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Century Hawk - Falcon - Raven - Predator > Why are there so many bad Century posts?

hhart
Senior Heliman
Location: San Jose, CA

I had help several people on Century helis. One thing I dont like is the
tail pitch slider geometry. Totally suckieeeeee ! At one point, a buddy
upgrade from century cheapo gyro to Fut GY 501 and still not holding up. Upon a close inspection we found out that the tail pitch slider geometry is not symmetry. Watch out with the rudder ATV, otherwise
Y-yoke will self destruct.

07-27-2002 Over year old.

mike lewis
Senior Heliman
Location: northeastern AZ

spoke to soon

just yesterday i mowed the grass with my tail rotor and apon closer eximination I will have to admitt it could use some changes it is not as I might like I guess it upgrade time but to what? century doesn't offer up grades to the slider as an assembly I don't think, do they?

07-27-2002 Over year old.

Greg McFadden
Key Veteran
Location: Spokane Valley, WA

Buy a raptor 30 tail pitch slider assembly. you will have to use the bearings out of the century slider but that is easy. The only difficult part is that you must take the R30 brass sleve that slides on the rod and grind off most of the large end to shorten it. I ground mine down to where the flats for gripping no longer were in existence.

you must use the ball links off of the century pitch slider on the raptor. This improved things somewhat and when I put MS 97mm tail blades on it the tail locks real good (for a wire drive)

Do not worry about how the grips will look a bit odd after the mod (you will have to reset servo travel as this allows a lot more total blade travel) as the ball links on the balls on the grips will be about as far to one side (do it and you will see what I mean) as they can get but it does work well... from the look of it, you could probably buy a whole R30 tail with R30 grips and do fine.

The silence often, of pure innocence persuades, when speaking fails

07-27-2002 Over year old.

mike lewis
Senior Heliman
Location: northeastern AZ

greatful

Thanks Mike

07-27-2002 Over year old.

Inspector Fuzz
Veteran
Location: My own private Idaho.

Warlock...

Howdy!!!
Sooooo, your a mechanical engineer and you have "pored" over the design many times?? If they have so many problems, why did you buy 4 of them?? Personaly I find that a shave and a hot shower are good for my "pores"..

.
JEFF

07-27-2002 Over year old.

the Wasp
rrProfessor
Location: Vt

wire, tub or belt

The wire tail drive is good to learn on, and it's good if your happy with it !, but when I upgraded my Hawk SE V2 to a torque tube I could feel more power at the main rotor head !!

As for the belt drive,,,,
the heli pilots ""that I have talked to"" that have been flying for 20/25 years, they all told me that they prefer a tub drive,,,,,,, but it's all what an individual likes, thay said too !!

I think all helis should be made both ways, so one can have what he wants !!

Mechanically,,,
the Raptor has 5 pulleys for it's belt, the Falcon has 4 gears for it's tub drive,,, the Raptor has like 8 bearings for it's pully and tail shaft, the Hawk and Falcon has 6 bearings,,,, one is not easier than the other, and I have built them both,,, for a 50 or larger heli you better have something stronger than a 2mm tail drive !!,,, and a torque tube will not lag as a belt will, a belt can and will lag because of torque whip just like a chain on a motorcycle !!

If I had more money I would have all kinds of helis, both belt and tub drive !!!!,,, OOOooohh YYyeeeaa I would !!!

Jim

07-28-2002 Over year old.

jimmyhua
Veteran
Location: Guam

Digging up Old Dirt. warlock1174

You've probably already sold all your Hawk Heli's by now. But, hopefully someone here can learn from your mistakes. After buying & building a FalconSEv2, I'll be the first to admit, the kit isn't meant for any beginner to build. There are too many minor details that a new person can screw up.

Here's the detailed post you made in rcuniverse, colored in darkblue.

Known Hawk Issues.

