Model Engine Maker
Engines => Your Own Design => Topic started by: Brian Rupnow on December 18, 2019, 11:37:12 PM
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This is going to be something a bit different. Most of you will have a fairly good knowledge of how a hit and miss engine runs. On a hit and miss engine, the governor disables the exhaust valve when the pre-set rpm is surpassed, holding the exhaust valve open and letting the engine coast until the engine slows down, at which point the governor allows the exhaust valve to close and the engine will once more be able to build compression and fire. However, there is a different way of governing an engines speed for engines which are not "hit and miss" types. In this type of governing, the governor opens and closes the butterfly valve in the carburetor to adjust the engine speed. In a perfect world, you "dial in" the speed at which you want the engine to run. If the engine speed slows beyond that point, a linkage from the governor opens the butterfly valve in the carburetor and admits more air/fuel mix to bring the engine back up to the "dialed in" rpm setting. If the engine rpm exceeds the "dialed in" speed setting, the governor closes the butterfly valve, thus starving the engine for fuel until it slows down to the dialed in rpm. I have a twin cylinder opposed engine that I built a few years ago, which has a manually controlled butterfly valve in the carburetor. I also have a governor which was salvaged from the very first "hit and miss" engine which I designed and built. (The engine ran, but was horribly unbalanced). Over the course of the next few weeks, I am going to try and "marry" the two bits of technology to end up with a "throttle controlled" engine. Follow along. It should be interesting.---Brian
(http://imageshack.com/a/img924/5475/Jmr9AZ.jpg)
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Is that sort of the same effect (but very different mechanism) that the cruise control on a car has, where it pushes the gas pedal down/up as it senses the speed change?
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It is the same end result, but I don't know how they do it on a car.
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Most lawn mower engines are regulated like that- a vane is in the cooling air flow path and is moved by the velocity of the air. These things can be very tricky to get right- they are more likely to hunt up and down in speed.
Many steam engine models have flyball governors, and they almost never really work. The balls are to light and the speeds to slow.
This should be an interesting project.
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Before I dive into this one, I want to set up the twin cylinder engine and make sure that I can tweak it manually to give a high speed of 2000 rpm and a low speed of about 1500 rpm. I have a laser tachometer and can measure rpm quite accurately. Last night I lay in bed thinking about this. If I don't want the engine to ever exceed 2000 rpm, that can be accomplished by a hard-stop on the throttle linkage which doesn't really involve the governor. I would like to have a "mode" where the governor is disengaged so I can start the engine with the throttle closed and the governor completely "locked out" where the engine will run at about 850 to 1000 rpm . When I have the engine started and do engage the governor, I would like the governor to take the rpm up to around 1500 and hold it there under a "no load" condition. As soon as a load comes onto the engine and the flywheel shows the smallest inclination to slow down, I want the governor to immediately open the throttle fully, not incrementally, and take the speed up to full 2000 rpm and hold it there until the flywheels are no longer seeing a load and the engine can drop back to 1500 rpm until the next load is applied.
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Since my twin cylinder engine is a few years old now, and has ran a lot, the first thing to do is to run a few diagnostic checks. The attached drawing and explanation will give a pretty good way to check the valves and rings on each cylinder.
(http://imageshack.com/a/img923/1180/Ibnrsi.jpg)
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Ummmm….. Couple of questions:
You are using the governor to sense engine load correct? Engine rpm drops then the engine is under load - right?
You plan on using the governor to then increase the engine rpm to full throttle, right? I believe you said this is about 2000 rpm.
When the governor is engaged and your engine is at full throttle, how are you going to sense the no load condition with the governor?
Just had a Brain Fart. What if you didn't go full throttle but set a mechanical latch to hold the throttle open enough to hold the engine at about 1900 rpm under load. Then when the load went away, the engine would overspeed to 2000 and you could use the governor to reset the mechanical latch letting the engine throttle back to the 1500 rpm setting.
This is assuming that the 1500 rpm setting would be a mechanical latch which would move the low throttle limit. I'm assuming that this is set/reset by your governor engaged/disengaged lever/whatever.
Don
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Don--All will be revealed as I figure it out.---Brian
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I don't think you really want the speed to change as most governors are set to keep speed constant under load.
Think about if you are driving your car at say 50mph on a flat road, you are only applying light throttle pressure so small opening of the carb. You now start to go up hill but want to stay at 50mph what do you do open the throttle due to the increased load but speed of the engine stays the same.
having stood and watched a few engines running a saw bench they don't speed up when the wood is fed in, there is a momentary drop in speed then back to what has been set yet the sound of the engine is quite different as it runs under load, as steam engine will go from a docile chuf, chuf to a real bark if the load is high
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So, now I have something to screw into the sparkplug hole and do my valve and ring testing. Now it's out into the blizzard to get my good wife some cold medicine from the drug store.
(https://imagizer.imageshack.com/img923/5220/GOmH7X.jpg)
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Jason--based on what I have seen so far, the load goes immediately from no load to high load. There is no smooth transition of load forces. Thus I want the engine to go immediately from fast idle to "wide open throttle".
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It is the same end result, but I don't know how they do it on a car.
Modern cars has electrical controlled throttle. So not a direct/lineair linkage between amount of opening pedel vs throttle body. So full pedal on low speed (manual) get a small % opening throttle and on a higher rpm larger % opening.
Indeed for cruise control, it is similar to Governor speed controlling system, but then with electrical controlled PID system that accurate the throttle valve to get to the desired speed measured by a speedsensor.
You can compare it with adjust a potmeter by hand to control the brightness of a led or the speed of a dc motor.
But I am looking forward in this governor valve controlled build Brain. What is the displacement of your twin?
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The engine is 7/8" bore x 3/4" stroke
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Testing the left side cylinder at 40 psi shows no leakage of either valve and no leakage at the piston. Now I will move over and test the other cylinder.
(https://imagizer.imageshack.com/img921/4884/OG7ljM.jpg)
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After checking the right side cylinder and discovering no leaking valves or rings, I went ahead and started the engine. It needs a bit of run time to clear itself out, but appears to be working okay. Tomorrow I will test the rpm range with my laser tachometer before starting any modifications to make it a governor throttled engine.
https://www.youtube.com/watch?v=r8JJmTa9ZrE
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Not that you'd necessarily want to do it this way, but is this an option? Set up a rev limiter at 2000 RPM. Set the idle at 850 to 1000 RPM. When you want to saw wood the throttle is advanced to full, the rev limiter kicks in at 2000 RPM, but full power is available as the load increases. I think wood chippers work this way.
Jim
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As with all things, the layout and development of something totally new may seem to look a bit "goofy". However, goofiness aside, the components all have to be modified and set up so it is physically possible to make and assemble them. I don't want to make any permanent changes to the twin cylinder engine, but realize that the governor may go thru some dramatic changes. At this stage of things, I have unbolted the fuel tank and set it aside, and sussed out an o-ring drive for the governor. From here I will move on to the linkage necessary to interface with the carburetor. I'm off with my grandson this afternoon to see the latest Starwars picture.
(https://imagizer.imageshack.com/img924/5195/75AUlO.jpg)
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May the Force be with you!
Art
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Art--I don't know if I have grown old and curmudgeonly, or if the quality of the Starwars movies has changed. I seen the first three in the 1970's?? and they were just wonderful. The next three that followed a few years later were just awful, and the most current three have a lot of special effects and explosions, but not much story to them.
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Art--I don't know if I have grown old and curmudgeonly, or if the quality of the Starwars movies has changed. I seen the first three in the 1970's?? and they were just wonderful. The next three that followed a few years later were just awful, and the most current three have a lot of special effects and explosions, but not much story to them.
Well count me into the world of "curmudgeondom" as well Brian. The movies today change scenes so fast that my mind just can't keep up.
Jim
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Well, here it is in principle at any rate. The "at rest" position of the carburetor throttle is normally fully open. As centrifugal force makes the governor balls swing out away from the stem-post, the center red rod moves downwards. This causes the blue assembly to tilt about the center of the hub (which is attached to the governor body with a shoulder bolt, not shown). This rotates the vertical governor arm, which is attached to the carburetor throttle with a link, and will bring the engine down to idle speed when the balls are fully extended form centrifugal force. So---Any load imposed on the engine will make it slow down. This means that the governor arms will move in towards the center of the stem-post as centrifugal force becomes less, swing the vertical arm, and feed the engine more gas to counteract the load and bring the engine back up to speed.The threaded handle with the spring below it can be adjusted up or down to put more or less pressure on the blue linkage to counteract the centrifugal force, which determines at what rpm the governor engages. There is more to this, but this is the basic concept to get your head around.
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Your design looks good Brian. I’ll be following along to see it put into practice. :popcorn: :popcorn: :popcorn:
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Brian,
Before you get too far into the design and build you might want to try starting the engine at wide open throttle. I have never had an engine that liked to start with the throttle wide open. I know that the newer lawn mowers and implements have fixed throttle settings but they also have a primer bulb to provide enough fuel with the throttle plate open.
