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Gasser Model RC Helicopters > Pred. main gear - white dust

jschenck
Elite Veteran
Location: La Vista, NE.

I'm finishing up the first gallon of fuel in my Predator. I was looking over the heli this evening after another few tanks. I'm starting to do some flips and rolls, bumped up the HS to about 1600 and just flying it.

Now this picture looks pretty scary. I'm a bit concerned, looks like my main gear is getting some wear on it. When I first looked at this I spun the gear with my thumb. It was getting tight on every revolution of the pinion gear. After taking a look at things and twisting the starter shaft around a bit it suddenly freed up. Now the main and pinion run smooth to each other. I blasted everything clean with some compressed air and a toothbrush. I don't see anything too concerning on the main gear. The crown gear looks good.

Now my engine seemed to be running hot despite what should be rich needle settings - see the tuning thread GreyEagle started:
http://runryder.com/helicopter/t426698p1/

When I setup the mesh during the build I ran a strip of typical office paper through the gears and it did not tear but was accordioned up nice. I understand you want it just a little tight on a fresh build and the gears will set into one another. The starter shaft feels a bit tight to me.

What'd ya think? builder issue here? Don't really want to tear the whole heli apart but I don't want to tear it up either.

...yep...

04-23-2008 04:44 AM

FCM
Elite Veteran
Location: Malaysia

It may be the gear dust issue and tightness you described is loading the engine too much and raising the temperature. I'm not a Predator flyer but this may be useful to keep in mind.

Paul.

04-23-2008 05:08 AM

HOMEPAGE

jschenck
Elite Veteran
Location: La Vista, NE.

I think you may be right - I can't figure out why it suddenly would loosen up though. Perhaps I will need to tear it apart and just remove the starter shaft. It doesn't feel quite right.

...yep...

04-23-2008 05:18 AM

Billme
Key Veteran
Location: MS

If you can call me, I will be able to help you on this problem..
601-545-7633
Bill

04-23-2008 07:48 AM

jschenck
Elite Veteran
Location: La Vista, NE.

Thanks Bill - Probably this evening as I'll be tied up at work all day but this evening I'll be watching my daughter at her diving practice for a few hours (if that's ok?).

...yep...

04-23-2008 01:04 PM

Billme
Key Veteran
Location: MS

That will be fine..I may be out for a while tonight, but should be back by 9pm...
Bill

04-23-2008 05:49 PM

trunkmunki
Senior Heliman
Location: Bangor

If you find the issue, I am just curious as to what it is. I am considering ordering a predator.

04-24-2008 01:38 AM

Professorwiz
Veteran
Location: Livonia, Michigan - USA

Please do post any relevant info, as I'm in the middle (well start) of a Predator build.

Thanks!
Russ

Go that way really fast.. If something gets in your way.. TURN

04-24-2008 02:29 AM

HOMEPAGE

C.A.P.
Heliman
Location: custer park IL.

My predator did this when the main gear was rubbing on the carbon frame. Changed the brass spacer on the main shaft under the the auto-clutch. That brought the height back up, so the main gear did not touch thr carbon frame.

Also the reason this happen was my pinion gear was not lined up correctly, leaning back pushing the main gear downward waring the brass spacer down just a little until the main grear started to touch the carbon frame. Well anyways this worked for me

04-24-2008 04:17 AM

jschenck
Elite Veteran
Location: La Vista, NE.

I had a pretty good conversation with "Billme" about this. I can see that yes indeed the gear must have been rubbing against the frame. This makes sense to me since I didn't see too much wear on the teeth. After Bill mentioned this I did note that I can move the main gear up and down about 1.5mm or so. The inner part of the assembly (with the crown gear) does not move at all so this is the outside of the sprague gear floating.

I will be pulling the gear assembly out and performing some suggested fixes. As I get them done I'll document what I'm doing and report back.

...yep...

04-24-2008 04:35 AM

Billme
Key Veteran
Location: MS

Guys,

I have selected just a few people to date to make sure this fix is easy..
I'm planning on telling you all, I just wanted to make sure this is the way to do it...
So far, I can say I have found the quivering tail cause on gassers in general. The Predator is not the only machine that can have this problem..

jschenck can let you know... I have been hunting this for years, and it effects any heli that uses a inter sleeve on the auto clutch, wither its a sprag, or torrington...
Torringtons not using a inter sleeve is another ball game....

I will let you know when I can get the right parts, and the correct dimensions, on what to do...
Since I'm using new gasser pilots, it will ensure how to proceed as we continue the experiment

so far, so good..
Regards,
Bill

04-24-2008 05:13 AM

AceBird
Elite Veteran
Location: Utica, NY USA

Quote
I will let you know when I can get the right parts, and the correct dimensions, on what to do...

It may very well be the practice of using a clamp collar on the bottom of the main shaft instead of the provided collar that screws to the main shaft (taking the easy way out). The screw type shaft collar sets up the dimensional stack. You like to use the clamp collar because it lets you make up for something else that is wrong. The crown gear must sit flat on the aluminum hub. I think this is the biggest problem with most peoples assembly.

Ace
What could be more fun?

04-24-2008 01:05 PM

HOMEPAGE

jschenck
Elite Veteran
Location: La Vista, NE.

I'm using the screw on bottom main shaft collar and there is no play at all on the up/down axis of the mainshaft. Two issues are (from what Bill told me) 1. spraq bearing support and 2. the inner sleeve fit against the mainshaft.
I'm not 100% clear on the spraq bearing issue yet but I think it my understanding will become clear once I have it apart. The entire main gear assembly was pre-assembled when I got my kit.

