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Home✈️Aircraft🚁HelicopterCentury Radikal G20-30 N640 Hawk Predator › What now...........tail gear loosing teeth..woof woof
08-21-2008 02:14 PM  12 years ago
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Frank Bostwick

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Cincinnati Ohio

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What now...........tail gear loosing teeth..woof woof
Just got my Hawk Sport up in the air again but I seem to be having a new problem. I switched BACK to wire drive on the tail this time so I can start learning autos the cheap way. Also installed a JR7703d with the 8900 for control. I had also had some Woof woof vibrations in the air befor when I switched to the bigger Fshaft w/Tbearings but had that worked out.
The first flight showed woofing again and I lost about 5 teeth on the main gear, top side (tail driving gears). At the time I thought perhaps those were stressed from the last crash (TT on tail) and just broke on the 1st flight. I installed a new gear, checked my red dampers (took blade grips off head and reassembled) for good lube and turned down the gain on my gyro. Flew again

Had some woofing that came and went. Woofing, to me, is Heli vibrating port to starboard in flight and in hover. It'll come and go with no "this does it, that does it". This happened 2-4 times, each time Id land, turn down the gain a point or 2 on gear chnl (gyro gain)and try again. Last time I landed and called it a day. This morning I thought id check the main gear and sure enough 1 tooth is busted off and the others look like hell. 2 flight on this new gear.

Tail spins smooth as silk. no catching to be felt (BTW constant tail gear installed on this heli). whole drive train feels smooth on the bench. During rebuild, new main mast bearings, main mast, Fshaft, tail output, input, trans out shaft, tail gears, along with other parts.

I only have 1 gear left in stock.Planning on removing the boom and tail assembly, dis assembling the tail case and inspecting. At a loss here.....

Ideas, Please.
RIP ROMAN
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08-21-2008 02:29 PM  12 years ago
Frank Bostwick

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Cincinnati Ohio

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Just a quick add on here. This build I installed a machined clutch bell, balanced it. It has NO run out on the OD. It has ALOT of run out, up and down. Pulled it after 1st install and reassembled, bearings are seated, Im sure of it. Locked down with crank lock. Does not catch the clutch, spins free, clutch locks on spin up at normal RPMs, seems to work fine............Heli, when not woofing, flys smooth as can be, tracks fine, sounds better than ever. Spun balanced everything during build..........RIP ROMAN
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08-21-2008 08:30 PM  12 years ago
oldfart

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Vancouver, Canada

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1 - Woofing - you have the wrong definition - woofing is when your mainblades go in and out of trach at different times (usually when unloading - as in a descent.

What you are describing sounds like "wobble". This is related to the damping - the harder the dampers, the higher the rotor speed is needed to keep from the wobble.

2 - Crown gear missing teeth - this happens with any shaft drive system that has a constant tail drive auto system. As there is NO give anywhere in the tail drive, ANY hard landing that causes the tail rotor to come into contact with the ground or anything solid, will strip gears (that is assuming that the pins that secure your tail gears in position are properly secured by the allen screws that are screwed into the ends of their respective shafts.) This usually becomes more apparent with a CTD system when one starts to earn to auto.

So if you have a habit of occasionally landing a bit hard - I would suggest:

a) add more spacers between the landing gear struts and the lower mainframes to raise the tail further.

b) install landing gear that flex less, (e.g. the CN2243 l/g with a number of spacers) and/or hold the heli higher off the ground.
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08-21-2008 10:19 PM  12 years ago
Frank Bostwick

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Cincinnati Ohio

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Thanks for the info, but gears getting stripped, in flight. No hard not even close to hard landings. Happend on shake down flights..........Can see where tail bevel gear isa really diggin into plastic teeth. Gonna start on the tail but wondering if my clutch is slipping then catching........Only 2 things I can think of........RIP ROMAN
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08-21-2008 11:10 PM  12 years ago
oldfart

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Vancouver, Canada

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an you give some history of your Hawk Sport. Has to be a few years old - did you buy it new and build it yourself?
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08-21-2008 11:17 PM  12 years ago
beavis1

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New York state

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770 with wire drive = real bad
Wire drive with a heading hold is a bad way to go and in most manuals and gyro instructions is reccomended as a don't do. with the gain low on a say 401 you can get away with it many have but drive wear is definitly higher than what gyros were out when wire drive was standard.

