A Collection of R/C Modelling Tips - RC World

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it stops running smoothly) and causes a PCM lockout and a subsequent crash.Loose screws and vibrating washers also need to be taken care of.The only counter measures that I can suggest would be to make sure that anymetal to metal connections are snug.Tinting CanopiesThis is probably "more than you ever wanted to know" about dyeing canopies, but it was an easy cut'n'paste froman RC club newsletter, so what the heck, here it is in its entirety. Apologies for the length to those who aren'tinterested, but I'm too lazy to edit it down :-)Ever wonder how those great looking tinted canopies got that way? In many cases, the builder dyed the canopyusing dyes intended for tinting clothing! The process is actually quite easy, and the dye itself is easily obtained andquite cheap. I've found that Ritt powdered dyes are quite effective in tinting the plastic canopies found in mostmodel kits, and are available in most drugstores, priced around $2 per package. When using powdered dye to tintplastic canopies, here are some tips to consider:• Make sure that the canopy is squeaky clean before dyeing. Washing in mild dishwashing detergent iseffective here, and will avoid unsightly fingerprints in the final work. Dry using a soft cloth (not papertooling, which is almost always abrasive to some degree).• The container used for dyeing must be clean as well. Stainless steel or glass containers are the best forthis process. Use a container that is just large enough to allow the canopy to be fully immersed in the dyebath.• Wear something appropriate for working with dye. It is also a good idea to place the dyeing container withina stainless sink and to clear any items from the working area. If you do splash some dye on a hard surfacein your work area, some diluted bleach will take the stain out (rinse the area thoroughly with water afterusing bleach!).• A meat thermometer is perfect for measuring the working temperature of the dye solution. Also, a pair ofcheap wood or plastic tongs are handy for handling the canopy while it's in the dye bath.• Fill the container with hot water first, then pour in the dye (this will help avoid splashing dye around). Mixthoroughly but avoid splashing. Remember to use only enough water to fully immerse the canopy. Theobject is to create as strong a dye solution as possible to speed up the tinting process.• Always test the dye bath using the scraps of plastic remaining after trimming the canopy from its "asshipped" form, principally to determine if the solution is too hot. I've found that an optimal workingtemperature is 150-160 degrees F, but you should immerse a scrap for a few minutes to determine if thereis any chance of deformation at these temperatures.• Place the canopy upside down in the dye bath to avoid trapping air bubbles. To remove any bubbles and toensure consistent tinting, periodically shake the canopy gently within the dye bath using the tongs. Avoidscuffing the sides of the container with the canopy.• Periodically remove the canopy and observe the level of tinting. Some plastics take dye more readily thanothers, and the level of tinting you desire may vary, so you have to give it an "eyeball" every few minutes.• If you desire a really opaque level of tint, or if the plastic takes dye slowly, it may be necessary to reheatthe dye bath. This is where a stainless steel container comes in handy: remove the canopy, rinse it in tepidwater, and set aside. Place the dye container on the range and use LOW heat to gently bring it back up toworking temperature, checking with the thermometer. Don't overheat! Then remove from the range, and reimmerse the canopy.• Once the canopy has reached the desired shade of tint, remove from the dye bath and rinse thoroughlywith tepid water, then dry using a soft cloth.Voila! A professionally tinted canopy!
