Spirit of Sam Power System Decoded

I’ve had a number of inquiries for an alternate Spirit of Sam power system. I worked out a system for Phil Pearce. He’s had a chance to do some run time and amp draw tests. Here are his comments thus far.

Phil Pearce Spirit of Sam Afterburner Setup
Phil Pearce Spirit of Sam Afterburner Setup

Good morning Dave. Here are a few picture of the little 5 oz Wren, built for the Spirit Of Sam event at the Society of Antique Modelers events. The rules call for the power battery be a single 160 mah lipo. The task is endurance, using the second best flight time of two flights. The motor you provided is an “Afterburner High Performance Brushless Motor. The number on the info. sheet says: MR-012-030-4000-1.5 I ended up using a GWS 9/7 prop. As the picture shows, the rear lipo is for radio power. The BEC is disabled. My procedure for maximum flight time is to hand launch with full power of about 1.5 amp draw, than establish a slight climb at minimal power of probably about 1 amp. I level out at about 200 feet and only use enough power to maintain altitude while looking for signs of lift. The motor will start slowing down at somewhere between 8 and 10 minutes with no thermal help. I must immediately start a landing approach while the prop is still spinning and plan on landing in about 15 seconds. Unfortunately a folding prop is not allowed. The drag on a stopped motor is dramatic on this small light model. I hope this is what you wanted. Thanks again for you help. Regards, Phil

P.S. If you have any advice on another prop, please advise. PP

Phil Pearce and his 5 ounce Wren Spirit of Sam competition model.
Phil Pearce and his 5 ounce Wren Spirit of Sam competition model.

Equipment is a 4000kv 12mm Afterburner with 1.5mm shaft. Running in a GWS LPS gearbox 4.8:1 ratio.

close up of gws lps gearbox with afterburner motor installed.
Close up of GWS LPS gearbox with Afterburner motor installed.

Links to parts supplied by Radical RC:
GWS LPS 5:1 “B” Pinion: GWGER002
GWS LPS 5:1 “B” Blue Spur Gear: GWLPS4B
GWS LPS 5:1 Blue Spur Gear: GWLPS4B
GWS LPS Ball Bearing Set: GWLPS2A
GWS LPS Gearbox Shaft: GWLPS6A
GWS LPS Gearbox Frame: GWLPS5A
Afterburner Motor (Take 1.5mm shaft option): MR-012-030-4000
Screws for AFterburner Motor: MR-SCREW-080-125-2
All parts needed are contained in the system linked below. Replace motor with 12mm Brushless Afterburner. Note, If you buy the brushed motor system to get all the parts, consider buying a pinion. A puller is needed to remove one from the included brushed motor and it can be ticklish. Some skill, minor tools and a drill press (or press of some sort) are required to install a pinion on LPS RXC OR RLC Drive take “B” gear ratio option: GWLPS-RXC or GWLPS-RLC
GWS LPS Gearbox Frame: GWLPS5A

side view motor and rx battery spirit of sam geared brushless power system
Side view motor and RX battery.

Note, the point of this blog post is to record what we did in a way that will last longer than my memory. If you want to do the same thing, all the links are provided. 😉

Some thoughts that I have based on what I know thus far: An “A” ratio (less reduction) could be considered in order to reduce the pitch or perhaps the disk diameter. That might lead to a 9-4.7 or 9-5 or 8-6 being optimal. I’m tickled by the idea of a 4 or 5″ high rpm setup in order to try and get the model to glide with a stopped prop longer than Phil reports with 9″ props. Not being experienced in the competition, my thoughts might be completely off base here. The higher KV Afterburner motor should be avoided because the higher no-load current. Although it might be more efficient at wide open throttle, the minimum no-load current would kill you in cruise (partial throttle flight). So, the lesson is stick to the 4000kv motor. Anything you can do in this contest to utilize a low non-load current motor would probably be an advantage over most motors with higher no-load currents. The no-load current rating is one of the fixed parameters (motor constants) of every motor. Explaining it fully is beyond the scope of this article.


Reluctance Motor In The News

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A reluctance motor is a different breed. It is a form of a brushless motor. However, the brushless motors we use in the RC hobby, the number of stater teeth (each iron segment that is wound with copper wire) will always be 3,6,9,12…; A number always divisable by 3. Magnets will always number 2 or 3,6,9,12 some number divisable by 3. Each magnet is considered a pole. So, a 6 magnet motor is called a 6 pole motor.

The cause of investment into the development of Reluctance motors is communist China produces most of the materials described as rare earth that are used to produce modern high power magnets. China has limited the export of these materials and magnets in order to help China monopolize permanent magnet motor production. The reluctance motor does not need any of these materials and is hence much cheaper to manufacture. Also our ability to produce motors in the USA would not be hindered by the unholy alliance between government and business as is so common in socialist/communist states. Regardless of the type of government, anytime governments stick their fingers into business, supply problems and shortages ensue. Perhaps these developments will stifle the anti-capitalists this time. Sustained monopoly’s are only possible when governments collude with business (or nationalize industry). It’s an interesting side note to mention there have never been any long lived monopoly’s that were not created and maintained by government regulation.

Clean Tech Open 2012 Winner HEVT

According to HEVT the spot price for neodymium increased from $19 a pound in 2010 to $129 a pound in 2011.

HEVT Hybrid Electric Vehicle Technologies

Many times technologies are developed and press releases fly all over the internet. These products offer great promise yet often the creators are just looking for somebody to buy the technology and when they are unsuccessful (most of the time) we never see the great new products. This development strikes a different tone with me, I feel this very well could be the beginning of a new paradigm shift in motor technology. Lets just hope it makes it down to us modelers sooner rather than later.

Gigaom Story: An Electric Motor That’s Ditched The Rare Earth Materials

Reluctant Hero’s (The Economist)

Learn more about Switched and Synchronous variations here: Reluctance Motor Wiki

Many photo’s and drawings: Google Images Reluctance Motors


“Hi, my name is Nick. I’m from Prop Buster’s R/C club in Richmond, IN. I recently bought a brushless motor from you for my GWS P-51 Mustang. Thanks to your help. My plane flies a lot better than it ever has before
(in spite of my poor piloting skills).

The software you used to determine the proper set up for my airplane was very helpful…thanks for all your help. I look forward to doing more business with you in the future.

Nick Edward Jones”

October 2004