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Jack's November 2005 Gear Crunch!
As we collect data, we learn what is good, an what isn't. Gears are one of those things that just have to be made right if you are going to run the hours that Jack does, and the hours that many off girders wish to run.. India has a reputation for making crap for gears, sure they make good ones, but you are depending on India to send you the good one, and in some cases you are depending on the fact that the builder knows the difference himself! As we look into this gear situation ever so deeply, we find that few people in India understand what makes a good gear train. You will be amused to know that some of the Prakash engines have thousands of hours more on them than Jacks, and no gear failures! This was a small time assembler, and we saw difference from one engine to the next, so who knows the difference from one engine to the next? I have edited some small portions of Jack's story so we do not share a trade secret of the PS engines, as we are using these parts to upgrade the Prakash. We have a new approach, do the research, specify the proper materials be used in the gear manufacturing process, and have them fitted to the engines we order. IT was a dark and stormy night in November of Oh Five…..
Actually it was just drizzling rain in the early evening when the pleasant and nearly ignored, distant thump of the 6-1 Listeroid and my window to the outside world, the computer screen, went silently dark together.
Except for the pang of impending expense it really didn’t bother me. I had accepted the fact that such a thing *WAS* going to happen sometime or other…..There’s just no such thing as a ‘good time’ for to occur. I had decided early in this project to treat any breakdown as an entertaining and educational experience and not a drama of inconvenience. Be prepared, it IS going to happen, was my attitude. Charged batteries and a spare genset helps relax with winter coming on.
I had even thought of what trouble-shooting steps to take so as to not make a bad situation worse. I thought of all the ‘what-ifs’ I could….. And then assumed whatever eventually happened would be something I hadn’t thought of before.
As I turned on a battery light and got my jacket and headlight and gloves I was running through the checklist of things that could have gone wrong—FUEL, WATER, OIL, and OTHER.
My first ‘test’ through the dark pumphouse door was a smell test…..All I could smell was normal oil vapor from the breather, a hint of exhaust, and wet farm dog. So far so good.
I had just put five gallons of fuel in the nine gallon tank, so knew if it was starved of fuel it was debris that stopped it and not forgetfulness on my part to feed the beast. I didn’t think it was a shortage of fuel that stopped it.
I shot the laser pattern of the infrared heat sensor gun over the coolant tank and cylinder head and the high point was 191 F. That’s good too! It’s always possible to have a cooling problem with a stuck thermostat or broken hose. I just *hate* the smell of crackling paint and bubbling grease.
I just HAD to know if it was seized so I rocked the flywheel half inch in each direction and felt a clicking crunch in an otherwise free-wheeling ‘feel’. It wasn’t seized and I thought the crunch came from gears and not a bearing. I went to soak in the hot springs and thought about it some and pretty well had visualized what I’d find in the morning. It’s not TOO bad….. IF that’s what it was. Gotta be the cam gear, hope it’s not the crank gear.
Day One--- I jumped in the Lister's chittlins about eight in the morning with a blowing snow and wind scraping leafless limbs on the tin shop building. It would have been spooky if it weren't for the four cylinder diesel blaring just outside the building supplying compressed air and power to the shop and house. I MISS the low thud of the Lister and can’t stand the urgent roar of 1800 rpms anymore. It only took six months for that evolution in acoustic taste to take place!
My dad was a great one for saying, “If I ever get the chance to do that again….”.
DON’T mount an engine in a closet!! I think the perfect place to mount a stationary engine is about four feet from a metal-topped workbench with a big window over it for light and a heavy vice on one corner.
My engine is mounted eighteen inches from a solid wall on both sides and the work bench is next door and it has NO windows.
When you lay a hand on a Listeroid that works for a living that hand is going to be dirty. It’s simply amazing what else gets dirty at the same time without touching anything! Oil vapors and dustbunnies, hairballs and cottonwood fuzz, get caught up in the flywheels and forms a black goo that would give India Ink and walnut shells a run for their money as indelible stain champions. It only takes about 15 minutes to pull the intake and exhaust manifolds and the coolant fixtures and have the head, valve train, cylinder, piston and rod laying on the bench. Another fifteen and the fuel pump, cam covers, cam and tappets can be there too. Beware! It takes an hour to get clean enough to get rid of any coffee you drink! Plan ahead.
