Tuesday, February 24, 2009

The Littlest Wing


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It's the one on your engine; the propeller. A lot of us forget that it's a wing, or better yet, a whole kit of them, usually arranged in pairs. (Yes, there are single-bladed props. A tear-drop shaped counter-weight adorns the other side. But except for low Reynold's number events, such as model airplanes, the hoped-for improvement failed to materialize.)

Your propeller converts torque into thrust. It does this by accelerating a slug of air. Air has mass and while it's pretty thin stuff, if you can accelerate it to a significant velocity, that soft summer breeze can become a tornado or hurricane. Unfortunately, with a tractor-type engine installation a good percentage of your airplane is embedded in that tornado. And along about there you remember that Drag increases as the Square of velocity. That means you and your fuselage, with all its lumps and bumps and intersections is a major problem, especially when trying to generate thrust with a Volkswagen engine.

To stop being part of the problem and start being part of the solution you need to do two things. The first is to find a prop that is the best possible match for your power-plant and airframe. The second is to do whatever you can to produce a wide thrust-slug rather than a narrow one.

Solving the first problem is pretty easy, if you got lottsa money. You just keep buying props and test-flying them until your improvement peaks-out and you start going down hill. That's when you glom onto the Last prop you tested and put it back on the nose of your bird.

But you may not be able to do very much about the second part of the problem. The only way to produce a wider thrust slug is to sling a longer propeller. But if your engine doesn't have enough thrust to spin the longer prop, you're stuck. But hang around; there's a couple of things you can do that can be of real benefit.

When selecting a prop most of us track down someone having the same airframe and power-plant and use whatever prop they happen to be using. Sometimes that even works out. But not always. His airframe could be seriously out of trim. Or it could have up to twice the parasitic drag as yours. And if it's a Volkswagen engine, most of them are victims of the Horsepower Myth, which is okay for dune-buggies but hilariously wrong when bolted to the nose of an airplane. Even so, there's no doubt his prop will fly your plane if it manages to fly his, but unless your engines are a good match there's the possibility you've just bought a pig in a poke. And a properly made propeller doesn't come cheap.

Gathering more information about other guy's props & engines is a step in the right direction but the chances are, they did exactly what you are doing, which means you could all be barking up the wrong tree. Don't believe it? Okay. It's your plane and you are the Mechanic in Charge, not only of your plane but of your life. So good luck in the Contest :-)

One thing you've got going for you is the fact that propellers are relatively easy to build, meaning you can roll your own for a fraction of the cost of buying one. And as soon as you finish the first one, you get started on the second, because for your research to be useful you should only change one thing at a time.

Didja get that? You carve yourself a 58x34, balance it to a gnat's ass and go fly. Your test flights follow a carefully worked out routine in which you quantify the propeller's performance in your particular machine by measuring such things as Take-off Run, Time to Climb to 1000 feet, average speed over a known distance and so-forth. While all that's going on you're spending your evenings carving another prop in which you change only ONE of the propeller's four basic characteristics; that is, diameter, pitch, Blade Area, and Blade Area Distribution. (Other factors are: Weight, Stiffness and Airfoil.) And while you're doing all that you may want to look up the recommended propeller for the Continental A-40. Rated at 37.5hp and having a displacement of only 1834cc (sound familiar?) the A-40 was typically between 60" and 68" with a pitch that varied between 37" and 43".

As to the things you can do to improve your engine's torque, one of them is to simply use a longer connecting rod. Here's why: Each time the piston reaches Top- or Bottom-Dead-Center, it reverses direction. Depending on the ratio of rod-length to crankshaft stroke, the piston may literally stop. The crankshaft is still rotating but for a number of degrees the piston is motionless. The longer the connecting rod, the longer the piston will dwell at TDC.

The Static Compression Ratio that you built-in to the engine during its assembly, occurs at TDC. Interestingly enough, Ignition has already been initiated -- in fact, the fuel-air charge was ignited quite some time before the piston reached TDC. This reflects the fact that the process of ignition requires a finite amount of time. Not that it's a slow-poke. Even in the largest Big-Bore Stroker combustion only takes a couple of milliseconds. What's interesting is that except for some minor variations having to do with ambient temperature and air density, the process of combustion is virtually independent of the engine's rpm. That means, the faster the engine is running, the earlier we need to light the fire. Even so, in the typical dune-buggy engine the Combustion Space is constantly increasing. Indeed, this is what you want when the engine is bolted to a box full of gears. But this is NOT what you want when the engine is bolted to a fan!

