Kirk – Page 4 – Irrelevant Tech

Draining Garden Hoses

If you drain garden hoses in the fall or between jobs and have a portable air compressor you may find this adapter a big time saver. It is assembled out of a few dollars worth of parts from the hardware store: a ball type hose valve, an air hose adapter, an appropriate thread adapter, and thread tape.

With the valve off, attach the adapter to your air compressor. Run the compressor to shut-off, unplug it, and carry it to your hose. Remove the hose nozzle and secure the hose end as it may thrash around. Disconnect the hose from the water source and attach it to the adapter. Crack the valve open slightly to start the water flowing. Moderate the valve to get a typical flow. When the hose starts to sputter, briefly open the valve fully to blow the last of the water out.

This will empty reeled hose as well as coiled or loose. A 3 gallon tank will clear a 50 foot hose in one shot. A 6 gallon tank is sufficient for a 100 foot hose or a couple of 50 foot hoses.

Chopped PID Control of Processes with Delay

For nearly 100 years PID controllers have been the standard for feedback control of a wide range of processes including autopilots, automotive cruise control, industrial heating, servo positioning, and motor speed control. PID stands for Proportional-Integral-Derivative, also called Span-Reset-Rate in earlier times. The PID controller reads the process variable, PV, such as temperature or position to be controlled. The value is compared to a setpoint, SP, and use to calculate a control variable, CV, such as heater power or motor voltage to drive the process toward the setpoint. PID controllers are “tuned” by adjusting three internal constants. Ideally the tuning should allow close control of the process. A properly tuned controller should bring the process up to the desired setpoint quickly and settle smoothly to the desired value without overshoot. A controller that is too aggressively tuned will slew the process too hard and overshoot, then try to bring that process back, undershooting, and continue to oscillate around the setpoint. A controller that is too conservatively tuned will react sluggishly and slowly approach the desired value, perhaps never reaching it.

PID works well for ordinary processes but has a problem controlling processes with a significant delay compared to the process response time constant. An exotic example would be a remotely controlled lunar rover. It may be able to turn in 1 second but nothing will be seen for 3 seconds and any error will take 3 seconds to change. Imagine a simple earth based direction control where the rover hunts back and forth around the desired direction, tacking one way for 3 seconds and then the other for 3 seconds. If a standard PID controller is tuned conservatively enough to eliminate the hunting it will be very sluggish compared to the potential speed of the overall controlled process. A more familiar example is adjusting a bathroom shower. If it’s too cold you turn down the cold faucet, but nothing happens for few seconds. If you keep turning the cold down while waiting the water will end up too hot. Then you start turning the cold back up and when the water at the shower head hits the right temperature it is already too cold coming up the pipe. The problem here is that the temperature can be changed much faster than you can find out about it. A human quickly hits upon the solution: make a small adjustment, wait a bit, make another small adjustment, wait, and repeat until the temperature is correct.

Modern computerized process control uses strategies such as the Smith predictor which uses a mathematical model of the process to predict in advance what the process will do after the delay or System Inversion which uses a model of both the process and the controller for an improved future prediction. These require a priori mathematical computer models of the process and controller.

Long before such sophistication existed there was a surprisingly robust technique called chopped or pulsed PID. This basically emulates the human shower algorithm by chopping the PID controller on and off repeatedly. This is still useful when a simpler solution is desired or when there is limited knowledge of the process model, as is usually the case.

The PID is first turned on briefly. While ON the PID operates normally, driving the process toward the desired result.

The PID control is then turned off for a time approximating the process delay. While OFF the proportional and derivative terms sample the error normally but have no other effect beyond keeping track of the rate of change. If the integral gain is nonzero, the internal integral term is held unchanged. If the process is integrating such as position control, the control variable is turned off (zeroed) while the PID is off. If the process is a normal lag such as temperature or speed control, the control variable is held unchanged while the PID is off.

This adds two more constants to the existing three for PID. The off time should approximate the delay, longer is more conservative, shorter is more aggressive. An on time less than the process time constant exclusive of delay is more conservative and longer is less conservative. Neither is particularly critical and the control scheme is quite robust. When tuned properly, chopped PID responds and settles much more quickly and stably than standard PID for a process with delay.

Processes that involve pure delay include: fluid flow in pipes where the source is heated or cooled but the pipe outlet temperature is sensed, speed of light delay for control of satellites, pneumatic instrumentation and control systems where small pressure changes have to propagate through long thin tubes, and control over computer networks where there can be significant processing and/or communication delays.

Pruning Loppers

This post addresses pruning loppers that are two or three feet long but also applies somewhat to one hand pruners and pole pruners.

