Friday, December 1, 2006

AV - Flying On The Cheap -- Hose Fittings


.
A fellow homebuilder spotted a female air-hose quick-connect fitting on a fuel I'd just finished sloshing (riveted aluminum tank) and told me he hadn't bothered to pressure-test his tank since it was gravity feed and he figured just filling it up was enough of a test. He went on to say that it hadn't leaked so I guess he was right.

I didn't bother to tell him the fitting wasn't there for the purpose of pressure-testing.

Heat the end of your 2-ply fuel line in oil, you can push it onto an air-hose quick-connect fitting. Safety wire or even a hose-clamp for the rich bastards, you got yourself a fuel-line fitting.

Why? Because it costs less than half a buck and works perfectly well. Gettem from Harbor Freight. Two male fittings, one female and a quick-connect coupler. Wait for the sale, you can pick up the kit for $1.39 (otherwise, it's about $3).

No big deal? Maybe not, if you got lots of money to waste.

Personally, I prefer aluminum tubing for fuel, vent & vacuum lines. Old habits, etc. But if you have to squeeze ever nickle until the buffalo farts, hose is makes pretty good sense. When properly installed & supported, frequently inspected and periodically replaced, hose can be made to serve for the plumbing in a minimum-cost, VW-powered puddle jumper. Assuming you've got a drawer full of fittings.

Back around Thanksgiving I reached in the drawer and came up empty and the local auto-parts place wanted something like three bucks for one 1/4"-NPT to hose fitting, I needed four of them and they only had the one in stock. I could turn them up on the lathe faster than they could order them but on the way home I stopped by the Harbor Freight store in Escondido and they had a whole bin of air-hose fittings on sale. Bought a bunch. Worked fine.

They're cast brass rather than extruded. And only come in straights, male or female. But a gravity-feed system doesn't see any pressure to speak of and space isn't at a premium in this particular airframe so straight works okay.

Yeah, it's outside the box. No, it isn't unsafe; not when properly installed. And the proof is no farther away than testing it for yourself.

-R.S.Hoover

AV - ...but I don't have a LATHE

.

"...but I don't have a lathe."

Sound familiar? The truth is, you probably have any number of things around your shop that can serve as a lathe.

In a lathe, the work rotates against the cutting tool. ( In a milling machine, it's the cutting tool that rotates against the work.) The main purpose of a lathe is to produce a circular part, which is achieved by pressing the cutting tool against the work-piece as it rotates. Anything that achieves that goal with sufficient accuracy for the task at hand will allow you to do the job.

The most common thing used to rotate the work is the ubiquitous quarter-inch drill-motor. A drill press works even better. And the cutting tool may be anything from a hand-held file to an angle-head grinder fitted with a flapper wheel; even a portable belt sander can be your 'cutting tool.'

"Tried that," they usually say. "Didn't work." Odds are, they didn't try hard enough :-)

The trick to holding the work-piece in a drill-chuck is to use a coupling nut. Put the coupling nut into the chuck and tighten it evenly, taking the slack out of all three jaws. (Just put the chuck key in each hole in turn, taking out any slack. If you tighten a Jacob's chuck at only one point there will always be some slack in the other two positions, usually enough so that whatever is chucked will not run true.)

The centroid of the work-piece is then drilled to accommodate a bolt that matches the coupling nut. The standard 1/4-20 will serve for most work but coupling nuts come in all sizes. To keep the work-piece from spinning on the bolt you may use a lock washer.

When using a hand-held tool as your cutter, be it a file or even a belt-sander, the trick to producing a true edge is to use your eye to align the opposite edge of the work with a known-true reference, such as the string of a plumb-bob. Or the blade of a protractor, if you're creating an angle. Any deviation is instantly apparent and just as quickly corrected.