Well, the first and most important is the drive shaft of the counter gear. This can be seen here: http://centuryheli.com/manuals/cn100xHawk4/step9_10.gif

9 times out of 10, there will be no problems with this part, however, I personally know several people who also frequent this site that have had the same problem I did. Namely, the two bearings that fit on the shaft do not always fit tightly. Over time, the shaft itself will begin to wear down from the vibration of the bearings that results from the loose fit. Feel free to remove this segment from your helicopter, and it will be interesting to note how many people are surprised when they see this. The problem with this, is that eventually, when the shaft wears down enough, it will cause the whole shaft assembly to slide downward, just barely enough to allow the gears to disengage. This in turn will cause a loss of rotor speed, and the engine will scream. This defect has been ACKNOWLEDGED by Brian Anderson who is a tech support person working at Heli-world.

Response: There's no way the counter gear could slip down unless, the set screw loosens, or the shaft breaks from wear. However, you could get so much wear that the counter gear will skip/slip. If you find the bearings have a loose fit, or the inner race doesn't fully set with the shaft. It's time to take it apart, and put a thin coat of blue locktite, wait for it to dry, then slide the BB's back on.

Secondly, the rubber dampers on the rotor head block. They can be seen here:
http://centuryheli.com/manuals/cn100xHawk4/step1_2.gif

Again, I am not the only one who had this problem...
But anyway, the stock rubber dampers work fine. The problem is the washer that separates the blade grip from the head. The washer actually wears down the dampers and eventually you get a little bit of play in the rotors. This problem has not been as frequent, because several people have told me that they noticed the washers were too small right away, and substituted larger ones in their place. I had called heli-world, and Mr. Brian Anderson advised me that he had the same problem, so he substituted bearings in their place. I took his advice and did the same, and ended up with an even worse problem.

The second problem is that some of the swashplate bearings were extremely tight in the plastic race. Again, I am not the only one to have had this problem, however, it seems to be limited to the Hawk 4. Apparently, the company that actually builds these machines had switched to a new milling device that allowed for just a millionth of an inch of error. But, the machine had been incorrectly programmed and produced several that were to tight. They realized this only after several hundred kits had been produced.

Mr. Anderson gave you some bad advice. Yeah, if the bearings are in the plastic housing are on so tight that whatever's in it doesn't turn freely. It's wrong. Call them on it.

I have no clue what's wrong the the current set of rubber dampers & washers. The washer has to be small, so that the Bearing rides on the washer on the inner race only. I think it can stand to be a little thicker though. That washer is there to keep the rubber damper from rubbing against the BB on the outside races. With the washer there, the dampers should only give friction to the inner races.

And finally, on the main shaft, as seen here:
http://centuryheli.com/manuals/cn100xHawk4/step13-1.gif
The mast stopper on the main shaft can, in some instances, wear away the plastic on the underside of the frame it touches. It seems to me that the simplest fix for this was to simply turn it upside down, and put a washer in between it and the frame.

Whatever you do, don't flip the mast stopper and slap a washer there. It will defeat the purpose of having a BB up in that area. Most likely, you forgot to put that plastic spacer that you see right next to the BB. You need to put that big plastic washer on top of the BB, and then stuff them both into the plastic frame.

That big washer pushes the BB down and ensures that the BB is held by frame by outer race. The mast stopper comes up, and contacts the BB on the inner race and holds onto the main shaft.

If you forget this, then the BB will slide up, the mast stopper will follow, and parts of the mast stopper will rub against the frame. You will get plastic all over the place, but it will fly fine.

Some others have mentioned that although the picture is correct, the instructions tell you to put the plastic spacer below the bearing. You will get alot more plastic bits this way.

08-01-2002 Over year old.

the Wasp
rrProfessor
Location: Vt

so buy a Raptor

Warlock, padilme01,,,

Don't think I'm being rude, but if you 2 think the Century helis have problems, go buy a Raptor and fly that for a while !!

Jim

08-01-2002 Over year old.

blazen
Senior Heliman
Location: California

WRONG WRONG WRONG !!!!!!!!!!!!!

Quote
>>>9 times out of 10, there will be no problems with this part, however<<<<

Quote
>>>>The problem with this, is that eventually, when the shaft wears down enough, it will cause the whole shaft assembly to slide downward, just barely enough to allow the gears to disengage.<<<<

Quote
>>>If you find the bearings have a loose fit, or the inner race doesn't fully set with the shaft. It's time to take it apart, and put a thin coat of blue locktite,<<<

WRONG WRONG WRONG !!!!!!!!!!!!! Using locktite to lock bearings to a shaft its kinda like using bailing wire and bubble gum to repair a broken motor mount in a car it might work for a short time >>>BUT there is a better way..

