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Would be interested in some opinions on something I have been wondering about.I have had a gyro with what seems to be referred to as a pump stick, ie: one universal type join attached to the keel in one place.And a gyro with what I can only describe as a "2 bar" control, ie: attached to the keel in two places and 2 bars working back and forward under the seat. The pump stick travel is more like up and down than back and forward.With the "pump stick" I felt as if forces from the rotors in rough conditions came back through the stick and push it back or forward. I always felt someone unsuspecting could get into PIO easily. I would never have let go of that stick.With the "2 bar" , the stick travel is actually back and forward. This gyro I have flown in worse conditions and never felt that same force through the stick and felt comfortable flying it hands free.(though I believe it is a silly practice with no purpose)Is this anything to do with the configurations or more to do with the "pump stick" being on a lightweight gyro with light rotors and the other being a heavy Suby gyro with heavy rotors?? I do remember seeing an airworthiness directive, I think from England or USA, a lot of years ago in regards to pump sticks.Just curious [?][?]
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Mark,mate ,replace wot ever you'v got with one of Roscos sticks.[low profile,two rod thingy type setup][
]Very,I mean VERY strong and no way near the feed back problems as a pump stick.[
]I noticed the same differences as you,and I just put it down to the amplifying affect of the setup of the rotor feed back.[the hand pice is alot farther way from the pivot than the yolk is,wich makes the stick movements greater for the same head affect.]The only upside I can see to the pump setup is it's simplicity.[
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Hi Birdy and mford,Have you ever tried an overhead stick, you know, straight out of the end of the torque tube? Everything goes the opposite direction but there's not much to go wrong. 'Bout as simple as it can get.I think they're pretty popular in Qld.... you know, the Gykes.Hoges
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Birdy , yes have seen one of the Rosco set ups on your old frame that Dave Barker has built into an excellent gyro.Scott, never tried one but have seen a couple of photos of gyros that had an overhead set up as a back up in case of control failure. I,d imagine it would be hard to adapt in an emergency but a lot better than the feeling of helplessness of having no control.
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You could use a twin set up like a gyke on a permanent basis, put a twist throttle on the overhead stick so your hand has to be there and acts in concert with the control movements input by the joystick. Then if your joystick fails, no drama at all, you've been using the overhead stick all the way along... Mind you, the first dozen hours or so might be a bit risky, getting coordinated.As a failsafe, the rotor head should be set up for a default trim arrangement, where if you let go of the stick the gyro will trim to straight and level flight at a particular speed and sink if you lower the speed slightly or climb if you increase it, this also goes to PB's favourite topic, aircraft stability (I can see his eyes light up as he reads this - give us your dissatation Paul). This way at least you should get a breather if you know it is going to happen, loss of joystick then wouldn't relate to loss of control... hopefully.Cheers,Nick.
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G'day Mark. Technically, if there was no friction and both sticks had the same travel, then the rotor feedback would be the same. The difference is probably as you suggested or simply because the "parallelogram" stick has many more friction producing pivots to dampen the feedback. Incidentally, if you increase the friction in the pivots to reduce rotor movement feedback, then that movement is then transmitted to the airframe, which is felt as what is often referred to as "airframe hump" or "cabin hop"Tim McClure
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In my opinion, both control sticks (properly engineered) are as good as one another, however, the Brock "sissor" approach takes up far less "real estate".Pete Barsden
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I have a pump stick on my gyro and find it easy to use.There are a few points to consider with pump sticks.1) The stick moves up and down through the vertically plane.2) During turbulent weather the pitching motion of your gyro can add weight to your forearm therefore unintensionally inducing PIO.3)Also PIO can be further agrevated due to the sticks vertical movement.4) The stick has more rotor feel due to less moving parts, therefore less to go wrong.5) When setting up a pump stick I found if the sick is set up so in the trim position you can rest your rist/forearm on your leg it will help reduce the above, and aid in unintentioally lowering the nose due to fatigue.With the Rosco Push Pull system this is not a problem as the stick cannot move through the vertical plane.Regards Sam.
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Pete Barsden has nailed it in that the pump stick needs more space in which to operate under the seat. Most of us guys endeavour these days to raise the seat away from the keel to get some weight up, so that shouldn't be an issue. More space means you can see and inspect the system easily during a pre-flight. I like the pump stick because it does give the pilot important feed-back and it is simple with fewer wearing points than the others. I am weary of Roscos arrangement simply because of the number of rod-ends in the system and the added potential for some failure in the system. The scissor has caused deaths over the years apparently due to engineering and installation faults. Simply put 'I'm PUMPED'.Pete
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As Pete said, if it's engineered properly, both typs are adaquate, but its harder to engineere out the highly amplified leavereage of the pump, at the point just in frount of the knuckle. And if you do any serious heaving on it, thats where it'll let go. Roscos setup, tho more complex, is much stronger, but i gess this isn't a concern for most.Ignorance is bliss............but only till you realise you were.You can always get the answer you want, if you ask enough experts.
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I got Rosco to build me a pump stick some time back Birdy and I observed that he doubled up the thickness of the tube in front of the universal/knuckle until it comes to the bend. That should make it strong enough. My only concern with the system you are using is the rod ends themselves where the thread meets the shoulder. I have heard of a rod end failing when an attempt to loosen the lock nut was made, and although this may have been an old wives tale, it scares me enough to replace my rod-ends every other year. Not being a farmer from central Austalia, I would have to save up for a long time to afford to change all the rod ends in the 'Rosco' system.Pete
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Peter I have repaired a number of rotor strike gyros with roscos & other types of "parallelogram" controls & I am yet to see a damaged-failed rod end though I replace them in this case anyway and have a bag of S/H ones marked NOT FOR AIRCRAFT which my mates have found non critial agriculchural uses for Butch
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quote:Originally posted by SamLalso PIO can be further agrevated due to the sticks vertical movement.Actually Sam the pump stick works the other way around. If you hit an upsurge, the weight of your arms and the vertical movement of the stick tend to lower the stick, partially cancelling out the "upsurge". The same but opposite for a "lift".quote:Originally posted by PeteI got Rosco to build me a pump stick some time back Birdy and I observed that he doubled up the thickness of the tube in front of the universal/knuckle until it comes to the bend. That should make it strong enough.I think you will find that the material is double thickness to around the first bend and then triple thickness for about the first 6". Cetrainly over strength.Tim McClure
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"Actually Sam the pump stick works the other way around"Ya beet me to it Tim, i was guna say the same thing. But, of corse, this only works if you ain't choke'n the poor bastered to start with.Pete, with respect, a few years back i saw the very same rosco pump stick setup with the outer cracked compleatly round, the second 'layer' cracked along the same line 2/3s of the way round and the inner just starting to crack. I never thought there was that much stress at that point either, till i saw that.No, it wasn't my machine, but i didn't let him fly like that either.[from memory the machine had only bout 800 hours with no incidents or rotor strikes.]Ignorance is bliss............but only till you realise you were.You can always get the answer you want, if you ask enough experts.
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