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Decided to keep going with the oil pump casting and complete all it’s machining just in case there is a hidden gotcha that might hold things up. Ready to assemble the oil pump. So the bearing for the magneto drive shaft was completed along with the cross shaft. The 90 degree helical gearing...

In the quest to get the sump, crankcase and oil pump fitted together I needed to complete the crank shaft which meant get the oil ways blanked up where needed , cut a key way for the 15 tooth gear and generally fit the bearings and end caps with properly sized shims. A bit of skimming on the...

I’ve never tried casting with lost wax, the burnout procedure always seemed long and complicated with temperature profiles etc. to get the wax out and dry the plaster sufficiently. I guess the original Chenery castings were lost wax. I finally got around to fitting the lower half of the crank...

Yes can’t wait to get started on the heads. Just an update on the crankcase casting. I’m hoping to fit the oil pump to the crankcase so I‘m working on the various gearing for the cam, timing, and oil pump. Most of the spur gears and the helical gears I found as stock items in the HPC Gear...

Sure, I don‘t see any issue with you adding your experiences to this thread. I would suggest that if you have an extensive build story it might be best to start afresh as this thread has already rambled along over a number of topics for some time all be they Gipsy related. Your choice though.

Very nice. Yes that is what is indicated on the drawing using 8BA screws. I hadn’t seen the screws on the full size engine because most references to the Gipsy Moth show the later 120hp mk2 version which utilized a different arrangement. I’m tempted to get a copy of a Gypsy 1 engine maintenance...

Well to be fair to Les Chenery although I didn’t spot any cam bearing fasteners in the side wall of the crankcase in any model engines, I did find a real example of a Gypsy mk1 that appears to have some type of visible fastening at the right places on the crankcase adjacent the cam.

Thanks for your thoughts on this. In fact the drawings call for securing the cam lobes in position on the cam shaft using loctite. The cam shaft isn’t submerged in oil but is constantly splashed by oil from the crank throwing it about the casing. I’ll try shrink fitting the bearings first...

A bit more work on the crankcase and spot facing for the front cam bearing. The casting is a healthy 0.25 in thick here. Aside from the ends there are three internal bronze bearings for the shaft, essentially rings that sit in the crank webs. The drawing shows they are to be held in place by...

As it turned out there was an issue with my ‘final‘ casting which meant another go at it. The tenth try. The bore for the crank shaft is 0.625” and is counter bored to 0.875” at both ends. At the front bearing the counter bore extends 0.375” into the casting. I had not allowed enough depth in...

l worked on the ‘shrunk‘ casting a little more and drilled through for the cam shaft. All seemed well but I realized the foundry that produced the original casting I am now using as a pattern made the gear housing dimensions exactly to the drawing dimensions. This means I need to enlarge...

Yes, that’s the plan. I’d like to get the crankshaft bearings drilled as well as the camshaft. Then I can mock up the gearing at the rear of the engine and check the gear housing for clearances etc. Obviously the crankcase casting shrank in width as well as length, I measured it as about 0.035”...

I bored out the casting for the cylinders and right off the bat hit a snag. The new casting shrank in length by 0.075” overall with each of the cylinders about 0.025” closer together. So on a fixed 1.6 inch spacing on centers they become misaligned with the raised cylinder seat features on the...

So just by way of an update to the Gypsy casting saga. I have increased the amount of aluminum I can melt to about 6lbs which is more than enough for this casting. At this point I‘ve had four goes at it. In the first one, shown below, there were some areas the metal did not completely flow. The...

Thanks GreenTwin, very interesting comment on the CO2 exposure time. I started out worrying that the gas wouldn’t get into the cores enough and left them in the bag for hours. Then wondered why they fell apart under their own weight. Since then I’ve generally not been as concerned about the...

Step 2. Place the crankcase pattern into the impression in the sand. Step 3. Pack the sand around the pattern with sprue and vent. Separate the two halves of the mold , pull out the crankcase pattern and place the cores in position using the indents from the step 1 template. . Check the core...

The top case requires four cores. The middle two are identical but there are some differences in the two end ‘bays‘. Notably there is an undercut to the front crank bearing housing on the right that the oil fill passage connects to from above. The pattern shown above is based on the original...

Spent some time recently preparing an attempt at a home casting of the upper gypsy crankcase. The first step was to modify the original casting to avoid the external feature issues. I filled in some areas at the rear of the casting and blocked up the holes for the cylinders, leaving them...

Thats interesting, I didn’t know Hemingway ever sold the Gypsy castings. I built the Aero V twin from them. I wonder if they also tried to recreate them from the drawings and got similar results.

By way of an update on the Gypsy castings. I contacted the originating foundry to ask if it was possible to modify the patterns and try another run. It’s been about 10 years since the original casting so I was not overly hopeful but they did reply and asked for details on the modifications...