Custom Mortar Tube Plugs

[BlastFromThePast]

I was able to source a bunch of tubes recently, and have found that none of them match either of the three different sized hole saws I have. I have one of those circle cutters from HF. Would I be able to use this thing on 3/4" pine and then glue 2 or 3 together to make a plug? How do you guys do it when you come across randomly sized tubes that you intend on using as mortars?

[Algenco]

sure, but for really strong plugs the grain should be vertical

make the plugs 1.5-2 x id

[BlastFromThePast]

But you think that the circle cutter will make it through 3/4" pine?

 

-edit: I have no idea what commercial plugs are like for HDPE mortars nor do I know how tight fitting they are or if they are glued in place. What's the best way to secure the plugs? Glue, screws, friction tape...?

Edited April 24, 2013 by BlastFromThePast

[Bobosan]

If you can't get or make vertical grain plugs, you could always use two discs and align the grain at 90 degrees on each disc. Pics are my home made 3" mortar and endplug. The plugs use two 3/4" thick discs glued and screwed together .They are the same thickness as commercially available plugs.

[BlastFromThePast]

Thanks for the pics and the tip on phasing the grains by 90 degrees. I know I asked this above but how are they secured to the mortar? and what's the hook for, pulling the plugs out?

[Bobosan]

I use wood glue and drywall screws...same type and length screws used to screw the discs together. You can see one of the side screws in bottom pic.

 

The hooks are just to hang them for drying after sealing and painting. They are removed when done.

[BlastFromThePast]

Gotcha. Well I got my circle cutter to work after 3 failed attempts and some fine tuning and now I've got four beautiful 1 7/8" x 3/4" plugs. I'm going to glue 2 together and bolt them together, and like you said, probably wind up using 3 1 1/4" drywall screws to secure them. Thanks for the help!

[Arthur]

My findings have been that odd tubes never fit the standard sizes of shells, and are rarely thick enough walled. When I found some 3" bore tubes with 3/4 thick walls I simply put some gaffer tape over the bottom and carefully poured in some polyester resin which I filled in situ with really dry sharp sand two hours later I had mortars with a plug 1.5" thick permanently glued in

[psyco_1322]

If you can cut a plug that's fairly close, you can roll up heavily glued chipboard around them to bring the size up to what you need.

[BlastFromThePast]

Just curious, but for commercially available 3" HDPE mortars, what are the wall thicknesses for those like? And how much does wall thickness increase, if it does at all, as you go to larger mortars?

 

The tube I used in like 1 and 7/8" dia and the walls are a good 3/8" thick.

[Bobosan]

3/16" thick wall on a Pyrodirect 3" HDPE tube. Yes, HDPE walls get thicker as the tube diameter increases.

 

The 3" cardboard ones I work with have 5/16" wall.

Edited April 25, 2013 by Bobosan

[BlastFromThePast]

Okay so yeah those cardboards you've got are only 1/16" less then mine. Are they parallel or spiral wound?

[Bobosan]

Spiral. They are coated with Minwax wood sealer before painting with BBQ grill flat black. Lift area is reinforced with fiberglass packing tape. Overkill I think and don't expect them to last forever. They do launch baseballs quite nicely. Haven't progressed to shell making yet. Edited April 25, 2013 by Bobosan

[Mumbles]

Here's a list of common HDPE sizes. Nothing we get is custom, usually just picking the closest one to the size we want.

 

http://www.petersenproducts.com/Specifications/Pipe_HDPE.aspx