30 December 2009

RightTool(tm) for the job

A revelation struck me while putting together a Midway order. I started to order 200 rounds of .30-06 brass when I remembered there are several coffee cans full of MilSurp brass in the garage that I can't use because of the primer pocket. These 200 pieces of brass represented about 70% of the cost of the RightTool(tm) to solve that problem! I canceled the order.

A friend and I made the trek to North Scottsdale today.. I asked for demo of the tool and asked a couple questions. I even brought a couple rounds of the offending brass. Unfortunately the demo was set up for small rifle primers rather than the .30-06 and really didn't teach me anything, nor did most of the questions. However the final question was good enough to seal the sale "If it doesn't work for me, can I bring it back?" She said "yes" and the RightTool followed me home

Back at the SandCastle, I read the manual which is only two 4x6" pages. It didn't take long. A couple measurements, $3 at Ace hardware, a couple minutes with the drill and the unit was mounted to the loading bench.

The first six pieces of brass were swaged and mounted in the press. The primers seated easily! WOO HOO!!! The RightTool works!

The picture here shows the RightTool mounted on the reloading bench. The empty brass immediate left of the blue unit is my carefully hoarded 50 pieces of usable .30-06 brass. It is commercial stuff scrounged from the range. The surrounding three coffee cans of brass and white bin show the quantity of MilSurp brass that was previously unusable. (The white plastic container contains 100 pieces of processed brass, swaged, sized and ready to reload. Bottom left is the 11 test rounds loaded and ready to try. These have the same loads as previously loaded (47.1 gr IMR4895/150 gr Hornady RN/BT). These will be tested before loading more.

Prepping the MilSurp brass adds a lot of time to the reloading process but this is a one time investment. Those crimped primers take a lot of effort to punch out. I ran the depriming pin well down into the die so it would punch out the primer without resizing the brass thus reducing the arm effort. Then a trip through the swager and then back through the resizing die to actually resize the brass. This is a one-by-one process, not part of the progressive reloading process.

22 December 2009

Desktop Artillery, Midieval Style

The SCSon's school science fair is gearing up to the science night show late January. His team chose the category of weight and motion or something. Last week the teacher asked apologetically* "Can you build a catapult for the science fair?"

Kits are available for purchase over the internet. However we didn't have time to wait for shipping. Instead I studied medieval designs looked at pictures, as well as some of the "pumpkin chunkin" engineering marvels.

Design criteria required throw weights from 5g to 20g.

A simple catapult is an easy design, lever powered by a spring mechanism (probably a rubber band in this case). I recall constructing one in Boy Scouts in the previous millennium. The downside A catapult needs a stop mechanism equal to the power of the torsion mechanism. This is a waste. I'd rather put the effort into power than brakes, cuz brakes only slow you down! I also recall the Boy Scout catapult didn't last very long.

The Trebuche is a more elegant design, but still simple enough. It uses a lever arm powered by a counter weight hanging off the short end of the lever. The long end of the lever pulls a sling to take advantage of the whipping action to accelerate the projectile. The sling is held captive on one side at the end of the lever arm and the other held loosely on a "finger". Release point is adjusted by adjusting the finger angle.

We hit Home Depot for supplies. First we checked the 55 cent rem bucket for a something to use as a base. The rem bucket was no where in sight, but there was an 18" section of 2x6 in the garbage can. That went into the cart. (side note: The HD Cashier accepted the explanation and gave us the board. Hence the plug as a quid-pro-quo). We also picked up a 1/2" and 3/8" dowel, a bolt and a stack of fender washers (at $0.18 each!). That and four 87cent 4-packs of incandescent bulbs (banned by congress after 2012) still came in under $10.

Measurements and design were from the TLAR* school of engineering. The axle is ~9" off the platform and the beam is ~13" long. The main uprights are 1/2" dowel while the lever arm and struts are 3/8" dowel. A cut off 16 penny nail forms the axle while a 3/8" bolt suspended the counterweights. The SCQueen had the sewing machine setup for Christmas gifts and sewing the sling was a two minute job.

Historical accounts from the 12-15th century talk about throwing 2-300lb stones 300 yards with 12,000lb counter weight. The stones would hit with enough force to knock down the castle walls of the day and forced a complete defensive rethink. I needed the data to estimate a ballast/projectile ratio. 50:1 is in the ballpark. That means ~500g (one pound-ish) to throw the 10g weight. That would provide an over/under for the other weights. Clearly the fender washers purchased were well under weight. We scrounged around the house looking for appropriate ballast. The Hornady box of 100 150 grain 30-06 bullets was heavy enough and plenty dense. But even if sealed in an opaque container (probably a cloth sac), there is a chance the beans might spill and cause exploding PSH that could splash back on the SCClan. That idea was rejected.

