Navy Commander Dave Leonard showed up today at SZP to show the TTC
guys what a rotary looked and sounded like in the air and to see the
TTC engine. Dave has 880 hours on this airplane and has practiced at
Reno at 230 MPH. No race as that was the year of the P51 disaster.
I had an idea that we could measure the HP by using platform scales
to measure the prop torque.
Dan Gray loaned me a set.
The jury is still out. With the wings rocking like that the readings
varied all over the map.
If the data could be sampled and captured by a computer one could
average the data and it might then work but I doubt it. That was not
the case here. One had to quickly read the LCD's and write down the
numbers.
Another factor is the helical slip stream over the wings. One wing
has one angle of attack and the other a different angle of attack.
That would seriously affect the readings.
Not worth doing but we learn from ideas that don't work.
The movie was 5050 RPM and 37" of HG. Dave's 3 blade prop is about
68" in diameter and 80 pitch. Ironically this is about what we are
getting on the TTC engine with an 82 inch dia. and 66 pitch prop.
However the TTC engine still has that 1.25 inch diameter hole in the
exhaust manifold. I can't wait to try it with out the hole. I think
Jim M put the hole in there to protect the engine in case we screwed
up on the cooling installation :-)
I suspect this is the chart of what the TTC MAP should look like with
out the hole. The numbers are absolute KPas.
BTW discussions I had with Dave and some data from OMC indicates the
stock wear rate on the stock iron apex seals is around .001 inch per
hundred hours. That is .010 inch per 1000 hours. That means you might
need to put new apex seals in about every 1000 hours. I suggest
biting the $1200 cost bullet and put in Iannetti Silicon nitride apex
seals when you build the engine in the first place. The TTC engine
has them. The projected life is then 20,000 hours for the apex
seals.
Be sure you use Teflon encapsulated oil scraper O-rings. Dave's
engine is smoking when he starts it up. A sign that the oil scraper
o-rings have melted. This is not a real problem as I drove my Cosmo
for at least 100,000 miles with melted side seal O-rings. 300,000
miles total. I mentioned this on the web site.
http://www.rotaryeng.net/O-ring-size2.html
The side seals are also subject to wear but Silicon Nitride side
seals are not yet available. Once that is done a turbo four rotor
would be a potent competitor for a P&W PT6.
The four rotor would be half the weight and 85% of the fuel burn.
Much less fuel burn even than that... in a turbo compound
configuration. The PT6 is almost all steel accounting for the high
weight.
Paul Lamar
I would think that with a way to record the data that the results
could
easily be averaged and converted into a meaningful torque reading. The
buffeting didn't look that severe.
Gary Knutson
Yes that is a possibility. If I had time I could dope out the schematic of
the solid state wiring interface and build a computer interface using a
Maximite
to record the data 10 or 20 times a second and store it on a micro SD card.
I could write the program in five minutes :-)
Maybe I can get a schematic for the scales on the Internet.
I think this is it.
http://www.mktechnologies.com/products/other/longacre_accuset_II_1100lb_scale_system_72582.htm
I sent them an email asking them for the pin outs on the scale.
Paul Lamar
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