Radio Control: Helicopters
Larry Jolly 15781 Empire Ln. Westminster, CA 92683
Introduction
Welcome back. This month I have the pleasure of introducing a new helicopter—the Kalt Enforcer, distributed in the U.S. by Hobby Dynamics.
The Enforcer is a derivative of the Kalt Space Baron, but it is not the same machine; there are several important differences. The main change is the gearbox. The Space Baron's so-called "planetary" gearbox tended to chatter. The problem was traced to idler gears that turned on plain bushing-type bearings instead of ball bearings. The Enforcer uses needle bearings on those idler gears, and the previous transmission vibration problem has been eliminated.
Another difference is that the rotor blades are produced by Tech Specialties instead of by Kalt. These changes are what make this machine an Enforcer and not a Space Baron.
There are many similarities between these later Kalt helicopters and Kyosho's Concept 30: both designs originated from Taya’s drawing board and are .30-size helicopters with a lot of sophisticated molded parts. However, parts are not interchangeable, and the Enforcer is certainly not just another Concept. The Enforcer's transmission is quite different, and the engine is positioned forward of the main shaft and canted about 15° forward from vertical. The rotor head is also very different — I haven't seen anything quite like it before.
In one respect the Enforcer is the equivalent of the Concept SE, in that it uses ball bearings nearly everywhere. Taya has done many things differently with the Enforcer; whether for a specific reason or simply to be different, I don't know. Both the Enforcer and the Concept are fine helicopters.
Kit and power
My Enforcer was supplied as a kit. It will be available from Hobby Dynamics as a kit or ready-to-fly. I understand the ready-to-fly version will have a new Webra .35 engine, which should be exciting because this ship can certainly make use of the power.
My Enforcer has an O.S. .32 helicopter engine with the Concept-style muffler. For guidance I'm using a JR PCM 10 radio featuring NES 901 servos. I hadn't used these servos before, but I find them perfectly acceptable for helicopter use, with minimal backlash and good power.
The instruction manual supplied is excellent; mine happened to be a Space Baron manual with English translations.
Construction tips
The kit version is assembled in modules in nine main steps, which should not be difficult for anyone to complete. As you follow along, however, watch a few items:
- Step #2-2 (planetary gearbox): My kit had some thin spacers that looked like washers but were not mentioned in the manual. I had to tear down the transmission case for an hour to put them in underneath the idler gears. These spacers keep the gears from having any up-and-down travel and thus stop transmission vibration.
- Use grease and Kalt Tite as the manual instructs. I had to disassemble part of the tail rotor and discovered I had used too much Kalt Tite on one of the tail rotor housing screws. It was difficult to disassemble, so go sparingly — Kalt Tite goes a long way. Make sure you grease everything in the transmission, as lack of lubrication could be a source of howling. Also, watch the tail rotor drive gears: keep those ball bearings greased and clean.
- Step #2-3 (swashplate): My swashplate appeared to have a lot of slop, so I contacted Hobby Dynamics and they sent a replacement. Later in the build I found I didn't need the new part. The ball is not as tight as I would like, but it works fine because the swashplate is suspended by mixer arms and bellcranks similar to the old Schuster Heli-Boy system; you really don't notice the slop in the ball.
- Decals: In step #8, put the decals on before mounting the tail fins. My decals did not want to stick well and tended to lift in the sun despite being attractive.
- Servo pushrods and servo arms: The Enforcer comes with good Kalt ball links that fit well. The Japanese commonly use Z-bends at the servo connectors to avoid the extra slop or drag of a ball link. Be careful when drilling servo arms for pushrods — do not drill the hole oversize. Fit the pushrod without forcing it to avoid cracking a servo arm. If you need practice, use a spare arm first.
The final nine steps (those relevant to the ready-to-fly version) cover putting on the tail boom, mounting the rotor head, and installing the servos, receiver, and gyro.
Kalt supplies a gyro box that sits right under the main shaft with a cover to keep fuel residue out; it’s right on the axis where it’s most effective. Kalt also supplies servo tape and foam rubber for mounting the battery, receiver, and gyro in the cabin.
Throughout the Enforcer's design and parts I saw a real commitment to quality. Parts fit well and the machine is very well laid out and executed. It is a very pleasing helicopter to work with.
Rotor head and airframe details
- Basic structure: Side frames are molded from reinforced plastic, a commonly accepted method. Like most .30-size machines, a lot of plastic and nylon is used in the airframe.
