Granite Help me choose a brushless motor size

[Jakelandry]

Hi guys, I am relatively new to the RC world. I bought my Arrma granite 4x4 about a year ago on a rare Louisiana snow day just to play in the snow and sadly it only got used a handful of times between then and now. I was just too unsatisfied with only having a single stock battery and a bit too intimidated to go out and invest a lot of money in lipos and brushless motors. Well fast forward to now and my wife bought me a 2s LiPo for Christmas so that was enough of a kick in the pants to get me going again. I have since sourced a second 2s LiPo with the intention to bash around my front yard on 2s but run them in series when I get serious.

So to my question. It seems I’m limited to a 13t or 17t input gear in hd form so I’m gonna have to pick a motor size around that. I’d like to break into the high 50mph range on 4s and be able to beat around my yard at 30 ish, in the grass not asphalt, on 2s. I am very interested in a mamba x ESCs so I basically need help picking a motor that can handle the above conditions without getting too hot. I’ve seen a few videos online of motors in the 5700kv range but I want to make sure that something that size will be compatible with the limited gearing we have with upgraded input shafts. If any further information is needed feel free to ask otherwise thank you for any help in advance.

 

[bicketybam]

Hi guys, I am relatively new to the RC world. I bought my Arrma granite 4x4 about a year ago on a rare Louisiana snow day just to play in the snow and sadly it only got used a handful of times between then and now. I was just too unsatisfied with only having a single stock battery and a bit too intimidated to go out and invest a lot of money in lipos and brushless motors. Well fast forward to now and my wife bought me a 2s LiPo for Christmas so that was enough of a kick in the pants to get me going again. I have since sourced a second 2s LiPo with the intention to bash around my front yard on 2s but run them in series when I get serious.

So to my question. It seems I’m limited to a 13t or 17t input gear in hd form so I’m gonna have to pick a motor size around that. I’d like to break into the high 50mph range on 4s and be able to beat around my yard at 30 ish, in the grass not asphalt, on 2s. I am very interested in a mamba x ESCs so I basically need help picking a motor that can handle the above conditions without getting too hot. I’ve seen a few videos online of motors in the 5700kv range but I want to make sure that something that size will be compatible with the limited gearing we have with upgraded input shafts. If any further information is needed feel free to ask otherwise thank you for any help in advance.

I am so glad you posted. There are a lot of things that you need clarification on and we are here to help!

First I am going to assume that you have the mega version of the granite. That truck comes with a 17t input gears. The 13t input gear is for the newer 3s BLX trucks and there differentials. It will not work with your differentials. That said, upgrading to the 3s BLX differentials and input gear is something to think about, especially if you plan on running more than 2s. That brings me to the spur gear and slipper assembly. The Mega uses smaller 48p size gears for the pinion and spur. While this is fine for brushed applications and mild 2s brushless applications, it won’t hold up to 3s. And forget about 4s. You would need to heavily modify the truck to run 4s and you don’t need 4s to accomplish what you want to do. If you want reliable 50 mph speed, you need to run 3s and you really need the 3s BLX spur gear/slipper assembly (along with a 32p pinion). And the pinion, not input shaft, is what you use to control gearing (well, everything has an overall effect on gearing, but the pinion is what is most commonly changed to change gearing).

As far as the Mamba X esc goes, it is a very nice (and pricey) esc. I run one in my Senton. For the 4x4 Granite, you want a motor that is somewhere between 3000 and 3800 Kv. 5700 is WAY too high and is reserved for lighter 2wd vehicles. I run a castle 3800kv motor in my Senton.

Now with all that said, by the time you upgrade everything and especially if you go with the Castle esc/motor, you are going to be pretty close to what it would cost to buy a new 3s BLX truck and you would have instant gratification. I highly recommend you go that route (you could sell your Mega or keep it for spare parts). However if you want to convert your existing truck we are here to walk you through it. I hope I didn’t confuse you too much!

