How much power is enough power?

[Crash]

When choosing Motors if we look at the wattage ratings how much is enough and how much is too much?
Myself I'm running a motor That's rated at 6200 Watts often Peaks out at 10000 Watts or 13 hp
and has broke four Flex shafts in a season wondering I can get the job done with less wattage or horsepower saving the driving line.?
Is there a formula to choose the rite wattage motor for a given set up.?
Thanks guys
Dan

[Fluid]

Motor maximum watt ratings are deceptive. They may be max for ten seconds, for extended running - or they may be marketing hooey. In many cases it is the ESC which limits power, not the motor. 10,000 watts on 8S is well over 400 amps, good luck finding an ESC which can handle that for very long.

Are you racing? Are you winning? If you are breaking flex cables then either the cables are too small, too weak, or are improperly installed/supported. Too, how you drive can effect cable life - lots of full throttle hits from a stop or from low speeds puts a very large instantaneous stress on the cable.


.

[Crash]

My data log showed 430amps with my big prop on it at over 10000 watts recorded as well.
At that rate its over 13 horse power, I am not surprised stuff brakes.
My question is to , how much is enough.
I can run a 3600 watt motor on 8s at 2070kv and go faster then my 1650 kv 6200 watt motor on 8s.

[Fluid]

Part of the problem may be the motor Kv. That is on the high side even for a 6S racer. Depending on the hull size, a motor Kv of 1000 rpm may be more appropriate. That gives a wider safe rpm range and with the appropriate prop can give competitive speeds. But we don’t have enough information - we are not mind readers.

Again I ask, are you racing? If so is your boat speed competitive? And exactly what hull are you running? Too, exactly what motor and prop are you running?


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[rol243]

must be running a 3/16 inch shaft. if you have that much h.p. etc try a 1/4 inch shaft.

[Crash]

Well, I was trying to get a answer that applys to choosing the rite motor wattage and what's necessary amount of power and what's too much..more of general question not exclusively about my set up but, ok.
Mine is a 36 inch mono
8s
Today it has a 646 prop on it, I also run a 452
I do not race it.
Runs in the upper 70's mph
At 78% throttle.
Motor is a tp
4060 1650kv

[Crash]

must be running a 3/16 inch shaft. if you have that much h.p. etc try a 1/4 inch shaft.

I looked into the 1/4 inch drive, there are no props under 60mm at 1/4 inch shaft

[rol243]

yes there are 1/4 inch flex shafts which come with a 3/16 step down so you can run 3/16 bore props.

[NativePaul]

500 watts per kilogram is generally enough power for me. It is what my racegoers run at so I set my fun running boats for the same, it gives me enough speed and enough run time for my tastes and scales well to any size boat I have built.

It is not for everyone though, I know fun runners that want more runtime at the expense of speed, that want more speed at the expense of runtime, that want more runtime at the expense of expense, and plenty that want the imposible. Fun running driving styles vary lot, and fun runners all want something different from the boats, so there is no simple answer.

Breaking 4 shafts in a season sounds like too much power for your shafts, or too small a shaft for your power, but it could be something misaligned in your driveline (I broke 3 wires in one boat this season and it turned out to be a slightly eccentric bore in the stub shaft, not enough to notice spinning it by hand, but enough to rapidly fatigue the wire right next to it in use).

What is your driveline and are they all breaking in the same place?


If you go up from 1650kv to 2070kv without propping down a lot you will be pulling a LOT more power than you are now, whatever the motor is rated at. Even if you do prop down it is a very high Rpm and as fluid says, at those RPM a small difference in prop size makes a big difference to amp draw, you might get away with it for a few seconds on a SAW run, but I wouldn't recommend it. It sounds like you could use propping down on the setup you have.

[Prodrvr]

There is no such thing as too much power

[Crash]

500 watts per kilogram is generally enough power for me. It is what my racegoers run at so I set my fun running boats for the same, it gives me enough speed and enough run time for my tastes and scales well to any size boat I have built.

It is not for everyone though, I know fun runners that want more runtime at the expense of speed, that want more speed at the expense of runtime, that want more runtime at the expense of expense, and plenty that want the imposible. Fun running driving styles vary lot, and fun runners all want something different from the boats, so there is no simple answer.

Breaking 4 shafts in a season sounds like too much power for your shafts, or too small a shaft for your power, but it could be something misaligned in your driveline (I broke 3 wires in one boat this season and it turned out to be a slightly eccentric bore in the stub shaft, not enough to notice spinning it by hand, but enough to rapidly fatigue the wire right next to it in use).

What is your driveline and are they all breaking in the same place?


If you go up from 1650kv to 2070kv without propping down a lot you will be pulling a LOT more power than you are now, whatever the motor is rated at. Even if you do prop down it is a very high Rpm and as fluid says, at those RPM a small difference in prop size makes a big difference to amp draw, you might get away with it for a few seconds on a SAW run, but I wouldn't recommend it. It sounds like you could use propping down on the setup you have.

Thanks.
My shafts keep breaking at the weak spots, at the drive dog knotch, at the prop shaft meets flex cable. It once twisted the solid steel section shaft.
I have checked and rechecked drive line and now I just think its too much torque for the 3/16 shafts.
If a guy runs a motor rated at. 3600 watts 1650kv and a guy runs a 6200 watt 1650kv does one draw more amps ? Does it make more power aka torque in same set up boat and prop and lipos same?

