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Its All About - Realism & Scale! A Real Workboat has a Top Speed between 12 & 18 mph, which is the fastest any Tug or Towboat = Can Attain. So its main engine ('s ), are turning only about 1,000 RPM's - At Most, which is further reduced by its Gear Reduction or Transmission. And that, means the Prop or Wheel, may only be turning 150 to 300 RPM at Most. So - Ok, your building a model and installing a pair of DC Motors that turn 12,000 RPM ......... So Now Your wondering if they will be - OK? .... RIGHT! Well the # One Rule In Workboats, is SLOW SPEEDS - When MANEUVERING! So wouldn't ya say - that sorta screws up "The Whole Theory?!?!" Well below - I've compiled some basic - guidelines to assist the Novice, whom needs help choosing the right types of DC Motors. Hey - This ain't "Rocket Science" guys, so relax & read a little further before you install a motor - You may regret doing = Later! ....... Cause that's about when you'll realize Old River Bill's = Been There, and Done That Too!!!!! ___________________________________________________________________________
Dc Motor - Basics Used in Model - Tugs, Towboats, Ships, Subs, Cabin Cruisers, Sailboats, Pontoon Boats and other slow moving R/C Craft. DC Motors .... come in all Sizes, Types, Brands, Voltages, Current Ratings & Rpm. Ranges. The best motors are always the ones that are "Fully Shielded" in a metal case and - Ends, to reduce - RF Noise. Cheaper motors are always bad about causing rf noise, created by electrical noise from their brushes and will often cause an r/c radio - or its servo's, to Chatter, or Glitch Meaning they need - Noise Suppression Capacitors to stop this interference. .. So Read Further Below! RULE # ONE .... A motor doesn't have to turn faster, than about 5,000 rpm in a Model Workboat. RULE # TWO .... A motor doesn't need to draw "More Than" 2 Amps, under full Load, meaning its shaft - locked tight, with full voltage applied! RULE # THREE .... 3 to 12 Volts, in these types of Motors = reduces your cost and saves Batteries too! RULE # FOUR .... There are certain trade-off's, that allow some motors to be used, provided certain limits are followed like in Rule # One & Two. Here,, usually 4 Amps is the Absolute Limit for a DC Motors = Full Current Load. And anything turning over 12,000 Rpm, is a wasted effort in smaller motors, used in a model workboat. Even when operated at a lower than 6 to 7.2 volts and directly driving the Prop, these motors on less voltage - are a waste of time - in my opinon. That-Is, unless you add a "Gear Drive" to further reduce the motors = rpm speed, going to the drive shaft and Propeller. So, there are ways to get around things, provided your willing to keep an open mind as to what you need to do, in order to allow a model to operate properly at scale speeds!
Above - Left Photo = the Pittman 12 volt Dc Motor Right Photo = the Radio Shack = RS 273-256 Motor Pittman makes all kinds of motors, but the ones - we use in workboat models, are rated 2.1 Amps at 3,300 Rpm.` The Radio Shack - Mini DC Motor, shown above is rated 1.5 Amps and turns about 11,500 Rpm. and can be used in small models - if given a gear drive. Both can be used in certain applications, if you also use a "Gear Reduction" system - as I said. Or lower the Input voltage - in either motors case, which may mean it only operates on 7.2 volts, or at about 7200 rpm's. And therefore easily can be further reduced, using gears to slow the rpm's further down, going into the drive shaft on small models. Also, if the motor is capable of running easily on a small 9 volt dc transistor radio battery, it can even be used to power a small out-drive on a Sailboat - for example, it will also work fine! THE ANSWER TO RF NOISE = Simply add a pair of small non polarized capacitors, to reduce the RF effects, caused by tiny sparks produced by the motors - Bushings, Bearings and/or Brushes. Noise Suppression Capacitors are very small Capacitors or Caps - as I call them. Available from any electronics' parts suppliers ( Radio Shack ) and cost only a couple of bucks - at