 

[Jakelandry]

Dang that is immensely helpful. I agree with you that buying the blx is undoubtedly the smartest move here, but I think I am pretty firm in keeping what I have. It really does sound stupid when I put it all on paper especially since I essentially plan to replace every part on mine that comes pre upgraded on the blx, but I am an engineer and I enjoy breaking and fixing things gradually over time.

The thought of swapping drivetrain doesn’t bother me at all. A 20 dollar gear here and there is perfectly fine with me, but purchasing a $200 ESCs and motor is a bit offsetting when I am not terribly knowledgeable. Luckily, I actually do not plan to run “reliably” on 4s. I am not disciplined enough to run on 4s at all honestly but I intend to do it occasionally for fun. Whatever breaks is perfectly fine as I understand the risk. So with that being said, I greatly appreciate the help and will look into motors in that range.

I considered a blx185 at one point but I noticed from brief review that castle seems to be one of the most reliable so I started looking into them instead. I am up for suggestions outside of castle but I feel like if I am going to spend 150+ on an esc and motor I’m willing to spend a bit more for reliability in that area. Broken 20 dollar parts are fine but as I said I’d like to keep the expensive parts in one piece.


Edit: I apologize. I am at work and as a result a bit scatter brained. I believe I would like to stick exclusively to 2s/4s for now and the castle “programmability” features are appealing to me because it seems I can somewhat tune down the 4s to 3s tier. The reason i’d like to stick to 2s/4s is because my wife grossly overspent on battery’s at the local hobby town and I don’t have the heart to return them as they were a thoughtful gift in my opinion.

 

[bicketybam]

Dang that is immensely helpful. I agree with you that buying the blx is undoubtedly the smartest move here, but I think I am pretty firm in keeping what I have. It really does sound stupid when I put it all on paper especially since I essentially plan to replace every part on mine that comes pre upgraded on the blx, but I am an engineer and I enjoy breaking and fixing things gradually over time.

The thought of swapping drivetrain doesn’t bother me at all. A 20 dollar gear here and there is perfectly fine with me, but purchasing a $200 ESCs and motor is a bit offsetting when I am not terribly knowledgeable. Luckily, I actually do not plan to run “reliably” on 4s. I am not disciplined enough to run on 4s at all honestly but I intend to do it occasionally for fun. Whatever breaks is perfectly fine as I understand the risk. So with that being said, I greatly appreciate the help and will look into motors in that range.

I considered a blx185 at one point but I noticed from brief review that castle seems to be one of the most reliable so I started looking into them instead. I am up for suggestions outside of castle but I feel like if I am going to spend 150+ on an esc and motor I’m willing to spend a bit more for reliability in that area. Broken 20 dollar parts are fine but as I said I’d like to keep the expensive parts in one piece.


Edit: I apologize. I am at work and as a result a bit scatter brained. I believe I would like to stick exclusively to 2s/4s for now and the castle “programmability” features are appealing to me because it seems I can somewhat tune down the 4s to 3s tier. The reason i’d like to stick to 2s/4s is because my wife grossly overspent on battery’s at the local hobby town and I don’t have the heart to return them as they were a thoughtful gift in my opinion.

If you want to run 4s you will need a motor that is 2650kv or less. I ran this one: http://www.castlecreations.com/en/1512-2650kv-sensored-motor-060-0061-00

I would suggest using Jennys RC for the BLX parts. You need 2 diffs, turnbuckles, input gears, spur gear/slipper, motor mount, metal wheel hexes and a pinion gear. Cost is around $86. The Mamba X and 1512 motor will set you back around $281. You would then need to Houdini up a solution for the wheel driveshafts because they will not last under 4s power. Arrma has an upgraded version coming out at some point. It would be $80 for all 4.

 

[Jakelandry]

Thanks a ton for spoon feeding all of that to me. I suppose I now need to do some more research and find what kv around that range would suffice as a happy medium between 2s and 4s in terms of speed correct?

