Hi MIke
That is quite a thought re: RPM testing. We do indeed have the same
frequency here. Though I believe the frequency spec. is much much tighter
than 2%. I used to balance large fans using strobe equipment etc. to
measure phase angles of the out of balance fans etc. Same principal. I
could give that a try. I guess I better not try that inside with my hangar
door shut if I can't wait for nightfall! (Just kidding).
Thanks for your thoughts.
Brian #328R
-----Original Message-----
From:
murphy-rebel@dcsol.com [mailto:
murphy-rebel@dcsol.com]On Behalf Of
Mike Kimball
Sent: Friday, March 29, 2002 10:21 PM
To:
murphy-rebel@dcsol.com
Subject: RE: Sensenich prop 74 x 58"
Poor man's way to check the tach: Put a little piece of duct tape on the
back of a prop blade, wait for the sun to do down, then position the
airplane with one of the airport flood lights behind the plane. In the USA
we have 60 cycles per second AC power (plus or minus no more than ~2%
usually). The light will flicker at that rate even if you can't see it. (I
don't know if Canada might be 50 Hz.) Set the rpm at factors of the power
cycle rate. For instance, set 1800 rpm for 60 Hz power. At 1800 rpm the
prop with the tape on it should appear to stop. If it stops at something
other than 1800 rpm, that is how far off your tach is. If it stops at 1700
rpm, it is reading 100 rpm low. (You need the tape because most props are
painted black on the back and would be harder to see.) The prop should
appear to stop at all factors of 60, such as 1200 and 2400 rpm as well as
1800 rpm.
Mike Kimball
SR#044
-----Original Message-----
From:
murphy-rebel@dcsol.com [mailto:
murphy-rebel@dcsol.com]On Behalf Of
Brian & Pat Cross
Sent: Thursday, March 28, 2002 4:46 PM
To:
murphy-rebel@dcsol.com
Subject: RE: Sensenich prop 74 x 58"
Hi Robert
Thanks very much for your info. I am going way over the engine red-line
assuming my tach is correct. I am going to get my tach checked somewhere.
Static rpm is at least 2500 rpm. I can go over 2700 rpm at 12,000
feet...something Sensenich thought would never happen.
I will pull the prop assembly apart this weekend & check for markings. I
contacted the fine folks at Purple Hill Air who just painted the aircraft &
installed the prop for & they stated that no information of any kind came
with the prop save a generic prop log booklet.
Robert, you mention that the hub has the diameter & pitch marked on the
hub. Is this on the front or back? I have not seen the hub as it is
covered by the great looking Sensenich spinner. Getting their spinner, by
the way, turned out really well. No cutting required, and the spinner is
all predrilled, with nut plates, and the best part is that the material is
heat treated. I would also not be inclined to use the Murphy spinner. Had
some trouble with the forward flange although the rear flange with a doubler
& the spinner itself looks great.
That sounds like one heck of speed for a Rebel. Have you cross checked
your airspeed with GPS etc? As I mentioned earlier, I am now back at the
speed of Rebel equipped with the Rotax 912. Although the 912 is a very fine
engine, this is not what I am looking for.
Thanks again for your help.
Brian #328R
-----Original Message-----
From:
murphy-rebel@dcsol.com [mailto:
murphy-rebel@dcsol.com]On Behalf Of
Robert Johnson
Sent: Thursday, March 28, 2002 8:25 AM
To:
murphy-rebel@dcsol.com
Subject: Sensenich prop 74 x 58"
This message is for Brian regarding your new Sensenich 74" Dia. x 58"
pitch. This is what I have on Rebel "652" on my O320 H2AD 160HP. I can't
pull the full 2700 RPM on a static run-up, more like 2500, but it climbs
like a rocket, and just the other day, with a passenger on board and 3/4
fuel, I demonstrated to him, in level flight, fire wall the throttle, fight
to stop from climbing, and watch the airspeed indicator creep past 160 mph,
while approaching 2700 rpm. From what you described with your performance,
it does not sound like a 58" pitch. Have you checked the markings on the hub
??
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<DIV><SPAN class=650074017-31032002><FONT face=Arial color=#0000ff size=2>Hi
MIke</FONT></SPAN></DIV>
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size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=650074017-31032002><FONT face=Arial color=#0000ff size=2>That
is quite a thought re: RPM testing. We do indeed have the same frequency
here. Though I believe the frequency spec. is much much tighter than
2%. I used to balance large fans using strobe equipment etc. to measure
phase angles of the out of balance fans etc. Same principal. I