The greater the dwell at TDC, the more time there will be for the process of combustion to occur when the fuel-air charge is at it's maximum compression ratio. With the piston virtually motionless combustion will produce it's maximum temperature, which in turn yields the maximum possible pressure. And it is that pressure which appears in the crankshaft as TORQUE.

To achieve this minor miracle we retain the stock cam shaft and retard it by as much as seven degrees, although -4 is more typical. This causes our maximum torque to appear between 2500 and 2800 rpm, which makes it ideal for slinging a prop. Dune-buggy engines, typically running above 3000 rpm, produce a narrow, high-velocity thrust slug, which works okay in a cleaner airframe. But if you're driving a tumble-weed you're going to need a wide, low-velocity thrust slug. And the only way to get it is to move your engine's torque-band to a lower rpm.

That covers the engine. And should have made it clear that there is an enormous range of differences between supposedly 'identical' engines. Now let's look at the prop itself. I've included a couple of illustrations just to liven things up. The image at the start of this article is of a template used to test the Upper Camber of the prop's airfoil. But don't pay any attention to the dimensions; this template happens to be for a prop only 42 inches in diameter, meant to be used with a 6hp single-cylinder engine.

You don't start 'trying' the templates until you are almost finished fabricating the prop. But such trials are of critical importance to insure each blade of the prop is the closest possible match to the other.

Traditionally airfoil templates were made of brass shim stock, having a thickness of .006" to .010". Nowadays, lo-buck builders use the aluminum from a beer can. If building just a single propeller, you can even get by using paper, such as the cover of a file folder.

Since our prop is going to be operating well below the critical tip-speed of 880 feet per second we can use one of the traditional airfoils such as the Clark-Y, a very good choice for a wooden prop, thanks to its flat bottom and good thickness ratio, which is about 12%. (The Clark-Y, which was used on Lindbergh's 'NYP' and the USA-B, (US Army, version B) which was used on the Piper 'Cub', owe their existence to Col. Virginus E. Clark, one of America's first truly competent aerodynamicists. Colonel Clark (U.S. Army) was a real genius. His research in molded propellers lead to the invention of the 'Duramold' process for producing laminated wooden skins that had significant advantages over riveted metal structures. The Duramold process is what made the HK-1 possible. [HK-1 or 'Hughes-Kaiser #1' more commonly known as the 'Hercules' or 'The Spruce Goose,' even though most of the structure is Duramolded birch rather than spruce.])

The second illustration is of the coordinates for the Clark-Y, which I don't believe is included in Abbott's 'Theory of Wing Sections.'

When I can find the time I will include drawings of the airfoil templates we will need to fabricate propellers for the Chugger. The airfoils will be drawn full-scale (ie, 1:1) allowing them to be used as patterns. Printed by an accurate printer, the patterns will be glued to the metal templates then scored with a scalpel or razor-knife.

Interestingly enough, when working with sheet-metal thinner than about .025" you will find that scoring works better than cutting. The scored metal is simply flexed back & forth a few times, which causes it to fatigue along the scored line and fracture. The tricky bit is in how you make that first all-important score-mark and the secret is, for the thinner the metal, the lighter the amount of pressure. Indeed, for beer-can stock (or .006" brass shim-stock) you don''t us any pressure at all (!) While this would appear to violate common-sense, it turns out that if you use any pressure you will cause the shim-stock to deform long before any scoring takes place, and that the now-deformed shim-stock refuses to fracture along the scored mark.

-R.S.Hoover

Sunday, February 22, 2009

Reuben Sandwich

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Sunday's peaceful decline is marked by the horn of a distant train, clearly heard in the still air.

The sky is overcast, what warmth there was is gently trapped beneath the gray blanket, without sound or movement. A candle on the patio table burns undisturbed, it's flame as stable as a painting.

