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06-17-2006 11:53 PM  14 years ago
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starstructure02

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Trinity, Florida USA

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Problem with my HAWK PRO
Hello all I'm new to this forum but not new to Fling Helis.
The Hawk Pro is my first nitro copter I'm coming out of a Trex SE.
I found this copter to be very nice to fly and was a great choice for an entry nitro copter for many reasons. Anyway, I have found what I think to be a problem with the counter shaft part # HW3042.
After running about a gallon of fuel I noticed that the counter shaft was wobbling. I disassembled the copter to find that the shaft was completely worn out after only 1 gallon of running. The shaft was grooved by the top bearing so bad that it was half the diameter where the bearing road. I ordered a new shaft and replaced it. I checked the bearings and they seemed fine. I didn't replace the bearings but did switch the bottom with the top. I have flown the copter with no problems. Today after fling I went through my normal inspection and noticed that the new counter shaft is worn out the very same way. Again there seems to be no damage to the bearings only the shaft. Considering that this 2nd shaft went after only 4 tanks I have to right this off as a defect in the shaft. I was woundering if anyone else has had this problem and would tell everyone to check it !!!!!!!! The result of this shaft breaking would be nothing less then a bad crash.
I did contact Century and am waiting for a reply.
Mike
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06-18-2006 04:36 AM  14 years ago
oldfart

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Vancouver, Canada

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You will find a lot of Hawk flyers in the Century forum here on RR:

http://runryder.com/f48p1/

You may have a bearing with a slightly larger tolerance ID. I would suggest that you use a bearing sleeve type of locktight (like #620) between the shaft and the inside of the bearings.

This is a good practice on any shaft/bearing.
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06-19-2006 11:59 AM  14 years ago
Jimmi

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Southern Ca. U.S.A.

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And a light dab of oil will help too. And do as oldfart suggested Jimmi


They say its mind over matter but if you don't have a mind it doesn't matter
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06-19-2006 02:56 PM  14 years ago
Climax

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West London, United Kingdom

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I've owned a Hawk/Raven for a number of years now, and I have lost count of the number of times that I have replaced the counter shaft and bearings...

I should just say that your wear does seem to be happening very quickly, not sure why... Are you running a high head speed?

I've tried bonding the shaft to the bearings with retaining Loctite and removing the surplus end-float. Neither worked, in fact I found that removing the end-float made matters worse. I'd also suggest that you replace the bearings whenever you change the shaft, I found that using the old bearings just accelerated the wear on the replacement shaft.

When I was first learning to hover with this machine, I had a lowish head speed and shaft lasted longer. The wear only seemed to get bad once I could fly and cranked the head speed up to around 1750.

This is not going to be very helpful, but I think that the only way to permanently solve the problem is to increase the diameter of the shaft and then use bigger bearings to support it. Of course this is not easy as the bearings are held in place by the moulded plastic frames etc... I just learnt to live with the fact I'd have to replace the shaft twice a year.

I've always been surprised that more people here don't moan about this, as everybody I know locally with a Hawk has had this problem at some stage.
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06-19-2006 04:28 PM  14 years ago
oldfart

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Vancouver, Canada

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Hmmm...interesting Climax. My latest from this group is a Raven 30 that now has over 180 flights and when I had some bearing noise at the 168 flight mark, I checked all the bearings/shafts. The primary shaft and its' bearings where still fine.

The bearing noise was from the rear bearing of the OS-37. While waiting for the bearing, I have installed a Toki 40. I have 14 flights on it so far at "break-in" needle settings and am very impressed. It gives far better fuel mileage then the OS, while developing more power. It delivers a higher rotor speed (using the same blades) at the same top end pitch as the OS, so I have increased the top end pitch to keep the rotor speed at 1850.

