you've gotta see this

[kfxguy]

I went did a little more testing with my 26" mini rivercat today. The first outing was with a castle 1512 2650kv motor, x438 prop, 50c 5000mah 2s packs run in series. I was wondering if I went to a lower kv motor (same exact motor) with more voltage, pretty much the same rpm, would it be faster. Well today my question got answered first hand. I'm sure a few of already know, but doing it first hand is priceless to me. So here's the first run, 4s 2650kv

http://youtu.be/JgdDTQUI45E

now here's today. Switched motors. I didn't know castle made a 1800kv version until.a couple weeks ago when a member put one up for sale. I used 50c 5000mah 3s packs for this run. Motor ran cooler too at 95.5f. Other setup ran a little over 100 degrees.

http://youtu.be/14AD40SLvNw

tell me what you think. I feel like visually it's a big difference and sounds like the motor isn't straining as much. Here's the rpm difference, unloaded rpm with 4.20v per cell:

4s, 2650kv is 44,520rpm
6s, 1800kv is 45360 rpm

[tlandauer]

That second vid is music to my ears! The boat is great and I am glad you posted these vids.!

[srislash]

Travis, this is why I went with the 950 kv's in my Fantasm.They were supposed to be the upgrade for my Shocker (1820 kv), but since it's demise... Torque goes up with lower KV motors. This is an excellent example of this. Well done and thanks for posting. That little guy is rippin for sure.

[kfxguy]

Travis, this is why I went with the 950 kv's in my Fantasm.They were supposed to be the upgrade for my Shocker (1820 kv), but since it's demise... Torque goes up with lower KV motors. This is an excellent example of this. Well done and thanks for posting. That little guy is rippin for sure.

What?!!! This little thing is flyin! Lol! I could not believe how much it picked up. Goes to show you that just because it's supposed to turn "x" amount of rpm, that it really is. The 2650 kv motor just didn't have the tq to get the rpm's up high....I think mainly this could be attributed to the additional voltage. I thought it was a pretty great test. Next up is a x637 prop and I may (if I get brave enough) try my x642 prop with alot of checking on Temps. Pretty cool test!

[gsbuickman]

Thanks Travis ,

I agree with Shawn & Landauer, this is a perfect example of why I passed on the twin machine I seen on fleabay. It was advertised as a 60 mph boat with 5400kv leopards pushing 42mm 1.6 pitch props on 2s x 2 parallel. What a joke

High winding high rpm motors are more about all out speed, and not much torque. When you run lower kV motors like 900-1800kv, they're all about torque not all out speed. They have gobs of torque and are under far less loads at higher voltage where a high winder is beyond its max peak @ a lower voltage.

[keithbradley]

Travis,
What you're seeing here is EXACTLY what I was referring to in your other thread.

First, to get one part of this out of the way, your RPM calculations are wrong. 4.2v is never realistic, even on an unloaded motor. I know that's what we charge lipos to but in this equation it's totally irrelevant. On a loaded motor, you might see anywhere from 3.3v to 3.9v with most setups, depending on obvious factors. Increasing voltage and decreasing kv will cause you to be in the upper range, while higher kv and lower voltage will cause you to be in the lower range (or below that, even less than 3v/cell with some setups). This is only logical as the higher kv/lower voltage setup will result in a higher current draw.

Outside of that difference, you will see further differences if the motor is OVERLOADED, as perhaps it was in the first video (although I wouldn't expect a x438 to cause much of an issue to be honest). Beyond voltage drop, the inefficiency of the motor is increased because it physically can't handle the load that's put on it. There are actually extreme current spikes with setups like this that you will never see on a data logger, because they occur in between each pole "firing". Some of this can be slightly mitigated by fine-tuning timing but for the most part the result is inefficiency and sometimes fried ESCs (due to the nature of the current spikes in an overloaded motor it doesn't always manifest as dissipated heat measured at the heat sink after a run, but it does cause very brief periods of extreme heat at the FETs, which can of course lead to failure).

[keithbradley]

Thanks Travis ,


High winding high rpm motors are more about all out speed, and not much torque. When you run lower kV motors like 900-1800kv, they're all about torque not all out speed. They have gobs of torque and are under far less loads at higher voltage where a high winder is beyond its max peak @ a lower voltage.

I'm not sure that I agree with this statement. Can you elaborate more on what you're saying here in regards to lower kv motors not producing speed?

[gsbuickman]

I'm not sure thrt I agree with this statement. Can you elaborate more on what you're saying here in regards to lower kv motors not producing speed?

Sorry Keith, I guess I got a bit tongue tied there. I wasn't implying that low kV motors don't produce speed because we both kmow thats bs. Low kV motors produce speed, it just takes more voltage to do so.

like the mean machine that I mentioned above, that thing is a fireball waiting to happen. It may be quick, but its inefficient & reckless. If you take that same setup and run it on 1800kv / 5s, it will perform far better & be super reliable because the motors are under far less stress .

[kfxguy]

Thanks Travis ,

I agree with Shawn & Landauer, this is a perfect example of why I passed on the twin machine I seen on fleabay. It was advertised as a 60 mph boat with 5400kv leopards pushing 42mm 1.6 pitch props on 2s x 2 parallel. What a joke

High winding high rpm motors are more about all out speed, and not much torque. When you run lower kV motors like 900-1800kv, they're all about torque not all out speed. They have gobs of torque and are under far less loads at higher voltage where a high winder is beyond its max peak @ a lower voltage.

5400kv motors? Whoa, they are brave. Nah, just foolish. Lol

[Darin Jordan]

5400kv motors? Whoa, they are brave. Nah, just foolish. Lol

I have a SAW Hydro that has a 13,500KV motor in it... just installed it to replace the 12,500KV motor it ran previously... But then, I'm trying to achieve 80mph on 1-Cell, so you do what you have to do! Got 74mph from the previous setup... using a 120A car controller...

[kfxguy]

I have a SAW Hydro that has a 13,500KV motor in it... just installed it to replace the 12,500KV motor it ran previously... But then, I'm trying to achieve 80mph on 1-Cell, so you do what you have to do! Got 74mph from the previous setup... using a 120A car controller...

Well yea! That's only one cell on a pretty light boat I'd imagine :)

[iridebikes247]

Nice to see someone actually going to the lake and trying setups, naysayers will be naysayers, keep the testing coming and looks like your having fun doing it. Not sure the higher kv motor makes more torque it just derives power differently.

I could say you're gunna roast a motor and all sorts of bs and I hope these tests don't change people's perception of what is/isn't acceptable past a certain point....but who cares...they're just fun and you only learn by trying!

[kfxguy]

Nice to see someone actually going to the lake and trying setups, naysayers will be naysayers, keep the testing coming and looks like your having fun doing it. Not sure the higher kv motor makes more torque it just derives power differently.

I could say you're gunna roast a motor and all sorts of bs and I hope these tests don't change people's perception of what is/isn't acceptable past a certain point....but who cares...they're just fun and you only learn by trying!

I think it was said lower kv motors make more tq and probably more hp too because of increased voltage to arrive at the same rpm.

[flraptor07]

Awsome thread, goes hand in hand with your High RPM thread. Good job man!

[iridebikes247]

ah ok gotcha