Swashplate: Compass Model Atom 500E/CF ARF
Michael Ramsey
The electric-power advantage is obvious in this compact machine.
The number in the helicopter’s name threw me at first. After several learning and fun seasons with 450-class machines, the Atom 500 arrived. My expectation about the size difference was that the increase would be minor; helicopters are often named based on either the motor or the blade size they use.
Happy me — with lots of 450-class experience (models named for the motor class) — my eyes nearly popped out when the Atom 500 arrived (named for the blade size). Just 50 little number values different, this aircraft is almost twice the size of the 450. That surprise meant looking at accessorizing to suit the larger machine.
KBDD was the distributor at the time the Atom 500 project started. The importation process was beginning, and the only Atom available initially was the carbon-fiber-frame version.
Two Atom models are offered: the carbon-fiber-frame version and one with frames and flat-milled parts made from G10 material. Both are ARFs. The cost difference is roughly $50. The carbon-fiber frame is stiffer and a modest advantage in weight compared with the electronically passive, circuit-board-like G10 material.
Better than a typical ARF, the Atom 500 came with the motor and ESC, both of which were healthy. Many say the included 500 BL HT motor is oversized, but since when has that been a bad thing for a 3-D helicopter pilot’s dream?
The 60-amp ESC is prepared, minus the battery and motor connectors. Its BEC can handle 3 amps of load for the servos and accessories. Planning to fly conservatively at first, I predicted a separate BEC might be needed later.
Sport fliers will consider the nice offering from mini digital and nondigital servos from Hitec. Nondigitals fit well into the smartly shaped and located servo openings. The 3-D and precision pilots will demand performance that only digital servos can offer. With three directly linked servos managing the CCPM cyclic controls, “overpowered” isn’t a bad idea.
The JR DS3517 servos used for the cyclic have metal gears for durability, excellent centering, and strong power. They fit into the frame with room to spare, which meant the grommets needed to be offset a bit to fully secure the case. Servos that wobble in their mounts can cause trimming issues, so choose a mini-sized servo with four lug points.
On the tail, the JR G7703D gyro found a home on the aft-located gyro plate, straight above the frame-located tail-rotor servo. That spot was filled with the smallest tail-rotor servo JR offered: the S3500G. (The newer JR G3703D gyro system would also work nicely.)
I like boom-mounted tail-rotor servos on electric helicopters for their ease of adjustability, but the Atom’s tail-rotor-control servo location makes sense for lateral and vertical balance. The nice thing about boom-mounted servos is they move with the boom if drive-belt tension requires adjustment.
A good thing about the Atom is that the belt is dimensionally superior to that used on a pro-type 50-class glow helicopter. A strong belt won’t need frequent adjustment, so I’m fine with the tail-rotor-servo location.
Specifications
- Rotor diameter: 962 mm
- Weight: 1.75 kilograms
- Length: 835 mm
- Height: 270 mm
- Motor: 500 watts
- Gear ratio: 8T, 9.75:1; 4.286; 9T, 8.67:1; 4.286
- Construction: Carbon fiber (optional G10 frame)
- Control system: CCPM 120° swashplate
- Drive system: Belt-driven tail rotor
- Main rotor blades: 420 mm main, 70 mm tail
- Tailboom: Oversized, aluminum
- Canopy: Factory-painted fiberglass
- Landing gear: Multipart plastic-and-aluminum assembly
- Battery: 14.4- to 22.2-volt Li-Poly (6S recommended)
- Requires: Six-channel helicopter radio system, gyro, digital miniservos
- Price: $499.95 ($459.95 for the G10 version)
Test-Model Details
- Motor used: Compass 500 BL HT, 1080 Kv (included)
- Battery: 22.2-volt, 2600 mAh 35C Common Sense Li-Poly
- Radio system: Spektrum DX6i transmitter, Spektrum AR6200 receiver, three JR DS3517 cyclic servos, JR S3500G tail servo, JR G7703D gyro, Compass Premium-60 ESC (with 3-amp BEC)
- Main blades: 420 mm MAH carbon fiber
- Tail blades: KBDD 70 mm (4 mm hub)
- Paddles: KBDD 500 class
- Ready-to-fly weight: 64.8 ounces
- Flight duration: Four to seven minutes
Pluses
- Precision CCPM 120° metal swashplate
- Aluminum rotor head and tail-rotor gearbox
- Strong G10 or carbon-fiber frame design
- Low parts count
- 80% preassembled
- Extra-large boom avoids static discharge
- Oversized power system meets demands easily
Minuses
- Exceedingly tight ball links (better than too loose)
- Limited recommended battery capacity
- Oversized servo openings
The Atom is sleek and low-profile. Part of that look comes from the absence of tailboom supports, which echoes one of Compass Model’s major goals: offering performance helicopters with low parts counts.
Because the powder-coated aluminum tailboom is large in diameter, it’s good at withstanding loads without additional bracing. To keep the boom from twisting, it’s keyed into the frame and tail cases. Once snugged into position, it doesn’t shimmy.
Play in the fit of parts is expected with any helicopter; however, after a season of flying my Atom 500, it doesn’t have any slop or play in the parts. That includes the programmable head.
When assembling the machine, I had to remove the prefitted linkages and size them because they were so tight. They’re still slightly snug. Electric helicopters don’t get lubricated like glow-powered helicopters do, so from time to time the Atom’s swashplate, sliders, and links get a touch of lubricant.
The model came assembled with the motor installed, with the stock nine-tooth pinion. The disappointing part about it being an ARF is that enjoying the engineering majesty is left for later, when maintenance or repair is needed.
