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Most Powerful 21.5T, 17.5T, and 13.5T Motors?

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Most Powerful 21.5T, 17.5T, and 13.5T Motors?

Old 06-14-2019, 10:49 AM
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Technically you aren't cheating if you never race
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Old 06-14-2019, 11:54 AM
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Originally Posted by Racermac73 View Post
Technically you aren't cheating if you never race
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Old 06-14-2019, 05:28 PM
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Originally Posted by Racermac73 View Post
Technically you aren't cheating if you never race
Technically soaking up all the Rctech knowledge is better than cheating...It's summer now and nitro racing time....
The 40g rotor(shaft material change is legal) might be the next revolution, and all prototypes get secretly tested in regular club races: not considered cheating at all.....
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Old 06-14-2019, 05:39 PM
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Originally Posted by bertrandsv87 View Post
Technically soaking up all the Rctech knowledge is better than cheating...It's summer now and nitro racing time....
The 40g rotor(shaft material change is legal) might be the next revolution, and all prototypes get secretly tested in regular club races: not considered cheating at all.....
Check the rules again. Modifying motors by fabricating custom parts for them is not legal. Secretly using unapproved prototypes is definitely cheating.
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Old 06-14-2019, 05:53 PM
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Originally Posted by gigaplex View Post
Check the rules again. Modifying motors by fabricating custom parts for them is not legal. Secretly using unapproved prototypes is definitely cheating.
itís legal at the Bench racing keyboard Nationals
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Old 06-14-2019, 06:02 PM
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Originally Posted by gigaplex View Post
Check the rules again. Modifying motors by fabricating custom parts for them is not legal. Secretly using unapproved prototypes is definitely cheating.
It is the same as changing from steel to aluminum screws, no biggie....It does not matter how they made the aluminum screw, and the steel screw was not modified: same for the rotor shaft, as long as the magnet is the same, you're legal according to the Roar rules...I believe that the shaft has to be a single material with no holes or cavities in it...
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Old 06-14-2019, 06:24 PM
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Originally Posted by bertrandsv87 View Post
It is the same as changing from steel to aluminum screws, no biggie....It does not matter how they made the aluminum screw, and the steel screw was not modified: same for the rotor shaft, as long as the magnet is the same, you're legal according to the Roar rules...I believe that the shaft has to be a single material with no holes or cavities in it...
It is absolutely not the same thing as changing screws. ROAR rules require you to use the specific rotors from the manufacturer, unmodified, with the part identifier stamped on the shaft, that were approved. You can't swap them out with a custom part.
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Old 06-14-2019, 06:31 PM
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8.4.2.4 Modification of approved motors from their approved configuration and materials by manufacturers, importers or competitors is not permitted.
It is explicitly illegal to change the materials of approved components.
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Old 06-14-2019, 07:09 PM
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Its funny, though I typed what I typed I was also thinking what you said to me to myself. I get the point of the thread but a balance of power and setup is typically the key is most races.

Regardless I just got a 13.5T motor to replace a 9.5T motor on my new YZ4. I got an R1 13.5 V16 motor...and the reason I got it is because some dude on YT did a bunch of dyno tests and said it was a bad boy I look fwd to racing in a stock class with my new toy.


Originally Posted by dietDrThunder View Post
Holy thread necromancy! Anyway...since we're here...

I'm pretty sure we are all aware that if you drive better, your lap times are better. Why is it that every single time, ever, when a person asks a motor question, someone has to pipe up with "drive better?" If the guy wanted advice on driving that's what he would have asked ffs.

the lessons being learned are that it isn't always clear-cut which motor is faster, because there are many many variables to account for. It will always be the case that if you drive better, you will go faster. This is true in every class, in every car, with every motor, at every track. This is not a useful answer when someone is looking for help in making the car objectively faster.

Cripes.
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Old 06-14-2019, 08:10 PM
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if its not illegal it will be. the difference is dramatic but too low of an inertia ratio is just as bad as too high of an inertia ratio. anywhere from 1-10 to 1 for continuous accel/deceleration. up to 30 to 1 for a mix and 60 to 1 for power. what you will see is cogging if its too low, traction loss and bad efficiency. if its to high it wil feel soggy and unresponsive. go too far and you get hot or smoke the esc.

at the extremes the motor doesnt feel the drive train (low inertia ratio) or the drivetrain has over damped the rate of change the motor is capable of. (High inertia) drive train with low rotor inertia,

when escís get as powerful as there big brothers feed forward (predictive) temp control or dynamic notch filters control the inefficiencies.

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Old 06-14-2019, 09:56 PM
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Originally Posted by gigaplex View Post
It is explicitly illegal to change the materials of approved components.
I guess the rotors with the new tungsten shafts will have to be sent in for approval...I wonder if some smart racers could fill up the center of their steel shafts with tungsten or gold to gain some inertia...
Bry, I understand your point about the extremes of the inertia world, but an extra 10g to 14g close to the center of rotation of the rotor will not push the inertia to the extremes, but it might be enough to make a visible difference on the track...I am pretty sure that if it ends up being around a 40watt difference, then all the manufacturers will jump in and push Roar to approve the new change in shaft material for Bert's sake...lol....
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Old 06-15-2019, 08:51 PM
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in the other thread I said I suspect a low inertia drive train would be helpful and i described what you would feel if you went too far. i then described what you would feel in the opposite direction. im not trying to disagree or totally agree, If it was on my radar i would do the math. Im simply providing you with descriptions that help you do your on track testing.

rotor inertia is not something that is intuitive. racing is torque and power and most people use a stop watch to figure out what works for them (which is fine). there is an order to what you have to understand if you want to understand inertia matching (beyond testing for improvements). it starts with understand how torque is delivered at every rpm on a curve a matching what can be delivered to what is needed. there are a couple guys on here that are all about the curves but are still thinking about how to balance the curve against what a track needs. once the connection is made a bell will go off and it wont spread like wild fire because you have to really want it to go into no mans land and there are alternatives. That is only the first mental revolution that is down the road. Then you find out that profound understanding of matching torque to track requirements is not as important as inertia matching. if the first and second concept doesnt eliminate all motivation the 3rd and 4th ones will.

