Test of the Flight Works, Inc. Model 100 Pump;
With the Mejslik prop installed and proven, the next phase of testing included installation of the smaller of the two pumps, the model 100. Even though I had made the entire TurboProp assembly as modular as I could, it is still a bit of a chore to replumb. After a couple of hours of effort, I once again had the prop jet off of its base and partially torn down for maintenance. The old Hausl pump was removed, and replaced with the model 100. While I was at it, I changed the oil and checked for overall wear. Everything looked fine... gear train backlash was still its original ~ 3.6 to 4.0 mm at 18" on the prop blade. With the gears bedded in, everything rotated very smoothly.
|Back on the stand and ready for the trial run with
the new pump. The new prop really looks cool and was very
easy to adapt to the turboprop.
The setup for this run was the same as before with the Hausl pump; 7.2V 1100 mAH NiCD battery through a 5 Bears ECU. The pump will be throttled between 0 and 7.2V with 10 bit PWM, frequency of 4.8 kHZ.
In this picture, the pump is installed on the right beneath a protective aluminum shroud. A single filter is placed between the pump's output and the fuel manifold. The fuel supply is additionally carefully filtered before fueling into a 1.3L tank.
The new rocker switch is evident, replacing the old toggle which was a bit too close to the left exhaust for comfort.
With everything ready, I began the start process. First, the system was primed, and the prime pump setting was stored into the ECU's EEPROM memory. A voltage of 0.96 was enough to tick the pump over with my particular plumbing and cause a very slow advance of the fuel into the manifold. Your results may differ a bit depending upon tank head pressure, etc.
External air was used for start. With the turbine idling perfectly at a gas gen. RPM of 50,000, the pump voltage was 1.4V. Even this small difference in voltage (prime vs idle) was easily handled with 10-bit logic, allowing the ECU to zero in upon (and track) 50,000 RPM without ratcheting or overshoot.
For this run, I limited the Gas Gen. RPM to 125,000. At this speed, the prop is turning at 6,800 RPM, and the pump is powered with 3.7V. Obviously, there is plenty of room for more power, both with gas gennie and prop RPM. Extrapolating (an educated guess here) to 160,000 would create a pump voltage of 4.6 to 5.0V.
Overall, the pump performed perfectly. The increased resolution over larger "Speed 280" sized pumps is very welcome, allowing one to avoid chokes, bypasses, or any other goofy system to restrict pump output for smaller turbines, as well as a large savings in weight and space. Acceleration and deceleration were very smooth, due again to the larger voltage range between idle and max throttle.
When the turbine is next torn down, I am going to try fitting the model 200 pump to act as the oil pump rather than the heavy, bulky Orbit pump.
I can highly recommend these pumps for MW54-sized turbines, with the smaller pump being more than adequate to power an MW54 with a 4 to 5 cell pack.
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