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Engine KV and gearing for MT410

freelosophy

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Still waiting for the MT410 kit and going to bed late every night reading up . . . . I really need help understanding gear ratio and motor KV. Am thinking that a Castle Mamba X 25.2 WP ESC with the 1515-2200kV sensored motor. Sensored motor is good but this kV stuff. I know electricity ohms law, watts, amps and all that. But gearing is killing me. I get the fact that high gears give you higher end speed and stresses the motor more getting to speed. And lower gearing gives you more torque and less top end speed and less stress on the engine. And that's where my understanding ends. Hell this is a MT. I don't want to go 50 mph. I wanna do willies and flips and jumps at least try.
So what do you experienced guys say for a starting gear(s) and motor kV. I think that no matter what I do am gonna end up with a few gears . . .
Really appreciate the help! Not sure I would have attempted a kit without knowing this forum was here. This is a great Tekno support! Am confident I can follow directions and build this MT with quality. But figuring out the dam parts to put into it I thought would have been easier. It's actually challenging. For the radio I decided the Futaba 4PM and I'll figure out the telemetry receiver stuff later. The body and tires/wheels there are plenty of recommendations but gearing . . . these gears 15T and kV determines the rpm I just don't get it. Thanks bros, you guys deserve a beer or/and toke and I could help with both ;)
 
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tetsuo

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There are a ton of guys on this forum who can probably explain this much better than I, but I'll take a swing :)

kv is how fast the motor will spin at 1 volt with no load. So a 3000kv motor will spin at 3000rpm at 1 volt, and that 2200 you're looking at will spin at 2200, etc. As a general rule, with ALL other things being equal, a lower KV will give you more torque but lower max RPMs.

OK, so given all of that, now you add the pinion gear into the mix. You already seem to have the idea of what effect different tooth counts will have, so you can combine that knowledge with the kv info above. In terms of speed, a 2200kv motor with a 15t pinion will end up driving the vehicle to roughly the same top speed as a 1800kv motor with an 18t pinion.

The next factor to consider is if you're running 4s vs 6s. Actually the MT410 is so light, you can actually start out with a good high C 3S battery and you'll still get enough current to wheelie all over the place and have a more beginner-friendly top speed :)... but that's a digression. Anyway, if you're running 6S, you're upping the voltage 50% over 4S, so you're going to be running everything hotter and faster. That's why people going w/ 6S often pick a lower kv motor. They're still going to be spinning faster with 6S+1800kv than 4s+2200kv, but they can drop down on pinion size and put less strain on the motor.

BTW - one final thought. I run the Castle MMX/2200kv sensored combo with a 16t pinion on 4s and LOVE it. Wheelies and backflips for DAYS and more than enough speed for my needs. If I ever do run 6S, I'll put a smaller pinion on there and stick w/ smaller diameter tires as well (like the backflip LPs)
 
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freelosophy

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Wow, dude, it clicked. Got it! so you guys talk about it overheating because you loading up the engine too much with the gearing and it strains at low speeds trying to ramp up. I guess the other end is over reving the rpms. So I will start out on a 3S and maybe 4S way in the future. I have the Granite BLX on 3S and it flies. Don't see any need for anything greater. So you help make up my mind. For MT410 it will be a Castle Mamba X 25.2 WP ESC with the 1515-2200kV sensored motor. Now I can to start saving up the pennies, this is not cheap but sure is fun. I suspect that I'll play with gear ratios in the future, but much to do before that. You'd think some of these motor manufacturers would put together some videos explaining how to calculate this stuff but I guess it gets kinda of complicated. Thanks tetsuo much appreciate you sharing your valuable knowledge!
 

Nicochau

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Tekno RC's
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  2. ET48
  3. MT410
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Let me give you a reference coming from my ET48.3, which should be using same diff pinions / overall gear ratio.

Truggy wheels are 143mm tall. Very common kv is 2000kv on 4s with 17t pinion being perfect for medium to high speed track.

With the same Truggy wheels, 2200kv motor, to keep the same overall ratio as my above reference, your pinion should be: 17t x 2000 / 2200 = 15.45t.

Now lets imagine you are using Backflips LPs that are 158mm tall. Same ratio applies. Your pinion to keep same overall gear ratio Should be: 15.45 x 143 / 158 = 13.98t.

14t pinions are a tad too small to clear against the plastic center brace. I would recommend 15t. But by doing so, you are already gearing taller than my above mentioned reference. This is why 2200kv is perceived as a slightly high kv motor for 1/8 scale. They are fun for bashing though and give great air control (higher tire rotation speed). Start there and don’t go too crazy on the tires, lighter / smaller can actually be better.

