THE 10 MOST IMPORTANT TUNING TIPS #1) The best way to increase the performance of a new stock motor (or any laydown brush motor) is to align the brush hoods (see the Black Book for how to do this properly). #2) Clean the inside of your brush hoods REALLY well. This is how your motor gets it's power. Don't just spray it with motor spray (the Black Book has a great cleaning "How To" section). The brush shunt is only good for a 10A MAX. #3) NEVER replace the brushes in a motor without retruing the commutator first. It's better to leave the old ones in if you don't have a lathe handy at the moment. #4) The biggest reason for a new stock motor being slow is it's geared wrong. Try this. Gear the motor so it just peaks out as you let off the throttle to set up for the turn at the end of the longest straight. This is how you get your most speed. You can then adjust for run-time, infield punch, or motor temp. Don't rely on someone else telling you how to gear. I've seen stock motors of the same brand and type require a 5 tooth gear difference to be geared properly. #5) I shouldn't have to say this but bushings and bearings need oil. I suggest the TRIBO. #6) The biggest reason any motor slows down is poor commutation. This could be an out-of-round comm or bad brushes or both. #7) The best dyno in the world is the track. Don't place too much value in "the numbers". And don't compare dyno's. They usually are never the same. #8) When breaking in the brushes on a modified motor, set the endbell to zero timing first. This is the point that the brushes arc the least. So your comm won't have any heavy black areas to the left of the slot when you're done. Once the brushes are seated, then crank in your race timing. #9) Most racers know that high-silver content brushes make the most power but are hardest on the commutator. Try putting a brush of lesser silver content on the negative side. This brush will deposit more graphite and other lubricants on the comm and make the high-silver brush on the positive side wear better. This is called the polarized brush system. #10) Buy the latest version of Big Jim's R/C Motor Black Book when it becomes available. It is far more up-to-date and contains more tuning tips than the one that's currently on line. We are saving the best for last. I hope to see a published copy the end of January '02. May-June, 2002 INFO ON THE NEW REEDY CO-BALT STOCK MOTOR SCHEDULED RELEASE DATE: Late 2002 I have posted all this info and testing of the prototypes on my forums. If you missed any of it, here it is. IMO, this motor is destined to be the fastest, easiest to tune, coolest running 24 degree stock class racing motor ever produced. Because of this, I will no longer be stocking any EPIC motors either stock or modified. I will be making D4 and P94 replacement armatures for awhile until I run out of blanks. The Reedy CO-balt stock motor, due to be released in July has recorded the highest numbers ever on my CE dyno. The brush hoods will not have to be aligned because there will be no brush shifting. How we accomplished that I can't say at this time. But it is an industry first. It will come from the factory in Japan with the #766 brush and the right spring tension for 6 cell use and of course, those marvelous C4 high-grade magnets that never need remagnetizing. It will have lots more torque than the MVP and require no cut down brushes. And it will run cool. Every problem you or anyone normally has with stock motors will be eliminated with the Reedy CO-balt. This motor is so good, I am not going to stock any Epic motors after it's release and we have some great changes we're making to the Ti after we get done with the CO and the Spec 19T (that motor will be [I]really[/I] trick if the factory can do what we planned). I don't think Mike would mind me sharing this much with my readers here (I hope). Between Mike and myself, we have a combined 48 years of r/c motor experience to rely on. I don't mean to make myself sound equal to him in any way. He is the master. I am just a hired consultant but we are on a mission to bring you the best motors ever made and I am grateful for the opportunity to help do that. NEW MOTOR TEST **Dyno Testing the REEDY CO-balt Stock Motor** This is prototype #2 with all the latest innovations and is the closest one so far to the production motor design. The necessary parts were hand-built except for the armature blank. It came from Japan and is as production will be. The new REEDY CO-balt stock (so named for the can color, not the magnets) will be a dynamite looking Cobalt Blue powder coat with the blue endbell and heatsinks. This is the first time Mike has used something other than the standard Yokomo greenish/black or chrome. I just recalibrated my CE TurboDyno 45 using Glenn's (TMFU) relatively new machine as a standard. I also disassembled the entire cradle and cleaned all the bearings, rpm sensor, torque sensor and installed my custom faceplate by Bruce Triplett of www.rc4less.com with my own picture on it no doubt. While I had the case apart I cleaned the fan and FET heatsink. I also painted the ugly bathroom beige plastic case with Duplicolor Mirage magenta/gold flip-flop lacquer paint and then coated it with clear polyurethane. Definitely the hottest looking TD around and it works perfectly. BTW, I am using P94 hardware on my Ti slave motor with the brushes narrowed to standard width. Although the taller brush would have worked well, the #4380 compound is not the best to use in a slave motor and the #4383 compound would be disastrous. But now to the testing. TEST PARAMETERS Test #1 SETUP: 4 cell oval or 1/12th Voltage input: 5.0V Brushes:Reedy #766 both + -, no cuts or serrations, full face. Springs: Yokomo soft: 5.0 FS units + and 4.75 FS units -. Applied the usual tuning tricks as outlined in the Black book. 17394rpm 3.3TQ 43W 57EF @15.0A Load 15933rpm 4.8TQ 56W 62EF @17.9A Load 14832rpm 5.9TQ 65W 65EF @20.0A Load 14093rpm 6.8TQ 71W 64EF @22.0A Load 12836rpm 8.1TQ 77W 61EF @25.0A Load 11678rpm 9.3TQ 80W 57EF @28.0A Load Difference in rpm from low to high load:5716 Test #2 SETUP: 6 cell TC or Off-road Voltage input: 7.0V Brushes: Same as Test #1 Springs: Reedy Coppers: 6.0 FS units +, 5.5 FS units -. Otherwise, same as Test #1. 