No prep Motor/ESC discussion

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Iowa crawler

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Thought I would create a thread about the latest motor/ ESC for no prep.
This is for 2022 season as no prep is changing everyday. I found the product recommendations are always dated. But the fundamentals are always the same.

So let’s jump into the questions I have first.

Budget builds are always asked about and no budget builds are fun to see. So let’s mix it up.


What KV on 2 s is better. I was looking at the 7700kv from castle or the 5700kv paired with a Mamba X

Or the Hobbywing XR10 pro seems to be a good system paired with a 5.5 turn motor.

What about Trinity? And Tekin. Anyone use
them?

I see Reedy makes a 3300kv motor/ESC combo for $80.00. That seems like a great deal.


What size wire is recommended?
What type of plug is recommended ?

What don’t I know that is important to consider?

Personally for a drag car I want all the power. Then dial it back for the track conditions.
 
Thought I would create a thread about the latest motor/ ESC for no prep.
This is for 2022 season as no prep is changing everyday. I found the product recommendations are always dated. But the fundamentals are always the same.

So let’s jump into the questions I have first.

Budget builds are always asked about and no budget builds are fun to see. So let’s mix it up.
First let me start by saying, Everything I'm about to say is based on what I have picked up from the internet or local guys who run no prep. I have not run no prep myself yet but after the first of the year I'm going to start a no prep build to compete locally. I've spent the better part of a year learning what i can about the topic and watching things evolve so when I go to build a no prep kit Id have a shot at taking everyone's money! >:)

Its hard to talk about budget builds because just like with anything competitive, you have to buy top shelf to be competitive.
What KV on 2 s is better. I was looking at the 7700kv from castle or the 5700kv paired with a Mamba X.
Or the Hobbywing XR10 pro seems to be a good system paired with a 5.5 turn motor.
Personally I would not be looking at any 4pole motors. Id be looking at 2 pole motors. 4 pole motors have more torque but 2 pole can run higher RPMs. Sure the 2 poles will pull more current than the 4 poles but I'm fine with that trade off in this particular RC category. Plus most people I see building competition kits are all using 2 pole motors.
What about Trinity? And Tekin. Anyone use
them?
I just bought the Trinity Holeshot 2.5T Drag Master motor for my no prep build. My original thought was to pair it with the Maclan DRK160 Drag Race King ESC because of its 3-Stage Launch Power Control Software but alas that ESC is limited to 3.5T motors and higher so for now I plan on using a Tekin RX8 ESC since I have two extras just sitting in a drawer anyway. The Tekin RX8 is good down to 2.5T motors.


Probably what I will do at some point is buy the DRK160 and run a 3.5T Tekin eliminator motor with it and compare it to the Trinity 2.5T & RX8 set up to see which one turns the fastest times.
I see Reedy makes a 3300kv motor/ESC combo for $80.00. That seems like a great deal.
3300kv is not going to be remotely competitive but if you're not trying to be then Reedy makes good electronics.
What size wire is recommended?
big as you can possibly get. The bigger the wire the less resistance, The less resistance the lower the voltage drop, the lower the voltage drop the faster your kit goes.
What type of plug is recommended ?
See wire recommendation above.
What don’t I know that is important to consider?
The only thing I can think of here is that you are going to want the very best lipos you can get for the same reasons as using big wire and connectors. Also you want to make sure that whatever ESC you use, if its not the DRK160 with its specific drag race programming options then you want to get an ESC that is fully programmable like an RX8 or a Castle MMX. Not only are you gonna want to create custom throttle and brake curves but ideally you're gonna want data logging capabilities too. Oh and also you most definitely will want a sensored set up. Sensorless just wont cut the mustard here.
Personally for a drag car I want all the power. Then dial it back for the track conditions.
Me too brutha!
 
This is great information to document for future readers.

Before we go any further I found this link.

Kv numbers , motor turn numbers and number of poles is super confusing. And everyone uses different ratings and numbers.