On engines that had adjustable throttle control the cable would run to a lever which would pull a spring that was attached to the governor arm. The engine could be started with the throttle closed and then as the throttle lever was advanced it would pull against the governor arm (and governor spring) to change the engine speed.
gbritnell
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George--I totally agree with you. Provision will be made to allow starting the engine in the "idle" position. Haven't quite figured out how yet, but that will be part of the design. For now I'm just playing on the cad system, getting a handle on the three largest new pieces.---Brian
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There is a subtle bit of magic around that mechanical link between the governor arm and the throttle arm. It has to be a solid link in order to work and make the carburetor throttle arm move in concert with the governor arm.---But---when the engine is at rest and not running, the default setting of the governor is such that the carb throttle is wide open. These small engines are not fond of starting with the throttle held wide open. Therefore--That solid link must also be capable of being over-ridden so that when the engine is at rest and not running, the throttle arm can be held in the "idle" position so that the engine can be easily started. As I said, it is a subtle bit of magic. That solid link actually has to have a spring incorporated into it's design so that even though the governor is in the "wide open throttle" position, the over-ride can hold the throttle arm in the "idle" position. I will be addressing that issue and will post the updated solution when I get the design finished.
(https://imagizer.imageshack.com/img922/5650/n4M57l.jpg)
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Well, I never said it was going to be easy---
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Well Sir!!!--This governor controlled throttled engine isn't for sissies. I've rejigged things about four times now, trying to come up with a workable plan. A great thank you to George Britnell for giving advise on this. I can build practically anything, but it is nice if you have some certainty that whatever you build is going to work. I've been trying to comprehend what George is telling me, and scouring the internet looking for information on Briggs and Stratton engine mechanical governors. What you see here doesn't show the carburetor, only the throttle lever. One exhaust stack has disappeared, but only because it was going to interfere with my linkage. I am going to have to make a different shaped exhaust for this side of the engine.
(http://imageshack.com/a/img922/1401/AhvPPv.jpg)
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I was hoping to turn the radius on the bottom of the governor housing on my faceplate, but it isn't going to fly. The largest radius I can turn on the faceplate is 5.625". Poohhh!!!
(http://imageshack.com/a/img921/5943/2HzmIi.jpg)
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Use the faceplate, but on the rotab on the mill rather than the lathe?
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Brian, I think you are making your life more difficult than you need. You need to control only one variable.
your spring, oe the fly ball, both at the same time.... good luck ;)
here is a video on how it's made
https://www.youtube.com/watch?v=SSwSIA8qgR8 on how it's made
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Since the arc is just a tad to big to turn on my lathe faceplate, I will cut it out oversize and then drill a chain of 1/4" holes thru as shown, then cut it out on the bandsaw, then use my vertical oscillating sander to clean up the stubs of material left between the holes.
(http://imageshack.com/a/img922/8729/FbZlFv.jpg)
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As Chris says Rotary table would do it easy enough, just clamp to a bit of scrap.
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This went much faster than I thought it would. Of course when you have a cad system that gives you all of the ordinate dimensions, it's just a matter of turning cranks and watching the dro numbers. Merry Christmas to all of you guys and girls that may be following this thread.---Brian
(https://imagizer.imageshack.com/img924/1600/4O3fXp.jpg)
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Well Dang!! I'm impressed. Christmas is being celebrated a day late here because of various sons and daughters "in law obligations". This gave me a chance to sneak down to my machine shop and build the main governor body. A bandsaw, milling machine, and oscillating cylinder sanding machine makes short work of something like this. The old guy with the white beard and red suit and bag full of presents will show up here tomorrow along with all of my kids, spouses and grandkids.
(https://imagizer.imageshack.com/img922/2742/wBj8sw.jpg)
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Coming together quickly! Makes a nice bell-tower on top. :popcorn: :popcorn: :popcorn:
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Moving forward things seem to be mounting the way I wanted them to. I am finished with the governor body main parts. Next up will be the linkage which connects things to the carburetor.
(https://imagizer.imageshack.com/img924/2103/Dam6bg.jpg)
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Today was governor linkage day. The brass lever is moved thru it's arc of travel by an internal rod that is acted upon by the governor weights. Yesterday when I mounted the governor body to the steel hoop around the flywheel/fan, I somehow got it as crooked as a dogs hind leg. So--Part of the day was used up dismounting it, lining it up correctly, and then drilling/tapping new mounting holes in the hoop.
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Hello Brian,
That looks really good :popcorn:
Have a great day,
Thomas
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This morning I made the adapter which goes between the intake manifold and the carburetor, and the link which ties the governor lever to the carburetor throttle lever. I am not really sure what I'm doing here, and the more I do, the less sure I am. (That is not as unusual as it sounds!!). In the attached picture, my hand is holding the spring in tension, and the levers are pulled into what is actually a "wide open throttle" situation. As the engine runs and centrifugal force makes the governor weights swing out away from the center, it actually pulls the throttle lever against the spring tension, until the carburetor is in an "idle" position. I have to adjust the spring tension to a point where the engine will settle in and run at 2000 rpm. but not so far that the engine idles. Now, if a load makes the engine slow down, the governor weights won't have as much centrifugal force, and the spring tension will pull the lever into a more "open throttle" position, causing the engine to run faster and bring the speed back up to the magic 2000 rpm. So--The magic here seems to be my ability to adjust that spring tension so the engine runs at 2000 rpm but not any slower. However, that is only part of the equation. I also have to have the capability to completely over-ride the governor weights and bring the carburetor into a "full idle" position for starting. I THINK perhaps I need a counter spring pulling in the opposite direction to the spring I am holding, so that when it is engaged the carb throttle moves into a "full idle" position.
(https://imagizer.imageshack.com/img924/6145/ZTz0Zj.jpg)
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How did your engine respond to the throttle when you measured the rpms? I found that my twin will run and take up a load over a wide rev range but gets unhappy when I open the throttle under load. I will need to consider a more complicated carb.
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Happy 2020 Roger. I haven't yet tried to run the twin cylinder engine under any great load. I believe that the reason these small engines falter when being accelerated under load is that the mixture leans out. I will know more when I finish the governor. When this engine was finished a few years ago, I put up videos of it idling at about 8 or 900 rpm, and accelerating under no load. It hasn't been really used since.
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Update time---I really didn't want to cut the exhaust stack off on the governor side of the engine. Sometimes as I design and build these things, I see a way to change the design a bit and save myself some headaches. By brazing a piece of round 3/16" brass rod to the far side of the governor arm, I can move the spring over closer to the fan shroud to clear my exhaust stack. I have removed the pull cable and extra spring that showed up in a previous 3D model and went to a simple lever which I can move back and forth to determine the tension of the red spring. When I reach a point where the spring tension is strong enough to limit the motor rpm's to where I want them to be (about 2000 rpm governed) then I tighten the yellow threaded handwheel on the far side of the hand lever to lock it in place. I do have an idea for the mechanism that will completely overcome the governor and move the throttle into a closed position to make easier starting, but I have to chew on it for a while before I model it.
(https://imagizer.imageshack.com/img923/8210/b1pA6w.jpg)
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Today seen significant progress on the governor control lever. I can loosen off the knurled handwheel and swing the brass lever into whichever position gives the best spring tension. The spring tension is what sets the "governed speed". I was able to position everything so that I didn't have to butcher my exhaust stack. I still have to work on a mechanism to over-ride the governor and set the engine throttle into it's "idle" position, as that is the best position when starting the engine.
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Getting close Brian. We’re all waiting to see the chips fly with your reworked power plant :pinkelephant:
:popcorn:
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Happy New Year Craig. Your engine looks marvelous.---Brian
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Now we are in the final phase of this throttle governed engine. As it sets, two things are happening. With the engine setting at rest, not running, the single spring pulls the throttle on the carburetor wide open. When the engine is running and the governor weights fly outward, that puts tension on the spring and pulls the throttle into a closed position, but not all the way closed. I adjust the tension on the single spring to a point where the engine is running at 2000 rpm., which is close to the idle position, but not too close. This is a state of equilibrium between centrifugal force from the weights and the tension of the spring. Now there is only one issue left. These small engines are difficult to start when the throttle is "wide open". Now I have to devise an "over-ride" that will pull the throttle to the fully closed (idle) position for starting, but not effect anything else in the governor train. Once the engine starts and warms up in the "idle" position, I disengage this "over-ride" and the governor takes over to control the speed of the engine.--3D cad to follow---
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My Kohler Direct Lighting set has a solenoid operated choke to solve this problem. When the engine gets the signal to crank the choke is closed and as it starts firing and the revs increase the governor arm move forward and opens a contact that opens the choke and removes the power from the starting winding.
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This is the mechanism which over-rides the throttle spring and moves the throttle lever into "idle" position for start up. The pinkish colored bar has a slot in it that fits around the throttle lever. It is all clearance except for the left end of the slot. This bar moves left or right, and is held in position by a ball detent screw (yellow). It rides in a guide which is bolted to the main governor tower. So--In the current model, the engine is stopped, the balls are in against the stem post, and the pinkish bar has been pulled to the extreme right and is held there by the ball detent screw. The left hand end of the slot is touching the throttle lever to pull it to the extreme right which is the idle position. The engine is started in this position, and allowed to warm up. Once the engine is warmed up, the pinkish bar is moved to the left, and no longer touches the throttle lever. At this point the governor takes over control of the throttle. The pinkish colored bar no longer touches the throttle anywhere.