Now the 770 is a mother of a hard stopper and hold, this will break that wire drive at some time and the spin up of the wire could easily be a culprit to taking out a main gear tooth not to mention stress on plastic tail gears.

I know you want to save on the TT durring practice but you can buy just the shaft material seperate and replace the dogbone and bearing easily.
This is just as cheap as wire drive and does not put you in a bad situation like you have now with the 770 and the wire drive.
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08-22-2008 12:04 PM  12 years ago
Frank Bostwick

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Cincinnati Ohio

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Old Fart, Ill try not to write a book. Bought it off ebay 3+ years ago, struggled and crashed alone the first year. Dust collector the next. Back at it 18 months ago. Found RR, my knowledge and skill quickly advanced. Current ability is solid FF,Good all orientation control, solid approch and landing (poor spelling) some inverted (2 times) Have crashed many many times.

Sim Time: lets just say if I had a nickle for every 5mins on the sim, Id be a very wealthy man. ALot. Good inverted sport flying, loops, rolls etc. My best sim skill is autos. Just starting inverted, flame out autos.

Building skills: Start by saying I run the maintenance department in a plastics plant. Built and repaired things my whole life. Busted alot of stuff too along the way.

My building skills and understanding have improved many times over since joining RR. My Hawk building skills and understanding went thru the roof after I followed the setup procedure written by SteveH in the century area. Torn down andd rebuilt this Hawk so many times I rarley need to look at the manual (but I still do). Last 6 rebuilds have flown great with very little tweeking needed on the shake down flight. In fewest words, at least comptent.

Current set up: New 3152s, OS37, stock century muffler, changing back to the 401/9253, A123 2s RX power, Dx7/AR700. Cool Power 30%, Arizona Reg, header tank, Maverick G5 550s (only because Im outa woodies).

Larger feathering shaft w/Thrust bearings, red dampers, machined clutch bell, all BB head parts, Constant tail drive system, Triple BB counter gear shaft, and Torque tube but not installed.
RIP ROMAN
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08-22-2008 01:11 PM  12 years ago
Frank Bostwick

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Cincinnati Ohio

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Pics of 1st gear and mounted gear. New pics of current set up in my gallery.

RIP ROMAN
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08-22-2008 01:15 PM  12 years ago
jetfixrguy

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Florida

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this is what I do, I have a good amount of stock.....
you can buy just the shaft material seperate and replace the dogbone and bearing easily
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08-22-2008 01:24 PM  12 years ago
Frank Bostwick

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Cincinnati Ohio

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I know I can get the shaft at HW, where can you get it otherwise? and how do you pin/fasten your dog bone? Im doing a shaft right now, planning on a pin and JB weld or other epoxy......Stock Hawk replacement is not pinned at all, dont like that no pin thing.....RIP ROMAN
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08-22-2008 10:57 PM  12 years ago
Frank Bostwick

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Cincinnati Ohio

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Removed boom and tail today. Tail assembly was correct, gears perfect, shafts straight. Only glitch was the white drive wire support (3 of them on a wire drive) was scooted down to the end of the boom. May have caught on the tail input but saw no indication it did. I didnt want to glue them (per manual) because I want to use the boom for TT again. (as if it'll live that long). Ended up gluing support closest to tail.
Moving this weekend so Ill make no more progress(?) unil Monday. I will switch back to the 401 combo since I know it worked fine B4. I can use the JR set on my Logo 10 which is almost done. If the problem still presents, the only other t hing it could be is the clutch bell.
Unless you all have another idea...............
Will update. if only for the record.
RIP ROMAN
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08-23-2008 11:51 AM  12 years ago
Ray Fernandez

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Guam (U.S.A.)

