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HeliProz . ZoomsHobbies . HeliHobby

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Century Hawk - Falcon - Raven - Predator > Hawk IV and main gear
 
 
jaws
Heliman
Location: New Carlisle, Ohio

Guys,

I am having a hard time figuring this one out. I am hoping someone can shed some light on it. I bought a used Hawk IV. There were some setup problems with it that I fixed. I have hovered it several times and have done one circuit around the field. About 3 weeks ago, doing some testing with quick changes to pitch to see how it reacted, I broke some teeth on the main gear. Just wrote it up as part of the improper setup and got another one. Century guy said he never heard of that happening.

Yesterday I had a landing where it just touched down and I shot it back up in the air - and again several teeth broke on the main gear. I didnt think i hit the ground hard or did anything abnormal like that. I am running a stock OS32 and head speed around 1700 rpm.

I dont know what I am doing wrong. There is absolutely no play in the main shaft. I can hold the head and shake the heli and there is no movement or slop. There seems to be an appropriate amount of gear lash with the tail rotor drive gear.

Any help is greatly appreciated.

-jeff
06-17-2002 Over year old.
 
 
sreuss
Senior Heliman
Location: Ontario, Canada

Hi Jeff,

I've done this to a hawk before too, however, I could trace it back to one of two things:
- ANY play between the teeth of the main gear and the tail drive bevel gear, or
- a previous landing that either the tail blades contacted the ground or were snagged in the grass while the main blades were at speed.

This is not a problem just with the Hawk. Indeed, I've gone through 3 $50USD bevel gears on my Vigor CS because of excessive play and/or bumping the tail blds at the end of pirouetting autos.

Set the gear mesh in question to have NO play at the loosest point. The tightest point should wear in a bit then. Also, some .1 or .5 mm shims to get the bevel gear a bit more forward (pressed into the main gear) will help accomplish this.

HIH,
Steve Reuss
06-17-2002 Over year old.
 
 
jaws
Heliman
Location: New Carlisle, Ohio

Thanks!!!

Steve,

Thanks - can always count on useful info from the Run Ryder guys.

On my flying yesterday, it is possible that I may have touched the grass with the tail blades but I didnt think so. I am ordering another main gear and will try all that you have suggested.

Is the main gear really that sensitive to tail blades hitting grass? Our field has slightly longer grass at the heli end and it doesnt seem to bother my other 2 helis. I will try and find a better place to land if that is the case.

-jeff
06-17-2002 Over year old.
 
 
replick
Heliman
Location: Fayetteville Arkansas

hey jeff,i have a hawk 4 too and have mowed the grass with my tail blades and have had no problems with the main gear.which teeth are you stripping,the tail drive or the inside teeth.
06-17-2002 Over year old.
 
 
ncostes
Veteran
Location: US

I bet it's the teeth above that mesh with the tail drive bevel gear. When I "landed" in a tree and busted main rotors and bent the boom the only damage inside the frames was one tooth broken off the main gear by the tail drive gear

But it was a pretty hard hit, struts broken, feathering shaft bent, flybar ruined, etc.
06-18-2002 Over year old.
 
 
jaws
Heliman
Location: New Carlisle, Ohio

Guys,

The tail drive gears on the top of the main gear are stripping. When I replaced the gear last time I made sure to check that there was no play in the main shaft - there was initially some play when I got the heli from someone else and stripped the first gear.

I did inspect the Hawk last night and found that there is some play on the tail gear and the tail drive. I can slide/push/pull the tail gear in and out slightly - maybe 1/32 of an inch or so. Would that be enough to cause the problem? Should i put a washer or something behind the tail drive gear to eliminate that play?

-jeff
06-18-2002 Over year old.
 
 
ncostes
Veteran
Location: US

So what was the consensus?
My tail/main gear have play - should I be worried?
Should we do what Steve said and put in a shim to tighten it up?
06-20-2002 Over year old.
 
 
jaws
Heliman
Location: New Carlisle, Ohio

Well I have put the shims in on the tail gear but am waiting for the new main gear to arrive in the mail. I will fly it this weekend and try to report back as to how well things worked. I added 3 small shims and now there is abolutely no play in the tail drive gear. It sure feels better but I dont know if that will help.

-jeff
06-20-2002 Over year old.
 
 
sreuss
Senior Heliman
Location: Ontario, Canada

Gear shimming... yes/no?

Hi All,

Gear shimming may or may not be 'necessary'. Depending on the flying you do and how well you keep the tail out of the grass, you may never need to shim the gears together. However, it is cheap insurance that bad things dont happen and that everything is functioning at as close to 100% as possible. If its worked for you until now without shimming, then roll with it. Next time you are taking things appart, consider shimming the gears for a proper mesh.

Finally, this is just an issue with this (and other) plastic fantastic helis. Note my earlier post, where I said that I've gone through a number of expen$ive gears on another heli because of a less than perfect gear mesh. As always, try to keep your heli at as close to 100% as possible, and it will be as relyable as it possibly can.

Cheers,
Steve
06-20-2002 Over year old.
 
 
jaws
Heliman
Location: New Carlisle, Ohio

Thanks Steve.

I have a problem with the grass length at our field where they make the heli guys fly. I am hoping a few other guys will start flying helis so that we can convince them to maybe setup a low-cut area or create a landing are or something. Trust me when I say I want to keep it out of the grass . It just seems weird how sensitive the hawk is to the grass since my ergo doesnt seem to mind it - but that has a different gear setup too.

Thanks for all the info. It sure feels a lot better - lets just hope it all works out.

-jeff
06-20-2002 Over year old.
 
 
ncostes
Veteran
Location: US

Yeah I hit the grass with mine sometimes too (blades are green and haven't had any problems.

What do you use to shim, just washers?
06-20-2002 Over year old.
 
 
jaws
Heliman
Location: New Carlisle, Ohio

My Ergo 60 came with a packet of really fine washers/shims. I just put three of those together and put them on the tail gear in the Hawk. By fine I mean about as thick as the tape in a VCR cassette. They are really thin and kind of slippery like they are made with some kind of lubricant on them.

I tried a plain old washer, but the thinnest one I had caused the gear to turn really hard and rub against the housing that the gear sits in. I imagine if you can find a thin washer that will work just fine. I also tried one of those washers that come with engine plugs and that was just a tad to big also. Caused some rubbing although the gear did spin pretty well just not completely freely.

-jeff
06-20-2002 Over year old.
 
 
oldfart
Elite Veteran
Location: Vancouver, Canada

shims

You can get Niftec/CMS shims (M5X7X.02 and M5X7X.05) at some hobby shops.

I only shim my Falcon SE because of the hard flight envelop that I use it for.

Phil
06-20-2002 Over year old.
 
 
jaws
Heliman
Location: New Carlisle, Ohio

Good news

Well I flew the Hawk sunday with all the new spacers and almost slop free gear setup and didnt have a problem at all. I even tried to get the tail rotor into some grass just to see what would happen. No problem - didnt lose a single tooth on the main gear!

So thanks to all who helped - looks like my problem has been licked.


-jeff
06-24-2002 Over year old.
 
 
Toddp
Heliman
Location: Spokane, WA

I'll be trying this also

I've stripped teeth on 2 main gears, the last 2 times I've been flying. I'll try the shim trick. Runryder really is a great source of information.
07-06-2002 Over year old.
 
 
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Century Hawk - Falcon - Raven - Predator > Hawk IV and main gear
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