Motocalc Version 5

Steve Horney takes a look at the latest version of MotoCalc.

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  • Product: Electric R/C aircraft performance simulation software
  • Platforms: IBM compatible computers using Windows 3.1, Windows 3.11, Windows 95, Windows 98, and Windows NT operating systems
  • Price: Free 30 day trial (downloaded from the web at, $35.00 registration fee ($45.00 Canadian). If ordering a disk, there is an additional $7.00 shipping and handling fee ($9.00 Canadian)
  • Manufacturer: Capable Computing, Inc. 8150 Concession 5, R.R.#3, Moorefield, Ontario, CANADA N0G 2K0


Introductory Comments

MotoCalc is an impressive piece of software designed to allow the electric modeler to simulate almost any parameter of electric flight. I was very pleased to be offered the chance to review this piece of software; I’ve heard of it’s capabilities and I wanted to try it out for myself.  I know - it can be downloaded for a free trial period. Like so many other things, though, I just never got around to it!  The trial version is actually the full-blown software - it just has an expiration date 30 days from the time you load it. Registering the software provides the "key" that removes the time limit.

MotoCalc has a few novel features that make it ideal for the electric flyer who loves to experiment. Not only can you draw from a database of motors or add a known motor, but you can even use the motor design option to design your own! This software also allows you to graph almost any parameter against any other parameter. I’ll get into these features in more depth later in this review.


Basic Product Description

I see no point in rewriting the basic description of MotoCalc, so below is the manufacturer’s description of the product:

Manufacturer's Description

MotoCalc is a program for predicting the performance of an electric model aircraft power system, based on the characteristics of the motor, battery, gearbox, propeller or ducted fan, and speed control. You can specify a range for the number of cells, gear ratio, propeller diameter, and propeller pitch, and MotoCalc will produce a table of predictions for each combination.

MotoCalc will predict current, voltage at the motor terminals, input power, output power, power loss, motor efficiency, motor RPM, power-loading, system efficiency, propeller or fan RPM, static thrust, pitch speed, and run time. By producing a table of predictions, MotoCalc lets you determine the optimum propeller size and/or gear ratio for your particular application.

MotoCalc can also do an in-flight analysis for a particular combination of components, predicting lift, drag, current, voltage, power, efficiency, RPM, thrust, pitch speed, and run time at various flight speeds. It will also predict stall speed, hands-off level flight speed, maximum level flight speed, rate of climb, and power-off rate of sink.

MotoCalc's graphing facility can plot any two parameters against any other (for example, lift and drag vs. airspeed).

If you have particular requirements, such as a minimum run time, maximum current, or maximum power loss (which is dissipated as heat), you can use MotoCalc's filter facility to filter out the unacceptable combinations.

To reduce the amount of information you have to deal with, MotoCalc comes with a database of motors, cell types, gearboxes and propellers, speed controls, and filters. For example, there are over 250 motors in the motor database (including the Astro, Aveox, Graupner, Keller, Kontronik, MaxCim, and Robbe lines), and 50 different cell types (the entire Sanyo and SR lines) in the cell database.

If the motor you are using is not included in the database, MotoCalc will help you figure it out from test data, catalog information, or from the specs of another similar motor. And if you don't know the aerodynamic characteristics of your plane, MotoCalc's drag and lift coefficient estimator will make short work of determining them.



In order to demonstrate MotoCalc, let me use one of my planes as an example and go through each of the entry and prediction options available with this software. I am currently flying my SuperMutt (Scat Cat fuselage, ElectroStreak tailfeathers, 54 inch scratch-built wing with Eppler 193 airfoil) on an Aveox 1412/3y with an L160 controller, 10 or 12 1700 mah cells, and an APC 11-8 or 10-8 prop. I am looking at the possibility of converting this plane into a twin (called the "TwinMutt") with a pair of Astro 15’s on 10 cells wired in parallel using APC 7-6 props. This program should be a great way to tell me what the potential results of this conversion would be. I can also compare the results with the known flight characteristics of this plane. Another plane I want to look at (although I won’t be able to show the tables for both planes in this review) is a potential sailplane combination. I recently picked up an Aveox F7LMR motor, L60 controller, and Graupner 14x9.5 folding prop. I want to use this with my Great Planes Spirit 100 (yet to be built) on 7 cells for Sport Sailplane events and Class A LMR events, and on 10 cells using 13x7 blades for class B LMR events. Someday I would like to pick up an F5B style sailplane, but that will have to wait! I’ll use MotoCalc to check the potential of these sailplane combinations. One of the more beneficial features of this software is a sink-rate calculation, which should come in very handy for sailplane predictions.

