Sunday Morning, A report from Fantasy Island, GM90 failure

I’m sure you remember Fantasy Island?

Noel Douglas (ON Left)
Noel Douglas (ON Left)







Noel’s Parents immigrated to the Fijian Islands from Scotland  some where in the later forties I’m told..

I remember having a Fijian born customer drop by my shop here in Washington State  years back, he was a handsome young man, and his Inlaws owned an Island here in the San Juan’s north of me.   He and his brother-in-law were designing new power for the family Island and bought a generator.  We talked a little about Fiji, and I took the risk.. “Do you know Noel Douglas?” The young man looked stunned.. his jaw dropped, he gave me a wide eyed look and said ” YOU KNOW……. MY UNCLE NOEL?”  I replied, “sure but that’s not too amazing in the alternative Energy Crowd… because your Uncle Noel is pretty well known in our circle.

Noel Douglas came to Fiji as a boy, he learned at his Father’s side the same way my friend Soon Wah Lee learned from his Father in Malaysia. All of them involved in making plantations run in their earlier years.  They moved on to other things, but never able to stay away from their love of engines and mechanical things.  Noel does import a lot of stuff, Fijians normally need make their own power, pump their own water, and more.

Since the Island pretty much runs on diesel, and diesel is normally sold in 55 gallon drums, there’s a lot of logistics to keeping guests in luxury, and in Air Conditioning during parts of the year. This includes a specialized boat designed for running to a fuel dock on one of the larger main islands, and Noel has experimented and now does this task with half the energy.

One engine Noel has had good luck with is the GM90 from Lovson in India, they sell it branded as the LG6, or LG8.  The failure we discuss below happened at 20,000 hours of service, a remarkable feat for a third world engine.  This particular engine was doing water pump service for the island.

Here’s Noel’s email  to me:

Hi George,I am attaching images of a crank shaft broken in two. I never thought this could ever happen. This engine is one that drives my water pump which supplies water to the Resort. I have had amazing service from these engines which run continuously year in year out. This one would have done over 20,000 hours without any parts replaced. The engine before it ( same type ) had done over 30,000 hours when I replaced it and it still runs today making electricity for one of my workers in the village.When this crank shaft broke all the bearings were still perfect and the crank where the bearings fit is still perfect.I am at a loss as to how and why this happened.Regards,Noel 

Noel Douglas Matangi Private Island Resort Box 83 Waiyevo Post Office, Taveuni. ph    679-7780061 mob 679-7105113OK,

Pretty remarkable he’s getting this kind of service, but as I have said before, this is a testament to the design, but you are foolish if you think India builds everyone of them with the same QC. One thing we’ve learned is that Lovson is good to send parts and offer support when things go wrong.  I’m not so sure  they’ll offer you a free new crank after running the equivalent of over 300,000 miles though, I know I couldn’t do that. Yes, I already have some theories about this failure, and I was going to share, but I thought it would be more fun to hear your theory first. All so easy to scroll down and leave a comment. Quinn, are you ready? Here’s three pictures Noel sent (gifts to us all)

 Failure 1

Failure 1



ND-GM90 Failure3

ND-GM90 Failure3
















Failure 2










Thanks Noel for all you share with us Students.


see comments!


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36 Responses to Sunday Morning, A report from Fantasy Island, GM90 failure

  1. John Gillen says:

    My 2 cents worth ok maybe a nickel. Now days with inflation 2 cents doesn’t go far.

    I’d say a bending fatigue failure, like bending a wire over and over again until it fails.
    From the photo it looks like the failure started on the same side as the oil hole. You can see the finer grain goes almost half way through. Where the course grain starts is when it gave up the ghost. From the photos I can’t see if their are inclusions or imperfections in the metal or machining. It doesn’t take much to cause a problem and over time even small things cause failures. I can’t tell if that is a flat machined side to side across the oil hole. It is interesting because it looks like it is the point of initial failure. I don’t know why the oil hole would have anything to do with the problem but the flat could cause a stress point.

