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    Hobby RC: Brushless Motor Conversion Basics

    Most modern, electric-powered RC airplanes utilize brushless motors for propulsion. And why not? Brushless motors are much more efficient than their brushed cousins (not to mention lighter and sometimes even less expensive). Similarly, airplane models that were designed to use brushed motors can enjoy a huge boost in performance with an upgrade to brushless power.

    Some brushed-to-brushless upgrade projects are just a simple matter of swapping out the relevant components (motor, Electronic Speed Control (ESC), propeller). Others require a bit more planning and modification. My most recent brushless upgrade is a good example of the more-complex type. I'll show you the hurdles I encountered during this project and how I cleared them.

    The Airplane

    The recipient of this power system transplant is a small electric sailplane called the Skimmer 400. Kits for this balsa airplane were popular during the late 1990s and early 2000s. Like other electric-powered models of that era, the Skimmer 400 was designed around the brushed "can" motors and NiCad batteries of the day. There was never a surplus of power with that gear. So models that performed well, did so by virtue of excellent airframe design. I've found that these types of model airplanes adapt particularly well to brushless upgrades.

    My Skimmer appears to have led a hard-knock life. I bought the airframe in very-used condition at a recent RC event. Despite model's wrinkled and tattered covering, the balsa structure seemed to be built relatively well and I did not notice any obvious crash damage. It may be an ugly duckling, but the asking price was only $5. What was I supposed to do…just leave it there?

    This old Skimmer 400 looks rough, but it performs really well with a modern brushless motor.

    As originally designed, the Skimmer 400 was powered with a Speed 400 brushed motor spinning a 6-inch propeller. "Speed 400" is just an RC-centric term for the generic Mabuchi RS-380 motor that is used in all types of different applications around the world. It has a diameter of 28mm (1.1"), is 38mm (1.5") long, and weighs 65 grams (2.3 ounces). The intended battery pack for the Skimmer 400 consists of seven 2/3A-sized NiCad cells of 600mAh capacity. Altogether, this system produced about 60-80 watts of power…enough to fly the Skimmer 400 in a leisurely fashion.

    Model Behavior: Diorama Water Effects!

    Kayte and Norm take miniature vehicles from past Model Behavior projects and augment them with a water base. Using Smooth-On Crystal Clear to make a base, we experiment with sculpting water effects using silicone caulking and Smooth-On's Sil-Poxy.

    Modeling Achilles' Sword for 3D Printing!

    This week, Darrell walks us through his process for 3D modeling Achilles' sword inspired by the prop from the movie Troy. Using photo reference of the prop, Darrell explains how he creates a faithful replica that retains all the characteristics of the original!

    Model Behavior: Let's Talk Paintbrushes!

    We got back to the basics with an overview of the various kinds of paintbrushes you can use for modelmaking and painting props. Bill brings a selection of brushes and we demo each type, showing the techniques that make the best use for each. What are your favorite brushes to use for your projects?

    How To Make Flying Holiday Decorations

    At this time of year, I try to keep a few simple projects in my back pocket for when my kids act bored during their holiday school break. I like things that fly, so my projects tend to lean that way as well. For example, I previously figured out how to repurpose Christmas Cards as indoor gliders. My latest flying holiday craft is just as much fun to make and to fly.

    For this year's project, I dusted off one of my indoor mini-quads and gave it a holiday makeover. It is now a flying Christmas decoration! I'd be willing to bet that many of you have a mini-quad stashed away somewhere. The crafty, decorative parts can be made with common household items. So you probably have everything you need. Here's how I did it.

    A Quick Fix

    The quad I chose is the Heli-Max 1SQ. This particular quad is no longer available. But that's not an issue here. Just about any mini-quad you have on hand should work just fine.

    I had not flown the 1SQ in quite some time. The airframe was in good shape, but I quickly discovered that neither of my batteries for it would take a charge. This quad is designed to be flown with a single 250mAh LiPo cell. While I didn't have any direct replacements for the dead batteries, I did find an alternate that works great.

    My first step in this project was to repair the long-ignored mini-quad by replacing the stock battery (top) and connector with new parts.

    The new battery is a 260mAh LiHV cell, which is basically a LiPo battery that charges to a slightly higher voltage (4.35v vs 4.2v). Despite the drastically different form factor of the newer cell, it fit well in the quad's battery compartment. I only had to apply a small patch of thin foam padding to give the battery a snug friction fit.

    My final hurdle was to reconcile the mismatch of battery connectors between my new power source and the quad. The LiHV cell uses a JST-PH 2.0 connector, which has become common for micro-RC applications. I had to snip off the 1SQ's stock battery connector and replace it with a matching JST plug on about 1" (25mm) of additional wire.

    Model Behavior: Hairspray Paint Chipping

    For this week's project, Kayte and Norm experiment with a modelmaking technique using off-the-shelf hairspray as a way to create realistic paint chipping. We apply this to a few test pieces and then to a garage kit from Machination Studio. We couldn't be happier with the results!

    Modeling a Judge Dredd Helmet for 3D Printing!

    This week, Darrell walks us through his process for 3D modeling a helmet replica using photo reference. We've shown how he preps models for 3D printing, but much of the work happens on the computer screen. Follow along as Darrell explains how he approaches creating digital forms to exacting detail.

