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Author Topic: Estimated speed for 2 inch pitch props  (Read 2582 times)

Offline Clancy Arnold

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Estimated speed for 2 inch pitch props
« on: December 20, 2006, 11:47:52 AM »
          20 ft        25 ft       30 ft         35 ft        42 ft         52 ft
RPM  Sec/Lap   Sec/Lap  Sec/Lap    Sec/Lap   Sec/Lap   Sec/Lap
12K    3.77        4.71        5.66        6.60         7.92         9.80
14K    3.23        4.04        4.84        5.65         6.78         8.40
16K    2.83        3.53        4.24        4.95         5.94         7.36
18K    2.51        3.14        3.76        4.40         5.28         6.53
20K    2.25        2.83        3.39        3.96         4.75         5.88
22K    2.05        2.57        3.08        3.60         4.32         5.34

Note: extending your arm out will add about 0.2 sec per lap.
 
Revised to add line lengths Ray requested.
« Last Edit: December 22, 2006, 05:12:52 AM by Clancy Arnold »
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Clancy Arnold
Indianapolis, IN   AMA 12560 LM-S
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Offline minnesotamodeler

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Re: Estimated speed for 2 inch pitch props
« Reply #1 on: December 20, 2006, 03:03:59 PM »
So my Norvel .061 is cranking a 6x2 prop well over 20,000 rpms?  Impressive if so.

The table would be more useful if expanded to 35', 42', 52', maybe intervals in between.  I don't know of anyone personally who uses lines under 35'; certainly not in the 20s. 

Ah--perhaps electrics.  And, of course, 1/4A. 

Thank you, Clancy, nice work.

--Ray
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--Ray 
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Offline Clancy Arnold

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Re: Estimated speed for 2 inch pitch props
« Reply #2 on: December 22, 2006, 05:18:05 AM »
Ray
I added the additional line lengths you requested. (Twice).

Glad Robert admitted that he had lost a days posts as I had just thrown the data into the round file.   Dug it our and re-posted it.  No complaints here Robert.  Most people would have just hoped no one noticed.

Clancy
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Clancy Arnold
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Offline minnesotamodeler

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Re: Estimated speed for 2 inch pitch props
« Reply #3 on: December 22, 2006, 07:23:24 AM »
OK, my "lost" comments:  (By the way, Thank you, Clancy.)

Even on 52' lines, and a 6x2 prop, I can't get my LittleAxe to slow down beyond 5 sec. laps--so that .061 is cranking, what, 24-25k?  Wow...

The Norvel .049s are another matter--I can get them to over 4 secs. on 42' lines on my smaller planes (LilGeo, etc.),  maybe 4 sec. flat on 35'--that's still 20k or better?  Sure seems high.  It's only 15% nitro I'm running.  I really need to find a tach sometime and see.

I know the Norvels are good--but, man!

Verrrrry interrrrresting...

--Ray
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Offline Clancy Arnold

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Re: Estimated speed for 2 inch pitch props
« Reply #4 on: December 22, 2006, 11:55:24 AM »
Ray
On one of the posts on Cox engines is a link to a Cox collector and on his site he has copies of test reports and one report lists the .010 TD as peaking at 30,000+ rpm.

Clancy
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Clancy Arnold
Indianapolis, IN   AMA 12560 LM-S
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Offline Clancy Arnold

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Re: Estimated speed for 2 inch pitch props
« Reply #5 on: December 23, 2006, 12:02:31 PM »
Ray
I just received copies from J.B.M Griner of the factory specification sheets provided by L.M.Cox Manufacturing Co. 
The sheets printed in 3-61 and also 8/74 both give the following speeds.

TEE DEE .010 Prop size 3" dia. x 1 1/4 P, 27,500 RPM

TEE DEE .020 Prop size 3 1/8" dia. x 2 1/2 P (3 blade), 22,750 RPM
4" Dia. x 2 1/2 P, 19,500 RPM

Clancy
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Clancy Arnold
Indianapolis, IN   AMA 12560 LM-S
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Offline minnesotamodeler

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Re: Estimated speed for 2 inch pitch props
« Reply #6 on: December 23, 2006, 02:40:52 PM »
We may have to re-think the line length for these .020s. 

--Ray
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Offline Paul Smith

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True helical prop speed
« Reply #7 on: January 11, 2007, 05:41:34 AM »
I've done several Spreadsheets like yours. 

I found no relationship whatsoever between calculated helical prop speed and actual airplane speed.

It is my theory that due to the aerodynamic lift of the airfoiled prop blade, it is possible to fly EVEN FASTER than calculated helical speed.  Whatever the reason, airplanes sometimes exceed helical speed. This happens on light combat planes

In most cases, however, due to the large drag factor of stunters, they fly well under helical speed.




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Offline Ralph Wenzel (d)

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Re: Estimated speed for 2 inch pitch props
« Reply #8 on: January 11, 2007, 03:24:27 PM »
Hi Ray,
I'm very impressed with the NorVel's output, too. My .061 AME's are turning 18,500 on a 7-4 Tornado Nylon, with Powermaster 10-22 fuel, so I find your numbers quite believable. Fuel economy is, well, unimpressive, but at 1½ oz. per flight, who cares?




Quote from: minnesotamodeler on December 22, 2006, 07:23:24 AM
OK, my "lost" comments:  (By the way, Thank you, Clancy.)

Even on 52' lines, and a 6x2 prop, I can't get my LittleAxe to slow down beyond 5 sec. laps--so that .061 is cranking, what, 24-25k?  Wow...

The Norvel .049s are another matter--I can get them to over 4 secs. on 42' lines on my smaller planes (LilGeo, etc.),  maybe 4 sec. flat on 35'--that's still 20k or better?  Sure seems high.  It's only 15% nitro I'm running.  I really need to find a tach sometime and see.

I know the Norvels are good--but, man!

Verrrrry interrrrresting...

--Ray
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Offline minnesotamodeler

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Re: Estimated speed for 2 inch pitch props
« Reply #9 on: January 12, 2007, 03:59:25 PM »
Yeah, I made up 2 different tanks for my LittleAxe(s) of about 1.5 oz. capacity, or a little more, from a couple of film cannisters.  Required if you want any chance of getting through the pattern.

I've really wanted to try a 7x2 on the .061s but can't find one.  the x2 pitch seems plenty, and the larger diameter should produce a little more grunt in maneuvers, right?  Maybe even an 8x2, I could always cut it down a little...if there were such an animal.  I've never seen nor heard of one.

--Ray
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Offline frank carlisle

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Re: Estimated speed for 2 inch pitch props
« Reply #10 on: January 20, 2007, 02:03:08 PM »
i don't think there is one ray........
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Frank Carlisle

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