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Model Forum / Radio Controlled / Air Models / April 2004"Install rubber grommets onto servo"?
The instructions for my Great Planes PT-40 are telling me to remove the servo arms and wheels from my servos and install the rubber grommets that came with them. What's a rubber grommet, and how do I install it? I have Futaba S3004 servos. Thanks guys, I'm really new to all this...  SignatureJoel Konkle-Parker Webmaster [Ballsome.com] E-mail [jjk3@msstate.edu] With each servo you should have a small plastic bag with additional servo wheels, 4 servo wood screws, brass eyelets, and the rubber grommets (they're the small black rubber things). They go on the 4 corners of the servo (along with the brass eyelets) to provide a small amount of vibration dampening for the servo. What your grommets look like exactly varies as the manufacturers change them over time. In this picture you'll see 3 examples of what your grommets might look like. http://home.swbell.net/smizwhiz/grommet_off_servo.jpg In this picture you can see that I've installed one of the grommets on one corner of the servo. Not shown in the picture is the brass eyelet that would then be inserted into the hole in the grommet. http://home.swbell.net/smizwhiz/grommet_on_servo.jpg Good luck. Jim > The instructions for my Great Planes PT-40 are telling me to remove the > servo arms and wheels from my servos and install the rubber grommets [quoted text clipped - 3 lines] > > Thanks guys, I'm really new to all this... To add a bit, the brass eyelet should be installed with the flanged end down. SignatureWill http://www.willstech.com http://snurl.com/2mn - Our eBay Stuff > With each servo you should have a small plastic bag with additional servo > wheels, 4 servo wood screws, brass eyelets, and the rubber grommets (they're [quoted text clipped - 22 lines] > > > > Thanks guys, I'm really new to all this... >To add a bit, the brass eyelet should be installed with the flanged end >down. Since the grommet bears directly on the wooden servo rail, the flange is not needed on the bottom. Install the brass eyelet with the flange up, to provide a hard bearing surface for the servo screw. This will keep the servo screw from digging into the grommet. Do not fully compress the grommet when tightening the screw, or you will have very little vibration isolation for your servo. Welcome to R/C. Feel free to ask questions, and keep us posted. Dr.1 Driver "There's a Hun in the sun!" >Since the grommet bears directly on the wooden servo rail, the flange is not >needed on the bottom. Install the brass eyelet with the flange up, to >provide a hard bearing surface for the servo screw. This will keep the servo screw from digging into the grommet. Do not fully compress the grommet when >tightening the screw, or you will have very little vibration isolation for your >servo. [quoted text clipped - 3 lines] >Dr.1 Driver >"There's a Hun in the sun!" I have to disagree here. If the flange is installed up then that allows the servo screw to compress the grommet to much, because of the nonexistence of a surface "area" of that side of the eyelet it just digs right into the wood. The flange at the bottom allows the screw to be tightened "just right" for all intents and purposes. I know what your saying DR1 however you and I both know to many newbies overtighten their servo screws and loose most or all of the vibration protection the grommets provide. rick markel My Model Aircraft Home Page http://hometown.aol.com/aileron37/index.html Wrong answer, DR. The brass eyelets go in from the bottom, with the flanges down. CR >>To add a bit, the brass eyelet should be installed with the flanged end >>down. [quoted text clipped - 10 lines] > Dr.1 Driver > "There's a Hun in the sun!" Agree > Wrong answer, DR. The brass eyelets go in from the bottom, with the > flanges down. [quoted text clipped - 15 lines] > > Dr.1 Driver > > "There's a Hun in the sun!" >Wrong answer, DR. The brass eyelets go in from the bottom, with the >flanges down. Not on my servos. If you use the proper eyelets that go with the grommets (there ARE differences from manufacturer to manfacturer), then it will be slightly shorter than the grommet is thick, allowing proper grommet compression before the eyelet seats against the wood. Dr.1 Driver "There's a Hun in the sun!" Here's a few of the major manufacturers that would disagree with you. http://horizon.hobbyshopnow.com/ProdInfo/Files/jrpm111.pdf See page 9 http://www.futaba-rc.com/faq/product-faq.html#q479 http://www.hitecrcd.com/Support/Manuals/eclipse.pdf See page 5 Couldn't find any info on Airtronics. 