Hope that helps.
 

MikeBuzz

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Just worth noting that the mamba x with 1515-2200kv has a weight limit of 9lbs/4kg
 

MAVERICK

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I second mike buzz

Personally I love castle and I have there product in 5 of my rigs. 2 of them running the mamba X. My eb48.4 weighs in at 7.6 lbs. and it is a track only car and I would not feel good about added much more weight to it

I do not have a MT and don’t know were they weight in at. but if you are going to bash it and run in the grass with larger tires step up to the mamba monster X

I have it in a 15 lbs basher matched with a 2200kv motor and it is unstoppable
 

freelosophy

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mike, you make a good point dam it. Didn't notice it was max of 9 pounds. So am going with the
Castle Creations Monster X 25.2V ESC/1515-2200kV Motor which maxes at 15 lbs. But now you mentioned the SIDEWINDER 8TH SPORT 1:8TH SCALE which I saw and didn't consider because I thought it would not fit since it's 1/8 scale. Are you sure that it fits? Am gonna go check it out now. Thanks everyone for the feedback! The MT410 kit is still on back order now until late June instead of mid June. Am crying.
 

freelosophy

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Just checked it out, it's a good option, good pricing too although a little extra for the fan. Am leaning towards the Monster X with the same motor cause it seems a little more beefier. Lets see how the pennies come in the next few weeks, either would work well I think.
 

pconcemi

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  2. MT410
  3. SCT410
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@freelosophy Just FYI the MT-410 will be larger than your Granite, it says 1/10th scale monster truck but it is really 1/8th scale. The MT-410 has the same wheelbase and width as the 6s Arrma Outcast.
 

freelosophy

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got the MT410 kit and am loving it! got the chassis built adn next to the granite, well, can't compare it. But it's a LOT bigger. Since Tower Hobbies has the ESC/motor on back order (early July they say) i figured I'd wait to build the shocks until the shock tool arrived, can't do anything anyways and am bound to scratch up the shaft with my luck. I think am going to order a 15 or 16T pinion . . .? ? ? I just don't want it to deal with over heating.
 

freelosophy

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over heating is my realized fear. I set the max temp on the CC1515 2200kv motor to 160F and got the familiar - - . motor overheat beeps. Running 4S and mamba monster x esc and trenchers tires. Tried a 14T pinion yesterday and it still over heats. Mind you I run it on the grass almost full board to test it. Am I expecting too much? I run it with the nylon mesh cover on and have the cc single fan. Couldn't get the yeah dual fans to fit due to the m3c center brace. Any thoughts? Oh yeah and it Los Angeles and it's been really hot like in the mid 80 to low 80s. So any thoughts would be appreciated. I save and date logs and eventually I'll figure out how to keep it from over heating but this trial and error approach is rather slow with so many variables.
 

tetsuo

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over heating is my realized fear. I set the max temp on the CC1515 2200kv motor to 160F and got the familiar - - . motor overheat beeps. Running 4S and mamba monster x esc and trenchers tires. Tried a 14T pinion yesterday and it still over heats. Mind you I run it on the grass almost full board to test it. Am I expecting too much? I run it with the nylon mesh cover on and have the cc single fan. Couldn't get the yeah dual fans to fit due to the m3c center brace. Any thoughts? Oh yeah and it Los Angeles and it's been really hot like in the mid 80 to low 80s. So any thoughts would be appreciated. I save and date logs and eventually I'll figure out how to keep it from over heating but this trial and error approach is rather slow with so many variables.

I think 160F on grass might not be a realistic expectation even w/ a 14t pinion.

On grass with 80-85 degree ambient temps, mine regularly hits internal temps of 170-180 degrees F, but it levels off there. No heat sink or active cooling. I know that's right on the borderline for what Castle considers safe, but as I said... it does level off there. One thing that can help on grass is less grippy tires. My favorite on-grass tires are actually the minikawa LPs (4s). People tend to hate on them due to not having enough grip, but I like being able to kick the rear out on grass and they slide nicely on pavement too. You give up standing backflips and loose surface grip, but backflips off a ramp are still no problem and the handling is definitely more fun and progressive on grass than with more grippy tires like the badlands or dboots backflips. Added bonus is that a little wheelspin will help the motor run a tad cooler.
 

freelosophy

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you know, I had a gut feeling that these trenchers might be too big. Am going to do the same test on dirt and see how hot it gets. The logging feature is dynamite, without that I be totally lost instead of partially. lol.
I guess I gotta invest more $ in tires. getting expensive. . .
 
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