Ni-Cd Life - or why is down so quick?C. ScholefieldWhile volumes have been written on this subject I would like to relate it to the specific application of R/C ,separating fact from fiction and enabling the R/C fraternity to focus on more serious issues of the day, likeconvincing your wife it's too foggy to clean the pool so you're going flying while the field is not so crowded.The primary failure mode of Ni-Cd cells (outside of user abuse) is separator deterioration. This will occur in all Ni-Cd batteries as they age. The separator breaks down allowing the plates (electrodes) to touch and short out thebattery. Millions of testing hours on thousands of cells has established the mean time to failure of a single cell to be8 years for cells/batteries maintained at 25C (77F). Higher temperatures will significantly reduce these numbers.Mean time to failure means the time that it takes for half the cells in a given population to fail. As the cells are builtinto packs the mean time to failure decreases. For a 4 cell receiver pack the mean time to failure comes out to be5.7 years while an 8 cell transmitter pack falls to 4.8 years. Now it is completely possible that the average R/Cmodeler doesn't want to tempt statistics to the point where half of his battery packs should have failed. A morereasonable number would be the expected time for 0.1% of his batteries to fail. The number comes out to 58 weeksfor a receiver pack and 49 weeks for a transmitter pack. For the more adventurous willing to live with 1 failure in ahundred, he can stretch his receiver pack to 103 weeks and his transmitter to 87 weeks. Does this mean that heshould rush out and buy new packs at these intervals? Not really. Proper battery monitoring, while it may notsignificantly increase life, will give you ample warning that your pack should be considered for replacement.Remember, normal failure is the deterioration of the separator system. As the separator deteriorates (oxidizes) selfdischarge rate of the battery increases significantly. A pack that looses 15% or more capacity over a week of opencircuit stand is at risk. A pack that looses 10% overnight should be used for ballast only. Check your pack with acycler or some technique that gives you the amount of capacity available immediately after charge and then (afterfully charging again) after a rest period of 5 to 7 days.(NO, this isn't MEMORY!). Doing this at least quarterly (if youare fortunate enough to live where you have a flying season longer than 3 months) will greatly increase your oddsof crashing by some other defect than battery failure.The number of cycles you put on your battery is secondary in the life equation, again, assuming you don't abusethem by high rate over charge, vibration or exposure to high temperature. I know of very few people that totallyexhaust their battery packs while flying (at least not as a matter of course) so the packs seldom see a full dischargeand the risk of cell reversal is nil. Test have demonstrated that hundreds of cycles of reversal where 140% of therated capacity is taken out in a driven discharge resulted in a capacity loss that was barely measurable. Many multispeed power tools use the technique of tapping the battery for speed control with no adverse effects on the battery.A single cell can be discharged through a load to zero volts without damage. In fact this is a good way to determineif a cell has suffered from separator deterioration. A cell discharged to zero volts will recover to over 1 volt opencircuit if left to stand. Those that will not are approaching the steep part of the failure curve and could be a crashwaiting to happen. Bottom line: the number of full charge/discharge cycles that can be accumulated by today's Ni-Cd technology is in the 400 to 500 cycle range. Of course partial discharges seen in the R/C application can extendthe use cycles to significantly more than this. It doesn't take a battery expert to figure out the amount of flying timeyou can accumulate on 500 full discharges. We are talking in excess of 1000 hours. If you put in a full two hours aweek in the air every week year round, you would be well into the next century before you reached 500 cycles.Separator failure or old age will probably do you in before you run up 500 cycles. Meticulously recording thenumber of discharge cycles to establish a replacement schedule can be a study in futility and should be left to theelectric R/C indoor microfilm pylon set. Don't worry about reversal. If you have left your switch on overnight or foreven a couple of days, just give the pack a good long slow charge using your regular charger supplied with thesystem for 48 hours and you will probably be OK. It would be prudent to run a capacity check cycle after such anincident just to make sure.Long term overcharge, leaving your packs plugged in to the charger supplied with the system, while considered anacceptable practice for many consumer applications can contribute to a reduction in battery life. First, as a batterygoes into overcharge, oxygen is generated on the positive electrode and then recombined on the negativeelectrode. This oxygen rich atmosphere only accelerates the oxidation of the separator. As the oxygen isrecombined on the negative it generates heat. We all know how to make a chemical reaction speed up, turn up theheat.One further phenomena recently brought to light after years of testing is that of cadmium migration. This is atransfer of cadmium metal through the porous separator structure to form a conductive bridge between theelectrodes. In simple terms a high resistance short which causes the cell to self discharge, shunts charging currentto where the cell takes longer to charge and ultimately, if left of continue, become a hard short which, if happensduring a period when batteries are part of, or contributing to the direction of an airborne operation, result in a rapiddepletion of model resources. The same testing reference also confirms that the same amount of charge put intothe battery in a short period significantly reduces the cadmium migration. Therefore using a simple appliance timerto switch your charger on for about an hour a day minimizes the overcharge and yet maintains the packs at peakcharge should an airborne operation be called for at any time. For the experimenter, a charger designed to charge
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