AR-1 gyro manufacturer
- Oct 31, 2011
- Tampa, FL
- Total Flight Time
- 4000+ 472 gyroplanes. Sport CFI Gyro and Trikes
As I said Abid I agree shims are easy and precise, but it doesn't change the fact that the contact patch between teeter block and hub bar is totally lost and the strength of the hub bar is compromised.
Gerry Goodwin (mad max pilot) one of our retired blade makers used to track his blades in a whirl tower with shims, once he knew what was needed he machined the teeter block to suit and then send the blades out. His blades always flew smooth straight out of the box and rarely need any adjustment, just bolt them on and go. He is an old school proper machinist though.
I just think that maybe there is a better way, I like something like Brian's idea of a wedge shim. Maybe blade makers could supply there blades with an array of wedges to tune with if needed.
Maybe I'm worried about nothing but I doubt any engineer would agree that loading the hub bar on two points like that is a good idea.
Where are all the engineers?
The teeter tower first does not loose it’s strength with the hub bar when shims are used in any measurable way. The shim is squeezed like crazy due to proper torque and preload applied to the bolts holding the teeter block to the hub bar. No measurable loss in strength results on the hub bar because shim itself becomes part of the single torqued unit assembly. Thousands of hours on thousands of machines bear this out. Shims used are in a couple of thou range not size of a washer.
Regarding what Mr. Goodwin did, in my opinion wasn't completely useful because (though it is better than nothing) these swirling towers tracking does not do so much as soon as you put the rotors on a machine with its rotor-head and go fly with load in a representative speed range That is where tracking and balancing has to be done.
Remarks like the blades flew "smooth" straight out of the box are not an indication directly that they were tracked and balanced just that there was little stick shake. Two different things that may or may not be related. Measure the IPS with proper numbers and then you can use the numbers not just some feel thing. As long as the IPS is below a certain level and you are in acceptable range, you are ok. You may still have stick shake because of slop in the control circuit
Shims do exactly and precisely change the pitch of the blade that can also be undone precisely. It is in fact not trail and error compared to a half moon which is trial and error IMO. That is what you are doing so not sure what that point is about.