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Thumper---A new 1 3/8" bore i.c. engine

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  • That looks like a simple and elegant solution.
    Kansas City area

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    • I scrounged around in my flat plate box to find a piece of material to make this manual spark advance from, and the only bit I found close to the right thickness had some rust pits on it. Oh well, that will be hidden in behind the flywheel. I have to call my nut and bolt store and see what they have in the line of Belleveille spring washers so that I can put them under the head of the bolt which goes thru the slot into the engine frame to keep the spark advance from slipping and resetting itself.
      Brian Rupnow
      Design engineer
      Barrie, Ontario, Canada

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      • Another way to keep the spark advance from unintentionally moving would be a series of divots or holes every 5 degrees or so and a spring loaded ball or plunger. It's probably not necessary to have resolution finer than that.
        http://pauleschoen.com/pix/PM08_P76_P54.png
        Paul , P S Technology, Inc. and MrTibbs
        USA Maryland 21030

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        • And the ignition timing handle is added. One picture shows the entire engine set up on an angle plate in my milling machine so I could drill and tap the single #10-24 thread thru the side of the engine for the bolt that keeps the timing handle in place. The other picture shows the engine setting on my side table with the installation completed. Tomorrow I will set it up to run and see how big a difference the timing makes to the power output.

          Brian Rupnow
          Design engineer
          Barrie, Ontario, Canada

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          • I just went down to my "Nut and Bolt" store and picked up a dozen Belleville washers. For those of you who haven't heard of them, they are a spring steel flat washer, which have a curve built into them---They're not really flat. In situations like I have with the new timing handle, you want it to stay wherever you set it and not move out of adjustment from engine vibration. However, you do want it to swing freely "by hand" but then remain in place. These Belleville washers are the answer. You can stack 4 of them together and put one ordinary flat washer next to the part which has the slot cut in it. They work very well to put a constant "pre-load" on the part which must be moved by hand but not by engine vibration.
            Brian Rupnow
            Design engineer
            Barrie, Ontario, Canada

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            • For those who bought a set of plans for this engine----This is the timing handle that I added to the engine.---Brian
              Brian Rupnow
              Design engineer
              Barrie, Ontario, Canada

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              • Today I started and ran "Thumper" with the new ignition timing handle in place. Did it make a difference?--No, not really. I could manually adjust the timing thru a range of about 75 degrees. With the engine running under no load conditions, I couldn't really see it affecting the way the engine ran. The engine ran good, but it ran good before I added the ignition timing handle. I have one more test to make, and then I will put this thread to bed. I want to set the engine up to run my sawmill edger, and see what difference the timing handle makes when the engine is under a load. If it does make the engine run stronger I will post a video of the engine running the edger and edging boards. If it doesn't make any difference to the power under load I will let you know.
                Brian Rupnow
                Design engineer
                Barrie, Ontario, Canada

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                • You never responded before if you manually opened the throttle more when loaded during your previous test. Obviously not a minor factor.

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                  • Sparky--On my previous test I had turned in the throttle stop screw until the engine was running at 2000 rpm before engaging the clutch. When the clutch was engaged and the edger was running, it would feed a board thru the first set of pressure rolls and about half way thru the cut the engine would bog down and stall.
                    Brian Rupnow
                    Design engineer
                    Barrie, Ontario, Canada

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                    • Originally posted by brian Rupnow View Post
                      Sparky--On my previous test I had turned in the throttle stop screw until the engine was running at 2000 rpm before engaging the clutch. When the clutch was engaged and the edger was running, it would feed a board thru the first set of pressure rolls and about half way thru the cut the engine would bog down and stall.
                      Yes, I read that before. So, you did NOT manually increase the throttle when the board engaged the saw then ! Not surprised it loaded down, its sort of like letting the clutch out on the car, on a hill, without giving it some more gas at the same time. Same concept, car cruising at 2500 rpm on level ground, comes to a BIG hill, will bog right down if you don't increase the throttle.

                      You were expecting this to behave like a electric motor, not going to happen. Try increasing the throttle when the wood enters the blade and it just begins to bog, bet it responds nicely.

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                      • Originally posted by Sparky_NY View Post

                        Yes, I read that before. So, you did NOT manually increase the throttle when the board engaged the saw then ! Not surprised it loaded down, its sort of like letting the clutch out on the car, on a hill, without giving it some more gas at the same time. Same concept, car cruising at 2500 rpm on level ground, comes to a BIG hill, will bog right down if you don't increase the throttle.

                        You were expecting this to behave like a electric motor, not going to happen. Try increasing the throttle when the wood enters the blade and it just begins to bog, bet it responds nicely.
                        This is my thinking as well.
                        The electric motor is a good analogy.

                        An internal combustion engine requires more fuel and air when subjected to a load in order to maintain engine speed, either accomplished automatically by a governor or manually by an operator.

                        The electric motor on the other hand simply draws more current to maintain it's speed under load.
                        In both cases when more energy is required for any additional load over and above it's "idle" speed, more energy must be supplied to the engine/motor in one form or another.
                        Last edited by Willy; 05-16-2020, 03:49 PM.
                        Home, down in the valley behind the Red Angus
                        Bad Decisions Make Good Stories​

                        Location: British Columbia

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                        • And yet, if there was nothing suddenly different at that point in the "cycle", if it was OK until then, it should make it through. The saw was cutting, and it ought to keep cutting. The issue must be a sudden increase of load, such as the spring rollers that Brian suggested.

                          Just like an old JD tractor, it sits there idling, but you can put it in gear and drive it, maybe even tow something, all without touching the throttle. I know that works with a friend's JD 40U. Some engines seem to have a "reserve", and some do not.

                          Not sure why that is. It DOES seem to be more prevalent with older long stroke higher torque engines, the short stroke "screamers" often bog down if you just show them a picture of a load. They might be inefficient at idle, and burn fuel better with a load on them, or some other reason. I know it happens, it's the reasons for it that escape me.
                          Last edited by J Tiers; 05-16-2020, 07:50 PM.
                          CNC machines only go through the motions

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                          • I recall the John Deer 40's had a governor.

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                            • Originally posted by J Tiers View Post
                              And yet, if there was nothing suddenly different at that point in the "cycle", if it was OK until then, it should make it through. The saw was cutting, and it ought to keep cutting. The issue must be a sudden increase of load, such as the spring rollers that Brian suggested.

                              Just like an old JD tractor, it sits there idling, but you can put it in gear and drive it, maybe even tow something, all without touching the throttle. I know that works with a friend's JD 40U. Some engines seem to have a "reserve", and some do not.

                              Not sure why that is. It DOES seem to be more prevalent with older long stroke higher torque engines, the short stroke "screamers" often bog down if you just show them a picture of a load. They might be inefficient at idle, and burn fuel better with a load on them, or some other reason. I know it happens, it's the reasons for it that escape me.
                              My guess would be that Brians engine has very large heavy flywheels for a engine its size, I bet the momentum from those delays the bog when the saw first enters.

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                              • John Deere 40U and pretty much any tractor made in the last 100 years have a governor. It would be steady job to move the throttle lever for every change in load.

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