As I said earlier, most of what I've been doing was small steps which were taking up more time than expected. This posting documents some of them.
The modified linkage for controlling the cam and flywheel assembly changed quite a few of the dimensions given on the plans. This required making few adjustments along the way. The photo below shows the foot which opens the exhaust valve during the engine's freewheeling mode. This action is what makes a hit and miss engine "miss". With the exhaust valve held open it can't deliver any compression.
That odd silver ball on the front of the cam was not there for decoration only. It served as a pivot point for the catch arm that holds the valve foot down. This piece was supposed to be installed much earlier in the build, but I didn't like the original design which called for a piece of 1/8 inch flat bar. Once the foot was installed, I had to come up with a custom arm to fit the new linkage. This photo shows what I came up with.
If you look closely you'll see a small rod has been added to the slide linkage This rod is the remains of a broken cobalt drill bit and is where the arm catches the linkage when the gear cam is activated... assuming the governor is at full extension. As a side note.... you might want to know that drill rod (silver steel) and cobalt do not solder very well at all....so green Loctite was used to secure the joint.
Here is the completed linkage assembly. For the curious, take a little time to study the relationships between all the components and the operational sequence of the little engine will begin to reveal itself.
With the front side of the engine completed, that free swinging end of the crank shaft needed attention. The plan is to mount a small water pump behind the engine body and drive it with an eccentric mounted on the shaft. In order to accomplish this, the shaft had to be stabilized. A place to mount the pump was also on the list of things needed. The bushing was installed and the face of the piece was turned to "fit" the large opening in the rear of the base. This will let me use it to mount he pump as things progress.
While it doesn't look like much of a step, this piece had me sweating a bit. When a shaft is supported at two points, as this one has been until now, you have little chance of binding. When that same shaft is supported at 3 points, things can begin to bind in a hurry. Even a slight misalignment will cause problems. The large hole in the base is centered at 1.812 inches from the bottom of the body. This is also the location of the hole center in the front support where the points are located.
Since the body is contoured and lacking any abundance of reference points I had added one the plans never called for. That small flat spot you see in the photo below was a god send. I was able to us it to help square the work piece when it had to be put back in the mill vise. More than once it saved my bacon and is now one of the tricks that is being used regularly on other projects.
By using the flat spot, a DTI and my now much beloved DRO, I was able to nail the 1.812 inch measurement perfectly and mill the slots for the plate into the round body at exactly the right place.
The photo below shows the pump in its early stages. The bore is 5/16 with a 3/4 inch stroke. The plunger has been made and fitted with its o ring and the water hammer chamber is fitted. You'll see flat spots on the upper section which I mentioned above. Since the area will be removed when the pump gets its end cap, they won't interfere with anything. The simply make it easy to keep things square.
Here is what it all looks like at the moment. The mock up fuel tank is about to be replaced with the real deal and the round mounting plate and wooden plinth are almost ready for final finish and the pump build is well under way. The ignition system should be here next week and hopefully the first test firing will also be made before next weekend. Lots of little items to finish tying down and still more polishing to be done, but the project is quickly coming to completion. Keep those fingers crossed that the darned thing will run....LOL
Steve
