Building Tips and technical articles. > 1/2 A building.

Estimated speed for 2 inch pitch props

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Clancy Arnold:
          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.

minnesotamodeler:
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

Clancy Arnold:
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

minnesotamodeler:
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

Clancy Arnold:
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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