DS821 Servo Arm Rubbing On Canopy - HeliFreak
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Old 08-29-2007, 05:45 PM   #1
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Smile DS821 Servo Arm Rubbing On Canopy


I am building a Terx 600 and have installed the DS821 Servos that come with the DX7.

The servos are very deep and I have fitted them with the aid of spacers.

Here is the problem: I have put some heavy duty JR servo horns on the DS821's but with now I am getting some pretty serious rubbing on the canopy with the ball on the servo horn.

Mounting the balls on the underside of the horn is not an option because it will cause binding elsewhere.

I tried the smaller horns that came with the DX7 but they almost split open when the ball was inserted.

Regardless I want to keep the heavy duty horns on.

How can I adjust the canopy to stop this happening? I thought about extra washers on the canopy pins but I don't think it will be enough.

Thanks in advance for any help.
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Old 08-29-2007, 07:37 PM   #2
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You have to mount the balls on the backside of the arm and shim the servo out enough so the links won't hit the aileron arms. Mine almost touch, there's only about a half a mm between them and even after doing that it still rubs on the canopy but not as bad as if the balls were on the outside of the arm. You can also shim out the canopy mounts but I really wish they just made a wider canopy.
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Old 08-29-2007, 07:39 PM   #3
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Better be careful with those servos if you start beating on that thing.
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Old 08-29-2007, 07:53 PM   #4
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On my 9351s I mounted on the inside of the horn as well. Just had to trim off the remaining length of the horn.
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Old 08-29-2007, 08:17 PM   #5
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Measure the distance between the canopy mount posts on the heli. Pack the canopy full of foam, towels, rags, dirt, whatever to spread the canopy apart where it's rubbing. Tape the "ears" of the canopy back to the width you measured then take your heat gun (hair dryer will work if it's got enough wattage) and warm up the canopy. The fiberglass will relax a bit and allow the canopy to expand and gain some clearance.

I had to do this to mine. Now I've got a good 3/16 - 1/4" between my servo horns and the lid.

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Old 08-30-2007, 12:07 AM   #6
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So far the slight rubbing on mine has had no bad effect on the can or servos.
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