25269rpm 3.5TQ 65W 61EF @15.0A Load 22941rpm 5.1TQ 87W 69EF @17.9A Load 21969rpm 6.2TQ 101W 71EF @20.1A Load 21041rpm 7.1TQ 111W 72EF @22.0A Load 19479rpm 8.6TQ 123W 70EF @25.0A Load 17929rpm 9.9TQ 132W 67EF @28.0A Load Difference in rpm from low to high load: 7340 TEST CONCLUSION: The 4 cell test is by far, the best numbers I have ever recorded, even when my dyno was reading high. The 6 cell test recorded the highest 25A and 28A numbers ever on my TD, even when it was out-of-calibration. The rest of the numbers are excellent also with a good balance of rpm and torque which makes the motor easy to gear for any class of racing. The rpm difference between the low load and the highest load in each test is smaller than any stock tested so far. This indicates a powerful motor with a broad powerband. As a rule with the MVP's, a 97W @20A MVP is equal in speed and power on the track to a 100W Epic at the same load. I don't for sure know why except it could be those marvelous C4 magnets. If this is the case then the CO will be a serious contender for the most powerful 24D stock motor ever to make production. Also, with perfect brush hood alignment, it took 3 cycles of 300 secs at 3VDC and 2 more cycles at 400 secs to break-in the brushes full. The comm looks polished with very little black carbon on the trailing side of the slot. I take this as an indication that the motor is extremely low in back EMF and eddy current buildups. It also ran very cool, unlike an MVP. With 3 dyno runs back-to-back, the numbers varied at most, 2W in any load category. I'm sending this prototype out to one of my testers in IL, Brent Bones. I have prototype #3 almost ready to track test here at SoCal by my other good tester, Louis Rainer. I'll report more when the testing is done. Then it's to the new 19t Spec. Just before I sent the CO out to my tester, I cleaned the brush faces with the Paradigm comm stick www.team-paradigm.com and the comm through the hoods with the square part of it and TRIBO'd the bushings (none on the comm during any phase of dyno testing however). These are the numbers that came back this time. 24157rpm 3.8TQ 69W 65EF @15.0A 22755rpm 5.2TQ 88W 70EF @17.9A 21969rpm 6.2TQ 101W 71EF @20.0A 21021rpm 7.1TQ 111W 71EF @22.0A 19616rpm 8.5TQ 124W 70EF @25.0A 18267rpm 9.8TQ 133W 68EF @28.0A The difference in rpm from the low load to the high load is only 5879! So substantiates the value of a clean comm and brushes, even if it looks OK. And look at the EF even at a 25A load. IMO, it has the perfect powercurve, that is in the 18A to 25A range. When you see the armature, you'll understand why the CO has so much load handling capabilities without sacrificing rpm. Very trick indeed. I'm sure looking forward to dethroning the Epics as "king of the Hill" as far as stock motors. The 19t Spec and the Ti are next. TRACK TESTING THE CO I set the prototypes #2 and #3 up as close to the way they would come from Japan and gave them to TWO OF my testers. No special tuning. #766 brushes on both sides, about 6 to 6.5 FS unit on spring tension which is the standard MVP spring. From Brent Bones in Illinois "In off-road truck it was awesome, better than a P2K or P2K2. Saturday I went and ran Carpet Oval 6-cell with the Proto #2. The motor was again very strong and fast. My runs were very much right on the track record. This motor seems to be very universal for multiple applications." Louis Rainer- So. California "Very, very, good. It was somewhere between my strong P2K2 and a 19 turn motor. It qualified me second for the A-Main when I probably would have qualified mid-field to back in the A-Main. First race I had it geared 88-38 in my TC3...very fast. I was actually pushing people out of my way on the straight. If this is what a motor from the factory is going to be like, then you have a real winner. A tuned version (brushes and springs) will be awesome." The overwhelming thing every tester said was the bottom end was so strong. Everything is going along well. I'm doing the final report in a few days. April 14, 2002 Sharpening Carbide Bits for Truing Comms DIAMOND BITS VERSES CARBIDE FOR YOUR PIT LATHE. Choosing A Bit First, the benefits of carbide supercede that of a diamond. Here's why. If you've never used a diamond tool bit before, you will probably chip it before you figure out how to set it up. Then you won't know it's chipped and you'll keep trying and trying and you'll look like Big Jim and Hank by the time you stop pulling your hair out. They chip very easily. Then you're out of a bit of money and have a whole lot of frustration ahead and behind you. Diamond bits are for experienced pit lathe users or machinists. I have been cutting toy motor comms for 30 years and I use carbide bits. Diamonds can go bad if you take too big a cut, if you hit the tabs, even if it was cutting fine when you packed it away, a diamond bit can be bad the next time you take it out. Don't ask me why. I have even chipped a diamond just by using the wrong kind of brush to clear the chips away. I figured out later that the steel band around the small paint brush I was using must have hit the tip. And no two diamond bits are the same as far as setup goes. Some bits need no shims. Others of the same brand and type will require 2 shims. Don't ask me why on that either. Carbide bits of the same brand always seem to setup the same. Another reason to use carbide is when it's dull, the finish looks like crap. A diamond will just start cutting out-of-round and you won't know it until your start putting your motors together because the finish looks fine. Unless you are extremely experienced, stay away from diamond bits. Use carbide until you gain that experience. Then you can either buy a tool sharpener like I did to do the job right, keep honing the tip with a diamond file until it is so distorted it (you unintentionally change the angles a little each time if you won't work anymore then sharpen by hand), throw it away and start with a new $4 bit or use a diamond. Here's the tool sharpener I use. I've had it since 1980 and it still works fine. www.glendo.com. CHOOSING THE RIGHT CARBIDE BIT The best place to buy carbide bits is McMaster-Carr www.McMaster.com. They are cheap and