DX Upper Tree-House & Fan

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

2. Definition • “Blue sky” recommendations assume • Sufficient budget • Sufficient schedule • Sufficient manpower

3. 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

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

5. 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

6. DX Upper Tree-House Fan

7. 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

8. Motor rocking motion(coning) Rubbermounting pads Tensile Load

9. 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

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

11. “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% damping@10-Hz, 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

12. “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