ifixairplanes

My Feedback: (9)

Thanks. Being a rep. does have its perks
http://www.scoob-e.com/shuttle/

bdavison

My Feedback: (1)

First off.

Your saying that my not owning a nitro heli, means I dont know anything about aerodynamics, and because you own a nitro heli, you automatically know everything about aerodynamics.

Hmm.
Im sure the aerodynamicists at MIT and Stanford would love to hear an explaination of that. Perhaps they should discontinue their education, and go to Pathogens school of Nitro, where they can learn everything they need to know. Then maybe they could build a hughes 500 from a matchbox and some toothpics.

Secondly,
You do not know my background, or education, so dont presume to call me a moron.

Thirdly, do you know why your nitro bird has a single pin/screw/bolt hinge point. Because the educated aerodynamicist that designed your heli, had the forethought to know that uneducated folks would kill themselves tipping it over into the pavement if the blades didnt have some give. This however will still not lead or lag, because the centrifigal forces, dont allow it. The principles involved are far involved to post here, but....

If one blade on a dual blade system were to speed up, It would immediatly pull the other blade faster, causing it to also speed up and straighten out.

This is the last post I will put in this thread. If you still dont get it by now, I cant help you.

Pathogens

My Feedback: (1)

I was mearly saying that you, or anyone else that tries to strap down a heli or gives new commers advice to strap down helis are morons.

It doesn't matter what eductation you have, because its a dangerous practice.

dkshema

As for knowing rotor aerodynamics before posting replies, bdavison......

It is true that a two bladed, rigid rotor system won't go into ground resonance.

But, as many others here have aptly pointed out, our systems ARE NOT rigid rotor systems. They have a single bolt blade attachment, and the blades are free to lead/lag as they see fit as they rotate around the main shaft.

You have never seen a Concept 30 DX sitting on asphalt (silicone skid stops to keep it from scootin around) as the rotor system comes up to speed. There is a certain RPM where the heli begins a very nasty, undamped oscillation. You either get airborne immediately or shut it down and try again. It is a combination of the asphalt, the somewhat springy strut braces, and the ability of the blades to lead/lag. It only takes one blade to move slightly fore or aft when your heli is strapped down to rip it and whatever is in the near vicinity to shreds.

Never, ever, under any circumstances should someone tie their heli down while running it up. Sheer lunacy. If you can't track your blades while hovering, maybe you don't have the skills to fly one of these things safely.

Dave

jb_turner

bdavison,

Pathogens is absolutly right.. strapping down an RC heli is a dangerous practice. You may have some type of grasp of aerodynamics or full scale but we are talking about RC. Strapping down an RC heli is past the verge of stupidity at this point because you have been warned several times. You are inexperienced but in time you will learn.

corey11

Bdavidson

First off, yes, your are correct on the aerodynamics..But, you are missing a HUGE HUGE part of the aerodynamics. Going full throttle on the ground, causes massvie wake turbulence to be created from the lift created by the blades hitting the ground. This makes MUCH more stress on the helicopters rotor head. The air is recirculated back into the rotor system, makeing the air going over the blades un even. parts of the blades will have more lift in some areas, such as the middle of the blade will have more lift, and the tips will have less..And it will vary from each blade...can you guess what happens when there is a un even distrubution of air, on each of the rotor blades because of to much re circulation of rotor down wash?? yep, the blades are out of track. Amazing huh! So again, strapping the heli down, does NOT help, only worsens the problem.