provide excellent service and on-line ordering and support. Or if you have a machinist supply close to you, do that. Try the phone book. To see if you need a left hand cutting or right hand cutting, see which way your lathe trues toward the tabs. But remember, your bit is installed upside-down so it will be backwards to what you have to order. Remember that most of the machining world cuts with bits right side up. So if your lathe cuts from right to left like my Integy Xipp or my old Cobra, you'll need a left hand bit. The old Twister lathes cut from right to left so they'll need a right hand bit. On page 2327 of their on-line catalog, you'll see a bunch of different bits of different angles. Unless you have a tool bit sharpener, get the AR series, either R for right hand cutting or L for left hand cutting. Also get the "4" series for non-ferrous (no steel) cutting. And ALL pit lathes use a 1/4" shank. Don't get any other size even though it would fit in your holder. The point will be in the wrong place. So if I were ordering tool bits for my Integy Xipp, I would want an AL4 bit #3367A131. HAND SHARPENING YOUR CARBIDE TOOL BIT. OK, the #1 rule when hand honing with a diamond file is, NEVER, EVER FILE THE TOP OF THE CARBIDE PIECE. If you get this part even slightly rounded, it will have to be sharpened with a tool sharpener because you can never cut it back far enough by hand to make it flat again. Even if you do, it will likely be at the wrong angle. There's no need to hone this part of the bit anyway. The bit cuts from a sharp point formed by the convergence (coming together) of three angles on the bit. A new bit comes rounded on the point. It will work this way because it's uses the top sharp edge to cut with. But when this gets dull, you want to sharpen it to a point. When honing by hand, most of your work will be on the angled side (the part of the bit not 90 degrees from the commutator). However, you must lightly touch up the 90-degree side because of the burrs left from honing the angled side. Just a couple of strokes will do it (boy, I've heard that before, ha). Try not to change any of the angles; file the bit with that in mind. If you have a good magnifying glass it's helpfully in inspecting the point during the sharpening process. Use the #400 grit file (also available from McCaster-Carr) if you have some material to cut away and then touch it up with the #600 file. It may take a little practice to get it cutting the way you like it but just think of all the advantages you'll have over a diamond and if you screw anything up, it's only 4 bucks! April 7, 2002 "Brush Serrations Per Inch" How the serrators cut. First, serrations are made up of peaks and valleys but since it's only the peaks that touch the comm (if the valley touches the comm, there are no serrations left) this is what we concern ourselves with. Second, I'm listing the serrations on the different cutters and brushes by the number of serrations per inch measured from peak-to-peak. Also, I found that the "stack" of serrations on a brush can start in a peak or a valley The only brushes I found that start with the peaks were the T#4500's and the T#4455. Nothing strange there-they are the same compound. The only difference is the standup vs. laydown comfiguration. The number of serrations per inch indicate how "fine" or "coarse" the serrations are but not how many are necessarily on each brush. Since the dictionarys don't list the word "Serrater" we can make history here. Do we spell the tool that makes serrations a "Serrater" or "Serrator" . I'm not an English teacher but I say "Serrator", just looks better. If anyone out there knows any contradictory rule in English that says it would be proper to spell it the other way, let me know. So whipping out a magnifier and a steel machinist scale I did some measuring. Here are the results. SPI = Serrations Per Inch. PROMATCH SERRATOR TOOL: 36 SPI INTEGY SERRATOR TOOL: 32 spi (Same as the P-94 brush). TRINITY SERRATOR TOOL: 40 SPI (but much shallower than the others). TRINITY #4499 Brush: 44 SPI TRINITY #4500 Brush: 56 SPI TRINITY #4455 Brush: 56 SPI TRINITY #4383E (P-94) 32 SPI (Matches Integy tool). TRINITY #4380E (P-94) 32 SPI TRINITY #4383 brush: 56 SPI REEDY #767 Brush: 56 SPI Putnam Pro "green": 44 SPI Putnam Pro "red" : 44 SPI Putnam Pro "blue" : 56 SPI I couldn't figure a way to accurately measure serration depth. The Integy and ProMatch serrator tools "look" to be about the same. What if any difference there is in a "fine" or "coarse" serration as far as power output, I'm not sure yet. But it is general thought that a finer serration is easier on the comm. March 24, 2002 Competition Electronics TURBODYNO 45 Settings These are the settings I use. Although these certainly aren't the only ones to use, it does establish a baseline to start with. But I caution you on this. NEVER COMPARE DYNOS! They are all different. Mine may not be the same as yours. But it's not important. As long as you use your dyno and you can improve your motors with it, the number values don't have to compare with anyone else. And they probably won't. Use these settings and numbers as a guide only. Your numbers maybe be better or worse. VOLTAGE SETTINGS FOR 6 CELL TESTING ON SPEC (27t, 21t, 19t) MOTORS: 7.0V FOR 4 CELL TESTING ON SPEC (27t, 21t, 19t) MOTORS: 5.0V FOR 6 CELL TESTING OF MODIFIED MOTORS 11 TURNS OR MORE: 6.5V FOR 6 CELL TESTING OF MODIFIED MOTORS 10 TURNS OR LESS: 5.0V FOR 4 CELL TESTING OF MODIFIED MOTORS, ALL WINDS: 5.0V In case you are wondering why I test low wind mods on 5.0V even if they're going to be run on 6 cells is because those type of winds spin so hard that it's very destructive to the slave motor on the dyno. With extreme low winds, a 5.0V setting will still tell you all you need to know accurately. I should mention also that I'm not going to post all the readings from all 6 settings in my examples. You may not need to use all 6 and it will save space and get you the necessary info. AMP LOADS ALL SPEC MOTORS (27t, 21t, 19t) 4 OR 6 CELL USE (Except Oval): 15A, 18A, 20A, 22A, 25A, 28A *Most Important for 6 cell: 20A and 28A 4 CELL OVAL: 15A, 18A, 20A, 22A, 25A, 0.0A *Most Important for 4 cell: 20A and 25A MODIFIED MOTORS: 