Electric motor data
Q615: Bob, I know you often talk about electric motor vendors that fail to supply the necessary technical data on their products. Can you specifically recommend an electric motor supplier that provides what you consider the required data?
A615: My usual source of motors is now unavailable, so I went looking. I really lucked out by finding a company known as Innov8tive Designs, based in California. It carries a large selection of brushless outrunner motors at attractive prices. I know I sound like a salesman, but I ordered several motors and I can tell you from hands-on experience that the quality and the prices are good.
The best part of this company and its Cobra product line is the technical data it supplies for each motor. One of the photos in this column shows the smallest motor in the line. It is rated at 45 watts and 6 amps maximum and costs $17.
The website provides a motor specifications box for each motor, which you can see in the photo. It states: “Click here for Cobra C-2202/70 Propeller Data Chart.” When you do that, you get a Cobra Motor Propeller Data box (shown in the photo). In my case, data was supplied for nine propeller sizes, with information about the motor current and power input in watts. With data like this, you can’t miss.
Also of note, Innov8tive Designs supplies companion brushless ESCs at good prices. The website is listed in the “Sources” section.
Substituting LiPo Batteries
Q616: I’m starting to hear more about modelers replacing their old Ni-Cd and NiMH transmitter battery packs and substituting LiPo batteries. Is this okay? Can I damage my transmitter? How do manufacturers feel about this?
A616: I think the RC manufacturers are gradually coming around to using LiPo battery packs in RC transmitters. The biggest concern is that the voltage of two- or three-cell LiPo packs can be higher than a comparable Ni-Cd or NiMH pack. The question is whether the transmitter can take the higher voltage.
Most RC transmitters have used eight-cell packs with a nominal 12 volts for years. A two-cell LiPo pack would have a nominal 7.4 volts, which would be too low. A three-cell pack can have a nominal 11.1 volts and this could
Radical RC supplies replacement LiPo battery packs for many RC transmitters. A three-cell 2,800 mAh pack (lower pack in photo) replaced an eight-cell 600 mAh NiCd pack (above). This LiPo pack came with the mating connector for an Airtronics RDS8000 transmitter.
reach 12 volts when fully charged. The best bet when trying to switch batteries is to contact the manufacturer of your specific transmitter.
In my case, my Airtronics RDS8000 transmitter needed a new battery. The Airtronics technical service representative indicated the following to me: “The RDS8000 transmitter is designed to work on eight 1.5-volt AA (Ni-Cd or NiMH) batteries, e.g. 12 volts. Therefore it is fine operating on a three-cell LiPo pack, which also is in the 12-volt range.”
Knowing this, I went looking for a three-cell pack. I centered on Dave Thacker at Radical RC. Dave had a three-cell pack with a rated capacity of 2,800 mAh. I was cautioned by the Airtronics people that the polarity on the RDS8000 transmitter is opposite of most brands.
With Airtronics, the outer pin is positive (red wire), while the center pin is negative (black wire). Radical
RC took this into account and supplied the pack for the Airtronics RDS8000 transmitter with the proper polarity. The part number is RRC3S2800TX1C (with Airtronics polarity). Its price is $33 plus $3 shipping in the US.
When going to LiPo batteries for your transmitter, you must remove the battery pack every time to recharge.
Star Plugs
Q617: I prefer to use the popular Deans Ultra plugs for my electric-power wiring connections. I use them for higher current-drain applications. But there has always been a problem with this connector. It takes a lot of effort to separate the mating halves. In several instances I’ve broken a wire off of the pin connection.
I’ve seen several schemes to help separate these connectors, but none were that practical. I’ve seen advertisements for a product known as the Star Plug. Have you tried it? What can you tell me about it?
A617: My feeling has always been that any motor current above 8 to 10 amps deserves a heavy-duty connector. The time-honored Anderson Power Pole, also known as Sermos, does a good job, but when you try to use very heavy-gauge wire, you find it difficult to get the wire inside the silver-plated metal pins.
An alternative is to use a set of gold-plated pins (male and female). These pins can take a lot of current, but if improperly installed, they might short out. This happens when the heat-shrink tubing leaves part of the metal exposed.
That leaves us with the Deans Ultra connector. First of all, it can take a lot of current. Best of all, it is still easy to solder heavy-gauge wire to the pins.
But you will still have the problem of applying a lot of force to separate the mating halves. This is where the Star Plug comes in.
The company has developed a housing or cover that snaps over a Deans Ultra connector. This gives you something to grip other than the wires. I think the photos included with this column tell the story.
In the “Sources” section I’ve provided the address for the Star Plug website. I believe the company offers a video that covers the installation of these connector covers. I’ve also included the Tower Hobbies website where you can order them. The price is $2.99 per set (mating halves). This is definitely the way I’m going in the future on my larger models.
SOURCES:
Innov8tive Designs
(760) 468-8838
www.innov8tivedesigns.com
Radical RC
(937) 256-7727
www.radicalrc.com
Star Plug
www.rcstarplug.com
Airtronics
(714) 964-0827
www.airtronics.net
Tower Hobbies
(800) 637-6050
www.towerhobbies.com