There is nothing wrong with the Hawks counter gear assembly !!! it’s a proven design that was used on the Rolls Royce of model Helis (Schluter)The only problem with this design is the unfortunate ability of the builder to overlook the obvious !! I can only attribute this to a lack building experience.

If you are experiencing galling on the counter gear shaft you have not properly preloaded the shaft bearings !!!! The counter Gear is designed to mate with the inner race of the lower bearing while the spacers under the pinion gear is designed to mate with the inner race of the upper bearing. when properly preloaded the Counter gear shaft will be locked to the inner races of the Bearings and forced to rotate with them

To preload these bearings follow the procedure outlined below.

1. With the assembly mounted on one half of the frame and while pushing up on the counter gear and the bottom of the counter gear shaft simultaneously apply downward pressure to the pinion gear.

2. while maintaining firm pressure tighten the set screw and test the assembly.

3.Test the assembly while it is in the frame by slowly turning the gear it should rotate smoothly with absolutely ZERO END PLAY and minimal friction.

4. If it feels notchy and hard to turn you have applied to much pressure and this will cause premature bearing wear.

5. If there is any end play you have not applied enough pressure and the shaft will spin within the inner races of the bearings.

It is as easy as that !!!!

On some early counter gear shafts the flat that the set screw tightened into was not long enough. In order to preload the Shaft bearings properly you must grind this flat longer to allow the pinion gear to properly put pressure on the shaft spacers...

Bottom line is The Falcon SE V2 is a great Helicopter. Century has taken the best designed subcomponents from various other helis then Improved them. They have done a great job of assembling a complete heli from all these subcomponents

1. The rotor head is a much improved copy of the X-cell head. The Locknuts are a vast improvement over the original locktited 4MM cap screws
2. The Tail is mostly Concept
3. The start system and drive train is Schluter
4. The Collective and Roll assembly is Hirobo

I’m tired of typing so I will address the other issues later

73’s
Blazen

08-02-2002 Over year old.

blazen
Senior Heliman
Location: California

flapping Resistance Modules..

Quote
>>>> Secondly, the rubber dampers on the rotor head block. They can be seen here:<<<<

One more issue.... Rotor head Dampeners SHEZZZZZZ how did we ever manage to start calling them Dampeners. They are not dampeners as there primary function is not Dampening they are not shock absorbers.. Until we as a group start understanding the function of the various components within our Helicopters and further use the proper jargon to identify them. We will never earn the respect of our Full size counterparts as They all think we play with toys and have little understanding of there operation.

On to the little rubber O-rings that we all call Dampeners. There actual purpose is to provide spring resistance to the flapping/teetering plain of the rotor head’s blade and spindle assembly. The amount of flapping/teetering resistant provided by the rubber insert is directly associate with the responsiveness of the rotor head. The amount of dampening provided by these inserts is minimal.. They should be called Rubber flapping Springs. Or flapping Resistance Modules..

73’s
Blazen

08-02-2002 Over year old.

the Wasp
rrProfessor
Location: Vt

So,,,

Does all this mean I can't call my model helicopter a chopper any more ?!!

Jim

08-02-2002 Over year old.

blazen
Senior Heliman
Location: California

Chopper is a world wide accepted Nickname...

Jim..

Dampener is not a nickname it is the officially accepted Name in model Helicopters that incorrectly describes a part and its function.

Calling the “flapping resistant spring” a dampener is like calling a motors crankshaft a Dampening spindle ...

Calling a motors crankshaft a Dampening spindle just because it is counter weighted to reduce vibration is incorrect. Just because some people might see this as an acceptable name, Reducing vibration is not the crankshafts primary function. Counter weighting the crankshaft just allows the crankshaft to do a better job

If an individual does not understand a components proper function how can we or why should we listen to there opinion on its failing’s or inadequacies.. This lack of understanding leads hobbyists to give out incorrect and possibly dangerous Advise.

