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Discussion Starter · #1 ·
Could anyone tell me max rpm for super wasp, parma 16d and proslot group 12 motors. Im trying to work out gear ratios to ensure im running the motor at max revs possible. Presuming of course the max power is at top revs? Does a motor power go up in line with revs? Cheers Bungee. ps Love this forum, where do the hours go.
 

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Bungee, I think you're wasting your time with this endeavor. Gear ratio is not something you are going to be able to calculate from max RPM for the motors. The situation is more complex than you are thinking as there are more factors involved, such as track power, car weight, and tire slippage. Another issue is that max RPM varies quite a bit from motor to motor, even among motors of the same type with the same arm timing and with magnets of similar strength.

Most of the really sharp racers and builders, Monty Ohren being one, will tell you that the only effective way to test gear ratio is on the track. That has certainly been my experience over the years, even if I don't have anywhere near the knowledge and experience that Monty has.

One further point: the goal is not to get the motor to run "at max revs possible," but to gear to achieve the lowest lap times.

And even that is not the ultimate goal, which is to make more laps during the heat or race than the competition. I frequently admonish other racers that they should not get too "psyched out" when another racer turns faster laps during practice, as first place is awarded to the racer who makes the most laps, not the racer who turns the fastest lap. I think a lot of slot racers don't fully understand the ramifications of this.

To put it another way, pure speed is not the sole objective in road racing. You need the best combination of speed, handling, and "staying-in-the slot" to be the guy who takes the checkered flag.
 

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Having built up a Parma S16d motor I can tell you that the performance of this motor depends heavily upon it's preparation and tuning. I built one under the supervision of a guy who builds for a lot of people and what you get out of it depends upon what you put into it. Balancing the armature, advancing the timing, upgrading the brushes and ensuring the branch springs are good and correctly shunted all play a big part in the speed and driveability. Ask on Old Weird Herald for help on S16d setup.

Coop
 

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Coop, we're drifting a bit from the original question, but in my experience the most critical parameters in slot car motor building are these:

1. Magnets parallel and 180-degrees from each other, and with an "air gap" co-axial with the armature shaft axis.

2. Brush hoods that are precisely centered on the armature shaft axis and 180-degrees apart.

3. Quality brushes that fit in the hoods with minimal clearance in the horizontal direction. This is especially important in motors that don't use shunt wires.

4. Well-aligned precision bushings or bearings.

5. A combination of armature timing and magnet strength appropriate to the track power and wiring scheme.

6. A well-balanced armature with a straight shaft and a smoothly-finished cylindrical commutator co-axial with the shaft axis.

Futher notes:

1. Some very successful racers do not insist that magnets must be of matched strengths.

2. Brush spring tension must be sufficient to prevent brush bounce but beyond that point spring tension is not a significant performance factor.
 

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Discussion Starter · #5 ·
Thankyou for your info etc but i really would like to know what revs motors go to and where the power is. Untill you understand the power source how can you modify the car properly? When looking at the set up of different cars all doing their best times im noticing a pattern of average revs per lap/minute. With no track at home i can calculate what different set ups will do to laps times given same rpm and see what actually happens to laps times at the races. This way i can build a database of set ups etc. Also 1mm diameter of trye difference as they wear means changing the spur by one tooth to retain the same motoor caricturistiscs. And of course a race is about lap times, it is a string of laps put together. Not much else makes a winner than a car doing more fast laps in a row than the opposition! If you all want to keep testing by feel alone without a bit of science keep going. You'll soon be overtaken by those using a combination of both. Cheers for all your thoughts. Bungee.
 

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Bungee
Agree that both are necessary.
Motors vary so much that your very best bet is to purchase a cheap rpm meter and do your own checks on your own motors so that you know EXACTLY what you, yourself, have. Well worth it you want to know what is really going on.

I don't know of any metering system that checks actual power produced (as opposed to consumed) and would be fascinated to know if anything exists that can produce this information on small motors.
 

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not sure how much people on here know about motors (a lot I'm guessing in soe cases) but I can tell you that the motor has most current going through it at the lowest rpm. as the motor turns it produces a back electric motive force which opposes the force from the power source. it's the some of these that is the effect on how much current goes through your motor
 

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Bungee, my point about lap times was that most racers can rip off a banzai lap but few can sustain that kind of lap time over the course of a heat or a race.

I still believe that your proposed research will not generate much useful info, if all you are considering is motor rpm.

If you desire a clearer understanding of PMDC motors, you might find these links of some interest:

http://www.globe-motors.com/dc_motor.pdf

http://lancet.mit.edu/motors/motors3.html

http://hyperphysics.phy-astr.gsu.edu/hbase...etic/motdc.html

The analysis of the performance characteristics of PMDC motors requires higher level math than I can recall (if I ever knew it) and again I must offer the opinion that on-track testing is the most practical way to go.