 

[bicketybam]

Thanks a ton for spoon feeding all of that to me. I suppose I now need to do some more research and find what kv around that range would suffice as a happy medium between 2s and 4s in terms of speed correct?

Yes. It will be challenging to find a motor that will perform well on both. The 2650 is probably your best bet. You really can't go higher than that and run 4s. And it will be slooooooow on 2s.

 

[ptr1ck]

Don't do 4s, seriously. Get a truck already made for it like an Outcast if you want 4s.


For what it's worth, I really like my Granite with a $80 Kinexsis (Horizon Hobby) 3000kv.

 

[Brewcity414]

Just soaking in knowledge

 

[Jerry-rigged]

As someone that has been trying to run 4s on my Granite mega, (with a BLX185 ESC and motor) I'll add that it is a bad idea - But fun... LOL (yeah, I am no help) But my truck is broke more than it runs. I really am thinking I need to step back to either a 3660-size motor in 3800kv (I have this motor in a SCT already) and run the truck on 2s/3s, or maybe buy that castle motor @bicketybam was talking about (the 1415) in 2600kv for 3s running...

Another combo I am thinking about is the MAX10SCT with the 3660 in either 3200 or 4000 kv. About $140. Much better than the china combos, very similar to the Castle in quality, not as many tuning options, but still pretty programmable.
https://www.amainhobbies.com/hobbyw...3660sl-motor-combo-3200kv-hwa38010200/p607213
If you want to save some money on the motor, the china motors are pretty reliable - more so than the china ESC's. You can get a GoolRC/Racerstar 3660 or 3670 for like $20-$30 if you shop around. But you would still need a decent ESC, and then be close to a MAX10 combo.

Also, a note on motor sizes - that 3660 is XXYY - XX is motor diameter, YY is motor length. So a 3660 is 36mm diameter, and 60mm long. Bigger motors make more power for the same KV. As a reference, the BLX100 motor in the BLX3s trucks is a 3660, the Castle 1415 is about 3670, and the BLX185 is 4074. A 'standard' 540 is 3650.

 

[wricksta]

^great post

Over motoring a car is freakin awesome, but spending time fixing stuff sucks @ass! I learned that back in the 90's. I bought a Stampede when it first came out. I decided I wanted to put a Kinwald Dirtinator III 10 turn triple in it with a Tekin Titan ESC and run a 7 cell hump pack. That truck hauled ass(for it's time). Note: ESCs were not nearly as programmable as they are now. If I tapped the brake just a little, I stripped the idler gear in the tranny. I ripped apart that tranny SO MANY times. That was my lesson on over motoring lol.

I love the 3660 4000kv motor in my BRCC, Jerry-Rigged. I run the max10 SCT too. It's very smooth, haven't gotten a chance to put the BRCC on the track yet, but I'm thinking it'll do pretty well.

 

[Jakelandry]

This is all a lot of very good information. I want to make sure i don't come off as hard headed here when I say this but I would like to stress that I do intend to run on 4s and here is why:

1) It is my understanding that with some respectable ESC's I have the ability to throttle down the power whether its on the initial punch or peak power. This leads me to believe I can run 4s but have it perform as a 3s would, giving my two 2s battery combo the power range of 2s to 4s without purchasing a 3s battery. If I am completely wrong on that I would love for someone to chime in and elaborate on the extent of control I actually will have with a programmable ESC. From my brief research, I believe the above logic to be accurate.

2) I would like to take advantage of the battery combinations I have available. I have two Venom 5000 40c's which seem to be pretty overpriced in the current market, but they're what my wife got me and I'd like to use them. I am not against purchasing a 3s battery, but why not spend that money on the BLX parts I already intend to buy anyway (provided my ESC logic above is sound)?

3) I am ok with parts breaking regularly. Sadly I am not satisfied unless I have found the limits of what mechanical things can do so even if I were to buy a more appropriate vehicle, I would just do the exact same thing with it. I actually build race cars as my primary hobby so I pretty much build and break things almost weekly.