In most drill presses the chuck is attached to the quill with a simple taper. A taper has the advantage of providing a virtually error-free alignment but has the disadvantage of not being able to withstand much of a side-load. Even a 3M fiber-wheel (used for dressing aluminum edges) may cause the chuck to leap off those cheap Chinese drill presses. To prevent that from happening when using the drill press as a lathe, the head of the bolt you use to secure the work-piece to the coupling nut should be drilled in a cone large enough to accept a small ball bearing. Simply trapping the ball between the drill-table and the bolt will provide enough axial pressure to prevent the chuck from coming adrift.

- - - - - - - - - - -

There are endless elaborations to this theme but the basic idea is that you probably do have a lathe, if you put a bit of thought into it. Although crude in appearance such jury-rigged tools are accurate enough to allow turning down a piece of 4130 tubing to fit a standard bearing, make circular flanging dies of any diameter and even create the plug for a 10 x 12 inch spinner for your propeller hub.

-R.S.Hoover

AV - Gift Horse


.
Mess around with airplanes long enough, you'll get calls from strangers asking for stuff. Hunk of urethane foam. Piece of tubing of a particular diameter & wall-thickness. Quarter sheet of .012 2024-T3. Various tools...

I no longer lend tools since they have a habit of not coming back but if I've got it to spare I usually try to help out with materials, like that twelve-thou aluminum.

So the guy shows up and he's brought his own personal Inspector, one of those Designee-types slightly older than God and equally omnipotent. I go to digging under one of the outside benches where there's a couple sheets of .012 rolled up & sealed and the Great Inspector stands there and gives us a lecture on how I've over-driven the rivets in the structure laying on the table. The shop heads are okay he sez but I've been reverse-setting the things (according to him) and the factory head is all flattened out.

Which isn't too surprising because they happened to AN442's. And are set strictly to spec.

I gave the guy the metal but told him if he needed anything else to leave his idiot 'inspector' at home. I don't have any time for fools.

-------------------------------------------------------------

AN442's are flat head aluminum rivets. Not countersunk rivets; real flat-heads, like you'd find on an old fashioned cow bell or milk pail.

When you get most of your fasteners as new-surplus you're liable to run into just about anything. Nowadays, most homebuilders (and homebuilt 'inspectors') are only familiar with AN470 'Universal Head' rivets and countersunk head rivets having a 100 degree angle (ie, AN426's). But there's a few hundred (!) other types of aluminum rivets out there and if you've got the tools and sets to use them, there's no reason not to. Indeed, you'll see a lot of round head rivets (AN430) on vintage airframes, especially war birds, and it seems only fair to use the same fasteners when making a repair.

You can still buy sets for round-head and brazier-head rivets. When fabricating interior components such as bulkheads or the firewall, where aerodynamic drag isn't a factor, there's no reason not to use AN430's. And if you happen to be making a thermostatically controlled vent for a greenhouse, it's the perfect opportunity to use-up some of those Reynold's 6061 AN442's that have been taking up shelf space since Jonah was a seaman-deuce. But don't let one of them Designees see you doing it or the greenhouse will never get off the ground.

-R.S.Hoover

VW - Boot Camp

.

No, we're not at war, but we've definitely got a fight on our hands when it comes to CV joints. And since you only need to do your boots every 30,000 miles you're not likely to become proficient at it. So here's a little refresher course. But before we start, I want to preach a little pre-sermonette at you.

When you do periodic maintenance on CV joints you must insure the parts are not thrown out of balance. Before taking anything apart, make orientation marks that will allow you to reassemble the parts in exactly the same relationship as they were originally installed. That includes not only the CV joints to the stub axles and tranny, and the CV joints to the axles, but even the balls within the CV joints; they should go back into their same races and the same opening in the cage. John Muir failed to make this point in his otherwise excellent discourse on CV joints and that failure had expensive consequences for lots of VW owners who reassembled them in a willy-nilly fashion and even used hose clamps and the like when installing their boots. The axles rotate at about a thousand rpm at freeway speed. The imbalance created by the screw-type clamps causes premature failure of the rear wheel and differential bearings. As with pounding on the wheel nuts with a hammer & chisel, this is another instance where the earnest efforts of St. Muir did far more harm than good.

