Mitch
08-05-2005, 05:22 PM
Many thanks to Peter Lovegrove for his excellent article in the latest gyro news.
Prior to flying my Butterfly after the Cooma event, I decided to ensure my rotor head system was set-up exactly right. I read the article several times and proceeded to action.
I believe it is important to note here, that not all hub blocks are the same. For instance my old original 1978 Benson Blades and Hub Bar have what appeared to me to be circular machined rebates into each side of the hub block. Upon discussing same with a number of people I was assured that each side of the block had been warn in by previous teeter bushes (tophats). This seems logical as they are not the same depth.
When I was advised to set my head up on Butterfly initially, the deal was to ensure a gap of 2.490" between inside faces of tophat teeter bushes. The distance between inside faces of towers 2.5".
To ensure this gap we were to make up shims of 6061-T6 from .0025" material and to place them each side of the towers between the teeter bushes and the thrust washers. They would require machining down to give the correct gap and tolerances. This may well have been the go on a hub block with no side rebates.
I have made up shims of same material one at 9 thou and the other at 14 thou that go between the inside faces of teeter towers and against the face of the hub block on both sides. Due to the different thickness, each face of the block and each shimm is marked, for correct placement. I now have about three thou float and the teeter bolt and block teeter on the bushes as required.
After flying for a couple of hours with two mates yesterday, I was very pleased at how smooth the whole system was. I had a look at the rotor head set-up on another gyro. We found it had no float at all. He advised me he has a slight two per rev through the stick. We reviewed the article and discussed the fact that he would need to shim inside faces also.
I would appreciate any further comment on this, it is so easy to get it wrong and I believe not fully understood or appreciated. The rebates in the hub block certainly caught me out. If it's not set-up correctly you can find the block sliding on the teeter bolt, causing excessive wear to bolt and block, ect.
Cheers,
Mitch.
Benson Blades.
I don't really know any different, because I soloed on Benson Blades but they drop out last few feet. My only comparison is to the two place trainers I have been in. They are all using new generation stuff and the flare is totally different to my Bensons, they don't hang on. I only mention this because it has been something like 6 weeks since I flew at Cooma. Saturday first landing was a gooden, because I flew her all the way in, no flare to speak of. Next landing I tried to hold her off a little and they let go and I dropped in. Almost like what has been described as what happens in a down wind landing. Look out! :o :oops:
Prior to flying my Butterfly after the Cooma event, I decided to ensure my rotor head system was set-up exactly right. I read the article several times and proceeded to action.
I believe it is important to note here, that not all hub blocks are the same. For instance my old original 1978 Benson Blades and Hub Bar have what appeared to me to be circular machined rebates into each side of the hub block. Upon discussing same with a number of people I was assured that each side of the block had been warn in by previous teeter bushes (tophats). This seems logical as they are not the same depth.
When I was advised to set my head up on Butterfly initially, the deal was to ensure a gap of 2.490" between inside faces of tophat teeter bushes. The distance between inside faces of towers 2.5".
To ensure this gap we were to make up shims of 6061-T6 from .0025" material and to place them each side of the towers between the teeter bushes and the thrust washers. They would require machining down to give the correct gap and tolerances. This may well have been the go on a hub block with no side rebates.
I have made up shims of same material one at 9 thou and the other at 14 thou that go between the inside faces of teeter towers and against the face of the hub block on both sides. Due to the different thickness, each face of the block and each shimm is marked, for correct placement. I now have about three thou float and the teeter bolt and block teeter on the bushes as required.
After flying for a couple of hours with two mates yesterday, I was very pleased at how smooth the whole system was. I had a look at the rotor head set-up on another gyro. We found it had no float at all. He advised me he has a slight two per rev through the stick. We reviewed the article and discussed the fact that he would need to shim inside faces also.
I would appreciate any further comment on this, it is so easy to get it wrong and I believe not fully understood or appreciated. The rebates in the hub block certainly caught me out. If it's not set-up correctly you can find the block sliding on the teeter bolt, causing excessive wear to bolt and block, ect.
Cheers,
Mitch.
Benson Blades.
I don't really know any different, because I soloed on Benson Blades but they drop out last few feet. My only comparison is to the two place trainers I have been in. They are all using new generation stuff and the flare is totally different to my Bensons, they don't hang on. I only mention this because it has been something like 6 weeks since I flew at Cooma. Saturday first landing was a gooden, because I flew her all the way in, no flare to speak of. Next landing I tried to hold her off a little and they let go and I dropped in. Almost like what has been described as what happens in a down wind landing. Look out! :o :oops: