What N motor for 7.4 5000ma lipo?

[HTV Boats]

In building some P & Q tunnel projects I am wondering about also trying a "N" setup since I have quite a few 2s 5000mah packs that are used in series for a 4S "P" boat. I know it's not going to be all that fast but could be a good trainer or just fun playboat for the kids or a little pond racer. Would something like a Feigao 540 5XL/3324kv or a Leopard 3674 3270kv 2d work? anyone run these motors on 7.4v? Hull would be a lite 24"-27" boat with OS lower to take any power. Turning maybe a 438 prop? What might the speed control requirement be? 60amp or just a Turnigy120 I already have? Load should be similar to a D-2 Cat.

On a side note whats the difference between a Y and D motor. I have the impression the D takes more current so please enlighten me.

Thanks in advance for any info you care to share.

Mic

 

[D. Newland]

A 540 7L would be a solid performer. X438 would be good, but after testing you may be able to get to an X440.

When you go to the lower voltage classes, you really need to stick with a higher amp rated speed control. use the 120.

As far as the D vs Y wind, my only experience is w/the Neu motors. Both are powerful, but D's typically are much more sensitive to timing, and like very low timing. Y's aren't as finicky to timing changes and can give you more options to "tune" via timing.

 

[jeepers]

I agree with Dave Newland, I have ran the 540 7L motor and those suggested props are a good place to start.

The boat might not be as slow as you think though, my N class sport hydro ran nearly 50mph on 540 7L.

 

[obrien]

I am pretty sure most of the guys running n2 mono run higher amp speed controls as well. I think most of the ones I have seem were hydra 240's. could be wrong though.

 

[MarkTanski]

Thats a 2400 watt motor, not saying you'll be pulling maximum power but just keep in mind that 2400 watts / 7.4V = 324.32 amps!

Will not take much of a mistake choosing a prop to make a 120 amp esc go poof.

You'll also need some high quality high C batteries, N setups are way harder on equipment than the higher cell count classes, when you give up volts you have to supply more amps.

 

[HTV Boats]

Thats a 2400 watt motor, not saying you'll be pulling maximum power but just keep in mind that 2400 watts / 7.4V = 324.32 amps!

Will not take much of a mistake choosing a prop to make a 120 amp esc go poof.

You'll also need some high quality high C batteries, N setups are way harder on equipment than the higher cell count classes, when you give up volts you have to supply more amps.

I understand the logic here but is a Feigaio 540 7L motor 2400W? OSE lists it at 400-700Watts? Needing 240a for 7.4v seems a bit out of line. Not talking about a Nue here.

Mic

 

[MarkTanski]

The leopard is 2400 watts potential.

That cheap 7L @ 700 watts is still drawing almost 100 amps, and it will draw a lot more than that, an electric motor will just keep drawing current until something goes up in smoke. With that motor you're stuck with prop sizes unless you want to bore out smaller props, I'd be pretty leery about trying a 38mm prop on that setup for a first run, I have serious doubts you will ever see a 40mm prop with a 120 amp esc. 3 blade 40mm forget it! Thats a spec 4s size prop! Your amp draw would be right through the roof, would probably over heat and de-magnetize the motor if the esc doesn't let loose first!

Do some research on other forums and check out what other people are using for 2s setups before you decide on anything, thats about all I can say. There are some of the best nitro racers in the world here but the electric side of this forum isn't as developed as some of the others.

 

[TinoAlmanza]

Needing 240a for 7.4v seems a bit out of line.

Mic

Sir I am no expert like many here but that comment is one that many people make. It's just the reverse. Higher voltages require less amps. It's much easier and cheaper to run higher voltage then higher amps. I think that's why you see so few N2 classes run anymore.

 

[Dick Loeb]

Im running Hydra 240 LV for N boats :huh: :huh:

 

[HTV Boats]

I was hoping there might be a chance of a cheap alternative here. Looks like trial and possible poof by loading too much. Not expecting anything near 40+ mph here either. How much would backing off in KV rating reduce the load. Say droping from an 7L at 3511KV to an 8L at 3072KV? Is there a formula or not knowing the total energy load/work to propell any hull the issue.

Thanks again for input. I have to say the more I learn about FE I really appreciate how well the UL-1 motor and 60 amp controller work together as a P limited setup. If there were N and Q equivilants you would have more converts from nitro than you know what to do with.

Mic

 

[SeanKewley]

A properly setup high voltage system will draw less amps than a properly set up low voltage system that generates the same power.

Here is a chart showing motor KV and voltage with the preferred RPM ranges. Hope it helps.

One of the best tools available to a FE boater is data logging. The new Castle Ice ESCs have this capability, as does the Eagle Tree eLogger. I use the Eagle tree and it takes a lot of guess work out of the equation.

kv_voltage.pdf

 

[jeepers]

I love N class boats, its a challenge to make small boat run well. We used to have a N2 spec class here in Colorado, It was based on 120amp esc, and a NEU 1509 1.5D 4500kv. My boat was setup with a Hydra 120, 1509 1.5d and 2s2p 10000mah,x438 I ran this setup for a couple of years, I also ran in the same hull and the SAME Hydra 120 with a NEU 1512 1D 4875kv with a y536 at the 2009 Michigan FE Nats. The Hydra 120 finally died after sticking a NEU 1515.5Y 4400kv motor in and a x640 prop, I also ran a Feiago 6L with a detounged x438 or x637 on a Hydra 120. It can be done just have to prop accordingly.

 

[hugh hargett]

Yeah Id think around 4000-4500 kv would be better for a 2cell boat . I dont think you will ever see 300 plus amps on a light and small boat. Note when it comes to the esc the more headroom the better and typically a higher amperage esc will have a lower on resistance simply because they usually have more fets thus more roads for the current to travel thus reducing resistance kinda like a traffic jam.If you have the cash for a NUE or a Lehner definately go that route not saying that a properly choosen chinese motor wont do the job but at the high rpms quality will start to show thru.Note if 2400 is the max watts and you plan on reaching that on 2 cells you better have a beast or a motor the average 540 china wont like more than 100 amps max. I would imagine that the 2400 watts was not measured at 2 cell voltage.I wouldnt be looking for max power anyway but rms power around 1700 watts.If you want 2400 watts continuous you need a motor that will put out 3400 watts max.

 

[HTV Boats]

I was not thinking anywhere near 2400w. I figure the Feigao 540's are in the less than 1000w range? Not sure why going to 4000+kv will be less of a load? Pushing an X438 or cut down similar prop with a 3500kv motor on 2S should be around 23-24000 rpm under load? Am I thinking wrong here?

Jeepers what hull and total weight were you running?

Mic

 

[SeanKewley]

Pushing an X438 or cut down similar prop with a 3500kv motor on 2S should be around 23-24000 rpm under load? Am I thinking wrong here?

Mic

That will make for a fine sport running setup. The higher kv motors mentioned above for the N2 class are for competitive heat racing.

 

[hugh hargett]

HTV you want more than 25k on those reletively small props around 30k will be better.You want the motor to do the most work it can without going past what the motor can take plus if you aim for rms power you will have some headroom and the overall performance will just be better.Peaks and Maxes are better off reserved for SAW setups.

 

[jeepers]

I was not thinking anywhere near 2400w. I figure the Feigao 540's are in the less than 1000w range? Not sure why going to 4000+kv will be less of a load? Pushing an X438 or cut down similar prop with a 3500kv motor on 2S should be around 23-24000 rpm under load? Am I thinking wrong here?

Jeepers what hull and total weight were you running?

Mic

HTV. it was a 26" inch long Hydro& Marine Lifter hydro, weight 5 lbs something oz, I don't remember, I retired that boat it had been tested on many setups from 2 cell to 4 cell lipo, 12 cell nimh with 700 series motors etc.

What your wanting to do with your tunnel and a Feigao 7L it would run strong with a 438x and still use a 120 amp esc. or you can go with an 8L and a x438 and be nice and gentle on the power system.

Hmmm... now I am curious what a 6L on 2s will do in my VS1!

 

[HTV Boats]

Just an update. I did try a Tacon 3500KV 3660-540L Car motor on 2S. Ran a X438 trimmed a little and it pushed a Vision 21 nitro size tunnel about 30-35mph. (T-120 ESC) Boat for the kids as it won't tear up anyone and I just wanted to experiment without blowing up anything expensive. The fuse here is the 120A esc. Just too expensive to put a real motor and 240a ESC to use 2S packs. Might need to try 3S but that would put a 3500 into the 40000 rpm range. Cheaper and faster to just stay in P spec/limited.

Mic