Stick Shake -et al

[Mike Schallmann]

Ive been delaying talking about flying my gyro because Ive got some issues with the Dragon Wings -- Ive got a fair amount of stick shake -thats something I never had with my Vortec Blades. Ive strung them and checked the tracking--all seems ok --but it dont feel quite right yet --

I dont know how Ernie balances his blades --Im assuming that the blades are individually balanced and then put on the hubbar and then re balanced.

One thing I did notice is that the machining tolerances on the hubbar are not to close--for example the holes in the teeter block vary as much as .008 off center in both the fore and aft and vertical placement.

Another thing --if you measure from the Center of the teeter block hole to the tip of the blades -they are NOT equal -- one side is .065 greater in length . This is where I wonder about blade balance --if the blades are not balanced after they are put on the hubbar-- this could cause a problem---

I bought these blades used --they came in the original box and the hubbar was unassembled --There were no shims or any instructions--

The blades were wrapped in bubble wrap but there was a problem that I didnt discover until I took them out and began polishing them . All of the bolts for the hubbar were in a baggie -- well it broke open during shipment--apparently one of the nuts worked itself up under one of the blades and put a dent in the underside -its about 1/8" deep and say a quarter of an inch in dia -- structurally this isnt a problem --but it dosent look all that good.

If I cant get the blades running smoothly --I'll be putting them up for sale and going back to Vortec Blades --I still have a couple of McCutchen Hub around here...

Additionally I made two larger hubbars --I have NOT used them yet -as I am trying to resolve all issues using the original parts.

[Screw]

Screw-In

Hey Mike, I know your pain. I too bought a used set of DW for my KB-2 that the owner had disassembled the hub bar, and it took a while to get them right. As a matter fact the bolts holding the straps were slightly rounded from where the owner had iether disassembled or attempted to disassemble.

I guess we all take our chances buying used.

However, for the record, my new DW have no issues. Ernie builds them individually and test flys, and balances them prior to shipping or pick-up. Once balanced and test flown, I was instructed never to disassemble the hub bar.

How big is the hub bar and how much do ya want for it?

Screw-Out

[GyroRon]

you really should contact Ernie directly on this matter and then if no success come back to the forum for help

[C. Beaty]

Mike, I presume you have a beefed up mast. If so, whatever brand of rotorblade you use with a 2 ½” hub bar will shake.

The stiffness in-plane of the SkyWheels center section raises the in-plane resonance of the mast/rotor combination above the 2/rev aerodynamic input far enough to avoid excitation.

If you would like to experience some World-Class shake, mount your Flecks on a 2 ½” hub.

[BUD ONEAL]

I echo Ron, The forum should be the last line to step up to. Ernie is a very fair person but if rubbed the wrong way he can and will be a hell cat,I can,t blame him eithor.

[Mike Schallmann]

Im NOT bad mouthing Ernie --Im just stating the facts --I'll try and call Ernie--but this really isnt his problem --its mine --as far as the machining tolerence go -- I dont know if he makes them hinself or farms them out --but it is what it is --the tolerences are .008 off on the teeter bolts and one blade IS .065 longer fom the teeter bolt to the tip --thats a fact --

[MikeBoyette]

Mike,
Give him a call. He will try to give you a helping hand, if given the chance. He makes all hubs in house. What is the serial number of the blades? This can be located stamped on the brass tip weight of the blade. I am just curious. Also the blades and hub are a matched set they are balanced as such and can not be swapped out for a hub you made. They are balanced,tracked, and test flown as a set.

Check the aluminum portion of the hub and see if there a letter stamped there. If the hub is the original it should be letter matched to a letter stamped on the root end of the blade. My blades for example are marked A on one and H on the other. The hub is stamped with an A on one side and an H on the other. The A blade goes to the A side of the Hub and the H blade goes to the H side of the hub. Are yours marked in such a manner? If they are not then this is not the orignal hub and you will not be able to get them smooth unless they are rebalanced as a unit again. Also if there are no shims in the teeterblock then they probably need to be retracked.

