Who’s an expert (or even reasonably knowledgeable) on bungee style landing gears?
I am trying to work out the design details for the new landing gear on my Starduster, combining three different designs. The original Starduster design had the bungees mounted vertically inside the fuselage, as on a Taylorcraft. The later design has the same bungee arrangement, but the legs are longer and the design is improved to eliminate the weak spot where mine broke. My plane has the original shorter legs but Cub style external bungee struts. My new gear will be the longer length, but retaining the Cub style strut arrangement… except that I want to replace the bungee struts with die spring struts from Wag Aero, since I would have to remake the bungee struts longer anyway.
What I’m trying to get a handle on is how the bungee gear works. Am I correct in understanding that with the airplane (e.g. a Cub) at rest on the ground, the shock struts are fully compressed by the bungees against a hard stop, and start to extend only when the load exceeds the initial bungee tension? In this case the landing gear wouldn’t extend any further when the plane takes off. I know that on some older planes the gear is already in mid travel when the plane is sitting on the ground, and droops down quite a bit further in flight.
The Wag Aero struts are rated 2200# at mid travel. 2200# is not the wheel load but the load in the strut, which is a function of its geometry. My plane uses two 1080HD bungees per side, as does the Super Cub. A 1080HD bungee is rated 900# for a total of 1800# per side, but I don’t know what that number is based on, i.e. what amount of stretch. But the die spring strut is made for Wag Aero’s Cub clone and the geometry is similar, so it should work (?) I don’t know what the total travel is of the Wag Aero struts, but I don’t know what the available travel is of a Cub strut, either.
Does anybody here know these things?
Dana
I am trying to work out the design details for the new landing gear on my Starduster, combining three different designs. The original Starduster design had the bungees mounted vertically inside the fuselage, as on a Taylorcraft. The later design has the same bungee arrangement, but the legs are longer and the design is improved to eliminate the weak spot where mine broke. My plane has the original shorter legs but Cub style external bungee struts. My new gear will be the longer length, but retaining the Cub style strut arrangement… except that I want to replace the bungee struts with die spring struts from Wag Aero, since I would have to remake the bungee struts longer anyway.
What I’m trying to get a handle on is how the bungee gear works. Am I correct in understanding that with the airplane (e.g. a Cub) at rest on the ground, the shock struts are fully compressed by the bungees against a hard stop, and start to extend only when the load exceeds the initial bungee tension? In this case the landing gear wouldn’t extend any further when the plane takes off. I know that on some older planes the gear is already in mid travel when the plane is sitting on the ground, and droops down quite a bit further in flight.
The Wag Aero struts are rated 2200# at mid travel. 2200# is not the wheel load but the load in the strut, which is a function of its geometry. My plane uses two 1080HD bungees per side, as does the Super Cub. A 1080HD bungee is rated 900# for a total of 1800# per side, but I don’t know what that number is based on, i.e. what amount of stretch. But the die spring strut is made for Wag Aero’s Cub clone and the geometry is similar, so it should work (?) I don’t know what the total travel is of the Wag Aero struts, but I don’t know what the available travel is of a Cub strut, either.
Does anybody here know these things?
Dana
