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Jun 10, 2019, 06:58 AM
Registered User
KiwiKrawler's Avatar
So I was about to pull the plug and go home disillusioned. But I remembered someone posted on here once that they found an improvement with prime with the battery further forward. As Iíd reconfigured everything in the boat the only place was right up front. Was gunna flag it as I thought it would be a waste of time with the battery right up in the bow. But then I thought what the heck. And gave it a go.

The result was a pleasant surprise...

Tear Into with battery in the front (1 min 6 sec)
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Jun 10, 2019, 12:29 PM
Just Plane Nutts
AirDOGGe's Avatar
Surprise, surprise. I agree it does better in the second video.

Just shows that every modded boat is unique. Mine handles like crap when the battery is forward. Go figure.


Glad you got it going nicely. Happy boating!
Jun 10, 2019, 12:49 PM
Registered User
My Bermy Lizard did the same thing. Spun out really easy with the batteries near the back. Tried them up front just to test and had a way better handling boat. Amps went up though as it is pushing more water with the bow planted but the handling is much better.

No difference on priming either way though......

Cheers
Jun 10, 2019, 05:02 PM
Registered User
KiwiKrawler's Avatar
Quote:
Originally Posted by AirDOGGe
Surprise, surprise. I agree it does better in the second video.

Just shows that every modded boat is unique. Mine handles like crap when the battery is forward. Go figure.


Glad you got it going nicely. Happy boating!
Agree every modded boat is different. Might be something to do with my ride plate effectively increasing the boats waterline length. As itís fixed under the boat starting from in front of the jets intake.

It wasnít a total success. Although it stayed on prime better the steering was not as good. All the turns in that vid are full lock on the steering and couldnít spin it to save myself. Now itís about finding the happy compromise and that all important happy place with the centre of gravity.

And you were right about the 4800kv motor. Not enough power to really perform with my three blade impeller. You can hear the difference in revs from loaded to free spinning unloaded. The boat was faster with the higher kvís but definitely not revving as it should.
Jun 10, 2019, 07:40 PM
Just Plane Nutts
AirDOGGe's Avatar
The difference in handling may or may not be because I mounted my nozzle with a 3 or 4 degree up angle to lift the bow. Not sure because I've never compared it to an un-modded Tear. Since then there has been increased activity on nozzles with adjustable nozzle angles, either at rest or adjustable on the fly.

I've since added a ride plate, but have no video of the boat running with it yet. At minimum it protects the fragile nozzle assembly from impacts, and I HAVE broken nozzles.
Last edited by AirDOGGe; Jun 10, 2019 at 07:57 PM.
Jun 13, 2019, 05:29 PM
Quote:
Originally Posted by KiwiKrawler
Agree every modded boat is different. Might be something to do with my ride plate effectively increasing the boats waterline length. As itís fixed under the boat starting from in front of the jets intake.

It wasnít a total success. Although it stayed on prime better the steering was not as good. All the turns in that vid are full lock on the steering and couldnít spin it to save myself. Now itís about finding the happy compromise and that all important happy place with the centre of gravity.

And you were right about the 4800kv motor. Not enough power to really perform with my three blade impeller. You can hear the difference in revs from loaded to free spinning unloaded. The boat was faster with the higher kvís but definitely not revving as it should.
What amp ESC was it out of interest?

Higher KV/lower voltage motors usually pull more amps than lower KV motors running higher voltage. Is it possible the motor couldn't draw enough current? I'd be surprised if that were the case though.

If not, then I guess the higher KV motors really do lack torque in this application which is strange to me because when it comes to road vehicles I have found the KV/torque thing to be mostly untrue apart from very start of transitioning from 0 rpm to turning where you might see an advantage in a rock crawler but otherwise, I have found things to be about the same, especially when the RPM is up at the level these boats run at.

A higher KV motor can draw more amps and torque is supposedly proportional to amperage. Lower KV motors make more torque per amp unit but the thinner windings allow less current through in the first place so require more voltage to compensate.

There can be no doubt from that video though that the motor isn't able to get anywhere near full speed.
Jun 13, 2019, 08:37 PM
Registered User
KiwiKrawler's Avatar
Quote:
Originally Posted by nowinaminute
What amp ESC was it out of interest?

Higher KV/lower voltage motors usually pull more amps than lower KV motors running higher voltage. Is it possible the motor couldn't draw enough current? I'd be surprised if that were the case though.

If not, then I guess the higher KV motors really do lack torque in this application which is strange to me because when it comes to road vehicles I have found the KV/torque thing to be mostly untrue apart from very start of transitioning from 0 rpm to turning where you might see an advantage in a rock crawler but otherwise, I have found things to be about the same, especially when the RPM is up at the level these boats run at.

A higher KV motor can draw more amps and torque is supposedly proportional to amperage. Lower KV motors make more torque per amp unit but the thinner windings allow less current through in the first place so require more voltage to compensate.

There can be no doubt from that video though that the motor isn't able to get anywhere near full speed.

The esc Iím using is pictured below. Was what I had lying around at the time so threw it in. Must admit Iím still on the steep part of the learning curve when it comes to the electrical side of things at present. So your thoughts and advice are welcomed.

