Graham's Economy build

[Graham P.]

After a few weeks of deliberation I decided to build an Economy engine from Engineers Emporium. The casting arrived just in time for the long weekend.
I cleaned up the lower surfaces for the base and cylinder and was able to blue it up and check the major dimensions.
First job is to bore the hole for the liner in the cylinder this will be then used to fix the height of the crankshaft.

[Jo]

That casting looks very clean Graham. Was there much flashing on it when it arrived?

Jo

[Graham P.]

Hi Jo,
There was a lump on the bottom of the cylinder that took a bit of filling off. Other than that, just a quick rub with the file removed most of it. It still needs to have the mounting lugs on the base cleaning up.
Graham

[Graham P.]

I've been working on the bore for the liner. I decided to follow other builders and turned a plug that served as a gauge and then was used to align the casting with the spindle on the mill. A second plug was then used as a gauge for the slightly smaller rear bore.

[Graham P.]

A quick update on my progress.
The bearing caps are done. Currently working on the cutout for the timing plate and building a fixture to hold the casting on the saddle of the lathe to bore the holes for the main bearings.

[propforward]

Looking good Graham. Keep it going!

[cnr6400]

  great progress on the engine!

[Graham P.]

This weekend it was time to bore for the main bearings. I've been planning this for a number of weeks as to which was the best way to attack it. I decided that the lathe was a better approach rather than my small mill. With the centre height being fix, the only way I could mount the main casting was vertically. I purchased some ground aluminium plates from Poland that took around a week to arrive. The first was 25mm thick and mounts to the saddle. The second was smaller and 15mm thick and is mounted on an angle plate and bolted to the casting.  Some 8mm and 10mm holes were drilled in both plates for fixing.  The plan being that these plates will be kept for future projects where large castings need to be mounted to lathe for boring operations.

I made a couple of tools in advance as I knew that once I started I had to continue to end without breaking down the setup. The first was an extension to hold a centre drill at length from the chuck and the second was a between centre boring bar, as I wanted to run this through both bosses once complete to check that both were the same size and true.

I had already spotted the location of the bore using the DRO on the mill. Using some shim material I carefully set the centre on the spotted mark on the casting. Using an indicator to check that the casting true both left to right and front to back. It took a while and I think I got there within 4 thou.

I then opened up the left boss with a series of drill up to 25mm.  Then I passed my extension bar through this and spotted the right boss. This was then opened up the same as the left boss to 25mm. To be honest I think I could have stopped here, but to be sure I passed the boring bar through both sides. It appears to have taken the same amount of material of both sides, suggesting that both sides were the same.

The last picture shows the build so far, with the timing plate in place.

Next job is the main bearings.

[crueby]

Well done, I really like the way you did the extension for the center drill, have to remember that one.

[Roger B]

That's coming along very nicely   

[Graham P.]

The last few weeks I've made the main bearings, a relative simple turning job on the lathe. Cutting the groove that sits over the bearing brackets took a bit of care. As must people have reported they are 17mm rather than the 20mm on the drawing, I kept the total width of 23mm with more material left on the sides.

Next task was the keyway slots on the crankshaft. Turned out to be a simple milling job. I switch my mill to high range and ran it at 2800 rpm, running a 3mm slot drill down the crankshaft until I got to 2mm deep. Then I opened it up + / - 0.55mm so that the supplied key was a snug fit.

The supplied crankshaft webs were bored out to suit the crankshaft and crank pin.

Next in line: Turn the crank pin down and the split big end bearing.

[Graham P.]

The split bearing was made in the same way as other builders.
The blank was machined and then split into two. The two halves were soft-soldered back together before being machined to final size.
I had seen a builder who choose to silver solder the two halves together, rather than the more common method of soft solder. I had problems with mine coming apart during the final machining, not sure if it was due to the part getting too hot due to aggressive cuts or a dull cutter.

[Graham P.]

DON'T MAKE THE SAME MISTAKE AS ME.
Anyone starting out on a new build, don't fall into the same trap as me with the crank gear.

I remembered seeing in the plans that you should not drill the 1.6mm hole for the contact until assembly. But I didn't understand the importance of that statement and would actually go a further and say don't drill any holes.

I machined the two recesses in the gear and thought it would be an ideal time to drill the 3 large holes and the small 1.6mm hole for the contact. I even set the DRO for 6 hole PCD pattern so I could get the hole exactly between to large holes. I then shrink fitted it to a bush that had been shrink fitted to the cam. Only when discussing my progress on a Facebook build group that the significance of the instruction about not drilling the hole sunk in!

Unlike other engines I had built, where you could adjust the timing of the engine by rotating the cam, I had gone to a lot of trouble to firmly fix the cam to the crank gear.

You live and learn. I will have to wait to the engine is finished to see where I should have drilled the hole for the contact and then deal with it then.