You can press 1# rockets to 15000psi with these things. The rockets will be perfect in appearance. There are no clamps of any kind ever used. Just the brass, the plastic washer, 2 rubber bands, and 2 or 3 rounds of filament tape.

 

These supports are faster to use than other types, once you get the simple knack. They are not as pretty as clamshells, and they don't stand as naturally perfectly straight as clamshells. But, at a small fraction of the price, they allow pyros to save money on the most expensive rocket tooling items- clamshells or collette-style tube supports. And they are much lighter than clamshells. For long-spindled rockets, I made a simple device to keep the spindle aligned perfectly.

 

In use these supports need to have a plastic washer underneath them. Otherwise the downward pressing force will deform the bottom edge, which pretty much wrecks the thing. But, they can be fixed. I would not use these for hand ramming.

I have pressed all my rockets for the last 3 years with these supports. I generally press to 9000psi, even though I don't have to.

 

At first I had a few bugs to work out. I have learned a lot after making hundreds of rockets with these supports, but I'm not going to write a big story about the details right now. If there are questions I can answer them.

[OldMarine]

That is brass shim stock isn't it? I saw a tutorial somewhere on using that as a tube support. Surface tension/friction keeps it tight. If I recall the poster had some trouble getting the cut edges flat and smooth enough to keep the rolled layers tight. How did you accomplish this? A shear with that length would be giant.

[DavidF]

I did a couple of youtube videos showing my earlier work on these. I did run into some problems and solved them. Ned Gorski made a tutorial, but he changed some things. I didn't agree with the changes. I use the whole length of the roll as purchased for each support. Also, we both laid out the whole roll of shim stock in the beginning- as in Ned's tutorial. I later found that this was not necessary. The roll can be held with clothes pins as it is partially unrolled and re-rolled, like a scroll. The reason for unrolling and re-rolling is because sometimes the roll is damaged on the inside edge. We want a nice clean inside edge on the finished support

 

Cutting the brass to tube length is a PITA! I wrap the brass tightly around a dowel or tube and tape it securely on both sides of the cut. I then cut it with a 1/16" blade on a zip grinder. Then I true up the edge with a disc sander, bit by bit. That's the PITA part. It takes a while to get it just right, and can't be rushed. Forget about scissors. They leave a burr. Fixing the burr ends up harder than avoiding it. Also, forget about scoring and bending. Same problem. The whole reason the zip grinder works is that the brass is not mashed or crushed, and the sanding of the cut end doesn't damage it either.

 

This shim stock is .005" thick, about that of thick printer paper. So, yes, it is delicate. If you drop it, it will be damaged. I have repaired dropped supports. It is important to note that once the item is made, it will never be unrolled again. It will be for all intents and purposes like a piece of brass pipe. The deformation of the cut end was caused by the relatively soft thin layers of brass pressing down on the spindle base when pressing the increments. Fabricating a plastic washer to slip under the support perfectly solves that problem. This was one of the original bugs that had to be worked out.

 

Another bug (related to the first) was that I originally used a single clamp in the middle of the support to secure it. This gave the support rigidity, which was a contributing factor to the damage on the bottom edges. The clamp has since been replaced with filament tape, 2 or 3 rounds. The only reason the support needs to be secured is because of the twisting motion often used when removing rammers. If you twist the wrong way once, you loosen the support. Then you get compression wrinkles in the tube, which could lead to CATO. With the filament tape snugly applied, this does not happen. The support has just enough flex to do the job with high strength and no damage to the support. So, both those improvements together solved the deformation issue.

 

The brass is naturally springy. The rubber bands counter that springiness, and keep the support solid. To undo the support and release the finished motor, the tape is removed, and the motor is turned counter-clockwise. This will crack the motor loose and it can be easily slid out. It takes longer to type than to do.

 

I hope these additional details make it a little more clear. I regret that I am unable to be succinct.

[OldMarine]

That was an excellent description. Someone had an expansion type twist handle they used to tighten and free the tubes but I can't recall who it was right now. Do you use something like this?

I'd like to be able to use something like these supports for things I'd like to try but maybe not stick with since they can, as you said, serve multiple purposes.

