View Full Version : PN Racing 43t motor

ghost chili
2019.01.27, 11:30 PM
Just looking for some confirmation about the PN Racing 43t ball bearing motor. I am pretty sure it should be safe to run with the unmodified FWD electronics? I've been running the 50t BB motor and I'm looking for a little more speed. I read somewhere the FHSS electronics package on the MR-03 and MA-03F had been improved to be able to run hotter motors? What kind of motors are you guys running?

2019.01.28, 12:12 AM
You should be fine running this on the FWD electronics. The RPM is lower than with a 50t, but torque is higher. For similar speeds, you would need to have a higher gear than the 50t. There is a higher static magnetic field on the 43t with use of neo magnets in the can, where the 50t uses earth magnets. This provides significantly higher low end torque. Which might be more than the diff/swingshafts can handle. The 50t would be more linear and a flatter power curve.

I dont have a FWD, but used the motor in AWD and like the feel of it for that application. 50t has a feel of a 70t with a longer power curve, where 43t has similar gearing choice to the 70t but loads of lower range torque.

ghost chili
2019.01.28, 09:25 AM
That was super informative, thanks! Do you know the lower limit for turns the FWD can run? I'm kind of leaning towards a motor with higher RPM since the FWD has limited traction compared to the AWD or RWD so I think the additional low end torque would be wasted. I am still running the stock diff and driveshafts, but I am hoping the reduced traction would spare them any damage.

I'm not well-versed in motor tuning nor the science behind it, but if I am understanding correctly, a stronger magnet will reduce max RPMs, but increase torque and vice versa? So if I tinkered with a 43t motor by keeping the armature and replacing the neo magnets with weaker earth magnets, it would result in possibly higher RPMs than the 50t motor?

2019.01.28, 10:02 AM
You would get higher RPM at the expense of amperage drawn and heat. It would not be worth it, just gear the 43t to the highest gearing... what are you gearing the 50t at?

Having studied the data on the fet used with the rwdŕfwd electronics, it is roughly 3x more current capability and lower resistance than the ASF brushed fet. They use two of these in each charnel on the drive circuit on the ASF cars, which places the rwd/fwd capacity for amperage about 1.5x the ASF electronics.

This data is purely the fet, I am not an electronics engineer, and can not say whether the are other limiting factors in the board design.

As you go lower in wind, rpm and the torque curve flattens. The amperage draw also increases. I have no knowledge of the gearing options for this chassis, but would think that a 39 or 37t would be a happy medium in general.
33t is very flat

ghost chili
2019.01.28, 11:58 AM
I am running the 50t motor at a 5.97:1 ratio (17t pinion 29t spur). With fresh batteries, the FWD spins its front tires easily even on carpet and with Kyosho 20 degree soft slicks. Lowest gearing available is 7.23:1 (15t:31t) and tallest is 4.50:1 (21t:27t).

Here is the manual for the FWD with gearing options on page 34:


2019.01.28, 08:01 PM
I would try gearing up before thinking about a new motor if you're spinning tires already. Fastt motors are going to spin them even more

ghost chili
2019.01.29, 08:14 AM
Will do. Thanks again for the great info! Strange how the manual blanks out the 21t:29t combo, yet it works just fine when I tried it. I was thinking the pinion wouldn't clear the motor housing, but it does with room to spare and the gears mesh nicely.

2019.01.29, 06:30 PM
That is good information to know. I know that there were gear ratios blacked out on the AWD cars, which in fact did not work properly. 21/29 being one of them if memory serves correct.

2019.01.29, 09:28 PM
I would try gearing up before thinking about a new motor if you're spinning tires already. Fastt motors are going to spin them even more

I agree with EMU. If you go with a lower gear ratio, you're probably going to get less wheel spin in addition to faster speeds.

I'm currently running the stock motor with the 19T/27T combo and its plenty fast on a large RCP track. As it is, its hard to keep it going straight at high speeds due to it having toe out in front.

ghost chili
2019.01.29, 09:34 PM
Yeah, I'm very much hoping to see Kyosho release the tie rod set so I can eliminate the toe out. I'm half tempted to get a spare one just to see if I can't use a heat gun to modify it slightly.

So far, it seems the 21t:29t gearing is working well. More speed with little wheel spin. It will still spin with freshly charged batteries, but it quickly dies down and seems to be a happy medium. I did order a 43t motor just to give it a try.