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 > Not on my servos. If you use the proper eyelets that go with the grommets > (there ARE differences from manufacturer to manfacturer), then it will be > slightly shorter than the grommet is thick, allowing proper grommet compression > before the eyelet seats against the wood. > Dr.1 Driver > "There's a Hun in the sun!" > Here's a few of the major manufacturers that would disagree with you. > > http://horizon.hobbyshopnow.com/ProdInfo/Files/jrpm111.pdf See page 9 > http://www.futaba-rc.com/faq/product-faq.html#q479 > http://www.hitecrcd.com/Support/Manuals/eclipse.pdf See page 5 > Couldn't find any info on Airtronics. 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.... > 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. 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 > learned that if the safety inspector required something done >a specific way, there was usually a good reason for it 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!" >> learned that if the safety inspector required something done >>a specific way, there was usually a good reason for it [quoted text clipped - 5 lines] >of 4-strokes. It took a discussion with and explanation from the CD to >convince him my plane really was legal. 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 >No such requirement in AMA Safety Code - it was removed a long time >ago I did not know that, Fred. Thanks! Looks like I need to go back and read the AMA codes and manuals. It's a good point, too. At 50 mph, what does it matter if the solid metal thing that hits you has a radius or not? Especially since, as you point out, there's a 12" meat chopper about a half inch behind it. Dr.1 Driver "There's a Hun in the sun!" >>> learned that if the safety inspector required something done >>>a specific way, there was usually a good reason for it [quoted text clipped - 25 lines] >LHA 2 >WB 233 At my field, a flyer once got a precise 1/4" hole punched through his shin bone by an exposed prop shaft. He was instructing a new pilot, (but not with a buddy box) and standing slightly behind the student. On takeoff, the student suddenly got crossed up and veered directly at himself. At the opportune moment, he jumped OVER the speeding aircraft, avoiding injury. The instructor behind him wasn't as quick, or so lucky. He spent a few weeks in a cast. To my knowledge, there wasn't any damage done by the PROPELLER. A spinner may have made a difference (as well as a buddy box setup). In Dr1Driver's IMAA case, I agree that the safety inspector was wrong in requiring a JAM nut...calling it a safety nut. The IMAA Safety Review Form only requires "PROPELLER - secure (check for cracks and damage)" The CD properly settled the disagreement. And Fred is correct, it's no longer in the AMA Safety Code. The IMAA Safety Code only references the AMA Safety Code. IMAA events are not "Competition" events, but all IMAA events ARE also Sanctioned AMA events, and the AMA Contest Director's duties are spelled out in the Competition Rule Book. ("General Information, All Categories" page 1): AMA SANCTIONED EVENTS AMA sanctions contests, fly for fun meets, demonstrations, and other flying events. "In order to effectively oversee conduct of an event, the CD is granted specific authority relating to organization, rules, and safety. In addition, the CD at an AMA sanctioned event has the authority to perform safety inspections of any equipment and to prevent any participant from using equipment which, in the CDs opinion, is deemed unsafe." >Next time you run across that sort of nonsense, ask the 'safety >inspector' to provide the reference because you couldn't find it >yourself. You ASKED for it.... ; ) So.....ludicrous or not, here's where that "Safety Nut" rounded spinner requirement is still in the Competition Rulebook, as applies to all R/C events, and left to the discretion of the Contest Director. (Similar sections appear in Control Line events) RADIO CONTROL, GENERAL (FOR NONSCALE EVENTS) 1. Applicability. In addition to the following General Radio Control rules and the specific rules for each radio control event, radio control model aircraft construction, flying, and competition are also governed by the rules of the following sections: Sanctioned Competition, Records, and General. Although the following general and specific rules primarily govern competitive activity in AMA events, it is strongly recommended that in the interest of safety and consistency they be followed in all radio control activity. RADIO CONTROL SPORT SCALE (SPORTSMAN AND EXPERT) For events 511, 512, 513. 