I read a post somewhere in this form, Where a hobbyist Actually replaced the rubber flapping resistance springs with the radial bearings. Converting what was originally a two bladed floating axel / teetering rotor head into a poorly designed 2 bladed rigid rotor head. I say poorly designed because this individual did not bother to incorporate a flapping hinge or some means to allow the rotor blades to flap. It’s painfully obvious that this individual does not understand the basics of a floating axel / teetering Two bladed rotor head System. But this same individual believes that he has enough knowledge to point out all the design flaws in the same model helicopter. And then proceed to suggest improvements.

I was using this post merely as an example. I was not intending to belittle the individual who wrote it. In a roundabout way I was trying to show that most of the bad Century posts are from individuals with little understanding Of basic mechanical engineering. And most of the problems that they encounter with this helicopter are a result of their lack of understanding and inexperience. This is a very dangerous trend, model helicopters are inherently extremely dangerous and can easily take someone’s life. These models are not Toys and you must realize that you’re not only the pilot but the crew chief, flight inspector And ultimately the person responsible for it safe operation. If you do not understand the basic operations of the subcomponents within your model helicopter or understand basic building procedures such as preloading bearings how can you ensure the safety of the spectators while you fly your model helicopter.

73’s
Blazen

08-02-2002 Over year old.

blazen
Senior Heliman
Location: California

elastomeric dampers

I believe elastomeric dampers are Primarily used in Bearingless or Hingless Rotor head designs

In a two bladed floating axel or teetering Rotor head system this item is referred to a flapping spring or flapping restraint. While studying mechanical engineering my thesis involved rotor head dynamics To this day I will never forget the twenty minutes scolding I received from our professor when I incorrectly labeled a flapping spring as a dampener.

If in full size helicopters there are three major hub designs and are categorized as a
Articulated
Bearingless
hingeless

The hubs are divided into categories according to what type of flapping hinge, feathering bearing and lead lag hinge they incorporate. The Articulated hub is the most complicated mechanically it has bearings for the lead lag hinge, flapping hinge and feathering hinge. The hingeless hub has Ball Bearings on the feathering axes only. Lead Lag and flapping motions utilize elastic bending of the hub.

The Newest design and probably simplest and yet most advanced design is the bearingless Rotor hub... An example would be the one used on the Boeing/Sikorski Comanche . There are no ball bearings whatsoever in this rotor for Lead Lag, feathering or flapping. This Hub utilizes advanced graphite epoxy composites. Lead lag, feathering And flapping are all accomplished by elastomeric Flexing/Bending of the hub. Different rotor head characteristics can be obtained by simply very the composite utilized in the rotor hub.

Further more Flapping resistance alone has little to do with air or ground resonance. It is Flap lag coupling that is responsible for the vast majority of rotor induced vibrations..

In fact I believe that blade pitch instability caused be excessive Flap lag coupling also combined with a poorly designed main blade control system is what is responsible for the Craptors Susceptibility to the flight failure know as Woof and Poof

Since I am not a flight line Mechanic merely a retired prototype engineer. I am not up to date on the Slang jargon Mechanics use to identify components. but I can guarantee that elastomeric dampers is not a term you will ever see utilized by a competent mechanical engineer to describe the component that introduces resistance to rotor blade flapping within the flapping hinge mechanism of an articulated rotor hub

At this point I am getting tired of discussing rotor head dynamics. In my Professional career I worked in the prototype department under some of the worlds best modelers. I was lucky enough to be later named vice president in charge prototype development of the rotary wing division of the same major aircraft manufacturer. I have personally worked with high level US military officials developing new rotary wing concepts I carried this position until I retired..

73’s
Blazen

08-02-2002 Over year old.

Lift
Elite Veteran
Location: Houston, TX

Flapping heads

Gents,
While we are on the subject here can you guys in layman's terms explain to me the intent and purpose of the "flapping head" on the Concept 60 series helicopter. Why is Kyosho using this and what is it's attraction?