The basic rule for using a lopper is: NEVER twist the lopper. If the lopper does not cleanly cut all the way through a branch and sticks, rotate it back and forth around the branch in the plane of the cut to get it unstuck. It is tempting to give it a little twist to snap off the branch or pry it out — resist that temptation. If not you will often chip the cutting blade and ruin it. The cutting blade of a lopper is very narrow and very hard in order to make it cut easily. It is immensely strong in the direction of the cut but quite brittle against side loads, which is what makes twisting or prying so risky.

There are three basic types of loppers. The first is the anvil style that pinches the branch with a sharp cutter against an anvil jaw with a brass or polymer insert to keep from dulling the cutter. The cutter and anvil are usually straight. The main problem is that if you try to cut a green branch of even moderate size it tends to squirt out of the jaws. These also often take a greater amount of effort than other designs.

The second type is a “Bird’s Head” bypass lopper. In these, the curved cutting blade “bypasses” the fixed blade like a pair of scissors. This usually results in lower cutting effort for a given design. But, the curve of the cutting blade matches the curve of the fixed blade. As a result green branches tend to squirt out of this style too.

The third type is a bypass lopper with a cutting blade shape that is more squared off than that of the fixed blade. This captures the branch to be cut, eliminating any possibility of it squirting out. As a bypass lopper it cuts easily and the captured branch is held in an optimum position for the cut. Several manufacturers make these. The Fiskars PowerGear® and Power-Lever® families are good examples of the type.

A major consideration is replacement parts. The part that generally wears out, even with the best of care, is the cutting blade and a worn or chipped cutter is an exercise in frustration. If your lopper has replacements available they will be much cheaper than buying a new lopper. Some manufacturers sell repair parts on their web sites. As an example, a search for “lopper parts” on the Fiskars web site returns various cutter blades for current and past loppers. (It also lists a number of lower cost loppers that are still in production.) Drilling down into likely pictures and descriptions yields model numbers and reference dimensions so you can be sure you are ordering the right part. A replacement cutter is $8 for a $46 lopper and $4 for a $25 lopper, much better than a whole new lopper from the hardware store. Buy a couple while you’re at it.

454 Casull Penetration

The 454 Casull was originally developed as a high performance hand gun hunting cartridge. With about 50% more energy than a 44 Magnum it has become very popular as a bear defense handgun cartridge. When in bear country, make noise while walking, use your tiny bells, and call out ‘hey bear’ or something periodically – Plan A. Wild animals will often shy away from anything unusual. If you see a bear heading your way with intent, a cloud of bear spray in front of the bear will often discourage it – Plan B. If not, remember, bears kill and eat large animals on a regular basis. That is nature, red in tooth and claw. If you don’t feel like being part of the nature menu right now it’s time for Plan C.

The main problem is that a bear has hundreds of pounds of massive, thick skull, thick fur, tough hide, heavy dense bones, gristle, and muscle protecting its vitals. Ordinary handguns won’t do much to a Brown bear except make it mad. As for all dangerous game, penetration is the most important consideration. A flat meplat or bullet nose helps. In preparation for a Western hiking trip I decided to test various loads both straight on and at a 45° angle to simulate a glancing impact. The target was 1.5” of Purpleheart to simulate a skull or heavy bone, backed up by 6” of spruce in the form of four 2×6’s all held together by staggered 3” deck screws for a total thickness of 7.5”. Purpleheart is the hardest wood I had readily available. It is considerably harder and more crush resistant than Rock Maple, for instance. For the 45° angled shots the slant thickness was 10.5” on the diagonal.

Ruger Super Redhawk, 454 Casull, 7.5” barrel, 21 feet from target
90° penetration	90° retained weight	45° penetration	45° retained weight
Buffalo Bore 7B 300gr JFN (exposed lead nose) 1550 fps
3.7”	284gr	3.0” (a)	288gr
Corbon Hunter 335gr HC (Hard Cast) 1550 fps
4.6”	194gr	4.6”	258gr
Corbon Hunter 325gr FPPN (Flat Point Penetrator) 1550 fps
> 7.5” (b)	325gr	10.1”	325gr
Federal Swift A-Frame (hollow point) 300gr 1520fps
5.0”	268gr	6.7” (c)	279gr

Kimber 1911 45ACP, 5” barrel, 21 feet from target
Remington UMC 230gr FMJ 835fps
2.1”	230gr	1.8” (d)	230gr
Remington Golden Saber +P 185gr JHP 1140fps
3.0”	185gr (e)	2.6”	185gr

Notes:

(a) The corner of the lead tipped JFN apparently caught on the 45° impact. It tumbled sideways and didn’t penetrate as far as the 90° shot.