When the cam cover finally hit the right combination of spoke spacing and flywheel rotation and slipped out from behind the flywheel like a magic trick, it was very plain to see what caused the sudden silence the night before. The cam gear had shattered in several places and left half the gear hanging by a governor weight. I didn’t go any further. I had company on the way down in the early afternoon so I found one semi-clean paper towel to take with me to open doors and turn on faucets…..Clean-up takes a while.
Day two---
I decided I could pull the cam and catch the intake tappet instead of pulling the tappet guides. I still haven’t made a puller and *now* I’m in a hurry. No problem.
Up to now I’d avoided moving the crank anymore than I absolutely had to in case debris was poised to cause more grief. After the cam was out and the intake tappet out I could rotate the flywheel and feel and look for more damage. Sure ‘nough, the pinion gear was missing a patch of teeth on one side and all the teeth were missing something..
Thanks to the lightning fast response from Joel, the Listeroid dealer, I had parts on the way I didn’t even know I needed, but did!
Since day one I’ve kept a series of small but incredibly strong magnets stuck to the floor of the crankcase to gather any metallic debris circulating with the oil. It was pleasantly noted that all the scrap created by the gear wreck was either heavy enough to sink and stay there or became trapped to the magnets. The pinion gear teeth had obviously lost a lot of their mass by abrasion and flaking and the half dozen magnets had iron fuzz balls the size of jawbreakers on them. I’m sure plenty of metal fragments went through the bearings, but I don’t think they went through twice. I washed down the crankcase with fuel and then hand lubed everything with squirted 30W and assembly lube when it went back together.
Day Three-- With the prospects of a big store-bought lunch and a very scenic waitress at the little post office, store, campground, café and social center of “town”, I drove the 22 miles of gravel and cattle to check the mail. Hot dog! I gotta’ box of gears and fresh meatloaf was the lunch special! I ate about an acre of meatloaf but it still didn’t make my jeans fit like hers!! (There’s some debate among the cowboys that her Wranglers might actually be a tattoo.)
They did a great job of wedging the cam gear on the shaft with a taper pin. The secret of taper pins stuck in a rough hole is to drill into the small end about half way through THEN bottom it with a bottom bit. The hole relieves the wedge to the sides and the flat bottom means the punch doesn’t re-wedge it. They'll fall right out with a smart tap of the hammer on a strong and *straight* punch..
The new cam gear is drilled and taper reamed for the pin, BUT the OEM was drilled while on the shaft and it was a teeny bit off center. That meant the cam gear didn't line up exactly with the existing hole, but a few minutes and careful strokes of a chainsaw file allowed a new taper pin to go through and wedge securely. I lightly peen the little end for security, too.
The new pinion gear is made of an alloy and is great great stuff!! It’ll wear until it’s ‘right’ and then last about half of forever at that dimension using it’s own self- lubricating and work hardening properties to give years of life as long as it has oil. This will be a good test and good application of these gears. I was really anxious to root around in the wearable parts of this engine and see what kind of wear patterns and signals had been deposited in the last two thousand hours of operation or so. I have a very nice stereo microscope that I primarily use for engraving, but I can retro-fit with more powerful eyepieces and metallurgical lighting for failure analysis work. CLOSE examination of the cam lobes show brightness in the high spots of the rather crudely ground cam, but HEY, they heat-treated them right and at this rate will last longer than a government program....and that's about three days longer than cockroaches. The tappets are just perfect. No other way to say it. The tappet faces are plumb flat and shiny. The sides of the tappets and both valves and fuel pump follower shaft are all glossy, but no steps or streaks or oval wear to them. The push-rod sockets are absolutely new looking with no signs of galling or wear and the pushrods are straight and both ends still smooth, hard and shiny.
