bryancobb
Junior Member
- Joined
- Aug 2, 2010
- Messages
- 5,400
- Location
- Cartersville, GA
- Aircraft
- Owned Brantly B-2b/Fly Kitfox III/Mini-500b/Piper PA-38
- Total Flight Time
- 1350
Hey Folks,
Different materials have different CTE's (Coefficient of Thermal Expansion). I use the principle every day in my job when designing Invar, Steel, Aluminum, or Composite build molds and tooling for advanced composite aircraft parts.
I admit however, that when it comes to my main rotor gearbox on my experimental helicopter, I am simply not smart enough or experienced enough to be able to understand or calculate the in-flight geometry after the components' temperature stabilizes at a nominal between 160 and 180 DegF. My intuitive answer is that generally, everything loosens-up. I'd really like to get more understanding from someone with experience calculating this.
My case is aluminum. I can calculate, or use CAD or water-displacement, or weight to determine the amount of aluminum in it. Because of its complex shape, I cannot get my head around how it expands in all directions.
Pinion and Mast bearings are typical tapered rollers. The mast has the same ones as 2013 GM 2500 pickups (9436881 387AS/382A). I chose high-priced aerospace grade dual pinion bearings in the . They are FAG 33202'S. I'm using Robinson R-22 Blue gearbox oil.
I wish I could determine the "cold-tightness" or preload needed to give "normal helicopter spiral bevel gearbox spec's" at operating temperature. Anyone have specific experience in this?
Thanks In Advance,
Different materials have different CTE's (Coefficient of Thermal Expansion). I use the principle every day in my job when designing Invar, Steel, Aluminum, or Composite build molds and tooling for advanced composite aircraft parts.
I admit however, that when it comes to my main rotor gearbox on my experimental helicopter, I am simply not smart enough or experienced enough to be able to understand or calculate the in-flight geometry after the components' temperature stabilizes at a nominal between 160 and 180 DegF. My intuitive answer is that generally, everything loosens-up. I'd really like to get more understanding from someone with experience calculating this.
My case is aluminum. I can calculate, or use CAD or water-displacement, or weight to determine the amount of aluminum in it. Because of its complex shape, I cannot get my head around how it expands in all directions.
Pinion and Mast bearings are typical tapered rollers. The mast has the same ones as 2013 GM 2500 pickups (9436881 387AS/382A). I chose high-priced aerospace grade dual pinion bearings in the . They are FAG 33202'S. I'm using Robinson R-22 Blue gearbox oil.
I wish I could determine the "cold-tightness" or preload needed to give "normal helicopter spiral bevel gearbox spec's" at operating temperature. Anyone have specific experience in this?
Thanks In Advance,