The main shaft is stout, 8 mm thick and fairly short. The stepped drive gear has heavy teeth that withstand torque from the high-output motor and the jumpy throttle changes I asked of it. Still, its inner supportive webbing is light, which is good for improper ground impacts — that part will gladly sacrifice itself to save more valuable (and expensive) drive-system parts.
I downloaded the instruction manual and highly recommend printing it in color if you can. I found no complications with the manual other than occasional hardware-dimension variation. The good thing is long bolts can easily be shortened.
Compass made installing the servos before everything else on the frame easier; it’s less awkward to assemble that way.
To prevent the belt from slipping, keep its tension to a bare minimum. I can barely flex mine between the main gear and the pulley tensioners. Condition the belt with a light spray (I use WD-40) on a regular basis.
Without boom supports there’s no place to mount a horizontal stabilizer, so Compass left that part off. Most 3-D pilots remove the stabilizer anyway because it creates unwanted drag in flips.
Like the frame sides, the vertical fin is robust and hasn’t shown any vibration. The fin is a bit short, though.
If you’re careless, a tilt on the ground can quickly modify the stock plastic tail blades so they’ll fit on a 450-class machine. I thought the stock blades were too flexible anyway. The KBDD blades on mine work great.
The sleek fiberglass canopy is just large enough to cover the recommended 6S 2600 mAh Li-Poly battery. I found some batteries were a really tight fit, but the Common Sense 2600 35C is a perfect match for this machine.
That said, 35C batteries are the lowest-rated packs I’d run in this machine. It demands low-resistance power, and you’ll want that power available.
My prepainted canopy has the old color scheme. The current Common Sense RC canopy has more yellow than white. Both are attractive. The molded-in grommet and Delrin lower bracket mount locations were spot-on.
A long-range radio system is required for this class of machine. I like the Spektrum DX6i transmitter’s simplicity, and the throttle and switch locations suit my tastes.
The Atom includes servo arms sized appropriately to achieve the correct geometry with the swashplate. Two sets are provided — one for JR and one for Futaba servo users.
One revision I’d like to see on future Atom 500 kits is the flybar. The independent flybar stabilizer arms lock on with a grub screw. A precision-machined flat at the arm location on the flybar would aid alignment and ensure accurate orientation of the arms.
I know I claimed the Atom 500 was named for the size of blades it uses, but the recommended blade size is 420–430 mm — not 500. That's silly, huh? I don't make the rules; I merely report them.
Available from Model Rectifier Corporation, MAH makes some of the finest carbon-fiber helicopter blades on the market. Visit a dealer to get yours.
The 420 mm MAH set on my machine is balanced and beautifully finished. I haven’t needed to test 430 mm blades, but I suspect they’ll add stability to an already well-balanced machine.
For experimentation, I played with batteries, tail blades, and paddles. KongPower has a very light 25C 2600 mAh 6S pack that's great for sport flying; it got hotter than the rest when pushed.
The heartiest battery I tested was the RFI 3200 mAh 6S, also 25C. Available from Model Rectifier Corporation, this pack shifted the helicopter off its CG sweet spot but couldn’t be hurt no matter how aggressively I flew.
So far, I’m happiest flying the Atom with a 2600 mAh 35C 6S pack from Common Sense. I don’t know if it's custom-made for this machine, but it ought to be. Expect flights to last about four minutes if you’re a hard 3-D pilot; five minutes if you’re learning 3-D; six minutes for normal sport 3-D; or eight minutes if you’re mostly hovering.
Flying the Atom for the first time gave me that “OMG!” feeling. As I mentioned, my electric practice came from 450-class machines. The Atom 500 is a Cadillac by comparison, but with Corvette performance. The head speed and power were scary at first, but that’s the way these machines are and I quickly got used to it — also known as “spoiled.”
Forward flight requires a touch of forward trim, likely because it’s missing a large stabilizer as seen on F3C helicopters. The Atom is rock solid in a hover, like flying a 30-class glow-powered helicopter. In gusty conditions I never hesitate to fly the Atom; it hardly notices the wind.
I run approximately ±12° of pitch in both positive and negative curves. I can feel the machine’s bite — full collective is unnecessary to appreciate the power.
“Tick-ticks” are my new showstopping routine, because the Atom has the “pop” to arrest any approach angle. I get more aggressive with the model every time I fly it.
My latest favorites are the new paddles from KBDD (Compass helicopters’ previous distributor). KBDD makes the only replacement upgrade paddles for the Atom’s unique 2.5 mm flybar. The paddles smoothed out the Atom without taking away authority, and their bright color makes the machine easier to see.
When you’re learning, or even if you’re great at flying helicopters, service and parts availability is paramount. Don’t panic because Compass Model has been passed among different U.S. distributors; probably at least 100 dealers here carry parts for this line. I don’t think anyone will be disappointed with the Atom 500.
MA Michael Ramsey [email protected]
Manufacturer/Distributor:
Compass Model / Common Sense RC 9725 Owensmouth Ave. Chatsworth, CA 91311 (866) 405-8811 www.commonsenserc.com
Sources:
- KBDD LLC: (614) 863-1111, www.kbddintl.com
- JR: (800) 338-4639, www.jrradios.com
- Spektrum RC: (800) 338-4639, www.spektrumrc.com
- Model Rectifier Corporation: (732) 225-2100, www.modelrec.com
Other Published Reviews:
- None known at time of publication
Transcribed from original scans by AI. Minor OCR errors may remain.
