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Jr 821 Hv servos???

Old 01-02-2013, 03:46 PM
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Default Jr 821 Hv servos???

Did JR change the 821 servos....

I have read all the warnings about 821 servos and vibration, and not to use them in gas airplanes.. But now the new 1/4 scale super cub is all setup for 821 servos....

Also are the 821 hv servo the same but for high power??? meaning do they sheer the output shafts or was there a fix there.

John Redman shows putting those in the hanger nine p-47....

Why would Horizon show these servos in applications where your not supposed to use them.....

I like many here love the JR equipment but with as much bad press these 821s have I hope there has been a change....

Does JR make a good digtal servo with good torque for around the 50 to 60 dollar mark???


Old 01-02-2013, 05:38 PM
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Default RE: Jr 821 Hv servos???

It seems you have misread the HH warning against use above 1.20 size and the equivalent of that in gas is 20cc.

I've run seven of them in a 20cc powered Ultra Stick Lite with more than six hundred flights on it. After crashing it due to foolishly flying it during a fun fly with winds in the upper twenties where because it was early in the day, I let it get into the sun and on its back in crow mode and it was curtains from there.

I didn't hesitate to simply move the servos into a new Ultra stick Lite. I had to rebuilt the engine due to a bent crank... but none of the servos sustained any damage and I've now many flights on the new stick with those same servos from the first USL.

The 1/4 scale Cub is a 1.20 size or 20cc airplane so HH is not violating their own warning.

As to other servo options... there are plenty. For the same money as the DS-821, there is the non digital Hitec HS-645mg. A little more robust gears and a little more torque than the DS-821 but slower IIRC. I've used a bunch of them in 26-35cc planes.

Yes, the 821 is now available in a HV version for direct use above 6v but that doesn't change the 1.20 size plane rating unless I've missed something.
Old 01-02-2013, 06:26 PM
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Default RE: Jr 821 Hv servos???

DS-821's are great servo's. As staited above, in the right application.
As for the output shafts shearing. Locktite is the culprit. Again not suggested by the manufacturer. Add modellers, doing-one-better, now there is a warning added. Head this, we are back to a great servo.
When they started snapping shafts, they could be had at $10 each new as take outs from radio sets. I must have 18-24, never any problems. I too have a DLE20 powered RV-8 with these 2nd season ahead, no worries.


Thank-you Andy, I stand corrected.
Now, have I got some of the originals? Hmmm.
Old 01-03-2013, 09:03 AM
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Default RE: Jr 821 Hv servos???

Sorry but the original 821's sheared shafts w/o locktite anywhere near them.

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