I do have a 60amp hobbywing esc that was bought for the nqd. But as Iím currently chopping and changing motors and trim setups I thought Iíd stick with the esc I had for now...and just make one change at a time. The fact itís gone quicker with the 4800kv motor than the 3000kv 2445 inrunner...and 3400kv 2632 out runner (even thought the 4800 was loosing so much rpm loaded)...tells me this setup can handle more revs. And I really wanna see how quick this thing will go. Already I am really impressed when you consider itís only a 19mm jet drive.

And on that note...I have a 25mm drive that is a perfect drop in for the tear into. So watch this space for that in the near future. 😬
Jun 14, 2019, 01:19 AM
Just Plane Nutts
AirDOGGe's Avatar
Quote:
Originally Posted by nowinaminute
What amp ESC was it out of interest?

Higher KV/lower voltage motors usually pull more amps than lower KV motors running higher voltage. Is it possible the motor couldn't draw enough current? I'd be surprised if that were the case though.
An ESC that can't handle the current demand usually releases it's magic smoke and then becomes just an empty container


It's battery mAh rating and C-rating among other things that determine if enough current can flow to suit motor demands. An under-rated ESC that cannot handle this power load will act more like a circuit fuse burning out than a resistor restricting flow.
Jun 14, 2019, 01:20 AM
Quote:
Originally Posted by KiwiKrawler
The esc I’m using is pictured below. Was what I had lying around at the time so threw it in. Must admit I’m still on the steep part of the learning curve when it comes to the electrical side of things at present. So your thoughts and advice are welcomed.

I do have a 60amp hobbywing esc that was bought for the nqd. But as I’m currently chopping and changing motors and trim setups I thought I’d stick with the esc I had for now...and just make one change at a time. The fact it’s gone quicker with the 4800kv motor than the 3000kv 2445 inrunner...and 3400kv 2632 out runner (even thought the 4800 was loosing so much rpm loaded)...tells me this setup can handle more revs. And I really wanna see how quick this thing will go. Already I am really impressed when you consider it’s only a 19mm jet drive.

And on that note...I have a 25mm drive that is a perfect drop in for the tear into. So watch this space for that in the near future. ��
I would definitely be interested to see if more current made a difference but even if it did, you would get better efficiency from a lower KV motor volted up to run the equivalent RPM.

Even though in car use I have found torque to end up pretty much equal, lower KV motors at higher voltage definitely run more efficiently. That's why larger 8th scale and upwards stuff runs low KV/high voltage setups. If you had an Xmaxx running on a 2s 6000KV the amp draw would be INSANE!
Last edited by nowinaminute; Jun 14, 2019 at 01:45 AM.
Jun 14, 2019, 02:15 AM
Quote:
Originally Posted by AirDOGGe
An ESC that can't handle the current demand usually releases it's magic smoke and then becomes just an empty container
I agree but some speed controllers have over current/over heat protection.

I'm not sure of the size of this motor though and what it's current draw would be?
Jun 14, 2019, 02:18 AM
Quote:
Originally Posted by KiwiKrawler
The fact itís gone quicker with the 4800kv motor than the 3000kv 2445 inrunner...and 3400kv 2632 out runner (even thought the 4800 was loosing so much rpm loaded)...tells me this setup can handle more revs. And I really wanna see how quick this thing will go. Already I am really impressed when you consider itís only a 19mm jet drive.
Now I'm wondering what size that motor is? Because the size also has a big effect on torque. Is it a 380ish size or smaller?
Jun 14, 2019, 01:35 PM
Registered User
KiwiKrawler's Avatar
Quote:
Originally Posted by nowinaminute
Now I'm wondering what size that motor is? Because the size also has a big effect on torque. Is it a 380ish size or smaller?
Itís a turnigy 2040
Jun 14, 2019, 02:02 PM
Just Plane Nutts
AirDOGGe's Avatar
Quote:
Originally Posted by KiwiKrawler
It’s a turnigy 2040

Oh...That one. A lot of people tried that motor ONLY because it had the same 2.3mm shaft size as the wimpy stock motor.

But a 20mm x 40mm inrunner is much too small for the Tear Into to reach it's potential, and the HIGH KV makes it even less appropriate. The rotating armature within is so tiny!

Specs:
Max Amps: 20A
Resistance: 0.0399
KV: 4800
No load current: 1.4A
Max Power: 220W
Li-Po: 2-3S
ESC: 25A


High KV is ideal in cars because the lower torque helps with traction control and doesn't strip teeth from gears as easily.


Run a 28mm diameter motor minimum with the NQD 19mm drive, preferably in the 3000-3500KV range. My 2850 3300KV pretty much maxes it out.
Jun 14, 2019, 03:17 PM
Quote:
Originally Posted by KiwiKrawler
It’s a turnigy 2040
That's definitely the main issue, the motor is simply too small. Even in 1/16 cars they can struggle. Not fundamentally bad motors and no doubt way more powerful than an equivalent sized brushed motor but I think just not powerful enough for this scenario.
Last edited by nowinaminute; Jun 14, 2019 at 03:41 PM.
Jun 14, 2019, 06:39 PM
Just Plane Nutts
AirDOGGe's Avatar
Yeah, I put a 2030 fitted with a finned heat sink in an 11" FT007 in place of it's stock 380 brushed motor, and even there it wasn't the answer. The fact that they are 2-pole brushless motors didn't help the cause.

https://www.rcgroups.com/forums/atta...mentid=9594662

https://static.rcgroups.net/forums/a...brushless8.jpg
Last edited by AirDOGGe; Jun 14, 2019 at 06:44 PM.


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