360 servo mod

Before getting started on the turret mechanism, I dusted off the modified servo and gave it a test-run. Uh-oh! it was broken! One of the solder points inside broke loose, so I had to go back in and fix it. Perfect time to show how to modify a servo to move 360 degrees, eh?

OK, so a little walkthrough: The potentiometer (black circle far right) is getting disconnected, but first I made note of where the wires went. In this pot, the yellow wire was the 'center', or 'neutral' wire, and was the common point between the resistances both clockwise (red) and counterclockwise (green).. Representing 'Zero'. Servoes match the radio transmitters' thumstick by trying to constantly 'zero out' with the pot reading from that transmitter channel.

This little explanation is important for really only one reason: you need to know which solder point on the circuit board is the 'common'. In this particular servo: the common (yellow) wire went to the point of the <

Heres a better view of the circuit board, and how the resistors were situated. This was a particularly roomy servo, yet was small- making it perfect for this sort of modification. There was room to cram the pots wires back in the cavity, and STILL have room for the resistors. Side note: I cant remove the pot from the servo, since its shaft, which is geared into the control arm gear, also holds another gear in place on its shaft, so it needed to stay.

The resistors are obviously the same rating, as the stripes match, but the important stripe for this application is the far right one: its gold (cant really tell in this pic, but it is). This is the Tolerance stripe, meaning that this resistor is within 5% of its designated rating. This is better than normal, which is 10%. All resistors have this 'slop', and I went through several with an ohmmeter to find two that were as close as possible. (because this balanced Resistor-bridge is what represents 'zero', the same as the pot in center position, and it aint zero if they are lopsided!) But thats all thats needed to modify a servo to spin coninuously one way or the other on command.

I guess I should explain WHY it works, since I went though the trouble of showing HOW:

The pot in the servo is linked to the poition of the servo control arm. as the Arm swings around it turns the pot. The servo is set up to stop when the pot reads 'Zero'. If the pot finds itself lessthan [<] 'Zero', its setup to drin one direction intil the pot reaches 'Zero'. same way the other direction.

Now, 'Zero' is in quotes, because its actually not Zero Zero, but what the radio transmitter channel is commanding, and its command varies depending on how far you move the thumbstick on your transmitter one way or the other. In this way, the servo matches the thumbsticks position pretty much instantaneously, checking probably thousands of times a second.

Thats all well and good on how the servo channel works, but how does adding the resistors make it work? Well, by cutting out that feedback number from the pot, and replacing it with a matched set of resistance, we are 'faking' that its always at 'Zero'. You would think that it would make the servo never move again, but thats not quite the case: The "am I [<] than Zero??" part of the microchip is still working, and listening to the radio channel. So when you move the thumbstick left, the microchip goes "OH! Im [<] from where I need to be! that means drive left.. not there yet? then keep going... keep going" and will continue spinning left until it believes it has finaly reaches Zero - which is actually when you released the thumstick to center. At that point the servo stops and stays there where it wound up.

Presto! a 360 Modified Servo! Hope I explained it clearly enough.

Back to the turret mechanism, now that I had a functional Servo again, I mounted it to the turret piece to give it a little test, and also to eyeball if I got he center hole right (looking for a wobble), and shot another little movie:

Looks good! Hehe Side note, hear the stereo in the background that suddenly goes quiet when the turret starts moving? Thats because my Futaba transmitter flooded out all other radio signals in the immediate area. And the stereo was receiving only "LEFT ON CHANNEL 4! LEFT DAMMIT!!!" to its antenna, and was unable to pick up any other signals... hehe thats what old CB-ers call a STOMMMMP! Even though my transmitter was on 72 mhz (khz?), it still flooded all weaker signals out of existance.

hmm maybe I should'nt hold it so close to my lap when filming...

Servoed Hammerhead: Windshield and Lighting

Next, I dug out the windshield as a side little project, since I was going to light it as well.

Its going to have an amber backlight, but needs a window that will let a glow out, yet not let anyone see the servo thats directly behind it.










Someone reccommeded the perfect sort of translucent material to use as a windshield: milk bottle plastic. Thats ust perfect, aint it?








So, with the batterypack made, I wired up the LEDs, and made a little terminal block (the white thing), to make its a clean and as organized as possible.




Next came the difficult problem of mounting the lights, and making a light trap to keep the light from bleeding out through all the panel gaps, and even through the plastic at the top of the wing. The solution I finally came up with was this Ballast putty I had. Its kindof like playdough, but is the consistency of warm cheesecake, never dries, and comes off clean. Its not very sticky, but makes for a good gap filler, and will be the perfect solution to themany problems I would normaly have placing, mounting, and aiming the leds just right.







The ballast putty is the whie stuff, and I plced two globs of it in the area where the headlights would be.

Then I just squished the belly plate into place, and let the putty shift and ooze.. wherever. The great thing about this stuff is:





The belly plate pulled away clean, leaving me two perfect molds that filled all the areas where the light may peek out. The bumps visible match the pits on the bellyplate, showimg me where the light channel actually ends (it was very difficult to position/line up everything before: as the placement was completely out of sight as the pieces were put in place. The putty mold made it eas for the next part



I had to aim and place the bulbs of the LEDs just right. Not only did they have to point directly out the slits (focused directional beam), but also needed to be tilted slightly 'ground-ward' to make the light beams of the headlights perfect. The putty made it relatively simple. I just smashed them in place, letting the putty shift away... then I squished it back into the area, so that when I pressed the bellyplate in place one more, everything was filled in and final.



Then I dug out all the putty that was in the way of the beams of light. Presto! Now the bulbs are in precisely the perfect position and angle... something that would have been very very difficult to arrange any other way. The putty that was removed was combined and placed centerline, to solve another difficult problem: the cockpit light, for the windshield



The trick of the windshield light is that the bulb has to be indirectly lighting the area, and out of line of sight of the window. This simulates backighting from an illuminated cockpit control panel.. or something like that. Dim, yet definately lit is the objective. The putty made it simple to place where you see it, where otherwise it would have been tricky, with all the curved angles and such.

Next came routing the wires, and preparing the terminal block for connection. I used the channel trips of styrene to make a couple of wire trays to pin the wires in place, out of the way. Looks nice, huh? Can you tell that I'm an electrician by trade by looking at that?

Here the wiring is made permanent by soldering, and the servo system is put back in place. You may notice that the wires for the amber LED was not permanently connected. This was because the amber LED seems to be a lower resistance than the blue/whites, so that when they are all wired up in parallel, the power took the path of least resistance, leaving the white LEDs dead. Good thing I tested everything before making it permanent.

Isnt it neat how all those little gizmos are crammed into the nose area? I plan on leaving everything in the top half of the tank, so I can pop the bellyplate off to show off all the goodies inside.

Heres a reality check, on just how tiny all this stuff is, so: a Quarter. No thats not a gimmick giant sized quarter. Isnt that shocking?

Now that its all complete (except for the windshield itself) in this front section, its time for another movie, dontcha think?

And there, Whew! All caught up! From now on further updates will be about current events.

Servoed Hammerhead: Batterypack

Next was the headlights. Ive had some very decent 3.6v blue/white leds for a while now. Theyre perfect for this job. 3v leds are pretty much flashlight powered leds...













As you can see. In the top pic you can see thats its being powered by two hearing aid-style batteries, 2 stacked together. This was plenty power to do the job, but first I needed to come up with a way to switch it on/off with a bit more style than my first lighted Hammerhead (as I was still embarrassed by how sloppy and ugly it looked).



















So I got a micro slider switch, some styrene rods, and puzzled out how to put them all together into a tiny package.

















And here it is! Aint it CUTE!?! I found the channeled strips fit the batteries perfect, but the lips in the middle kept the batteries separated, so they had to get filed down. The switch was handilly the same width as the 2 batteries, so there we have the little box for it all! The wiretaps were twisted and plugged into holes in the side to make it a tight fit, for a good contact.









Heres another angle, showing how its all supported and self contained. Again, aint it cute?









And the switch contacts. I used the unused switch tap for the - part of the circuit, just to have both sides of the circuit anchored all in one place.









And finally, to prove that it all works!









Unfortunately, even as small as it was, it wasnt small enough to put it in the first place I was thinking: to the inside of the side hatch. It would have been nice to just flip the door open and have the gizmo flip out with it, but oh well.

















I have 2 plans for it now, instead:







Plan A is to just have it lay inside the door like this, to I could pull it out to get to the switch and batteries.

Plan B is to permanently mount it like this, to its more 'designed' and less 'thrown together'.




Either way is still up in the air, as I will wait until the rest of the rear cabin is filled with the other gizmos before commiting either way.

But now that the stuff is almost ready, I just had to temp wire up the leds and get a look at how it will look.


