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Old 04-05-2017, 07:16 AM   #1
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Default USGT Motor Questions

I have done some asking around my local track and read some threads here but am still feeling confused so I am hoping someone can help lay this out in laymans terms for me. Just some quick background VTA was the first class I started racing and 17.5, I just used the motors the hobby shop said were the best and didn't do much research so this is my first attempt at researching and purchasing a motor.

1. It seems like the fastest guys are using short stack motors but I don't really understand what these are, what makes them better/worse and in USGT do they really offer an advantage, for example the Trinity 24KO vs the 24k short stack

2. Gearing seems to be really important, what works best in general for either a TC6.2 or a TC7.1

3. I have looked at Reedy, Tekin and Trinity (trinity the hardest) are their other brands I should consider for a 21.5 motor

And finally

4. While researching the Reedy motors I found that the fast guys using them were using the Reedy Sonic 540-M3 Motor SS 21.5 1S Spec, instead of the regular Reedy Sonic 540-M3 Motor 21.5 Spec. There seems to be a claim that using the 1S motor can actually be advantageous in certian conditions and offer more power then the regular motor in 2S touring cars. I do not understand this at all, and does it just apply to their motors or would the same claim apply to any other manufacturer.
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Old 04-05-2017, 10:51 AM   #2
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None of the guys I race with for the most part don't use short stacks or Reedy motors. I see Team Scream, Fantom, and Team Powers. I also see a few Trinity's but not as often as I see the other three motors mentioned above.
If you buy any of those motors the fast guys will still be fast but you will scare the heck out of them coming out of corners and down the straight.
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Old 04-05-2017, 11:14 AM   #3
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4. While researching the Reedy motors I found that the fast guys using them were using the Reedy Sonic 540-M3 Motor SS 21.5 1S Spec, instead of the regular Reedy Sonic 540-M3 Motor 21.5 Spec. There seems to be a claim that using the 1S motor can actually be advantageous in certian conditions and offer more power then the regular motor in 2S touring cars. I do not understand this at all, and does it just apply to their motors or would the same claim apply to any other manufacturer.
Reedy got approval for two different 21.5 wound brushless motors. The first, Sonic 540-M3 21.5 Spec was their initial design and ran well on two cells. The second, Sonic 540-M3 SS 21.5 1S Spec is their short stack stator set up for single LIPO cell batteries. This motor runs in a higher RPM band because the short stack design requires less total length of wire on the stator, reducing the resistance of the wind. This motor also uses a 12.3 diameter rotor to get more RPM from the lower voltage of the single LIPO cell battery. Associated felt the higher RPM was better for lighter pan cars such as 1/12 and 1/10 WGT-R than a higher torque combination typically used in touring car 4wd chassis.

So the racers, being as creative as we are, experimented with the short stack stator design and larger diameter rotors for use in 4WD touring cars and found they ran pretty well.

Having experience with another motor manufacture gives me confidence to say that the same is true for the other manufacturer's products as well.

I hope that explanation helps and you become satisfied with the next motor purchase you make.
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Old 04-05-2017, 11:28 AM   #4
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None of the guys I race with for the most part don't use short stacks or Reedy motors. I see Team Scream, Fantom, and Team Powers. I also see a few Trinity's but not as often as I see the other three motors mentioned above.
If you buy any of those motors the fast guys will still be fast but you will scare the heck out of them coming out of corners and down the straight.
Yes I don't expect to be beating the real fast guys anytime soon. I rather by a good motor upfront and be educated about the decision I am making hence the questions.
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Old 04-05-2017, 11:41 AM   #5
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Yes I don't expect to be beating the real fast guys anytime soon. I rather by a good motor upfront and be educated about the decision I am making hence the questions.
Don't let the motor thing get in the way of learning the hobby.
Ask yourself this..Are my laps consistent enough to justify a motor change?
Concern yourself more with running lap after lap within a couple or three tenths apart, then maybe the motor is an issue.

