Who runs an Outrunner in their boats?

[Fluid]

Thanks Jay, can you recall who set that record or what equipment he/she was using? I'm guessing they were probably sponsored and you may know who the manufacturer was.

It was one of the Wollards - can't remember now who was actually driving it. Probably an N-2 or O Mono set in Valdosta around 2006.



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[sailr]

Outrunners have a LOT more torque than inrunners because the mass is on the outside. You can get by with lower KV's because you can swing MUCH larger props.

Our Jollymotor offshore boat has a little outrunner in it. The boat does about 38mph. Not bad for a $300 rtr on only a small 3S lipo!

[Ub Hauled]

Outrunners have a LOT more torque than inrunners because the mass is on the outside. You can get by with lower KV's because you can swing MUCH larger props.

Our Jollymotor offshore boat has a little outrunner in it. The boat does about 38mph. Not bad for a $300 rtr on only a small 3S lipo!

Sorry man, I have to desagree with you no this one, it has more torque due to the amount of poles, the mass may have something to do with it but all being equal the poles dictate the torque. More poles = more torque.

[sailr]

Back atcha. The MASS of the magnets contained on the OUTSIDE, rotating around the fixed stator gives it the torque...like a flywheel.

I manufacture outrunner motors for aircraft. I have been doing it for close to eight years now. Trust me, I know of what I speak. Even if you could put 12-24 poles in an inrunner, it would still not have a fraction of the torque of an outrunner. The only use for inrunners in aircraft is with a gearbox because alone, the motor won't turn a prop big enough to fly the airplane (except for some really screaming little guys with 5" props!) It wasn't until the advent of outrunners that electric aircraft really took off (pun intended)

Sorry man, I have to desagree with you no this one, it has more torque due to the amount of poles, the mass may have something to do with it but all being equal the poles dictate the torque. More poles = more torque.

[ozzie-crawl]

i would like to see some comparison in weight between the inrunner rotor and a out runners outer, both motors being of similiar kv and watt output.
my guess would be the out runner could be 2-3 times the weight.
i tried a scorpion 3026 1900kv in my meanmachine for some short runs.
wasnt real impressed till i propped up to take advantage of the torque.
for a small motor it sure has some balls,the motor did die,looked like wires shorted them selves out,had it replaced under warrantie,will be running it in my
vs1 as cooling wont be an issue

[Mel279]

I've run tonic-x z30 800kv but change the winding to suit for 6s in my triton and manage to get 51mph. Then I tried using scorpion 4020 1390kv 6s and manage to get 56mph, eventhough I put a watercool on the motor mount but still it gets hot after just a few run on freshwater, haven't tried saltwater yet to see if there's any difference in speed and temp.

[marker]

An inrunner and outrunner with the same Kv and nett current draw (Iin - Io amps) will have the same torque. It makes no difference to the number of poles the motor has either.
The equation for torque is,
1355 / Kv * ( Iin -Io) Inch-oz torque.

Iin = motor amp draw
Io = no load amp draw
1355 /Kv = Kt, the torque constant

[befu]

mean machine

I am running a turnigy 3648-1450kv outrunner in mine. Rated for 6s, have only been able to run 4s before the water became really hard. For a sport boat it is really cheap for how much fun it is.

It is pushing a 47mm 3 blade and tops out real fast. Motor is cool. I am looking at getting an eagle tree setup this spring so I can do some real number results. Interesting, the instrumentation will cost me more than the entire boat did!

I always thought outrunners had more torque in similar sized motors due to the radius where the magnetic force acts. An inrunner, the magnets are closer to the shafts. On a 36mm outrunner, the magnets are probably out around 34 to 35 mm. On a 36mm outrunner, I would guess they are closer to 20mm due to the fact they are attached to the shaft, and the motor windings have to go outside of them.

These large outrunners are interesting. I think I will hold onto my larger 52" and 54" monos as battery prices continue to drop, they will become feasible for sport running again. $150 ish for a motor, if you could get multiple batteries and a speed control that would push it for a total of 30 minutes for around another $400, that would be comparable to a gas setup. How much does a zenoah cost now? last time I was in this, it was about $550 for motor/pipe/mount

Brian

[Fluid]

1355 / Kv * ( Iin -Io) Inch-oz torque.

Theoretical value for the potential torque of a generic ideal motor. Actual torque values should be derived from the watt output at specific rpm. Measurement, not theory. This takes into account various dynamic losses and moment arm.

Example: at 20,000 rpm, a motor uses 90 amps at 14.8 volts
At 90% efficiency its output is 1200 watts

1200/746 = 1.6 hp

1.6/20,000rpm = 0.00008

0.0008 x 63,025 = 5.04 ft-lbs at 20,000 rpm
(63,025 is a conversion constant)

Measurement is the key to actual values, and is possible through the use of a datalogger. This isn't perfect without the use of a dyno. Real-world torque varies depending on voltage and rpm. No one has an "ideal" motor.



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[greenblast]

i am also interested in trying outrunners. i recently got some heli parts to feed my addiction! part of that "bargin" lol! is a align 600l and a 75 amp esc. i am going to try this setup. anyone tried this motor in boats? the motor is 1620kv rated up to 6s @ 1500 watts.i was thinking of trying 3s or 4s to start

[ray schrauwen]

I was looking for a sport motor for my 34" 6S SprintCat. I like the boat a lot, but it is way too fast (60+) for the small pond near my home. I chose the Scorpion 4025/1100; running on 6S1P with an x450 it runs near 40 mph for over 5 minutes. That is fast enough to be fun and long enough to be ready to bring it in. Amp draw is low for a motor with a 100 amp top end - nothing gets above 100F. More Kv is needed for higher speeds but that wasn't my goal. I got mine from Jim at southriverrcboats.




.

Thank you! I bought this motor for my 29" 3.8lb Promise hobby Catmaran, same as the orange one in an avatar, just smaller.

I now see Scorpion may have a 1600 KV 4025? [I]s that right???

If so, I want that one more but, it woul be nice to swing a x450

[Meniscus]

Great explanation Jay. I for one certainly found that helpful.

A while back I purchased a outrunner which Diegoboy is using in his stretched Renegade. It works great and better then the stock one from mile-high RC.

If someone is looking for outrunners, especially the sport boaters out there, contact 'sailr' on this forum. If I'm not mistaken, he may have some extra stock of outrunners of various sizes and KV ratings. If you are unsure what you want exactly, I'm sure he could help.

For me, I'm thinking of picking up a couple matched outrunners for a medium sized toy cat I have sitting around. It will primarily be for the kids at the pond and not setup for extreme boating, but who knows.

Anyone know if the outrunners induce more or less torque roll when turning larger props? Just curious.

[Mel279]

Thank you! I bought this motor for my 29" 3.8lb Promise hobby Catmaran, same as the orange one in an avatar, just smaller.

I now see Scorpion may have a 1600 KV 4025? [I]s that right???

If so, I want that one more but, it woul be nice to swing a x450

From what I've known only scorpion hk3026 have 1600kv, as I have the hk4020 1390kv, the 4025 maybe have the 1100kv, thats the highest kv if Im not mistaken.

[Fluid]

The only place I've seen a reference to the high Kv motor is in a drop menu on an order page at southriverrcboats. Ray asked a major US distributor the question, he has not yet answered.



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[Doug Smock]

[QUOTE=sailr;155074]

I manufacture outrunner motors for aircraft. I have been doing it for close to eight years now. QUOTE]

Jim you should take us on a virtual tour of your manufacturing facility. I'm sure we'd all enjoy it.
Interesting thread fellas.
Doug