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Old Sep 15, 2001, 04:47 PM
EFlight=Fun,Big-T=BIG FUN
San Antonio, TX, USA
Joined Jan 2001
964 Posts
Need RS380PH number for MotoCalc & Thrust computation

Could someone send me or tell me were to get the MotoCalc numbers for a RS380PH?
Need Constant, Current, Resistance and Weight.

MotoCalc has RS380SH but it bears little resemblance to my actual numbers (A,V,W,RPM).

How do you compute thrust from pitch & rpm?

I am running salvaged SoarStar gear (RS380PH, 1,85:1GB, 8x4 on 8x600AE) on a scrap built that is close enought to done to let me get a good guess at AUW. Trying out battery/prop combos to see what appears to work best.
During static tests I got
At 30 Seconds:
9.9A, 8.0V, 80W, 7950RPM - computed static speed = 30mph
At 2 minutes (350maH used)
9.0A, 7.3V, 67W, 7350RPM - computed static speed 27.8mph

Thank you,
Bernard
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Old Sep 17, 2001, 10:48 AM
Registered User
Rhode Island
Joined Oct 2000
585 Posts
Unfortunately the designation RS380PH only tells part of the story. A complete designation would be something like RS-380PH-4075. The last four digits indicate the size of the wire and the number of turns; ie, 75 turns of .40mm wire (I have no idea if that's an actual 380 wind). The only difference between a 4.8V Speed 400, 6.0V and a 7.2V is the winding, in other words all three motors are RS-380PH's but the last four digits would be different for each motor.

The E-Zone FAQ describes how to measure all three motor constants, here: http://www.ezonemag.com/pages/efaq.htm#motor16

I believe the SoarStar motor is the same as a 6V Speed 400, with a flux ring. The flux ring will slightly reduce the Kv and Io but would have no effect on Rm.

Hope this is of some help.
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