It is my stepson's birthday, he is now forty-something and rather surprised by how quickly this birthday has followed his last. We celebrate the event with Reuben sandwiches, Brownies and good cheer, the grand-kids rocketing around the house like elemental particles. A baryon zips past, narrowly missing a lepton as a meson comes through, hooting like the train. The meson has lost a tooth, proudly displays the gap, sign of approaching maturity and two-bits from the Tooth Fairy.

A Reuben sandwich is a bit of a mess, one of those things so messy that you know it has to taste good even if you've never tried one before. It starts with Rye bread, which gets lightly buttered on what will become the outside. Suitably greased, the slices of bread are spread apart and a dripping tablespoonful of my Secret Sauce gets slopped onto each slice, spread around by the spoon and allowed to soak in. The Secret Sauce begins as something tomatoey... tomato sauce will do but so will ketchup. I'm making six sandwiches so I'll need a bit more than a cup of sauce and begin by schlurping ketchup into a small bowl. Then comes Horseradish... the Good Stuff that stops your breath and brings tears to your eyes. Not too much but you need to establish Who is In Charge. The sauce gets a shot of mustard then a shot of mayonnaise, something of a surprise but a necessary evil. Dash of garlic powder and lots of stirring then two heaping tablespoonfuls of dill pickle relish. Schlop --- smear -- swipe. If you take more than a minute you've missed the whole point of a Do-It-Yourself Reuben.

Onion, in thin slices. This calls for a sharp knife. The slices fall away from the blade, already coming apart, which is okay, because you adorn the sauce with two or three slices broken down to their individual rings; a Torpedo Net of onion rings.

After the onion comes the sauerkraut which has been simmering on the stove. You can spice it up if you like. This one wasn't. The heat is important, part of the technique needed to produce a proper Reuben.

Swiss cheese, sliced stinking from a brick of holes comes next, followed by the meat. Today I'm using canned corned beef but you can use pastrami or various kinds of sausage, even dried beef, partially re-constituted by heating it amidst the sauerkraut. Bully beef is okay; it makes for less of a chore when accumulating the ingredients. Since bully beef is tapered by the can you need to plan ahead, topreventrunning out of room.

A cast iron skillet has been heating on the stove. Very low heat but fifteen or twenty minutes. A lid, also warm, is near at hand. The assembled sandwich is flipped into the hot skillet, causing the butter to sizzle, telling you if it's too hot or too cold.

The tricky bit here is to flip it into the skillet meat-side-down. Now pop on the lid and start assembling another. Why meat-side-down? Because you want the meat to be hot and the cheese to melt but you don't want to turn the onion into a soggy mess.

Cooking the Reuben cools the skillet so that when it's ready to be flipped, the onion-side goes down onto a relatively cool skillet. There is still a bit of a sizzle but now it's more like a hiss. The lid goes on. Nothing is getting cooked except the bread, which is being toasted, which is why you keep an ear out as you assemble the next customer. When the cool side of the sandwich is toasted you scoop it up with a spatula of suitable length and plock it onto a plate with crunchy dill pickle and a slab of potato salad if you've got it. If the sandwich is destined for a woman it gets sliced on the diagonal, which removes the threat of squeezing goo all over that pretty blouse. Guys being guys just wrap a large napkin around the thing and attack.

If there are vegens 'round the table, leave out the meat and use a French knife to give the onion rings a couple of chops. Cooked without meat, the onions will lose their crunch and become difficult to manage.

Reuben's have a habit of vanishing. People who are sure they can't finish one end up wandering around with an empty plate in hand and a wistful expression.

Use a LOW heat. Allow time to work in your favor.

If you're feeding kids as well as adults, mix two sauces, one having less horseradish. It's a big sandwich; serve them halves.

DON'T mix up things ahead of time. The sauce does not improve with age.

If using canned corned beef, it should be at room temperature.

Everyone's recipe for a Reuben sandwich is different, which is as it should be.

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I'm still trying to regain muscle mass. Reubens are one way of doing that but they're a lot of trouble to prepare -- you need a good excuse -- just having cancer isn't good enough. Turning Forty-Something justifies Reubens.

The joy of cooking is not in your ability to produce a tasty meal, it is in the expressions of the people eating what you have prepared. After eating a Reuben, they smile. Their plates are empty. It has been a memorable experience, for them as well as me.