The SCQueen found a couple large sockets in the tool box. Experimenting around we found a couple sockets that would nest conveniently and a longer bolt to suspend the stack. It was still short enough to allow the beam to swing freely. Total weight of the three socket stack was about 1.5 lb (750gram).

Kitchen table experiments showed this was a little overpowered for the 5gram weights. (The SCQueen was seriously concerned for the safety of the pictures on the far wall of the SandCastle.) One socket was removed to de-power the weapon. I could also see the points on the end of the lever arm could harm an unwary user and added a couple warning labels "Sharp points" and "Safety Glasses required". Probably not enough to satisfy OSHA or a PI lawyer but I tried. My son was a probable operator so I'm well motivated to ensure he's not hurt in the process. Still I insisted on eye protection for all team members.

Results -
The team's first attempts to throw were unsuccessful. I suspected operator error and suggested some training. We bumped into the teacher at a school function. It just so happened I had some time off the next day and I offered to work with the team. She gladly accepted and offered "any time". That night we again scrounged the garage for accurate masses. The bolt bucket held masses that were close but high. This is good as the grinder can fix that! Within 30 minutes we had 5, 10, 15 and 20g masses accurate to a couple .01g.

The team's problem likely was related to the plastic "Easter eggs" their masses were contained in. They were simply over sized for the sling. Sorry, that wasn't in the Design objective document ;-) The Frankford Arsenal scale I'd borrowed from the reloading bench showed their weights were 5g over.

The trebuchet was well tuned for the 5gram weights. They were consistently thrown in the 18 foot range. We didn't retune for different weights and as a result while some 20g weights flew 36 inches, some released prematurely and only flew a high arc landing only ~11 inches from the datum.

A co-worker asked "was on wheels?" and pointed out that they later found it would throw about 30% further with less stress on the structure if it had wheels. The idea is that the ballast wants to fall straight down but the lever arm forces it to translate aft. If the device is on wheels, the falling weight pulls the rest of the structure forward instead of the mass aft, imparting even more speed to the tip of the lever. It works even better if just the axle is allowed to float as only the mass of the axle, lever arm and projectile are accelerated rather than the entire structure. (I smell a v2.0 in the works).

Epilogue -
I fear my zeal for technology (in a medieval way) may have overshadowed the point of the exercise. The real goal was probably to show the F = MA effects. For a given force, higher mass means less acceleration, less "muzzle" velocity, less distance. The straight catapult would probably have provided a more consistent F with fewer variables to control. But the Trebuchet scores an order of magnitude higher on the coolness scale! And besides, I always wanted to build one! I'm an engineering geek, guilty as charged. (I'll skip the proper analysis of how the catapult's F varies with position/spring tension that is a staple of a decent DiffyQ class. Too many years of dis-use. The Trebuchet is that times 5 and I'm not going there either ;-) For this age "lighter = further" is probably all the results they need.

Meanwhile, these pikers*** had so much to work with and yet stopped short of their capability. If they had placed the projectile near the base with the tip of the throwing arm near the ground, they could have thrown considerably further.

* She knew we would be spending all day Saturday coaching another school function.
** TLAR = "That Looks About Right"
*** While I "disparage" them for the near miss, I envy what they did and always wanted an excuse to link their geekery!

07 December 2009

Remembering December 7th, 1941

Visiting the USS Arizona memorial was pretty high on my list of "things to do this life". We finally made it this summer:

Oil still rises from the hull. (click on images for full size)


Names inside the memorial.


Leaving the memorial.

02 December 2009

Note to self

Your carelessness lack of attention to detail is writing checks your skills can't cash.

So the creator of the November ePostal match, apparently drawing on "lessons learned" from previous contests, thoughtfully included a ruler on the target so a shooter could easily tell if the target was sized correctly or not. That's a great idea!

I printed the first set of targets on the SCQueens inkjet and checked the ruler. It was a little off but by only a hair. Next set of targets were printed on someone else's laserjet and I didn't bother to check the ruler since "it looked about right".