The valve stems are pretty much perfect but the guides are really getting sloppy. I’ll bush those in the next month or so….with bronze bushings. The lash caps and keepers are still in great shape and the valve stem ends are mirror bright on the high spots but not mushroomed or galled. As an experiment I had used a 50/50 goo of zinc-based anti-seize and STP under the lash caps. It works, but it dries out to a stiff gum. I’m back to using half assembly lube and half zinc anti-seize. It stays liquid longer.
I had had a problem at a thousand hours of the rocker shaft loosening in it’s block. I traced that to a pinch clearance cut that was too narrow which cut down on the pinching power of the block a bunch. That allowed the rocker shaft to gradually move enough to wear it some. I re-cut the pinch clearance cut with a hacksaw which solidified it. Its’ still holding like it should. The rocker arms are just perfect. They’re still a slurp fit on the shaft and the pads are perfect where they contact the lash caps.
The cross-hatch is plain in the cylinder and the carbon at the very top of the bore flaked off with a pocket knife blade. The piston wiped clean with no wear apparent or any sign of anything but, 'just like new'. Cleaning the rings and grooves was as simple as spraying with WD-40, rotating the rings a few times to float out the black oil, and blowing dry. All the oil ring holes were clear and no sludge anywhere.
The fuel pump side cam bearing is showing some wear. It looks like it gets plenty of oil, but shows a 'triangle' wear pattern from the three loads on the cam. I'll replace that next time with manganese bronze. that material takes sudden loads better than tin/zinc bronzes. (Or the apparent scrap cartridge brass bushings supplied by some Indian makers.)
The big end bearings still *look* bad, with pits and frosting and spots of missing bearing metal, BUT, they look exactly like they did 1900 hours ago. There’s been no change for the worse. The crank is glossy but has a couple scores that will polish out at a future rebuild, but poses no problem now.
The obvious cause for single cylinder silence in this case was the pinion and cam gear. The pinion was missing teeth and the cam gear was missing chunks. It was obvious the crank had gradually wound down after the cam had stopped turning with the accompanying grinding of mismatched parts . The fact the valves are still straight is a testament to having a flat-top piston and the valve faces square with it. No damage in the head.
Gear post mortem—
The OEM pinion gear was made of particularly nasty cast iron. Microscopically, the gear teeth were ‘smeared’ into thin slabs with layers of dark carbon between. Under the microscope the wear surfaces look like a plate of chrome plated corn flakes. The hardness of the gear didn’t vary with distance from the teeth. Rockwell hardness of < 20Rc was the norm. The Brinell ball indentation, under oblique light, resemble mashed honeycomb with obvious porosity and inclusions. The tooth wear on the pinion is a combination of drive and backlash forces, with both sides of the tooth worn more or less equally. The wear is a combination of displacement and abrasion. The edges of the worn sections are ‘cast up’ from metal flowing from impact and pressure. At least three teeth of the pinion failed at once from a load against teeth worn to about .050 thick. The teeth all sheared off and then impacts from teeth not quite meshing in time caused scaring and several cross-direction impacts, presumably from teeth and fragments being shed and mashed as the engine came to a stop. The sections of cam gear seem to have fallen directly into the crankcase without interaction with the crank or pinion gears. The cam gear broke cleanly into five parts. with no apparent shedding of fine particles. THAT’S good!
I could find no damage to the crank, crank gear, main bearings or rod end. I’m betting the thick whirl of hot oil damped the scattering of gear parts and the whole episode was over in less than a second, except for the wind-down.
The obvious question is “Why did the pinion gear fail?”
Alignment? The wear patterns on the pinion gear showed perfect alignment. The teeth failed as a result of excessive wear and not uneven wear.
Hardness?? Testing was done in several places on the pinion gear, from near the worn surface of a tooth to the hub. Several series of indentations were made on teeth showing different degrees of wear/failure. All were consistent at just less than 20Rc. In other words the indentation from my portable “Peck and Peek” tester was larger in diameter than the 20Rc base line, but not by much. I’ll call it Rc 18 even though it’s out of my measuring range. It’s clear the gear is overall the same hardness and the failure of teeth in one spot isn’t the result of a ‘soft place’ in the gear blank. The cam gear test Rc 30-32 in all places and exhibits no wear at all.