(https://imagizer.imageshack.com/img922/6848/8PoWxi.jpg)
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I will be "truly Impressed" if this system comes together like I'm imagining. I know that every sub assembly that I design works. I have built them before, and they worked. The big trick will be getting them all to work in harmony with each other. I know that similar full size machine assemblies work exactly as I want the model to. Best similar thing I remember was a local sawmill ran by a Caterpillar six cylinder diesel. It ran at a fast idle when the mill wasn't operating. As soon as the power was coupled to the stationary mill machinery, the engine would immediately kick up the throttle. It didn't run any faster, but the exhaust sound changed quite dramatically---You knew by the sound that it was working. Then when they put a 20" white pine log on the carriage and ran it through the saw, the engine would really start to blatt. It wasn't running any faster, but you knew by the sound that it was putting out tremendous power to keep the rpm's from dropping. After the log went through the main-saw, you could again hear the difference in the noise of the engine as it throttled back. It was all done mechanically, no human involved on the throttle controls. If I can do that on the scale I am working at, then yes, it's going to impress my socks off.---Brian.
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Brian,
If it doesn't work you'll figure out why and fix it.
The big trick will be getting them all to work in harmony with each other.
Just like herding cats. :lolb:
Art
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I still have to work on a mechanism to over-ride the governor and set the engine throttle into it's "idle" position, as that is the best position when starting the engine.
You could just put a second, manually operated, throttle barrel ahead of the existing one that would act in a similar way to a choke for start and warm-up. The governed throttle would tend towards fully open at starting speeds and so "cede control" to the manual one. As it warms up you open the manual throttle and the automatic one would progressively take over.
Just a thought...
AS
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Last night we had 4 year old grandson for a "sleep-over". He's a great little kid, but it didn't leave grandpa with a lot of machining time. I did manage to get the main idle bracket machined and installed. It is a rather complex shape, but turned out very well. I only have about one day of making parts left, and then I will see if all of these add-ons actually work. You would think that with all of the O-rings that I bought for the edger and then didn't use, I should have one that fits this application.---I don't. Everything I have is either too short or too long. Monday I will get on the phone and order one which fits this beastie.
(https://imagizer.imageshack.com/img921/3954/eEWUec.jpg)
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Okay boys and girls--we have a lot going on here. In the first picture, engine is stopped, governor over-ride pull knob is pulled to extreme right, which overcomes the tension spring and pulls the carburetor throttle lever into closed/idle position so the engine can be started. I didn't have a ball detent screw, so I made up a knurled and threaded brass knob which sets where the detent screw would have gone. I pull the governor over-ride to the extreme right and tighten the knurled brass knob so it stays there while I am starting the engine. Second picture shows the over-ride pull knob released, and the tension spring pulls the throttle to the wide open position. This is a situation that should normally never occur, because as soon as the engine starts, the governor balls will "fly outward" and pull against the tension spring, moving the carburetor throttle lever into a position which is actually quite close to the "idle" position. (if the engine were running, I would set the spring tension so the governor weights and the tension spring reach equilibrium at about 2000 rpm.) The third picture shows my hand holding one of the governor weights in it's "fly out" position, and you can see that the governor pulls the throttle lever back close to the idle position. That governor over-ride bar has an over-size clearance slot in it, and only contacts the carb throttle lever when it is pulled into the "engine start" position.
(http://imageshack.com/a/img922/8421/4SPxkp.jpg)
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Clever design Brain! Any close for a test run?
I just found this video recommend on my YT. It like same kind of application but then arduino controlled.
https://www.youtube.com/watch?v=v7GLQU-0Nwc
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Hi Alex--I'm hoping for a test run this coming week. Will post a video.---Brian
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When I first built this engine a few years ago, I machined a steel starter hub which attached to the end of the crankshaft to engage with my electric drill for starting. Then I discovered that the compression was so high that I couldn't comfortably grip the starter hub in my hand to turn the engine thru it's different stages to set timing, etcetera. No problem--I just machined a larger diameter piece from aluminum, knurled the o.d., and Loctited it to the outside of the starter hub. The other end of the crankshaft isn't available for a power take-off pulley, so now I am going to rework the started hub so that it will keep the knurled profile for a hand grip, but also become a power take off pulley.---Brian
(https://imagizer.imageshack.com/img922/1367/hB7Sni.jpg)
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Very nice work Brian, I'm still quietly following along. :popcorn: :ThumbsUp: Terry
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Hello Terry--Glad you've come along for the ride.---Brian
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In this picture, the starter hub and knurled aluminum ring have been removed from the engine and separated. They were only loctited together. A new intermediate hub has been turned and knurled, and will replace the old knurled aluminum ring but will still incorporate the inner hub.
(https://imagizer.imageshack.com/img922/3976/zmZI6i.jpg)
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And finally, there's my baby with the new starter hub-pulley installed. Room on the pulley for two 1/8" O-rings.
(https://imagizer.imageshack.com/img921/2729/AG1Ne0.jpg)
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Any time you take an existing engine and "repurpose" it to a different style, as I am doing here, some things get a little weird. This engine was designed and built with a manually controlled throttle, and now is being changed over to a governor controlled throttle. All of the new parts are made and installed, but I still need to mount the gas tank somewhere. It has to be marginally lower than the center of the carburetor, it must be away from the exhaust pipes, and the gas tank outlet still has to exit in the general direction of the carburetor. Playing around with the 3d cad model, I have found a position that meets all of these requirements and only requires that I make up one new plate and mount it to the steel bracket that holds the ignition coil. Looks a bit weird, but it works. This uses the original gas tank with no changes to it at all.
(https://imagizer.imageshack.com/img922/5278/gxNLmJ.jpg)
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This mornings work involved a new bracket to mount the gas tank, and a new, rather squirrelly looking yellow gas line. Gas tank and line clear all moving parts, avoid being close to exhaust stacks , and tank is marginally below centerline of carburetor. And that's it!!! I ordered a couple of new O-rings to drive the governor from the rear of the flywheel, and once they arrive we will see if this thing can fly---
(https://imagizer.imageshack.com/img923/9176/gb1fYj.jpg)
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You may remember that I made up a narrow 1/16" wide knurling roller to put a knurled finish in the bottom of o-ring slots on the pulleys I make. This was in order to keep the pulleys from slipping as they drove an o-ring used as a drive belt. I haven't used it before, but this morning I decided to do both driver and driven pulleys on the governor drive. this is what the knurled slot looks like.
(https://imagizer.imageshack.com/img923/1783/HWKbXR.jpg)
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How exciting!!! I have the engine running and the governor is operating and very sensitive. I haven't got things to the point where they are consistent enough to make a video, but it works. The engine is not terribly sure that it likes the additional load put on it by the governor system. I can take the o-ring drive off, and the engine runs quite fine. I put the o-ring belt back on, and the engine wants more throttle to run with the additional load. As it is running, I can see the governor weight system moving in and out against the tension spring and moving the throttle, seeking it's "happy spot". I have my office door open to keep from gassing myself, and it's colder than a witches tit in my office. Going to quit now and have some lunch, and try to get the grin off my face.
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A couple of short videos. I'm not finished yet, and there is a blizzard raging outside my office door, so I can't run the engine very long without having my door open. The fact that the engine runs and the governor is trying to do it's thing is quite positive. I am expecting to have better results as I refine things a bit. There is more governor action in the first video clip than in the second. I think I had the governor locked in position on the second run.
https://www.youtube.com/watch?v=mcqcSWhOrcI
https://www.youtube.com/watch?v=2xwvOKc0aAA
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Okay, third times a charm, and this is probably where I will quit for the day. The governor is working and controlling the throttle on the carburetor. I'm sure I have more tuning to do, and that arm which holds the end of the tension spring is going to need an arrangement to make it far more adjustable. I have to think on that one for a bit.--Probably need to make it adjustable with some kind of threaded screw to get fine adjustment. At any rate, concept is proven, and I like it.
https://www.youtube.com/watch?v=0rqDEkB6KNE
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That is very interesting to watch, seeing the lever moving as the speed varies.
Great!!
:popcorn: :popcorn: :popcorn:
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I probably burned up a few brain cells thinking of this--I want to turn the red threaded knob to move the green threaded rod to tension the spring---but I don't want the green threaded rod to turn. If I put a flat on each side of the threaded rod, and a slot instead of a round hole in the beige colored bracket, that should do it. This will let me fine tune the tension on the spring to give correspondingly finer tuning of my target engine rpm.
(https://imagizer.imageshack.com/img923/1919/9P1qsQ.jpg)
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Hello Brian,
Great job on that throttle and the motor sounds real good.
Have a great day,
Thomas
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And---On the weirdness-ometer-- I seen a dog wearing snow boots today. There is a foot of snow here, and it was a rotten day outside, so I went up to the Georgian shopping mall for my "fat man's walk". (Four laps around the mall=1.6 miles.) People take service dogs in training up to the mall. I seen a half grown German Sheppard dog, wearing a dog coat (I've seen dog coats before) and a set of pretty blue snow boots!!! I commented on it to the trainer, and she told me that "All the dogs are provided with snow boots in inclement weather." The dog didn't seem to mind the boots at all!!! Hey---I want to live another seventy three years---I'm still seeing new things that I've never seen before.
