Build Story
RAH-66 Comanche maintenance event.
Butch W.
Chapter 2 of 2
Maintenance Status.
Mar 11, 2025
I was pretty busy over the weekend on Comanche. Everything looked very good. The motor and gear box bearings were replaced and the shaft bearings were inspected and lubed. The grip bearing were inspected and lubed. Cleaned and inspected re-shimmed the TGB gears from .27mm to .30mm to take out some end play from the new bearing install. All the bearing on the pitch control assemble replaced lined and re assembled.
Replaced main motor bearings waiting for a replacement motor shaft. Inspected and lubed all main shaft bearings.
A few pics
Thanks for dropping by.
B
4 Comments
A short video I forgot to post.
https://www.youtube.com/watch?v=Y6fjuiG-bM0
What kind of mechanics is this?, looks very compact. Direct tail drive safes you a lot of mechanical transmission and weight.
Danny,
They are my design based on T-Rex 700 internals. The smaller tail motor is mounted just behind the main mechanics on a bulkhead and drives the Vario TGB and Fenestron assembly via a 6 mm torque tube and housing.
The torque tube and housing are roughly 20 inches long and uses 4 carrier bearings to support the shaft. I have turned the tail from 8500 to 10,500 RPM. It performs the best at around 9200 to 9500. The tail is 1 to 1 and runs on a 6s pack where as the main runs on 2 each 6s packs.
It did take some testing to get the tail ESC and gyro gains just right and working together. With the 1 to 1 drive, as the tail fan was under load, the speed would droop, maybe about 750 rpm, the tail gyro would add more pitch to maintain heading then the ESC would add more power to maintain speed, everything would catch up the tail gyro would reduce pitch causing what I called "gyro chasing".
The "happy" spot was reducing the ESC gain, running a slightly lower tail gyro gain and fan speed of 9300 RPM. Lower gains reduced the correction time to the ESC and tail gyro along with a little delay in the tail gyro made a nice flying machine. With the gains on the lower side it does not perform as a conventional tail but does fly sideways at a pretty decent speed.
The first vid was 14 years ago getting stuff sorted out. The second was about 10 years ago with some sideward flight.
Sorry for the long explanation.
Enjoy the video
B
https://www.youtube.com/watch?v=lgYc9h_GuM8&t=14s
https://www.youtube.com/watch?v=Qk1nG8nxJG0&t=10s
The best of the best!!!