Granite Jerry-rigged's Granite Mega 4x4

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Those tires were great up to 3s. On 4s, they just didn't grab, though. It was odd, the truck would not wheelie, unless I only gave it half or 3/4 throttle. Full throttle, it was too much wheel spin... LOL They didn't balloon much, so I was surprised when they blew.

I was trying to self-right - full throttle / full brake / repeat. it almost made it over, the front wheels hit the dirt and BOOM! rubber everywhere... LOL
 
So I downgraded a bit... LOL... Out with the BLX185, and in with a Racerstar f540, 3000kv. This is as much about curiosity as anything. For those that don't want / need huge power (kids) but need the truck to not constantly thermal shutdown, or burn bearings, like the stock combo does.

First run was with the Yeti 56t spur and a 10t pinion, WAY too much gear. So I swapped back in a stock 91t spur (more on this below) and a 20t pinion. Truck runs great, not huge power, acceleration near stock, but more top end. After 5 minutes or so, the motor was at 140f (on 2s)

That motor looks so tiny in there -
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BUT - Bad news on my Yeti spur conversion -

So my last run with the blx185, I noticed the spur mesh making a wa-wa-wa sound - a sign it is out of round, or off center. When I was meshing the pinion for the F540, again I noticed the spur was off center, but I ran it anyways. When I swapped the 56t out, I found my aluminum spiral spacer had been shredded -
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So before I go back in with the yeti gear, I need to come up with a better idea for a spacer.
 
For the size of the truck the castle sct/3800kv system would probably work well. That's what I run in my stampede 4x4 on 2S. I have MIP x-duty CVD's and I run 2.8" trencher tires on it with gearing that gets me right at 40mph. It gets warm, but doesn't shut down on me. I use SMC 7400mah 2S packs in it and I can run packs back to back on an 80F day in short grass, at the skate park and on dirt.
 
Thanks @olds97_lss - I am thinking I will probably look at picking up a Castle or Hobbywing system soon-ish for this truck. Question - are you running the Mamba X or the Sidewinder ESC? Also, I have read lots of stories about Castles needing BEC to run decently powerful servos - is this still true, or was that just with older Castle systems?

In other news, I ran a battery thru the truck, playing in the yard. Made a plywood ramp, and spent some time jumping - fun times. With this motor, it was smooth, controllable, 10' jumps. No chance of flips or such, but still, basic RC fun. After about 10-15 minutes, I did a 'finger on the motor' temp test and burned my finger... LOL Off to find my IR thermometer, took me about 5 minutes to find it, and when I got back to the truck, the motor was still 165f. So - looks like the 20t is too much gear. I'll drop in a 17t next, see if that helps control temps.

With these F540 motors, and their huge fins, the motor would probably benefit from a fan, but as a rule, I don't like to put fans on motors. Fans die too easy, and then you are pretty much guaranteed to overheat / burn out the motor.
 
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Thanks @olds97_lss - I am thinking I will probably look at picking up a Castle or Hobbywing system soon-ish for this truck. Question - are you running the Mamba X or the Sidewinder ESC? Also, I have read lots of stories about Castles needing BEC to run decently powerful servos - is this still true, or was that just with older Castle systems?

I run the cheap esc, the Sidewinder SCT SV3 and it came with the older unsensored 3800kv motor, it was $99 for both NIB on ebay. Now they only offer the 3800kv sensored motor for $106, but that esc is unsensored only, so you can't use the sensored part of the motor unless you get the SCT Pro or MMX. For me, I was just looking for a hopefully better performing waterproof replacement to use 2S in my stampede 4x4. The VXL system kept overheating on me with the gearing I liked to run.