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This morning I built the fine adjustment bracket and flat sided 1/4" threaded part exactly like the 3D cad and it all works fine. I re-used the knurled nut? that originally held the first spring tension lever in place. Now I'm at a point where there is nothing more to make. Now it gets down to the hard part of making it all work in harmony. I shouldn't admit this, but I enjoy making the parts way more than actually getting everything to work. I have a fairly good success rate of getting things I design to work, but there are times when I wish I had George Britnell and Chuck Fellows standing here in my office to bounce ideas off of. Getting small engines to perform is 70% engineering, 20% experience, and 10% magic. Probably tomorrow I will take the drive belt off of the governor and set the engine up to run as well as it can without the governor. Recheck the ignition timing, the valve timing, and the carburetor needle settings. Once I have worked thru that, I will put the governor drive belt back on and make any necessary adjustments.
(https://imagizer.imageshack.com/img922/3450/5KbtKe.jpg)
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Brian,
The twin runs great, all your modifications to make the throttle governed part work great.
Art
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Excellent progress :ThumbsUp: :ThumbsUp: :wine1:
I can outweird that :) Whilt walking in the snow covered mountains my wife and I came across a dog with snow boots and sunglasses 8) The owner was positive that this was necessary as he wore snow boots and sunglasses ::)
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I'm feeling a bit under the weather today, so no real work, just a lot of heavy thinking. George Britnell had mentioned that these small engines don't really like to start with a wide open throttle, and I agree with him. That is why I made the sliding affair with the pull knob that could be used to over-ride the governor and lock the carburetor in it's "closed" position for starting. However---I have found that when cranking this engine with my electric drill that the governors are very sensitive and as soon as I start to turn the engine over, the weights fly outward and put the carburetor into "closed" position anyways. Although this style of carburetor does have an internal "idle adjustment screw" which actually limits how far the throttle closes it is giving me problems. Without changing the complex bracket that holds this sliding affair with the pull knob, I can replace the bolt on top-cover and have room to install a 1/4" threaded rod with a knurled end on it to act as the throttle stop. This will actually work against the throttle lever arm, instead of being part of an internal throttle stop. I have a good view right down the carburetor throat the way this carb is mounted, and much better accessibility to adjust the throttle stop to a point where the engine idles but doesn't die out and stall. (The carburetor is hidden in this view, with only the throttle arm being visible).
(https://imagizer.imageshack.com/img923/9519/jQ4sv6.jpg)
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I have made the changes outlined in the last post. Engine runs, but not happily. I am in the middle of removing the home made carburetor and putting on a purchased Traxxas carburetor. This is more of a quick and dirty diagnostic than anything. Self throttling feature will not run with Traxxas carburetor, however if the engine runs well with the Traxxas, then I know the home made carb isn't working properly. If behavior doesn't improve, I will have to dig deeper. The videos on Youtube had the links pasted in this thread. The Traxxas 4033 carburetor is just about the perfect size for large single (1" bore)and smaller (7/8" bore) twin cylinder engines. If I have any complaint at all about them, it is the fact that the side which attaches to the intake is a plain 10 mm outside diameter. This means that any time you want to use them, you have to make a simple adapter like the one shown here. I use a bit of 638 Loctite to attach the carb into a reamed 10mm hole in the adapter. I'll let the Loctite dry overnight and see what happens with the engine tomorrow. The governor has been disconnected by slipping the o-ring drive belt off the engine pulley.
(https://imagizer.imageshack.com/img924/214/vEQj6I.jpg)
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The engine did run with the Traxxas carb on it, but it didn't run consistently. I discovered it had a plugged gas line right where the line enters the gas tank. Even after I had cleaned out the blockage it wouldn't run consistently. Finally, I tore the engine down completely. I was really trying to avoid that, but ya do what you have to do. I decided that first order of the day was to replace the viton O-rings. I don't think they were the problem, but since I have everything apart that is what I will start with. The two old rings are on the left of the picture, the two brand new ones on the right. In case you were wondering---I hate this worse than snakes!!! I like to build an engine, tune it, run it, make a video of it, then move on to something else. This going back and conducting a post mortem on an engine which no longer runs the way I want gives me a big pain in the head.
(https://imagizer.imageshack.com/img922/5663/z0Cy0i.jpg)
(https://imagizer.imageshack.com/img924/707/jox9wh.jpg)
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Well I can only agree that it's never any fun when your engines aren't running as they should :wallbang:
I hope that you solve this soon, as we all hope to see it run the Edger .... :cheers:
Best wishes
Per
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I feel your pain Brian. I have a friend who has several dozen model engines that he and his Dad have built over his life span. He takes them to shows over the summer and he says it's a full time job keeping them all running properly.
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Engine has been reassembled with new rings. This complete disassembly has given me a chance to clean everything up and to get rust and crud off the fins of the cylinders. I found that the set screw holding one wrist pin in place had fallen out, but fortunately the pin hadn't drifted sideways and scored the cylinder wall. I don't use aluminum outer cylinder with a cast iron liner. I make the entire cylinder from one piece of cast iron. That way it is much less work, better heat dissipation, and all I sacrifice is a bit of pretty. Tomorrow as I reassemble things I will check valve and ignition timing. The engine is so clean and new looking now that it is rather startling.
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I may have found the culprit. The old rings were worn, but not to the point where the engine was losing compression, so they were probably doing their job just fine. However, as I proceed with the re-assembly, I have found that the adjuster for the intake valve on the right hand cylinder bank was way, way out of adjustment. It had backed off to the point where just the very tip of the cam was "grazing" the lifter. I had labelled the push-rods as I disassembled the engine, so they haven't been mixed up. I will reset all of the valve adjusters now.
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An update---I have hit the wall on this engine, for the moment. I have replaced gaskets, set and reset valve and ignition timing, replaced rings, replaced carburetors, and tested every individual part. Every member of the choir sings perfectly, but I can not get them to sing in harmony. This doesn't happen to me very often. I can't even get it to run with all of the self throttling apparatus disconnected. I haven't been able to identify anything specifically wrong with the engine, other than the fact that one valve adjuster was out by a fair bit, but even with that valve clearance readjusted, it refuses to run. When I turn the engine over by hand with the cylinder heads removed, it will put a good suction on my thumb which doesn't fade away, and gives a distinct "pop" when my thumb is removed. The gas lines are clear, and fuel will run from the hose when I remove it from the carburetor. The vent hole in the gas cap is clear. I have adequate spark at both plugs. engine spins freely with heads removed--no hard spots. Only thing left to do is remove the ignition points, starter hub, and brass gear cover so I can have a good look at the timing gears. Thank you for your patience.---Brian
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This is one of those one of those "unexplained mysteries" that you read about in the National Enquirer. I've got the poor old girl stripped right down to her undies now, having just removed the starter hub, ignition points, and brass gear cover. One of the things that I just discovered which doesn't affect the engine (I don't think)---I pulled up the detail drawings of both gears to see what I used to hold them to the crankshaft and camshaft---and found nothing!!!--I never added the set screws to the detail drawings back when I originally built this engine. This is a bit strange, since I've sold half a dozen plan sets for this engine, and I have never had a call nor email asking about it. Next step will be to ensure the valve timing (valve beginning to open X number of degrees before tdc or bdc depending on which valve we're talking about). My software can let me set things exactly where they should be, degree wise, and then give me a linear distance from the top of the piston to the top of the cylinder. It doesn't appear that either gear has slipped from it's appropriate position relative to the shaft it sets on, but I will check it anyways. This is about as close to the "beginning" that you can get when doing engine forensics.
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Insert Twilight Zone music here... "The Engine That Shouldn't Have Run... Ever... "
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I have everything torn down to the bare essentials. I'm checking valve timing as we speak. Ignition cam is off the engine right now. Will reset everything as I build the engine back up.
(https://imagizer.imageshack.com/img923/5817/SNiaPq.jpg)
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Insert Twilight Zone music here... "
you did ask.... https://www.youtube.com/watch?v=-b5aW08ivHU
I worked on a Kohler engine once.... guy said it ran but didn't have any power. Upon opening it up I found the problem. The cam gear and lobes were built as a single casting that was drilled through and rode on a mandrel. The casting was broken completely through between the gear and the cam lobes. I guess the gear managed to pull the cam lobes around enough to sustain running, but not enough when under power. One of the strangest things I've seen in a "running" engine.
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This set-up lets me know exactly when the cam lobe begins to contact the lifter. I rotate the crankshaft slowly by hand in the direction it normally turns, and as soon as the cam contacts the lifter, the needle on the dial indicator moves. At this point, I measure from the top of the cylinder down to the top of the piston. My software tells me that when the piston is 0.263" from the top of the cylinder, the rotational aspect aspect of 15 degrees before top dead center has been reached. Since I am leaving approximately .010" of valve lash, that figure will closer to 2.53" before the valve begins to move. Checking the actual distance with my Vernier caliper I measure .280" This is well within the range of acceptable, but since I have everything apart I will loosen of the cam gear and reset it to exact numbers. All of the cam lobes are 'fixed" to the camshaft, so any change I make now will affect al of the valves in the system.
