Radio Control: Helicopters
Walt Schoonard
HELI-BABY Tail-Rotor-Drive Mod: When the Heli-Baby was first developed, the tail-rotor drive was accomplished through a V-belt drive that did not require much tension. However, in use this belt proved to be inadequate and was changed to the flat belt, which required a substantial tension. This tension caused a great deal of wear to the tail-rotor shaft running in needle bearings. It also caused wear to the clutch-gear shaft and clutch-needle bearing. The 1976 series Heli-Baby has an improved clutch bearing and has tail-rotor ball bearings that greatly improve the wear factor. However, the clutch-gear shaft is still supported by one ball bearing, and belt tension produces considerable drag that robs power to the head. I have made several suggestions to the powers that be to correct this problem with nothing being done, so I decided to do it myself.
The solution was to make a longer gear shaft and to support it with two ball bearings. There was nothing so great about that until I tried to get some gear stock to match the nylon gear. Each gear that was tried from American stock promptly ate the teeth off of the nylon gear. After exhausting every possible source, except from Germany, I was about to give up. However, a machinist friend found that we could have the gear machined to match the nylon gear. After all these months of testing different gear stock, the answer was right at hand. A kit has now been developed that will fit any Heli-Baby and Super-Baby. The kit consists of a new and longer gear shaft, a bearing block and ball bearing, two bolts and lock nuts, and a drill template to locate the two holes that must be drilled in the side frames. The instructions give step by step disassembly of the old clutch shaft and the installation of the new one. The installation is so simple that anyone will be able to do it with no special tool needed!
The real surprise is in the flying. Where any Heli-Baby normally lifts off at half power, it now lifts off at one-third power. The control improvement is apparent in all aspects of flight. Takeoffs are quicker and climb-outs much more rapid. Stops from descents are also quicker and more precise.
The mods are available from Miniature Aircraft Supply, 2563 Diversified Way, Orlando, FL 32804.
Heli-Baby Crashes: Since the introduction of fly-bars (cans or tubes as some prefer to call them), there have been many crashes from no apparent reason. Usually the helicopter is so badly mangled that it has been difficult to determine what caused the crash. So it has been written off to the possibility of interference, or radio failure, or pilot error. None of these are to blame. The cause has now been traced to the pushrod from the swashplate to the fly-bar control arms. These crashes have occurred during hard aerobatics where a severe mechanical load has been exerted, and this pushrod breaks in the threads. As odd as it may seem, the plastic ball joint is stronger than the steel pushrod.
This happened to my machine twice before I determined what had caused the crash. After examining the remains of the second crash, the only control mechanism that was broken was this pushrod. I then dug up the remains of the first crash, and sure enough, this pushrod was broken also! Considering that this pushrod is taking such a load and that its failure can result in a bad crash, some way had to be found to either strengthen it or reduce the load.
To solve the problem, I drilled the swashplate for an additional arm 180 degrees across from the original one. This arm was adjusted for identical length. An additional control arm was installed on the fly-bar on the opposite side of the rotor head. This control arm takes the place of the retainer collar. A pushrod with ball joints adjusted to identical length as the original pushrod was now installed. Many hard flights have now been made with no failure. This has also solved another problem with the cans and that is the dancing of the swashplate on hard cyclic commands.
Even if you have not yet experienced these problems and are using cans, I highly recommend this mod to prevent a very costly crash.
Kavan Jet Ranger: Next month's column will be the first of a series of articles covering the building and flying of the Jet Ranger. Since these kits have been on sale for several months, many have been sold so this will be a timely series of articles.
Many improvements have been made to this fine helicopter by a great number of people. Some drastic improvements have been made to the rotor head that improves the flying of this machine almost beyond belief.
If you're not flying, you're not trying! Walt Schoonard, 2080 Sharon Rd., Winter Park, FL 32789
Transcribed from original scans by AI. Minor OCR errors may remain.
