Timing the Trevithick Dredger Engine – 1. theory.
The plan is this…
- Finish constructing and installing all of the components, including gaskets, seals.
- Install a pressure gauge, in a temporary position. Trevithick did not have pressure gauges available, but the current model boiler regulations insist on one. So my plan is to have one installed eventually on the base, out of the viewing public sight, but where the operator (me) can see it. For the purposes of the timing, which requires some pressure in the boiler, the gauge location will be on top of the boiler, but moved to its final position later.
- Install a fitting to admit compressed air to the boiler. And a valve to adjust the flow and turn the air on and off.
The lever with the hole controls the entry and exhaust of steam into each end of the cylinder. (The other handle is the throttle.)
The timing is adjusted by removing material from the blocks above and below the lever. The blocks were made, deliberately, a few millimeters too long.
I will put some compressed air into the boiler, at about 20psi, and slowly move the lever until I hear air entering the cylinder at each end. The lever position at which air enters each end of the cylinder will be marked and measured. Then the blocks will be machined or filed to the correct length. I will assume that if the entry point is correct, then the exhaust will automatically be correct.
That’s the theory.
I have started making fittings for the pressure gauge and air couplings, and hope to get to the timing in the next day or so. I will also be checking the pressure at which the safety valve lifts. I will be aiming for 55-60psi.