(https://imagizer.imageshack.com/img921/3458/vq7KDz.jpg)
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Okay--Something is a little hinky. Based on the intake valve having a lead of 15 degrees before tdc, the dimension from top of cylinder down to top of piston should be 0.253" which includes the valve lash of about 0.010". I have reset the left side of the engine to agree with this,(It wasn't very far out) and that automatically sets the right bank the same. However, the exhaust valves should have a 40 degree lead before bdc, which gives a dimension from top of cylinder down to top of piston of 0.894". I measure 0.710" which means a lead of 60 degrees which is 20 degrees too much. All of the four cam lobes are Loctited to the camshaft, which is an acceptable method of cam building. I now have to check the cams to generate real numbers instead of working with theoretical numbers and see what's going on.
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The theoretical cam has 120 degrees of movement in the area which lifts the tappet. This translates to 240 degrees of crankshaft movement because of the 2:1 ratio between the crankshaft and camshaft. 240-180=60 degrees of movement which gets split between valve lead and valve lag. Theoretical split is 15 degrees before tdc. and 45 degrees after tdc. Real cam as measured with dial indicator has 130 degrees of movement affecting the tappets. This translates to 260 degrees at the crankshaft. 260-180=80 degrees to be split between lead and lag. 80 -15 degree lead=65 degrees of lag. 65 degrees of lag translates to measurement from top of cylinder down to top of piston of .706" and actual measurement on engine e is 0.710". This tells me that cams have not slipped rotationally on the camshaft.
(https://imagizer.imageshack.com/img923/2899/oTqOim.jpg)
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Tonight everything is back together. Ignition timing has been reset, Cylinders have again been pressure tested, and gaskets are all in place, nothing leaking that I can see. Liquid dish soap has been flowed around the cylinder heads while under pressure, and we have no bubbles to contend with, which pretty well assures no leaking head gaskets. Valve lash has again been adjusted. While I had the intake manifold off I gave it the old "Blow your guts out test" just to make sure there wasn't a big blob of gunk in one of the legs blocking the flow. Did I really see anything that would have prevented the engine from firing or running?--No, not really. Tomorrow we will try to start this thing again.
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Yar Bugger Billy!!! We're up and running again. What a mad thrash it's been. I tore everything down to the bare chassis, checked the valve timing, then on reassembly I reset the ignition timing. When completely reassembled, still no joy. I had spark, I had fuel, but engine wasn't firing. As a last result I unbolted the left hand cylinder head, relapped the valves and made a new head gasket. This was very encouraging. When cranked I had fire in the left hand cylinder and smoke rings coming out the stack, but still not running. Then I pulled off the right hand cylinder head and done the same thing on that bank. There was more to this than it seems, because it involved retapping a few holes and making up some more specially shortened bolts. Finally I was rewarded with a running engine. Turn up your speakers. I do some "voice over" in the video, but the engine is noisy. Now that engine is up and running, I will do some fine tuning before I put the throttle governing governor back on. the engine. The video is crappy but I will make a properly lighted and sound controlled video after the fine tuning is completed.
https://www.youtube.com/watch?v=5xVBi8Ulnic
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Victory!!
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Brian,
I have been following along and am a little perplexed. You built the engine and it ran fine. At that point you put it on the shelf only to be taken down to power your edge sawing machine, but it wouldn't run.
I don't mean to play the devils advocate here but what on earth happened from running to all the things that were required to get it rerunning?
Curious minds want to know!
gbritnell
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Very happy to see that you finally succeeded :cartwheel:
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George--I think it was a voodoo curse. Well, not really. If I had pulled the heads off and lapped the valves a bit more FIRST I probably wouldn't have done all the other things. When an engine runs well and gets put up on the shelf for a few years, then doesn't run properly when you get it down off the shelf, you start eliminating possible causes. The engine had spark. The engine had fuel. The engine refused to run properly. I pressure tested both cylinders with compressed air thru a fitting screwed into the sparkplug hole, and they seemed to hold pressure adequately. I did every "easy" thing that I know how to do to make the engine run properly, and none of them worked. At that point it was either abandon the project or start digging deeper. For whatever reason, this engine seems to be very very particular about the valves sealing 100%. Ah well, it's January and I don't have a whole lot going on anyways.---Brian
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:cheers: we ALL knew you’d figure it out. Congrats. :ThumbsUp: :ThumbsUp: :popcorn:
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Brian,
Woohooo....and I'll tip one to a running engine. :DrinkPint:
Art
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I have restored the hand built carburetor to the engine, and it is running much better. I have decided that the engine would benefit greatly if I were able to manually adjust the ignition timing while the engine was running. The points will now mount to the red plate with the red handle. The red plate rotates on a central boss on the gear case, and by loosening the green capscrew I can advance or retard the timing to find the "sweet spot" where the engine runs best.
(https://imagizer.imageshack.com/img924/4558/gKGwGI.jpg)
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Brian, you may want to alter that so that the long red screw also acts to loosen/trighten the bracket then you don't need two hands to adjust things. Another option is to add a spring or friction washer under the cap head screw so you can just move the bracket by the lever but it won't move due to vibration.
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That is a good idea Jason. I may put a spring washer under the head of the socket head capscrew.
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I had three grandchildren sleeping over and a sick wife, so I've been running around like a chicken with it's head cut off today.--Did manage a couple of hours this afternoon to whittle out the "Timing plate". The points shown are an old pair that I keep on hand for "set-up" purposes. The brass bit in the center will actually be attached to the front of the brass gear cover. When I have the handle attached to the timing plate, this will allow me to tilt the plate in one direction or the other, to the limits of the curved slot, to adjust the timing while the engine is running.
(https://imagizer.imageshack.com/img924/5540/EU0LIR.jpg)
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Here we have the timing plate and handle installed on the engine. The concept is that you set the ignition timing as close as possible with the plate mounted as shown in its neutral position.Then, when the engine is running and warmed up, you loosen the bolt that is in the curved slot, and this lets you rotate the plate and points mounted to it a few degrees clockwise or counter-clockwise. This retards or advances the ignition timing until the engine is running in it's "sweet spot", then lock down the bolt in the slot.
(https://imagizer.imageshack.com/img922/6677/j7VJJX.jpg)
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Brian,
I did a similar thing on my Upshur engine. I put the points on a round disc with a I think 20 degree slot in it. The back side has a step that fits into the hole bored in the crankcase, keeping it in that same radial plane. With the screw holding the plate in place.
(https://i.postimg.cc/k5rWQGrN/DSCN2392.jpg)
This is the best photo I can find.
Art
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I haven't ran of with the gypsies, nor anything nearly as exciting. I've been plugging away on this engine, correcting faults and trying to get my head around a few things. Like Bob Seger's song, "Nightmoves" I've been "Working on mysteries without any clues." I've had everything apart right to the bare bones and built it back up again, checking clearances and tolerances. I have no problem starting and running the engine. The problems are inconsistencies in the way it runs each time. Some of the new features I've added cascade. I added the manual ignition timing plate and lever, and it works fine---but it eats up 1/4" of clearance on that side of the engine. The answer to that of course, was a new pulley and starter hub, with an annular slot on the engine side 1/4" deep to fit over that #10-24 bolt head that holds the ignition points in place. I have eliminated everything that would potentially cause a problem except for the cams themselves. They are a direct copy of the cams Malcolm Stride used on his "Bobcat' and "Jaguar" engines. I made the single cylinder "Bobcat" engine with enough changes to rebrand it the "Canadian Cub", and although it ran satisfactorily it also shot vapour out the mouth of the carburetor while running. I ordered a new set of "Rimfire" sparkplugs yesterday from Roy Sholl at S & S Engineering. If I decide that the duration of the cams is too great and is causing the vapour discharge from the carburetor, I'm not sure if I will go so far as to make new cams or not. When I first built this engine, I didn't put any key in the starting hub and crankshaft on that side of the engine. The engine ran so well and with so few problems that I thought I would get away with it. Of course, it has came back now and bit me on the arse, because with all the messing around trying to change this engine over to a "Throttle governed" style, the starter hub was slipping on the crankshaft. So, this morning I broached a keyway into the starter hub and set the entire engine up on my mill table with the crankshaft locked against rotation and milled a new keyway into the exposed end of the crankshaft. The saga continues-----Brian
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Today we have some good news and some bad news. The good news is that the trouble with the right hand cylinder was indeed the sparkplug. I haven't got my new plugs from Roy yet, but I did discover a 1/4-32 sparkplug in one of my other older engines and used it to replace the sparkplug in the right-hand bank. The engine now runs fine. Who knows!!!---It might have been the bad sparkplug that was the problem all along. The bad news is that the engine doesn't want to accelerate while under load. The governor and linkage works exactly as I had planned. When I spin the engine over with my electric drill, the governor weights immediately fly out, closing the throttle right up to the adjustable "stop", the engine starts, and everything runs fine. When I put a load on the engine, the governor reacts exactly as I had planned. The engine slows down, the tension spring pulls the weights of the governor back to center, the linkage opens the throttle. BUT--then the engine stalls. If I engage the load very slowly, sometimes the engine will keep up, but nine times out of ten the engine just stalls out and quits. I more or less know why, but I'm not sure what I can do about it. In a conventional "old style" automobile with a carburetor, when you step on the gas to open the throttle, the accelerator pump squirts a stream of gasoline directly into the carburetor throat to keep the mixture from "leaning out" which would cause the engine to stall. In my miniature carburetor, there is no provision for an "accelerator pump". If I richen the mixture to my carb by unscrewing the needle valve, the engine won't run at low rpm. If I start the engine under load, it will run, but it doesn't like it. The vapour coming out of the carburetor throat has lessened considerably, so that may have just been a function of running too rich and having a bad sparkplug.