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Main Data Screen

This picture shows the main screen with the data for my TwinMutt. As you can see, there are 6 regions requiring input data from the user. Much of the data can be input from the included data bases, but for the more adventurous MotoCalc offers a wide range of customization options. I’ll go over each section individually. I should point out the Options button at the top left of the main screen. Clicking on Options will open up a window which allows you to select between English and Metric units, specify the elevation at which you would like the information to be calculated, printing style, and which columns of data you would like to have presented.


Using the Program

Motor Section

The first step in modeling my Twin Mutt is to select a motor.

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The Motor Section of the main Motocalc screen

As you can see from the above screenshot, I chose the Astro Cobalt 15 motor for my Twin Mutt. Choosing the motor was as simple as going to the motor database and selecting from the extensive list of motors that comes with the program.  The parameters are automatically entered into the calculations.

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The Motor Browser

If I wanted to input a motor not included in the database, there are a few options available: use the Motor Designer to create a new motor based on an already defined motor, create motor parameters from real-world test data, or input motor parameters into the catalog.

Selecting the "Design" button brings up the Motor Designer:

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The Motor Designer

As you can see from the picture, the user has the option of building a custom motor based on an existing motor in the database. One can start with a motor that is already in the database and vary the number of winds and the wire gauge.  MotoCalc will calculate the new motor parameters.

Another option for specifying a different motor is available by selecting the Tests button. This provides a window for test data input, as shown in the picture. If you have the test data from free running and loaded tests of a motor, you can use this window to import the data into MotoCalc.

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Defining a motor using test data.

Finally, a third option for entering a motor not included in the database is found by clicking on the Catalog button. This brings up the Catalog Data Input window as shown below. If sufficient information is available on a motor from a catalog, you can inset the data into this window and MotoCalc will calculate the other necessary parameters.

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Defining a motor using motor parameters.

I didn’t experiment with the various motor option windows, since the motors I use are all included in the data base, but it looks like these options are great features to allow expansion of the program in the future.


Battery Section

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Battery information in the main Motocalc screen

This section allows the user to enter the battery type to be used the aircraft under consideration, along with the number of cells to be used in the comparison computations. Most of the Sanyo and SR lines of cells are represented in the cell data base. As you can see, I used 1700SCR’s for my TwinMutt, and asked MotoCalc to look at cell counts from 10 to 12.

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The Cell Browser


Filter Section

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The Filter section of the main Motocalc screen

The Filter section of MotoCalc has the unique function of keeping the results somewhat realistic. You can easily take a computer program and determine that something like a geared sp400 on 20 cells and 40 amps would fly your 1/4 scale Cub just fine, but that ignores a critical component: Reality! Your sp400 motor would be smoke almost before the prop began to spin. This section allows the user to select a motor comparable to the one being used in his calculations to keep the current at a reasonable level. Shown here is the filter database, from which I selected the Astro 15 (which put a 25 amp motor current limit on the combinations the program would analyze).

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The Filter Browser

As with all of the data browsers in Motocalc, the user can sort the data by a wide range of possibilities. In this case, I could sort data by description, max. current, minimum efficiency, etc.  A nice feature.


Drive System Section

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The Drive System section of the main Motocalc screen

As shown in this picture, the Drive System section of MotoCalc allows the user to input the prop size, number of props, number of blades, and how the motors are wired. You can even tell the software whether you are using ducted fans or props. This should be a very popular feature, with the number of ducted fan models that seem to be proliferating. I set up my run with APC 7 inch props and I wanted to check combinations from a 5 inch pitch to a 7 inch pitch. I also told the software that I had two motors wired in parallel. I inserted my data manually (actually, I modified an APC prop entry so that I could have the proper propeller coefficient), but you can also use the data base if it contains the information you are looking for. The database is shown in this picture:

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The Propeller Drive System Browser