I suppose I should elaborate a bit more as to why I am so hung up in the 2s/4s combo. My initial thought was that with two 2s batteries I could beat around the yard for twice the time on 2s or really beat around the yard for 1/2 the time on 4s (or a throttled down version) depending on what I felt like doing that day. Apparently I was wrong in that assumption due to the fact that I am trying to make something do two things well which will result in a motor choice that does neither well eg. slow on 2s and breaking things on 4s.

I hope all of that did not come off as arrogant or me being stubborn and apologize for using "I" so much lol. I am taking everything you guys say into consideration and am thankful for all the help.

 

[bicketybam]

When I ran my Granite on 4s, I couldn't make it through a battery pack without breaking a wheel driveshaft. Not. One. Pack. At the moment there aren't upgraded wheel driveshafts. If your idea of fun is running for 5-10 minutes and then replacing the wheel driveshafts at $18 a pair, then knock yourself out. I am not trying to be a peepee, but that is the reality of things. Go search @Megasty and check out his build for a 4s Granite. If you are into that level of fabrication then it just might be the way to go. When the 3s BLX rigs came out, I bought one and retired my converted 4s Mega (esc and motor went into a Losi Rock Rey). My 3s BLX did everything my 4s Granite did without breaking every 5 minutes. I do still break the wheel driveshafts from time to time though.

 

[Jakelandry]

Do the axles/ wheel drive shafts break from being at too extreme of an angle maybe? It would seem logical that after raising the truck for bashing purposes and introducing more offset that could contribute some. I understand nobody is going to lower these when bashing to try and save axles, I am just curious if they break from too much torque, bashing at higher speeds, or maybe the angle.

 

[bicketybam]

Do the axles/ wheel drive shafts break from being at too extreme of an angle maybe? It would seem logical that after raising the truck for bashing purposes and introducing more offset that could contribute some. I understand nobody is going to lower these when bashing to try and save axles, I am just curious if they break from too much torque, bashing at higher speeds, or maybe the angle.

Torque. It's a about the torque. That big Castle motor on 4s just twists the U-joint apart.

 

[DoNoHarm]

I happen to be on the team sidewinder 8th side instead of the mamba X side. More powerful, cheaper, and still 6s supported. If you don't need a monster system though I guess mamba x is for you, but then again why not go hobbywing max10 sct?

 

[Jakelandry]

I wouldn't say that I am against any particular brand or set on a mamba. I am a pretty data driven person and it just seemed pretty appealing from my brief research that I can have as much access as the castle systems allow. Do hobbywing or other brands typically allow full modification access via laptop? If so I would be more than happy to look into them. After hearing what bicketybam has said I will definitely need the capability of fine tuning the throttle/power at a minimum.

I would rank my priorities as follows:

Reliability - want to be weatherproof/ heat stable

Tunability - want to be able to turn down 4s power at a minimum. Datalogging sounds appealing as I regular tune racecars

Speed capability I really just want a car that can do 30 in grass and feels faster when I move up to a detuned 4s. Hopefully tomorrow I will have a few hours to set aside and look into everyone's suggestions.

 

[wricksta]

What racecars do you build? What EMS systems are you tuning with? Sounds like you are looking to dive into tuning an ESC like you would an EMS of one of your cars. I understand where you are coming from. I used to load a summer tune on my EMS, a winter tune into it, a pump gas map, a c16 map, etc. You are able to plug into your laptop to tune and datalog with most of the popular brands of ESCs.

In RC, the only time I was on my laptop tuning on the ESC is when I raced. I'd pull timing or add timing based on ambient temperature and track conditions(if I needed to). That probably happened once, they laid down too much calcium on the track(dirt 1/8 e-buggy) and there was so much traction with 100 deg weather, guys were burning up ESCs and motors. For the most part(especially on a basher), it's set it and forget it. I've found that I can get my ESC dialed in, then use my radio to compensate for a minor things. I spend way more time tuning suspension, and general maintenance than I do tweaking the powersystem.

