Tech question
02-05-2018, 06:11 PM
#1
Tech question
Hi guys...
new to RC. Got my son a 2wd Stampede for Christmas, and he loved it, and honestly so do I! We've already broken the front skid plate, and the left side camber link bashing on it. Needless to say, we got the bug, and it is something cool for my younger sons and I to do together.
Since Christmas, I have bought a used 1/18 ECX Ruckus,( great little 4wd truck by the way), a Red cat Everest ten crawler, (lots of fun for a hundred and thirty bucks) and I bought a used HPI blitz.
My question is about the blitz.
It has been upgraded to brushless, with a sidewinder 3 ESC, and did have a 7700kv motor that came with the ESC, but the guy swapped the motor out for a Thunder Power 17.5 540 with variable timing. I am guessing that the 7700 kv just didn't have enough umphh to push the 1/10 Blitz.
Here's the issue, with a 3800 3s battery that carries 12.5 v fully charged, it gets smoked by our brushed Stampede. After they get going, the blitz is carrying about the same speed. I was under the assumption that a good brushless combo with the right battery would be a lot faster than a brushed motor.
The motor doesn't get hot even after 10 to 15 minutes of beating on it, and neither does the ESC. Now it has been cool out because it's winter, and I haven't put a thermometer on it, but it doesn't get hot enough to burn my hand when I touch it.
I know something must be wrong with something, but being so new to the hobby, I have no idea what to look for.
Any thoughts? Thanks guys, I appreciate it.
new to RC. Got my son a 2wd Stampede for Christmas, and he loved it, and honestly so do I! We've already broken the front skid plate, and the left side camber link bashing on it. Needless to say, we got the bug, and it is something cool for my younger sons and I to do together.
Since Christmas, I have bought a used 1/18 ECX Ruckus,( great little 4wd truck by the way), a Red cat Everest ten crawler, (lots of fun for a hundred and thirty bucks) and I bought a used HPI blitz.
My question is about the blitz.
It has been upgraded to brushless, with a sidewinder 3 ESC, and did have a 7700kv motor that came with the ESC, but the guy swapped the motor out for a Thunder Power 17.5 540 with variable timing. I am guessing that the 7700 kv just didn't have enough umphh to push the 1/10 Blitz.
Here's the issue, with a 3800 3s battery that carries 12.5 v fully charged, it gets smoked by our brushed Stampede. After they get going, the blitz is carrying about the same speed. I was under the assumption that a good brushless combo with the right battery would be a lot faster than a brushed motor.
The motor doesn't get hot even after 10 to 15 minutes of beating on it, and neither does the ESC. Now it has been cool out because it's winter, and I haven't put a thermometer on it, but it doesn't get hot enough to burn my hand when I touch it.
I know something must be wrong with something, but being so new to the hobby, I have no idea what to look for.
Any thoughts? Thanks guys, I appreciate it.
02-05-2018, 07:05 PM
#2
What is the variable timing set at if it's to low the motor will draw very little current and therefore produce very little power. A 7700kv motor definitely has a ton of power more then twice what that of the 17.5t which is possibly why he pulled it out is because it had to much power.
02-05-2018, 07:32 PM
#3
What is the variable timing set at if it's to low the motor will draw very little current and therefore produce very little power. A 7700kv motor definitely has a ton of power more then twice what that of the 17.5t which is possibly why he pulled it out is because it had to much power.
Really?
being new, I was kinda going by what the guy said, but he told me that the 17.5 was a stouter motor than the 7700 kv was. Looking at the website, castle creations, it says that the 7700kv is not suited for vehicles weighing over four pounds, and not recommended for short course trucks of the 2wd, or 4wd variety.
As far as the timing, it was set on like 3 degrees. I am gonna mess with the timing tomorrow, crank it up a bit and see what that does for the performance.
Thanks for the input.
02-05-2018, 10:16 PM
#5
A 7700kv is not meant for a short course it's not made for high torque applications. I's meant for high speed applications. It's meant for lightweight vehicles that go very fast like a modified touring car. 3 degrees is extremely low timing a lot of motors start to wake up around 40 degrees. If you have an ammeter you can set the timing using that and set it for a 6 amp draw. You can slowly advance the timing to get to a speed that you like while watching the motor temps. A lot of motors don't wake up until you get to around 40 degrees.
02-06-2018, 03:49 AM
#6
but the 7700 kv is a 540 "sized" motor as well. They are both brushless.
