higher engine orders 9-15-21
higher engine orders 9-15-21
(OP)
Hi,
We did a couple of vibration tests on a bus engine compartment (rear drive+north-south engine) to find the root cause of high level of vibrations perceived inside the bus. On the engine/transmission active and passive sides we see normal engine orders dominating (3-6-9). However, the problem inside the vehicle seem to be coming from 9-15-21 (multiples of 3) orders and on the vehicle they seem to be coherent at rear differential connection (shaft to rear axle attachment point). The number of gear teeths at pinion are totally different. How come these higher orders excite(d) the structure? What component they can be related to? This is a problem I have not experienced before.
thanks for the ideas in advance
We did a couple of vibration tests on a bus engine compartment (rear drive+north-south engine) to find the root cause of high level of vibrations perceived inside the bus. On the engine/transmission active and passive sides we see normal engine orders dominating (3-6-9). However, the problem inside the vehicle seem to be coming from 9-15-21 (multiples of 3) orders and on the vehicle they seem to be coherent at rear differential connection (shaft to rear axle attachment point). The number of gear teeths at pinion are totally different. How come these higher orders excite(d) the structure? What component they can be related to? This is a problem I have not experienced before.
thanks for the ideas in advance





RE: higher engine orders 9-15-21
- Steve
RE: higher engine orders 9-15-21
M
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Dr Michael F Platten
RE: higher engine orders 9-15-21
Thanks for the answers.
RE: higher engine orders 9-15-21
M
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Dr Michael F Platten
RE: higher engine orders 9-15-21
I assume this is an I6 engine?
A campbell's plot is the most useful diagnostic as Steve says.
Not too sure how much I trust coherence with order type signals, in theory all of them should be 100% coherent with all paths.
Cheers
Greg Locock
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RE: higher engine orders 9-15-21
RE: higher engine orders 9-15-21
RE: higher engine orders 9-15-21
RE: higher engine orders 9-15-21
RE: higher engine orders 9-15-21
dt (roller distance to roll center)
dw (roller nominal diameter)
z number of rollers
alfa angle of contact
how can we calculate dominating orders for any bearing with the properties given above. I believe we have found a link between the orders shown in the figure and the first bearing
thanks for the help
RE: higher engine orders 9-15-21