11 TURNS OR MORE: 4 or 6 cell 20A, 25A, 30A, 35A, 40A, 0.0A *Most Important 30A and 40A MODIFIED MOTORS 1O TURNS OR LESS: 4 or 6 cell 25A, 35A, 45A, O.O, O.O, O.O *Most Important: ALL EXAMPLES: My Best P2K2 @ 7.0V: 20366rpm 6.8TQ 103W 74EF @20A 17270rpm 10.1TQ 129W 66EF @28A My Best GM3 @ 7.0V: 23474rpm 6.0TQ 102W 72EF @20A 19550rpm 8.8TQ 128W 65EF @28A My Best MVP @ 7.0V: 19874rpm 6.9TQ 102W 72EF @20A 16659rpm 10.0TQ 124W 63EF @28A *Note: MVP Watt numbers can be slightly lower than Epic motors and still run comparably. This is because of the supereior magnets, my best guess. My Best Chameleon @ 5.0V: 18708rpm 5.5TQ 77W 77EF @20A 16632rpm 8.9TQ 109W 78EF @28A My Best Street Spec (21t) @ 7.0V 17964rpm 7.8TQ 103W 73EF @20A 16125rpm 10.6TQ 126W 64EF @28A Excellent 11x3 Ti Modified: RPM Blank, 6.5V 35041rpm 6.6TQ 168W 85EF @30A 31561rpm 9.1TQ 212W 84EF @40A Excellent 8 turn HVW2, 4 cell Oval: RPM Blank, 5.0V 35762rpm 4.5TQ 119W 79EF @30A 32234rpm 7.7TQ 184W 81EF @45A REMEMBER, THESE ARE JUST EXAMPLES. March 8, 2002 Using the Sonic Fiddle Stick The SONIC Fiddle Stick, available from Big Jim Racing, is a very useful motor tuning tool. Motor springs that are too soft for a motor's application will glaze and overheat the brushes and commutator and cause the motor to never be able to finish a race strong. On the other hand, a motor with too much spring tension will lack top end and run hot. It's just like running a disk brake on the motor. Through trial and error or following the advice of yours truly, the Fiddle Stick can make the difference between winning and losing. Before using the FS, I recommend a slight modification to make things work a little easier. First, with a Dremel tool or just a piece of sandpaper laying flat on a table, debur the grooved end a little. I put quite a taper in mine. This makes that end be able to lift the spring from the tab easier. Next, put a drop of oil on the slide and work it back and forth. Now your tool is ready. It's always a good idea to open up the tab on top of the brush hood. Those sharp corners let the spring stick down in there and make measuring difficult. Just open it a little. I use the socket end of my spring post tool but a small screw-driver works just as well. I have found two ways to use the tool that works quite well. I'll tell you the one I prefer first. Method #1 1. After you've opened the spring tab a little and installed the spring, place the grooved end of the Fiddle Stick over the spring next to the right side of the spring tab (left side for reverse springs) on top of the brush hood. Hold the tool between your index finger and your thumb. Push gently on the spring as close to the tab as you can, until the spring barely lifts off the tab. At this point look at the gauge and read the tension. Do it a few times just to make sure. Method #2 2. Method two is similar to #1 except you don't hook the spring on the tab. You just push the spring up to the tab with the tool just like you were using it to install that end of the spring under the tab. Make sure the tool is in the same place as method #1, on the right side of the spring tab (left side for reverse springs). When the spring is in position to go in the tab, look at the tension on the tool. This way does eliminate the spring sticking in the tab but there's more chances for your tension to vary. I call the tension the Fiddle Sticks reads as units. Here are some tensions I get so you can compare. Trinity Purple spring = 7.0 FS units Trinity Red Spring = 6.5 FS units Trinity Green Spring = 6.0 FS units Trinity Black (laydown) Spring = 6.5 FS units Reedy hard copper = 6.0 FS units Stock MVP Spring = 6.25 FS units Gold Epic tear-down Spring = 4.0 FS units Here's some spring measuring hints. Keep your Fiddle Stick 90 degrees to the end of the spring. Keep the end of the tool as close to the side of the hood tab as possible without it dragging on it. Run about .5 units more tension on the positive side. Don't tweak your springs much more than .5 unit stronger or lighter than they came. It's always better to over-spring than under-spring. February 18, 2002 Potential "Narrow" brush problems For this week I want to mention the one biggest problem racer's have with the narrow brush MVP. Since this is the recommended tuning procedure for the new Peak Hellfire also, it's important we discuss this. Since few racer's ever e-mail me back with their gearing they finally settled on with a particular car and track type, I haven't got any of that data. So when a BIG JIM RACING Customer gets his BJ Tuned MVP in the mail and installed in the car, that's when the head scratching starts. Although I always say start with the same gear you'd run with a P2K or maybe one tooth smaller on the pinion, this would assume that racer has run a P2K. So now what? OK, that's when my customer goes to his local track and asks the local "hot shoe" what he would gear an MVP (not saying a "narrow-brush" MVP). Thinking the racer had a normal high-rpm full brush motor, he tells the racer with MVP in hand to gear it so-and-so which the racer does. The problem is, the full-width brush MVP is very rpm-ish and any gear ratio this type motor would run well at, would be 3-5 teeth TOO LOW (too small a pinion)for a narrow brush version. When his highly tuned BJ MVP is a Piglet, it's right to the e-mail and I have to assure him if he would just gear it the way I tell him, it will be fine. He thinks to himself, self, "the motor was a pig on the bottom end too. If I gear it the way Big Jim says, it will even be worse on the bottom end". Well, not so Grasshopper! What most people don't understand is electric motors are not gas engines! A gas engine has to reach a certain rpm when maximum torque is reached. The lower you gear a gas engine, the more torque it has because it's closer to that rpm point. An electric motor has it's maximum torque at ZERO RPM and it goes down as the rpm goes up. Therefore, the slower you run it, the more torque it has! This is why you can use a larger pinion and have even more punch than you had before with the smaller one. Sometimes it's not readily apparent on a car with a tranny and gearbox but if you have ever raced an pan car much, you know this is a fact of