[kentasokapellos]

Hey guys,
I am an I.B. student and as part of an Extended Essay I have to write, I intend to test how the angular velocity of a simple 1:32 slot car motor (i.e. turns per second ) depends on the current intesity and the number of turns the coils inside the motor have. Should you wish to, I would be happy to post the results here on slotforum.

I was unable to find a tool to to turn the coils in the motor. Does anyone know where I could buy one or if I could order the motors with the coil turns I require? I could do it by hand but the probability of a an error is huge and it would be too time consuming.
Any suggestions on how to go through with it are welcomed.....
Thank you.

 

[Abarth Mike]

Many, many years ago there used to be a book on motor tuning. Maybe someone has a copy they can copy for you?

 

[tifosi]

QUOTE angular velocity of a simple 1:32 slot car motor (i.e. turns per second )

Coo er! I have never heard of 'Revolutions per minute', or 'Revs', expressed that way before!

Perhaps you could persuade some of the 'old hands' here to rewind you a set of armatures for analysis.

Certainly rewind tools did exist, although very simple they certainly helped.
I have not rewound a motor since late 1969 but I found that rewinding by hand and then balancing the arm(ature) resulted in a fast and smooth motor.

Not sure I have the eyesight to do a good job these days!

Good luck with your project. Keep us in touch with the results.

 

[stoner]

i,ve got some info on wire gauge, number of turns, and the rpm these different winds will go to. ive also got some info on same motors, different turns, wire gauge, and rpm achieved at 12v. i suspect this is what your after. if its any use i,ll pm them to you. john

 

[justDave]

I don't know if any tools are currently made for slot car armature winding, but they certainly used to be. Here's an example currently available on eBay. Whether it would give you any better results than winding by hand, I don't know. You'll find extensive discussions about motor winding in the Motors and Motor Building forum of SlotBlog, the US retro slot forum.

David

 

[RichD]

High performance 1/24th and HO armatures are all hand wound. I have seen machine wound S16D armatures that are very sloppy. In a perfect world an armature will be mechanically, electrically and magnetically balanced. If you spin your test motor with another motor you can connect the output to an oscilloscope and compare the shape and amplitude of the peaks. Of course you would want to measure the RPMs and torque of the motor with different applied voltages..

 

[kentasokapellos]

Guys Before you answer note that:
Research Question : How the Revolutions per Second depend on the Current intensity ( I ) i.e. Amperes and the number of turns of the coils. Anything else is out of the question. Should "anything else" affect the results, it will be discussed in the conclusion-evaluation part but NOT in the measurements and Data proccessing
Independent Variables : The only variables I will change, ceteris paribus of course, are "I" and number of turns( Ideally --> 10 different number of turns and for each 10 different current intensities )
Dependent Variable : Revolutions Per Second because I am working in S.I. units.
Controlled : These Variables will remain Constant thourgh the course of the experiments( Voltage, type of motor used, magnets )
Everything is within experimental error
-Thank You

 

[Abarth Mike]

QUOTE (kentasokapellos @ 2 Jul 2012, 22:22) <{POST_SNAPBACK}>How the Revolutions per Second depend on the Current intensity ( I ) i.e. Amperes and the number of turns of the coils. Anything else is out of the question. Should "anything else" affect the results, it will be discussed in the conclusion-evaluation part but NOT in the measurements and Data processing

So if I understand this correctly not only will you have to use the same magnets, you will have to use the same armature for all your test as timing effects RPM . Not sure what percentage the difference is so maybe it will not matter that much.

I was thinking buy a whole bunch of armatures and wind them all in one shot then do the testing but I don't think that will work as the factory timing may be different because of manufacturing tolerances.

That being said this is an academic experiment so real results may not be as important as the process and the conclusion.

 

[300SLR]

As long as the armatures are all the same type, it should be OK to use a batch of arms with different winds rather than keep stripping and rewinding the same one. It would be straightforward enough to swap arms in the same can and endbell, that way variations in magnets, brush gear timing and alignment will be minimised. The production variations between the arms will probably introduce a small experimental errors - here are some ways of reducing that sort of error.

It's worth checking the commutator timing is the same on all of them. This is easy enough to see once the arm is out of the can. It would be a wise precaution to check this each time even if you were rewinding the same arm - coms are a bit prone to slipping on the shaft with some motors.

It's worth checking the spacing of the stack, comm and spacers along the shaft is all the same. Checking by eye may well be good enough. Blueprinting to set them up with the stack centred in the magnetic field and a standard amount of endplay would reduce this variable, but it might not be worth bothering, it will probably only introduce slight errors.

The balance will be different for each arm - but it would change each time the same arm was rewound. Assuming all the testing is done at the sort of speeds normally used in plastic chassis slot cars, balance won't introduce large errors. If somebody with the right skills is available, that variable could be reduced by static balancing the arms. Dynamic balancing would eliminate that variable, but is probably not worth the trouble unless you are going to higher speeds.

The commutator roundness could make some difference. Again, this shouldn't make all that much of a differance with relatively low motor speeds. If the facilities are available, that variable could be eliminated by truing all the comms.

 

[stoner]

just to add another variable. if using 12v as a standard. on a lot of motors torque increases with higher amps thrown at it. john.

 

[300SLR]

Not quite sure how higher amps are thrown at it
The motor will take what current it needs at a given speed and voltage. The current it takes is a maximum at zero revs, falling to a minimum free running at maximum revs. When free running the motor isn't producing any output torque, the torgue it does produce is lost in friction, windage etc.

If insufficient current is available from the supply the voltage falls. In a sense "higher amps are thrown at it" if an adequate power supply replaces an inadequate one, so the voltage doesn't drop. Once an adequate power supply is used, there will be no further gain from using an even higher current supply.

 

[stoner]

thanks 300, you put it in a more understandable way. john

 

[roblees]

Interesting thread. OPs objectives might be better served by starting with a known, professionally wound armature and unwinding the relevant number of turns. arms are normally lightly epoxied or varnished but unwndng is doable (and done by racers seeking an unfair advantage!).

That way OP only has to master resoldering the comm tags, not the whole craft of arm winding.

So I would research standard winds (ie a wire guage and a number of turns) for Group 12, Group 15 and Group 20, say, get a C Can and a bunch of arms and start playing unwinding and measuring.

Another different option is to get a bunch of arms with known winds and just test them!

This is the definition of an acadeic exercise - in real life controlling the variables in motor performance requires a deep understanding of all of them and quite a lot of skill in optimising them, which is one reason aces are faster!

Good luck.

 

[GT6]

hi

I replied to your dad's post on this topic in the other forum, but in case you check here more frequently than he checks there, I'll repost:
The commonly available Mabuchi motors use last 4 or 5 characters of their designation code to specify the wire diameter and number of windings; i.e. an FC-130-11270 motor would use .11 mm diameter wire with 270 windings on each pole. Mabuchi gives a fairly detailed explanation of the complete designation code on their website at:
http://www.mabuchi-motor.co.jp/en_US/technic/t_0302.html

The motor designation code also specifies factors that others have mentioned that effect power output, such as type of magnet, contact brush type, etc. This should allow you to search for and select a motor with the appropriate specifications, availability and price as a starting point to work from.

Good luck with the project.

Scott