2.4. All planes entered must have rounded prop spinners or some sort of safety cover on the end of the propeller shaft (such as a rounded "acorn nut"). Also, for Scale static judging, see last sentence: 5.5. No changes shall be made between judging and flying which alter the scale appearance of the model except as noted below. b. The propeller spinner used in flying must be the same size, shape and color as the one presented for scale judging except that it may have a different number of cutouts appropriate for the flying prop. The nose of the flying spinner may be rounded to comply with the safety regulations. RADIO CONTROL PATTERN For events 401, 402, 403, 404, 406. 6.1.The Contest Director at an AMA sanctioned event has the authority to perform safety inspections of any equipment and to prevent any participant from using equipment which in the Contest Directors opinion is deemed unsafe. 6.5. All planes must have rounded prop spinners or blunt faced hubs such that no propeller shaft protrudes. Rounded devices shall have a radius of point not less than three (3) millimeters. Also: AMA's website publication 508 "Safety Comes First" also mentions: "12. All model must comply with AMA safety requirements (rounded spinners or prop nuts, no metal props, no knife-edge wings, etc.)." Darrell Anderson Montana >>Next time you run across that sort of nonsense, ask the 'safety >>inspector' to provide the reference because you couldn't find it [quoted text clipped - 5 lines] >to all R/C events, and left to the discretion of the Contest Director. >(Similar sections appear in Control Line events) No, I didn't ask for it. It's been in the AMA Competition Regulations ever since it was removed from the AMA Safety Code. Alas, IMAA events are not subject to AMA Competition Regulations by fiat : IMAA does not hold competitive events. Do note that the general section of the competition regs does not mandate anything with respect to non-competitive events, it only recommends the general section be followed. Moreover, IMAA and AMA have gone their separate ways with respect to safety. AMA invented the Experimental Class for models exceeding 55 pounds dry weight (modified last year from an absolute 55 pounds). Other than that class, AMA does not expect any particular scrutiny of models in general except as may be found in the competition regs for a particular type of event. AMA doesn't appear to think a model weighing 54 pounds 15 ounces needs any inspection at all. It's that last ounce that's the kicker. IMAA went one step farther, and rendered their own safety inspection worthless by allowing the pilot/owner to do the inspection. Even I can spell conflict of interest. IMAA's participation is limited to signing the form as being accepted, period. IIRC, the argument was that by removing IMAA safety inspectors, IMAA could not be assigned liability. Since IMAA events are not subject to AMA Competition Regulations, the requirement for safety nuts and spinners is not applicable. As for the gent only getting a hole punched in his shin, I'd say he was extremely lucky. He could have been hit by a spinner-equipped model and had an excellent chance of that spinner re-directing the model and thus angling the prop blades into his leg. What's ludicrous is the notion that an acorn nut or a spinner will prevent the business end of a model aircraft engine causing bodily injury. Relying on inane "safety" measures always will have been a bad idea. Cheers, Fred McClellan The House Of Balsa Dust home.mindspring.com/~the-plumber AMA L180201 IMAA LM 090 NASA 6512 LHA 2 WB 233 Eyelet actually goes in from the bottom. At least that is what all the instruction books that came with my radio gear advise. Gord Schindler MAAC6694 > >To add a bit, the brass eyelet should be installed with the flanged end > >down. [quoted text clipped - 10 lines] > Dr.1 Driver > "There's a Hun in the sun!" > Eyelet actually goes in from the bottom. At least that is what all the > instruction books that came with my radio gear advise. [quoted text clipped - 19 lines] > > Dr.1 Driver > > "There's a Hun in the sun!" 