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

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  • Originally posted by Sparky_NY View Post

    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.
    Makes sense to me!

    -js
    There are no stupid questions. But there are lots of stupid answers. This is the internet.

    Location: SF Bay Area

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    • Originally posted by Captain K View Post
      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.
      I have to do that on my Massey 35 as the governor has broke again. Need to be an octopus to drive the thing for any loader work, but I use it so sparingly anymore, It's not worth the effort required to tear into it to fix it right now. But when It was working.....you set the throttle lever where you want and it keeps the engine there under load.

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      • Originally posted by Captain K View Post
        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.
        It was the same with my old S10 in 1st. Guarantee no governor in that, and it was a "short stroke screamer".

        The 40U might have a governor, but is it good at idle? It WOULD stall at idle, but it would take some load also.
        CNC machines only go through the motions.

        Ideas expressed may be mine, or from anyone else in the universe.
        Not responsible for clerical errors. Or those made by lay people either.
        Number formats and units may be chosen at random depending on what day it is.
        I reserve the right to use a number system with any integer base without prior notice.
        Generalizations are understood to be "often" true, but not true in every case.

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        • The S10 probably also had a vacuum or centrifugal advance, which may have helped it provide more torque under load at idle. If it was fuel injected, with a computer, it would have adjusted the fuel to maintain idle speed, much like a governor.
          http://pauleschoen.com/pix/PM08_P76_P54.png
          Paul , P S Technology, Inc. and MrTibbs
          USA Maryland 21030

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          • All the talk of governors is valid but not related to Brians problem at hand, his engine does not have a governor and as such would need the throttle increased in proportion to the load applied. Several posts back he mentioned that just engaging the clutch without the edger connected even bogged the engine some, thats not much of a load at all. This little engine shouldn't be expected to perform anything like a farm tractor or larger engine, some of these tiny engines barely overcome the internal frictions enough to even run, they are not torque monsters by any stretch.

            I find it somewhat hard to believe Brian did not consider throttling up under load but that appears to be the case from what he posted.

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            • A governor is the only proper solution here, however it may be too late to add one now. Second best would be to manually match the throttle to the load
              Last edited by Captain K; 05-16-2020, 11:26 PM.

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              • A governor does not have to be a precision device on the carburettor but could be, for example, an exhaust restrictor.

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                • Yes, probably bad comparisons, although I think engine design has a lot to do with it, since some ungoverned engines do seem to take loads better. They may have factors that tend to act like a governor even though there is no actual governor on the engine. Cooling fans can act like that due to the large change in the load they provide as speed changes, for instance. From what Brian says, this engine does not move enough air to have that effect.

                  Actually, the "formal" governor is the best solution, because if you set the throttle for the maximum sawing load, then it will probably speed way up between "boards", possibly almost to runaway. If you stay out of that condition, then it may stall, as Brian reports it does now. Otherwise, you have to watch the throttle and adjust it to just balance every load change, which makes demonstrating the motor no fun at all.

                  Governors can be fancy servo-systems, or they can be quite simple. A governor on this engine might just keep it from exceeding a set speed. That way you could open the throttle to where it is needed, and the engine would not over-speed. With more load, you would just let it bog down a bit, and not worry too much about holding a speed.
                  Last edited by J Tiers; 05-17-2020, 12:58 AM.
                  CNC machines only go through the motions.

                  Ideas expressed may be mine, or from anyone else in the universe.
                  Not responsible for clerical errors. Or those made by lay people either.
                  Number formats and units may be chosen at random depending on what day it is.
                  I reserve the right to use a number system with any integer base without prior notice.
                  Generalizations are understood to be "often" true, but not true in every case.

                  Comment


                  • Originally posted by The Artful Bodger View Post
                    A governor does not have to be a precision device on the carburettor but could be, for example, an exhaust restrictor.
                    That's an interesting idea -- keep the throttle wide open (or close to it), and choke the exhaust at idle. Have you ever seen this in practice?

                    Allan Ostling

                    Phoenix, Arizona

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                    • Originally posted by aostling View Post
                      Have you ever seen this in practice?
                      The practice was somewhat common on model aero engines back in the 70's or so. I do not recall seeing it on any bigger engine.

