|After the first couple of runs, I realized quickly
that the 15 X 8" Graupner prop was waaaay too small
for this engine, and did a bit of internet research to
find suitable replacements. The problem with most cheaper
hobby props is that the hub of the larger propellors can
be molded hollow, which interferes with the 4 hold-down
bolts needed by my prop system. I found some pictures of
the Czech Mejslik props and was fascinated. These are
top-quality propellors made of braided carbon fiber in an
epoxy matrix, and had a very unique appearance, as well
as being quite light. I ordered an 18 X 10 and a 16 X 11.
The 18 X 10 came pre-bored for a perfect 10mm shaft,
while the smaller prop would have required boring, so the
big prop was used.
With the new prop in place, the Sony camera was set up to record the event for posterity. Here they are! The files are quite large.
|crank.mpg - 1.8 mB||I am still using my leaf blower for now. This is an excellent system, plenty of air, and makes for fast, cool starts. Oddly, I guess the frame rate of the mpeg cannot keep up with the prop, as during the crank, it seems as if the prop is stuttering. Rest assured it is accelerating smoothly. I have the ECU set to idle at 50,000 RPM. At this speed, the prop turns at 2,300 RPM.|
|upto125.mpg - 1.1 mB||The turboprop is being accelerated from 50K to 125K
gas gen RPM. In all these videos I am being gentle with
the throttle, not yet wanting to explore the accel/decel
capabilities of the turboprop.
At 125K gas gen, I am turning the 18 X 10 3-bladed prop at 6.8K. The turboprop is absolutely smooth, yet there is a feel of enormous power. Not too much prop noise at all... the Mejslik prop tips are designed to minimize this. I have my foot on the back of the workmate. LOTS of wind!
In all honesty, even at this relatively sedate RPM, the whole thing is a bit scary! Hopefully I'll get used to it.
|upndown.mpg - 1.6mB||
Some gentle throttle movement, first up to perhaps 110,000, then down.
frntshot.mpg - 543K
|For these videos, I dismounted the camera from the
tripod and am doing my best to film with a transmitter in
one hand and the camera in the other. They are a bit
wobbly but give a different perspective.
The throttle is set low, and with the workmate stable in this situation, I can move around a bit. I am not as close as it looks because of the zoom feature!
Overall, these runs were the best by far! The new prop is a winner. The EGT went up slightly, but generally was happily low, in the mid 500's for most throttle settings. The prop blast at high throttle settings is astonishing. As I mentioned before, it is almost scary in its power. This engine demands respect in its operation. I personally wouldn't want to attempt to control it manually, and believe an ECU to be of great benefit.
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