Originally Posted by
Henning
I flew my Naruke Ascent for the first time this weekend with the Brenner V4 drive. This is the the third motor set-up in this model. First Pletty Advance and then the OS belt drive. Both works well but the Contra took the model to another level flying the F17 schedule. The constant speed and the breaking just makes the manoeuvres look less stressed. I got more time to prepare for the next manoeuvre. The torque and power of the Pyro 600 with Mejzlik 22x20F and 22x22R are very good.
After gaining some knowledge with rubber damping the OS belt drive I decided to design my own motor mount for the Contra drive. One of the main motivation for designing my own was due to the “issues” that has been reported with the rear support bearing and twisting in knife edge manoeuvres in the F17 schedule. My mount eliminates that problem. The pictures explains it better than me.
Regards,
Henning
Hey Henning,
By the way, the issues due to twisting of the rear support have been identified as being due to the natural rubber grommets that were shipped with the Budd Mounts. These grommets have a "linear" stiffness, and the material itself doesn't have very much internal damping. They are very much like using springs without any damping to limit travel.
What we have found is that replacing these natural rubber grommets with the blue vibration isolators from E-A-R Composite Specialties solves all of these problems.
This is because these "blue isolators have much more internal damping, and their spring compliance is "non-linear". The internal damping eliminates any displacement of the Drive as is accelerates through its first natural frequency, and the grommet spring stiffness gets progressively stiffer as the mount starts to move, which limits displacement.
We are currently running with these blue isolators on both the front motor plate and the rear support plate, and the system works well.
I practice the F17 schedule regularly, and I am having no issues. My motor noise doesn't significantly increase when I fly the corners of the inverted top hat, and my Allure tracks through these corners very cleanly, even with large amounts of rudder deflection.
Brenner ...