    If the rotation was opposite of the Listeroid I’d say it was a failure caused by the power stroke. If I am right about where the failure started it would position the shaft 90* from TDC and put it in the meat of the power stroke BUT if the GM90 rotates in the same direction as the Listeroid the start of failure should have been on the other side of the shaft. That confuses me.

    Anyway I’d say that a bending load did it in. I’d also suspect a high belt load with the pulley at the end of the shaft or possibly a flywheel out of balance could do it too, especially if the engine was bolted down and the flywheel was badly out of balance. Without seeing his setup it is harder to analyze, at least that is the excuse I am going to use not to be more specific and if I am wrong. 🙂

  2. Bill Knighton says:

    What about the aluminum piston the gm90 uses? Am I correct that it uses a lower mass aluminum piston compared to the regular listeriods?
    It may be that the massive iron piston of the regular listeroid reduces the peak load on the crank. Yes it takes more force to accelerated it to peak s

  3. Bill Knighton says:

    Hit send accidentally. Continued:
    The iron piston takes more energy to accelerate back and forth than the light aluminum piston but it does not require a high peak force and that force is highest way before tdc when the force from compression is low. During highest compression forces the extra mass of the iron piston is an ally. would you rather try to drive a nail with a heavy hammer or a light one? But possibly more important is what happens on the power stroke. Especially in a carboned up engine. When mine gets loaded up from unheated veggie oil the combustions sound like metal on metal bangs. There I think I would like to have a heavy piston aborbing kinetic energy and buffering the crank from the shock of detonation. I do not know what the difference in mass is between the gm90 piston and a regular listeroid piston is so possibly none of this matters.

    • Bill Knighton says:

      After thinking more I want to alter what I said a little, just to be precise. I do not think a more massive piston takes more energy to move back and forth. It takes more to go from lowest speed to highest speed but then on the deceleration that energy is put back into the crank. A theoretical engine with no friction, with the head off and in a vaccume would keep going if cranked up to speed.

  4. wmshooke says:

    Torsional fatigue initiated by surface imperfection on the inside corner above the oil gallery thru hole? (small gray area)

  5. George B. says:

    Good input so far….

    • Quinn Farnes says:

      I’m just a hobbyist, not a failure analysis engineer, so I don’t know what my opinion has to do with anything. You already know that my bias is against counterweighted flywheels in “normal” ‘roids (which Noel’s is not). 3 lbs of cast iron in each counterweight at the flywheel rim pulls on each end of the crankshaft with about 120 times the force of gravity, or about 360 lbs of centripetal force at 650 rpm. So on each end of the crankshaft you have 360 lbs whipping around with each TRB serving as the fulcrum. A plain bearing would support the crankshaft better, but I can’t argue with success. That bending force is concentrated at the crank pin, and I’d expect it would break just as shown, at a right angle turn where the force would be concentrated. The fact that such failures are very rare indicates the crankshaft is pretty well made.

      But I know I’m all wet. Noel’s is a GM90 ‘roid with a counterweighted crankshaft. His engine wasn’t equipped with standard counterweighted 6/1 flywheels by mistake, was it?

      All that aside, it looks just like metal fatigue, to me, starting from a surface crack in the pin, perhaps a casting void, that widened until it failed catastrophically once it had progressed to about 1/3 the diameter of the pin. A closer photo of the break would be interesting.

      So what do you think?


  6. George B. says:

    As we reflect on yesterday’s blonde thought, we do a similiar thing, and that is we attempt to draw a circle around the problem and all the potentially connected elements that might contribute to the failure.. but note.. did I define my goal? Following written previously:

    Failure Analysis of the Matangi Island GM90 Failure.
    Why the long post, why must I inject other things into my comment?
    My answer valid or not… the Matangi Failure give us practice at critical thought, how wide do we make our circle when we draw around possible causes for study? What did we learn on Saturday when we watched a person struggle just to define her goal? The following comment will be read by so few, it’ll never be read by a member of the free energy crowd; because it’s buried under a pile of discussion about something other than fairy dust.