Keep testing inertia. you are certainly inspired and there is allot to be gained, if you run into a wall work around it, there is still more to understand about torque that would make workarounds easier if you get stuck that will still be here.
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Old 06-15-2019, 09:04 PM
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Im not telling you that you skipped something that you should go back to and understand first. i tested concepts that were out of order in robotics way back when that motivated me to do more. Some old guy was always telling me im doing it wrong and i proved them wrong. Now im that old guy doing the same except I remember that i didnt listen and as messed up as it was behind it all was something more important. Anybody who invest the time into going against some predominant concept is developing motivation and a will to succeed. Or they dont, but im only going to push the order of things enough to give people who need a motivational challenge room while at the same time not demotivating guys who arent waiting for an old guy to tell them they have no clue. Do your thing. Its reasonable.
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Old 06-15-2019, 09:27 PM
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In terms of inertia isn't the rotor shaft considered on the drivetrain side of the equation? The rotor shaft is something the magnet has to move. I thought one side of the ratio is just the mass of the magnet.

On the inertia matching it isn't rocket science. You want the drivetrain as light as possible, while still being able to have components durable enough to withstand the forces you are putting through them. At that point track layout and grip levels will dictate final gear ratio and timing settings.

Each track is different and there are a multitude of adjustments that you can make to lower your lap times, which is ultimately all that matters. It is way easier to swap a pinion or change timing than to adjust the inertia ratio. Additionally, how you drive the car has a big impact on setup and performance. We have a 1/18 latrax rally spec class and I can take the controller from some guys and knock 2 seconds off their fastest lap with their own car. If I set their car up for my driving style I could get even more time out of the car. Good drivers carry corner speed, which means the less you slow down, the less you have to speed back up. If you get motored on the straight it's because you were slow through the corner before.

If you race at one track, once you are in the sweet spot you don't have to make wholesale changes. If you regularly go to different tracks then wholesale changes are usually necessary.

Bri195 have you set any lap records yet?
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Old 06-16-2019, 09:18 AM
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Originally Posted by waitwhat View Post
In terms of inertia isn't the rotor shaft considered on the drivetrain side of the equation? The rotor shaft is something the magnet has to move. I thought one side of the ratio is just the mass of the magnet.

On the inertia matching it isn't rocket science. You want the drivetrain as light as possible, while still being able to have components durable enough to withstand the forces you are putting through them. At that point track layout and grip levels will dictate final gear ratio and timing settings.

Each track is different and there are a multitude of adjustments that you can make to lower your lap times, which is ultimately all that matters. It is way easier to swap a pinion or change timing than to adjust the inertia ratio. Additionally, how you drive the car has a big impact on setup and performance. We have a 1/18 latrax rally spec class and I can take the controller from some guys and knock 2 seconds off their fastest lap with their own car. If I set their car up for my driving style I could get even more time out of the car. Good drivers carry corner speed, which means the less you slow down, the less you have to speed back up. If you get motored on the straight it's because you were slow through the corner before.

If you race at one track, once you are in the sweet spot you don't have to make wholesale changes. If you regularly go to different tracks then wholesale changes are usually necessary.

Bri195 have you set any lap records yet?
you are thinking in terms of torque not inertia. Inertia is the resistance to a change. Torque creates the change whether itís too much or too little. You are ahead of the game in thinking in terms of torque and mass and so on but inertia matching not minimizing rotating mass to increase effective torque. Increasing effective torque will make you faster. Itís just not inertia matching. Iím sure Bert is wondering why I think his concept should be investigated at this point.

A light weight drive train may give you more effective torque by over powering the drive train. This can work well. But a 1:1 or 10:1 is not .5 to 1. Too little drive train inertia is bad. I explained previously.

hmm, do I sense some competitive conversation on the horizon? As far as records itís probably the ratio of what I know to what I actually use in rc. I practice and understand. The two arenít exclusive but I certainly practice more than experiment. Iíve already done that and I know where priorities are right now.

I got frustrated with my usgt car and tuned the heck out of the motor and drive train. Itís faster than my 17.5 now and in a straight line it canít be beat. But the motor exceeds my skill and setup. Iíll leave the motor the way it is and Iíll focus on the setup and practice. Having too much motor kind of forces you to improve other things. Itís not a bad thing to push yourself as long as your realistic about the big picture.

im not trying to be the smartest guy who ever typed about motors. Iím pretty soft on false information because I want to encourage. Iíll push a little on guys who need adversity to motivate because that is what I needed back in the day but what I didnít know then is that when you get old you get tired of it. I probably missed allot in the way I squeezed old guys for knowledge.

Last edited by Bry195; 06-16-2019 at 08:30 PM.
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