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how firmly do you attach the servos?

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Old 05-14-2003, 06:56 PM
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mikenlapaz
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Default how firmly do you attach the servos?

I have read what appears to be differing procedures and need some more input. Which of following best describes?
1) Snug them down till screw shoulder just barely contacts the rubber grommet;
2) compress the rubber grommet (%'s are total thickness of both grommets), If so how much
a) 10% b) 20% c) 50%
3) contact the rubber grommet plus 1/16"

Isn't the degree of compression two sided? Vibration dampening and securing servo from too much flexing.

Share your thoughts, maybe I should have posted this in Beginners!

Additionally, when they get attached to balsa, with a ply backing, do you mount, remove, and then put anything lightly in the balsa holes like a bit of wood glue or CA to toughen the balsa?
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Old 05-14-2003, 08:28 PM
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MinnFlyer
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Default how firmly do you attach the servos?

Here's the correct way (although I only recently discovered this, and quite frankly, I don't do it. Nonetheless, this is how it should be done)

The little brass collar goes in from the bottom, and the screw is tightened until it meets the brass, so you can't over tighten the rubber.
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Old 05-14-2003, 09:30 PM
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Default how firmly do you attach the servos?

Geez I wish I could draw like that on the software. My drawings always look so bad I can't even begin to post them.

Anyway, that is the correct way. I didn't use the brass collar inside the grommet for years. I do use it now. screw the screw down tight on it. It works well. Keeps the grommet from coming out of the servo too.
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Old 05-14-2003, 10:14 PM
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George E.
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Default how firmly do you attach the servos?

ditto on the brass grommit

It's fool proof

And don't worry so much
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Old 05-15-2003, 04:22 AM
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mikenlapaz
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Default how firmly do you attach the servos?

MinnFlyer I would be interested in your method.
What you diagramed is Futaba's instructs as well, which I found this morning. Went out and measured and found that (2c) 50% of compression of both grommets is required for the screw shoulder to touch the grommet. Seemed like alot and just wanted to get feedback from experienced builders if it was considerably different.

geoharry just learning and would like to keep this first plane as long as possible. The forums are 99% of my contact with RC people that I can commicate with in English!

mike 1000 miles to the LHS
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Old 05-15-2003, 01:41 PM
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Default how firmly do you attach the servos?

It really doesn't matter that much. Just tighten the screws in them. I have put them in with servo tape too. It really doen't matter that much.
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Old 05-15-2003, 01:54 PM
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Default how firmly do you attach the servos?

True, remember I said that I really don't even do it that way, it's just what is SAID to be the correct way. I put the brass sleve in from the top, and tighten the screw until snug.

I think the idea of doing it their way is to prevent OVER tightening. That is to say, you don't NEED to make the screw touch the brass, the brass is more of a safety stop.
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Old 05-15-2003, 04:00 PM
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Default how firmly do you attach the servos?

mikenlapaz

I hope I didn't offend you. I surf RCU everyday trying to learn from other people's mistakes, I can't make them all

My point was, you can get by just fine doing a lot "wrong" in this hobby for a long time. Most stuff just isn't that critical. I never used the brass grommits until this year and never had a problem, but I use them now.

Have fun.
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Old 05-15-2003, 04:37 PM
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Default how firmly do you attach the servos?

Been doing it like the Pict sense 1981 with no problems yet!!!! knock on wood , except lately with Arf's I have had to back up all the wood servo trays with hardwood sticks to get enough thickness to allow more threads of the screw to grip(Man most Arf's wood trays are to Thin)

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Old 05-15-2003, 04:47 PM
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Default how firmly do you attach the servos?

Minnflyer says:
I really don't even do it that way, it's just what is SAID to be the correct way. I put the brass sleve in from the top, and tighten the screw until snug.
Actually, there is a reason why SOP is to put the grommet in from the bottom: the flared end of the grommet gives a large area to bear against the wood, whereas when the grommet is inserted from the top, the small end has minimal area and can penetrate the wood of the servo rail when the screw is tightened.

Still, you can get by with doing things wrong, but that is not necessarily right. There is so much that can go awry with the aircraft that we need to remove as many negative variables from the equation as possible.

FWIW...
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Old 05-15-2003, 04:55 PM
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Default how firmly do you attach the servos?

You're right Bill, and from now on, I'm going to install them properly.
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Old 05-15-2003, 06:16 PM
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Default how firmly do you attach the servos?

Hi,

To answer one of your original questions, I would not even think about trying to screw a servo directly to balsa.

In my opinion you need at least 1/4 inch of hardwood or plywood to make the screws secure, unless you are talking about a park flyer or something really small.

As one of the other posters has said, arf's commonly have 1/8 lite play for a servo tray, screws just will not hold for the long term with this arrangment. You need to double up with scrap lite ply or similar.

You can fasten servos to balsa and harden up the screw holes, but the screws will not hold long and will soon loosen and goodbye bird. It won't be a pretty sight.

HTH

Jerry
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