    March 25, 2012, I posted an email and pictures from Noel. What a gift he makes to our DIYer group, as he keeps good records, and is careful to provide good maintenance to his engines, it’s a way of life in Fiji, and you learn quickly that maintenance saves you a lot of money. The engine under study has its oil changed every other Sunday, unlike the folks that think these engines are magic, Noel is careful to make valve lash adjustments, and he pays attention to things like clanging and banging, he’s curious like all good DIYers are, and he investigates when he hears or sees something different.

    We note his report on the TRBs, this is so typical, and I reflect on my early curiosity about Indian supplied TRBs, and the Quality. As I’ve reported, I’ve never seen a bad one.

    We know we’ll pass on the blonde seen in Saturday’s post to give us an answer as to what likely caused this failure we discuss. And maybe we should note that there are folks who work for NASA that are employed to predict WHEN parts like this one will likely fail. MTBF (mean time before Failure) figures are not about a date and time, but more about the stresses a part is required to endure, and when it is likely to fail. As you can visualize in your mind’s eye, the part would last so much longer had it been left on the shelf as a spare.

    Our MTBF estimator needs a lot of information, he needs to know exactly where the bending moments are, the materials, the mass of all components, rotational speeds, and after he has gone over the calculations 100 times or more, he makes all kinds of disclaimers.
    • Assuming the engine is never operated at an RPM above X,
    • Assuming that loads are taken off on Flywheel A.
    • Assuming the pump is driven via a belt at the specified location, and at the feet per second specified in document number 123.

    We are DIYers, we close our eyes, and note things that could happen, we see our hands on the pump engine, did the governor ever stick? Did the flywheels ever over-speed? When we consult the machinist’s hand book, we note important things that our Great Grand Fathers understood, we need a proper radius at each end of this crank journal with a specified finish. And that hole drilled to supply oil, it needs to be chamfered, and finished per spec, and some engine builders will literally polish these areas in an attempt to reduce the chances of a crack developing in the area.
    Mechanical Engineers love to study these things, and many you talk to might say.. “I have no interest in that part, as we know the designed is flawed from the start, and we can make the part in another way where we eliminate that hole, edge, transition, etc.

    This is course is an example of how they think, and nothing to do with this part!
    We note the positive lubrication the GM90 design provides to the crankpin; no doubt this was done because the crank pin and bearing in similar prime movers ARE a source of failures under the designer’s study.

    Let’s go back to the bending moment thing.. I once saw for sale on EBAY a 12/2 that ran a generator through a speed increaser gear box, and then onto an 1800 RPM 4 pole generator. The power was taken off near the end of the crank, and a very small sprocket was used to transfer the energy to the reduction box. We have discussed this before, and when we close our eyes, and see the machine, we can see that a set of 2.8 inch diameter sprockets requires the transfer to be made at far higher torque with a far higher radial load on our crank shaft as compared to sprockets eight feet in diameter. We close our eyes, and see we’ve now traded off that high torque load for a lot of feet per second of chain whirring past us, BUT we have dramatically reduced the torque (radial load) on our crank shaft that WILL always fail at some point in time. Yes that may be well past 100 years of operation, but always prone to failure less it remains on the parts shelf.

    We know the 8 foot diameter sprockets and chain might be deployed by a guy working on a free energy machine, but not likely to be seen in our DIYer circle. The cost would turn off most of us, and the chain oiler, chain covers, and even the fact we’d need the engine more than four feet off the ground would give us pause in considering it as a solution. Digging a hole in the ground for same?, we’d pass on that….

    Some will think of the inexpensive serpentine belt, they’ll note it can transfer loads at the full feet per second the flywheel Rim runs at, which is likely the practical maximum speed, and we do so at the lowest (reasonable) radial load on our crank shaft.

    Other people in our community suggest small cogs are smarter, others say it makes for a more compact unit, and solves problems in lugging the unit from the fabrication shop to the field. The point is, there’s trade offs in near everything we do, and the seasoned DIYer recognizes this fact, the person working on the free energy machine never will.