My crown gear seems to hav a good fit, no issue there. I have done some pretty fast piro's and fast stops though I would not call them 'hard' stops. My 601 gyro is set in F3C mode and is running a gain between 37-45 displayed on the gyro. I do hear the tail blades ZIIIIPPP when stopping so I know I'm putting some stress on the tail drive mechanism.

...yep...

04-24-2008 01:26 PM

AceBird
Elite Veteran
Location: Utica, NY USA

Is the collar flipped upside down for the type of auto clutch used?

Ace
What could be more fun?

04-24-2008 01:41 PM

HOMEPAGE

Billme
Key Veteran
Location: MS

Here is the first problem...How the sleeve fits to the shaft... When you take the mast off the heli, take the sleeve out of the auto hub, by just turning it as you pull...Place the sleeve on the mast again, and put it where it supposed to be...
Try to put side loads, or try to rock the sleeve on the shaft...
If there is ANY play, you need to take it out..

Its a easy fix, you can use thin, to medium CA with a Q tip, and using a swirling motion trying to make it even as possible...Do a little bit at a time, and then put back on the mast, using a twisting motion..the mast will cut the excess ca out, making it easier to get the shaft on, plus take out the play...
The reason for all this, and I have found it even on a 600n Trex and other helis that uses a inter sleeve..Any slack will be movement during operation of the heli.. Even when all this is blocked up installed in the heli, it can still move...You can't move it, but the engine does, and when it does, it allows the whole hub to move 90 degs to the pin, or bolt, and take the slack up...

This can cause a very high frequency vibration, which can upset the sprag clutch, or a torrington using a inter sleeve, by rocking back and forth every revolution.. Sometimes you can see it, sometimes you can't, but its there. You will see its results. this has cause the TT bearing to come out of their holder, swashplate wearing out fast, ETC not to mention the power loss to the blades big time...
You have to pull the mainshaft, or mast, and do this outside the heli on the Predator...
BTW, I found this on the Trex, which was causing their torrington bearing to fail....
To be continued....

04-24-2008 02:26 PM

abwomack
Senior Heliman
Location: Houston, TX - U.S.

smoothest Gasser (Condor)

For those of you who have not met Billme, let me start off by saying that he really knows these gassers and is great guy. He gave me a few simple directions in how to make my condor tail smooth (and let me tell you it's a piece of cake) I don't know the part numbers off hand but I am sure that he will chime in and get that info out. The modification is simple, all you have to do is pull the main gear out, seperate the main gear from the crown gear and add an o-ring under the sprague clutch. and if the sleeve is not tight use a little CA to fix this. it only takes a few minutes and is definately worth the effort. I am on my 3rd gallon now on my brand new Condor and everyone that sees it is impressed with how smooth it is for a gasser and how it looks like it is on rails. Of course I tell them that it's the pilot not the Chopper (Ha Ha) but really it is a great machine which took very little tweaking from it's kit form. Feel free to Pm me with any questions. My tail went from kicking every few seconds to smooth and steady.

"Powered by AirThunder"

04-24-2008 03:19 PM

turbogti
Senior Heliman
Location: St. Andrew, Jamaica

I just checked my sleeve and there is a very slight play on the sleeve.

I'm going to clean it up and apply the CA as stated above

Any more info Billme?

EDIT: abwomack i would love to get some more information on this o-ring mod

****Predator Gasser SE - She's Ready to rumble ***

04-25-2008 03:45 AM

HOMEPAGE

Billme
Key Veteran
Location: MS

According to how many shims you have used for the crown gear hight, most will need 4 orings on the top, and 1 on the bottom...

You can use a spacer 4 mm long, and 1 oring on the top and one on the bottom, if you want to get fancy, just keep the width dimention of the spacer with the oring..The spacer will also have to go over the step up on the sleeve that fits the top bearing.The spacer will ride against the race of the top bearing..

The objective of all of this is to suspend the sprag off the floor of the oillite bearing, and sandwich it in from the top.

Make sure when you put all this in the hub, and before you put the oillite bearing in, that the cage keeper on the clutch will still rattle..Make sure it doesn't rub againt the flange on the wall of the hub at the top..You'll see it....

Finally, when you put everything together, the sleeve should protrude evenly with the oillite bearing... They both will rest on the spacer on the botttom mast bearing..If you need to adjust the grown gear, its best to get another spacer to the thickness you need...Do not use the old method of crown gear hight. You probably want have to do anything, I didn't..
Also, i'm stacking this on the sleeve so you can see it better, you will actually be putting this in the hub..

Regards,
Bill
Once everything is in place, you should not be able to move the main gear up, and down..If you can feel it move, but can't see it, then its done...
Make sure you clean the system good, and relube with transmission fluid...

04-25-2008 07:41 AM

Billme
Key Veteran
Location: MS

For those that don't have a internal bearing puller, you may can try this..
Get a strip of hard metal that want bend much , and stick it up in the hole, and position it over the hole on the inside..then you can take a smaller diameter shaft, and just punch it out from the top...Its not pressed in hard, so it want take much...All you need is a piece thats just longer than the diameter of the hole..

Hope this helps
Bill

04-26-2008 04:26 AM

jschenck
Elite Veteran
Location: La Vista, NE.

I put my order in with RHPS today and it's in the shipper's hands. I hope to be able to get the o-rings installed next week. Sounds like they are trying to source the right material to cut the 4mm spacer similar to the MinAir part that was discontinued.

Looking forward to getting this bearing supported properly and adding the foam baffling in the fan shroud. These two modifications should make a difference. I hope to finish off the lawnboy oil and switch to synthetic oil asap.

I also ordered a set of Thunder Tiger Red paddles. Bump the headspeed up and this machine should be coming to life!

...yep...

04-26-2008 04:43 AM

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Gasser Model RC Helicopters > Pred. main gear - white dust

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