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Balsa or Bass servo mounting blocks

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Old 06-09-2018, 12:33 PM
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the Wasp
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Default Balsa or Bass servo mounting blocks

so guys, my plane came with Balsa servo mounting blocks, they are only 8mm wide, is Balsa strong enough or should I make new ones out of Bass ?? the Bass blocks are 9.80mm wide

the Servos are 90oz in torque

thanks guys !!

Jim
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Old 06-09-2018, 02:26 PM
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Prsonally, I always use some aircraft ply for the servo screw mounting area. I pick up all the good scraps that can be cut down ..just for that purpose. Personally I use 1/8th glued on top of either balsa or lite ply.. It sort of depends on the kit or situation of where I am mounting the servos.

There is nothing wrong with bass though..
I typically drill the hole, turn in the screw, remove it, drip thin ca in the wood to harden the threaded hole area.. then once dry, mount the servos..
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Old 06-09-2018, 05:48 PM
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I pretty much do as foodstick suggests making servo mounts from spruce, bass, ply or a combination of those materials. I always harden the threads with thin CA as foodstick suggests. If the threads get loose from repeated removal ./ install cycles, I just add a bit more CA to re-tighten the hole. I can't say I'd like balsa mounts unless they were capped with a harder wood.
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Old 06-09-2018, 05:57 PM
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I'm in agreement with Foodstick. If it takes a screw I use ply, bass or hardwood.
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Old 06-10-2018, 07:35 AM
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Yup, what all of them said. Plywood or hardwood, CA to harden the threads. Sometimes I will mount a micro throttle or retract valve servo on a piece of lite plywood, but that is as light as I will go.

Scott
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Old 06-11-2018, 10:04 AM
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thanks guys !, I have made up new blocks from quality Bass

Jim
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Old 06-15-2018, 06:41 PM
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I like quarter square Hardwood such as spruce to mount my servos on in airplane and also use 1/4 square hardwood for pushrods for the elevator and rudder in my airplanes. I would never use balsa wood as it might snap and guess you have a nice wreck to throw away!
Michael
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Old 06-22-2018, 01:14 PM
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Depends too on the plane. Some little park flyer could probably get away with balsa mounts. But since you mentioned 90 oz of torque, I suspect you plane is a bit bigger. I always prefer to go with either ply, spruce or even maple. It all depends on the application.
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Old 07-01-2018, 09:22 AM
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just about anything other than balsa wood. although I have used that too,...with no problems at all as long as it's not the very softest, lightest grade. there really isn't that much stress involved in running control surfaces, the main consideration is that the throws are properly adjusted so that the extent of control surface travel is not what is stopping the servo arm's travel. even the most dense hardwood is not too heavy considering the sizes of the pieces needed for mounting a servo.
I think there is an awful amount of overkill and "much to do about nothing" when it comes to the torque of control surface servos. it is only since the hobby got infiltrated with young "techy types" with their scientific calculators and the internet, needing something to post about, that servo torque became such trendy concern. in all my 40 plus years of being around rc, there was never any concern beyond "having a decent servo", until recent years. 90 oz. is aprox. 7-1/2 lbs of force . no model control surface of any plan is anywhere near big enough to require that much force to move in the air stream. the association between plane weight and servo torque is a false equation, made up simply to have something to compare numbers ....a 7-1/2 lb. plane doesnot need servos with 7-1/2 lbs. of torque to move a control surface.

Last edited by r ward; 07-01-2018 at 09:41 AM.
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Old 09-06-2018, 09:36 AM
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I personally want my servos solid as a rock
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Old 09-07-2018, 02:26 PM
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Originally Posted by r ward View Post
just about anything other than balsa wood. although I have used that too,...with no problems at all as long as it's not the very softest, lightest grade. there really isn't that much stress involved in running control surfaces, the main consideration is that the throws are properly adjusted so that the extent of control surface travel is not what is stopping the servo arm's travel. even the most dense hardwood is not too heavy considering the sizes of the pieces needed for mounting a servo.
I think there is an awful amount of overkill and "much to do about nothing" when it comes to the torque of control surface servos. it is only since the hobby got infiltrated with young "techy types" with their scientific calculators and the internet, needing something to post about, that servo torque became such trendy concern. in all my 40 plus years of being around rc, there was never any concern beyond "having a decent servo", until recent years. 90 oz. is aprox. 7-1/2 lbs of force . no model control surface of any plan is anywhere near big enough to require that much force to move in the air stream. the association between plane weight and servo torque is a false equation, made up simply to have something to compare numbers ....a 7-1/2 lb. plane doesnot need servos with 7-1/2 lbs. of torque to move a control surface.
1) I agree that a 7-1/2 pound Cub does not need a 90oz rated servo, but, there is 16 OZ in 1 pound, 90 divided by 16 is 5.625 (pounds) (not 7.5 pounds), that's just about 2 pounds difference in your counting,,
2) no one here is talking about 7-1/2 pound plane, my plane I am talking about should weigh in at 9.5 pounds and should fly around 70 MPH,

now to get a reference of wind power take the wing for your 70 inch span, 7&1/2 pound Cub and walk out in a strong wind of say 30, 35 MPH, hold the wing vertically at it's center, or root rib,, how much weight can you hold, surly it's more that 15 or 20 pounds, now tell me if you can hold that wing steady in that 30 MPH wind while holding the wing at it's root rib, I'm betting you can not hold it steady. to add the faster your plane flies the more drag (or weight) it puts on ALL services, this is why all wings are designed and built to hold more weight than what the plane weighs, don't forget the G factor that loads the air frame and control suffices 2, 3, 4 times the flying weight,, now I don't know much about wind forces on an aileron or rudder, but I do know that there is more than twice the amount of force on an aileron or rudder at 40 MPH than there is at 20 MPH>>> now what about 70 MPH
now, also consider these facts about your 90oz (5.625 pound) servo that you have connected to your aileron, rudder or elevator, A) there is about a 110% chance that that servo does not produce it's rated torque spec,, B) servos are tested with the hole on the arm closest to the servo's output post, and the farther out you mount your linkage on the arm the lower the torque out put is, now your 90oz rated servo is down to about 70oz = 4.375 pounds, yet you would like to be safe and have a servo that produces more torque than your plane actually needs,,

my other plane, a Wold Models 46 size P-40, it's suggested flying weight is 6.3 pounds, this plane has been reported to fly at 70MPH with an OS AX46 (that sounds kind of fast to me), I am putting an OS Hyper 50 in mine with an over size muffler to help it breather batter, I would feel safer with a 90oz rated servo in it than a 50oz rated Cub servo..

don't forget the G factor !

Jim

Last edited by the Wasp; 09-07-2018 at 02:28 PM.
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Old 09-09-2018, 03:04 PM
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If memory serves the old Kraft KPS-14 servos did around 24 ounces of torque. The KPS-15s did slightly more, maybe 28 ounces. And these are what we would put in our 60 sized patter planes and 10 pound scale warbirds.
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