JMHO
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Old 04-05-2017, 11:45 AM   #6
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on a side note, which is the best body for USGT?
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Old 04-05-2017, 11:46 AM   #7
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Yes I don't expect to be beating the real fast guys anytime soon. I rather by a good motor upfront and be educated about the decision I am making hence the questions.
You'll do fine with any of the motors they've listed. Everyone has their own opinion on the best motor. My VTA car on sunday put down the fastest laps of the day and you know i don't have the fastest motor.
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Old 04-05-2017, 11:52 AM   #8
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on a side note, which is the best body for USGT?
Tamiya or HPI 2007 NSX.
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Old 04-05-2017, 12:24 PM   #9
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You'll do fine with any of the motors they've listed. Everyone has their own opinion on the best motor. My VTA car on sunday put down the fastest laps of the day and you know i don't have the fastest motor.
Remember I am not asking about which is the best motor, but more about the technical aspects, like what the heck is a short stack motor.
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Old 04-05-2017, 12:25 PM   #10
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Originally Posted by KE4PJO View Post
Don't let the motor thing get in the way of learning the hobby.
Ask yourself this..Are my laps consistent enough to justify a motor change?
Concern yourself more with running lap after lap within a couple or three tenths apart, then maybe the motor is an issue.

JMHO
In VTA yes, so I want to build my USGT car right the first time.
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Old 04-05-2017, 12:55 PM   #11
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In VTA yes, so I want to build my USGT car right the first time.
which car are you going to be using for USGT?
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Old 04-05-2017, 01:49 PM   #12
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Remember I am not asking about which is the best motor, but more about the technical aspects, like what the heck is a short stack motor.
Each motor has a stator that starts as a number of laminations of steel formed together that accept the windings. It is the part that becomes magnetic when current flows through the windings and either repels or pulls the magnet of the rotor around to provide rotating motion. The number of laminations can vary. In the case of a short stack stator, the number of laminations is lower compared to the standard stator, making the overall length of the stator shorter. Thus the name "short stack" has been applied to that stator design .

Continuing, the length of the stator determines the overall length of wire(s) wound around each part known as a slot. Each motor has three slots. The length of wire around each slot has a "resistance" figured in Ohms/foot, or Ohms/1Kfoot. So the lower resistance of wire is now wound around the short stack stator, allowing more current to pass through the windings. This from the famous Ohms Law, E=IR. To calculate passable current, the E is the voltage and it is fixed, so the only variable is the R, resistance. Lower the resistance and you, therefore, increase the current. Why is the current value so important. It is the primary variable in the calculation of power. So, the power of the motor increases as long as you reduce the resistance of the motor.

OK class. There will be a written exam tomorrow and your final grade will be 100% of your results of this exam.
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Old 04-05-2017, 02:18 PM   #13
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The new TSR motor "The One" has a new design that reduced the length of wire while maintaining the ROAR minimum stack length. That reduces its resistance comparable to other motors in the wind class. 13.5, 17.5 and 21.5. The 25.5 ROAR motors are built to a specified minimum resistance number, stack length and rotor spec. With that in play the TSR design could not be applied to that class.
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Old 04-05-2017, 02:44 PM   #14
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Thanks for your input regarding these motors. I will grade your test first tomorrow and then we will be ready for class #2 that will discuss how power is influenced by reduced resistance in the stator.
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Old 04-05-2017, 03:12 PM   #15
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which car are you going to be using for USGT?
Well I have the 6.2 that was the 17.5. So I may just use that but I swear to god if my finger isn't itching to pull the trigger on the 7.1 and building that Friday night. Throwing your set up on it and giving that a go. I have the caddy body pulled for me at Hobby Hanger, the justock hobbywing ESC. So I am just deciding whether to use the 24K Revtech they have at the shop or order the same motor you have, or get what of the other motors mentioned here. I figured I got tonight to figure it out.
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