It was told to me before but have lost my notes. It had Pi in there somewhere, I think.

Techman

I would like the find information on how to build a magnet zapper. Or an online source on where to buy an inexpensive one.
I'm also interested in a com lathe.

John,

Be prepared to pay! All of the comm lathes mentioned can be used effectively, but you also need the diamond tipped cutter, another $85 or so. As for zappers, Trik Trax and Best o' the West make them, both cost $500 or more, and both are limited to cera mic magnets only. The comm lathe costs less and will certainly do more for your performance... Good luck and good racing.

Techman

Don't worry, it's coming! The next article will be on wing car chassis, but the following one will likely feature low end motors. Meanwhile, the short version is incorporated in the current article on Nastruck building.

Techman

Techman

I am new at this game and would like to know how to tell about what the timing on a motor is and how to change it. If anyone can help I would appreciate it. The motor I am talking about is the 16d type.

Timing refers to the angular relationship between the commutator and the wire coils it connects to. The article by Rudy Garriga of Slick 7 elsewhere on SlotSide has some nice pictures that make it easier to see. In a 16d type motor, in the interest of pro viding reliability, the mass importers of these motors (Parma and Trinity) have chosen to use mild timing of less than 20 degrees. By physically twisting the commutator in the same direction to somewhat higher timing (and I wish there was just one number of degrees that worked best, but there isn't and you MUST experiment), being careful not to break or even stretch the wires, your motor will rev higher and draw more power. There are several important results. First, the motor will wear out faster. But, i f you gear to allow for the higher revs, your car will go faster. Finally, you MUST glue the comm in its new position or it will slip back on its own! Many racers don't try to do this on their own, and just buy an armature or motor prepared by any of many aftermarket rebuilders. We've discussed the pros and cons here before, so lets leave the arguments back down the page. Bottom line is that you will do what you can afford to do, know how to do, or simply wish to do, at your sole option - but if you d on't, you will be passed on the straight! Good luck, and good racing.

Techman

Techman thanks for the info, most enlightening. I thought comms today were locked in position and could not be twisted to advance the timing? To put you more in the picture, we race two class's with 16-D's and S 16-D's. These motors must remain standar d, no timed brush's or shunts, brush hoods must be parallel to the motors flat side, stock arm length, diam and winds, but can have a max timing of 20 degrees for which we use the Parma diamond trued arms, they seem to be pretty good. Magnets, which I was originally seeking advice on can be what ever, providing they look like the standard type, as they can not be tested it is difficult to police. I do not intend on cheating but wish to push the rules to the limit to extract as much power as possible. As we can only run 20 degrees is there any advantage in using stronger magnets ? You may have some other tips. No matter what I do with the 16-D some guys can get their motors to go just that little bit faster a couple of feet a lap, which is impossible to c atch. The S 16-D's some of these really fly much faster than mine. I have also tried the Paul C's and the Fast Ones but all are too slow. Makes you wonder what some people are doing.

Looking forward to your reply.

The 16d's manufactured in China are easily timed by twisting the comm, which is exactly how Fast Ones and many others are doing it. You do have to remember to glue the comm into its new position. Even at 20 degrees the advice remains the same, to avoid stretching the wire! There are many other factors. You say that you are being pulled by just a few feet. Chances are this isn't your motor! Besides the fairly obvious factor of gear ratio, check out the following:

1)Drag - Different bodies can and do perform differently, both for downforce and drag. Check your rules carefully, and then cut the REAR of the body out as much as you can. This both reduces drag and lowers the pressure under the body, thus improving d ownforce.

2) Rolling resistance. Tires act differently IN THE STRAIGHT, as well as the more obvious corners. Using the timer as your guide, test a variety for best average lap times. This assumes, of course, that you can drive the car fairly well to begin with.< /P>

3) Mesh. Sound is your perception of vibrational energy transmitted through air. Speakers are rated in watts because it takes energy to produce sound. If your car is noisy, you're wasting power. A smooth car will also handle better.

4) Alignment. The axle must spin freely, but too much sideplay will bind the gears in left hand corners.