Lubrication?? Since the failure took place at one particular place on the circumference of the gear, it’s normal to think maybe something failed that particular spot, like a lack of oil. I don’t believe it. To think anything in that crankcase is lacking oil is beyond comprehension. All you have to do is leave a plug out ONE time to convince you the bottom end is *getting* oil on it.
Firing impulse?? I thought at first the engine was (miss) designed to make the firing impulse occur at the same place on the pinion in relation to the crank on every firing stroke. But, the pinion gear has 37 teeth and the cam gear 44. Since I *know* the crank gear has less teeth than that and the crank runs twice the revolutions the cam does, it means the crank must have _____________teeth. So, the firing impulse should ‘travel’ around the pinion gear and spread out the force between an equal number of teeth…..shouldn’t it? I become about as mentally limber as a quartz rod with gear ratios and such.
Resistance from another source?? The only thing I can place as having a resistance effect on the pinion is the valve springs and the fuel pump. The cam gear has resistance when the tappet is ‘climbing’ the cam lobe and will have less resistance as the tappet is ‘falling’ off the back of the cam lobe. The intake valve opens 5 degrees BTDC (Before Top Dead Center) The intake valve closes 15 degrees ABDC (After Bottom Dead Center)
The exhaust valve opens 55 degrees BBDC (Before Bottom Dead Center) The exhaust valve closes 20 degrees ATDC (After Top Dead Center)
The high pressure fuel injection pump operates between about 320 and 20 degrees
I’ll leave it to others more talented to computer generated models and graphing wizards to illustrate the wear patterns, but its’ clear to see that all the “clatter” of applied and relieved stresses on the cam gear occur in places between 320 degrees and 195 degrees on the cam gear. The balance of the circle is ‘coasting’ with nothing to do but mesh with no real forces applied to the gear teeth. Could the pinion gear be in a harmonic ratio that puts all these stresses on one set of teeth? I don’t think the designers would have allowed that, BUT, the originals probably had better metallurgy in them and maybe they didn’t fail, so the ‘fault’ was moot until the Indian Hibachi Gear and Sash Weight Co. Ltd came on the scene with their peanut butter cast iron gear. An animation of the Lister gear train would, I bet, show us how these pinion teeth got beat up and broken.
Preliminary conclusions--- I think this failure is the direct result of poor quality in the pinion gear casting and insufficient mechanical properties to transfer the stresses from the crank to the cam. Hopefully the better bronze material will accommodate these stresses and increase longevity and reliability. There are test in progress.
More company and then a day in town…..TODAY it goes together. I’m tired of four cylinders competing for precious fuel and my impatience with gratuitous noise is beginning to show…..
Gunk from the water---- The head and cylinder cooling galleys were thickly covered in a soft, tan, clay substance. The accumulations were the thickest around the exhaust valve, but everything had it. It was soft stuff about like dried pancake batter that came right out with blast from a pressure washer....it's also a great way to get REALLY wet on a cold and snowy day.
The roar of the 3 gallons per hour genset supplying all of a thousand watts for my meager needs while the Lister is apart spurs me on....
I tried muriatic acid to boil out the crud in the head, but, this being a volcanic origin hot springs with no ancient lake beds to percolate through the water has very little carbonates or limes, only silica. Silica is pretty inert stuff. Thankfully it's soft enough to wash away with some water pressure. I found that acid will loosen the really caked-on deposits. Since my cooling system is a flow through to waste operation, I’ll start adding a little acid to the water supply once a month or so to keep down the crud.
The new PS pinion gear is .040" thicker than the cam gear but the same width as the crank gear, so I took .008 off the face of the pinion gear hub to center all three gears. The crank and pinion are now aligned perfectly and the cam gear rides in the center of the pinion gear with .020 left over on each side. I’m counting on this extra rim of bronze to illustrate wear in the future. It should be easy to see from the inspection door with a strong light. Backlash is variable from .004 to .007 measuring every fifth tooth or so. It took six revolutions of the crank to 'even out' the backlash and make it surprisingly consistent all the way around. I didn’t actually ‘measure’ backlash once the cam was re-installed, but I checked the motion of the pinion gear by hand all the way around and found estimated backlash to be very consistent at about .005 during the ‘slack times’ of the cam.