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Cooking with cast iron is a bit different in that the skillet never goes into the dish washing machine. Cast iron pots and pans are washed by hand but it is more scraping than washing. Once all of the residue has been removed they are put over a low flame and fed a small amont of oil. We usta use lard but that meat having to wash the skillet before using it as well as after. Nowadays you'll probably use rape seed oil (ie, 'canola' oil). Let it get hot in the skillet, Dutch oven or what-have-you then wipe it dry and put it away. The next time you use it, give it a gentle pre-heat with a shot of oil and wipe it out. In many ways a cast iron skillet is similar to a cast iron griddle.

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A good Sunday. I hope there will be plenty more.

-Bob

Saturday, February 21, 2009

Cancer Report 05 -- Email Woes

I'm still alive. But 谷歌 has 86'd my email account, kicking messages back to the sender, causing many of them to think dire thots. So try this one:

veeduber@chuggers.net

My isp is a company NAMED 'ISP.' Cute name but a bad company. They made some kind of a deal with Gmail (eh?) which passes all of my messages to 谷歌... who decides to shut down my account. Why? I've no idea. And I suspect 谷歌 doesn't either. But with the account shut down, any message sent to veeduber@isp.com would be rejected, causing the sender to think I'd died. Or something.

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It is 104' around our patio. And 294' from the kitchen door, down the front drive then up to where I park the bus, around the bus and down the back drive to the patio gate. Then thru the gate and back to the kitchen door. Two hundred and ninety-four feet.

Good exercise. Something to do, what with no emails to fill my morning.

The pain is almost entirely gone. That worries me a bit, wondering if something is about to break loose. Take the 'long' walk; try not to think about it.

5280 feet equals one mile. 1320 feet equals a quarter of a mile. Four-point-four times around the long walk is a quarter of a mile. I'm now strong enough to walk a quarter of a mile without falling on my face.

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An Amateur Radio License is only good for ten years, after which you're expected to renew the thing. Mine expired on the 13th of February so I went to the FCC's web site, found out what I had to do to renew my license, and did it. Today a shiny new license arrived from the FCC. It's just a computer-printed page but one suitable for framing. There is also a smaller version you can cut out and tuck in your wallet although I'm not too sure why. I've never had anyone ask to see my ham radio license. Nor my pilot's license.

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It has been nine months since Alberto Bessudo told me I had cancer. I'm not in the hospital and all things considered, I'm not feeling too bad.

-Robert S. Hoover
-21 February 2009

Friday, February 6, 2009

ENGINE MOUNT


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Engine Mount
(All photos courtesy of Mike Sample)

When you install the propeller on the clutch-end of the crankshaft it solves a lot of problems, such as having the nose of the crankshaft break off, taking your propeller with it. But like the man said, there's no such thing as a free lunch. Put the prop on the clutch-end of the crankshaft and you have effectively reversed its direction of rotation. That is, if you are sitting in the cockpit of your VW powered Dream Machine and you've mounted the prop on the fan-pulley hub, the propeller is rotating anti-clockwise. But if you have installed your propeller on the clutch-end of the crankshaft, to someone sitting in the cockpit the prop will be rotating in a clockwise direction. Kinda like it shows in the picture at the top of this article.

Another part of your No Free Lunch is having to carve a propeller for that direction of rotation. (Not to worry. I'll post a big, fat article showing you how to carve such a beasty.) This article will give you some idea of what you will need as an engine mount. The tubing is 3/4" x .049" The method of engine mounting also includes some means of shock absorbtion or vibration damping. In this case, the shock mounts are pre-molded rubber mounts usually sold as 'Lord' mounts. I'll include a drawing showing how to make them, as well as another type which uses simple rubber pucks. (The rubber pucks in Lord mounts are tapered on one end.)

As you can see in the photos, the engine mount is triangulated, taking advantage of the threaded busses found on all 1971 and later VW crankcases.

As you can see, a bed-type mount is used on the FRONT/LOWER mounting bolts.

(When dealing with Volkswagens everything is always called out relative to the vehicle. The forward-most crankshaft bearing -- the one nearest the flywheel -- is the #1 bearing and so forth. This is the convention used in more than twenty million Volkswagen engines over the past seventy-five years and I think you'll have to admit it would be rather silly to try and change things now :-)

You may also use individual mounts at this point, the crankcase providing more than enough strength. But the bed-type mount -- something to which you can weld a mounting tab -- offers a number of advantages when installing your oil cooler, carb-heat box and so forth.