[Crash]

There is no such thing as too much power

lol, you been saying that but there may be a thing as too much power in this case, #gofundme for rc parts has been started'

[larryrose11]

If a guy runs a motor rated at. 3600 watts 1650kv and a guy runs a 6200 watt 1650kv does one draw more amps ? Does it make more power aka torque in same set up boat and prop and lipos same?

Power = Volts * Amps.
Voltage*Motor KV*efficency = Loaded RPM.
The prop is what determines the amp draw for a given setup.
For a given hull and prop, If the motors have the same KV and efficiency, then the amp draw will be the same. The motor power rating is what the motor is capable of producing.

[Prodrvr]

lol, you been saying that but there may be a thing as too much power in this case, #gofundme for rc parts has been started'

I need a Gofundme account lol

[Prodrvr]

Where are you getting your flex shafts from?

[Crash]

Where are you getting your flex shafts from?

I have tried stock, OSE HD and dasabota.
I am in the process of installing a Speed Master stinger in it now, to improve what was the stock stinger.
I also bought a lower wattage higher kv motor.
still a 8s motor but should not have the power to snap drives.

[rol243]

good flex shafts; cc racing / prather / speedmaster / hughey[ if you can get ] . also don,t cut into the hard shaft too much for those grub screws. i keep this shallow and remove any excess screw so all is flush on the dog. Crash, also have you considered trying a lower kv motor and run larger props. ?

[Crash]

good flex shafts; cc racing / prather / speedmaster / hughey[ if you can get ] . also don,t cut into the hard shaft too much for those grub screws. i keep this shallow and remove any excess screw so all is flush on the dog. Crash, also have you considered trying a lower kv motor and run larger props. ?

I have a 52mm prop that is a blast to run but, they producd more torque then the 46mm I have been trying lately. And the 52mm produced 380 amps on the data log. The smaller props get you there too with less amp draw in my boat.
I am pushing 70 plus now with my boat, ill be at 80 plus on this next set up.

[photohoward1]

Post some pics of the set up let’s have a look. Running some pretty powerful set-ups on 6s. Don’t go to a ¼ until 8pr 10s. Alignment is key.


Sent from my iPhone using Tapatalk

[Prodrvr]

Could always try a shaft from MHZ.

[rol243]

common breakage of shafts can result from the drive dog contacting the strut which in tern causes severe drag / binding when the shaft contracts. motor wants to turn shaft but can,t due to binding on strut so something will give. this is like holding the prop tight so it can,t move then applying some motor power.

[Nevs]

With 10.000 watts peaks you would need a 1/4 flex.
How much power is enough power?. No idea. it depens on what you want and where you run your boat. The boat I had /have the most fun with is a very light (10 pounds) 47" Delta Force copy. It can run full speed for 8-10 min, on 12s /4000. The top speed is in the low 40. But its "enough" for that pond.
So in this case 100-125 watt/pound is fine.
I tryed a bigger prop, (62mm). Gained less then 10 mph. Had less fun and less running time.
https://www.youtube.com/watch?v=4tcpHLrk63g

[Crash]

1027180656b.jpg
1027180733.jpg
1027180700c.jpg
New set up going in
8s 2070 kv
3600 watt
X646 prop from Dr. Props
SF 300 X

[Crash]

With 10.000 watts peaks you would need a 1/4 flex.
How much power is enough power?. No idea. it depens on what you want and where you run your boat. The boat I had /have the most fun with is a very light (10 pounds) 47" Delta Force copy. It can run full speed for 8-10 min, on 12s /4000. The top speed is in the low 40. But its "enough" for that pond.
So in this case 100-125 watt/pound is fine.
I tryed a bigger prop, (62mm). Gained less then 10 mph. Had less fun and less running time.
https://www.youtube.com/watch?v=4tcpHLrk63g

I think in the my case you answered the question for me. 10,000 watt is too much for my set up. Its 3 times what is needed to move this hull around and more then the flex shaft can take in my set up.
I will update this thread when I get some data of the logger for the new motor.

[NativePaul]

I hope your going to run your cells in parallel for 4s2p and not as 8s with the new 2070kv motor.

Good luck.

[Crash]

I hope your going to run your cells in parallel for 4s2p and not as 8s with the new 2070kv motor.

Good luck.

Ive heard that before.

I ran my 1650kv on 10s and got some of my best data logs to date.

I will run this 2070kv on 8s

[Prodrvr]

Which motor is this 2070? That Kv on 8s has my attention!!!

[Crash]

Which motor is this 2070? That Kv on 8s has my attention!!!

Tp 4030 V1
2070kv
29 volt
124 amp.
1600 to 3600 watt

[Crash]

Which motor is this 2070? That Kv on 8s has my attention!!!

Just did some bench testing of that motor on 8s no flex shaft no prop just bolted into the boat the motor wires are getting hot right away they're not they're not enough for 8's even though the motor is rated for it stay tuned I'm going to try 6

[Crash]

Which motor is this 2070? That Kv on 8s has my attention!!!

Surprisingly this motor is rated for 29 volts same as my bigger motor That's rated for 29 volts but this little 2070kv only likes 5S otherwise the wire start getting hot
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