(b) The 90° Corbon FPPN blew straight through the 7.5″ stack, the only round that did so. Even though the bullet was not recovered there was no jacket or core material in the channel through the wood.

(c) The 90° Federal Swift A-Frame expanded as expected, retaining 89% of its weight. The 45° impact shot collapsed the A-Frame hollow point from the side, causing that round to not expand significantly, to penetrate farther, and to retain more of its weight.

(d) The 45ACP FMJ distorted for the 45° impact and tumbled slightly resulting in less penetration.

(e) Both of the 45ACP Golden Sabers packed Purpleheart into their hollow points and did not expand. They also did not loose any weight. The 45° shot tumbled slightly. I added the 45ACP to illustrate the difference between a personal protection cartridge and a bear cartridge.

Note that the 45° Corbon FPPN penetrated 10.1″. It kept straight all the way and was not diverted or destabilized by the angled impact. This is a hard lead core flat point bullet with a thick jacket that completely covers the core including the base. Here is what one looks like after going through 10.1″ of wood.

Unfortunately it’s not available anymore. If you are looking for this kind of penetration there are some alternatives. Grizzly sells a 300gr 1400fps metal jacket lead core round. These use the Belt Mountain Punch bullets.

Another possibility is the Magtech 260gr 1800fps lead core FMJ Flat.

There are monolithic copper penetrators from manufacturers such as Underwood. As they are less dense than cored bullets, they take up more powder space for a given bullet weight and can’t be loaded to the same energy levels as a lead core bullet.

I’m waiting for someone to make a tungsten cored heavy brass jacketed flat nose penetrator. As tungsten is denser than lead, this would leave even more powder space for a given bullet weight.

One common recommendation for this application is the Hard Cast bullet. Note that these penetrated less than half as deeply as the FPPN with a heavier bullet at the same muzzle velocity. Here’s the 90° HC after 4.6″. Also note that it only retained 58% of its weight.

The Federal Swift A-Frame penetrated deeper than the hard cast, retained over 89% of its weight, and expanded to 0.75″ as recovered.

As it turns out, I have enough Corbon FPPN for all the predatory bears I could conceivably meet so that’s what I’ll be carrying. If I couldn’t use that, I’d either take Federal Swift A-Frames or repeat the test using Magtech FMJ Flat, Grizzly Punch, and the Underwood Penetrators.

Quad stopper knot

This is a stopper knot that is somewhat bulkier than Ashley’s Stopper Knot and is derived from it. Where Ashley’s shows a trefoil pattern when looking down the standing end, this knot has a four-fold pattern around the standing end.

Topologically the knot is a double overhand noose with a tuck back.

It is easiest to tie without the tuck at first. Tighten up the double overhand knot around the standing end by eliminating the A segment. This will bring the B and C legs together with the standing end inside the loop. Snug this up enough that the standing end is no longer free to slide and none of the sub-loops are loose. The tighter this is made, the more secure the finished stopper.

Then, continuing in the same wrap direction around the B segment, tuck the working end through the loop as shown. Pull the standing end and the working end tight to create the four-fold pattern. In addition to being bulkier, if this knot comes loose there is a remaining overhand knot as a backup stopper. This last feature precludes it from being slipped, unlike Ashley’s Stopper Knot

If this knot already exists, please let me know so I can give proper credit.

Old-school combs

A long time ago, when consumer products were made in America, the original ACE combs were ubiquitous. Men and boys carried them. Every barber shop had an ACE comb sales display. James Dean famously used one to comb his hair in Rebel Without a Cause. President John F. Kennedy owned at least one. ACE combs were successful because they were quality products, typical for that age. They were made from a tough, strong, flexible hard rubber with thick end guard tines to protect the teeth. The rough mold parting line around the back and edges was carefully ground off smooth to eliminate the sharp edge. Even the tips of the teeth were smoothed off so as to not damage hair. They could be dropped without damage and tended to last for years. As cheaper imitators appeared, ACE started stamping their products as “Genuine ACE Hard Rubber”.

During the adverse conditions of the 1980’s, one of their competitors bought ACE and that was the end of the original ACE comb. Since the competitor now owned the ACE trademarks, they had legal right to stamp “Genuine ACE Hard Rubber” on their existing combs made out of a more brittle material with thinner guards and an exposed sharp mold line including along the tips of the teeth. These combs broke if you dropped them on their ends but that just meant the customer would buy another.

Many people didn’t notice, but if you cared, it was annoying. If you do care, here are a couple of sources for hand-made, high quality combs, with saw cut teeth to eliminate mold edges between teeth, and polished all over so they have no sharp edges anywhere. They are tough and long lasting.

