Horizontal Air Cooled Engine

[Brian Rupnow]

Having a very wimpy day here in the great white north. It has snowed here all day and I haven't been outside. I did a little tidy up work on the cylinder head and the rocker arms, and added a screw to the base to mount the condenser. Other than chasing down an 8mm sparkplug and making rings, the engine is completely "built". I have successfully made and ran cast iron rings in my last two or three i.c. engines, and now I will pull out all the notes I made with respect to 1" diameter pistons and see if there are any real changes to make rings for a 7/8" bore engine.

[Brian Rupnow]

I ordered an M8 A.C. Delco sparkplug this morning. Cost $14 delivered. I will post a picture when it comes.---Brian

[Brian Rupnow]

Paging Steve Hucks---Hi Steve--I am currently building an engine which takes a spark plug with a 1/4"-32 thread. Unfortunately, I screwed up the threads in the sparkplug hole. I don't want to have to remake the head, so I have to either find a sparkplug with a 5/16" thread or build my own custom sparkplug. I much prefer to buy a plug, but haven't had much luck finding one with either a 5/16" thread or a 8mm thread.--Do you sell anything like that, or have a link to where I can buy one.---Brian Rupnow

[Brian Rupnow]

I have spent the last two days designing some light automation for an old customer. My new sparkplug will be here on Saturday, and if it doesn't have an 8mm thread I am going to buy a 1/4"-32 helicoil kit from a source provided by Brian Lawrence from Calgary. Tomorrow I will begin the task of making rings for a 7/8" diameter piston. I have the grey cast iron material, but will have to build a new heat treat fixture to accommodate the new ring size. The rings will have the same cross section as the ones I made earlier this year for my T-head engine.

[Brian Rupnow]

Todays job was to make a whole armada of 7/8" rings. The material is fine grained grey cast iron, same as I made my other 1" rings from. The o.d. of the ring is turned to 0.875" diameter and polished with 200 grit aluminum oxide strip and a fine India stone, to the best finish I can get. The i.d. is drilled and bored out to leave the rings 0.038" wide axially, which is what I was aiming for.  The rings are then parted off, and with some luck will all be slightly greater than 0.045" width, which is the width of the ring grooves in my piston. They will be finished on both sides with some 600 grit aluminum oxide paste on a sheet of glass, rubbing round and round until they are a sliding fit into the ring grooves in the piston. After they are "sized" for width, I will break them in my bench vise. I don't like the fancy fixture which I made to split them because it has a tendency to bend the rings. The last rings I made were cut with a sharp cold chisel, but I felt that doing that deformed the ring on both sides of the cut.

[Brian Rupnow]

Okay---Just to set the record straight---My rings came off the lathe about 0.003" to 0.004" too wide (as I had planned). I tried polishing that 0.003" to 0.004" off using 600 grit compound on a piece of glass, but it took so long I thought I might not live long enough to get all the rings done.---So---I used a sheet of 600 grit paper laying on a finished cast iron surface, and my handy dandy piece of steel with a 0.875" dia. x 0.025" deep hole in it to hang onto the rings with while I polished them. That went more quickly, but even so it took a lot of scrubbing in circles before the rings came down to 0.044" thick and would fit into the 0.045" grooves in my piston.

[Brian Rupnow]

This was something new---The material didn't want to break in the vice. Damn stuff wanted to bend, which is unusual. When I seen that it didn't just snap quickly like other rings  have made, I sharpened up my big cold chisel and cut them with the chisel and a pall peen hammer. Whack---and it was done. All the rings in this picture are finished, deburred, and split. Tomorrow I will machine a heat treat fixture and into the heat treat oven they go.---Brian

[Brian Rupnow]

A couple of picture worthy things going on here. One picture shows a good way of filing the ends of the ring at the ring gap. That is an ignition points file gripped in the vice, and a ring spread over it. I grip the ring with thumb and forefinger of each hand and slide it back and forth on the file, keeping it "square" to the file. Give it 20 strokes and try it for fit in the cylinder--You are aiming for a gap of 0.004" between the ring ends when the ring is slid into the cylinder. Keep track of the number of strokes you take, because whatever it took for that first ring will work for all the rest of the rings. The other picture shows the heat treat fixture I machined this morning, made specifically for 7/8" rings. The drawing I am working from specifies a 0.131" diameter spreader rod. Closest I had was an 0.135" drill, so thats what I used, and the drill will be sacrificed as my spreader rod. Once the cap is bolted on, compressing all of the rings to ensure that they are all laying flat and tight next to each other, the fixture and rings go into my heat treat furnace for 4 hours.

[Brian Rupnow]

Bad on me---I ordered an M8 sparkplug from A.C. Delco, assuming it would have an M8 thread on it.---it doesn't. It has a 10 mm thread on it. However, all is not lost. As we speak, Stephen Hucks is making me a "one of" sparkplug with a 5/16"-24 threaded end. As luck would have it, I do have a 5/16"-24 tap and die as part of a set I inherited from my dad.

[crueby]

This chart may be of future help - shows thread sizes for a number of brands. The NGK section, row E, shows an M8x1 thread size.
https://www.gsparkplug.com/identifying-spark-plugs
Chris

[Brian Rupnow]

After four hours at 1100 degrees F and then an overnight cooling off period, the fixture comes out of the oven looking like this. There is a lot of black crud on the outside of the fixture (Don't know what it is) but it cleans off very easily. When the fixture is taken apart, the rings come off easily, but they are all stuck together. A bit of finessing with a jacknife gets them apart, and as you can see in the picture they have all taken a set to the new gap of 0.135".

[Brian Rupnow]

The rings are on the piston and the piston is back in the engine, and everything goes round and round and up and down like it's supposed to. Out of 8 rings four were damaged, two are on the engine, and I have two left over for some other project.---I would not recommend  putting new rings on a new piston to anyone who was looking for a way to pass a tranquil afternoon. There is no cylinder head on the engine right now, but it does have lots of "suck" when I put my hand over the cylinder and turn the engine over with the flywheels.----thats a good thing!!!!

[Brian Rupnow]

The engine is basically finished. I'm just waiting for a new sparkplug from Steve Hucks. In the meantime, this things needs a gas tank. I've built about a zillion round gas tanks, but this time I decided to try something a bit different. I went out into my "junk steel closet" and found a piece of 1 1/2" square tube. It will be the basis for my new rectangular tank, and I have a piece of 3 1/2" x 1/2" aluminum flat bar that will make a good sub base to hold the engine and the gas tank.

[Brian Rupnow]

Got this far today, and just run out of ambition. Tomorrow I will finish the gas tank and the sub base.

[Brian Rupnow]

Today the gas tank was assembled. There is a lot going on here that you can't see, but the ends of the tank are assembled to the body using J.B. Weld. The tank assembly is bolted down to the sub base, and the big vice grip clamp is on there as  secondary means of clamping things tight for the next 24 hours. The sub base has had all of the holes added to hold the engine and the gas tank. Tomorrow I will leak test the gas tank, and if all is well I will paint the gas tank and the fan assembly.