I do agree with the fact that these shafts do wear (as do the bearings) and I also consider them to be maintenance replacement parts.(similar to start shaft support bearings on other systems, only not requiring replacement as often. I usually get 200 to 400 flights before requiring replacement.
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06-19-2006 05:33 PM  14 years ago
Breitenstein

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Denmark (Scandinavia)

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Did you locktite the bearings to the counter shaft? If not that's the reason the shaft wears out!
The bearing on the counter shaft need to be "glued" to the shaft with locktite (the blue one)!!
It's very important but sadly not mentioned in the Hawk Pro manual (It is in the Hawk Sport manual, and that can be downloaded from the Century site).
Jens
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06-19-2006 06:28 PM  14 years ago
Climax

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West London, United Kingdom

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The counter shaft wear only really got bad for me once I really started to load up the machine at high head speeds, and the same is true for the others I mentioned.

It's funny really as I love flying mild 3D with the Hawk on a clam day, for a little 30 it’s got a lot going for it. I've often though about selling it, but somehow I just can't do it...
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06-19-2006 09:21 PM  14 years ago
Gearhead

rrMaster

Vt

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I have to agree with Phil, in the 5 years I have been flying Century's 30 and 50 I have only had this happen twice on my 50, the first time was my fault because I used a bad bearing when rebuilding, after I started using red locktite on the counter shaft I never had the problem again..

Jim
Jim
Buzz Buzz Buzz
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06-20-2006 02:25 AM  14 years ago
Mr.Bowflex

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Toronto Canada

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I had the same problem as starstructure02 except I had to change the shaft and bearings every 4 gallons.

However, I have COMPLETELY SOLVED the issue on my upgraded Hawk sport by installing 2 extra bearings ( I think I used 5X11 bearings) to the shaft in-between the 5X13 bearings on the counter gear shaft assmebly. There is a recess for them in the frame and will drop right in with a nice snug fit.

I also made it so there is no vertical play in the shaft by extending the flat spot by carefull work with a dremal tool. I assembled it without any shaftlock or locktight on the drive shaft.

I have over 5 gallons of fuel through it with only a very slight sign of wear on the shaft.

I also run a Hyper 50 on CP 30% fuel, with Funkey 550 blades, 1950+ headspeed and + / - 14 degrees pitch 7.5 degrees of cyclic and do full 3D with it with no problems.
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06-20-2006 08:47 AM  14 years ago
Climax

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West London, United Kingdom

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Now that's an interesting idea! It will certainly provide loads of extra support for the counter shaft...

My hawk is due for a bit of a re-build, I'll try adding the 2 extra bearings.

Do you have any way of verifying the size? Don't worry if you can't 'cos I guess it's easy enough to check once the frames are apart, just it would be nice to be able to pre-order them...

Thanks for an excellent idea!
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06-20-2006 05:01 PM  14 years ago
starstructure02

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Trinity, Florida USA

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Thank all for the replies.
Although I'm not happy to hear that this seems to be a problem
(I would suggest that all owners check this NOW)It's a relief that this is not just my copter. I like the 4 bearing idea a lot I think I'll do this. I did lock tight the new shaft in and am noticing play in it already.

I am sending the worn shaft to century so they can see what’s happening. This is a factory assembled part and if there's a problem that needs a mod it really needs to be announced. Like I said on my first post as an entry level nitro flyer I am very pleased with the performance of this copter (not to mention the price) It would be a shame to have it crash because of this problem.
Thank again to all that responded,

Here is a rather blurry photo of the shaft but you can see how worn it is.
Mike

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06-20-2006 05:59 PM  14 years ago
Isaac F

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Panama Republic of Panama

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I am sending the worn shaft to century so they can see what’s happening. This is a factory assembled part and if there's a problem that needs a mod it really needs to be announced.
Century is aware of this problemo long time ago. From long time ago there have been post on many forums including RR about this problem.

Maybe the material of the shaft is to soft......Maybe you can make your own shaft of hardened steel.

Isaac
Speed of light is greater than speed of sound. Some people seem very bright until U hear them speak
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06-21-2006 01:35 AM  14 years ago
starstructure02

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Trinity, Florida USA

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Mr. Bow flex

Thanks for the info. I like the duel bearing idea I'll do it.

I was wondering if any could help me with the pitch / throttle curves. Or if anyone knows of a Hawk Tunning Site.
I have my Normal curve nice, just having trouble with the Idle up curves. I can’t seem to get the transition smooth.

