2017-11-09 UteRC Meeting

Gerhard Roos opened the Show & Tell portion of the meeting with a brief review of the first two parts of his presentation on Electric Propulsion. He then proceeded with Part 3 which dealt with RC Brushless Outrunner motors.

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Part 3 of Gerhard's Electric Propulsion Presentation began with a slide showing basic brushless motor electrical relationships.

The brushless motors internal resistance is important to know. In order to show how that resistance could be calculated, Gerhard rigged up a typical brushless motor with a flat blade (low load) as a prop so the motor's voltage and current at high RPM could be measured. The bright light was necessary to get a reading on an optical tachometer.

Here the flat-blade prop has been replaced with an appropriate prop to provide a full load for the motor. Again the voltage, current, and RPM were measured.

From those measurements, with the help of Tony Naef keeping track of the numbers, and the formulae in the first slide, the resistance of the motor was determined.

All of that was the hard way to make that determination. The easy way is to use the on-line calculator available at the CastleCreations web site.

Here is a screen showing all the calculations that can be provided from the basic information on any combination of motor, battery, ESC, and prop in the vast CastleCreations data-base.

Utah State Aeromodelers (USA) President, Roger Kramer, shows off a beautiful prize winning built-up control line model of the Japanese Tony fighter, one of a pair he and Gordon Delany built at the same time.

Jim Rhoades of USA, shows his Apteryx, a control line stunt plane designed by Jerry Worth, another fine model with lots of contest performances under its belt.

Whitey White shows off his new JR XG14E Tx. It has a full 14 unshared channels, comes with a 7-channel RG712BX Rx, and a foam lined metal carrying case. http://www.jramericas.com/234723/JRP00664/?pcat=2

Doug Dorton describes how he keeps CA glue in the freezer (the CA stays liquid) to extend its life. Doug uses a pipette to draw small amounts to use at the workbench from an intermediate bottle which is also kept in the freezer. While demonstrating how to handle the CA from the original bottle to the dispensing bottle to the pipette, all the while juggling the open CA bottles and pipette in one hand and gesturing with the other, everyone was sure he was going to glue his fingers together or worse. Then OOPS! Much to Mike Passey's surprise who was sitting in the front row, Doug accidentally squirted CA from the pipette onto Mike's clothing. When the shock wore off, Doug explained it was of no concern, he was only using water in the bottles for the demonstration!

A bottle of cyanoacrylate (CA) super glue, a one-ounce CA-proof Nalgene bottle available from REI, and a pipette from West Valley Hobbies. The extra bottle and pipette are used by Doug to extend the useful life of the CA.

The technique is to reduce the CA's exposure to airborne moisture (which causes it to cure) in the original bottle and to further reduce the curing response by keeping the CA cold. He opens the original bottle only infrequently to put some in an intermediate bottle. Both bottles when capped are quickly returned to the freezer. He only opens the intermediate bottle to fill a pipette from which the CA will remain usable for several hours at the workbench. The intermediate bottle is capped and quickly returned to the freezer as soon as the pipette is loaded.

In this two-stage isolation method, most of the original CA is never exposed unnecessarily to fresh air and is kept cold to reduce any curing response to that air. Doug finds this method extends the life of the CA many months over a bottle that lasts only a month if used directly for gluing.

If the CA clogs the pipette, its end can be snipped off or the entire pipette just discarded thus wasting only a small amount of CA.

For more information about CA and how it works, see


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