Recent content by Ringsnapper

Something I should have mentioned in the previous ‘achieving compression’ rigmarole was the alignment of the valve guides. In the Gypsy heads the bronze guides are an interference fit, pushed into the top of the heads, so there is possibility for misalignment. A small misalignment would clearly...

2. The copper washers that came with the spark plugs were a sealing nightmare. I just made new ones in the end. With these two issues taken care of the leakage rate dropped dramatically but still not holding pressure. 3. Air was whistling past the valve seats. Using the screw head technique...

Thanks. One subject that often arises with cylinder heads is their ability to hold pressure so I thought I’d leave a note based on my experience with the Gypsy. My last project (the Chenery V twin) was fraught with issues trying to get compression, and it turned out the main issue was the...

It seemed that the drawing leaves some of the geometry of the exhaust porting to the builder to figure out and it was that triangular arrangement that cost me at least one or two attempts before I got it so the there was clearance for the head bolt in that corner and the port lined up with the...

‘A little while later’ …..I finally get around to the cylinder heads and boy did I underestimate the work needed to get them finished. There is a lot of machining on these guys and ample opportunity to mess up. These were the final four out of about ten attempts, though two of them didn’t get...

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...