First mortar rack design.

[gman]

Hey guys, I'm new here. I'm planning on making some mortar racks that fit dr11 HDPE pipe for consumer shells and I'd like to get your guys' input on this. I'll be buying 50 mortars, and I'll make 10 racks. The holes on the sides are for a bolt/wingnut that will attach to some plywood or 2-bys (haven't decided yet) with many holes in them so I can flexibly arrange them in a finale or fan rack style. 2.5" holes will be bored out with a 2.5" DIA hole saw (bi-metal's okay right? and do you suggest getting an arbor?). all the wood here will be treated 2x4.
It seems sturdy enough. What do you suggest for fastener type (screws preferably) and placement?

Any advice would be great.


Forgot to attach:

[WWhite]

somebody help me out, the "...." rack. I'm spacing and I built some from him. Found it. CamelJoe...racks are still rock solid

http://www.pyrouniverse.com/forum/sh...ght=rack+build

[gman]

I had forgotten to attach the image last night and no moderator was on to approve the thread so I had to wait until today:



Is .5" too small from the edge of the circle to the side of the 2x4?

[mrk874]

I really like this design - nice work! They can go together with as few as 12 screws. The great part is all you need is 2x4s and screws.

A little work with the hole saw - that will get tedious. The bonus is you don't need spacers or side rails. That saves a lot of cutting.

Are you planning 2" or 2.5" screws? I'm thinking of building some of these myself. I was planning on the Camjoe design, but I think I'll modify to build these for the racks and use Camjoe's end board design.

One thing I'm not sure on is the durability vs camjoe's. You're putting screws down in from the top and probably lifting from the top, hopefully it holds up long term. Maybe add some wood glue on all joints when assembling and you'll have plenty of strength.

I woudn't use pressure treated lumber. Too expensive for one, way more work to cut with the hole saw, and adds too much weight, and the dust from the hole saw will give you cancer. Paint em if you want to protect them, or maybe just spray on some thompsons water seal.

Anyone have a good idea on how to cut the holes - anything better than a hole saw? I would imagine if you had a drill press you could attach a hole saw and get through it quicker.

[gman]

@mrk thanks for the reply. Arbored hole saw for sure if I'm going to make 100 cuts. I may make this rack fit one more mortar for 6 per rack, then make 8 racks for 48 mortars just to have the multiple-of-6 thing going. I'm afraid of rot, I'd like these to last long, perhaps I will paint them. Do you think the 1/2" of wood between the holes and the sides of the 2x4 is too small? Good point on lifting the racks, maybe I'll make the sides 1.5" taller and the top hole board fit on the inside.

[gman]

Also, I'll probably use 2.5" screws how do these look?
http://www.lowes.com/pd_68356-37672-...rew&facetInfo=

I'll just have to be careful not to put a screw through the hole.

2 screws a joint?

[mrk874]

Yes, I would use 2 screws per joint - those zinc screws will last. For the top, 2 screws straight down should hold together pretty good. I think it will hold up better than making the sides taller and putting the holes board inside. Ignore my last comment on durability - it will be fine with 4 screws total. Just pre-drill and coat the joint with wood glue.

For your other question, 1/2" is enough between the edge and the mortar. Post some completed pics when you've built it!

[tradami]

What happens to all of the loaded, lit, tubes when a canister blows up inside one of them?..

[gman]

@mrk could you clarify what you were saying by 4 screws total?

My biggest fear is that the .5" between the edges of the holes and the edge of the 2x4 would be too small, make it weak.

@tradami The plugs will probably be 1.5", not sure where exactly I'll buy the mortars from yet. So all the shells should be above that second 2x4. Would it blow one of the sides off? Or would it make the other mortars jump out of their seats? I'd love to hear your concerns/suggestions

[mrk874]

What happens to all of the loaded, lit, tubes when a canister blows up inside one of them?..

Always good to think about the worst case - an upside down shell test would be a good idea. 1" distance between tubes and proper staking should be good? If one blows up, the others will likely still fire OK. To be extra safe, you could go to 1.5" between tubes, what do you think tradami? I've never witnessed a rack with spacing like this have a cascade failure (I definitely haven't seen everything though). Wouldn't the HDPE tube the exploding shell is in absorb most of the blast? Then you have 1" of open air for the blast to dissipate a little before it hits the other tubes. I would expect you may need to discard the neighboring tubes if they are damaged. Many still build racks with no spacing, which is much more likely to lead to multiple failures.

You might suggest some wood spacers to run between each tube to absorb the blast and increase safety, but at that point, the benefits of this rack are mostly lost and gman might as well build camjoe racks (considered the gold standard by most, it's a great design). I like gman's rack design for simplicity.

For damage, expect you may need to replace the bottom hole board. Maybe a good idea to not glue that one down then.

[ziptie2k2]

What happens to all of the loaded, lit, tubes when a canister blows up inside one of them?..

First will be "OH S**T", then there will be damage. What kind of damage? Who knows. I can imagine the top or bottom (or both) 2x4(s) may split. Could glue some plywood with the same hole spacing on to of each 2x4 with the holes. This will add a bunch more labor, and cost. Just a thought though. I can tell they'll look pretty darn sharp when finished though.

[gman]

I've changed the design to include a sixth mortar. Not too many is it?

Also, if there's any doubt about safety, should I just throw a screw or two into each of the plugs on the bottom?

[gman]

Here's what I have so far:



Please criticize the hell out of this. If there's anything I'm doing wrong, could somebody talk with me about it?