So hopefully this helps with the explanation.
I pulled this out of the comments related to this article.

Very important words are missing here.

For example '13.5T means 3300 RPM' by itself means nothing.
The correct version is:
13.5T means 3300 RPM PER VOLT. Each volt will give you 3300 rpm. So for example ten volts will give you 33,000 rpm.


https://www.minipro.com/blogs/articles/motor-turns-kv-rating
 
@Be Ready here seems to be really knowledgeable in the no-prep game, and he gave some good pointers in my thread on Breydon's DR10 unboxing. He said to look at turns listed motors like 2.5T and up. As Grey mentioned, the Kv rated motors are typically 4 pole, and for drag racing, 2 pole seems to be where it's at.

I will eventually go with the Maclan DRK for ours, but for the initial setup I am just slapping a 3800Kv in our Slash along with a Sidewinder 3, just to get it running. I am not looking to go all out competitive with ours, so nothing too crazy planned so far.
 
This is great information to document for future readers.

Before we go any further I found this link.

Kv numbers , motor turn numbers and number of poles is super confusing. And everyone uses different ratings and numbers.

So hopefully this helps with the explanation.
I pulled this out of the comments related to this article.

Very important words are missing here.

For example '13.5T means 3300 RPM' by itself means nothing.
The correct version is:
13.5T means 3300 RPM PER VOLT. Each volt will give you 3300 rpm. So for example ten volts will give you 33,000 rpm.


https://www.minipro.com/blogs/articles/motor-turns-kv-rating
That article has some decent basic level info in it but there are some things that could be added to it. For example it fails to mention that there is no direct turns to kV equivalency. Meaning that those charts you see are approximations. Most, if not all, of the turns to kV charts I've found on the internet seem to all be based on a chart that was created by RC Car Action. Ill post their chart below. As far as I can tell, RCCA's chart was based on tests done on 4 different motors (The motors that are highlighted) and the rest were extrapolated from those four results. Someone correct me if I'm wrong about this.

turns to kv.jpg


I have also found this formula for approximating kV to turns that was based directly on this chart. Using this formula, as noted below, the approximations get less accurate as you get closer to the extremes. (either really high or really low turn motors).
Turns to KV formula.JPG


kV rating as you stated (and as most people generally know) is how many RPMs a motor will spin per volt applied to it.

Turns, on the other hand, are how many times the copper wire inside the motor wraps around each armature of the motor. "kV" is kinda like HP in an engine and "Turns" has more to do with how the engine was built. This is why there is no direct correlation between turns and kV and it can only be approximated.
brushless_motor_diagram2.jpg

Then there are winds which are different than turns. Youve probably seen on some motors, like Castle Creations for example, Wye and Delta wind types listed. For example we all know the famous Castle 1515 2200kV and if you look at the can it will say 1515/1Y 2200kV on the can. The 1Y tells us that this motor has a 1 Wye wind. What is a wind? I can't say I fully understand everything there is to know about winds but what I do know is the basics. So in the previous paragraph we talked about how a 12T motor has the copper wire wrapped around each armature 12 times. The wind rating is actually a rating signifying two different things. Lets use 12T/1Y as an example. The 12T tells us that the copper wire is wrapped around each armature 12 times. The 1 in 1Y tells us that there is only 1 stand of copper being wound around each of the armatures 12 times. Wye and Delta just signifies the pattern in which the wire is wrapped and terminated before exiting the can to go to the ESC. So if we had a 12T/4D motor then each armature has 4 pieces of wire wrapped around it 12 times in the delta pattern. The pic below will give you a better idea of the difference between a wye and delta wind.
Delta and Wye Winds.jpg


As for poles this has to do with the number of magnetic "poles" inside the motor. a 2pole motor only has two magnets or "poles", a 4 pole has 4, etc etc. The poles or magnets are what is mounted to the "rotor" which is the piece that is essentially the shaft sticking out of the motor. The armatures that have the copper wire wrapped around them are called stators. The more poles the more torque but it also means less RPMs at least generally speaking. There are sometimes way companies can make up for have more or less turns based on the type of winds used but I'm not even going to go down that rabbit hole.

