Outrunner kv questions monster truck

[welder820]

OK guys I have been building a CPE Wraith monster truck I have been looking at some motors ranging from 1100kv up to 1450kv 5mm shaft.I wanted to make sure I'd have enough wheel speed to race if I wanted I was going to run dual motors and 4ws on 3s or 4s running clod sized tires looking at Turnigy and Tacon motors .I've waited almost 2 years on Holmes list for restock and now I'll have to go another route also show casing build on YouTube.I welcome any and all advice do not want to run an inrunner.Thanks

 

[GLwagon]

in my 1/8th Scale Buggy I ran a 1400 KV in-runner on 5s and it was good.
1350kv to 1400kv with a 6s is a monster (depending on size of can and gearing)
I can't imagine a 4s or 3s for a monster truck, unless wheel speed isn't needed.
I have a 1200kv out-runner on a crawler on 3s & it is slow & methodical. (5-7mph tons of torque)
1000kv to 1400kv starts at 5s if I were racing.
More voltage + lower KV = less amperage for same speed/rpm & power
I have a chart for KV & Voltage if you know what your target RPM range is.

As far as in VS. out runner, the in-runners are more durable & less efficient.
Usable power is dependent on physical size & in-runners tend to be smaller for same torque.

 

[welder820]

That I am not certain about I was going to play with the gearing the fact I am going to run dual motors I figured I could gear up as temps allow.

 

[welder820]

I almost forgot I want to try to keep the weight down as much as possible.

 

[WHITE-TRASH]

Why dual motors? You say you're trying to keep weight down so now uoure going to throw 2 motors and 2 esc's at it? Stuff an 1/8 scale 2000-2500 kv motor in it and have at it.

I'm running a 2350 4 pole sensored 1/8 scale motor on 4s and it flat rips even geared low.

 

[welder820]

Ya I am still in the planning phase I ve used outrunners on other projects so just love using them a 2000kv would be nice but can't find one with a 25mm bolt pattern.

 

[GLwagon]

Best things are custom.
On a 5s a 2000kv is like a jet engine... & doesn't last forever, but is really cool.

 

[welder820]

OK reading some more on net I don't want a crazy fast rig it just need to be competitive in the monster jam type events like the racing and free style .I see on some forums 2000kv and up is good for monster Trucks but can I gear up a lower k motor to compensate?

 

[GLwagon]

You will be unimpressed with a low KV motor on low voltage.
2000kv on a 4s will draw a ton of amperage compared to a 1550kv on a 5s, 1350kv to 1400kv on a 6s

Thing that helps to know is needed runtime.
You may be able to use a 3600mah 6s pack VS. a 5000mah 4s
14.8v X 5.0ah = 74wh
22.2v X 3.6ah = 79.9wh

"Smaller" batteries at higher voltages can = moar power or "watts" on tap.
It will draw a lot less amperage & the ESC will live a lot longer.

I have never been unhappy with Tekin's big Buggy & Truggy motors I have a few of them.
The sensorless motors from Turnigy/Hobbyking can be great bang for the buck.

 

[welder820]

My question is what kind of speed are you talking because these types of events aren't huge tracks and most out runners can't handle past 4s for what I could find This is a clod style truck with a wraith tranny I don't want blistering speed it breaks and tears stuff up.

 

[GLwagon]

It is the 35-45mph & spinning the tires most of the way on dirt kind of power, that you can run for 10-15min solid thrashing it the whole time.
Think HPI Savage or single motor E-maxx able to do back flips...
Too much power, lol.
You can over volt a motor to a certain extent as long as it doesn't get hot.
This on a 3s to 4s might be fun, just gear it down a little. Leopard LBP3665 / 3D 2680KV 4 Pole Brushless Inrunner Motor | Value Hobby
This caught my eye, and it would likely run well on a 4s for what you are trying to do and will likely take a 5s with out complaint... https://hobbyking.com/en_us/turnigy-aerodrive-sk3-3542-1250kv-brushless-outrunner-motor-1.html it will need to have the shaft flipped.

 

[welder820]

They have on hobbkyking a 1450kv outrunner I think it's the d3542 or something by turnigy and a 1450kv outrunner in a can it's called the glider drive by turnigy it's in they're SK3 series motors.

 

[GLwagon]

If you can find a 3542 in 1450kv that would be a nice one to try.
Double check 5mm shaft, & you likely need to cut a flat spot in the shaft too.
I would start on a 4s for that.
I couldn't find a 3542 in that high of a kv.
3536 & 3530 are available in 1400+kv

https://hobbyking.com/en_us/electric-motors-1/turnigy-sk3/35mm.html

 

[welder820]

D3542/4 1450kv turnigy have to flip shaft and glider drive Sk3 1400kv they're under 34mm to 42mm outrunner motor size category.

 

[steveo 561]

There lots of guys that use out runners for fast brushless boats with kv up to 2000 and high cell count, I have a pair of hk typhoon 500 1800kv that have run 5s no problems.

 

[welder820]

What would happen if I run a 60amp Max motor on a Orion vortex r8 esc from a mad force ve on 4s have this esc lying around never used?

 

[welder820]

Would this esc hurt the motor it's a lot higher and rating than the motor I think 120 or 130 amps .

 

[GLwagon]

So here it is in a nut shell.
The amp rating of the ESC is how much it can handle before it smokes or dies.
The motors amp rating is useful for things like airplane props & boats, the ESC should be higher than this rating.
The "C" rating is part of a calculation on batteries for maximum output before possibly damaging the pack, example 5000mah @ 20c = 100amps max, 4000mah @ 30c = 120a
There is no true standard on "C" ratings, but companies that make batteries for airplanes tend to not inflate their numbers unlike car pack makers. [cough] MaxAmps [/cough]

Example, my one plane has a 25amp ESC & a motor & prop capable of drawing 27amps full load.
I have "thermaled" my esc on long climbs. I should run a 30-35amp ESC, but that adds weight & cost. I just run 3/4 throttle most of the time.
The batteries for that plane are 1800mah & range from 15C to 30C.
The 15C pack also shows a struggle keeping up. 1800mah X 15C = 27amp max load.
The battery actually comes out of the plane luke warm at end of flight.
The 30C pack never flinches at being ran hard & has more punch on climbs & never warms up.
Heat kills things, motors ESC's, & even batteries. Monitor temps on ESC & Motor if it is a new setup.
I run 60amp ESC's in most of my non-race cars, & 100amp+ ESC's in the bigger stuff even if the motor will never draw near what the ESC is rated.

Do not run electronics over 160-180f.
Motor magnets will degauss if heated too much or burn windings (180f)
ESC's I try to keep below 150f.
The concern with Batteries is more about under-volting (3.2v per cell), over-volting (4.2v max per cell), & Storage voltage (3.8v per cell)
Not balancing EVERY CHARGE can throw bad cells way off over time.
I do not use LiPo cut in race cars, but set my LiPo cut at 3.4v in my other cars.

 

[welder820]

Ya I wanted to ask because I've never used this esc since it was new sat in a box.I found a motor that's a 1900kv boat motor 4s on hobby king 60amp.

 

[welder820]

I was wondering though should I run a dual motor setup or just a single motor.