But don't let me discourage your experimentation and data collection! :cool:
 

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i did some research on electric motors for a physics prodject. thought you might find it useful

Electric motor
All of the above methods of powering a car use an electric motor so it made sense to explain just how these motors used for these concepts work.
An electric motor uses the electricity to produce opposing magnetic fields. They can be set up in two ways for the use in a car, they can use an electromagnet for the rotor and normal permanent magnets for the stator or they can use electromagnets for the stator as well as for the rotor. Other than this issue of weight and cost it would be feasible to use both electromagnets and permanent magnets for the stators.
The electric current passes through one stator coil making an electromagnet, it then goes through the coils making the rotor magnetic field, and then through the second stator coil making another magnet. The magnet fields produced by these magnets repel each other and as the rotor magnet as its name suggests can rotate, it does this thus turning a spindle, which can be used to drive the car. Brushes are used so that the stator magnets are constantly repelling the rotor magnets so that the rotor turns while there is a supply of electricity.
The amount of current passing through the coils that make the electromagnets is determined by the potential difference across the coils. However this isn't constant at all speeds of the spindle. This is because the action of the rotor rotating creates an electromagnetic force (back EMF) which acts in the opposite direction the to the electromagnetic force of the power supply. It is the net force of these to that determines how much current passes through the motor. As the back EMF is proportional to the speed of the rotor at high speeds when there is very little load on the motor the net potential difference across the circuit is very low so very little current passes through the circuit. This also means that when the motor is going at a slow speed there is little back EMF produced so the net voltage of the circuit is high so a lot of current passes through it. As the strength of the electromagnets is proportional to the amount of current going through them they become very powerful so the motor has a lot of torch. This mean that a car with an electric motor will have most torch when pulling away which is when you need the most power. It has the down side that when the motor doesn't turn the amount of current passing through it can cause the motor to get very hot. For this reason they can be set up with two different voltage been put through the motor. The first is a lower voltage which is use to get the motor up to speed before a load is applied to it at which point a higher voltage is used to run the engine when the car is been driven.
 

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Discussion Starter · #10 ·
Wow! Now were talking. Thanks very much for all the latest replies. I dare say most of my research will be a waste of time but its always best to learn for yourself. Im going to build a rolling road with a mate at my club who is an electronics wizz. Hes currently developing contactless controllers and is making me one with various new knobs on. Were talking about the possibilities of rolling roads to properly understand motors under power. Also looking into data logging of trigger/plunger positions, perhaps linked to the main computer so we could compare laps etc. It all sounds a bit ott im sure but perhaps it may take what you can get out of slot car racing to a new level. Imagine comparing what your motor mods are actually doing to the performance of your car. then looking at your driving printouts to see if you're doing anything different etc. Will keep you posted as to how its all going. Once these controllers are sorted they'll be the only ones to have. Can't wait for mine, launch controll, permanent full voltage to the car, digital capabilities etc oooooooh.
 

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Other than the fact that you may enjoy doing all this,knowing the free load RPM of any motor,is just not usefull in any way.

Apart from the fact,that the power sousrce you are using,will undoubtably be different from any track you run on,there are so many factors involved.And very few of them even to do with the motor.

Track power,track wiring,track surface,track configuration,track temperature,humidity,track conditions(clean,dirty,glued,un glued).

As well as the free load RPM,you need to know the torque characteristics of the particular arm/setup combination.You can take ten seemingly identical Superwasp motors,and have ten different no load max rpm readings(and,I mean huge differences,of several 1,000s of rpm).Now the good news,do this on another source of power,and everything will change again.

The one thing I can guarantee you,is that the max RPM reading will have ABSOLUTELY NO CORRELATION WITH ON TRACK PERFORMANCE AT ALL.

As I said,there are too many variables in the motor,and in the track,and chassis.

While you are spending untold hours charting moto performance/RPM,most other people with 10-20 minutes worth of track time will be blowin past you on the straights and out of the corners too.

By all means,enjoy what you are doing,but,I would rather spend the time actually playin with my cars.

For the Super Wasp,just go with the smallest pinion you can put on it.That will usually get you close,and go from there.
 

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Hi

I have the feeling that the impulse behind this thread is that so many cheap motors come with "RPM" listed on the label. This reading has no reflection in reality. These are cheap buck motors(or one euro if you insist), no one tests them in any meaningful way.

As for the concept...Motors like the S16d can vary just in the wind by 3% PER POLE. If you want a given motor to have more RPM...shorten the stack, lighten the springs, KILL THE MAGNETS. All this will raise RPM but ruin HP and efficency.