Also, the tracking of a helicopter will NOT change, from in a hover, to flying around, doing 3d or anything. What will cause it is bad thrust bearings. Maybe we have discovered a myth..someone thought the tracking came out during certain manuevers, but in reality, the thrust bearings were bad..but to late for that, the rumor has spread(as you all can see)

One more thing, if you strap the heli down, go full throttle, why would you set up the tracking at full throttle, when it will some how change at a hover?? because like you say, and many others, your tracking changes during flight...Wait, why would we even track our heli if we know its going to come out of track in flight?? easy answer...BECAUSE IT DOES NOT

People need to understand, it is very STUPID to strap your heli down, and it DOES NOT change in flight!

ifixairplanes

My Feedback: (9)

bdavison, you are still referring to full scale. A head like on a huey will not lead or lag. You have some fullscale knowledge, this is apparent. But you still don't understand, our model heli heads are different. We have problems with FFF with our nitro helis if the blades are too tight or too loose because they wont be able to lead and lag properly. The single bolt is only tightened enough so the blades dont fall when the heli is held sideways. Thats the general rule of thumb I go by when setting the torque on the jesus bolt on the blades. I have fullscale knowledge as well as you, you could say I took a few classes (My RCU name isn't "I fix airplanes" because I crash alot.). Your explanations are correct for a fullscale heli, but it dosn't apply to our model helis. Once you step up to a nitro you will see what I am talking about when you examine the rotor head.

Sean

ChopperMike

This is SO wrong. Do you want to know how I know that? I had a vibration problem with an ECO 8 a few years ago. I determined the problem was due to some imperfection in one of the blades causing it to lag the other and throw off the balance. How do I know this? Because I discovered that by straightening out the blades and locking down the blades bolts VERY tight the problem went away. I was preventing the blades from leading or lagging. If your "theory" is correct, it would have made absolutely no difference because centrifugal force would have prevented the lag.

Centrifugal force prevents lead or lag? Yeah, right, if I run a headspeed of 10,000 RPM maybe!

rusirius

Wow... I had to debate rather or not I would even GET INVOLVED in this discussion...
I myself do come from the school of thought that strapping the heli down to do some throttle curve tuning, engine tuning, etc, is easier than doing it in the air (ESPECIALLY for a beginner) as well as CAN be done in a very safe manner. It DOES however deserve the utmost respect regardless of rather it's tied down or not.
I find that when people have "problems" with tying their helis down, it's almost ALWAYS because it was done incorrectly... First, our models DO lead and lag with the blades... Though it is slight... This CAN cause resonence... A lot of people attempt to strap their helis to a workbench, picnic table, the ground, etc... THIS is definately a bad idea. As had been pointed out, this causes a lot of very turbulent air to recycle itself into the rotor.
The only SAFE way to do this is to get the heli up into the air... (preferably over your head)...(I prefer the Ray's authoritative method of using a tall step ladder) This prevents it from being in ground effect as well as making sure no projectiles come hurling at you in the event of a failure.
You will find lots of people that have had bad experiences with strapping their helis down... Almost all of them you will find had it strapped in a position that put it in ground effect... You will also find lots of people that have been strapping their heli's down for years and years and have never had a single problem. As long as it's done correctly and again treated with respect, you will have no problems.
One last thing to note here. I have seen lots of posts of people saying that the heads aren't made to take that kind of pressure (generating lift and not being able to act on it)... Let me tell you first hand, when I'm doing 3D manuevers, the head is under FAR more stress than I'm EVER going to put it under while it's strapped down... If it can't handle being strapped down, I don't want it in the air.
Bottom line is this... Regardless of rather it's strapped down in your back yard, or flying around at the field, a heli deserves the utmost respect and should never be treated without the utmost of care. They CAN and WILL hurt or even kill people. Keep that in mind, and you'll have no problems at all.

duelist

My Feedback: (7)

ROFLMAO
Make sure to wear glasses and a hard hat




It wasn't safe then, and it isn't safe now. Get over it.

w.pasman

I once strapped down my heli to check the stuff. That was when I was not yet feeling comfortable with hovering.
Without foam it indeed vibrated too much and we cancelled the test run. Then we applied some vibration damping foam under the landing gear and the test run went without problems.
Just keep a safe distance (10 meters) just as with normal hovering. As they say a 1.5meter circle saw is something to treat carefully. Tie it down FIRMLY to something heavy. Do not apply too much pitch and no aileron elevator or rudder. Stop immediately if something abnormal is happening such as vibrations of strange noises (just as with hovering I guess??).
But let me add that once you are comfortable with hovering, strapping down is just a pain. Normal out of track conditions do not give any problems during hover.

heli-john

TOTALLY AGREE

heli-john

Something I omitted to mention was that I tend to use the head loaders when using my heli stand. In fact, I use the head loaders more than the stand. In fact, I recommend head loaders!!!!!!!!!!