    With all the words I’ve put on this page, you need realize I spent 20% of the required time to place them here, and too lazy to proof it and correct the grammar errors and more, I let it flow out of my mind and onto the page, so expect errors.. and know I have the mind of a student, and never do I think I should be in front of the class with chalk in hand. I only claim we should all own our own chalk board, and do our own math.

    So much of what we read is pure Bull Shit, and nearly everything a Politician says is bound to be Bull Shit.

    So this crankshaft under study.. we need know exactly how the part was finished, and we need discover exactly where the weak spot developed, and look at the finishes provided during the manufacturing of this part. Labor is a big cost, and whether we like it or not, the Bean Counters of the world are the reason most mechanical engineers have a job at all. If you left it up to them to run the entire operation of the crank shaft production, it would look like a piece of jewelry, and be delivered in a box that would put a lot of caskets to shame. The fact you’d need to sell it for five times the price is what would cost every one their job… Of course there are exceptions, if the purchase was being funded from the public purse, who cares?
    In the real world, it’s all about investment and the return on that investment, about risk VS reward. If you look at what Amonix is doing, it’s insane when we look at the cost of the alternatives, they claim to be leaders in the field of efficiency, and yet they target a deployment site where efficiency is the last criteria for consideration in the design! This goes totally un-noticed, and no pretty face in media will ever think of asking. I watch a favorite local TV anchor here in Seattle, she’s probably one of the nicest ladies on the planet, beautiful inside and out. But I know.. her job has nothing to do with thinking, that’s all done for her. We DIYers would last about 3 days in a job like that, of course most of us will never have her good looks, her charm, her ability to care so deeply for the impossible dream.
    We need to keep investment VS return on investment in the forefront of our mind, it’s reality, and so much of what we see in AE never ever discusses the real hard numbers of KWH production. Why is that? Perhaps KWH production is not the real goal, but on Matangi Island, it’s a necessity to learn exactly what gives you a return on investment, as there is no one else to pay your way.
    Totally un-related, but perhaps an example.. unless it’s our hands on the engine, do we know how the engine was used previously?
    Have a great Sunday..

    This Blonde moment brought to you by George B.

  7. George B. says:

    So finally.. we note.. the goal is to focus on the most probable cause of an early failure..and we know it was early….we note it is exactly where a fillet with a proper finish should be, but there are other possible causes as well. We need not count tire rotations or know how the load was driven 🙂

  8. Bill Knighton says:

    Is 30,000 hours and early failure? I guess I never think about 24/7. For me 30,000 will take decades.

    • George B. says:

      I guess we need note the failure we discuss happened at 20,000 hours, and the other crank is still running with well over 30,000 hours today….. so we know this was at least an earlier failure.

      We also need note, since this engine sees a steady film of oil on parts, and never really has to start up dry, the parts wear is likely reduced in this type of service.

      I’d need to live to well over 105 years old to see 3000 hours at Easton off grid where my one engine is.. The only reason to run it 10 hours days is when it’s well into the higher 90s F. I use it to irrigate and bring in a cool mist, humidity is low here, it works well.

  9. Bill Knighton says:

    I think the blonde was a fake and this was a skit. She looked like a smart person trying to sound dumb and even if she wasn’t I doubt she would put up with being ridiculed by someone who is I guess dumber than herself.

    • George B. says:

      Bill, these thoughts have crossed my mind.. that video could make some serious money with the advertising on there.. no way I’ll bet against you.. but if that’s an act, let’s nominate her for an Oscar! Now, I dare you.. tell me those magnet fools are all acting 🙂

  10. Bill Knighton says:

    Cool mist? Do you use one of those machines that makes vapor fine water mist? I have seen them at engine shows and they worked well even in north carolinas swamp weather.

    • Quinn says:

      The heck with that, what I want to know is what happened to the rest of the engine when the power contained in two 150 lb. flywheels turning 750 rpm suddenly uncoupled from each other at the crankshaft pin. That’s gotta sound like a train wreck.

