Selecting the correct vibration motor

[alec_t]

To cancel any vibration will involve creating an equal and opposite vibration. Assuming the rotor is the main vibration source, would it help to redesign the heli to have two coaxial contra-rotating rotors?

 

[JimB]

As someone who has spent numerous miserable hours travelling in helicopters to and from work, your project should address:

The frequency of the vibration - need to accurately control the speed of the compensating motor.

The phase of the vibration - need to accurately set the vibration of the compensating motor in anti-phase with the vibration in the airframe.

The amplitude of the vibration - need to vary the out of balance in the compensating motor. How to do this could be a problem, you will need some means of moving the out of balance mass. This will of course affect the phase/frequency of the compensating motor as you will be altering the moment of inertia.

The plane of the vibration - there will be components of the vibration in the X Y and Z directions.

With these points in mind, particularly the requirement to adjust the amplitude, I think that the selection of the "correct" vibration motor is far from simply just a motor with an eccentric mass.

JimBs thoughts on helicopters:

They are uncomfortable.
They are very noisy.
The noise is obnoxious and very annoying. (Unless it is the noise of the helicopter which is coming to take you home, in which case the noise is sweet music!).

On one trip home in a helicopter, I noticed that the side of my face was irritating and itched like hell. Nothing would relive the itching, I had to endure this for 2+ hours.
Only as we were about to land at Aberdeen and the pilot reduced the power did the itching stop.
My face was resonant at one of the many frequencies jiggling that damned helicopter!

JimB

 

[JonSea]

I love the "safety briefings" I've had on US Navy helos: "When the helicopter crashes, it will flip over in the water...." Not if but when.

 

[unclejed613]

I love the "safety briefings" I've had on US Navy helos: "When the helicopter crashes, it will flip over in the water...." Not if but when.

reminds me of the 101st...
Q: why would anybody want to jump out of a perfectly good aircraft?
A: in the Army, there's no such thing as a perfectly good aircraft...

 

[gophert]

To cancel any vibration will involve creating an equal and opposite vibration. Assuming the rotor is the main vibration source, would it help to redesign the heli to have two coaxial contra-rotating rotors?

Twice the number of possible issues.

 

[large_ghostman]

Well it was a fun question, no one is seriously thinking th US navy lets a guy go ask questions about a helicopter with problems on a forum, some the guys here are ex military and learnt there thing from the military. I guess cutbacks could mean military training is now down on internet forums.

If i got to explain my joke about women then your under 15!

 

[unclejed613]

Well it was a fun question, no one is seriously thinking th US navy lets a guy go ask questions about a helicopter with problems on a forum, some the guys here are ex military and learnt there thing from the military. I guess cutbacks could mean military training is now down on internet forums.

If i got to explain my joke about women then your under 15!

IIRC the Army uses tank simulators for training, and the software for the simulator was derived from a game called "Steel Beasts" (the company that wrote Steel Beasts had a spinoff company that makes tank sim hardware for military training)

 

[large_ghostman]

IIRC the Army uses tank simulators for training, and the software for the simulator was derived from a game called "Steel Beasts" (the company that wrote Steel Beasts had a spinoff company that makes tank sim hardware for military training)

Yeah but the guys fixing the tanks are not handed a screwdriver and told to go join a forum to find out how to fix it .

Maybe they are, would explain why most our Nuclear subs dont work! That will teach them to join 'the other ' place.

 

[JonSea]

I don't think it's a bad thing to keep you eyes open for better methods of doing things, no matter what you are doing, and even asking for advice in relevant forums is ok. That relevant forum part is kind of important, where more than opinions should guide you.

But if a number of people illustrate that what you want to do can't work, you better step back and consider what they are saying. Don't get defensive and say they just don't understand what you are trying to do; consider if they are backing it up with concrete examples. If so, better re-think what you are proposing.

 

[shortbus=]

Yeah but the guys fixing the tanks are not handed a screwdriver and told to go join a forum to find out how to fix it

Weren't you here back when BillyMayo was a member? He was wanting to learn how to fix avionics here.

 

[large_ghostman]

I am not allowed to mention him, yes i was here. No it didnt go well and i ended up leaving for a bit.

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Thats all i am saying on him!

 

[unclejed613]

Weren't you here back when BillyMayo was a member? He was wanting to learn how to fix avionics here.

it seems there are a lot of different skill sets and interests here on this forum, you never know, there might be people here that have avionics experience. when i was growing up, i had a lot of books on the subject, but i'm sure what i learned about avionics then is very out of date today. after all, most of the NDBs have been phased out, LORAN-A has been phased out, and so has 4-course radio range.

 

[large_ghostman]

I had a visit to the engineering school at surrey university 2 years ago, they have a whole building and full sized wind tunnel for wing design alone. Two years ago they were working on wing designs for a new passenger jet, it was whispered that with new engine technology and the all important wing design, Sydney to London should be possible with a full sized Jumbo and no fuel stop!!

I honestly thought the guy was barking! Turns out that those wing tweaks they were doing made into the final version, and i know i mention this the other week, but that non stop flight they did was amazing! To halve the fuel use is some achievement. But then I look at old Haynes manual car repair guides from the late 1970's to mid 1980's.......

Cars doing 32mpg considered good for 1.6ltr engine lol, If you got that now you would look for a leak

 

[shortbus=]

it seems there are a lot of different skill sets and interests here on this forum, you never know, there might be people here that have avionics experience.

This guy wasn't one of them. But he was persistent, came back under many names after being banned. Always the same type posts though.

 

[large_ghostman]

I am not allowed to me mention him,,, But i remember the schematics from the Cockpit area really well! I think the funniest bit was when we all discovered he wasnt working alone and they were trying to get this thing repaired for a customer or something.

ACC didnt allow car electrics talk and there we were trying to convince him maybe he should at least learn how to use a scope before fixing a plane . I dont think the mods have been as busy since........come to think of it i dont think they been that busy at all lately

 

[gophert]

come to think of it i dont think they been that busy at all lately

You're correct. The mods just keep banning the higher volume (most helpful) posters or meddle in interesting conversations and diddle on about irrelavent factoids until everyone else drops out of the thread. Interesting place.

 

[large_ghostman]

You're correct. The mods just keep banning the higher volume (most helpful) posters or meddle in interesting conversations and diddle on about irrelavent factoids until everyone else drops out of the thread. Interesting place.

Thats unfair and not really true.

There is a post i am working on to show TCM the error of his ways, now considering the topic and the potential was argument, all they have done is mention a couple of times to keep it civil. I am one of the main offenders on ETO for saying what they think, and yet in the last couple of years i can only think of two occasions where I felt hard done by, considering the balance they have to strike i think they do a good job, Forums are not small one/two guy hobby boards anymore, they are full on marketing businesses.

The rules of engagement changed the moment the board was sold as a business, and most today are a business. You rarely see much mod bashing here, there is little to bash them over. And TBH you came from a place where there was a great deal more to moan about than here! Every other post at one time was stepped on if it didnt follow one or two peoples official lines. When Matt was made Mod i had concerns but they proved unfounded, he has been excellent.

The rest of the team do a good job as well, i am aware Jim is most likely to jump on me for a wrong doing, but equally Jim is one the first to jump in and help out when i need it. So it depends on your world view. The best bit is........This board makes money, probably a fair bit of it, and yet they do it free . Cant knock people working hard for no pay! Its like being given a free beer and moaning its warm.

 

[gophert]

Your second paragraph in post 55 was about mods at AAC.

I quoted your post 55 in my post 56. I, like you, was referring to mods at AAC.

Now, in post 57, you say I am not being fair. Do you say that because you forgot we were talking about AAC? Or are you defending AAC mods?

 

[large_ghostman]

Your second paragraph in post 55 was about mods at AAC.

I quoted your post 55 in my post 56. I, like you, was referring to mods at AAC.

Now, in post 57, you say I am not being fair. Do you say that because you forgot we were talking about AAC? Or are you defending AAC mods?

its 4:32 am

I can assure you i was not defending mods from other places, but i am full to the brim of a really bad cold and cheat infection (hence me not sleeping!!), dunno Gophert i think i simply just got lost confused! not what you call working on all resistors at the moment lol.

What your saying makes sense now, i dunno if i missed it or miss read it! my bad either way