    Hobby RC: Upgrading a Third Hand Tool

    I'm sure that most of us have some variation of a Third Hand (aka Helping Hand) in our workshop. If you're not familiar with this particular tool, it's basically a pair of alligator clips that are attached to articulating arms with a weighted base. The mechanical "hands" will securely hold whatever small widget you're working on, while leaving your actuals hands free to do the work. The utility of these simple tools for outweighs their meager cost (usually $5-$10).

    I have several Third Hands that I employ for a variety of tasks. The one I use most often is at my soldering station. I use it to hold wires, connectors, circuit boards, motors, or whatever else I need to solder. While I love this tool, I do have to concede that it has limitations. You can certainly buy nicer and more elaborate Third Hand tools. But there is often a significant bump in price for the upgrade. Second-tier units typically sell in the $30-$50 range.

    There's nothing wrong with spending $50 on a high-quality tool that fits your needs. The problem was that I didn't see any off-the-shelf models that had everything I wanted for soldering tasks. So I decided to try upgrading my base model Third Hand. This was actually my second round of modifying the Third Hand I use for soldering. I previously adapted an aluminum heatsink that makes it easier to solder battery connectors.

    Model Behavior: Groot in Carbonite Garage Kit!

    Time to put together another garage kit! Bill brings a kit featuring a pretty sweet mash-up: baby Groot at 1:1 scale frozen in carbonite. We use this kit as an opportunity to practice some oil washes, as well as install a lighting kit. This was the project that put us in contact with VoodoFX!

    Model Behavior: Making a Set for Toy Photography

    Kayte and Norm work with styrene this week to build out a backdrop for sixth-scale toy photography. Specifically, we're going to making a photo-ready approximation of an Imperial wall from Star Wars for use with a K-2SO figure. Follow along as we cut stencils out by hand and then also experiment with the Cricut vinyl cutter to automate some of the processes!

    Hobby RC: Analyzing LiPo Battery Discharge Rates

    The Lithium-Polymer (LiPo) batteries that we use in RC vehicles have evolved tremendously since they were first introduced to the hobby about 15 years ago. Most of that progress can be traced though ever-higher rapid discharge capabilities. Early users had to link multiple cells in parallel just to have enough juice to get airborne. Now there are LiPo cells that can safely deliver hundreds of amps! But is there a downside to using the latest high-discharge lithium batteries? In this article, I'll cover some LiPo basics and then analyze the pros and cons of using rapid-discharge cells.

    Understanding the LiPo Lingo

    I wrote an article a few years ago that covered the basics of LiPo batteries. You may want to review it if you're totally new to the LiPo world. But I'll be recycling some of the high points from that piece into this article as well.

    When talking about a LiPo, the primary characteristics to understand are the battery's voltage and capacity. This is typically noted in a shorthand such as "4S-2200". "4S" denotes that the battery has four cells in series. The nominal voltage of each cell is 3.7 volts (4.2v fully-charged), so the total pack voltage is: 4 cells x 3.7v = 14.8v.

    The second number denotes the capacity of the battery in milliamp-hours (mAh). A fully-charged 2200mAh pack is rated to provide a current of 2200 milliamps (2.2 amps) for one hour before it is completely discharged. This capacity value is totally independent of how many cells are in series. In simple terms, the capacity value allows you to estimate how long a battery will provide useful power in a given application. In practical terms for RC use, the capacity rating is typically only helpful for rough comparisons of different batteries. i.e. a 2S-5000 battery will provide about double the run time of a 2S-2500 LiPo in the same RC car.

    Shop Tip: Collect Material Samples for Your Workshop

    Sean shares his collection of material samples that he uses for his workspace and Tested's workshop. These samples become invaluable when figuring out what kind of resins to use for casting, material for laser cutting, and even fabric for cut and sew work. What kind of material samples do you have in your shop?

    Model Behavior: Acrylic vs. Oil Washes

    Bill and Norm experiment with different kinds of paint washes for model figurines. We examine the differences in application and results between using a water-based acrylic washe and an oil wash for weathering. What kind of paint wash do you use for your projects?

    Custom Model Paint Racks for the Tested Workshop!

    Sean's latest project with our Universal Laser Systems laser cutter is an improvement to our workshop's model paint storage. Sean designs a stackable storage system that can work with different sized bottles, properly labeled. We assemble one of these storage racks and show off the design details.

    Model Behavior: Vinyl-Cutting Figure Decals

    We're back with more episodes of Model Behavior! Bill comes by the studio to help us experiment with a new vinyl cutter, the Cricut Maker. While we cut tiny decals to deck out a sixth-scale figure, we chat about the uses of vinyl decals and stencils for propmaking and modelmaking, and Bill gives some great advice about how to make the most out of the material.

    Model Behavior: Making Custom Wood Blaster Grips!

    Bill's back for another Fusion 360 tutorial in our shop! This week, we step up to modeling more complex shapes with the making of wooden grips for the Dave Goldberg snub-nosed Blade Runner blaster prop. And these grips are going to be milled in a CNC machine instead of 3D-printed!

    How to Make a Laser-Cut Prop Stand!

    Inspired by a Blade Runner blaster stand that came with a kit, Bill Doran walks us through the simple process of designing and laser-cutting an acrylic stand for your hand props. In this case, a lightsaber! We take our quick design to our shop's Universal Laser Systems laser cutter and piece together a stand in less than 10 minutes.