5) Contact. You first have to pickup the power! Fresh braid, in a guide that is level or SLIGHTLY raked upwards, will allow best contact. On cars where the fronts may touch, like most 4 1/2", are also very sensitive to guide pressure. Experiment with w ashers. If the track has variences in braid depth, tune to the low and high spots depending on where they are, and see if you can work with the trackowner to reduce them altogether.

6) Weight. Most hotshots I know now carry digital scales sensitive to 1/10 gram. The total weight of your car, as well as each of the components, will affect speed and handling. This subject is almost a book in itself! Returning to the motors, I honest ly don't know of any better magnets that would look anything like the 16d's you are allowed to use, but do get them zapped, regularly! Also, consistant with your rules, play with spring tension. If your motor fades away as a heat progresses, the problem i s usually springs. The great Brooklyn Dodger baseball executive who invented the minor league system, Branch Rickey, used to say that "luck is the residue of design". Good words to live (and race) by. Faster racers usually don't cheat, but they do take ca re of the details! Good luck (designs) and good racing.

Techman

Techman, how do I know when I've stretched the wire (too far)? Also, how much advancement in timing is possible on a 16D arm?

Justin,

Its hard to tell without a meter to measure armature resistance, and taking before and after readings. Suffice it to say, if the resistance increases, the current loss will offset any gains you get with the timing. As I told Gil further down the page, look for arms with more slack in the wires around the comm tabs. You can sometimes get a bit more slack by pressing the comm furthur onto the shaft, and by folding the tabs in against the phenolic body of the comm as far as you can. All of this is at risk of damaging the arm, but then so is bumping the timing to begin with! I have seen stock 16d arms at as much as 38 degrees and super 16d as high as 45. It is not just possible, but likely that such extreme timing will be detrimental to performance, so be careful. Good luck, and good racing.

Techman

I have a Trinity Midnite that's been running hotter and a little slower than normal lately. (Arm is shimmed correctly, still using stock springs, put in new endbell that was a bit tight in the can, temp was OK when motor was new). Gear ing 9:31 (3.44) on 134ft. LTD. Could I need new springs? Re-zapped magnets? Rebuild in general? Does it do a 16D any good to true the comm during a rebuild? Thanks for the information.

Sounds like the brushes and/or springs are in need of replacement. Do a total rebuild include Mura Bigfoot 2 brushes, and Koford 313 or Champion meduim springs, cutting the comm. Re-zap the mags.

The motor should be better than new.

Justin,

I concur with Mike. To take it a step further, I recommend a rebuild whenever performance drops off at all. Always cut the comm. You don't automatically need new brushes, though. If they are long enough, just reradiusing them is fine, provided you then break the motor in thoroughly. One not so well known fact is that even good brushes, like the Bigfoot II, can vary quite a bit. Bad brushes do occur, so if your motor ran well when fresh reuse the brushes if they are not too short. On the other hand, if you use new brushes in a fresh rebuild and it doesn't run ok, thats one of the first things to suspect. If a zapper is handy, do that every time too. I would never use the stock springs unless I had to by the rules. Good luck, and good racing.

Techman

Techman, you replied to my question on whether there was any advantage in putting S 16-D magnets in a 16-D and you replied that the Deathstar had just that. Well my question is, because S 16-D magnets are thinner and have a larger radi us on the armature side and when put in a 16-D can and because the 16-D armature is smaller in diameter the air gap would be very large reducing the effect of strong magnets. Is there not an optimum air gap one should run in 16-D's and S 16-d's. Is there not a high strength magnet available that can be put into the 16-D. Look forward to your comments

