Throttle governed engine

[Brian Rupnow]

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---

[Roger B]

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.

[Brian Rupnow]

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.

[Brian Rupnow]

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.

[Art K]

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.
Art

[Allen Smithee]

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

[Brian Rupnow]

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.

[Brian Rupnow]

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.

[AlexS]

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.
<a href="https://www.youtube.com/watch?v=v7GLQU-0Nwc" target="_blank">http://www.youtube.com/watch?v=v7GLQU-0Nwc</a>

[Brian Rupnow]

Hi Alex--I'm hoping for a test run this coming week. Will post a video.---Brian

[Brian Rupnow]

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

[scc]

Very nice work Brian,    I'm still quietly following along.               Terry

[Brian Rupnow]

Hello Terry--Glad you've come along for the ride.---Brian

[Brian Rupnow]

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.

[Brian Rupnow]

And finally, there's my baby with the new starter hub-pulley installed. Room on the pulley for two 1/8" O-rings.