most. Their ratings should be between .01 to .1 MFD. = Micro Farad and they also need to be "Non-Polarized" types. Non-Polarized - means, the Caps - don't have any Negative or Positive polarity. So they can be wired to the motor - terminals, with either of their - two leads. The Other lead, is soldered directly to the dc- Motors = Case, which then forms the "RF Shield" that reduces the motors noise output, by grounding them out. This usually stops problems = like when a "Speed Control" or Servo, suddenly Goes - Wide Open, or servos suddenly Go- Hard Over, or wiggle & Chatter, for some unknown reason. And this addition to the motor, doesn't effect it, in any other way, except to enhance its use in R/C modeling! The Faster Motors - Turn ..... The Higher = its Current Needs, and the more RF noise = it Will create Being another reason to stay with slower operating motors, or using shielded DC Motors - that are always heavily made, with a much thicker - metal case, for Noise Suppression. Cheaper motors usually have - Thin metal cases, or Plastic - End Caps, that offer far less protection from RF Noise! ___________________________________________________________________________
Motor Ratings NOTE .... Not all suppliers of motors, rate them - the same way! Here, you can be easily fooled into thinking a motor will be ok, when its not a good choice. So you have to look at the info - they supply on the motor, then determine if its ratings fall within certain limits of what you want it to do .....Or NOT Do? Example, - a motor is advertised = Operates at 6 to 24 volts, draws 5 Amps, under Full Load, at 10,000 Rpm's. But your going to power the motor - with only 6 volts. So that would reduce its Rpm and Current Load, within a respectable range of what falls within my rules - Right!..... "Or Does IT?"..... It will work - yes, but it will also be very sluggish at 6 volts, because its being starved of what it craves - More Amps. So it doesn't respond very well, and doesn't have much top end power. Plus its still drawing more current = then is really needed, so it draining your battery faster. Now, does this make sense?....Or What?? I think your getting the idea - now, because this is sort of a trade-off, which sometimes works, only if certain things, fall within refined limits. Current - is the problem here, because the motor is designed to work at higher speeds - with more amps, then you require...."So this is not a good trade off, or Buy" However, had the motors info said it only needed 3 Amps, at full load at 24 volts, it would have been a much better choice!.....So shop around and compare dc motors, before you buy them. ___________________________________________________________________________
Buying DC Motors - DIRT CHEAP! Meaning no disrespect to any hobby shop, supplier or manufacture, "But guys - If ya wanna save some $$$$ .......... And High Prices are hard to swallow, even when buying simple dc motors, like the commonly used = Dumas Motors, costing over $65.00 - Each Then try these sources and see if you can find a few more bargains to make you happy! I've found motors & other stuff - far cheaper from these sources. And I've been able to get almost the exact same motor or parts, for as little as 5 or $10.00 - Each. Visit My - Modeling Links Page" and check out sources like - E-Bay = "Electronic Parts Suppliers" and also "Electronic Project - Kits." They buy large quantities of overstocked parts from manufactures, then resell them for pennies on the dollar. No matter what you need, these sources usually have a dozen different versions - On Sale, at a whole lot less. Far less than buying them from the usual hobby sources, which includes DC MOTORS - with Gear Drives too. Some are name brands like Pittman Corp. / Globe / Johnson / Mabuchi and Astro and are guaranteed "New or Used" the motors - runs. But lately, prices have been going up, so a motor that used to cost = 5 to 10 bucks, may cost you a little more today. Why?.... Because everybody is doing = what I'm doing. Trying to get the lowest price, by comparison shopping for used or rebuilt motors and other items!