08-02-2002 Over year old.

blazen
Senior Heliman
Location: California

DDF Rotor head

The Concepts Rotor head is a DDF head or duel dampen fly bar system. Hirobo makes a similar head known as a triple hinged DDF rotor head. There are numerous advantages to this type of Rotor head in models. Hovering and high speed forward flight are two of those advantages.

Since each blades flapping Hinge is independent there is less negative interaction between each blade. The Blades are free to flap independently of each other. Unfortunately I do not believe that the DDF head works well in 3D aerobatic type maneuvers. Or for any type of acrobatics

The concept DDF head is a fantastic hovering Rotor head unfortunately it suffers from excessive ROLL PITCH coupling. This can be tuned out with a good computer radio but none the less the Coupling is still there and could cause sever problems in tumbling and rolling type maneuvers

Other then lacking a true Lead Lag hinge The Concept DDF head as they call is fairly close to being a true fully Articulated Rotor head. I thought at one time they even offered a true lead lag hinge as an upgrade ???

73’s
Blazen

08-02-2002 Over year old.

Lift
Elite Veteran
Location: Houston, TX

Thanks

Blazen,
Thankyou for the explanation. I find these various head designs interesting. I have a friend that flys one of those Concept 60 helis and it is a very smooth flier. Although, I thought that the flapping head might be a less than favorable design for 3D.

08-02-2002 Over year old.

blazen
Senior Heliman
Location: California

Lift
I agree there are quite a few really nice Model Rotor head designs out there. The old Schluter System 88 head was probably one of the first commercial and economical Rotor Heads that actually supported the Feathering spindle in the middle of the rotor head .Doing this preventing the Spindle from compressing both dampeners at once and improving the Rotors flapping characteristics.

As far as I’m concerned the Concept DDF head is really only good for use on a basic trainer.. Hovering and basic forward flight are where it shines. Anything other application and there are far better choices

73's
Blazen

08-02-2002 Over year old.

oldfart
Elite Veteran
Location: Vancouver, Canada

Rotor Theory

Blazen and Alexander,

Well done guys. It is good to see any helicopter forum have such intelligent and civilized discussions of such important issues as the dynamics of the rotor head. A gigantic improvement over the proliferation of posts by lesser knowledgeable people on whose penis is the longest.

Good explanations of the dynamics of a model's systems are a rare occurance on these forums as they seem to be more a network for spreading myth and smoke.

Thank you both for being part of this Century forum. An asset to all.

When I first started on the net many years ago (does anyone remember the old initil painfully slow telephone modems) it was with a desire to find such discussions simply because I read everything I could in the model helicopter press and found them extremely wanting. They never seemed willing to discuss or illuminate for their readers the pros and cons (practical, mechanical or dynamic) of any system used in any of the helicopters being tested. (Note: there are some exceptions e.g. the review of the Falcon SEV1 by Steven Reuss in one of last summers american Rotory Modeler issues and the recent review of the Falcon SEV2 by Stephen Bell in the July issue of the british Model Helicopter World magazine.) So it seemed natural to look for such discussions elsewhere....unfortunately, the net has failed also. These discussions are here, it is just that one has to filter through a lot of wives tales, blind brand prejudice, deaf penal pride and simple ignorance etc. to find them.

Well done guys, a welcomed intellegent discourse.

Phil

08-02-2002 Over year old.

Lift
Elite Veteran
Location: Houston, TX

Yep, thanks and let's talk more tech

Gents,
I know that Dieter Schluter had a book out years ago regarding some of the the technical aspects of RC rotor systems. I was introduced to a copy of his book when I first got started in helis last year but was already nose deep just trying to learn what a "curve" was let alone the dynamics of rotor systems.

Does anyone know the name of that book? For that matter, what are some other resources that would be beneficial to learning more about rotor systems that seem to miss the RC circles?

08-02-2002 Over year old.

IMZ Caliber
Senior Heliman
Location: Chesapeake, VA USA

actual technical name of dampners

Blazen you are correct by saying that the dampners, or as they are commonly reffered to as, are really springs. dampers are supposed to absorb and then stop without rebound. I believe the actual term for our "Dampners" is "Hub moment transfer springs".

08-02-2002 Over year old.

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Century Hawk - Falcon - Raven - Predator > Why are there so many bad Century posts?

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