life. Sometimes, racer's also forget this basic fact. The #1 criteria you should use for setting your gearing is your lap times! Not infield punch, not top-end speed, not even motor temp. LAP TIMES!!! Who cares if you have good infield punch, good top speed and your motor stays an ice-box if everyone is beating you! Still don't have a clue on where to start your gearing? First, ask someone where they would start with a P2K. Then start there. Run 1/2 a charge with a friend getting your lap times. While you're repeaking, change your ratio either taller or shorter (higher or lower). Go out again, run another 1/2 charge and again with your friend taking lap times. Are your lap times faster or slower? If you went taller and you're faster, GO UP SOME MORE until your lap times fall off. Then go back one tooth. If you went taller and you're slower (unlikely) then go the other way. Are you faster now? Yes, then keep going until you find the ratio that gives your fastest lap time, period! Use this method and you'll never be wondering if you have the right ratio or not.!!! February 11, 2002 How to: check for a bad armature. WHAT YOU’LL NEED!! 1. An old but clean can and mod endbell w/bearings in good order. 2. A Digital multi-meter for checking continuity. 3. Magnifying glass or Mag light. 4. A good set of calipers. 5. An old armature to help explain these tests. Not even experts can tell if an armature is 100% good just by looking butA visual inspection is the best way to start. The most important part of the armature that eventually gets too small to use is the commutator. I don’t recommend an arm be used if the commutator is smaller than .270" (6.86mm). You can stretch this figure somewhat if you are running stock class and only using 4 cells. But if you’re running 6 cells in a TC and your 8 turn is at this limit, don’t cut it again and use it. I’ll tell you why. When the commutator is made, it’s not made round. It’s only round when it’s trued. Each of the 3 commutator segments or plates are the same thickness but the hole isn’t on center. Therefore, as it’s retrued each time, one or two plates are thinner than the other one or visa-versa. The commutator is only as good as the thinnest plate. When a plate gets too thin two things happen. First, the thinner plate can’t carry as much current as a thicker one. Therefore, the currentlooks for an alternate path, one of lesser resistance. As the resistance builds up in the plates, the brush arcing increases. The bigger arc tries to jump anywhere it can to make a connection and it jumps UNDER the plates! This eats away the phenolic under the plate and soon the thin copper will actually peel away from the brown center insulation. If the motor is running at race speeds, this causes the brushes to self-destruct, knocks out your hood alignment and you lose the race unless it happens just as you cross the finish line. Yeah, fat chance of that. It could lock up the motor causing you car to stop unexpectedly (for everyone else too, besides you) and you have 9 other cars nailing you hard. IMO, going below .270" is just not worth the chance. Measure the comm every time you true it so you know where you’re at. BTW, I have found there is no "ideal" comm diameter. A large comm has more torque and will flow more current. A smaller comm has less torque but more rpm. Since HP=RPMxTorque/5252, it’s really just a trade-off because your total power is about the same. You will have to change your gearing to compensate for the torque loss and rpm gain as the comm gets smaller and also increase your spring tension slightly because the brushes are going to sink further down in the hoods, relaxing the spring more. If your comm is still good sized, check for loose wires. If you can move any much with your fingers, that loose wire could keep stretching and start rubbing the magnets and even lock the motor up and you end up being nailed by those 9 other driver’s again. Stock unepoxied arms can be saved however. Mod arms can’t without re-epoxying them. If you think the wire could cause problems, push it down tight against some other wires and put a drop of CA Glue (Crazy Glue, Hot Stuff, Permabond, etc.) on it and the surrounding wires anchoring them all together. Set it aside for awhile until the glue sets. BTW, CA glue is only good to about 200 degrees F. So don’t run it too hot. There are some clear adhesives made by Loctite that have a higher temperature rating but they have to be special ordered and for most stock arm applications, the CA will work fine. Check both ends of the shafts when they turn in the bushing. If they’re scored or scratched, chuck them in a drill and sand them with #400 grit paper. The finish with #2000 grit (or fine crocus cloth) and polish as described in the Black Book and on this web site. Ball-bearing mod motors won’t usually have this wear indicator AND USE TRIBO on the bushings and bearings. I have never worn out a bearing or bushing when TRIBO was applied before every heat. They go bad for other reasons but not from shaft wear. If some wires are skinned, this usually doesn’t hurt anything if it’s not touching another wire in the coil that’s similarly attired. Shaft straightness is difficult to check but if it makes a rattling sound in the comm lathe, that’s the first clue or if you have a hard time keeping a 64 pitch gear mesh, there’s another one. Checking the armature for electrical problems: OK, you probably won’t believe this one. I’ve seen the look from almost everyone I’ve told this to. It’s like "yeah, sure Big Jim". This is why I had you get an old armature for a graphic demonstration. Put that old arm with the worn out comm in that old can and endbell with no brushes! Now spin it by hand. See how many times it turns before the magnets pull it to a stop. Maybe 5,6,7 revolutions. Now take it apart and solder two comm plates together. Yeah, just blob the solder across the slot connecting two plates. Put it back together in the can. Now spin it. If you can get it to make two revolutions, you’re quite the man (or the mags are weak). By soldering the comm plates together you have effectively SHORTED the armature. The same thing happens when two bare wires in the coil touch each other. A shorted