Other Important Factors - To Consider When Buying Gear Drives & Motors # One ..... What Scale - Is The Model = Its OVERALL SIZE? .... This pertains to the models interior and what its Hull & Structures ( the interior will allow you to Install? ) Meaning things like - the Motor ('s ), Battery & Other Components, which may limit some of your choices? If your building a kit, do the plans recommend certain parts = Motors, Batteries - Etc.??? If So, you may have to stick closely to what is recommended, but even then, you may still have a few choices too. # Two ..... What Size Propeller ( 's ) will be Used? .... The size of the Propeller, or the larger its diameter, the more current loads it will cause on the - Motor, Battery & Speed Control. Here, even slight changes in Propeller - Pitch, using different props, can effect performance. Or increase or reduce the heat build-up problems on motors & speed controls. Boiled down to basic's = the whole idea, is to make a model handle best - at Very Slow Speeds, without adding un-needed expense! # Three ..... Will the model require - A Gear Drive ( 's )? .... Here, if its a Kit, you may find the instructions "May or May Not" indicate a need for a Gear Drive, or for the one you pick, to have a certain ratio. And its often best to stay with the motors and drives - the kit recommends, unless your experienced enough to experiment - a little. Here again, hull space inside the model will determine whether you can use a drive - Or Not? But a good rule of thumb, is to always use "Gear Drives" on models, which can be fitted with one to slow them down, save the battery and allow the rc system to operate cooler. Especially in boats that will not travel over 15 miles per hour, as in their real counterparts. Here, the faster a motor turns, the harder it is to control, so you want motors that spin easily = at low speeds, and only use small amounts of current to attain this. # Four ..... How much will the model weight - Once Completed? ..... Here, if its a small model 12 to 18 inches long for example, this can be critical and you may often be working within ranges of the decks, being nearly awash. And if the motors, batteries and other r/c components are to heavy, you risk losing the model. While larger models, may require a few extra pounds of lead weight = Ballast, after everything is installed. Just to get the hull - down to its proper waterline draft.... NOTING = The more weight, the harder it will be to get moving ...... But it will also look - EVEN MORE REALISTIC! # Five ..... How large a Battery, will the model - use? ... The hulls overall size, usually determines this, including what type of battery may be required. For example, a small model, may have only enough space for a typical - 7.2 volt Ni-cad pack, or a pair of them. While a larger model will allow space for bigger batteries, like the "Gel Cell" types, in 6 to 12 volt sizes. Remember to measure the space inside the hull, with the structures - On. That's to see if - pairs of "Nicad Batteries" for example, will fit? Or the hull & structure have enough space for all these items - your installing. And from this, you can also determine the types of Motors and drives needed too, which a kit often recommends the needed items - you should consider or purchase! # Six ..... Just because you have space for something, doesn't mean you have to install - it! .....Here, I mean you don't have to do things, if you don't want too. Just because somebody else did them in their model, you can choose not to do something. But be warned, sometimes - it ruins the model, so be aware of what you may cause. Because I've seen guys add details and so-called "Whistles & Bells" or additional functions to models, then wish they hadn't. Because they found something better, that worked even easier - later. But that's the problem we all run into, in this hobby, so about the time you master scratch building, some outfit will start offering the same thing - at a pretty reasonable cost. OH WELL! ______________________________________________________________________ Batteries!!!! Always Use The Right Type in - Basic Transistor Batteries = 1.5 to 9 volt types.
Naturally, it goes without saying, "If You Buy - Cheap....."You Get Cheap!" So normally I wouldn't even mention this, but some battery brands don't live up to what they claim. Almost all "R/C Systems", recommend the use of "Heavy Duty = Alkaline" batteries, for longer operation. So I ran a few tests of my own and discovered the "BUNNY" = Ever Ready - Energizer's (( Don't As Claimed )) .... "JUST KEEP ON = Going & Going!" In fact, the Copper Top or Duracell did even better. So Duracell batteries, do out last others, under constant use and prolonged periods of several days or months with or without hard use. So whenever you find a sale on Duracell "AA" Batteries, or another size of this brand, buy several packs or a whole case and save yourself - Some Money. I prefer these over any other brand, because I use a lot of AA - AAA - C & D- Size batteries and tons of 9 Volt batteries in a years time. And I like to always keep a large supply - on hand, and so-far, they haven't failed to withstand the rigors of my tests and abuse and nothing has come close to lasting - as long. But I'm always looking for something - better too, so I do try new stuff, just to see what's better, or lasts longerand compare shop - as well ......And So far - I'm sticking with DURACELL.....Nuff said! _________________________________________________________________________________
