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450 Pro GT, Main Gear Assy- Warped

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WearTheFoxHat View Drop Down
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  Quote WearTheFoxHat Quote  Post ReplyReply Direct Link To This Post Topic: 450 Pro GT, Main Gear Assy- Warped
    Posted: 22/Dec/2011 at 11:21pm
Hello all-
I recently purchased my first HK Heli, the 450 Pro GT, which happens to be the first heli I've built. Surprisingly, the build has gone really well (thanks to YouTube vids and TRex manual). Anyhoo, I installed the main/tail rotor gears and the gears are warped... BAD! It's so bad the tail gear slips out of drive about 1/3 of the main gear rotation. There's also a good 1-2mm up/down wobble.

I had read about this being an issue before I made the heli purchase, but I had not idea it would be so extreme. The kit was pretty nice- too bad the gear resembles an egg.
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  Quote hairykarts Quote  Post ReplyReply Direct Link To This Post Posted: 23/Dec/2011 at 6:41am
The up/down wobble is not uncommon and depending how perfectionist you are tends not to be a major problem.
No answer to the warped , but replace. May be a one off.
I must remember .... when inverted .... down is up and up is down .
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  Quote WearTheFoxHat Quote  Post ReplyReply Direct Link To This Post Posted: 23/Dec/2011 at 8:31pm
After looking at this more closely, the main gear is perfectly straight and true. It's the tail gear that is so bad.

If I go to my LHS and get an Align main and tail gear assy for a TRex450, it's going to fit.... correct?
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  Quote hairykarts Quote  Post ReplyReply Direct Link To This Post Posted: 24/Dec/2011 at 5:26am
Should do $$$$$$$ though
I must remember .... when inverted .... down is up and up is down .
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  Quote Heartstarter Quote  Post ReplyReply Direct Link To This Post Posted: 01/Jan/2012 at 9:00pm
don't tighten the bottom bolt. This warps the tail gear.
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  Quote WearTheFoxHat Quote  Post ReplyReply Direct Link To This Post Posted: 03/Jan/2012 at 5:11am
Here's an update...
Well, I went and purchased a T-Rex gear. Good news- It's pretty, blue, has fancy fan blades and it's perfectly round. Bad news- it still didn't fix my problem.

Now instead of partially grabbing the tail gear during a rotation, it doesn't do it at all. It's JUST missing it.

I came up with a solution and I think (hope) it's going to be OK. I've increased the screw hole sizes for the tail gear box by about 2 drill bit sizes. By doing this I can slightly slide the box forward to make the gears mesh. Obviously I'll need to watch this carefully and make sure everything stays in place.

I'm a little surprised there's no way to adjust the gear mesh from the tail to the main gear- either by adjusting the main shaft or by adjusting the tail.
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  Quote 2Doggs Quote  Post ReplyReply Direct Link To This Post Posted: 05/Jan/2012 at 11:26am
the key thing is not to over-tighten the bottom "Jesus" bolt. Rely insted on threadlock to hold it - otherwise the auto rotation gear will not run true.

With my first two HK 450 Pro kits and my first lot of spare main gears, all the gears were warped. I bought a pair of align gears, which ran true. My last couple of HK spare main gears have been fine, however.

Sometimes it helps to anneal the gears - put them in a pan of close-to-boiling water for a while, then let them cool down slowly.

In one of my HK 450 Pros, I had to elongate the boom block holes and slots to move the boom forward to get enough gear mesh - but make sure your boom block bolts are really tight if you have to do that.
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  Quote hairykarts Quote  Post ReplyReply Direct Link To This Post Posted: 06/Jan/2012 at 6:10am
This has been a problem on the 500, depending on where the lack of meshing is , you can shorten the boom , elongate the slots and holes in the frame ,and yes dont overtighten the bottom banjo bolt . You will need to replace this with time because of play , but so long as these things are checked regularly ( every flying day ) , you should be ok
I must remember .... when inverted .... down is up and up is down .
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  Quote JSantana Quote  Post ReplyReply Direct Link To This Post Posted: 05/Feb/2012 at 7:34am
Could you tell me if is possible to have problems later?? if I elong the holes and slots in the frame to reduce the distance between the tail drive gear and the autorotation gear on the HK450 gt pro.
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  Quote Memphis Eddy Quote  Post ReplyReply Direct Link To This Post Posted: 12/Mar/2012 at 8:59am
Tail gear mesh replace the tail gear with Align part and then tail drive gear. If that is a no go then start replacing all the aft parts with Align parts.
I matched up my Align frames with HK frames and both were identical.
It is not the frames.

Edited by Memphis Eddy - 14/Mar/2012 at 12:04am
Hk/Align45oPro/DFC/KDS/3GX/ZYX/9x/Dx8/7s/7/6i/9xr
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