  11. George B. says:

    I might ask Noel some more questions, about this particular failure. We talked on skype for about 45 minutes today, but dang, we were all over the map with the conversation as usual.. , everything from using a compressed air gun to toss fishing lures, to fish farming, to aquaponics, Noel is always trying different stuff, and he has one of his best friends over from Oz helping him engineer a few projects. I’ve got a picture of one of their research projects they’re doing right on Matangi, maybe it’ll be the heart of a post?

    But back to this failure, a better picture I got today suggests that there is no proper radius at the ends of the crank pin, and jsut as bad, the area is rough, and ugly.. this area should have a nice radius, and it’s worth the time to smooth and polish up this area. I would guess that this is the most probable cause of the failure, and properly finished and with normal use, I’d expect waaaay past 30,000 hours.. but… I’m just a DIYer myself, so we take that into account.. we had some excellent comments!

  12. Charles B says:

    Well I’m not an expert but the wearing on the one small line thats bright on the crank would seem to me that the bearing wasn’t riding evenly, mostly at the one point, seems to me it should be an even shine all the way across under where the bearing rides on the crankshaft. Or am I totally off base, may have been said in earlier comments and I didn’t pick up on it. Maybe the crank wasn’t machined true, or casting might have had a weak spot or combination thereof.

  13. George B. says:

    Some where curious…when was this condition found? Here’s some additional email from Noel, pretty amazing.. this is why we don’t associate every mark we see with the root cause.

    Hi George,

    Thanks for all the feed back.
    Yes the engine was unattended and it was still running after the crank broke. Some body heard unusual noise and the engine ” going up and down ” and turned it off. The ” going up and down ” is something he would have heard from a distance and would have caught his attention. It would have been going on for some considerable time before he got to shutting the engine down. I thought this was quite amazing. Most other engines would have stopped immediately and would have been a train wreck. With this one I would only need to replace the crank shaft to get it going again. The bearings all still look ok, all the cam shaft gears look ok and the 2 crank shaft seals would work again. I will be replacing all these and other parts. Amazing considering the length of time it continued to run and all the wobbling about of those heavy flywheels.



  14. Quinn Farnes says:

    Ok, that accounts for the bright area parallel to the break. The rod bearing and cap were holding it together. It’s pretty amazing, though, with all that force being supported by the rod bearing and the main bearing. In a multicylinder engine there would be other bearings to keep the crankshaft in line, but with this one, only one bearing on each side.

    Zooming in on the crank pin I can see now there’s not much of a fillet there, and that’s where it broke. Stress concentrated at a sharp corner and eventually failed. That’s a great lesson we’ll all remember.

    Thanks for showing us the pics George and Noel.


  15. George B. says:

    I can’t stress enough how valuable Matangi Island Power is to our DIYer community along with other REAL world off grid locations. Bill says… 30,000 is a life time for him, that’s true for most of us. Another thing we keep in mind, Noel is not trying to sell us a darned thing. We should be skeptical when we read some of the claims made by sellers.. especially when they refer to their work as ‘my wonderful’ research, my wonderful youtube videos, etc. I have so many stories to tell about those who have delusions so grand. I’ve often thought about a book of tales called “FAIRY DUST”. I’d ask Willem to write the forward.

    Off topic, but worth a mention. If we have a design capable of going the distance, AND parts finished to the Standards that our Great Grand Fathers understood the need for, THEN we might have a test bed to experiment with less idea situations than Noel’s fairly ideal; near continious running water pump.

    What do dry starts cost us? How much less does the govenor work WHEN the load is constant, and there is no need to mitigate changes in load as we might see if the Primer mover powering a typical generator and typical loads that come and go? In some water pumping cases, we might have fairly severe govenor problems and never discover it! What types of troubles (if any) might cause additional stresses on rotating parts and why?
    Alternative Fuels are a big topic of discussion, but in order to study them, I think we need a baseline, we need to know what the prime mover can do with typical fuels and typical lubrication, how do parts normally wear? We get a clear understanding from people like Noel who MUST keep records, and who live in the real world. I reflect on Sebastian sharing a mission statement of their research in Mali, he clearly states that the measure of sucess is when the share holders realize a return on their investment! This is a profoundly wise statement that should guide every DIYer in his decisions, with one exception… there are times we do stuff just to play, and we all do that at times.