- Tail boom: Aluminum tail boom houses a piano-wire drive shaft for the tail rotor.
- Tail gearbox: A 90° bevel gear box with a plastic housing and two ball bearings on each shaft.
- Tail rotor blades: Molded nylon; each blade has two ball races.
- Engine mount: Angled forward approximately 15° from vertical and positioned ahead of the main shaft.
- Collective pitch: Achieved via a rod sliding up through a hollow 10 mm main shaft.
- Main rotor head: The hub is a molded nylon piece rigidly attached to the main shaft. The flybar is pivoted through the center of the two housings that trap the blade mounts, yielding a very tight, low-slop head. The blade attachments use spring-steel plates (approximately .045 in. thick). The blade spindles bolt to these plates and are followed by molded nylon blade hubs that also cover the bearings. The head’s center portion is rigid; independent blade flapping is achieved through flexing of the steel plates. Lead/lag is controlled by the single-axis blade mount and by slight rotation of the spindle on the steel plate. My ship hovers and does aerobatics very nicely without noticeable vibration.
The overall lack of slop in the Enforcer's rotor head is remarkable. My model's parts move freely — the balls don't have much drag — but there is no flybar slop: you can rotate the flybar by hand only by moving the servos. There is minimal blade slop when rotating the blade by hand, and only a little slop in the mixer. The Enforcer is probably one of the tightest helicopters I have ever flown.
The cabin is sleek and racy, molded from what appears to be polypropylene (difficult to paint but very impact resistant). The cabin is held in place by two small keys on the bottom of the main frame and two posts at the rear; these keep it secure. Because the engine is angled forward, the starting cone is accessible via the top of the cabin, which is nicely laid out. Kalt did not provide easy access to the glow plug, however — you may need a remote head lock or another device to power the glow plug.
Flying characteristics
The Enforcer flies very well. As a .30-size helicopter, many people will look at it for training; it will do well in that role, as well as satisfying intermediate and expert pilots. It hovers very stably and is capable of excellent aerobatics. Mine loops and rolls with ease, performs an excellent rolling stall turn with substantial carry-through, and autorotations are predictable with a very good flare. It is a lot of fun to fly.
The Enforcer exhibits both stability and responsiveness. There is plenty of collective throw for negative pitch, which helps with inverted maneuvers. The helicopter seems to like a lot of rotor RPM for aerobatics, so set your ship up accordingly.
Radio setup and pitch settings (JR PCM 10 examples)
The manual is explicit about pitch settings. If you use a JR PCM 10 like I do, try these pitch-curve ideas:
- Normal:
- High stick: +10°
- Neutral: +6°
- Low stick: +2°
- Idle-Up 1:
- High stick: +10°
- Mid stick: +4°
- Low stick: -2°
- Idle-Up 2:
- High stick: +10°
- Mid stick: +4°
- Low stick: +4°
- Throttle Hold:
- High stick: +15°
- Low stick: -4°
With these settings you'll likely do loops and rolls in Idle-Up 2. The Enforcer handles a lot of negative collective pitch well and holds attitude without perceptible sink. Do rolling stall turns in Idle-Up 1.
Suggestions and notes
- Glow plug access: I would have liked Kalt to supply a method for glow plug access.
- Tail boom support: Add an extra support on the tail boom for the tail rotor pushrod. This will reduce flex and resultant slop in the pushrod system.
- Fuel pickup orientation: Don't let the fuel level get too low. Because of the tank's position, the fuel pickup orients to the left side of the helicopter. At low fuel levels (one-quarter tank and less) in a right bank, fuel can move away from the pickup and cause premature engine stoppage.
- Accessories: Expect many add-on accessories. I’m testing a set of Phoenix blades I got from Nick Nikolas at Vortex Distributors in Anaheim, CA. They work well for full-house aerobatics.
Summary
I found the Enforcer, paired with an O.S. .32 engine and JR PCM 10 radio, to be an excellent combination. The ship looks good, is a dream to fly, and goes together very well. I'm impressed with the overall quality and look forward to spending a lot of time flying it.
Thanks to Kalt for making a fine helicopter and to Hobby Dynamics for sending one to test. This has been a real pleasure.
Next month I'll report on the .30-size contest in Chino, comparing Concepts, Enforcers, and Shuttles back-to-back, and looking at how people have modified their ships and the techniques they use. Tune in next month for a .30-size roundup.
Transcribed from original scans by AI. Minor OCR errors may remain.
