Hello fellow experimenters!! This episode I plan to finish the valve linkage which is the last machining step before I can test the engine. I have been working on this project during every free moment the last 8 weeks so it would be nice to know if the thing is going to work or not :oP
The valve linkage includes both the upper and lower valve rods as well as the linkage “knuckle” which allows the eccentric to drive the valve. The “knuckle” (for lack of better words) is built from a piece of 3/8” square brass. I will be putting my own “spin” on the design of the knuckle just to warn those who are faithfully following the prints ;0) I first started out by machining the “female” side of the knuckle on one end of the 3/8” brass. I located the center of the wrist pin and then centered that mark in the central axis of the rotary table. The center finder tool was quite useful for this task.
The next step was to drill out the wrist pin hole with a “undersized” 1/8” drill bit as seen below. The undersized hole will hold the wrist pin captive later on...
The next step was to contour the end of the knuckle round. The rotary table was used to “spin” the workpiece against a “stationary” milling bit.
Next, a 9/64” hole was drilled into the side of the knuckle to define the end of the slot that will form the “yoke” of the knuckle. This hole was placed at .4” from the rounded end of the piece to the center of the hole.
The next step was to remove the material in the “slot” of the yoke with a “slitting cutter”. The cutter was set up in the mill at the desired height off of the table while the table was traversed past the spinning blade. Notice the layout marks on the yoke....
The width of the yoke gap ended up being around .145” wide...
I decided to machine the male side of the knuckle on the other side of the bar so that one parting cut could be made to separate the two pieces later on. I started the male side by centering the pivot point in the central axis of the rotary table.
I drilled the pivot hole out with a 1/8” drill bit as seen below.
The next step was to mill out one side of the “shackle” to match the female side. I used a 3/8” end mill to cut out the one side. Notice the layout mark on the piece below....
The next step was to contour the end of the shackle....
I flipped the piece over and cut out the other side of the shackle. The thickness of the shackle ended being about .143”.
I parted the two pieces exactly in half (about 1” long each) with the bandsaw (not shown) and then slid them together for a fit check :0)
The next step was to drill out the valve rod holes and oiler hole. Yes it’s true :0) I am adding an oiler to the knuckle. And while it’s quite obvious that this part does not need an oiler I thought that it wouldn’t hurt to add a grease cup/oiler to the design for good measure.
I aligned one end of the knuckle in the table vise with a precision square in preparation for drilling...
I then drilled the end with a 3/16” (slightly undersized) drill bit for the upper valve rod end. I drilled the hole to about .375” deep.
The next step was to drill a 1/16” hole through to the pivot hole in the center of the valve rod hole. This hole will pass the oil from the oiler cup to the wrist pin.
The hole for the 5-40 grease cup was now drilled into the top side of the male end at about .575” from the rod end (right side). I used a #38 (.1015) drill to meet up with the 1/16” oil hole made earlier (I was careful not to drill into the rounded yoke pockets by accident).
The 5-40 tap was hand-fed into the hole using the mill’s chuck to keep it straight.
You can see the oil hole in the photos below and how it connects to the oil cup threads.
The next step was to drill the 1/16” roll pin hole into the male half of the knuckle. I installed a 2.6” long piece of the 3/16” brass rod (upper valve rod) into the rod hole of the knuckle. I then drilled an 1/16” hole at about .225” from the square end of the piece as seen below. The hole penetrates through the entire assembly. Note: the plans call for a 2.5” long upper valve rod. I cut mine a little longer as my knuckle parts are larger than the plan suggests to build them....
Before installing the 1/16” roll pin into the knuckle end I applied some blue Locktite to the rod and then reinserted it into the knuckle. The roll pin was then tapped into place with a small hammer. Note: The Locktite will seal the backside of the valve rod and keep the lube oul from leaking out later on...
The female side of the knuckle was now drilled and pinned just as the male side was. I used the remaining piece of 3/16” brass rod for this connection. Notice the black dots below, they were used to keep the pieces oriented correctly to each other as the pieces were apart for the application of the Locktite....
Now the next step is purely aesthetic. I decided to taper the inside of the knuckle ends with my lathe as seen below. I tapered the ends to about a 20° angle...
And now the finished parts!! Not too shabby ehh???
And now it was time to install the upper valve rod into the valve itself. I mounted up the valve into the table vise (using copper jaw inserts to protect the valve) and then installed the upper valve rod into the valve. The roll pin hole was drilled out and I installed the last roll pin (not shown).
I installed the valve to see where the lower valve rod would need to be bent to align with the eccentric. I marked out my bend centers and removed the rod for modification.
I made a bending jig by clamping two 1/2” hardwood dowels into my bench vise as seen below. The pegs were used to form the brass rod by acting as a pivot point for the rod to “break” on.
The last step was to thread the end of the lower valve rod for the 10-24 adjustment jamb nuts. I used a hand die to carefully thread the rod making sure not to get off-center with the die.
Now that the machining was basically done I could assemble the parts for a final fit check. I used the supplied 1/8” steel pin to join the two halves of the knuckle together.
I installed the grease cup into the knuckle with a little Locktite to hold it in place.
And last but not least, the adjustment jamb nuts were installed on the eccentric yoke as seen below. The final adjustment of the valve including timing will be done when I get the engine running...
I now have the basis for a running engine at this point. All I have to do is cut out my paper gaskets and plumb my engine to run on compressed air. I can then see if the project is a success or not. Please join me again for the next episode of the 6CI project and see if this thing will turn over or not :oP