Gil,

In theory, you are correct in that the large air gap will reduce the field. However, the super 16d magnet is so much stronger than the stock 16d magnet that a better field is developed anyway. The major advantage of the super 16d magnets otherwise is t hat they DO, more or less, fit the D can. The stock 16d armature specs of 70 turns/30 guage on a .600 long stack are so torque oriented that I feel a better field would be wasted, for lack of adequate gear ratio availability, and lack of inertia based low end performance. By that I mean that a slower rotating motor, even if geared to produce similar wheel RPM, will carry less kinetic energy for low to mid range acceleration. Put another way, if the motor is spinning faster, it is easier to increase its sp eed by any given increment. Since DC motors have only two speed limiting factors (the torque load and the counter EMF) it makes sense to reduce the load by designing for more RPM. To get past the back EMF, we both raise the timing and avoid a field so str ong that it limits RPM. If the purpose of our motor was to drive a model tank uphill, or move a scale escalator, the opposite arguement would apply. For what its worth, I have experimented with shimming super16 magnets, with no positive effects. Shimming DOES help with the stock magnets, but of course thats usually illegal:-). Here's the most valuable tech tip I know of for 16d advanced motor building:
Select armatures based on the amount of slack in the windings where they connect to the commutator. The more timing you can get WITHOUT OVERSTRETCHING THE WIRE, the better. Play with that a while, and let us know if you find some extra speed. Good lu ck, and good racing.

Techman

Situation: wired my scalex 32 with a 12v/10a battery charger, for brakes,(red, white, black) just like the big boys. works fine with Russkit or Parma resister controllers. hook up my Slotworks and as soon as I touch the black, the car' s at full throttle immediately. no trigger at all. ideas/suggestions? Worked fine the other night at the raceway. worked fine on a friends 'Quickstart 32' using wall warts. Tracks use batteries. Maybe the charger? AC leakage? Help! Techman?

Thanks,

Mike

Mike,

You didn't say, but I suspect your Trinity controller is the electronic model with the transistor circuitry. These, as well as a few excellent high end controllers like the Ruddock DR40, are sensitive to polarity and require that the "gate polarity" of the track match the controller. The controller is available in both positive and negative gate versions, but in your home track situation it will be easier to change the wiring. In a positive gate setup, the power variation is performed between the posit ive power supply and the common (power side braid) connection. The majority of commercial tracks are wired this way. In a negative gate situation, the power regulation is in the negative feed from the power supply, and the brake connects to the positive. Figure out which one you have, and change it. Your resistor based controller will be unaffected. Good luck, and good racing.

Techman

I was informed that a person should square up there endbell when blueprinting there own motors. Can anyone give me proper details on this procedure. Any and all help is greatly appreciated.....Thanx

Step 1) Obtain an alignment bar. Parma, Slick 7, Koford all list them. You want one with the hole for centering on the motor shaft. To this end, also obtain a 2mm (5/64") shaft. This can be a blank shaft, a magnahone, or a Turtle rotor. The only thing tha t won't work is an armature, as the comm gets in the way. If you can find and afford the magnehone hood hone, it is most helpful. Take our motor setup, less armature, and insert the alignment bar into the hoods. If this takes excessive force, you may heve to tweak the hoods, loosen the hodd retaining screws, or use the hood hone to remove small amounts of material from the inside of the hoods, or a combination of all three. Next, run the shaft through the hole in the alignment bar and also the endbell bus hing. Slip the assembly into the can, with the shaft going through the can bushing as well. If this doesn't come easy, you definitely need to loosen the screws. Screw the can in place. Wiggle the bar around some to set the hoods in line with each other. U nless you are looking to affect timing with the setup, the bar should set parrallel to your workbench surface. Tighten up the hood retaining screws. The shaft should slide and rotate freely at this point, or you need to tweak things until it does. This ca lls for care and patience, so take your time and get it right. When it is right, you should be able to easily slip the shaft out the bushings, the bar out of the hoods, and back together again without removing the can. At this point your brushes are cente red on the armature, with no timing effect, and they should also slip easily in and out of the hoods, but with minimal side slop. The endbell is now 'square'. To keep it that way, depending on type of motor, the hoods should be glued to the endbell itself , and/or soldered to their underplate. After this motor isw assembled and run, take it

apart and note whether the brushes wore evenly with the radius centered in their width. If the radius is off center, you either didn't have the hoods straight, or they were very loose around the brushes. Practice this procedure. Once you master this an d airgap setting, you will be as good as anyone at 'blueprinting'! Good luck, and good racing.

Techman