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HELP Please! Ziroli twin Beech power system?

Old 02-16-2018, 02:39 PM
  #1  
sailbode
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Default HELP Please! Ziroli twin Beech power system?

3/4 done with a Ziroli Twin Beech and would like to power it with electrics.
Limited budget so wanting to give the Hobby King stuff a shot...I've used it before with good success.
Estimating weight will come in at approx 38 lbs. (lets say 40)
20 lbs per motor....most guys say 100 watts per pounds minimum so I'm looking at Turnigy SK3 6374 192kv max watts 4000 but sustained 2750
10s = 7104 "unloaded" RPM
12s = 8524 "unloaded" RPM
Question: What RPM should I expect loaded "static"?
Question: If I go with 12s, and prop it for 50 amps (2200 watts) at full throttle, should that match or exceed the performance of a typical Zenoah G38?
Question: If I go with 8000 mah pack can I expect 10 minute min flight?
Thanks
Don

Last edited by sailbode; 02-16-2018 at 03:09 PM.
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Old 02-18-2018, 01:00 AM
  #2  
MustangMan
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I just did some calculations using Drive Calculator 3.4. I had to do a little bit of guessing on the motor specs since HobbyKing doesn't have a lot of specifics on that motor. You should take all of this with a large grain of salt.

With a Turnigy 5000mAh 40C 12S Lipo, RotorStar HV-80A ESC (with guessing on specifications), Turnigy SK3-6374-192kV motor, and APC 20x10E prop peak current is 67A, power 2665 W, 7330 RPM, static thrust 12.4 Kg (27.3 lb), pitch speed 112 kmh (70 mph), and wide open throttle flight time of 4.1 minutes. I suspect you could fly 10 minutes easily with a scale flight profile.

Two of these on a 40 lb plane would have unlimited vertical performance. Not exactly scale for that airframe!

The 20" propeller seems roughly comparable to that recommended for the G38 gas engine.

Switching to an APC 18x8E prop the calculation gives peak current is 45.5A, power 1895 W, 7707 RPM, static thrust 8.4 Kg (18.5 lb), pitch speed 94 km/h (58 mph), and wide open throttle flight time of 6 minutes. I suspect you could fly 10 minutes easily with a scale flight profile.

Hopefully you'll find this useful and reasonably accurate. Good luck!
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Old 02-18-2018, 06:58 PM
  #3  
ron_van_sommeren
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Originally Posted by MustangMan View Post
... Two of these on a 40 lb plane would have unlimited vertical performance. Not exactly scale for that airframe! ...
And the extra weight will result in higher minimum start-, landing- and flying-speeds.

Originally Posted by sailbode View Post
... Twin ... 38lbs ...
Extend motor wires, and keep the battery wires short. Keep controllers close to battery.

Too long battery wires can kill ESC: precautions, solutions & workarounds - RCG
Contents
  • Solution I & II, rules of thumb
  • Problem
  • Capacitor type & polarity (orientation!)
  • How & where (not) to add extra capacitors
  • DIY capacitor pack pictures
  • Capacitor & pack suppliers
  • Expert/manufacturer opinions, they all say the same ... & their rules of thumb.
  • Explanation, water hammer/knock analogy, theory, references, measurements
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