    Noel has no choice, he must make a profit off his investments, as there is no one else looking after him, and furthermore, he has made jobs for a lot of familes who depend on his decisions for their income. The cost of fuel, the high costs of landing products onto the Fiji Islands is a large expense indeed. Noel is always looking for the better solution. Thanks to all who have commented so far..great comments, and if I were the teacher, we’d be handing out a lots of As.

  16. George B. says:

    Buried deeply under this pile of comments is the reality that the GM90 design CAN go the distance! We’ll read posts in forums that all India has to offer is junk. We are able to make the distinction between bad designs,and poorly made parts. We know how some of these defects are created.. often by people who are paid by piecework versus the hour, and who have no understanding of the parts they pour, hammer, and machine. As I close this AM, I am still thinking about that collection of stories called ‘Fairy Dust.’

  17. George B. says:

    Consider the bending of the crank, notice how the flywheels have been moved out, and pulleys on the inside.. Is this a good idea? I know one guy who does MTBF calcs that woud like these flywheels any further away from the crank bearing than necessary..

    • Dave says:

      I personally would keep my 6/1 externally balanced flywheels as close to the TRB’s as I could. Not knowing all of the variants of 6/1’s or 8/1’s the video engine appears to be internally balanced……is it? If so the flywheels could be moved out with less effect than on the externally balanced models. I still would like them close to the TRB myself.
      I also had to do some research on MTBF…..I always thought some crankshafts will last forever and some maybe 20 hours a few even less. For many reasons of course and depending on the amount of engineering, and quality control invested in the manufacturing. I found this explanation of MTBF and it makes sense and solidifies my thought on MTBF….

      • George B. says:

        Great Article Dave,

        I guess our focus should be on the fact that people are paid to calculate these figures, and in the case of a crank shaft, they look at bearing support, materials, flywheel mass, cross sections, and more. Surface prep and surface finish has long been associated with early failures, as a student, I am forced to accept that as fact for the time. In our study of the GM90 on Matangi Island, we would likely assume that one engine running 5000 hours would have a higher probability of breaking a crank than any 10 absolute identical engines running 1/10th the time. there is the problem, no one I know would assume any two parts are identical.

        It causes me to think of the Boeing building just over the hill from where I live.. they torture parts of airplanes with robotics to discover when they fail. To think that boeing could no build parts with methods that eliminate those that might failure at 20 hours would cause far more of us to take the train.

        As for the bearing support, and the flywheel, it has always been my thought that you offset the flywheel just far enough to be able to put a tool in there to prove the gib end hasn’t wiped out the seal. Any further out, and you increase the chances that ‘we’ see the falure. Concentric flywheels are better, they still have errors, and any minute of movement in the centerline of the crank can produce bending loads between that flywheel and the bearing, the more distance between this two points, the more likely of developing a failure in this area.

        I’ll need to read this article more times for it to sink in.. I notice the Mil produced a MTBF of 3000 hours for an APU, and their pull and replace intervals are 1000 hours, I’m not sure what we learn from that relationship.. The MIL has the same goal many of us do, and that is a working power source when we need it, and for as long as we might need if for any given mission.

        Standing by to learn more.. but a note, There are a lot of DIYers in Oz who are fired up over clones that resemble part of Their Heritage, they had many 6/1 CS engines, most have been sold for scrap, same as we did here with master pieces of our past. Many powered sheep shearing operations, milking parlors and more. Guys like Benny have a lot of fab skills, but they are just like us, they are inthe process of learning the finer points,…. I know I will still be learning when I die. It’s pretty scary to think there’s so much to learn about one of the more simple engines ever made…

      • George B. says:

        Dave, did I forget to say yes, internally balanced

  18. bob g says:

    my vote is for a poorly ground fillet (or is that filet?), you see this sort of failure after a regrind on many diesel engine’s, usually much sooner than later however.