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Have you got an adjustable air bleed on your carb, plenty of model engines use them to give a richer mixture at lower revs and tick over. Look at The Nemett one if you want something to copy.
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HI Brian,
Quite some time back when you were getting into your I.C. Engine designing and building one of the contributors (Chuck Fellows comes to mind but I might be wrong) came up with a simplified carb design which had a needle valve and throttle barrel but no air bleed. At the time you built one and said that it worked fine. I commented that in my experiences with I.C. Engine carbs I didn't know how they could work properly without an air bleed circuit. For engines with a somewhat constant RPM they will work fine and even throttle up with seemingly no problem except that the fuel mixture from slow to fast speed is really a compriomise. Now that you have an engine that needs a more regulated mixture control because it's working under a load I suspect that the fuel curve is way off. The air bleed part of the carb is like the low speed circuit on a regular carb and allows you to adjust both the low speed and high speed mixtures to a more proper air/fuel ratio.
I suspect in all your building endeavors you have a model airplane carb laying about. If so I would try adapting it to see if it cures the off idle performance.
gbritnell
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I think I am going to "throw in the towel" on this project. I've spent two months working on it, with a few successes, but more failures and I've nowhere more to go on it. I will still wait until I get my two new sparkplugs from Roy Sholl and try the engine with them, but if I don't see a world of improvement, I'm going to call it quits. It has been an interesting but frustrating project, but I haven't been able to make it work the way I had hoped. Ah well, nothing ventured, nothing gained. I will offer this word of advice---If you design any kind of i.c. engine, don't put the sparkplugs at the bottom of a horizontal cylinder. I run a bit of two cycle oil with my naptha gas fuel to lubricate the Viton ring, but what I'm finding is the oil separates out in the cylinder and constantly fouls the sparkplugs. These engines don't run hot enough to burn the oil when running at low rpm. And yes George, I have been trying it with a 4033 Traxxas carburetor on it, but it doesn't seem to help a great deal. Thanks very much to everyone who has followed along.---Brian
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Brian,
Although frustrating, at least for me, I think that trying to solve a problem is a big part of a build. When I built the flathead engine I had around 2000 hours of design, drawing and building. The first spin of the starter got it running but that's about all it did. I ended up experimenting and making 2 more sets of heads, another intake manifold, modifying the distributor, going through 6 Hall transistors and heaven knows how many more little changes and tweaks before I got it running the way I wanted. If you feel your head design is causing a problem remake them. A good friend, Ron Colonna, built a Novi engine which took untold hours to complete and it wouldn't even start. It sat on the shelf for years until he finally persevered and got it running. A lot of people see these engines running at a show and think that the parts were made and assembled, gas and ignition were added and away they go but don't realize just what goes into getting them to operate well, sometimes well! If you shelf it now you'll always wonder what that little thing was that it needed to succeed.
gbritnell
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Good morning Brian,
I agree with what George said, but no matter what you choose to do in my view your build was inspiring and a pleasure to follow. You have a very creative mind and outstanding machining abilities and I have enjoyed following along on all of your projects, so keep them coming :ThumbsUp: :ThumbsUp: :ThumbsUp:
Have a great day,
Thomas
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Hi Brian
I’ll agree with George, but state that not all of us have George’s patience. :embarassed:
You might want to set it aside for a while and move on to something else, then go back to it later. That has worked for me with several of my more difficult projects/problems.
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Okay--I spent the morning on a redesign of the cylinder heads. IF I decide to go ahead and do this, it would move the sparkplug up to a point above the centerline of the cylinder. It would mean new heads, and everything in them. That is a lot of work.--Then again, I don't have a lot of other stuff going on. The only thing that makes this a somewhat attractive notion, is that I have all the material here to do it without having to buy anything. I will think on this for a while---
(https://imagizer.imageshack.com/img924/3135/gqKGd8.jpg)
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I hope you don't give up, Brian. Though can understand taking a break, frustration being what it is.
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After posting the previous 3D model, I went up to the mall for my "fat mans walk". As I walked along (four times around the mall is 1.6 miles) I was running thru this design in my head, and realized that the axis of the rollers that contact the top of the valve should be parallel to the rocker arm pivot pins. so--A slight change to the shape of the rocker arms corrects that issue, and actually makes for a simpler rocker arm.
(https://imagizer.imageshack.com/v2/1600x1200q90/923/dpHLoF.jpg)
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Fouling/oiling of the spark plugs on the bottom cylinders is a problem for radial engines. It looks like you are developing quite a neat design for your new cylinder heads :ThumbsUp: :ThumbsUp:
Flexible carburation for small engines has always been a problem. If the engine is driving a propellor it is not too bad for as the speed drops the load drops with it. For a land based vehicle it is more difficult as the load can increase as the speed drops, starting to climb an incline for example. ETW put a lot of work into a compensating carburettor for the 1831/Wallaby engine.
Many people build steam powered locomotives and traction engines but very few build IC engined ones with self built engines, most seem to use commercial engines. Maybe carburation is part of the problem :headscratch:
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Here we have two new cylinder heads, which almost entail a full days work. Notice that the sparkplugs have been moved a lot closer to the side of the head which the manifolds bolt to, which places them high above the bottom of the cylinder bore. I still have to make valves, valve guides, rocker arms and brackets but I'm happy with these. I never noticed how dirty the business end of that sparkplug was until after I had taken the picture.
(http://imagizer.imageshack.us/v2/1600x1200q90/921/o5T2fH.jpg)
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All that in one day? Busy day!
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This mornings offering to the machine Gods is four brass valve cages. These cages get Loctited and very lightly pressed into the cylinder heads. The 0.125" thru hole and the 0.25" hole are both put in in the same set-up to guarantee concentricity. The one on the left was about .002" undersize so I knurled it lightly, which increases the diameter by about 0.010", then turned it down to the correct dimension. After the Loctite sets up (preferably overnight) I will use my George Britnel inspired valve seat cutting tool to put the 45 degree chamfer in the area where the valves seat.
(https://imagizer.imageshack.com/v2/1600x1200q90/924/TWNPpL.jpg)
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one of my BMW motorcycles was duel plugged to help with the compression vs available pump octane issues,, the added plugs on the bottom of the heads always had more problems then the upper plugs,, always had a spare set under the seat..
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Wow, that was quick work!
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Bent--I find turning, drilling, and boring or reaming operations do go very fast. I use the auto-feed system on the lathe as much as I can, and just watch the numbers on the DRO.---Brian
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I'm very happy to see you're sticking with this Brian, no doubt in my mind that you'll get it all worked out.
Excellent work as always,
Watching & learning,
John
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Thanks John. I spent the afternoon making the main bases of the rocker arm support brackets. Tomorrow I will have to build a welding jig to hold all of the vertical legs of the brackets in the correct place before silver soldering the brackets together.
(http://imagizer.imageshack.us/v2/1600x1200q90/921/RHZ23u.jpg)
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Besides being impressed with the engineering, machining and stick-to-itness in this thread, I also enjoy the pictures taken of components and assemblies with books.
Going to rip that idea off as a presentation method.
Cheers, great work all round as usual. Glad to see you staying the course.
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Thanks Stuart. --It's good to be making parts. I can only fart around trying to make these things run right for a limited time. This throttle governed engine is one of those situations where my experience says it should work, the theory and physics say it should work, and all of the components have been built on other engines and they did work. Before I can make the "throttle governed" part work, I have to get the basic engine to work right. This makes me a little crazy, because when I originally built this two cylinder engine, it did work just fine. :pinkelephant: :pinkelephant:
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Brian, you may want to look at Pete's 4cylinder "Puma" version and how he dealt with the oil issue which is mostly what is thrown up from the crankcase not what is in the fuel
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Thanks Stuart. --It's good to be making parts. I can only fart around trying to make these things run right for a limited time. This throttle governed engine is one of those situations where my experience says it should work, the theory and physics say it should work, and all of the components have been built on other engines and they did work. Before I can make the "throttle governed" part work, I have to get the basic engine to work right. This makes me a little crazy, because when I originally built this two cylinder engine, it did work just fine. :pinkelephant: :pinkelephant:
This is why this hobby is so fun, right? Right? As a newbie, I need some reassurance here - this *is* fun, right??
No, I'm not serious - I have experienced the hair-tearing frustration of something that refuses to work for no good reason ... and the bliss of discovery, achievement, and victory when finally getting the #%$! thing to work.
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Just had a very valvey morning. I leave the long end unturned to act as a handle while I am lapping them. Then I drill the cross holes,then I part off the handles.