Speert imports a wide range of private label high quality hand-made Swiss combs for men and women, in pocket, purse, and styling versions. The Speert site also offers a very wide selection of different styles, sizes, and diopters of inexpensive reading glasses.

https://speert.com/combs/

For seriously old-school, Kent has been making the “world’s finest brushes” and combs for over 240 years … since 1777. They produce a range of men’s and women’s hand-made, saw cut, polished combs. You can hear the difference as their combs glide through your hair. The given link is for Great Britain and while they have importers, the home web site is worth visiting. It has a web store and PayPal does the pound/dollar conversion seamlessly.

https://kentbrushes.com/

These are elegant combs for a very reasonable price.

New M1 Garand Ammunition

Do not ever shoot regular 30-06 hunting ammunition in a standard M1 Garand. Commercial 30-06 ammunition is loaded to a much higher pressure than the “Cal .30 Ball M2” that the Garand gas system was designed for and simply will not work. At best, commercial ammo will cause a stuck case and at worst will bend the operating rod and/or break the extractor.

The last volume source for M2 Ball equivalent military surplus ammo was Greek HXP which was happily non-corrosive, unlike WW II and Korea vintage U.S. military surplus.

As surplus HXP started to dry up Federal came out with 30-06 ammunition loaded to Garand specifications. The boxes were printed with a picture of a Garand and the part number had an M1 suffix. Since then two other manufacturers have realized that with 6 million Garands floating around and Fulton Armory making new ones there is a significant market. The three current sources are:

Federal /American Eagle AE3006M1

Sellier & Bellot SB3006M2

Prvi Partizan PP347

A web search will turn up multiple ecommerce sites for each.

If you’ve never shot an M1, don’t pass up an opportunity. There are few firearms as much fun to shoot as the Garand.

Garden hose

Don’t buy garden hoses with aluminum fittings — generally silver colored instead of brass. These fittings will corrode and seize to your hose nozzles, sprinklers, and faucets. They then have to be cut off and generally ruin the mating part. Existing hoses can be salvaged by cutting off the aluminum fittings and installing brass fittings available from any hardware store.

Also, try to avoid aluminum in electrical fittings and switches. The aluminum eventually forms a surface oxide layer that causes open and/or intermittent circuits and, in some cases, fires. Years ago there was a brief effort to use aluminum wire in residential wiring before the fire hazard was recognized. It is hard to avoid aluminum in cheap lamp sockets but the effort will be worth it. As a couple of personal examples: our son kept fighting an intermittent ceiling light — replacing bulbs, switch, and breaker — until I swapped out the old aluminum lamp socket. At another time, my garage door manual button stopped working — the remotes worked fine. This was eventually traced to the use by the manufacturer of an aluminum washer under a terminal riveted to a circuit board. There was no visible corrosion, just an invisible oxide layer that formed under the rivet head. A bit of solder bridging over the washer from the terminal to the board cured the problem.

Aluminum is great for cookware and airplanes. Not so much for water fittings or electrical connections.

P.S. Since I posted this the Chinese have noticed people catching on and they are now coloring their aluminum and zinc hose fittings to look like brass. The solid brass fittings should say so. Any weasel words like brass color, brass filled, or brass plated should raise a red flag. Generally brass fittings are machined compared to plated zinc which is usually molded. Brass is over 3 time heavier than aluminum. You can tell the difference as aluminum just feels lighter. Brass is only 20% heavier than zinc but you can usually tell zinc by the mold marks. If you have a scale you can use it to determine the density (specific gravity), and thus material of a fitting:

Material Specific density g/cc

Aluminum 2.7

Brass 8.5

Steel (stainless) 7.9

Zinc 7.1

Fungus and mildew and mold, oh my!

Each time you take a shower or a hot bath, the air in your bathroom warms up several degrees and its humidity approaches 100% — excellent conditions for growing things. You can see the effect of humidity in the fogged mirrors and the damp feel in the room. To help with this, run your bathroom vent fan for 30 to 45 minutes after bathing with the bathroom door pulled almost closed to keep the damp air in the bathroom until it is exhausted by the vent fan but not completely shut to provide a path for cool dry air drawn from the rest of the house. This will help clear the mirror too. You can get an inexpensive humidity gauge from the hardware store to track the change from high back to normal humidity to know how long to run your fan. If you have screw base vanity lights, going back to incandescents in the bathroom will help too — leave them on with the fan. If you’ve been fighting mold in the bathroom, this will improve the situation.

Integrating Sampler

The standard point or impulse sampler that converts a continuous signal to a discrete data sequence has been well understood since 1924 thanks to Harry Nyquist. It is often assumed that the impulse sampler is the only way to create a discrete sequence. There are other sampling strategies that may have advantages in some applications. Here is an example of one.