Scoring the targets back home, there was one shot that narrowly missed the Bond Girl off the top. Now I vaguely recall adding a trapazoidal shape above the legs to fill in the gap and yet here was a gap big enough to drive a .30 cal bullet through with room to spare. Hmmm, that's odd...[cue minor irritation in the Force] In the short run though, I can see a clear white line between the hit and the BG so it scores as a simple miss instead of a Bond Girl Hit.


It wasn't until reviewing targets submitted from other shooters, targets that showed the BG extending very close to the top edge of the paper. So how is it possible for my shot to miss and still keep on paper.. Here is a snippet of the original target. Notice the BG extending nearly to the top of the paper.

After reviewing half a dozen targets, it struck me to check the ruler again. Sure enough targets are 15 or 20% too small!

That ruler was a stroke of genius by the match master. You have no one to blame but yourself for NOT CHECKING TO MAKE SURE YOUR TARGETS ARE SIZED ACCORDINGLY! The matchmaster does not make allowance for your carelessness and your shooting skills aren't nearly good enough to make up the difference. You have no one to blame but yourself.

Update... "Carelessness" never felt like the work I was looking for... Edited to replace it with "Lack of attention to detail".

01 December 2009

The Envelope Please...

And the November ePostal results are in, may I have the envelope please:

Mr. C has the high score - 21 in class 2 with no BG hits. He notes a couple misses were due to forgetting the holdover on his Red Dot scope.

And Merle M earns the Most Prolific award - with at least one, sometimes multiple entries in classes 1 through 7 inclusive! As well as shooting most classes he's at or near the top of each class. Good Shootin' Merle!

Thanks to everyone who entered. Especially those that had the guts to submit scores in the 0 range. As noted several times, 0 was mid point of the possible scoring range and a 0 score led one class for quite some time. Anyway, I hope you had as much fun shooting the match as I did hosting it even if you did not submit the scores.

 

Shooter

Make

Model

Villain Hits

Bond Girl Hits

Score

Tie Breakers

Class 0.5 – Airsoft

     
 

Duane Hakala

Classic Army

M14 Scout

11

0

11

0

 

Ian Argent

Cybergun

Colt National Match

10

1

9

5

Class 1, Rimfire pistol – Iron Sights

     
 

Billll

Ruger

MK I

13

0

13

8

 

Engineering Johnson

Ruger

Single Six

11

0

11

9

 

Ian Argent

Walther

P-22 Long Barrel

8

1

7

5

 

Merle M

Ruger

SSS .22 Mag

9

2

7

0

 

Paula

Ruger

MK II

7

2

5

8

 

James

Ruger

MK II

5

1

4

8

 

TrueBlueSam

Ruger

Single Six

5

1

4

0

 

Danno

Ruger

.22/45

6

3

3

11

 

Froggy

Ruger

Single Six

2

1

1

0

Class 2, Rimfire pistol – Optic Sights

     
 

Mr. C

High Standard/Red Dot

Supermatic Citation

21

0

21

0

 

Merle M

Ruger

Mk 2, Tasco 2-7x set on 2x.

13

0

13

0

 

Merle M

TC

10” Contender

13

0

13

0

Class 3 Centerfire Pistol – Iron Sights

     
 

Merle M

S&W

M3913 LS

9

0

9

0

 

Merle M

Walther

P38

10

2

8

0

 

Merle M

TC 38-40 WCF

Contender

8

1

7

 
 

Ian Argent

Glock

17L

8

2

6

5

 

Robert Lund

S&W G42

G42

1

5

-4

0

Class 4 Centerfire Pistol – Optic Sights

     
 

Merle M

TC

10” Contender 9mm

9

2

7

0

Class 5 rimfire Rifle – Iron sights

     
 

Merle M

Iver Johnson

.22 Carbine

11

1

10

0

 

Merle M

Savage

M72

7

0

7

0

 

Ian Argent

Springfield

84C

1

1

0

5

 

Robert Lund

Winchester

94-22

5

6

-1

0

Class 6, Rimfire Rifle – Optic Sights

     
 

Merle M

Ruger

10/22

16

0

16

0

 

Merle M

Marlin

M39A Marlin

16

0

16

0

 

Billll

Remington

Nylon 66 (.22)

13

0

13

8

 

Danno

Ruger

10/22

6

1

5

11

 

Paula

Remington

Nylon 66 (.22)

5

2

3

8

Class 7, Centerfire Rifle, Iron Sights

     
 

Merle M

Ruger

Mini 14

8

0

8

0

Class 8, Centerfire Rifle, Optic Sights

     
 

Danno

Inland

M1 Carbine

3

1

2

11