Installing a cam without help and without pulling the tappet guides is entertaining to one semi-claustrophobic. My Lister is mounted in a VERY tight place anyway so my feet are always pointed the wrong way and one hand is caught somewhere or I've got four parts aligned with two hands and I *wish* I'd thought to slap that deer fly with a big black greasy hand *before* I started this phase.....
The timing of the cam was a snap with George's descriptions and pictures in the Listeroid Longevity CD (If you don't already have this CD, get it now. It's as necessary as a sense of humor and adventure to the Listerman.) An 'automatic' center punch is about perfect for marking parts. Just place and push and it dings a mark with no grinding dust and no electric power needed, either. I marked the valve timing on the flywheel after rotating the engine through several revolutions with the cam cover off just to be sure the timing is correct. It WON’T run one tooth off. Don’t ask how I found THAT out.
The cam cover is one of those tourist trap horseshoe puzzles to take off and put back on. It goes slick as a gut IF it's oriented within .003 inch of dead solid perfect AND you nudge the flywheel with a knee to move it a skunch to rotate it to within about 13 arc seconds of perfect.....and the phase of the moon is right and the puppy doesn’t investigate your plumber’s crack... THEN you realize the gasket is still on the bench.... Don't forget the governor roller and shaft…. It has to go in the hole in the cam end cover BEFORE it goes inside the flywheel……don’t ask.
It seems to take me longer to figure out how to get it right the first time....and then I forget how to do it before the next time.
How do ya'll re-install the piston in the hole?
I've tried that job several ways and think I've found the best one for a guy with limited appendages and vocabulary. – The instructions call for blocking up the piston skirt on the deck and lowering the cylinder down over the head bolts and piston while using a ring compressor at the same time. I'm not sure I can follow all that and I KNOW I can't do it with only two hands. I’d like to see a picture of the factory description of that chore.
I turn the crank to bottom center and place the bottom gaskets on the deck. Then slide the cylinder down over the head bolts. Loosen the head studs a little so they flop around some and they’ll self-center. Then I oil the bore with thirty weight. I duct tape half a roll of toilet paper to the bottom of the rod with the bearing cap off. It holds the bearing shell in place and protects it too. Carefully lower the big end of the rod through the bore with the proper orientation....I marked the bearing cap joint towards the inspection door with the auto center punch. Carefully slide the piston skirt into the bore and lower til the oil ring is at the top of the cylinder deck. Then, using large outside spring calipers with one hand like tweezers and holding the piston with the other, (it helps to have a big hand and fingers like a bunch of bananas), squeeze the ring together with the calipers and allow the piston to lower down to the next ring. For each succeeding ring you have to re-orient yourself so the calipers contact the ring at ninety degrees to the gap. Be sure to alternate gap spacing to prevent oil pumping. The toilet paper is just a cushioned 'catcher' in case everything goes just right and it slurps right into place. I'd hate to ricochet the bearing cap bolts off the crank pin! It worked slick as a gut today. NEXT time I’ll have a store-bought ring compressor!
One sunny afternoon a week after it quit, with no company due and throw away clothes on, I assembled the rest of the Listeroid with renewed gaskets, fresh oil and water and closely inventoried the left-overs. Nothing important in that pile. I gave the crank my best “Three squeaks of the injector and accelerate through the compression stroke” effort and it cranked on the FIRST compression stroke, just like it has every time before. They can *almost* be boring.
Lister Truisms---
If it doesn’t crank, you screwed up somewhere.
It takes a day to repair a Listeroid, if you're slow. It takes a week to get the grease out of your hide, if you're fast.
The Listeroid has a personality: Old and patient, like an experienced draft horse, not young and devious like a snowmobile.
As I write this the snow is coming down sideways with a wind so strong it’s making the old school bell in the yard ring like a telephone. The Listeroid is running steadily and so is the heating system. Life is good again….. on Lister power.
Jack Belk November 14, 2005 Magic Hot Springs
JB |