Test run 17 Nov 2000 Cone off

Reeking of kerosene (mmm kerosene!) even as I type... The last week or two has been spent working on (and calibrating) the test stand with the cannibalized fish scale transducer from Wal-Mart. In the end, it was a lot of work but I beleive it was worth it. It was not a simple matter of connecting a trolley to the transducer, because unless the engine pulls on the transducer in a purely axial fashion, the weight measurement will be low. I confirmed this by mounting a tube into the stand and via a pulley arangement, loaded the tube (simulating the engine, diameters were the same) with a known 5 lb weight. With the old linkage, the 5 lb weight produced a 3.5 lb reading.

The linkage was redesigned so that when mounted on the exact engine centerline, the 5 lb weight produced a correct 5 lb measurement.

Please wait, LOTS of photos to load...

The ground support box in its finished state. The box carries a 12v battery for all supporting items, and a 7.2v NiMH battery for the pump. Seen here are the case pressure guage, white master switch, red pump switch, the 10-turn "throttle", the LCD readout from the fish-scale, and a deluxe LED EGT readout.

The really sad part is that after all the work, I took the box outside for the run and discovered the EGT meter is totally washed out by the sun! I didn't even think about that. I'll need to find an LCD-powered EGT meter to replace it.

The final test stand. Note the spark plug, which works so well that I removed the glo-plug from the other port and plugged it with a SS cap.

I am using some Legris quick-disconnect micro-couplers. These are extremely slick, and function exactly like full-sized shop air tool couplers. My understanding is that Legris sells a bunch of these to dentists for their drills.

The quick disconnects are set up on the air tap (blue) and the gas tap (bottom). Lube is left, and fuel, right.

A closeup of the thrust measurement linkage. Buried beneath the nose of the engine is the variable-length arm which pulls against the thrust transducer. The big ring in the middle is a simple clamp which can be adjusted up or down... this varies the leverage exerted on the transducer, and allows me to calibrate the stand.

In the foreground is a lever operated cam which allows me to remove the engine's thrust from the transducer to allow resetting the scale to zero. A flick of the lever foreward releases the carriage for thrust measurements.

Once again, the engine behaved perfectly, started easily, and had no bad tendencies at all! The recordings below were done on a cool (10C) day, unknown pressure.

Also on this run, I checked the minimum case pressure I could idle at, and found it to easily idle at 1.5 PSI. Below that, the EGT began to creep up a bit.

Earlier, I had a table of thrusts posted here on this page which was erroneous. To see accurate thrust measurements, click here for both cone on and cone off data.


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