Up to this point the mount is the Plain Vanilla version. The following photos show the mount modified to accommodate various cooling and exhaust systems.




Notice that the struts from the upper attachment points has been 'cranked' so as to allow more space under the cylinder barrels. This is to allow the cooling shroud to wrap around the cylinders and heads.

In this arrangement the dynamo is mounted directly to the crankshaft, eliminating the need for brackets, pulleys, vee-belts an so on. The goal here is to provide an engine installation designed for non-mechanics.

If a starter is required, it is installed on the top of the crankcase. It's ring-gear attaches to the crankshaft between the engine and the propeller hub. This will probably require a blister on most cowlings.

On some airframes the location of the gascolator will have to be changed to allow an unobstructed path for the LOWER/REAR threaded bosses. These were introduced by Volkswagen in 1969 to provide a hard-point for installation of a rear engine mount in the Transporter.

The LOWER/REAR mounting bosses are not symmetrical relative to the parting line of the crankcase, something you want to keep in mind when cutting your tubing.

As on all of the later-model engines, the threaded bosses are fitted with Heli-coil type thread inserts. The engine mount is attached to the crankcase with high-strength metric fasteners having drilled heads to accept safety wire.

The last two photos show the engine mount installed on an airframe (ie, look for the yellow paint). From this point on the installation becomes airframe-specific.




-R.S.Hoover

Tuesday, February 3, 2009

Club Med

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Nope; no pictures. It isn't that kind of 'med.' This kind does chelation therapy for people without kidneys, and feeds cancer medicine to people like me.

I started going to Club Med in July, 2008, when I came home from the hospital. I was the newbie of course. Room full of geezers looking at me without looking, if you know what I mean. Geezers are good at it. Kids aren't. Little kid, say, six or less, will run right up to you, ask if you have cancer then tell you their mother's life story. How you handle it has a lot to do with how the Club members handle you.

People don't die at Club Med. They do that at home, or in the hospital. But before they do, they stop coming to Club Med. That's the part you notice. A different face plugged into Machine #3. Oddly enough, you never ask. You already know. And if you were close, you might reach for your cell phone. Or ask one of the nurses, to find out if you've still got time to send flowers. Or whatever.

Whatever else it is, Club Med is a business. It's there to make someone a profit and you have to remember that the profit comes first. No profit, no Club; it is not a charity. But right now -- and for the foreseeable future, business is good. Perhaps a little too good, from an humanitarian point of view. And while you may not know it, there's a Club Med near you! No, they don't want anything from you (well... mebbe not. I don't have a lot of experience with Club Med's. But most don't want anything from you... mebbe kid's toys at Christmas but they probably don't have to ask for stuff like that).

There's only two ways out of Club Med. You gain weight, grow hair, start to smile more often, pay more attention to how you dress. Then you vanish.

Or... you start turning kinda gray. Not your hair, your skin; all of you. You lose weight. Your smile becomes more hesitant, often fails all together, as if to say 'What the hell are you looking at! Don't you realize I'm dying here?) Well... yes, we do. And believe it or not, we'll miss you. But it's a path we all are one day going to travel, the only difference is that Club Med is a kind of short-cut.

Ol' Ironsides comes in both flavors, getting better and getting worse. They are typically 12V-Powered-Loners who arrive in their battery-powered wheel chair, don't need any help, thanks. And really don't. If they are male you can imagine them pumping iron down at the beach, soaking up some rays, playing catch with the kids. I see them out at the shooting range, raising hell with a hand-gun, which is usually somewhere on their person 7/24 because some folks think Ol' Ironsiders are an easy touch. They're not. Going armed doesn't mean they're looking for trouble. In fact, it usually means exactly the opposite.

But most Club Med members come in pairs, the patient plus... someone. 'Care Giver,' whateverthehell that means. My wife comes with me. Going by myself will mean I'm getting better. Stay tuned!

I did Club Med today to pick-up a Zometa refill.(*) I'm exercising more which means I'm hurting more and Zometa seems to help. Another newbie over in Chleation Row and for the life of me, I can't remember who was there just a week ago. Someone notices me looking and fills me in. Others join the conversation, people closer to him. Sudden. Some sort of stroke. I sense a feeling of relief. About the best some have to hope for is to die in their sleep.

