Gremlin #2 servos in the tail!

[Motowncali]

Took a little while and actually by the time I figured out the linkages, the elevator servo is mounted just like in the first build, but the rudder servo is mounted under...
The rudder servo gets mounted first, arm up as you look into the service window. Then the elevator tray slides down in and mounts to the rudder servo beams.
1mm carbon pins to keep the plywood plate stacks aligned and held tight. Added a few lightening holes to keep the weight down and they look cool anyway...
Rudder arm linkage is in the third hole out from center, as long as I could make it, still needed to shave the rudder sniper to get a little more throw, could get even more if the wiper were removed...
I put the rudder servo in a bag, secured it to the rails, then screwed the elevator tray to the rails, then glued in with 15 minute epoxy and milled fiber. Once cured, removed tray, removed servo, cleaned a little of the excess epoxy that squished out with a Dremel and a 1/2 stone.

 

[Konrad]

Wow, that looks like a real neat and tidy installation!

 

[Konrad]

Love the attention to detail! Nice job undercutting the corners to stress relieve the opening.

I often wonder why Doc. didn’t move the opening aft. I’d have thought that this would allow for more support under the stabilizer (full depth walls on both sides). Also an aft opening would allow for easier mounting of the elevator servo without the need for your clever cantilevered servo mount.

I see that in the Gremlin manual there is mention of installing the elevator servo through the aft fin. This is possible with the rudder side hinge. As this allows the rudder to be moved out of the way.

With the advent of great 8mm servos I wonder how many Gremlins are built with the supplied elevator bell-crank. With my two Aeroic models (previous manufacture) I have concern that the teflon snakes are not etched. This is why I’m really liking the idea of mounting the servos in the tail (fly by wire).

 

[Johnnashville]

Vary nice work Mo

 

[Motowncali]

Not sure Konrad... I think it has to do with designing, building , feedback, modifications...
The Aresti 108 was too far back and the vertical fin post actually came through the access area. This one is too far forward, I think the Aresti 2M had it centered, but when I redid that plane, the bellcrank assembly was already installed.
You try to think of everything on paper and something always seams to slip through... I know he is working on a scale ship and Dr.J and I have exchanged a few messages and he has done drawings and it is being designed with a tray for the servos to go in the tail from the start.

 

[Konrad]

I have to admit that I do like your cantilevered trays. But in the back of my mind I keep hearing my mechanics professor telling me that cantilevered designs are a sin against the engineering gods, and should be avoided if possible. Of course she was talking about structural stress. There are plenty of good reasons to have cantilevered designs, like our monoplane wings.

 

[Doc J]

GOD LOVES THE CANTILEVER!

Doc.

 

[Konrad]

Not my gods!! I look for support at both ends, much more ridgid and stable! Then there is the redundancy aspects.

All the best,
Konrad

 

[Doc J]

I think you have a God-given cantilevered appendage, Konrad...Not too sure about the rigidity or stability, but I do advocate redundancy testing as often as possible...

 

[Doc J]

By the way I finally decided to make the Redshift Spada new fuselage as an inverted radio install - just to make you smile today!

Quite a few new things that but the good news is they are all interchangeable.

Cheers,

Doc.

 

[Doc J]

Love the attention to detail! Nice job undercutting the corners to stress relieve the opening.

I often wonder why Doc. didn’t move the opening aft. I’d have thought that this would allow for more support under the stabilizer (full depth walls on both sides). Also an aft opening would allow for easier mounting of the elevator servo without the need for your clever cantilevered servo mount.

I see that in the Gremlin manual there is mention of installing the elevator servo through the aft fin. This is possible with the rudder side hinge. As this allows the rudder to be moved out of the way.

With the advent of great 8mm servos I wonder how many Gremlins are built with the supplied elevator bell-crank. With my two Aeroic models (previous manufacture) I have concern that the teflon snakes are not etched. This is why I’m really liking the idea of mounting the servos in the tail (fly by wire).

View attachment 2787

"I often wonder why Doc. didn’t move the opening aft. I’d have thought that this would allow for more support under the stabilizer (full depth walls on both sides). Also an aft opening would allow for easier mounting of the elevator servo without the need for your clever cantilevered servo mount."

Mistake in the CAD Mo - pure and simple. Obvious I know, but it still happens from time to time.

It won't be there on the next one - which will have the double hatch opening and the double KST servo mounting tray.

Plus an "electricable" nose!

Cheers,

Doc

 

[Motowncali]

Konrad, keep in mind that even though the servo is cantilevered out, the force it rotational to the tray, that is why I use four screws to secure the tray. Also, the tray is 1/8 thick, more than adequate for the job. The first tray I made was a little smaller and only had room for three screws, I didn’t like it, so I scrapped it and made a new one 1/8 wider just to allow room for another screw.
No textbook engineering here... just tried and true school of hard knocks...

 

[Konrad]

Like I said I like your mount! I'm sure it is more than up to the task! I'm actually impress at how compact it is. I too am a graduate with honors from the school of hard knocks.