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Discussion Starter · #1 ·
Would it still be competitive to run motors with different rpms if they are close to each other in specs. Like using an NSR 20, NSR 21.9, Predator 22.5, Piranha 21.5 against one another

Thank you,

John
 

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Greg Gaub
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It could be. Differences in actual RPM of mass produced motors means that some of them will be faster or slower than their rated speed. Some of the "slower" motors might actually be faster than some of the "faster" motors. That said, differences also include torque ratings, not just unloaded RPM, so one motor might work better on a technical track, or another better for a fast/flowing track.
 

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Discussion Starter · #3 ·
They all are in the 160 to 175 torque range I believe. Wasn’t sure how much of a difference it might make. Trying to get a level playing field without buying a bunch of new motors 😆
 

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I feel it's doubtful that the difference between the motors will be responsible for which car wins and loses.

Over time and with the benefit of experience the group will likely find their preference which may be track design, surface and tyre choice dependent.

The playing field may always be bumpy but have fun finding out 😊
 

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Rich Dumas
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I have raced in classes where a spec motor was used and those could vary in performance by a fair amount. If you race cars with traction magnets the motors are more important, if you race cars without taction magnets the way the cars are tuned is usually more important. In the second case an overpowered car may actually be slower than one with a less powerful motor. With respect to the motors' RPM, torque and power specifications are only helpful in selecting motors that might work well in a particular car, it is what happens on the track that actually matters. If you have a car that seems to be well dialed in and you are getting beat on the straightaways it is probably time for a more powerful motor. The motor in the car may be at the end of its life and need to be replaced. If you must use a spec motor and you are a fanatic racer you might want to purchase several replacement motors in the hopes that one of them will have well above average performance. If there is no motor constraint you will have to use the motor specifications to select which motor(s) to try next.
 

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I remember reading of a Mabuchi rep flatly stating their motors can vary 15% from spec. That is a lot, whether RPM or torque. Face it, these motors are mass-produced in the millions for toys and small appliances. Whether you get a good motor or a dog is strictly up to chance.

Looking for equivalency across brands is even more fraught. What size and turns of wire, what strength magnets, and the details of construction all influence performance. It is a stretch to expect two brands of motor to be equal, never mind variation within a brand.

The good news is tires and setup are more critical to good performance than any particular motor. The best motor going is wasted on a car with poor traction and bad handling. You need good rear tires, glued and trued, with a straight axle and precision bushings/bearings for starters. No car will perform well without a good rear setup.

Ed Bianchi
 

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ParrotGod
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It is not clear if you want to run on plastic or wood, analog or digital.
Mix and matching motors to try to achieve parity is a futile exercise: if you want to get parity then prepare a bunch a cars and then rotate the drivers so that each driver drives all the cars - often referred to as IROC.

As the others said, even within the same brand and specs motors performance varies.
 

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Take two cars one with an FF motor and the other with a standed can motor, with the FF motor having higher revs:
Which car would be quicker? Long straights wide curves definitely FF motor. Take a car with a comparative slower can motor.
Windy track, tighter curves short straights, which car would be quicker? Can motor definitely.
Why!? Torque!!! Yes the higher revving thinner body FF motor might be faster but the wider body can motor with greater
torque would have far better brakes and therefore much quicker around the bends. :)
 

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ParrotGod
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We’re racing on a 75ft Digital Carrera track
I think the best approach to have some "parity" is to have simulations and longish races (more than 10 mins).
The main idea is that with simulations, the managing of the car and resources (fuel, tyres, damage points) become more important that just the top speed of a car.
Assuming that all cars are tuned in a similar way.
We run 14 min races, with simulations on (using oXigen and RCSO2) and making a mistake during a pit stop costs you the race win.
 
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Discussion Starter · #13 ·
All Carrera, all 17.3 slot it rims on slot it axles, slot it gears, rubber or urethane tires, all geared 3:1
 

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Take two cars one with an FF motor and the other with a standed can motor, with the FF motor having higher revs:
Which car would be quicker? Long straights wide curves definitely FF motor. Take a car with a comparative slower can motor.
Windy track, tighter curves short straights, which car would be quicker? Can motor definitely.
Why!? Torque!!! Yes the higher revving thinner body FF motor might be faster but the wider body can motor with greater
torque would have far better brakes and therefore mu
I think the best approach to have some "parity" is to have simulations and longish races (more than 10 mins).
The main idea is that with simulations, the managing of the car and resources (fuel, tyres, damage points) become more important that just the top speed of a car.
Assuming that all cars are tuned in a similar way.
We run 14 min races, with simulations on (using oXigen and RCSO2) and making a mistake during a pit stop costs you the race win.
ch quicker around the bends. :)
Generally atempted to show why FF motors have comparatively poorer brakes due to lower torque.
 

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Alan Wilkinson
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John, you didn't tell us whether you :
A. Want to balance a set of your own cars for your own track
Or
B. Want to create a formula for club racing to ensure a level playing field.

If A, test the motors with an RPM meter and swap them around between your cars. Track testing will reveal which chassis handle poorly so fit the slower less torquey motors . Fit the faster to the less well handling cars. There is a no formula, just experimentation.

If B. Just spec a standard motor for all to use.
However, I have seen some clubs and organisations allow different motors in the same class with some success.

1. DiSCA permits slot.IT Flatsix and MX16 cars to run against each other (LMP versus GT)
2. London slot car runs a touring car class with mixed motors. MX15 vs flatsix versus Fly Evo inline or sidewinder.
3. Nascot wood slot car run a sport/gt class where the only limit is a 25k rpm spec. Any motor any manufacturer

AlanW
 

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Generally atempted to show why FF motors have comparatively poorer brakes due to lower torque.
Peregrine - I completely agree with your conclusion!
It’s not the physical size of the motor, though, that decides the torque. The torque in a dc motor comes from moving each loop of wire on the armature through the magnetic field from the magnets. More loops/turns and/or stronger magnets give more torque and the faster the motor is turning the more torque you get. Bigger motors give more torque not necessarily because they’re bigger, but because the magnets tend to be stronger.
Mike
 

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I think you'll find maximum torque is at minimum rpm not max rpm.
I’m only a mechanical engineer, so these volt and amp things are a bit of a mystery to me 😸!

I was talking about the braking torque when the motor is being driven as a generator. I have trouble getting my head around how the drive power and torque vary as the car slows down. When the car is stopped, there is no voltage generated by the motor as a generator, so that can’t be the maximum torque.
Mike
 

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Discussion Starter · #20 ·
John, you didn't tell us whether you :
A. Want to balance a set of your own cars for your own track
Or
B. Want to create a formula for club racing to ensure a level playing field.

If A, test the motors with an RPM meter and swap them around between your cars. Track testing will reveal which chassis handle poorly so fit the slower less torquey motors . Fit the faster to the less well handling cars. There is a no formula, just experimentation.

If B. Just spec a standard motor for all to use.
However, I have seen some clubs and organisations allow different motors in the same class with some success.

1. DiSCA permits slot.IT Flatsix and MX16 cars to run against each other (LMP versus GT)
2. London slot car runs a touring car class with mixed motors. MX15 vs flatsix versus Fly Evo inline or sidewinder.
3. Nascot wood slot car run a sport/gt class where the only limit is a 25k rpm spec. Any motor any manufacturer

AlanW

Thank you, yes this is for my home track, trying to get a small club together. We race GT3 right now. Also, all the cars have no rear magnet, just the middle magnet right now
 
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