armature coil will not rotate in a magnetic field, even without brushes! Never thought that could happen did ya? Single and double wound arms are easy to check by this method. Triples will be a little easier to spin because only 33% of the wires could be shorted. Quads, well, you almost have to put some power to the motor with brushes installed to check it for sure,. With only 25% of the wires shorted, it gets harder to tell this way from a good arm. The absolute best way to check for any electrical problem is with an LCR meter. But they are about $175-$275. If you have access to one of those you can save yourself some time and know positively your arm is good or bad electrically. On Japanese machine-wound motors, one of the comm tabs that connect the wires to the plate could go bad since they are just heat crimped and not soldered or brazed like mod arms. If you have to push the car to get it going, or spin the arm by hand with power to get it to run, then the arm has an OPEN COIL. It will also run at about 1/3 speed but won’t draw any more current. You can usually fix that connecting tab by squeezing it tight against the wire again and soldering it with solder of high-lead content, acid flux and a very hot iron. You could have one last little problem that could render your capacitors useless and that is if your armature is GROUNDED. This also messes heavily with the inductance of the coils. Take your digital multi-meter and set it for "ohms" on the lowest setting. Touch one probe to the comm segment and the other probe to the shaft or the stacks. There should be no reading. If there is any reading at all, no matter how slight, the coils are grounded and it’s just a matter of time before you have real problems, if you haven’t already. If you’re just a basher, you may not even notice the difference. It may look like your pack didn’t get charged as well or some excess drag in your car somewhere. So your armature could have 3 distinct electrical problems and now you know how to check for Shorts, Grounds and Open Coils. BTW, before someone asks the same old question, no, you can’t measure the resistance of the armature coils with a standard ohm meter. The resistance is way lower than the capabilities of the meter unless you have one of those LCR meters that I mentioned earlier. January 28, 2002 BALANCING- Not really an enigma but there are things you should know and look for. There are two types of balancing. Dynamic and Static. Static Balancing- Uses only one plane. A good example would be a prop or cap tire balancer. Or a bubble tire balancer for big cars. This is simply putting weight on the lightest side of something round. This works OK when the thing you are balancing is bigger in diameter than it is wide. Dynamic Balancing- Uses dual planes. When something spins very fast and it's longer than it's diameter, it must be dynamically balanced on a special machine designed to do this. For example, our r/c motor armatures. Definitely fits the criteria for needing this type of balance. The balancing machine divides the armature into two parts, right and left. It balances both ends of the armature separately but since each side (right and left) are actually on the same part, it must balance both ends in relationship to each other as well. I know this is a bit confusing but it's all necessary to get a motor that runs smoothly at 40,000 rpm. Using the Vector Principle - This is why our armatures are drilled down the center of each stack. TWO TYPES OF R/C BALANCING Epoxy Balancing- This involves adding weight to the armature in the form of a weighted putty on the lightest areas. It sometimes is air-dry, sometimes oven-dry. The proponents of this type of balancing say it saves all the metal in the armature and gives the armature more torque because of that. Opponents say it adds centrifugal mass to a rotating object, the epoxy weight changes over time making the arm out-of-balance again and it sometimes fly's off making the arm really out-of-balance. Also, it takes more time to process the part and rebalancing is always done by drilling anyway. Drill Balancing- This is just what it implies. A small drill, usually a center drill takes away metal from the heavy area of the armature using the Vector Principle (more on this later). Proponents of this type of balancing say the armature stays in balance better and doesn't add excess weight to hinder spool-up of the armature. Opponents say it takes too much metal out of the arm and since there's less steel, the pole with the most holes is weaker, limiting torque. The TRUTH!!!! These are facts! 1. The companies that make the balancing putty say it's not intended for speeds in excess of 30,000 rpm. 2. Every time you cut the comm, the armature goes more out-of-balance from when it was new. No motor tuner in the r/c industry rebalances by adding weight, that I know of. They always drill correct. 3. It is the standard procedure in the small, high-speed motor industry (outside of r/c) to drill balance the rotors. It's faster, stays balanced and never "loses" it's balancing weight. Very precision and expensive aero-space motors have drill-balanced rotors. They can't afford to have the weight come off or the balance change. Imagine what would happen to a dentist's drill if a balancing weight came off while the drill was in someone's mouth spinning at 100,000 rpm? (yeah, I know they're air-powered but still motors). MY OPINION The area which most drill-balancing is done on the armature is in the middle of the crown. Since the armature is pulled and repelled by the magnets reaction to the tips of the crown, the area on the stack that is drilled is far less important. Even Trinity who started this whole epoxy balancing idea, has a balancing groove right down the middle of the stack, removing metal from that area. If it's so important to have that metal there, why is it that every Epic motor armature has this groove? It seems hypocritical to me to say how important the metal is to the function of the motor and then design the part so that the metal is removed! There is a time however, when even I would suggest a small amount of balancing epoxy. Sometimes, very packed armatures are really out of balance and would