Lead Acid 6 - 12 Volt Batteries DON'T USE THEM!" .... These batteries are designed for Motorcycles & ATV or Automobiles & Trucks, and Construction & Farm Equipment, all equipped with ventilation. And these batteries need plenty of ventilation to remove their toxic sulfuric acid fumes, which they produce. "Highly Toxic" = In Fact, which destroys metal parts in a model boat - like its electronic system and circuits - for example = REALLY FAST! "And I don't mean after a prolonged use, "I Mean In Minuets!!" WHY - You Ask?..... Because Sulfuric Acid - fumes are confined inside the model = Its Hull & Structures, and quickly soak quickly into the wires and circuits. And that corrodes these r/c components in a matter of moments, which you can't see - till the damage is done. Unseen - as its happening, just one use in a scale model, usually means its to-late to save the radio receiver system. Believe me, "I've had guys laugh - in my face, at this claim, then watched them a few days later, trying to figure out why their radios - quit working? And once the repair bill came in, they wished they'd listened. A hard lesson that I - learned myself, years ago, when I used a small car battery in a model towboat and ended up, destroying the model after it rotted apart after only a couple of runs. That's when I suddenly discovered a green acid - scum, all over my models inner electrical parts. That was, just a few days - later, when I started looking at the wires, circuit boards & switches and everything was already ruined! Sealed - Lead Acid = 6 / 12 Volt Batteries ..... Also designed for use in today's modern automobiles, trucks and farm equipment, including marine usage too. These batteries can still produce some acid fumes, but are only slightly safer versions of the above Regular Lead Acid types. But can be used in small = cramped spaces, but they are still not recommended for model boats, because of their weight and required care extra, just to keep them from shorting - out, or exploding or cause fumes. _________________________________________________________________________________
Ni-Cad Battery - Packs Designed for applications in Models = all types, Cordless Tools, Phones and other general industrial or personal use - applications. These types of batteries provide very "High Current", even at small voltages, for extended short periods of time and can be recharged - many times. Positive Factors .... They Don't produce - Toxic Fumes, They have totally sealed casings and are usually covered with further - protection of plastic shrink wrap to prevent short-outs Produced in wide arrangement of Voltages & Current Ranges and Sizes and properly cared for, can last a couple of years. NICAD Packs, should never be left on a charger that keeps them - fully charged. Unless they are recommended to charged that way, to peak settings. Charger Notes ......The charger = once the battery is fully charged, should be designed to continue charging at a reduced rate, or trickle charge setting. And should be fuse protected in case of battery short-outs, during charging. That's why most guys charge these batteries, only when their going to use them, and leave them drained down to only a few volts almost dead .... to reduce the danger of them causing fires. NOTE...Some insurance companies have been known to raise home owners - insurance rates, if they know your using a lot of these batteries in your hobby! Bad Nicad Characteristics = constant recharging, causes ni-cad battery decay to set - in, meaning the pack will provide less & less run time, indicating it needs replacement. Under heavy use, these batteries get - Very Hot, and have been known to Reverse Polarity and explode. Never run these batteries = Completely Down, Or Dead. And they have also been known to "Short Out & Explode or Sometimes = Catch Fire!" The best type of Nicad = Chargers Monitor the battery constantly, and once fully charged, slow the voltage and current down to a small trickle charge rate or turns the charger - Completely Off! Always check Nicad's periodically (( Most common size = 1200 Milliamp. 7.2 volt - Packs, suitable for small model cars & boats or planes with limited space. When Purchasing, always choose the best brands ( High Capacity Types ), to reduce overall costs of replacement under use. Sources = Tower Hobbies, R/C Hobby Shops. _________________________________________________________________________________
Gel Cell - Storage Batteries - THE BEST! Used for Back-up Power in many business applications, that require "High Current" from small storage batteries for short periods of time. Positive factors - totally sealed = "No Toxic Fumes", built with a similar case enclosure to "Lead Acid" type batteries. Biggest Application Use = Computer's, used as battery - back-ups in 110 / 12 volt emergency DC to AC Converter Power Supplies. Used in Emergency Lighting Systems, and as back-up battery systems for Fire & Smoke and also Burglar Alarms. Designed for heavy use, over long periods and last for many years with little or no effects on output, due to age, usage, or Battery Position = Upside Down or laid on their side! When Purchasing, slightly higher in costs, compared to high quality = Lead Acid types. Found in Current / Voltage ranges matching or exceeding most all - Lead Acid batteries. Easily recharged - many times, with no effects, even if not immediately recharged. But work best, when kept at peak - fully charge, by leaving them on their own special dc charger systems, until needed. Note... One of the safest batteries - so far developed. But takes its own special type of charger, recharges them - Fast, then drops to a trickle rate, to keep them at Peak Condition. Bad Characteristic = "If you totally discharge them ( Run The Battery Completely = Dead ), Its Ruined! I've purchased these batteries in many sizes, shapes and voltage ranges. from 3 to 6 & 12 volts and prefer them, over anything else. Can be purchased from varied sources = Hobby Shops, Security Alarm & Safety Lighting - Dealerships and some Automotive Parts Stores. Come in various voltage sizes and current ranges, and can be specially designed for some special applications. Can be built almost, as small as some "Nicad Packs", but won't produce as much current, as small Ni-cad packs, but doesn't produce the dangers of exploding - unlike Ni-cad's can do sometimes..
I'll Add More - Later, so check back Often! _______________________________________________________________
Last Updated On 06/30/07
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