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                      • Originally posted by J Tiers View Post

                        It was the same with my old S10 in 1st. Guarantee no governor in that, and it was a "short stroke screamer".

                        The 40U might have a governor, but is it good at idle? It WOULD stall at idle, but it would take some load also.
                        The JD40U does have a governor and to some extent so does the S10.
                        The ecu on fuel injected vehicles controls idle speed through an idle air control motor to maintain a preset speed.Some later carburetor equipped vehicles even had solenoids in order to do the same.
                        Turn on the A/C or place an automatic transmission equipped ecu controlled engine into gear and the ecu receives a signal to increase the engine's idle speed up to the preset level. Most modern systems even account for use of the power steering by use of a pressure sensor that indicates to the ecu that more power is required due to it's use.

                        As I stated in a previous post, idle speeds are exactly that, idle, meaning no work done. The engine only produces the power to maintain that speed and precious little else, thus the term idle.
                        On a large displacement engine there is some reserve for minor loads, however it will slow down to some extent unless throttle position is altered to account for the increase in load.
                        Remember the days of 400+ cu. in. engines with carburetors? What happened when you turned on the A/C, that's right, the engine slowed down. Idle speeds were adjusted on these vehicles with the automatic transmission in drive and the A/C on. Not doing so would result in rough running and stalls at idle. Tune up specs related to idle speeds always denoted the difference between man. trans equipped engines and those with A/C and automatics. Even then, cranking hard on the power steering in drive at idle with the A/C on would just about stall even the biggest V-8 engine.

                        This characteristic of non-governor equipped engines is a fact, argue if you will, however it is an undeniable reality.
                        Home, down in the valley behind the Red Angus
                        Bad Decisions Make Good Stories​

                        Location: British Columbia

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                        • Willy: The S10 was not an automatic. And the behavior is also found with other older vehicles not equipped with sophisticated ECUs. As I stated, that may be due to other factors which act as a governor, even though the engine has no governor.

                          Your point on the V8 engines is directly on-target, and Brian did what you suggested to an extent. He set up the idle speed of the engine, and the engine was able to carry the saw load as a result, at least until added load came on it. He may be able to set it just a little higher and have it work.

                          Obviously a governor is the best solution, but it seems he has little appetite for any further fiddling with the engine, which was, after all, supposed to be powerful enough to handle that sawmill.
                          CNC machines only go through the motions.

                          Ideas expressed may be mine, or from anyone else in the universe.
                          Not responsible for clerical errors. Or those made by lay people either.
                          Number formats and units may be chosen at random depending on what day it is.
                          I reserve the right to use a number system with any integer base without prior notice.
                          Generalizations are understood to be "often" true, but not true in every case.

                          Comment


                          • Originally posted by J Tiers View Post
                            Obviously a governor is the best solution, but it seems he has little appetite for any further fiddling with the engine, which was, after all, supposed to be powerful enough to handle that sawmill.
                            As I suggested before, manually adding throttle when it starts to bog will answer the question if the engine is capable of developing enough power. Only then would a governor be a consideration. IF the engine just isn't capable of developing enough power, a governor isn't going to help one bit. Hard to believe Brian is avoiding such a simple test.

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                            • I have a few things to say about this engine, and immediately after I do I am going to go out into my main garage and try it one more time running the edger with the new manual ignition timing handle to see if it does make the engine run stronger or not. Firstly, I am completely blown away by the compression this engine has with the rings purchased from Debolt. Secondly, the flywheel fans do move enough air to constantly be moving air over the cylinder fins and dissipating the heat. They're not going to blow your hat off, but they are moving the air. Also, there is no measurable load imposed on the engine by these fans. (At least not with any equipment that I have). I will not be building a governor for this engine. The engine has been a complete joy to build and run, and even if it doesn't ultimately have enough power to run the edger, the engine has went together and ran easily.
                              Brian Rupnow
                              Design engineer
                              Barrie, Ontario, Canada

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                              • Originally posted by brian Rupnow View Post
                                ... the flywheel fans do move enough air to constantly be moving air over the cylinder fins and dissipating the heat. .
                                Cleared for take-off. Goose that throttle.

                                Allan Ostling

                                Phoenix, Arizona

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