This is for a .30 hawk pro with the .37 OS engine 550 Raptor Carbon blades and a Revolution .30 pipe
For now I’m running 15% Heli fuel a little on the rich side.

My Normal (Pitch curve) Throttle curve is as follows:
5-(12 degrees) 100%
4- (9 degrees) 75%
3- (6 degrees) 65% Hover mid stick
2- (3 degrees) 35%
1- (0 degrees) 0%

Right now my idle 1 curves are
5- (12 degrees) 100%
4- (6 degrees) 65%
3- 0 degrees) 40%
2- (-6 degrees) 65%
1-(-12 degrees) 100%

Any help would be much appreciated

TIA,
Mike
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06-21-2006 02:36 PM  14 years ago
Pistol Pete

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Seffner, FL

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anyone knows of a Hawk Tunning Site.
no...haven't come across any...only one close enought is

http://www.swift-tuning.com
~~Enjoying the hobby one flight at a time~~
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06-22-2006 04:36 AM  14 years ago
Mr.Bowflex

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Toronto Canada

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The high end pitch you run is actually irrelevant because it is determined by engine power (you may have already known that). The hovering pitch is also not that critical since the headspeed you run and the type and size of blade you have will change the hover pitch setting and the amount of lift needed to fly the model. If you are in around 5 degrees in hover your good.

With the O.S 37 (which I had at one point in my hawk) could not pull 11 degrees of pitch even on 30% nitro without the headspeed bleeding off in a full power climbout. If you are able to run 12 degrees of pitch on 15% either you run a realativly low headspeed, have it leaned out MAX or if you've got some kind of supercharged o.s 37 engine, let me know where you bought it because I'll go buy 3 .

As for your throttle curve, since your radio has 5 points (0, 25, 50, 75, 100 I guess) You will never get the headspeed to remain constant without "some" (I mean "some" as in a small amount) degree of change in head rpm through the throttle curve without:

A: An "exponential" feature on your TX that can be used on the throttle and pitch curves which allows it to look more like a "U" than a "V". That way when you transition from a hover to a steady climbout, the throttle servo wont have as much of a "drastic" effect on the throttle between say 50% and 60% (point 3 and 4) and 60% and 100% (point 4 to 5)

B. Or a governor.

As a side note, I don't run a governor on my machine with the hyper 50. Yes it does tend to overspeed the head "slightly" when transitioning from full power to hover or "zero" degree stick. But since I have a 10sx, setting up the throttle curve is easy with 7 points that can be placed anywhere on the curve and the exponential feature.

I am also 99.9% sure the bearings were 5x11 (the same ones used in the start shaft blocks on the main frame)
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06-22-2006 08:12 AM  14 years ago
Gearhead

rrMaster

Vt

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counter shaft bearings are 5x13..

Jim
Jim
Buzz Buzz Buzz
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06-22-2006 03:11 PM  14 years ago
Mr.Bowflex

rrApprentice

Toronto Canada

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Counter shaft bearings are 5 x 13
the 2 extra bearings between the 5 x 13's are 5 x 11's.
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06-22-2006 03:27 PM  14 years ago
Climax

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West London, United Kingdom

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I've now got two 5x11x4 bearings on order...

Thanks for the useful tip!
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06-22-2006 10:12 PM  14 years ago
Gearhead

rrMaster

Vt

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OK, had me scratching my head there guys LOL, I see, your going to add extra bearing between the two 5x13 bearins,, that should help,,

you know tho, I have always wondered if this wear on the counter shaft was from the up & down vibration rather that the shaft turning inside the bearing, I mean~ if the shaft turns the bearing should turn too,,, so make sure you remove all up & down play in the shaft, you can add a shim or along-agate the flat for the grear's setscrew..

Jim
Jim
Buzz Buzz Buzz
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06-22-2006 10:32 PM  14 years ago
Gearhead

rrMaster

Vt

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sorry guys,, it's such a good idea I just measured the extra frame I have here, unless Century has a couple molds that are slightly different the space in the frame between the top & bottom 5x13 bearing recesses is 10mm, err slightly less than 10mm..

Jim
Jim
Buzz Buzz Buzz
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