Jugmaker

There seems to be some disagreement on the use of a test stand. But from reading the pros and cons , I think maybe I can make a rational decision. For me that is forget the test stand for running the engine.
Thanks to everyone for all the great input.

Jugmaker

heli-john

For me, there is always a piece of kit for a given need. A rotating test stand fits in somewhere.

Flyfalcons

They fit nicely in trash cans.

heli-john

Mine won't cos I built it and it was, and is, very effective. Silly question I guess but have you used one?

Pathogens

My Feedback: (1)

Everyone.

Please disregard everything that bdavidson has posted here.

He has no clue.

Carry on...

Charlie

I agree 100%. If your a beginner and you don't have someone to help you tune your heli, head loaders are definitely the way to go.

In my opinion, if you strap down a heli so you can tune it, you better give your head a shake and find another hobby, because this hobby is going to kill you sooner or later. It's plain an simply not safe, it puts way to much stress on the head. When you open the throttle full and have a +9, 10 or 11 degree pitch, think about how much pressure is on the head of that heli from it being held down. If you had a way to measure it, I'm sure it would scare yeah. The head on a heli is not designed for strapping the heli down, if it was, it would be in your manual under tuning your heli (and as we all know, it's not in the manual), and there is a reason for that, BECAUSE IT"S NOT SAFE.

Flyfalcons

No I have not. I was smart enough to get help from an experienced pilot when I learned how to fly my helicopter. We spent time in the shop setting up and balancing the heli. We spent the first few flights getting the blades tracked, engine tuned, and throttle curves set. All of this was done a safe distance from the helicopter.

B.T.D.T.

Jugmaker,

I just brought this from Home Depot on clearance for $20.00. Reg $29.99.
HD #649394.

Had to go to three stores to find one. Call Home Depot Online so they can track it by computer as to which store have it, and then call that store to verify stock.

These pics are not mine.

Pathogens

My Feedback: (1)

Thanks BTDT

But, this topic was for a run up sand..not a working stand...

B.T.D.T.

Pathogens,

This was a reply to Jugmaker. I know you guys turned this thread into strapping down heli's or not.

But the original post is label "Test stand"

And if you read it again:

"Hi, I have been looking for a stand to use when working on a helicopter.[/size] Maybe one with hold downs so it will stay steady while running engine. Something to carry to the flight field. Does anyone manufacture one?
Jugmaker

I saw this and I brought two because of the price and it's multi function and is light. This is NOT for strapping down a heli.

Pathogens

My Feedback: (1)

Alright.


Sorry.



Sensitive.

heli-john

I don't see why what you're saying precludes the use of a stand! It doesn't mean that using a stand means no help from experienced flyers and it doesn't mean that because you got help from an experienced pilot that you are smart (implying that others aren't). All it means is you got help and I guess we all got some of some kind of help at some early stage and mebbe those that didn't are cleverer than you think.
"We spent time in the shop setting up and balancing the heli. We spent the first few flights getting the blades tracked, engine tuned, and throttle curves set."
Helos are set up before firing them up anyway - well mine are as much as possible - so that's no advantage and there is always some setting up at the field, that's understood.
Also, the stand that is shown in the link allows the helo to rotate or can be locked solid. No one is asking for it to be used to thrash the bird to bits. That comes later when you have the skill.
Don't knock it if you ain't tried it.