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. I usually agree with you here Dr 1, but in this case your misinformed. The flange on the eyelet faces the wood servo rail. This is so the eyelet doesn't sink into the wood over compressing the grommet. The screw won't crush the eyelet if it isn't screwed in there by King Kong. Sorry but I feel yer wrong on this. >>To add a bit, the brass eyelet should be installed with the flanged end >>down. [quoted text clipped - 12 lines] >"There's a Hun in the sun!" > SignatureMike Gordon AMA 320990 Remember RC Pylon Racing, the ultimate thrill, when Sex and Drugs just ain't enough. Sorry Dr1-man, but you got it bass-ackwards. Flange on the brass bushing goes DOWN against the SOFT wood servo rail. I think you're out voted on this one. > >To add a bit, the brass eyelet should be installed with the flanged end > >down. [quoted text clipped - 10 lines] > Dr.1 Driver > "There's a Hun in the sun!" >I think you're out voted on this one No voting required. I do it my way, you do it yours. The newbiew will do it his way. He may decide one way of another is best for him. Dr.1 Driver "There's a Hun in the sun!" > >I think you're out voted on this one > > No voting required. I do it my way, you do it yours. The newbiew will do it > his way. He may decide one way of another is best for him. Sideways? 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. > 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. Those 'crappy servo mounts' haven't disappeared; they're still being packed with radio systems. It's just that many of us have moved on to better ways of doing things because of the more complicated models we build. Cheers, Fred McClellan The House Of Balsa Dust home.mindspring.com/~the-plumber AMA L180201 IMAA LM 090 NASA 6512 LHA 2 WB 233 "Fred McClellan" <notthe-plumber@mindsprang.com> wrote in message : > Those 'crappy servo mounts' haven't disappeared; they're still being > packed with radio systems. > > It's just that many of us have moved on to better ways of doing things > because of the more complicated models we build. I'm just courious, why are the servo mounts 'crapy'? I've used them since I got my first Proline radio in ''72 and one was in the package. Where they fit the physical size and layout of the radio compartment/control system how can there be better ways? Currently, four of my models, a modified trainer type, a bype,and 2 '70's pattern planes have the servo mounts (2X1) in them and they have work perfectly for the 2-4 years these particular models have been flown on a regular basis. No, they are not useable for pull/pull systems or for a/c which need different spacing or location of the servos, but 'crapy', I think not. Paul > Sorry Dr1-man, but you got it bass-ackwards. Flange on the brass > bushing goes DOWN against the SOFT wood servo rail. [quoted text clipped - 15 lines] > > Dr.1 Driver > > "There's a Hun in the sun!" Dr.1 Driver gets my vote.....flange up is correct.....its just common sense. >>To add a bit, the brass eyelet should be installed with the flanged end >>down. > >Since the grommet bears directly on the wooden servo rail, the flange is not >needed on the bottom. Install the brass eyelet with the flange up, to provide >a hard bearing surface for the servo screw. <SNIP> Not. The flange is there to prevent the eyelet digging into the servo mount (usually wood), effectively shortening the eyelet and allowing the screw to over-compress the grommet. Since manufacturer-supplied servo mount screws have a wide head (integral 'washer', as it were), that is sufficient for the straight (upper end) of the eyelet to seat against, the screw cannot shove the flanged end of the eyelet into the wood and it cannot over-compress the grommet. The screws should be run in until the screw head bottoms out on the un-flanged end of the eyelet - the length of the eyelet sets the amount of compression for the grommet. Cheers, Fred McClellan The House Of Balsa Dust home.mindspring.com/~the-plumber AMA L180201 IMAA LM 090 NASA 6512 LHA 2 WB 233 On 4/24/2004 2:10 AM Ted shuffled out of his cave and grunted these great (and sometimes not so great) words of knowledge: As you have seen, you will receive a lot of very good information here. You will also see SOME conflicts and differences of opinion. For the most part, I would say that 95%++ of the information is good. After awhile you will also be able to figure out who is providing the best knowledge/expertise and in which area or areas. Welcome to the hobby. Take offs are optional. Landings are mandatory. > The instructions for my Great Planes PT-40 are telling me to remove the > servo arms and wheels from my servos and install the rubber grommets [quoted text clipped - 3 lines] > > Thanks guys, I'm really new to all this... > The instructions for my Great Planes PT-40 are telling me to remove the > servo arms and wheels from my servos and install the rubber grommets [quoted text clipped - 3 lines] > > Thanks guys, I'm really new to all this... Each S3004 servo should have two holes in each mounting tab, four in all. The grommets (little black rubber donut shaped things) go in there to absorb vibration. The brass eyelet goes in the grommet flange down to keep the screw from squishing the grommet too much. Welcome to the hobby, and remember, when in doubt, ask! Morris >The brass eyelet goes in the grommet flange down to keep the >screw from squishing the grommet too much. Think about it, Morris. The grommet bears its full surface area against the wooden servo rail. It won't squish too much on that side. The screw, however, is only a small circle of steel against the much larger rectangular grommet. With the eyelet in flange-up, there is a larger bearing area for the screw to seat against, and less squishing will occur. I've tried it both ways, and will always install my eyelets in flange up. Dr.1 Driver "There's a Hun in the sun!" Well....if you read the instructions with the radio it will tell you flange down!! Look at the pic for crying out loud. I vote with the majority on this one. I always put mine in flange down. That way I can tighten the screw until it gets snug without pinching the grommet to much. Hey I need all the help I can get. Eddie Fulmer On Sat, 24 Apr 2004, Dr1Driver <dr1driver@aol.com> wrote >>The brass eyelet goes in the grommet flange down to keep the >>screw from squishing the grommet too much. [quoted text clipped - 7 lines] >Dr.1 Driver >"There's a Hun in the sun!" I think you are wrong DR1 but respect your view to do it your way. The intention is that the bush fits from the bottom so that when you tighten the screw until the screw flange meets the unflanged end of the bush, the correct compression is applied to the grommet to give the dampening that the manufacturer has determined is appropriate. With the bush flange against the bearer it is not practical to over tighten. If fitting the bush from the top, over tightening of the screw will push the plain end of the bush into the bearer and over compress the grommet. SignatureRichard > On Sat, 24 Apr 2004, Dr1Driver <dr1driver@aol.com> wrote > >>The brass eyelet goes in the grommet flange down to keep the [quoted text clipped - 16 lines] > fitting the bush from the top, over tightening of the screw will push > the plain end of the bush into the bearer and over compress the grommet. 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. Mike, > Flange up, no distortion......dont over tighten the > screws. Very simple. Exactly! -- Jim L. https://sourceforge.net/projects/virtual-access/ Using - Virtual Access(OLR), ZAP 4.5, & WinXP Pro w/SP1 >>The brass eyelet goes in the grommet flange down to keep the >>screw from squishing the grommet too much. [quoted text clipped - 5 lines] >seat against, and less squishing will occur. I've tried it both ways, and will >always install my eyelets in flange up. When you have nothing else to do, you might try installing an eyelet your way, without the servo or grommet. See what happens to the eyelet. If you're drilling the pilot holes with the correct bit (# 56 for standard #2 servo mount screws) I think you'll find that you can run the screw in to your heart's content, merrily shoving the sharp end of the eyelet into the wood. Try it the right way 'round and you will most likely strip the screw head slots. Only one of the two orientations can be correct, and the guys who make servos say your way is wrong. It doesn't really matter if you've had no failures, but it's the same thing as installing flat washers wrong way down. You might also consider the servo mounting screws from Micro Fasteners. Hex drive, not Phillips. http://www.microfasteners.com/catalog/products/TWSSHWHMS.cfm _much_ better than the Phillips head stuff. Cheers, Fred McClellan The House Of Balsa Dust home.mindspring.com/~the-plumber AMA L180201 IMAA LM 090 NASA 6512 LHA 2 WB 233 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 > >>The brass eyelet goes in the grommet flange down to keep the > >>screw from squishing the grommet too much. [quoted text clipped - 37 lines] > LHA 2 > WB 233 >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. 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 http://www.mindspring.com/~torkit/ and notice the values associated with the sizes of fasteners we most commonly use, i.e. 2-56, 4-40, 6- and 8-32 . For 4-40, optimal torque for a socket head machine screw going into aluminum is 12 - 14 in-lb. If two or three inch-pounds were used just to flatten the washers' rough side, the fastener is below optimum tension. 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 > >Wait a minute Fred!!! > >I agree, servo eyelets should be flange down and the Micro Fasteners washer [quoted text clipped - 73 lines] > LHA 2 > WB 233 Thanks for the explanation. Now maybe I can tell up from down! That was THE best info to come out of this thread. Thanks Fred mk > >Wait a minute Fred!!! > >I agree, servo eyelets should be flange down and the Micro Fasteners washer [quoted text clipped - 73 lines] > LHA 2 > WB 233 > >The brass eyelet goes in the grommet flange down to keep the > >screw from squishing the grommet too much. [quoted text clipped - 7 lines] > Dr.1 Driver > "There's a Hun in the sun!" 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 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. > > >The brass eyelet goes in the grommet flange down to keep the > > >screw from squishing the grommet too much. [quoted text clipped - 19 lines] > > Morris 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. SignatureThe Raven http://www.80scartoons.co.uk/batfinkquote.mp3 ** President of the ozemail.* and uunet.* NG's ** since August 15th 2000. > If the screws are tightened correctly it really won't >make a difference which way the brass insert is (he says with limited >experience). 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!" > > If the screws are tightened correctly it really won't > >make a difference which way the brass insert is (he says with limited > >experience). > > Maybe limited experience, but a lot of common sense, Raven. Call me a newbie, just built my first a/c yet to fly it. However, I've flown others....... > 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. 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. > 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. Agreed, secure it and nothing more. > 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. 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. > 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!" Regards SignatureThe Raven http://www.80scartoons.co.uk/batfinkquote.mp3 ** President of the ozemail.* and uunet.* NG's ** since August 15th 2000. Raven, > just built my first a/c yet to fly it. A/C ehh?<gd&r> -- Jim L. https://sourceforge.net/projects/virtual-access/ Using - Virtual Access(OLR), ZAP 4.5, & WinXP Pro w/SP1 > Raven, > > > just built my first a/c yet to fly it. > > > A/C ehh?<gd&r> A common abbreviation outside of the US for aircraft. SignatureThe Raven http://www.80scartoons.co.uk/batfinkquote.mp3 ** President of the ozemail.* and uunet.* NG's ** since August 15th 2000. The, > A common abbreviation outside of the US for aircraft. Shoot, I was expecting to see photo's of your A/C (air conditioner) flying! -- Jim L. https://sourceforge.net/projects/virtual-access/ Using - Virtual Access(OLR), ZAP 4.5, & WinXP Pro w/SP1 > The, > > > A common abbreviation outside of the US for aircraft. > > > Shoot, I was expecting to see photo's of your A/C (air conditioner) > flying! Is this where I remember a free plan for a flying airconditioner in a RC magazine? Hmmm........ :-) SignatureThe Raven http://www.80scartoons.co.uk/batfinkquote.mp3 ** President of the ozemail.* and uunet.* NG's ** since August 15th 2000. On Sun, 25 Apr 2004, The Raven <swilson150@yahoo.com.au> wrote >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. ... and that is how I mount all of my wing servo's these days in moulded soarers and electrics. Nothing simpler ....... SignatureRichard >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 [quoted text clipped - 8 lines] >way you use the inserts, you shouldn't need them so tight as to introduce >negative effects. 