2 years ago, I had a spare SCT truck that I wanted to run 4s. It already had a Tekin RX8 in it, so I threw in one of my 1/8 buddy motors in it, Tekin T8 1900kv. The SCT I was racing ran a Tekin 4 pole 4300HD motor, on 2s. Top speed was the same, the 4s had a little more low end, but was 3 sec a lap slower. It was heavier so I couldn't carry as much speed into the corners, and slower out of turns. I could get on throttle faster and harder on the 2s setup, but had to roll into it with the 4s setup. You will be carrying more weight on a 4s setup, make sure you make appropriate changes to the suspension. You build cars, so you know it's all in the setup.

I really do think that a 3s setup is all these trucks can handle, and like mentioned earlier, there are zero companies that make upgraded driveline parts for the 3s BLX cars. Some of the guys mentioned some good setups. Ultimately it's on you, if you wanna run 4s. I'll keep up with your build.

 

[bicketybam]

I forgot to mention shocks. You will definitely need to change them. The weight of the batteries will destroy the stock mega shocks.

 

[tow_glinka]

Just a Little idea:
What do you think about the Idea of getting a new Radio with Dual rate adjustment for the Throttle?
Dual Rate (as far as I understand it, correct me if I'm wrong) lets you adjust the end point of your channel. So, if you adjust your Throttle to 50%, your car will only have about 50% Power and Top Speed at Full Throttle.
That way, you could just get yourself a Brushless Combo that runs good on 4S, run always on 4S, and set the Dual Rate to the Power and Speed you like at the Moment (you can even adjust that on the fly from your remote).
Also, a quality Radio is always a good Thing.

As a sidenote, the others are right about changing your shock setup. But, if you always run both batteries at once (4S or 2S with double capacity) you would just have to adjust it once.

 

[Jakelandry]

Rather than do a big post with 3 long quotes that'll make this even longer, I'll just answer everything between my last post.

I mostly tune turbo imports but have recently jumped into the modern v8 world since they all now use similar technology the imports have been using for a while like variable cam timing on dohc motors. Ive used a few different softwares over the years on various cars from stock ecu's with flashing capabilities like hptuners or dsmlink to full standalones like megasquirt and proefi. Ordinarily I would agree with you that I probably wouldn't tune an RC much but in this particular case I would be searching for that balance between breaking everything and how much power I could get down with 4s (which now seems to be similar power to 3s at best) so I feel like it would be a guess and check scenario in the "tune" for a while. It's pretty interesting reading your post about racing them though as that's not the outcome I would expect from my ignorance to the RC world. The extra weight will definitely be something I need to be thinking about lugging 2 batteries around.

I have "upgraded" shocks to the cheap Chinese aluminum specials and tried a few different oils in them. I haven't really had enough speed to take advantage of them yet I think but just running around my yard on some rough terrain I feel they're pretty bouncy. I've tried different springs and just really can't find a happy medium. I also don't jump much or anything like that because I really don't have the speed to test a 4 ft drop on the shocks. I also don't have the adjustable suspension that the Blx has so it's hard for me to get too much advantage out of them as when I raise the car the toe gets all out of wack. I do plan to explore more options no doubt.

The dual rate receiver sounds exactly like what I planned to do with esc tuning. with the amount of changes I intend to do, that may be a smart route to take due to the fact that I can make changes on the fly. Thanks for that suggestion!

I am at a stage right now like I see in the car world all the time. People get on YouTube or read forums and see people making 800-1000 horsepower and see a few pulls on video then think that's what they want. I regularly have to explain to them that it's not even remotely practical and try to convince them to build a 500 horsepower car first. Typically when you ask them what the fastest car they've ever ridden in they'll say something like my uncles corvette and it's typically a stock 3-400 hp car. That's where I'm at here. I see a lot of cars doing 50+ mph on video for 3 minutes and I am interested, but I understand that that is more than I have ever come close to experiencing and I plan to purchase parts and respect the power accordingly.