Back to Boots

The boots are those rubber bellows around your axles. Swing-arm trannys have two of them, one on each side. Later model 4-joint trannys use four of them, one on each end of each axle. (Both early and late VW's have independent rear suspension systems. The term 'IRS' as applied to late-model trannys was invented by magazine editors [who seldom get things right anyway].)

On early swing-axle trannys there is no periodic maintenance requirement for the boots, you simply check them now and then, replacing them if they become torn (as they all will) or leak excessively. On swing-axle trannys the axle runs in a housing; the boot flexes with the rear suspension but does not rotate, permitting the use of split-type boots as replacements. Since the boots serve only as an oil seal they should be replaced if they are no longer doing their job.

On late model 4-joint trannys the boots act as grease seals for the Constant Velocity (CV) joints and rotate with the axles. In order to lubricate the CV joints you must remove the boots. Because of the unbalanced nature of split-type boots they can not be used as replacements, you must dismantle the CV joint and press the axle out of the joint in order to slide the new boot onto the axle (and the old boot off).

Read St. Muir

John Muir's 'Idiot' book provides the best available step-by-step procedure for the removal, lubrication, and replacement of your CV joints. If you don't hold a copy of 'How to Keep Your Volkswagen Alive...' go buy one. Now. (I'll wait until you get back.) But you should also have the Haynes VW manual (#159) which is superior to all others thanks to its lavish use of illustrations. They do an especially good job describing CV joint maintenance.

Proper Parts and Tools

About three weeks ago you should have ordered your boot kits. A 'boot kit' consists of a replacement boot, eight (or four, depending on model year) new bolts, a new splined washer (needed to provide the proper pre-loading during reassembly), a new circlip, 90 grams of CV joint lubricant, and a new boot clamp. The best kits are from Meistersatz, the German company that supplies VW with your original boots.

If you've never done your boots, order four kits and do all of your CV's. It will provide you with a base-line for doing them in the future. You'll also need about twice as much lubricant than is supplied with the kits; pick it up locally. If some of your old boots are still in good shape, clean them and hold them as emergency spares. You will need to carry a spare tube of CV lube but you can make a nicely balanced emergency boot-clamp using wire. (The trick is to make two wrappings, 180 degrees apart, having the same number of twists so as to maintain proper balance. Use stainless steel aircraft-type safety wire if you can get it, stainless steel MIG wire if you can't, bailing wire as a last resort.)

Over the years Volkswagen used different numbers of bolts on their CV joints, and different sizes, too. The bolts are socket- head types using EITHER Allen-head sockets or the splined 12- point '3-squares' pattern (ie, three squares superimposed, each rotated 30 degrees from the other). Volkswagen has used both 6mm and 8mm sizes.

Since the Allen-head type may be used as replacements for the splined type, and since the splined type came in two sizes, and since some prior owner may have serviced one of the CV's but not the others, one of your first chores will be to determine what type of bolts are dealing with. Raise the vehicle, support on jack-stands, crawl under and scrub the heads of the CV joint bolts clean using a toothbrush and solvent. Be prepared to spend up to one hour on this job. You must clean the socket of every bolt and there are 24 of those puppies. If you fail to get the sockets clean the bit won't seat properly and you'll strip the socket, leaving you the lovely task of worrying the bolt loose using vise-grips. And don't assume all of the bolts are the same! Scrub them all; you may find one of your CV's wearing bolts different from the others.