necessitate a very large hole drilled in one stack or more. Since the hole would be so deep down into the web, it could effect performance. I suggest a small ball of balancing weight added to the light side and then finished by drilling. This way the correction hole isn't so large and the added weight is minimal. Ever wonder why the drill holes are right down the center of the stacks? What happens when the heaviest part of the armature that needs to be drilled is right where the wire is? This technique is called the Vector Principle. If you have to remove x amount of weight from an undrillable area of the armature, you can take x+1 amount from a drillable area on both sides of the actual heavy spot. This is basically what the Vector Principle entails. Since our three pole armatures have stacks 120 degrees apart, there really shouldn't be more than two holes on any two stacks. There is no need to have all three stacks drilled on the same side. Well, boys and girls, this is theoretical. If the balancer was working perfectly (with small razor-like chips everywhere) and if the operator was 100% accurate all the time (with those little chips embedded in his fingers), the commutator already cut and the arm never needed rebalancing (some boob dropped it), then two holes is the maximum you would need. But it doesn't always work like that no matter how good we are or how good the machine is. Sometimes you go over and have to retouch on the third stack. Just the way it is. When you rebalance an armature, all bets are off anyway because the balance is apt to change to the undrilled area. Thus three drill holes are needed. When I balance stock arms done in Japan, they over-drill a lot but don't recorrect. They have a larger tolerance than I do so I sometimes have to drill on that third stack. So it isn't out-of-the-ordinary to see holes in all three stacks on both sides, thus 6 holes! However, if the armature is brand-new and never been rebalanced and it has 6 holes drilled in it, that means the operator had to make a mistake on both ends. In other words, twice per armature. No very quality controlled. Most spec class armatures (27 turn, 19 turn or 21 turn) respond well with lots of metal removed. More rpm. So it doesn't hurt them. In mod arms, it may not hurt anything but it sure is a sign that somebody doesn't have their mind on their work or the balancer is in need of repair. Either way, I wouldn't buy a mod arm with six (sometimes even more) holes in it. This is the real story about balancing. I've been doing it for 24 years. When you can hold an r/c motor running on 6 volts between your front teeth, that's a good balance (happens about one out of 50). January 21, 2002 Wh the SMD capacitors go bad sometimes and how you can check them. I hated capacitors as a motor builder. Always soldering them on at the last minute. Always in the way when rebuilding a motor. And cleaning up a broken off one and installing a new one was really time consuming. Along comes the installation of the SMD Capacitors, aka SMC's or internal caps, on our race motors. Most Epic motors and some Orion motors have been using the SMC's for about two years now, with reasonably good success. I say "reasonably" because there are those who believe SMD type capacitors shouldn't be in such a harsh environment. Sometimes they do go bad, like everything else. There are two ways they can go bad. The first way causes the biggest problems. Shorted Caps. Capacitors normally have no continuity. This is why they can go between a positive and negative poles on a power supply, for example. But shorted caps do have continuity. Because they are so small, they won't read as a "dead-short". "SHORTED" CAPACITOR SYMPTOMS: The motor will draw lots of power (amps), run hot with diminished speed or any or all the above. CAUSE: Running the motor at full race voltage before the brushes are seated all the way. This causes high-voltage spikes which could short the cap. T does this on every "Pro" version they sell. It's not surprising that we don't hear more of this happening. Get a regular Epic and save yourself some time. The best way to test a capacitor is with an LCR or capacitance meter. But they are expensive and most racer's don't have access to one. However, this is still the only way to test the value of each of the capacitors in the endbell. Use a standard multi-meter, set on resistance on the lowest scale. Test this way. Be sure and pull the brushes away from the commutator for these tests. 1. Put one test lead on the neg side of the motor and the other on the pos side. This tests the center cap in the bearing/bushing tower. 2. Put one lead on the pos side tab, the other on the endbell mounting screw. This tests the cap on that side. 3. Put one lead on the neg side tab, the other on the endbell mounting screw. This tests the cap on the other side. THERE SHOULD BE NO CONTINUITY in any of the tests. As a final conclusive test, take the leads from a high-amp power supply and touch the endbell in the areas mentioned. Any shorted cap will register some reading, even if they don't show up in the first 3 tests. Good caps read nothing in all the above tests. The second way they can go bad is "opened" capacitors. This means they act just like they aren't there, even with a capacitance meter. In other words, they're doing nothing at all. "OPENED" CAPACITORS SYMPTOMS: Glitching, whenever the motor runs. It happens at any track or area, even if there's no one around but you. The capacitors are there for a reason. They absorb RF interference so the receiver in the car doesn't mistake these random RF signals as commands from the transmitter. If they aren't doing their job, the car will glitch. Sometimes uncontrollably. If this is your problem and you suspect the internal caps, either have them checked on a capacitance meter or just replace them. Trinity sells their's as a full set for $2.00. They actually cost about $.08 each from Newark Electronics. .1uf @16VDC is the value. CAUSES: Same as the reason above. Also, a bad connection in the cap hardware. You should clean with Lysol Tube and Tile cleaner. Detarnishes the endell hardware The third way the caps can go bad is that they aren't their specific value anymore. This can only be tested with a meter designed to test capacitors. I don't advise putting the standard external caps back on. If you have to replace them, get the exact value SMC's to replace. January 15, 2002TUNING TIP FOR JANUARY 15th "I've followed the directions for aligning my brush hoods exactly like it says in the Black Book of Motors. And the commutator is still wearing the brushes on one side. How come?" Here are a few advanced tips and how you can be fooled when aligning your brush hoods. 