5.7cc Glow Engine
I bought myself a model diesel engine a while back, a PAW35. The fuel for them is notoriously hard to get hold of simply because glow engines are so much better. I found it out of a box, stripped the engine down, gave it a good clean and attempted to start it. The fuel was about 7 years old but I did eventually get it started, I can understand why glow engines are so much more popular. I had broken one of the engine mounts off a few years back and I managed to break the other one off trying to start it. My project is to make a new crank case and modify the cylinder head to accommodate a glow plug.
I first started out by measuring the crank assembly and putting it onto paper. I decided that I would be able to make it out of 2 inch aluminium bar, so I offset it in the lathe and ran a clock down it to ensure it was running parallel.
The bar was bored out to accommodate the crankshaft, everything but the cranks shaft is imperial, luckily it measured 12mm and I happened to have a 12mm reamer. I turned a thread inside of the bore so that an end cap could screw into it.
The bar was ready to be parted off so I first clocked a jaw parallel with the cross-slide, I then used a boring bar to score line across the front, this is so that I had a centre point to work from when it comes to milling. The packing used to offset the bar was removed and the outside was turned, the remainder of the bar was parted off and then faced.
The jaws in the vice were clocked to ensure they were parallel to the bed on both the top and face. I used the score line to true the whole setup in the vice, this is the only part of the process I cannot do accurately.
I progressively milled it down, firstly profiling the engine mounts.
Some holes were drilled for the carburetter, the cylinder liner and the bolts to hold the cylinder head down.
Further milling and the crank case is almost complete.
The holes were tapped that hold the cylinder head down and mounting holes were drilled. The carburettor was such a good fit that I did not even have to use a grub screw to hold it in place. A large flywheel was made, 50mm diameter and 20mm high from mild steel. A large flywheel will keep momentum going and allow me to tune the engine a little easier, it's also a lot safer than a propeller.
The existing cylinder head had the internal step turned out and a total of 5mm was shaved off it's height. The existing thread for the compression screw was drilled out and then tapped to suit a glow plug, a little recess was turned so that the plug would seat right. A total of 6.8mm was turned off the cylinder so that I would get a compression ratio of 9:1. I was surprised to find that the cylinder was made from hardened steel and not cast iron like I would have expected.
The cylinder head mounting holes were drilled larger to suit the new bolts, the whole lot was then assembled.
The cap for the crank case was made and I tested it in the engine. It screwed in nicely but aluminium on aluminium is not a good idea and I managed to get it stuck, so instead I set the engine up ready for running. The engine did start and did rev up quite high but the glow plug I had was too cold to sustain running at low rpm and by mistake I knocked my power supply which turned the voltage up blowing the plug.
Another plug was placed in the engine, a medium one this time and then the engine was started.
Hello, if you have enjoyed reading this project, have taken an interest in another or want me to progress one further then please consider donating or even sponsoring a small amount every month, for more information on why you may like to help me out then follow the sponsor link to the left. Otherwise you can donate any amount with the link below, thank you!