Thunder Power Z3R-S Stock Spec 540 Sensored Brushless Motor (17.5T)
I can' post a link cause I haven't accumulated enough posts yet.
02-06-2018, 05:11 AM
#7
A 17.5t motor regardless of brand, will only give you roughly 2400kv which as Faqya stated gives you less than half the RPM compared to the 7700kv motor. The only thing the 17.5 motor has over the 7700kv motor is torque. Which may be what he meant about "more stout". But certainly shouldn't be as fast or faster. To add, 17.5 motors are Spec racing motors and are not meant to be particularly fast.
02-06-2018, 06:09 AM
#8
I'll put it simply so you can see the difference on paper.
A 17.5t motor regardless of brand, will only give you roughly 2400kv which as Faqya stated gives you less than half the RPM compared to the 7700kv motor. The only thing the 17.5 motor has over the 7700kv motor is torque. Which may be what he meant about "more stout". But certainly shouldn't be as fast or faster. To add, 17.5 motors are Spec racing motors and are not meant to be particularly fast.
A 17.5t motor regardless of brand, will only give you roughly 2400kv which as Faqya stated gives you less than half the RPM compared to the 7700kv motor. The only thing the 17.5 motor has over the 7700kv motor is torque. Which may be what he meant about "more stout". But certainly shouldn't be as fast or faster. To add, 17.5 motors are Spec racing motors and are not meant to be particularly fast.
that makes sense. Thanks for the help. I'd like to make it more powerful and faster, recommendations on a motor?
02-06-2018, 06:56 AM
#9
Tech Apprentice
iTrader: (1)
3800kv is the right motor. First I would make sure your remote is calibrated correctly to the esc. I don’t own castle but believe you can change settings in the esc with a programming card that plugs into a computer. If your sure these two are correct you may need a smaller pinion gear.
02-06-2018, 07:06 AM
#10
3800kv is the right motor. First I would make sure your remote is calibrated correctly to the esc. I don’t own castle but believe you can change settings in the esc with a programming card that plugs into a computer. If your sure these two are correct you may need a smaller pinion gear.
02-06-2018, 07:13 AM
#11
I went through and redid the setup on the ESC. The sidewinder is programmed from the transmitter through a series of y/n commands/questions. Like setting one option one yes, full throttle, no, full reverse. It will also program with an App and a mini usb I believe, but it is not necessary.
02-07-2018, 05:55 AM
#13
It's the 2.4 that came with the truck.
The first step in programming the ESC is to callibrate full throttle, brakes, and reverse, and it accepted the commands fine according to the ESC feedback.
02-07-2018, 07:17 AM
#14
Tech Adept
These are some ways I look at brushless motors. A high kv motor less bottom end torque higher top speed but also more heat and shorter run times. A lower kv is the exact opposite. Numbers on brushless motors are opposite each other as well. A lower number turn (say 6.5t) brushless motor means a higher kv.
Gearing makes a difference in each one as well. You can gear a 17.5 motor taller to gain more top end speed but lose acceleration. So you will lose off line against the pede but may overtake it down the line. The pede I believe comes with a smaller pinion so initial takoeoff is fast but top end speed is not the best. So gearing can make a big difference in performance in one way or another. Gearing for more top speed creates more heat so watching motor temps become very important. Generally I like to try to keep temps below 160f and gear up or down from there.
Batteries or voltage being pumped in make a difference too. A 17.5 motor can accept a higher voltage battery whereas a higher kv motor can only take so much say a 2s lipo max. Just look at 1/8 scale with low kv 4s/6s setups.
Gearing makes a difference in each one as well. You can gear a 17.5 motor taller to gain more top end speed but lose acceleration. So you will lose off line against the pede but may overtake it down the line. The pede I believe comes with a smaller pinion so initial takoeoff is fast but top end speed is not the best. So gearing can make a big difference in performance in one way or another. Gearing for more top speed creates more heat so watching motor temps become very important. Generally I like to try to keep temps below 160f and gear up or down from there.
Batteries or voltage being pumped in make a difference too. A 17.5 motor can accept a higher voltage battery whereas a higher kv motor can only take so much say a 2s lipo max. Just look at 1/8 scale with low kv 4s/6s setups.
02-07-2018, 09:13 AM
#15
Tech Adept
One thing that will throw a wrench in the gears is that on the SW3 ESC you can only apply ESC timing since it is a sensorless ESC. In order to use the mechanical timing on the can of the motor you need to attach a sensor cable to the motor and to a compatible ESC