Speed Control Section

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The Speed Control Section

The speed control section allows the user to select from a variety of popular speed controls and install this data (resistance and max. current) into the airplane system calculations. The max. current box does not have to be filled in, but if a value is input in this location it will act as a filter to prevent the calculation of combinations that exceed this current level. One novel feature is the option of designating your esc as a high-rate unit by checking the high-rate box, or designating it as a frame-rate unit by leaving the box blank. This option affects the part-throttle efficiency calculations. I would probably use either my Robbe 730 esc or my New Creations 60 amp controller, but neither of these controllers were in the data base. Rather than create my own listing, I simply used the Castle Creations Griffin 50, assuming the parameters were pretty close. Here is a picture of the speed control database:

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The Speed Control Browser


Airframe Section

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The Airframe Section

MotoCalc users specify the characteristics of their chosen airframe in this section. You can either select a plane from the database (as shown below) or you can insert your own parameters. I chose to insert my own data, since I was analyzing a custom airplane. In addition to the usual information about wing area, wing span, and weight, MotoCalc includes a drag estimator to help establish the performance of the airplane. Clicking on the Coeff. button brings up the drag estimator. I like the fact that you can very conveniently simulate your airfoil shape and characteristics, as well as describing the other characteristics of your airframe with the drag estimator. I should note one thing about the airframe section data: be sure you insert your airframe weight WITHOUT MOTOR , SPEED CONTROL, AND BATTERIES (but do include the prop and gearbox), or you will get a pretty porky aircraft!

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Selecting a plane from the Airframe Browser

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The Drag Estimator screen


Analysis Tools

Static Analysis

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MotoCalc has several excellent tools to help the modeler understand and refine the particular aircraft he is modeling. This Static Analysis chart comes up when the Compute button at the bottom of the main screen is clicked. On this chart you’ll see all the combinations of cell count, prop sizes, and gear ratios that you’ve selected which fall within the range of the filter (or other component limits). The chart then carries across to show a whole range of data, including such things as current, voltage, efficiency, thrust, pitch speed, rpm, etc. Another useful piece of information is the red coding of stalled prop combinations. Incidentally, you may notice in the upper right corner of this window is the comment that the data is for sea level conditions. You can input the elevation level of your field by clicking on the options window of the main screen - a very useful feature for many fliers who live at higher elevations. The material presented on this chart makes a good starting point for comparing various possible combinations.


Flight Analysis

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From the Static Analysis chart, highlight one of the rows of data and click on the In-Flight button. The In-Flight Analysis chart, shown here, comes up. This chart shows much of the same data as the previous Static Analysis chart, only the data presented here is for one combination of components at various airspeeds. A slider bar allows you to vary the throttle setting and see the impact on the flight performance. As an added bonus, the chart is color coded to show the user where the prop is stalled, where the plane is on the edge of a stall, and where the speed exceeds the prop pitch speed. This is very useful information, especially for ducted fans or racers with small props, where it would be useful to know if you need to bungee launch or not. It also gives you a realistic picture of the top speed of your plane. It’s very easy to look at pitch speed and assume your plane will go that fast - usually that isn’t the case! If you look in the description section at the top of this chart, you’ll find a lot of useful information. The bottom line gives information such as watt/lb., climb rate, and sink rate. I learned from this simulation that going from 7x5 props to 7x6 props increased my climb from 1021 ft/min. to 1266 ft./min., and my top speed from 53 mph to 59 mph at the cost of 4 amps (static amp draw).

According to runs I made with simulations of my (soon to be) electrified Spirit 100 glider, it should climb at 1242 ft/min. at 61.8 deg., with a sink rate of -103 ft./min. at -4.2 deg., a stall speed of 18 mph, and a level flight speed of 24 mph (using 10 1700 mah cells, F7LMR motor, and a 13-7 folding prop). It will be interesting to compare this data with other sailplanes to see the competition potential of this project.


Graphical Ability

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Finally, I’ve included a copy of a graph, in this case comparing prop rpm, airspeed, and efficiency from one combination in the In-Flight Analysis. MotoCalc has considerable graphing ability - the user can plot almost any data item against any other item. It’s very beneficial to see the trends plotted out like this - it gives a good overall feel for the most efficient region of your aircraft’s flight envelope.


Personal Impressions

I really like MotoCalc! This is a powerful electric flight simulation program that gives the user a lot of options (lots of fun for engineers, like me!) and a lot of value for the money. If you want to thoroughly analyze your plane’s flight characteristics (or a design that you’re considering) before you commit it to the air, MotoCalc is a very worthwhile tool to own. It just might save you quite a bit of money over the potentially lengthy and expensive process of trial and error experimentation!

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