Alas, Allen-head wrenches cannot be used on the 12-point splined bolts, nor visa-versa; you'll only ruin the bolt if you try. The majority of Volkswagen CV joints use the 12-point splined socket head bolts of the 8mm (socket-head) size. J. C. Whitney sells a four-piece set of such bits in 6, 8, 10 and 12mm for about $10 (p/n 14 xx 1662-P). Unfortunately, the bits are American-made, their shanks are 5/16" for the two smaller sizes, 1/2" for the larger (that is, the bits will fit sockets of those sizes). The 1/2" isn't a problem; you can use it in a 13mm socket, but the 5/16" size -- including the 8mm bit, the one most of us will use, is something of a poser since it's too large to fit an 8mm socket, too small for 9mm. I'm lucky to have a full set of metric and SAE sockets but if all of your tools are metric you will have to buy a cheap set of 3/8" drive SAE sockets in order to use the 8mm bit. The best solution is to find the bits already mounted in sockets (they come that way) but I don't know of a mail-order source. Indeed, my frequent citing of J.C.Whitney parts and tools is not from any admiration of their quality, service or price, but only due to their global availability.

(One word of caution: '3-square' pattern socket head bolts used on Volkswagens are not Torqx-bolts. Torqx is a 2-triangle pattern (ie, six points, rather than 12). The typical hardware store clerk doesn't know the difference, apparently defeated by an number greater than five. 3-square pattern socket-head bolts are found mostly on European vehicles, Torqx on American and Japanese. Brazilian vehicles use a pattern that is perfectly round :-)

As a personal note, I've made most of the Allen-head and splined tools I use by cutting off the bit and brazing it into a suitable socket, usually something picked up at a swap meet. Such bits are made of hardened steel, they will dull a file and strip the teeth from a hacksaw. The proper way to cut them is to use an abrasive cut-off wheel or a diamond saw. Cut-off wheels work best; the harder the material, the faster they cut.

The final tool you must have is an accurate torque wrench, and this is one of those cases where a clicker is superior to the torsion beam type. Working overhead, under the vehicle, it is very difficult to position yourself so as to read a beam-type torque wrench without introducing parallax, whereas the clicker can be read upside-down, behind your back and in the dark, if you wish.

Your Bentley manual fails to include the proper torque values for the two sizes of bolt used on the CV joints. Most of us have the 8mm bolt; they should be torqued to 25 ft/lbs, the 6mm to 31 ft/lbs. (That's right; 25 for the 8mm, 31 for the 6mm.) Run them up snug, then torque in a cross-pattern for the 6mm, a star for the 8mm (If you've got the 6mm bolts there should be only four of them.)

Hydraulics vs Hammers

The Bentley manual shows uniformed Volkswagen mechanics using the standard-issue Volkswagen hydraulic press to push the axle out of the CV joint (and pressing the CV back onto the axle when the job is done, no doubt marching in lock-step between times). St. Muir sez use hydraulics if you got'em but a hammer will work too. In this case, I agree with him.

The Haynes manual shows the mechanic pushing the axle out of the CV joint with his thumbs. This is the most likely case for disassembly since the axle is meant to be a tight sliding fit in the CV joint, rather than an interference-fit. If you encounter a sticky one, inspect the upper-most portion of the splines (above the groove for the locking ring). It's most likely that you will find some minor burrs on these splines. Stone them away and try again. If you must use hammers and drifts, use proper ones; lead or brass for the hammers, bronze or brass for the drifts. On reassembly the internally splined cup-washer must be compressed, a task most easily accomplished with a hydraulic press.

Failure to maintain the original spline/tooth orientation often causes the axles to bind in the CV joint hub during reassembly. Take it apart, verify the alignment and try again.

Sermonette

The Bentley manual neglects the CV joints, offering neither a nominal lubrication interval nor torque values. The Haynes manual sez to inspect them but to leave them alone unless the boots are torn or leaking. That is as invalid as the Bentley approach; by the time the things are torn or leaking you'll be faced with the expensive replacement of the CV joint rather than its messy but necessary lubrication. (The Haynes method is correct for the older swing-axle trannys and may well be a typographical blunder, albeit one of major proportions.) John Muir sez keep your CV's greasy and they'll last a long time. Despite his many errors and omissions, John Muir's approach is the most correct of all, at least when it comes to CV's.

Each of the manuals cited above claims a certain degree of expertise yet each contains many errors, some minor, some catastrophic. (The Chilton manuals are not worthy of mention.) Your wisest course is to gather as much information about your vehicle as you are able, and from as many diverse sources as possible -- and then to think for yourself.