    the big boys (oem’s) will often grind and polish the fillet, roll the fillet (which imparts a compressed region in the root of the fillet), or induction or flame hardens this area, or… some, part or all of the above.

    i can’t see on my puter, however if one looks very carefully generally you will see the crack propagating from the start of the crack in steps out to failure. it sort of looks like tree growth rings, first starting out very closely spaced with each ring getting progressively wider, up till “snap” and its done.

    my bet is if you look in the fillet you will see the start of these “rings” or “lines” starting at the surface of the fillet, and commonly it will start at the root of the fillet where it meets the journal, however it could just as easily start at the fillet to cheek interface.

    having said all that, it is also possible, (again i can’t see well enough from here) that the genesis is internal to the crank, a small flaw in the forging perhaps, if so the fracture lines will be very closely spaced at the start of the crack and work outwards to failure getting larger as previously described.

    i would suspect that any single cylinder engine with massive overhung flywheels, and perhaps heavy belt sideloads make having very good fillets mandatory for longevity.

    what amazes me is how few failures of this sort actually are reported, i would expect far more problems coming from poor machining from india all along. this tells me that the fillet area should be so flawed that even a nearly blind guy could find the problem given a good look with good light, or… there is a flaw in the forging?

    late to the party i know, but having had to diagnose many crank failures over the years i find this sort of thing fascinating.

    bob g

    • George B. says:


      I think most of us have included the fillet, filet as a probable cause.. I’ll see if I can send you a better picture. Thanks for stopping by always enjoy your input.. Fairly impressive huh, one doing 30,000 hours with zero parts!

  19. kevin hoffman says:

    looks like all of the above, after 30 years of engine repair , I would check your pulley load , but really suspect a bad casting. but lets not forget a mishandled engine during shipping , possbly dropped on the flywheel.

    • George B. says:

      We’re talking 20,000 of running once this engine was moved into it’s place of work.. anything is possbile, but I go for the area where the fillet should be, and the fact that it was crudely finished AND missing a proper fillet which is know as an important part of makig a reliable crankshaft.

  20. Luke Wadsley says:

    The tapered roller bearings for the crankshaft require some pre-loading; if this is too high, the eccentric of the crankshaft would be compressed between these two bearings and would create additional stress at the crank eccentric. Do these bearings get shimmed somehow to adjust the preload? Might be worth doublechecking if it is not too late on the re-build.

    • George B. says:

      Luke, these are indeed shimmed, seems there’s a margin that can be tolerated..but more than one error can work to cause a premature failure.. My vote is for the ugly finish at teh crank pin and the lack of a fillet. Thanks for your comment..

  21. Pat Young says:

    Hi George,
    I think the wrong question is being asked, these tapered bearings are in the completely wrong application, as they require preloading to work correctly, as shafts and crankcases never expand at the same rate it would be almost impossible to come up with a preload spec that at some point in the engines operation that either left the bearings unloaded or the crank overloaded, two of these bearings could be used on one end of the crank opposing each other with a floating roller bearing at the opposite end to take heavy thrust loads, but some how the crank must be allowed to float. I think the question here should really be how did any of these cranks survive, its a real testament to the thoughness of the crank castings.

    • George B. says:

      Pat thanks for contributing! As I remind myself and others, I am the student not the teacher.

      I can say there are several industrial engines like the old Kohlers that run forever and have tapered bearings. I have asked the old timers who rebuild these and some of the Wisconsin Industrial singles, and they claim the preload isn’t all that important, from a few thousands of movement in the shaft end to end, or a little preload seems to work, and they run for a long time. One Kohler I know of has been rebuilt three times and still using the same bearings.

      Pat, I think several people nailed it, the crank was finished poorly, but there could be other contributors.. I do know.. no engine builder would have accepted that crank!


  22. Trev says:

    I think its because it has roller bearing mains – when worn they allow the crank to whip – plain bearings less so

    • George B. says:

      Best thing ever for a single was TRBs, I’ve never seen bad ones. Some industrial singles were rebuilt three times, and the TRBs reused! It’s my thought, opinions vary.

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