1. You must use the same size "test" brush as the ones you are going to finally put in the motor. This is a common mistake. If your test brush is bigger than your race brush, it won't shift as much in the hoods. This will cause the comm to wear on the leading side of your race brush. If the test brush is smaller than your race brush, it will shift too much and the comm will wear on the trailing side of your race brush. 2. Don't just spin the armature by hand to check the wear mark. You have to make the wear mark on the brush by running the motor under power. Otherwise, it may not shift the same way and throw your alignment off. 3. You can use the same pair of test brushes many times.Look up a welding supply place in the phone book. Go there and get a BRASS bristle brush called a "toothbrush" because it's a small wire brush similar in shape. It's less than $3 and is soft enough to "wipe out" the wear mark on your test brush without distorting it. This way, you can use the same pair over again. Eventually, all the different wear patterns from all the comms will change the curvature of the brush and make it shift differently in the hoods so replace them once-in-awhile. 4. Visualize how the brush is shifting in the hoods. If you do this, you can determine what needs to be done to the brush hood to counter-correct the shifting. Don't just move the brush hood up or down while still being pushed against the endbell (or heatsink). You'll change the timing. Usually, the leading side of the brush hood has to be kicked out or away from the bushing tower while the trailing side stays tight against the bushing tower. 5.Use the alignment tool! Don't use your fingers or pliers. Get the tool. Racer's Edge sells one and so does Niftech (the Niftech one is lots more expensive and does the same thing). Only with the tool can you keep enough "pulling down" pressure on the hood to tighten the screws and keep it there. The tool also keeps the hood sized properly (not too small anyway) as you pull and push to align. 6.Enlarge only the spring post hole. Most motors don't need the endbell mounting holes enlarged to properly align the brush hoods. There's enough play in the holes to twist the hood/heatsink assembly with the tool to correct the misalignment. The Yokomo MVP is an exception. Just elongate (make the hole oval shaped) toward the endbell slightly. Don't do anything to the Phillips screw hole. It's large enough already. If you enlarge both screw and spring post holes, you won't have a reference point when you put the endbell back together and you probably will never get them aligned right. 7. Move the brush hoods and heatsink as one assembly. Don't try to move just the hood on top of the heatsink to align. On Epic motors, the "dimples " will prevent that anyway. Move everything together. There you have. If you aren't clear on how to properly align the brush hoods on any motor, go to "Big Jim's R/C Motor Black Book". There's a link to it from this site. January 8, 2002 Polishing the shaft for more rpm. I used to break-in the bushings on stock motors but I don't anymore. I've found a technique that is easier, faster, works better and you don't have to worry about getting all that abrasive stuff out of your bushings. You polish the shaft. This works for a used motor as well as a new one. Go to the hardware store or a Pep Boys and get some #1500 or #2000 grit wet-or-dry sandpaper. Pick up a sheet of #400 too. Also, some metal polish like Blue Magic or other low abrasive polish. Take the motor apart. If it's a used motor you are rebuilding, it could have some score marks on the shaft if you forgot to use some good oil on the bushings. Check the armature in a drill and sand the score marks with the #400. If you don't have any marks, start out with the fine stuff. #2000 grit paper will polish the shaft almost like a mirror. Next, take a clean rag and put some polish on it. Turn on the drill and go to it. You really only need to do the area that rides in the bushing but do the whole thing. It looks pretty. This should be done as your last step before assembling the motor. If you still have the comm to cut, do it before polishing or it will leave scratches that you just polished out. Put the necessary spacers on each end to center the armature in the magnetic field (see the Black Book for the proper way). Now for the important part. Just before putting the arm in the can, put a drop of TRIBO R/C Power Matrix Commutator Lubricant on the shaft near the spacers. Put it in the can and use the same procedure for the endbell. Once you have the motor together and the endbell screws tight, take the flat part of a pair of pliers (or similar tool) and lightly tap each end of the shaft a few times. This centers the bushing on the shaft. Check your spacing. Change if necessary. Spin the arm by hand. Feels good doesn't it? It works, trust the Big One. And check the link to my book, "Big Jim's R/C Motor Black Book". January 1, 2002 Don't run a fan on the shaft of the motor you're breaking in. A couple of company's sell those push-on little fans to cool the motor while it's running at 3.0V or so. This does a great job of cooling the motor but it causes the motor to draw another 2-3 amps. The extra amp draw causes the brushes to arc more during the critical break-in period which is harder on the comm too. Always break-in the brushes under a no-load condition. The brushes are considered seated when the entire brush face is riding on the comm, from all four corners. This also means the tips of the serrations. It is not necessary to wear the serrations away for the brush to be seated properly. A fan is a good idea to keep the motor cool but make sure it has it's own power source.