-Bob

VW - Brake Grease

.

In 1957 I had a part-time job doing brake jobs at Pep Boys in Hayward, California. It was an after-hours sort of thing, six pm until ten or eleven; whenever I finished; two to four jobs a night. You had to provide your own tools and as a part-timer, I didn't have a regular bench or locker; haul them in when I started, haul them home when I was done. I used Pep Boys parts of course, and whatever consumables I needed were provided by the store. One of those consumable supplies was brake grease.

I quickly used up the tube of brake grease I had in my kit and replaced it with what the store carried, a fair sized can with a fitted top like a coffee can; you opened it with a key. I don't recall the brand name, maybe 'Whitmore' but that's just a guess.

The can held four ounces and since you only use a dab here and there, a can that large was just about a life-time supply. It was hard, yellowish stuff with the consistency of saddle soap. The last time I saw the can was before we took off for a month- long trip down to Baja in 1991 to observe the eclipse.

About a year after the eclipse trip I was doing a brake job, went looking for the brake grease and couldn't find it. No problem; there's two real parts-houses in the town I live in, plus three or four of the fast-food variety. Next time I was downtown I stopped at the biggest parts-house, asked for can of brake grease.

There were four guys working the counter and I knew three of them, having done business there for nearly twenty years. They all thought I was joking, including one old fart who's been around since Henry was making T's. But not a one of them had ever heard of brake grease; swore they had never carried it, hinted that there wasn't such a thing. Ditto with the other parts-house. And ditto on the humor, too. They were convinced I was pulling their leg -- or someone was pulling mine, like sending a seaman duce to the bosun's locker for twenty fathoms of chow line.

I had to drive ten miles to another town, go to a Chevy dealer and pay a ridiculous amount for a tiny plastic tube of 'High Temperature Grease' and the gratuitous comment from the parts- guy, "Nobody calls it brake grease any more." I do.

If the counter-men at two parts-house had never even heard of brake grease it's a fair bet they haven't been selling much of it, which gives me a hunch a lot of you may not of heard of it either. And don't go a'waving St. Muir at me. Mr. Muir was a writer and a publisher; my grandmother was a better mechanic.

Before writing this I dug through a stack of shop manuals to see when brake grease lost its honest name. A couple of recent Haynes manuals still call it brake grease. Toyota calls it 'Special High Temperature Lubricant (Brake)'. The Bentley VW manual (66-69 Sedans) doesn't show you where to apply brake grease, although they offer a cryptic 'Use lubricants sparingly,' as if you'd been born knowing what, where & how.

Here's the where: On the threads of your adjusters. Take them apart, clean them, apply a dab of brake grease, reassemble them and wipe off any excess. Then put a dab at any point on the backing plate touched by the shoes; I think the bugs have four such places, two per shoe (most cars have three, a few have four). Then you put four other dabs on the ends of the shoes, where they contact the pivot, adjuster or wheel cylinder piston. When you assemble the rear shoes, put a dab on the link pin before you install a new Circlip. Put a dab where the parking brake cable fits to the lever.

Here's the how: A dab means just the lightest smearing of grease; use your finger. A two-ounce tube of brake grease should be enough for 25-30 brake jobs, mebbe more.

Here's the what: Ask for 'High Temperature Lubricant.' (Even then I'd be wary if it didn't mention 'suitable for brakes' or something similar.) And don't be surprised if you have to go to a dealer to find it.

Sermonette

The geezer behind the parts-counter had been selling parts for forty years and swore he'd never heard of brake grease. That told me he hadn't done too many brake jobs; from the look of his hands, he may not have done any at all. But he knew all about it and was quick to share his perception of reality.

On the other hand, when it comes to brakes, no grease at all is better than one dab in the wrong place. Your brakes won't work as well but the wiser course is to know what you're doing before you do it. Hanging around a professional brake shop and keeping your eyes open wouldn't be a bad idea.

-Bob
久久这里只精品国产99re66