DX Upper Tree-House & Fan 12 June, 2010 Esguerra

Definition “Blue sky” recommendations assume – Sufficient budget – Sufficient schedule – Sufficient manpower

Access from this side. M3 swing-arm Upper DX tree-house structure Rigidly attached to C-ring extension Upper fan enclosure also rigidly attached to C-ring extension

Upper DX tree-house structure Attached to C-ring extension Upper fan enclosure also attached to C-ring extension All rigid attachments

Comments It makes sense to isolate the C-ring extensions from any source of vibration The tree-house and tree-house ventilation are vibration sources – As demonstrated through AO testing – As demonstrated through vibration testing “Blue-sky” recommendation – Replace all rigid attachments to the C-ring extension with isolation Wire-rope isolator? Elastomeric? Flexure? – Isolation performance should be *tested* Quantitative test of isolation under representative loading Testing before and after installation – To verify improvement – To quantify performance

DX Upper Tree-House Fan

DX Upper Tree-House Fan Motor Operating at current low speed (16-Hz), there is obvious undesirable motion of the motor Motor is mounted through elastomeric pads to sheet-metal – The sheet-metal base is probably as compliant as the isolators for small displacements Whole motor assembly wobbles – Compliance of the sheet-metal structure – Varying belt tension during operation – Motor imbalance / cogging? Belt might also have dynamics – At higher speeds Balancing the fan will not fix any of this

Tensile Load Motor rocking motion(coning) Rubber mounting pads

DX Upper Tree-House Fan Fan is a “squirrel cage” type Connected to motor by belt/pulley (1:1) Bearing and pulley attached to sheet-metal through flimsy looking assembly

Tensile Load I would guess that this is not very stiff.

“Blue-Sky” Recommendations Eliminate pulley system – Direct drive, or through viscous damper, or bellows – Use a different fan/motor Attach fan and motor to common “frame” – Frame should be stiff – First mode (of assembly) should be higher than motor disturbance Should be able to measure motor disturbance frequencies directly <1-second decay; (8% decreasing OK with higher frequencies) Isolate common fan/motor frame – Isolate fan/motor connection to tree-house Isolation first mode should be less than lowest motor/fan disturbance frequency Damping is good (don’t use normal springs) Wire rope isolation? Flexible ductwork from tree-house to fan assembly/heat exchanger compartment – Isolate connection to C-ring extension if connection is necessary Balance fan/motor before reinstallation – Recommend testing in-lab before installation If there is still appreciable vibration – Additional passive or active vibration attenuation at the fan/motor frame – TMD or active vibration control

“Blue-Sky” Recommendations Isolation performance should be *tested* – Quantitative test of isolation under representative loading – Testing before and after installation To verify improvement To quantify performance