/ Let's talk flail mowers #7,581
- May 15, 2018
- Adell, WI
- Massey Ferguson 2706E, Massey Ferguson GC1705
I’m sorry but what degree did you get and what metallurgical and machinery specialty do you have to say this?
First 540 or even 2000 rpm is considered a low speed application for bearings
Second the manual generally speaking is absolutely correct. Depending on design clearances and specific bearing tolerances more grease can definitely work against reliability. It is not uncommon in general industry, where bearings at this speed carry far greater loads, to only need grease every 8000 hours. In that case overgreasing (too much or too often) can and will result in overheating, premature grease breakdown, and bearing failure.
It may be that the OEM supplied a poor quality bearing or simply had a defective assembly. That does not mean the manual is incorrect based on anecdotal evidence from 40 years ago. You simply cannot say their manual or engineering is wrong based on a single case when (to my knowledge) you have not done a full inspection of the failed unit. And recommending against an OEM in a public forum is irresponsible ; hopefully no one who reads your post will follow your specific advice.
Based on that reasoning - I guess adding lead to the gas for my car will make it run better…it did in 1960!
It is obvious you have a huge wealth of knowledge and expertise around flail mowers. That does not make you an expert on all aspects of modern equipment, so please consider that when you post because so many (including me) do look to you for that advice.
This is very true. I design machines in the food industry (specifically meat forming equipment). We have bearings that go for 800 hours of run time between greasing. The machines are in wet environments and food grade grease sucks compared to regular grease. Every day a cleaning crew comes in to the cold (~40°F) plant and sprays hot water all over the machine to clean it (usually getting it into areas it doesn't belong). Every inch of the machine is covered in water, whether from direct spray or condensation. Yet the bearings last with greasing them only every 800 hours. 500 hour grease interval on a sealed bearing on a flail mower is not unreasonable.
Over greasing can cause a seal to come loose. At that point you are inviting anything and everything into your bearings to destroy them. Bearing materials and greases have come a long way in recent years giving extended life to both. I would personally stick to the 250-hour grease schedule as mowing is going to generally be either dusty or wet. Either the grass is dry and dusty or its green and wet. My Alamo mower says to grease every 8 hours of use, but it is older and it appears to have shielded bearings instead of sealed.
A number of things could have caused this bearing to fail. To me it more looks like the shaft wasn't fully in the bearing. It was only holding on by a little bit causing excess pressure on the inner race where it is not supported by the balls. The other possibility is that bearing race missed heat-treat day, as typically when bearings fail the race is still in a recognizable shape. Or it could be an unfortunate combination of both. I don't see excessive heat on either the bearing or the shaft indicating the bearing seized up, and it looks like the balls are still there as well as what appears to be the rubber seal. I would rule this a manufacturing defect, not a lack of greasing.
The manufacturer of the machine has to warranty the machine. If they didn't honestly feel that the greasing interval was correct, would they suggest it? If machines fail due to under-greasing per their manual they are on the line for expensive parts. If they are offering to replace all the components, they are confident that it wasn't due to you not greasing it, but rather a manufacturing defect.
I would take their offer, as you're getting an extra set of hammers for your time. I would also inspect the assembly when you reassemble it to make sure the shaft is fully in the bearing race. Pop off grease covers to verify there is grease in the bearings if you feel concerned about lack of grease. I would chalk it up to "stuff happens".