(http://imagizer.imageshack.us/v2/1600x1200q90/923/mislWB.jpg)
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So, the valves, valve cages and valve spring retainers are finished. The valves have been lapped with #320 then #400, then #600 lapping paste and have been match marked to their specific place in the heads so that I don't mix them up. I'm coming down to the exciting strokes now. I will first design and build a fixture to hold all of the parts of the rocker arm bracket in the correct relationship and silver solder it together.
(http://imagizer.imageshack.us/v2/1600x1200q90/924/tTLsh9.jpg)
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This should make a good welding fixture to hold all of the rocker arm bracket parts in the correct relationship for silver soldering.
(https://imagizer.imageshack.com/v2/1600x1200q90/923/GgD4aH.jpg)
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I am getting worried about your books Brian you seem to be getting oil and dirt all over them :disappointed:
Jo
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Don't worry Jo, all the books are bought and paid for. I end up with so much junk piled up on my side table that I need to use a book to give a somewhat clean background for the picture I'm taking. That particular book was given to me by the engineering head of Volkswagen Canada about 30 years ago.
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Brian,
I guess I have been in my own little world as I see I have been out of touch for a bit. I remember when I first got my Upshur engine running, but it wasn't right so I called my dad knowing if I described how it ran he'd know what was wrong. And just as quick as you can snap your fingers he says timing's advanced to much retard it. It was off three teeth. Now I know enough to set the timing with an indicator on the rockers. So what am I doing that's distracting me from the important things in life, I am rebuilding that same engine. Drawing stuff up in CAD that I didn't have when I originally built it. That and life is getting in the way, work has been very busy and this is the slow time of the year. It is good to see you are working through the problems that are confronting you on your twin. I think you will have an even better design than the original, and it will have no problem running your saw rig.
Art
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Hi Art--Nice to hear from you. I'm plucking away at this thing just to have a way to get thru the winter. The existing cylinder heads are fine except for placing the sparkplugs in the worst possible position for oil fouling. Now this really matters on an engine with horizontal cylinders. However, for a vertical cylindered engine they would be perfect. I am making all new parts for the new cylinder heads, not robbing any of the old parts. ---I see a 3 or 4 cylindered motor in the future using these two existing cylinder heads.---Brian
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This picture shows the finished welding fixture. (Remember, it doesn't have to be pretty, just functional). The brass pieces which will be silver soldered together are bolted into place and are ready for soldering. If I have lived right, the fully soldered assembly will be easily removed form the welding fixture, and the pieces for the second brass rocker bracket will fit into it for soldering.
(http://imagizer.imageshack.us/v2/1600x1200q90/923/x2JMss.jpg)
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First soldered assembly removed form welding fixture and ready for cleanup. The fixture survived just fine, and tomorrow I will make the same soldered assembly for the second cylinder.
(http://imagizer.imageshack.us/v2/1600x1200q90/922/6uR8vK.jpg)
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Everything fits like the 3D model says it would. Not a lot of spare room, but a miss is as good s a mile. Tomorrow I will make up the hardened rollers which bear against the end of the valve stems, and the axles that the rocker arms pivot on.
(http://imagizer.imageshack.us/v2/1600x1200q90/924/PscY3W.jpg)
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Nice progress Brian :ThumbsUp:
And I really hope you get completely on top off the problems with this solution :cheers:
Per
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The new cylinder heads are completely finished and assembled. Everything fits, but there isn't very much real estate left anywhere. For those who were wondering, the compression springs are made from 0.020" wire, and are purchased. The valves are lapped and held in place by circlips. The next move will be to remove the existing cylinder heads from the engine and install the new ones.
(http://imagizer.imageshack.us/v2/1600x1200q90/924/Oq8gBM.jpg)
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All of the moving components could probably have been made of aluminum. Aluminum weighs almost exactly 1/3 of what brass weighs. I was limited to brass for the bracket, because I don't have the equipment to weld or solder aluminum. Would the difference in the way the engine runs have been measurable?---Probably not, at the speed I am asking it for. The original heads were aluminum, the original rockers were steel, and the original knurled adjusters were brass. The new heads are aluminum, the new rockers are brass, and the new knurled adjusters are mild steel. The engine in it's original form ran very well, but there was always a problem on cold starts--oil would separate from the fuel and foul the sparkplugs, because they were right at the very bottom of the cylinder. I'm not reinventing the wheel with these new heads, All I'm doing is correcting what I determined was a design flaw. I haven't dismantled anything from the old heads, the design flaw only appeared when the cylinders were horizontal. The old heads may get re-used on a new engine with multiple vertical cylinders.
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Brian, you could have cut the new rocker supports from a single piece of aluminium quite easily, only really an issue if you were putting the engine into a plane model.
do wonder if the weight of your adjusters may reduce the ability to stay in contact with the rods as the speed goes up, are they really needed as the cap head screw can be turned by hand or if you are using smooth sides screws change to ones with the straight knurl.. Or simply make from 5/32" steel and put a fine knurl on the "head" and use a ball endmill in place of the hex hole. Screwdriver slot on the top would also work if you have fat fingers. Ditto the bulk of the rocker arms.
4mm version of what I describe above
(https://img.photobucket.com/albums/v156/jasonballamy/Engineering/Midget/DSC03875_zpsnc9pqpyc.jpg)
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reducing the weight of the moving parts of the valve train might be worth doing,, making sure you are keeping free play in the valve adjustment is important to the running of a flat twin..having been a BMW motorcycle mechanic since the mid 80's, the 81-84 were the first engines to see problems with unleaded fuels, the selection of valve seat material caused valve deformation,, loss of free play,, first symptom loss of normal idle speed,, adjust valves idle would return.. changes in seat material and valve angle grind were the long term repair.. keeping proper free play at all times is very important..making sure the valve springs don't have to do more work than needed..
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People have been asking about the relative size the engine is that I am working on. Canadians don't use pennies anymore, so the only closest thing I could find for a visual comparison is a matchbook. In this picture, I have my adapter screwed into the sparkplug hole and 50 psi on the air hose. No leaks at the exhaust pipe nor the carb air intake. Having established that cylinder as being okay, I will now move over to the other cylinder and perform some magic over there.
(http://imagizer.imageshack.us/v2/1600x1200q90/924/EiYQPF.jpg)
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I had an interesting day today. I went to a heavier valve spring of .038" wire diameter. These are beefy little buggers. Too strong to compress with my thumbs and slide the locking collar into place. I had to figure out how to make a spring compressor. Honestly, I have never used any springs that are over 0.020" diameter on any of my engines. The "lift" on the cams for this engine is just a bit more than 1/16". The coin is a Canadian $2, called a "Twoney"--that name was derived form the 1$ coin issued a few years ago that had a loon on one side, so of course it immediately got named a Looney!!!
(http://imagizer.imageshack.us/v2/1600x1200q90/922/fsichH.jpg)
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Combustion chamber hasn't changed at all, other than the location of the valves and sparkplug. Biggest change of all was the shape of the rocker arms. They went from simple "straight' pieces of steel with rollers on the center to the new ones with the cantilevered rollers at the end. In test mode, with the adapter screwed into the sparkplug hole, the cylinders sealed up tight up to 50 psi. of air pressure No leakage of air out the exhaust pipe nor out of the carburetor throat, nor past the rings. The valves sealed great under "test" conditions, but engine had no (or very little) compression when cranked over. Nothing gets past the Viton o-rings, no leaky head gasket. Conclusion is that the valves aren't seating properly. They are lapped, and do seal under "test" conditions but not in normal "start the engine" mode. Normally, if I can get an engine to fire at all, the force from igniting fuel will force the steel valves against the brass seats hard enough to make a perfect seal. Tried to start it already, and there simply wasn't enough compression for the fuel to ignite. It's rather coincidental that Boomer has been talking about valve springs.--That is where I ended up going anyways as that's about the only thing left to try. Ignition and valve timing hasn't changed since the last time I had the engine running. I can push the valve off the seat, against the new spring pressure when gripping the head between my thumb and finger. It is noticeably harder to do that now, but my cams, lifters, and rollers on the rocker arms are all heat treated 01 steel. I did have to make a spring compressor, because it is very finicky work trying to get the spring compressed, the keeper in the right spot, and the c-clip on without something to compress the spring and let me work with both hands. The push-rods are 1/8" diameter about halfway up their length, then are reduced to 1/16". I will probably make new pushrods tomorrow that are 1/8" diameter over the full length.
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I haven't installed the head with new springs yet. I'm ready to go, but I want to mount a 0.060" spacer under the rocker arm bracket but wife isn't up yet. This has become my morning routine. Wake up, get dressed, make a coffee, then head down to my computer and look at the forums to see what everybody else has done.---Quietly. My bandsaw is out in my main garage right under her bedroom. I am going to saw the spacer out of 1/16" plate, and the bandsaw makes a Hell of a racket. I'm putting the spacer under the bracket to raise it up 1/16" because as you can see in the picture, clearance between the adjusting bolt in the end of the rocker which adjusts the valve lash is uncomfortably close to the head of the bolts which hold the intake and exhaust flanges in place.
