Thanks everyone for such a great response. I'm learning heaps about PTO shafts! I didnt realise the cover should stay stationary, I have greased up the plastic bearings at the end of the cover and looked into the chains. I don't think it's just the cover though as I tried running it with the cover withdrawn and it is still shaking itself to bits (see this vid https://user.fm/files/v2-2c4958d7cb4e6674b0e8085044ff1d1d/my-video.mp4)
So I took the shaft into a local tractor shop but they said they couldn't see too much wrong with it - they didnt think it was bent based on the fact it slid smoothly into itself (expanded/contracted) and there didnt seem to be excessive play in the universal joints.
So I'm still scratching my head a bit here. I'm hoping it's not the auger itself. The only thing I can think of is the shear bolt is a bit small (8mm rather than 10mm) I wonder if that would be enough to cause it? I only have a high-tensile 10mm bolt here, would that be ok given the shaft has a clutch? or does it need to be a "weak" bolt?
This is interesting to me as we have a lot of loose rock here and it's definitely going to be an issue - the BX25 at idle though doesn't have any real hydraulic flow/pressure (not sure about the terminology) and the PTO leaver is basically engaged or not, so I'm not sure I'll have much ability to slow it further than shown in that video which was only reasonably low engine revs from memory
So I took the shaft into a local tractor shop but they said they couldn't see too much wrong with it - they didnt think it was bent based on the fact it slid smoothly into itself (expanded/contracted) and there didnt seem to be excessive play in the universal joints.
So I'm still scratching my head a bit here. I'm hoping it's not the auger itself. The only thing I can think of is the shear bolt is a bit small (8mm rather than 10mm) I wonder if that would be enough to cause it? I only have a high-tensile 10mm bolt here, would that be ok given the shaft has a clutch? or does it need to be a "weak" bolt?
You really need to use the PHD at an idle and not running that fast. If the auger encounters something it will immediately shear the shear bolt. Slow it down. Slow also gives you better control.
This is interesting to me as we have a lot of loose rock here and it's definitely going to be an issue - the BX25 at idle though doesn't have any real hydraulic flow/pressure (not sure about the terminology) and the PTO leaver is basically engaged or not, so I'm not sure I'll have much ability to slow it further than shown in that video which was only reasonably low engine revs from memory