Club Med.. It's not for the weak of heart.

-R.S.Hoover

(*) -- Part of my medication regimen is a periodic Zometa I.V.

Monday, February 2, 2009

THINKING SMALL


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Need a drop of oil?

Sure you do. Everybody does, now & then.

Pocket-knife. Part of my Uniform, issued to me by the Navy in June of 1956. Good knife. The steel holds an edge. The blades pivot on either end. Keep the big blade 'knife-sharp,' the little blade 'razor-sharp.' (It has to do with the cross-sectional shape of the blade. Razor-sharp is a temporary thing; it dulls in a hurry; needs to be stropped back to sharpness. Knife-sharp isn't as sharp as a razor but it keeps it's edge longer. When it gets dull you sharpen it with a whetstone. Just a few strokes.

Oil a micrometer?!! Well... yeah, I guess so. After all, it's just a 40tpi thread inside a graduated barrel. But it doesn't need to be oiled very often; mebbe once every five years if you use it a lot.

Fan with Oilite bearings? Sure! Sez so, right there... little hole 'OIL.' And you are the Mechanic in Charge.

When it comes to lube-jobs we have a tendency to ignore the little jobs, like all those kitchen appliances you and your wife depend upon. But if you read the manuals you'll generally find some mention of lubrication, although many will want you to take it to a 'qualified repairman.' Which is you, by the way. Indeed, the main difference between a modern 'Lubricated for Life' partis that they make no provision for periodic lubrication. Most of today's cars are like that, with many key components being 'lubricated for life. But it turns out that their definition of 'life' can be as little as sixty-thousand miles, at which point you will be forced to buy & install a new part.

Kitchen drawers & cabinets? Yep. Tiny drop of oil every five years or so. Along with your home's door hinges, door knobs, latches, locks and so forth. But not always oil. Some call for a whiff of powdered graphite, like the door lock on your car or truck.

Sewing machine requires periodic maintenance, just like your car, boat or plane. And they'll usually tell you what oil to use.

Funny thing about oil: Provide something with a hole that sez 'OIL' and the odds are, it will get too much oil. The oil gets past the seals; gets into the motor which slings it all around. The oil collects fine-textured debris which eventually blocks the vents needed to allow the motor to cool properly. So they seal-up the oil holes, leaving you to go around, put your hand on the motor or gear-case to estimate the temperature. If you can put your hand on it, it doesn't need any oil. But if you can't touch it with your bare hand, then there's a good chance it needs to have it's lubrication replaced.'

Good motors, the sort of thing you find on ammo hoists and other military equipment, have very specific instructions with regard to lubrication. They spell out when the thing is to be dismantled and cleaned, what lubricants should be used and how much.

The point most often overlooked with regard to such lubrication chores is that the item to be lubricated must also be cleaned occasionally.

Another point often overlooked by the home mechanic is that selling light-grade oil in small quantities often inflates the price to over two hundred dollars per quart. No, that isn't a typo. See the half-ounce tube of Singer Sewing Machine oil? It's list price is $3.19.

This sort of thing reflects modern-day corporate thinking, in which every possible effort is made to screw the customer. Proof of this is seen in the first photo which includes a 4 ounce can of Singer Sewing Machine oil for thirty cents ( ie, $9.60 per quart ).

Your best defense against this sort of thing is to buy such lubricants in larger quantities, such as quarts or gallons and to provide your own dispenser... or to simply refill the regular dispenser, such as the cans shown in the top photo. WD-40 and kerosene are available in one and five gallon containers and a flit-gun provides all the atomizing I require. The same is true for light-weight oils which are usually available from distributors of hydraulic lifts and elevators.

The best example of this that I can think of is that I can think of involves my Zippo cigarette lighter, variously repaired (at no cost) by the Zippo company three times since 1958. Lighter fluid is naptha. Purchased by the gallon, is ( or rather, was, the last time I bought some ) about $3 per gallon while lighter fluid cost about $0.75 for a 4.5 oz can. That's about $21.00 per gallon. ( And the price has since gone outta sight ).

-R.S.Hoover
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