I already hear you asking "how can we tell how many poles a motor has?". Well the only sure fire 100% way is to take it apart and visually inspect it but the vast majority of the time motors listed in turns are 2 pole and motors listed with kV are 4 (or more) poles. There are exceptions to this but most of the time this is going to be true at least from what I've read. One other possible way to tell a 2 pole motor from a 4 pole motor is to take a magnet and while holding the rotor still and get it close enough to the motor to feel the push and pull of the poles (you want to keep the magnet off of the motor though) and slowly run it around the motor counting how many times you feel the poles change in one revolution.
maxresdefault.jpg


Incidentally if you didnt know this already, brushed motors also have stators and rotors too but the copper wire is wound around the rotor instead of the stator and the magnets are placed on the stator which in the case of a brushed motor the stator is basically the entire inside of the can. This is why brushed motors have to have brushes. Since you can't hook wires up directly to a spinning rotor the brushes take the electricity from the wires and transfer it to the rotor. The brushes are pushed against a section of the rotor called the commutator by springs so that they keep in constant contact with it. This is how the turns of copper wire are powered when they are attached to the rotor.

Model-of-a-brush-DC-motor.png


This pic here shows the wear spots from where the brushes were in contact with the commutator while it was spinning. The separations in the commutator are how the rotor activates each section of windings. That way only the section that is in contact with the brushes is active and thats what allows it to "chase" the magnets around and spin.
brushed commutator.jpg


This is probably waaaaay more in depth than anyone wanted to know but i hope that clears up some of the confusion around turns, winds, kV and poles. :)
 

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🤯
This is awesome information.

I guess the next thing with the power system is capacitors. I know nothing.

I think of them as a sorts shock absorber for the electrical system. But how many how much? How to wire them.
 
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Thinking about the radio set up.

Spectrum Dx5 rugged transmitter and SR315 receiver.
Power comes from a Castle monsterX and a 3.5 turn motor.

This is what I’m thinking about.
If I run the radio off 6 volts rather than 8 volts the ESC. I will have less voltage going to the servo and receiver. If my motor/ESC get a super amp draw the radio will brown out. Is it less likely to do that if it’s only trying to push 6 volts rather than 8?

Also I am using an old airplane servo. Super fast metal gears but 4.8 volts. I put it in as a temporary servo but it’s super quick on 6 volts and I’m not sure I need a lot of power in a dragster.

So hi voltage for the radio or low voltage? That’s my question
I also added a big 6volt capacitor to the receiver.
 
You may find you have very little steering under acceleration anyway. Your build is aiming at 30/70% FR/RR static weight distribution. It will be even less FR/RR under acceleration as static weight transfers from front to back as dynamic weight. Oh, and that dynamic weight transfer FR-to-RR comes back as RR-to-FR plus a little more under decelleration at shut down. That is where servo strength comes in to play, or at least consideration for use of a servo saver.

My Top Fuel electric was getting into servo brown out with attendant erratic steering in the speed traps nearing the end of a run. That is where servo arm zero becomes vital as the servo seeks "null". Think Tamiya offers an adjustable servo horn that allows for that. Wish I'd had one back in the day. Addition of a 'glitch buster' cap on the receiver solved the brown out issue. You already have that in place, so may not be an issue.

Perhaps consider a 4xAA alkaline battery pack (6.0v) dedicated to powering the receiver-esp. if you need weight up front? Added benefit it would offer 'good weight' over dead weight. Good luck. Cheers. 'AC'
 
Thanks
Great info. I have plenty of 6volt airplane batteries. If I need to add weight to hit minimal 4.5 lb I can do that.
 

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