The cheaper ESC doesn't allow you to adjust the BEC voltage and it's preset at 5V. I got an external BEC so I could run at 6V. Just a cheap one off ebay, $13 shipped, description "FVT 6A Adjustable UBEC For RC Car Airplane Helicopter, 5V, 6V, 7V BEC 2S-6S" and it works great. Plenty of power for the 2075 I have in there and I also ran it on a higher performance Hitec 5986MG just to see if it could run a stronger/faster servo. I tried the hobbywing UBEC and it was awful. Couldn't even power the low rent traxxas 2075 servo without causing the receiver to reset. Why castle would set it to 5V@3A fixed is kind of stupid. Who uses 5V anymore? 3A would probably be plenty for a servo in most vehicles it would go in. But 6V has been the norm for the past 20 years I've been into RC. I know way back in the day, they used to race indoors with little onroad cars at 4.8V, but geez. Offering anything now with less than 6V just seems stupid. Why output anything at all?

All that said, the 3800kv is on the lower end for torque, but it's very smooth compared to the VXL3500 system.

Here's some footage of it running at a BMX track:

I think I ran 2 or 3 packs through it back to back that day without issue. I don't think I was easy on it any of the time. It's just to fun beating the snot out of that truck. lol
 
I'm running the Kinexsis 3000kv with a 22t pinion on stock spur. It goes 27mph on 2s. I have the punch set to the lowest to preserve the input shaft on the rear diff. I really like how it feels with this setup.

I'm not sure on the temps right now. I have a temp gun showing up tomorrow. It didn't feel too hot to me though. It didn't burn my finger after 10 minutes bashing around the yard.
 
Is that Kinesis a proper 3650? And yeah, if you are not burning your finger, temps are good... LOL.
It's my first brushless, so I'm not sure. The motor dimensions in the manual are 37x52.
 

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I guess we could call that a 'nominal' 3650... LOL For motor size, the first two numbers are the diameter (36mm) and the second two are the length (50mm), so I guess you could call yours a 3752.
 
Looks like I need to do a Yeti spur conversion. My last run I heard the gear mesh more than usual. My temps were 200 on the motor and when I pulled it apart, the motor screws had loosened enough to F-up the gear mesh. The spur is still usable but has gotten slightly sharper.

I think I will go plastic 64t spur with 14t pinion to start. Jerry-rigged, do you have a parts list for what you used besides the spur and pads?
 
I am not sure the 64t 32p gear would fit. the stock 91t 48p is right a the limit of the housing, which is about 60t-61t in 32p.. I have not been able to find the 60T in plastic, only in steel. I'd rather run plastic spurs so long as they are not stripping, and at 32p, they should be strong enough.

In other news, I rebuilt my slipper conversion. I used some .018" thick SS plate for the spur spacer, and a 10mmx4mm bearing inner race for the spring spacer. I need to re-shoot my video to show the update. I no long have confidence in my aluminum can spiral spacer. Or rather, I am confident it will fail sooner rather than later.
 
I am running either the 56t 32p plastic spur, or the stock 91t 48p spur, depending on what motor I have in the truck. I would like a 60t spur - then I could leave the spur / slipper alone when I swap motors. But, I can't find one in plastic, so I don't have a 60t 32p spur.
 
So this weekend, I got some RC time... :) Got my new yeti spur spacer installed, shot some video to update my spur conversion video, re-installed the BLX185, this time with a 15t. The smaller pinion was to control tire speed, in hopes to no need to buy new tires after every run. I made a short run, didn't kill any tires, didn't break anything (yeah!) despite some impressive high speed crashes. Just going by feel, I think the smaller pinion is actually FASTER on 4s, vs the 17t. Seems odd, but with the 17t, I could run the truck, throttle pinned up an down the street. With the 15t, the tires start ballooning, and I loose control - which is why the epic crashes... LOL. ( I had one high speed tag a a curb that sent the truck tumbling, then roof slide for 50', then bump the curb again to drop the truck back on it's wheels, pointed the right direction to drive off... Made me wish I had the Outcast roll bar with the flint sparklers in it... ) Temps were only 110-115, so no issues there. Maybe I'll drop a 13t in the truck before my next run. (my Chinese pinion set finally came in, so I have a nice variety of 32p 5mm bore gears now. :) )
 
So this happened -

20180624_204337.jpg


I guess my idea of dropping the motor pinion tooth count to lower tire speed was not a great idea. Too much torque thru to the diff... LOL. Oh well, it was a fun bashing session, until FWD. Finally was getting the truck to backflip off a ramp. :)
 
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