Where does the TO shake come from?

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AKar
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Re: Where does the TO shake come from?

Post by AKar »

Yeah, all this may not be immediately obvious, but a spinning wheel has a great deal of angular momentum. Often this spinning wheel changes its axis of rotation at a relatively quick rate when the landing gear unsprungs itself at the liftoff. This introduces gyroscopic forces that tend to oscillate with the spring steel strut and its natural oscillations, often adding to where it would be wobbling on its own.

A similar issue appears when the landing gear that retracts sideways against the orientation to the wheel is retracted. This is just one of the reasons why spinning wheels are usually to be halted automatically by a timely brake application early in the retraction sequence. When speaking of a bogey gear in a large airliner, the mass spinning at a very fast rate is in order of hundreds of kilograms - not a small gyroscope to speak of!

[Accidentally deleted this one when attempting to post a new one, hence the late edits... :roll: ]

-Esa
Last edited by AKar on 13 Nov 2020, 15:18, edited 4 times in total.

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DHenriques_
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Re: Where does the TO shake come from?

Post by DHenriques_ »

Oracle427 wrote: 13 Nov 2020, 11:13 Some 172s and 182s I have flown have a brief but noticeable vibration after liftoff. The mains and the sprint struts all start to wobble together and it magnifies the sensation. When I flew as a backseat passenger for the first time I watched the mains and was surprised at how much the sprint gear wobbled due to the wheel rotation.
I think your spell checker is changing your spring to sprint on you. :-)
Yes, the Cessna Spring gear could vibrate quite well. :-))
DH

Jarek
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Re: Where does the TO shake come from?

Post by Jarek »

These small wheels usually have 2 tapered bearings which need to be tightened properly together. If they are worn (so expected tension is lost) or not adjusted properly, then wheel can wobble when weight gets removed. Otherwise I don't see much reason to see this effect at scale.

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MkIV Hvd
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Re: Where does the TO shake come from?

Post by MkIV Hvd »

Jarek wrote: 13 Nov 2020, 13:56 These small wheels usually have 2 tapered bearings which need to be tightened properly together. If they are worn (so expected tension is lost) or not adjusted properly, then wheel can wobble when weight gets removed. Otherwise I don't see much reason to see this effect at scale.
Seriously?? Even though Scott experienced that exact behavior in the real Bonanza??? Interesting perspective......hhmmmmm :?

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Rob
Rob Wilkinson
A2A: Civilian Mustang, T-6, Bonanza, Comanche, Cub, C182, Spitfire, P-40, Cherokee, P-51 - VATSIM P4 and some other stuff...

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AKar
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Re: Where does the TO shake come from?

Post by AKar »

MkIV Hvd wrote: 13 Nov 2020, 14:21
Jarek wrote: 13 Nov 2020, 13:56 These small wheels usually have 2 tapered bearings which need to be tightened properly together. If they are worn (so expected tension is lost) or not adjusted properly, then wheel can wobble when weight gets removed. Otherwise I don't see much reason to see this effect at scale.
Seriously?? Even though Scott experienced that exact behavior in the real Bonanza??? Interesting perspective......hhmmmmm :?

Cheers,
Rob
If the wheel bearing tolerances were to cause such a shake, they would be outright self-destructing by the time of it.

-Esa

Jarek
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Re: Where does the TO shake come from?

Post by Jarek »

Yes, it feels strange. Bo is not supported by some pair of skis like 172 where wheel can wobble around - and it vibrates like crazy in locked position here. Personally I see it as some malfunction that cannot be fixed currently. Perhaps it should not be seen in a "like new" state with main wheels balanced and bearings properly adjusted. Obviously, there is no brake on the front wheel so it is excluded from the list of possible vibration causes.

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Oracle427
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Re: Where does the TO shake come from?

Post by Oracle427 »

These wheels are not balanced. You gets what you gets and any wear from use will just contribute to the character of the vibration. You always feel a little something.
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Oracle427
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Re: Where does the TO shake come from?

Post by Oracle427 »

DHenriquesA2A wrote: 13 Nov 2020, 11:44 I think your spell checker is changing your spring to sprint on you. :-)
Yes, the Cessna Spring gear could vibrate quite well. :-))
DH
Thanks Dudley, I fixed it!
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Re: Where does the TO shake come from?

Post by Jarek »

They are not balanced here in the model for sure, but it is not something that can't be done. https://www.aircraftspruce.ca/catalog/t ... lancer.php Flat spot landing can put the tire out of balance, but again this is a consequence, not a default state and tire wear is supposed to be simulated here. It is not visually but could be done this way.

Interesting read about this topic can be found here: https://www.aopa.org/news-and-media/all ... raft-tires

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Killratio
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Re: Where does the TO shake come from?

Post by Killratio »

DHenriquesA2A wrote: 13 Nov 2020, 09:49 Yes, the Hornet's gear system was designed by twelve insane engineers that management locked in a windowless room and denied them food and water for 30 days straight. I believe the same crew engineered the gear on the Cessna 210. LOL :-)
DH
:lol: :lol: :lol:

Supermarine did the same with their Draftsmen, I am sure. They also specified a minimum error rate of 2 per drawing!!!


Dudley, don't I recall you losing a friend in a Sea Fury or similar after tapping brakes on takeoff and fusing the pads?


D
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DHenriques_
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Re: Where does the TO shake come from?

Post by DHenriques_ »

Killratio wrote: 09 Dec 2020, 19:59
DHenriquesA2A wrote: 13 Nov 2020, 09:49 Yes, the Hornet's gear system was designed by twelve insane engineers that management locked in a windowless room and denied them food and water for 30 days straight. I believe the same crew engineered the gear on the Cessna 210. LOL :-)
DH
:lol: :lol: :lol:

Supermarine did the same with their Draftsmen, I am sure. They also specified a minimum error rate of 2 per drawing!!!


Dudley, don't I recall you losing a friend in a Sea Fury or similar after tapping brakes on takeoff and fusing the pads?


D
Charlie Hilliard at Sun and Fun in 96 in a Sea Fury. His brakes locked on landing and the aircraft nosed completely over onto its back killing Charlie.
D

flapman
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Re: Where does the TO shake come from?

Post by flapman »

CRJ-200
CJR-700/900
EMB-135/140/145
ERJ-170/190

All use an automatic brake application to stop rotation of MLG during the retraction sequence. None, by design, retract rotating main wheels into the aircraft. All have scrubbers for NLG tires. If that helps...
... I'm actually surprised the T-38 didn't use an identical system. I had assumed that was standard since forever.

My Bonanza is run pretty ragged (I got real lucky with the "used" mx option) so I don't know what it's like for you guys flying well maintained examples...

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Killratio
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Re: Where does the TO shake come from?

Post by Killratio »

DHenriquesA2A wrote: 09 Dec 2020, 20:32
Killratio wrote: 09 Dec 2020, 19:59

Dudley, don't I recall you losing a friend in a Sea Fury or similar after tapping brakes on takeoff and fusing the pads?


D
Charlie Hilliard at Sun and Fun in 96 in a Sea Fury. His brakes locked on landing and the aircraft nosed completely over onto its back killing Charlie.
D

Ah, thank you. I thought so. It is always sad when such a simple thing brings someone undone. RIP.
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