(http://imagizer.imageshack.us/v2/1600x1200q90/924/5SpHuz.jpg)
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There is no joy in Mudville---I have no good news to report. The engine is reassembled with my new cylinder heads (the uber strong valve springs are only on one of the cylinders). With my adapter screwed into the sparkplug holes, the cylinders both hold 60 psi air pressure, with no air escaping past the valves. I have tried to start the engine and it isn't happening. I even went so far as to set it up on my bench and drive it for half an hour to see if that would seat the valves a bit better but it didn't seem to do anything. I am going to go out today and buy a socket and pigtail for a 12 volt bulb and wire it up through the points so I can get a really good concept of the ignition timing. I will also do one more check of the valve timing. This time I will check valve timing on both cylinders. The cams are made as four individual components and Loctited to the camshaft. I doubt very much that they have spun on the camshaft, but I will check it. I know a thousand things to check for on engines that won't run, and I've used up 998 of them. If this engine doesn't run after a final ignition and valve timing session, it's going up on the shelf. I have an idea for a new and different engine in my head that I would like to spend some cad time on, and I'm ready to move on.---Brian
(http://imagizer.imageshack.us/v2/1600x1200q90/922/yzGIT7.jpg)
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Brian. You’ve been working hard on this and I really feel your pain. You need an “engine buddy” to step back and ask the right questions, like, “is it plugged in?”. I have a good friend I can turn too when this happens to me and I can give him a visit and he usually comes across with something I hadn’t though of. I’d be lost without him.
I wish you well. Start thinking “outside the box” and maybe the problem will surface. Good luck my friend.
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Okay--An update. this afternoon I checked and reset the ignition timing. I even wired in a 12 volt light thru the ignition points so I could see exactly when the points opened the circuit. Stuck a hex wrench down the sparkplug hole and turned the engine over by hand, one hand hanging onto the hex wrench which was in contact with the top of the piston and the other hand slowly turning the vaned flywheel. I didn't really like the ignition timing it was set at, so I changed the timing a bit until I was happy with it. Then I slowly turned the engine over by hand , still hanging onto the hex wrench, and got a good reading of when the intake and exhaust valves began to open. That was right, so I then moved over to the other cylinder and repeated the act. Valve timing was good on that cylinder too. So---the cams haven't slipped on the camshaft. Tried to start the engine, and it didn't start, however the right hand cylinder was puffing smoke and getting warm. The left hand cylinder was too (that's the side with the heavy valve springs) but not as much as the right cylinder. I put new fuel in the tank, although I don't really think that Naptha goes bad with age. Tomorrow I'm going to set the engine up on the bench and drive it with the electric motor, until it flies or dies. I'm not going to work on this anymore. Now, an observation::--This is fairly important. The crankshaft has bronze bushings on it, not ball bearings. There is some runout on the crankshaft, but not much. The thing is, and you'll have to believe me on this---If there is any runout AT ALL on a crankshaft, it's going to squirm as it rotates in the bushings which support it. Consequently, the bushings will be worn away on a taper on both sides of the bushing centerline. Then it is only supporting the revolving crankshaft on a thin "line of contact" in the center of the bushing, which quickly wears away. The result of this is sloppy fit between the crankshaft and bushings. This won't prevent an engine from starting, but it will clunk and clank while running, and if your ignition cam is supported on the crankshaft, the points gap will not be stable. HOWEVER---And I wouldn't have believed it if I hadn't seen it---A single race ball bearing will tolerate a small amount of squirm without damage to the bearing or the shaft. I have found this out by my own personal experience, and will never again build an engine with bushings supporting the crankshaft. Again, on a 4 cycle engine this will not keep the engine from running. It will screw up a 2 cycle engine because a squirming crankshaft will quickly wear out the crankshaft seals and the crankcase will no longer be "air tight". That's it folks. I'm done with this. If the engine does decide to run tomorrow, I will shout "hurray" and post a video of it, and tell you all how clever I am. If it doesn't, it will go up on the shelf and stay there.---Brian
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Brian as you are not getting leaks with your adaptor in the spark plug hole but lack compression when trying to start have you checked the plugs are sealing? maybe a new copper washer as they deteriorate if you keep taking the plug in and out. Bit of soapy water around the plug as you turn the engine over may show. any leaks.
Those strong springs will just add to the load the engine needs to overcome to be able to run on it's own, The one I got going the other week has 0.4mm wire on the inlet and I will probably change that to 0.3mm when it goes back together after painting as it feels a bit too strong.
As for bearings maybe try to build a non squirming crankshaft.
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Some tricks I have learned:
Hold a flame over the exhaust whilst cranking the engine. If the flame can't ignite anything nor can the spark plug.
Rest the sparkplugs next to their holes whilst hand cranking the engine and see if they really spark when you think they should.
Try different sparkplugs if you can, although I can't see both of yours failing (I think that you may have tried this already)
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I took the super heavy springs out today and put the 0.020" springs back in. Fiddled and farted around all day with no success. I have to move on and leave this project.
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Brian does the ignition fire the engine on every (just before) TDC or every second ?
If the later is the answer - please check that it doesn't fire on the exhaust stroke instead of the compression stroke .....
Sorry to hear that this will not be a success for you.
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The ignition points are driven from the crankshaft, so it fires every time the piston comes up to top dead center. Both cylinders fire every revolution, but there is only a charge of fuel in each cylinder every other revolution.
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Brian, are you running a single coil and no distributor?
Might be a case of you getting one spark per rev and that spark will only go to the easiest route not to the cylinder that needs to fire. Would also explain your plugs oiling up if they are firing less than they should.
The CDI that I used on my similar Bobcat based engine has twin coils with a plug lead from each so you get a spark to each plug.
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My coil is off a two cylinder snowmobile. It has two leads and fires both of them simultaneously on each revolution of the crankshaft.It has an unusual spark path. The spark travels out one wire, jumps the first plug gap, then goes thru the engine frame and jumps the second sparkplug backwards, then returns to the ground terminal.
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Hi Brian,
I know you are really frustrated with the engine but here are some of my thoughts.
The engine ran fine when it was built and put on the shelf. When you decided to use it for the board trimmer, nothing changed. It was taken off the shelf had modifications made to it in just the carburetion and governor setup. It ran but didn't have the control you wanted. So all the other elements of I.C. engine function remained the same, coil, spark, compression and the timing was fiddled with making it adjustable. None of these things should have altered the way the engine ran. You made completely new heads to move the spark plug location. This wouldn't have affected the engine running.
Carburetion can be finicky but even an out of adjustment carburetor will work to some extent.
If all the elements are there, fuel/air, compression and spark there's no reason for the engine not to make an attempt at running.
My best guess is the ignition. Here's what I would do. Take the spark plug out of one cylinder. Hook up a single fire coil to the points and just fire the other plug. (one cylinder engine) The engine should make an attempt at running. If this works do the other cylinder. If that works I would guess that the snowmobile coil isn't doing it's job. Roy Sholl sells a dual fire ignition setup and I have one on my V-twin engine. My V-twin has a waste fire ignition and the ignition system works well.
gbritnell
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With the path for the spark plugs going through one to the other then out, is it possible that there is a short in one (or the path) so it is not making the journey? When you swapped in the light bulb, were the two plugs and all the normal wires still in the circuit? If so, this is not it. If not, that could be a possibility.
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My coil is off a two cylinder snowmobile. It has two leads and fires both of them simultaneously on each revolution of the crankshaft.It has an unusual spark path. The spark travels out one wire, jumps the first plug gap, then goes thru the engine frame and jumps the second sparkplug backwards, then returns to the ground terminal.
When you added the adjustable contact variation did you keep the contacts isolated from the engine frame? If not then there could be a new path to ground. just a thought
Bruce
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Yes, i'm getting good spark at the plugs.
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most bmw airhead engines run 6-9 degrees before TDC for timing at idle..full advance at around 22-25 degrees before TDC(3000 RPM),, with a retarded timing at idle they most often will not run..advanced timing at idle they run fast (other problems occur through the RPM range)
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Hey--Check this out. Somebody just sent me a picture/model of a new engine being built in China.--Nevermind--I can't post the image. Somebody in China is building and marketing my Rockerblock engine.
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Would help if you posted the picture
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For cases like that, I've found saving the image to my PC, then posting from that source (scaling down if needed) works.
Imitation may be the the best form of flattery, but theft of ideas calls for an angry hungry shop gnome stuffed down their pants....
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here you go, this is the image that Gil posted
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I'm setting here laughing my ass off at the thought of some Chinaman with an angry, hungry elf shoved down his pants.
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:lolb: :ROFL:
Art
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After much work and many failed attempts to run the "throttle governed engine" I have reached a conclusion. There were no real flaws in the self governing mechanism. The flaw was that I couldn't get the basic engine to run properly. The new cylinder heads with the sparkplugs moved didn't really help. The ignition cam on this engine mounts onto the crankshaft. The crankshaft rides on bronze bushings that have rapidly worn out, due to the crankshaft not being perfectly true with no runout. The slop in the crankshaft bearing lets the crank move around enough to screw up the gap in the ignition points. I have put the engine up on the shelf, and at a later date I will remake the main crankcase and design it so the crankshaft and camshaft both ride on sealed ball bearings. Sealed ball bearings, surprisingly, will tolerate a bit of run-out in the crankshaft, and are not harmed by it.
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Though annoying - you at least discovered why you got those problem, and that is very valuable :ThumbsUp: