Wait a minute Fred!!! I agree, servo eyelets should be flange down and the Micro Fasteners washer plate screws are nice, but I really have a question. Please explain what you mean "it's the same thing as installing flat washers wrong way down.", because I am too dumb to know which way is up.
TIA
In the old days everyone installed them the way DR.1 does. Now the MFG recomend the other way around. For the beginner I recomend the new way. If you know what you are doing and pay attention it probably doesn't mater. I use the new way with the flange down then I screw it down all the way and then I back out the screw about 1/2 a turn. This ensures plenty of shock mounting. Sparky
In the old days when we actually used those crappy servo mounts, the eyelet was going into hard plastic and didn't matter. Now that most of use are mounting in wood, the flange definitely needs to be on the bottom.
Dr.1 Driver gets my vote.....flange up is correct.....its just common sense.
Did you take notice noone and also anyone else, as you crank that screw down you are distorting that grommet....it kinda gives you a clue that you are digging in it......the grommet needs a bearing area to prevent that. Flange up, no distortion......dont over tighten the screws. Very simple. I also respect your views.
Here's a few of the major manufacturers that would disagree with you.
Not pointing any fingers because I used to mount them the wrong way too...that is until I went to my first SWRA race and had to flip them over after the Safety Inspection.
Greg
snip
Mike,
Exactly! --
Jim L.
I've read most, if not all, of the replies and I think that some people are missing the obvious. If the screws are tightened correctly it really won't make a difference which way the brass insert is (he says with limited experience). Of course, if the "cup" is at the top, overtightening will force the uncupped end into the servo mouning surface. If the other way, then the screw mashes and distorts the rubber.
Common sense would suggest: Secure but not overly tight. Who wants excessive vibration going through the rubber mounts (which is why they are there) and, who wants to mash rubber mounts and/or the mounting surface? No matter which way you use the inserts, you shouldn't need them so tight as to introduce negative effects.
Maybe limited experience, but a lot of common sense, Raven.
If the proper eyelets are used with the matching grommets, and the screw is not overtightened, then it doesn't matter which way the eyelet is.
A word to newbies: Do not overtighten. When the screw meets the grommet or eyelet flange, another 1 - 1 turns is all that's necessary. The servo should still be able to "wiggle" slightly in the mounts.
If you mix brands of grommets and eyelets, you're on your own. I've found different grommet thicknesses and eyelet lengths from manufacturer to manfacturer. This will cause either over-squishing of the grommet due to a too-short eyelet, or a loose installation when the too-long eyelet bottoms out against the screw or servo mounting rail.
If you use the type of plastic servo tray that clamps the servo on the mount over little plastic pins, then this point is moot, because you do not use the eyelets at all in that instance. Dr.1 Driver "There's a Hun in the sun!"
Call me a newbie, just built my first a/c yet to fly it. However, I've flown others.......
The idea, one would think, is to take out the slack and ensure the servo doesn't move under normal loads. That's it, no more than that. If you want it any tighter you may as well soak the thing in epoxy.
Agreed, secure it and nothing more.
Simple, use grommets that fit and don't go bezerk on tightening. In general, for all subjects, the average Joe tends to overtighten fasteners. It's a hard habit to break but once you realise the truth of fasteners you cringe at everyone else.
Regards
Dr. 1 Driver, think about it this way -- the wood's softer than the screw head. If a newbie puts a screw in too tight with the flange up, the eyelet digs into the wood and the grommet gets overcompressed. However, if you've done it the opposite way and it works, fine. To each his own! :-)
Morris
Raven,
A/C ehh? --
Jim L.
The screws (micro fasteners or manufactuer supplied with servos) I use have a flange on them so the flange on the eyelet goes down - against the wood.
Red S.
I use JR and Hitec equipment and I have always put my grommets in from the bottom, as originally instructed 34 years ago. Before servo screws came with a built-in "washer," one put a fiber washer on top, between the screw head and the sharp end of the brass eyelet, then compressed it and backed off 1/2 turn.
On Sun, 25 Apr 2004, The Raven wrote
... and that is how I mount all of my wing servo's these days in moulded soarers and electrics. Nothing simpler .......
Hey... we all know there are guys that know more than the manufacturers of the equipment!
;-) -just pokin' fun.
I'm not that smart, so I try to follow the directions....
That should certainly shed some light on the debate. I used to roadrace motorcycles and learned that if the safety inspector required something done a specific way, there was usually a good reason for it (which was moot because if you didn't do it their way, your bike didn't go out onto the track).
Good flying, Bob Scott
Usually yes, sometimes no. At an IMAA event I attended with my first Dr1, the safety inspector refused to let me fly because my plane didn't have the "safety nut", as reqiured by the AMA. I did have an AMA-legal safety nut on my plane. What he called a "safety nut" was actually a jam nut system, as used on a lot of 4-strokes. It took a discussion with and explanation from the CD to convince him my plane really was legal.
Dr.1 Driver "There's a Hun in the sun!"
Too much time spent in critical applications, I spose . . . nuke plants, 4500 PSIG air systems, and so forth.
Common flat washers are stamped, and there is a smooth side and a 'rough' side, where the rough side is the one with the edges left behind by the stamping die as it passed through the bottom of the sheet of metal from which the washer was punched.
You can usually feel the sharp edges on one side and not on the other.
On larger flat washers you can see the edges. 1/4-20 and larger flat washers usually have a noticeable set of edges on one side - that's the bottom and that surface should be against the object being fastened.
Unless you have application-specific flat washers, e.g. the copper sort intended for brake systems' banjo bolts. or machined (Blanchard ground, usually) washers intended as spacers or as sealing surfaces in hydraulic systems, the common flat washers we all use have a bottom and a top, and the rough side is the bottom.
If a common flat washer is installed bottom side up in a torque sensitive application, the sharp edges can cause the fastener to be under-torqued because the nut used up part of the turning force in flattening the edges of the washer. The torque wrench reads the proper number, but the tension on the fastener is low because part of the torque went toward 'machining' the washer.
Installing a flat washer rough side down means all the turning force was used tightening the fastener, not straightening out the washer. It doesn't matter if the washer's rough side didn't flatten out perfectly, the fastener is still at the correct tension.
It's not a big deal in most situations. In the case of small fasteners in the sub-quarter-inch range, where optimum torque is in the low inch-pound range, it can make a difference between the fastener staying put or falling out.
And as we all know, fasteners that fall out of model airplanes do so when it is most inconvenient.
See the FAQ at
I've got both the torque tools shown on the referenced web site. The tools are extremely accurate and both have a break-point where the tool releases when the selected value is reached. I use them all the time.
Which way you install a flat washer in model airplanes is probably moot, since very few modelers own a torque tool capable of readings in the low inch-pound range, and probably over-tighten fasteners as a matter of course. I doubt that being short one or two inch-pounds will make much difference.
Still, there is a correct way to install flat washers, and I'd bet real money most folks are content just remembering to use a flat washer, never mind which way is up. Cheers, Fred McClellan The House Of Balsa Dust home.mindspring.com/~the-plumber AMA L180201 IMAA LM 090 NASA 6512 LHA 2 WB 233
Installing the eyelet flange down means you _cannot over-tighten the screw_. No guess-work, idiot-proof concept - run the screw down until it contacts the non-flanged end of the eyelet and you're done.
The grommet is _supposed_ to be compressed, but it's supposed to be compressed >correctly
Next time you run across that sort of nonsense, ask the 'safety inspector' to provide the reference because you couldn't find it yourself.
No such requirement in AMA Safety Code - it was removed a long time ago when it was pointed out that the requirement for covering exposed threads on the end of a crankshaft was ludicrous in view of the _propeller_ following those nasty exposed threads.
Some 'safety requirements' never will have been well-founded. Cheers, Fred McClellan The House Of Balsa Dust home.mindspring.com/~the-plumber AMA L180201 IMAA LM 090 NASA 6512 LHA 2 WB 233
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