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Frank,

After seeing your pics, I remembered several years ago when I was flying the Hawk Sport, I was getting the same problem. I switched to a torque tube and that seemed to solve my problem. I think it had to deal with the back lash of the wire drive. I think someone else mentioned that already.
Ray Fernandez - GUAM
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08-23-2008 06:32 PM  12 years ago
Blade_Master1

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Canada

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It would be nice if Century at least silver soldered the dogbone to the shaft.

IMO soldering is better than pinning

If you decide to solder it use a small flame on your torch

Too much heat will weaken the tube. start by heating up the dogbone first then work your way around the tube until it is hot enough to solder.

I've got 1 tube done this way, so far so good (knock on wood)

.
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08-26-2008 04:41 PM  12 years ago
Frank Bostwick

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Cincinnati Ohio

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I just thought Id file an update. I switched to the 401/9235 combo and put in another main gear, along with dis assembly of tail to check it. (it was fine)
Spooled it up just now and every thing is fine as wine. Tried to get it to woof/vibrate and could not induce it. Just a shake down, FF F8s, nothing too hard but she did just fine. I am rusty on the sticks, so its time to get some tanks thru it!
As a side note, man a fully balanced bird flys much smoother and better, faster in all respects. I dont know if that can net you a head speed increase or if it was the CF blades but it sounded like my head was screamin' (in a good way) I landed twice to check the back plate because it sounded lean but it wasnt. Did seem more "twitchy", Just faster with all inputs, could be the gray paddles or even the new servos, thought they are only 3152s they feel alot faster than my ole 9202s (specs are not that differant).
Anyway she feels like a new bird!
RIP ROMAN
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08-26-2008 06:01 PM  12 years ago
Furious Predator

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Kitchener, Ontario, Canada

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Soldering the dog bone to the shaft will not work. its stainless steel and aluminium, solder just wont work with that. You MIGHT be able to braze it, but i think you would nearly melt the dog bone doing it.

even if solder would work, it isn't designed for that application, it would eventually fracture and fail.

the pin works fine.
Shawn
Team Leisure-Tech
Team HelixRC
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08-26-2008 06:57 PM  12 years ago
Frank Bostwick

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Cincinnati Ohio

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Why wouldnt you silver braze it and then pin it??RIP ROMAN
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08-26-2008 08:30 PM  12 years ago
Furious Predator

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Kitchener, Ontario, Canada

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does silver brazing get hot enough to melt the aluminium dog bone? im not too framiliar with the temps for brazing.

in eitehr case though, i havn't had any trouble with the pins. i know on the Trex 600 models, people have had to put a piece of heat shrink over the pin to stop them from comming out. but this doesn't seem to be an issue with century shafts
Shawn
Team Leisure-Tech
Team HelixRC
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08-26-2008 10:31 PM  12 years ago
Dilbeck

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Springdale Arkansas

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Guess Ive just been lucky, Never had 1 single issue with said dog bone.Clint
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08-26-2008 10:45 PM  12 years ago
Ray Fernandez

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Guam (U.S.A.)

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Guess Ive just been lucky, Never had 1 single issue with said dog bone.
Now you've gone and done it, Dilbeck. The heli gremlins are coming!!
Ray Fernandez - GUAM
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08-27-2008 05:24 AM  12 years ago
Blade_Master1

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Canada

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you can't braze it you will melt the aluminimum rod or at least weaken it

just use a propane torch !

as for the Dog bone it seems to be sticking no cracks

next time I have it apart I'll click a few pics

I wanted to wait and see if it will hold before I posted
So far so Good (knock on wood).

Dang now you got me wondering about it

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