Engine Update

As I said in my last post, the engine is up on the bench for some much needed repairs and upgrades. The first order of business was to fix the pulled out cylinder post. No big deal there, just some drilling and tapping for the bolt and backing plate (essentially a big washer). With that done, it was on to the water pump.

The pump you can see in the bottom left of the picture to the left. It's that long brass thing. Its a positive displacement gear pump, which should mean that no matter the speed, it will still pump water, and put some pressure on it as well. That's the theory anyway. In actual practice it needs to be going around a bit faster than once a second, which is the engine's approximate speed. But how fast?

To figure it out, I took it off and hooked it up to an electric drill, then put a gauge on the outlet end and had it pump water. To get a consistent 30 lbs took about 600 rpm, or ten times around in a second. That was the limit to the gauge I had on hand. Needing 40+ lbs I figured 900 rpm would be more than enough to overcome the pressure and pump water into the boiler. So I built a gearbox out of some sprockets and chain I had around. The result is what you see in the pics.

For those of a mechanical bent, The ratios are 2.4:1, 2.5:1, and 2.5:1 for each linkage giving a total ratio of 15:1. So for each time the main shaft turns, the pump shaft turns 15 times.

The pic on the right is the back side of the gearing and you can see the three linkages. The sprockets on opposite sides of the mounting block are connected to a joining shaft and turn on center together.

There's quite a bit of mechanical loss in doing it this way, but it was quick and relatively easy. I would have preferred to use spur gears, but that would have been a lot more machining than I have time for at present. Perhaps for the new engine.