Throttle governed engine

[Brian Rupnow]

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.

[Brian Rupnow]

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---

[Brian Rupnow]

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.

[Brian Rupnow]

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.

[Brian Rupnow]

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.
<a href="https://www.youtube.com/watch?v=mcqcSWhOrcI" target="_blank">http://www.youtube.com/watch?v=mcqcSWhOrcI</a>
<a href="https://www.youtube.com/watch?v=2xwvOKc0aAA" target="_blank">http://www.youtube.com/watch?v=2xwvOKc0aAA</a>

[Brian Rupnow]

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.
<a href="https://www.youtube.com/watch?v=0rqDEkB6KNE" target="_blank">http://www.youtube.com/watch?v=0rqDEkB6KNE</a>

[crueby]

That is very interesting to watch, seeing the lever moving as the speed varies.
Great!!
 

[Brian Rupnow]

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.

[Ye-Ole Steam Dude]

Hello Brian,

Great job on that throttle and the motor sounds real good.

Have a great day,
Thomas

[Brian Rupnow]

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.

[Brian Rupnow]

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.

[Art K]

Brian,
The twin runs great, all your modifications to make the throttle governed part work great.
Art

[Roger B]

Excellent progress     

I can outweird that  Whilt walking in the snow covered mountains my wife and I came across a dog with snow boots and sunglasses  The owner was positive that this was necessary as he wore snow boots and sunglasses 

[Brian Rupnow]

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).

[Brian Rupnow]

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.