Another question just came to mind: Do you need to degrease the brass before using? Oft times it's oiled to stop oxidation. I haven't seen this addressed but although grease could increase surface tension it is, even if viscous,a lubricant.

I regret to inform you that once I've latched onto your ear I'll pummel you with questions. Please be prepared!

[DavidF]

That was me with the winding tool I originally used. I wracked my brain trying to come up with a better tool, but in the end, a rubber gloved hand works well. This is for the tightening, which I didn't really explain.

 

To load a tube for pressing, the brass is brought to an ID that is JUST large enough to slide the tube in. The ends of the tube are previously cleaned up. As the picture shows, the support is held tight by rubber bands. The tube is inserted into the support just a bit. Then the tube is wiped with a sponge that is damp, but not dripping. The tube is pushed all the way down into the support on a table. The dampening makes the tube swell slightly. That's why it 'grabs' the inside of the brass. The tiny amount of moisture is of no concern. With the rubber glove hand, stick the appropriate appendage into the tube. With the support standing on the table, it is simply twisted tight by hand. The rubber bands keep it there, until the 2 or 3 wraps of filament taped are applied to fully secure it. The plastic washer is slipped on the spindle base. It is of such a size that the tube and support both sit on it. It is absolutely critical. Now, the rocket is ready to press.

 

I haven't ever found the brass to be greasy, so I have never had to clean it. I've seen the odd dried blood smears on the rolls though.

 

I don't mind questions. I like to ramble

[OldMarine]

Thanks! I know if a video of the use of those supports would be greatly appreciated buy at least one pyro...

[Col]

That was me with the winding tool I originally used. I wracked my brain trying to come up with a better tool, but in the end, a rubber gloved hand works well. This is for the tightening, which I didn't really explain.

 

 

Hi David

10 out of 10 for innovation, thinking outside the box

You could use expanding pipe bungs to rotate the tube. The 1/2" size runs 12-16mm, 3/4" size runs 18-24mm, 1" size runs 23-32mm.They cost less than £2 each over here.

[Maserface]

I've been using these types of supports exclusively for over a year, love em

[DavidF]

OK, I made a video demonstrating how I use a 6" wide roll of brass shim stock to 'make' a support for a 3lb strobe rocket. Unfortunately, the rambling and babbling led to a video almost 15 minutes long! The file size is huge. If anybody knows how I can make the file smaller without wrecking it, I would appreciate it. Then I would replace the one I made with a more data-friendly option.

This video shows how it works, and how to adjust the ID for different tube sizes. I will make another much shorter one showing the finished motor as it is removed quickly, and in pristine condition, after being pressed to 9000psi.

https://www.youtube.com/watch?v=7WHIrJ0AGiA

 

EDIT: I replaced the much larger file with a 358MB version.

Edited November 20, 2015 by DavidF

[OldMarine]

Thanks much! I'll be shopping me some shim stock for Christmas. Glad to see it will crank down to 1# because I plan on doing a few Saxons and wheels with them for NYE.

[DavidF]

OldMarine, here is the second part I promised. This video shows the finished motors and how easily they are removed from the support. The same out of the box support that made the 3lb rockets is then used to make a 1lb rocket. The rockets are flown successfully.

https://www.youtube.com/watch?v=hDY_yz-QpGA

 

Looking back, I see that maybe it would have been more appropriate to put my videos in the Member Tutorials section. But I was just following the conversation. I will be more aware in the future.

[Col]

Hi David,

I couldnt resist making one, marvellously simple design and only took 10 minutes

When going from 1lb to 3lb tubes, a few plastic washers with holes the same od as the 3lb support will act as a stop/brake to reduce the risk of overshooting as it loosens up.

 

[DavidF]

That's a handy idea Col. Don't forget the plastic washer for underneath too

[Col]

I knocked a few up from 3mm nylon sheet while i was waiting for the brass to arrive Getting the brass to grip my tubes is a bit hit and miss, lightly sanding the tubes before dampening them seems to help. .

[OldMarine]

Pressed a few 1"x5" charcoal gerbs using my brass support on my new press. Worked like a charm. I was able to use some of Phil's thinner tubes with no problemo!