Design of Tapered Round-Rod Tail Springs

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589KB taille 27 téléchargements 466 vues
Design Of Tapered Round-Rod Tail Springs By A. Szaraz, EAA 145 419 Center Rd., No. 2, Bedford, Ohio The tapered round rod tailwheel spring is shown here installed on the Vidervol VS-1.

N THEIR appearances at various fly-ins, the Daphnes Icerning and the Vidervol VS-ls have all drawn comment conthe unusual tail spring installed on these aircraft. Before going into the actual design, it would probably be a good idea to review some of the factors involved. 1. A small deceleration distance means high G loads. This dictates a fairly long length, a compromise between high G load and excessive flexibility. I'm quite sure that some tail spring troubles could have been stopped if the spring had been made a little longer and softer, instead of stiffer and stronger. For example, a 170 lb. weight dropped from 18 in. with a deceleration distance of 1 in. will register about 18 GS. With a deceleration distance of 5 in., the G load becomes approximately 4. 2. It seems logical that a round tapered rod with no stress concentration points and the diameters matched for the load along its entire length must give a longer trouble-free length of service than the conventional spring leaf. 3. The method of attach is just as simple as the spring leaf. 4. The weight should stay equal to, or less than, the spring leaf type. The first thing to determine is the weight of the tail in the three-point position with a gross load. You can weigh the aircraft or calculate it as outlined in Fig. 1.

I have deliberately kept this problem simple because, if you are familiar with engineering terms, it needs no explanation and, if you are not familiar, just follow the example. In the example, the tail load equals 104 lbs. Figure 2 shows the method of calculating the loads for the spring. I have chosen a length of 27 in. for our total length. At first glance, this might seem too long but, if you check a few tail springs on other aircraft, you will (Continued on next page)

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