Confused about 6S Motor

[rickwess]

I'm planning my winter build and was thinking about a DF35 running a LP4092 1480Kv on 6S. Now when I go over to LP's site to find the spec's on the motor, it shows a max of 23 volts. A fully charged 6S would be 25ish volts.

I see plenty of people running a LP40xx on 6S. What am I missing?

[Fluid]

It appears that Leopard is limiting the rpm of that motor to about 34,000 rpm - probably a good idea. The long case combined with the small 1/8" shaft could mean shaft whip at high rpm, damaging the motor. Neu Motors saw this problem some years ago and their longer motors offer the 8mm shaft to solve the issue. Shorter motors like 75mm cases would not have this limitation.


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[martin]

Fluid just in case its a typo the 4092 motor shaft is 5mm, still on the small size though for this length motor.

[rickwess]

Makes sense, given the LP4082's are all spec'd at a much higher voltage.

[Fluid]

Fluid just in case its a typo the 4092 motor shaft is 5mm, still on the small size though for this length motor.

Yes, I thought one thing and typed another. 5mm shaft on the Leos....



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[photohoward1]

why not go with the 4082/3y 2200kv on 4s. M447 and let it rip. 55mph easy.

[olwarbirds]

Im running a DF Cyberstorm ,,,Leo 4082 2000kv 180 amp esc 6S octura 445 ....DF 36 Explorer Leo 4074 2200kv 180 amp esc 6S octura 446 same set up in a pursuit, all three boats are running speeds around 70 mph ...with no over heating probs ...motors/esc's barely warm...we are using thrust bearings and seperate water lines...we have been running these same Leo motors and esc's for a year now on 6S ...we run 2-3 times a week normally...we use dinogy and nanotech 65-130c lipos...we have not experienced any problems with the Leo motors or Hobbywing aka Turnigy esc's...we have wore out a few lipos :) ...the Leo 4074 or 4082 should be plenty of motor for the DF 35 from what we have personally been expertencing with ours....good luck in your build... DJ

[lenny]

Hi,
How much run time do you get out of the pack on the Pursuit setup ?
And on how many mah cell pack, Are you running two 6s in parallel or just one pack ?

Thanks for any info on this.

[olwarbirds]

Hi,
How much run time do you get out of the pack on the Pursuit setup ?
And on how many mah cell pack, Are you running two 6s in parallel or just one pack ?

Thanks for any info on this.

Hi Lenny, 2 3S 5000mah series 65-130c ...I think my friend has a few dinogy 3S 6000mah (not positive) ..actually to be honest we havnt ever timed our runs ....Im guessing around 5 minutes though ...next time out I will time a full run for ya.... DJ

[rickwess]

why not go with the 4082/3y 2200kv on 4s. M447 and let it rip. 55mph easy.

6S is amp friendly. An LP4082 is about 3500 watts burst. At 6S that's 153A and at 4S that's 230A.

[rickwess]

Im running a DF Cyberstorm ,,,Leo 4082 2000kv 180 amp esc 6S octura 445 ....DF 36 Explorer Leo 4074 2200kv 180 amp esc 6S octura 446 same set up in a pursuit, all three boats are running speeds around 70 mph ...with no over heating probs ...motors/esc's barely warm...we are using thrust bearings and seperate water lines...we have been running these same Leo motors and esc's for a year now on 6S ...we run 2-3 times a week normally...we use dinogy and nanotech 65-130c lipos...we have not experienced any problems with the Leo motors or Hobbywing aka Turnigy esc's...we have wore out a few lipos :) ...the Leo 4074 or 4082 should be plenty of motor for the DF 35 from what we have personally been expertencing with ours....good luck in your build... DJ

Thanks, I now understand why the LP4092 is spec'd so low. It makes sense that at some length, the 5mm shaft will have issues at the high RPMs.

2000Kv and 2200Kv at 6S will get you some crazy RPMs. I'm convinced 6S is the way to go but was thinking more along the lines of 1600Kv. Conveniently, that's a 2Y so I'd get the torque upside of a wye motor.

I'm a ThunderPower fan and was looking at two 6S 3850mah 45C packs in parallel or two 3S 7700mah 45C packs in series. Volts, amps weight and price are effectively the same for each configuration. Is there any advantage of one over the other?

[Fluid]

I set SAW records near 90 mph with 2200 Kv motors and 6s. IME such a motor is not well suited for most sport running; even with a small prop to reduce amp draw the setup is sensitive to run time and how it is run. I'd use about 600 mAh of battery for each one-way pass and after two passes the ESC temps were logged around 170*F in November .....


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[rickwess]

I set SAW records near 90 mph with 2200 Kv motors and 6s. IME such a motor is not well suited for most sport running; even with a small prop to reduce amp draw the setup is sensitive to run time and how it is run. I'd use about 600 mAh of battery for each one-way pass and after two passes the ESC temps were logged around 170*F in November .....
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I was going to ask this question in another thread, but since this one has evolved, this seems like the appropriate place. What's a safe RPM target for sport runners who have the urge to race/SAW every now and then? I was thinking 35K. Then again, I put a 225 ProXS on the back of a 19' J-Craft. Doesn't mean I run on the hairy edge every time I go out, but I do get those urges a few times a season.


test2.jpg

Yes the wide angle makes it look worse than it really is, but you get the point.

[Fluid]

If you multiply the motor Kv by the nominal voltage you will obtain an rpm which is higher than what you'll see on the water. 2200 Kv x 22.2 volts = 48,840 rpm, but the actual rpm will be closer to 40,000 depending on the pack quality, prop and hull setup. I've set SAW records with on-the-water rpm between 33,000 and 41,000, the later being more specialized than the former and more prone to an accidental burn down if you prop up a bit too much or run a bit too long.

Actual SAW competition is considerably more demanding than the "SAW-type" running that most sport runners do. A competition SAW run may last five seconds at WOT and must be done at least twice, usually in rapid succession; each run is usually well over 1000 feet long. Most sport runners do not run like this, they use WOT for a couple seconds. Because of this difference, in theory they can use a hot setup with less risk of burning down...but YMMV.


I'd keep the calculated rpm under 36,000. Running a hot setup extensively at part throttle is a great way to cook an ESC.
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[rickwess]

I'd keep the calculated rpm under 35,000..

By calculated, I assume you mean (nominal voltage) * (motor Kv), where the nominal voltage is 3.7V/cell. The fully charged voltage being a couple of points per cell higher and a RPM bonus when the boat first hits the water.