Mike I hope this experience with USED Dragon Wings will not sour your opinion of them. They are good blades, they just can't be tinkered with like other blades. I hope this helps

[Doug Riley]

Mike S., make sure the hub came with the blades. I doubt that you can mix and match from different rotor sets without getting a mutt.

[Mike Schallmann]

Beatty ---By "beefed up" if you mean it is very rigid then my answer is no--The mast is totally unsupported --except at the clusterplate attachment.

[C. Beaty]

If your mast is an aluminum 2 x 2 x 1/8, almost any rotor can be shake free if properly tuned.

[Mike Schallmann]

The mast is a redundant 2x1--using 2 pieces to make a 2x2.
The only holes in the mast are at the cluster plate and at the cheekplates --all other attachments are clamped on. I tapped on the mast with a rubber mallet and it will easily flex (+/-) 1/16 to 1/8" . Also there are no rigid attachments to the mast -- EVERTHING is mounted with Rubber isolation dampers to allow the mast to flex...I think the problem is an imbalance issue Im going to make up a second teeter block that is absolutely true and see if helps --any input is appreciated--

I also thought about your statement on the Vortec blades on a standard 2-1/2 hub bar .. so here is a question --is this feasable --in addition to a 2-1/2" Hubbar you make a 3/8 plated that overlays and attaches to the hubbar --that is shaped somewhat like the McCutchen hubbar (ie cut outs for the teeter towers) --this would definitely reduced or eliminate the in plane resonance--feasable --?? --it would not be that hard to make--

Thanks

[C. Beaty]

Bensen used to claim that a B-8 had a “tuned” airframe and additional bracing would upset the tuning. He was never too specific as to just what he meant and violated his own mantra when going to double 1 x 2s for the mast.

My experience was that twin 1 x 2s always ran rougher than a single 2 x 2 but didn’t understand why at the time.

But the answer to your question is yes; a stiffener plate mimicking a Skywheels hub will definitely reduce/eliminate 2/rev shake. It should pick up the line of ¼” strap bolts; much of the flexing being in the straps themselves.

The attachment shows the expedient employed by Arthur Young to solve the 2/rev shake problem of the Bell-30, the precursor to the Bell-47.

Young stiffened the hub and root grips on the model 47 rotor so the strut rods seen above the rotor were no longer required.

[C. Beaty]

Another stiffening scheme that looks like it might do the job is the Averso hub (France).

[chuter]

So Chuck, if these stiffening devices are for the purpose of getting rid of the 2-per rev shake, how do they compare with a slider rotorhead for complexity, cost, etc?

I'm guessing the slider is the simpler solution or Ernie would have put some kind of stiffening plate on DWs.........?

[C. Beaty]

Whether to stiffen the hub or not is a difficult decision, Michael.

The 2.5” hub standard was established by Bensen something like 50 years ago and fits most any rotorhead.

Another issue is that stiffened hubs are helpful only where there is some flex in the mast. A truly rigid mast can only work with see-saw rotors when there is either a magic rubber bushing or a slider.

The best example of that is the Sparrow Hawk with its 2 x 3 mast. AAI was precluded from using an RAF style magic rubber bushing since it is patented and the slider is not. For them, the obvious solution was a slider.

A slider is inherently cheaper than a stiffened hub and will solve nearly any shake problem. It probably isn’t quite good as the magic rubber bushing due to break-away friction.

[giro5]

Don't know if you have talked to Ernie yet but I watched him balance my blades. The blades are put on the hub bar (and marked) and the assembly is put on a fixture that essentially has a teeter bolt so the assembly can pivot. Then a water level at the tip of each blade shows the relative positon and the tip weight on the heavy blade is modified till the blades balance. During the balance process you have to be mindful of air currents and people moving about as this disturbs the blades and keeps them moving and you cannot get an accurate reading with the water level. Or stated in another way the static balance of the blade assembly is very good when it leave Earnie's shop.