An example: the vintage FT13uo motor called the Monogram X88 was a two ohm wind, but with magnets in the 150 gauss range. This means that the no load amp draw is about twice the Modern FT 130 SCX motor with a 2 hom wind which has magnets in the 350 gauss range. The HP is larger, the same car with either motor will be faster with the new SLOWER ca 22,000 rpm of the SCX. For one thing, on short tracks it will accelerate better and run cooler. On long tracks will pull a far longer gear for more top speed and STILL have better acceleration and run cooler.

Want a number? A Wasp can turn ca 45,000 rpm, a gp 12 perhaps 55-60k. Nothing to do with trackside performance.

In the old days, my 25s pro motors would pull some 125k no load until I got cobalts, then it was nearer 70k.

Fate
 

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QUOTE Hey, Al, isn't your post basically the same thing I told Bungee?

Eggsacly so.Repetition is one of the keys to learning.
 

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Discussion Starter · #15 ·
A few things to clear up i think. Ive never seen rpm quoted for any motor, thats why im asking on here. im not interested in using the car at max rpm, that is only going to be on long straights, obviously. i did ask where in the rpm range the power is. Knowing where the most power is compared to my calculations will confirm or confuse my research. It seems there is some sort of pattern to gear set ups with the different motors i have. I havent got a track at home so dont have lots of 10 mins to test. And nobody is blowing me away. With standard cars and limited experience, no blueprinting etc im regularily beating twice the price cars built by mega experienced people. Once i can get my cars matched perfectly to my driving skills and working at their most efficient, by feel and by science ill be happy, but not until then. As i said most of research is not very efficient, often barking up the wrong tree but unless you look for that something else youll just be following the crowd. Loving all the replies cheers bungee.
 

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Discussion Starter · #16 ·
Why keep talking about freeload rpm anyway? Did i not say two of us are designing a rolling road to test motors under load, in the car! Has anyone ever done this? And thanks to all who have just helped with technical info and not bothered to waste their time trying to convince me of what i need to be doing or not. Im starting to get a good idea of how a motor works so i can better understand our testing results etc. Im over 18 and ill decide what to waste my time on, dont waste yours with opinions, experienced they may be but experience can stand still you know, and be improved upon. cheers bungee.
 

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QUOTE Why keep talking about freeload rpm anyway

Your original question was.

QUOTE Could anyone tell me max rpm for super wasp, parma 16d and proslot group 12 motors

Max RPM is allways asumed to be Freeload,unless you stipulate the conditions you want to measure it under,which you did not.
 

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And most of us have had rolling dynos for, oh, decades!

And you have never seen a rating? OK. Sorry I offended you.

Every NC1 is tagged at 14,000 RPM, the identical Evo 1 is rated at 12.500

Scalex stock motors are rated at 17,000 rpm, the idential Scale auto/MRRC is rated at 15k, The Fly, and evo 2 are similarly rated.

And so on.

How does this work on the dyno? It doesn't. I cannot test cars of different weight to get a meaningful number, or different gearing. And the numbrs I do get change from day to day. For decades.
Why do I still use it?

In stock box classes with stock motors, I dont hve to go to the track to discover that my sealed stock motor has started to go away. THAT CAR, THAT SPECIFIC CONFIGURATION, when it drops a few points, I know from experience how that will affect Tthat cars particular capability. Pitch the motor and use new. If the new motor does not perform to a certain value, I break it in. If it still does not, I then try a new motor.
But this NEVER has anything useful.

Your time is yours. Have fun. However, I think it inappropriate to ask the experienced guys a question and then get pissy that they dont give you the answer you insist on.

Fate
 

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Discussion Starter · #19 ·
"Im trying to work out gear ratios to ensure im running the motor at max revs possible. Presuming of course the max power is at top revs? Does a motor power go up in line with revs?"
These were my origional questions. And they have been answered simply by some. Max power isnt at top revs, ive been told rpms for different motors, and the last post has given real experience of dyno use etc. This is all i was after, fact and info based on science, not personal preference for testing. Some still missed the point i havent a track at home nor an endless suplly of moyors. i only want to test the ones i have against themselves wth different set uos etc. Im still going to build a dyno as perhaps after "decades" of use a new one could create better consistency with the load applied to the car when testing, rev counters,power in and out etc etc etc cheers bungee
 

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Bungee,

threads in a forum rarely are so narrowly focussed to address specifically and only the original question. This is a good thing in three ways -

1) the original question may be too narrow and missed some options and possibilities in its scope; the asker may be rewarded with ideas they had not considered

2) other people on the forum will get a wealth of knowledge on the general theme of the original post, making it a useful thread for everyone, not just a selfish enquiry of someone getting free advice.

3) it means the forum does not get clogged up with loads of similar ALMOST identical threads asking lots of similar but ever so slightly different questions.

Admittedly sometimes threads go wildly off course, but not here so far (until this 'meta' post lol). People are putting time and effort in here, to discuss the issues your post have raised in order to help everyone on the forum, its not all about you.

cheers

Dave
 
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