lml@lancaironline.net Mailing List Archive

Content-Disposition: inline X-Mailing-List: lancair.list@olsusa.com <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> << Lancair Builders' Mail List >> <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> >> Prompted by Marvs' request that I give some comments on electric actuators I submit the following: Early on in the construction of my Lancair 4P, I decided that composites and hydraulic fluid were two substances that are not, by any means, compatible. As good and reliable as hydraulics are, they are always prone to leaks and the hydraulic fluid will eventually wind up soaking in to what ever it lands on. In the 4P, we rely on both bonding and bolts to hold the gear box in place and the gear box is subject to extreme loading during a hard landing. Also, remote mounting of the resevor and pump and the running of hydraulic lines takes this potential leakage problem outside the confines of the gear box. I did consider coating all areas exposed to leakage with a protective coating, but decided that because of flexing from stress even the coating would be susceptible to cracking. I also knew that bolts going through the composite material could not be absolutely sealed, even if I used a flexible coating. Contrary to some opinions, hydraulic fluid will migrate into the epoxy bonds causing separation in the laminates. Prove this to yourself by spilling a little fluid on a piece of raw composite and wiping it off right away. The stain cannot be removed, which means the fluid has migrated into the material. To see how deep the fluid actually soaked in, start sanding, you'll be surprised. So I finally decided to redesign the system for electric. On the main gear I used two rotary actuators and on the nose gear I used a linear actuator. The flaps are deployed by another linear actuator. The main gear actuators operate independently from each other and produce 1200 in-lbs of torque each and have internal brakes when voltage is not applied. The interface gear and mounting plate were machined and built in my tool shop. The only modification to the gear box was a 3" hole cut through the main diagonal spares and 4 bolt holes. Since the motors were over rated, a current limiter circuit was included to protect the gear components from over torque. Both up and down motion are accomplished in 5.5 seconds. The system as designed, has no free fall capability. After analyzing the system for probable faults, I concluded that the most likely trouble would come from limit switches, relays, or the current limiting circuit. So I included a emergency circuit that bypasses all of these. By activating a separate switch I can provide power to the gear motor straight from the battery. The nose gear has this same emergency circuit. The flap actuator was pretty straight forward with a modification only to the bell crank in the gear box. After the install was complete, I invited an engineer from Bell Helicopter to inspect my work. His only negative comment was, I should have anodized 7075-T6 aluminum mounting plates on the main gears. If I can answer any specific questions you might have feel free to e-mail me. Dick Simkanin > N80D, American Eagle 540 Engine. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> LML website: http://www.olsusa.com/Users/Mkaye/maillist.html Builders' Bookstore: http://www.buildersbooks.com/lancair >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>