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<. Installed wrong, you can indeed over-tighten the screw and render the grommet ineffective because you're guessing at how much to compress the grommet. Why let yourself in for a guessing game when you can follow the manufacturer's instructions, put the flange down, tighten the screw until it contacts the eyelet, and get the grommet compression right automajikly ? You do what you want. I follow the instruction of the guys who made the servos. Cheers, Fred McClellan The House Of Balsa Dust home.mindspring.com/~the-plumber AMA L180201 IMAA LM 090 NASA 6512 LHA 2 WB 233 > >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 [quoted text clipped - 11 lines] > Installing the eyelet flange down means you _cannot over-tighten the > screw_. I see your point but if you go that far you;ll be tearing out the timber with the screw threads while distorting the grommet significantly. > No guess-work, idiot-proof concept - run the screw down until > it contacts the non-flanged end of the eyelet and you're done. Yep, that will work. > The grommet is _supposed_ to be compressed, but it's supposed to be > compressed >correctly<. And if done correctly it really doesn't matter which way the brass insert is because you won't have it tight enough to do any damage with the inserts.. > Installed wrong, you can indeed over-tighten the screw and render the > grommet ineffective because you're guessing at how much to compress [quoted text clipped - 4 lines] > until it contacts the eyelet, and get the grommet compression right > automajikly ? Looking at my servo box and instructions now. No mention on how to fit the insert. The vague sketch on the box might suggest the insert goes at the top but it's far from conclusive. Suffice to say, I've followed observed practice from the local club and no-ones plane has fallen apart due to unsecured servos. > You do what you want. Which I will, but I'm open to thoughts on the subject. > I follow the instruction of the guys who made the servos. Which would seal it for me, if the bothered to mention it in the instructions... so I rely on basic logic. Put the inserts under the grommet and the screw bears down on raw grommet, brass inset bears down on timber for no particular reason (the grommet is just as effective at spreading load). Put the inserts at the top of the gromment and screw bears down on a load spreader without damaging the grommet, the base of the grommet then spreads it's load over the timber. The base of insert will never contact the timber (at least with my servos) unless you're already tearing it up with the threads. Of course, overtighten either method and you open yourself up to problems. Not saying either method isn't going to work but both will suffer from heavy handedness. SignatureThe Raven http://www.80scartoons.co.uk/batfinkquote.mp3 ** President of the ozemail.* and uunet.* NG's ** since August 15th 2000. >> Installing the eyelet flange down means you _cannot over-tighten the >> screw_. > >I see your point but if you go that far you;ll be tearing out the timber >with the screw threads while distorting the grommet significantly. Not if you've used the correct drill for the pilot holes. Futaba supplies #2 wood screws, which means a # 56 drill for the pilot hole, here in the States. With proper pilot holes, attempting to "rip out wood" usually results in stripping the screw driver slots in the screw. Irritating, but you don't normally pull the threads out of the wood unless you got the pilot hole size wrong. >Which would seal it for me, if the bothered to mention it in the >instructions... so I rely on basic logic. > >Put the inserts under the grommet and the screw bears down on raw grommet, >brass inset bears down on timber for no particular reason (the grommet is >just as effective at spreading load). No. The grommet is not there to spread load, it's there to provide vibration isolation. As such, it should have the correct amount of pre-load (compression), and the correct pre-load is established by the thickness of the grommet and the length of the eyelet. As the screw is run in the head bears down on the eyelet, not the grommet. The eyelet is sized to provide for the correct compression (pre-load) of the grommet. The only way you can get the grommet over-compressed is to install the eyelet flange side up, in which case the self-limiting nature of the eyelet is defeated and you have no way of knowing when you've got the grommet correctly pre-loaded. I've recycled lots of servos over the years, and have never seen a grommet damaged by the screw head or the eyelet. I've even recycled screws, eyelets, and grommets from models which completed a Figure 9 maneuver, where the servo case didn't survive, but the fastening hardware was none the worse for wear. Futaba web site describes the proper way to install a servo at http://www.futabarc.com/faq/product-faq.html#q479 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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