[gyropilot]

Hey Mad Man Mike,

Keep in mind you may also have an undersling problem (improper underslimg height) contributing to your stick shake. Have you used Cheuck Beaty's spreadhseet to calculate the suggested undersling and then compared that to what you actually have on your rotor head?

Regards,

John L.

[Mike Schallmann]

I know about undersling --I'm using the set up recommended by Ernie --I was out in my shop today and checked the balance -- unfortunately it was not up to my expectations -- Im NOT blaming anybody for this -- so I did a check and reblance -

Heres what I found -- I did a droop test --in a jig one of the blades was 1/4" lower than the other--

I could not detect any difference in the weight between the blades --

Heres what I did: I checked the balance and found one blade to be lower than the other by nearly 5/8" even allowing for droop difference it was still nearly 3/8" off--- in addition to the water tube I also used a machinests level on top of the teeter block -it confirmed the imbalance --

Next I turned the teeter block around on the hubbar--it lined up better (side to side and the .065 length difference between blade dropped to less than .010) and when In checked the balance --by both water level and machinests level --it was nearly dead on --it was so close that additional balancing would have been an excercise in futility.

Im also shimming the teeter block so that the teeter bolt is DEAD PARALLEL with the Hubbar.

Im going to try and get this setup airborn this weekend to see if I can tell the difference

[C. Beaty]

Mike, you haven’t said whether the shake you get is 1/rev or 2/rev.

The stuff you’re tinkering with only affects 1/rev shake. I hope you’re not trying to cure a disease you don’t have.

Teeter height and mast stiffness affect 2/rev shake.

I’m also curious to know how you can detect a length difference of 0.010” over a distance of 12½ feet. You must have a magic tape measure. The ones I own all droop over that distance and I can get any number I like depending on how much they are stretched; stretch until most of the droop is eliminated and the tape itself stretches. Steel, after all, is an elastic material.

Not that it matters; if the blades balance and are in track, they won’t shake from minor length variations. A length difference of 1/16” is only one part in 2400 or 0.04%.

Where did your blades come from, Mike? Maxie Wildes had an assortment of blades and hubs he was trying to get rid of a few months ago. If Maxie was the source, you may have gotten scrambled parts.

[Mike Schallmann]

Detecting the length is pretty easy --over the years I made up a set of "standards" (steel bars that are exact in length) mine range from 2'to 20' --those standards and a digital caliper give me a pretty good measurement. After I established the 12' mark is was pretty easy to use the caliper to get the final measurement--- from my limited experience it appears to be a 1 per rev shake --but I could be wrong -- the stick was bouncing all over the place-Im trying to get it calmed down so I'm working on one area at a time.

I bought a new rotor head from Ernie --I told him what I had and wanted to get a slider --he said it would be a waste of money for me and said a regular head would do --so I took his advice --I dont know what the issues are but I will work it out. Its flyable like it is but I really want to smooth it out--

I bought the blades from Dave Eisler -- they were to big for him he went back to 23 footers ---

THanks for al of your help !

[Mike Schallmann]

For the past two days Ive been flying quite a bit--anyway the stick shake is mostly GONE -- once I got the balance and blade pitch straightened out --there was very little shake left--It now moves about 1/2" (total movement) in the 10-4 position-- rotor RPM seems a little high @ 385 in cruise --slightly higher when I load it in a turn --these are with the 25' disc on an 800# AUW gyro--

I flew about 2-1/2 hrs today --would have stayed longer but some relatively heavy wind showed up--

[Fl90]

Hello, I fly a 2 1x2 mast also. I fly 23' DW's and can not string them adequately. My solution is to sling them, and they are glass smooth every time. The problem is, I hand start my blades. Even so, the difference in the ride makes it worthwhile. I don't think I could fly any other blades with my setup.

Happy with my DW's, Phil.