The lights are just lying in the spots, and things are looking good! There is light bleeding out of all the gaps though, so thats part of my next project.

Heres a view of the splayed out headlights on the ground, but eh left wings light is being blocked by the burst cannon. Still you can see the point of it all.

Servoed Hammerhead: Servo and testout

Next, I mounted the servo. I routered away all of the front landing gear box, but after doing so, found out that the servo box was still too tall: the linkage rods would be flexed too far to get to the control +, and that was a problem. Luckilly, mounting the servo on the roof of the model would fit perfectly! The problem was how to mount it up there, it was all curves and wide open.. how to mount the servo in a way that it could still be twisted/removed? Greenstuff. Epoxy putty. I had a bunch, so started making a big block on each side of the servo, pinning it between the two in the floating open space where it needed to be. Before the epoxy completely set, I removed the servo, and let the stuff cure. Then, I cut away the excess, leaving just what was needed


Heres a good closeup of it all: the phillips screw visible on the control + is a handy little attachment I was happy to see I had space to mount: its a sliding set-screw sorta thing, allowing me to slide the rods and adjust on the fly, to make lining them up easier. LEDs were test-fitted, to make sure that there was room for everything planned. The linkage for the chin turret is seen , angled crossways, so the three things will spin the same direction.



Finally, I tried it out. Because I still wasnt absolutely sure the drones would actually spin when the rod went in or out... or just pop straight out. So I wasnt going to stop working on it until I could actually slap all the electronics together and give it a shot. I put burst cannons on all three turrets, to get a better feel for if theyre lined up or not.

Whew!! so it does spin! And looks awesome to boot!!

Servoed Hammerhead: Drone linkage

[grr I cant just cut/paste this whole project... this site doenst allow links to be pasted, or something, so I'm going to have to redo it all.]

I plan on using the curved cradle mount in the wing to hold the drone disk in place, since it covers approx 70% of the drones' circle. So, running on that assumption, I got right to work modifying the drones to accept the pushrods and also to have room for the pushrods motion.

I wanted to keep the mechanism that moves the drones invisible, so, notched out the side of the disks in the area where the rods will be. This was also a good place to have the rods go from the wings' point of view: this slot is right where the meat of the wing is.

Heres a sample layout of the rod, showing how it enters the circles area, and the vertical part (hard to see, sorry) is the hook, that will attach to the drone. At the moment its empty space, but the other piece of the drone will be where the hole actually goes. The hole will be directly to the read in the arc of the circle, and that will be the neutral position, to give the largest arc of movement in each direction.

Here the drone is assembled, and the hole is seen, with the rod sticking out. Some fine shaving and tuning was required to keep the rod pivoting in its hole smoothly, and to sweep through the midst of the drone and slot going smoothly as well. All of this was important; I wanted to avoid any binding of any sort.

This view shows the hole in the wing, and in general shows how everything is set up.

Here the rod is inside the hull, and the position of the holes, and the straight rods, is just about where I wanted it, to give the most room for the servo and its control +.

Servoed Hammerhead: intro/planning

Now, I am finally caught up to my current project, and I'm going to copy/paste dump all the updates so far up to my curent update, and from here on everything will be 'as it happens'.

Well, I feel that feeling coming up again, and AM now going to take the servo-ing several steps further. Here is my initial (often overly optimistic) Mission Statement:

I will build a hammerhead, with a spinning turret remotely controlled. In addition, The chin turret will move left and right (90-120 degree travel), and the GUN DRONE CRADLES will track along with it! Lastly, the third radio channel will act as a 'throttle', and pivot the engine pods up and down. Lighting-wise: the foreward slits in the wings will be lit (white led/incandescent headlights), the cockpit window will be translucent and faintly backlit, the engine pods will have a red glow from the exhausts, and, if possible, the railgun will have blue light strips down the barell length on both sides, illuminating the middle open channel.

WOW. Im not too sure about all that, but anyways, thats the obsession that simply MUST BE MADE MANIFEST.

And heres what ive got so far:

This is the electronics package from the old Razorback. The blue thing is the servo, modified to spin continuously left or right on command (to those familiar with RC servoes, youll know this isnt normal. I had to modify it internally), the white-ish thing is the radio reciever, and the big yellow thing is the battery pack. All in all you can see its pretty small package, easily able to fit fully inside the vehicles, as wires running out of it kind of takes away the suprise/kewlness factor of it all.

This is a rough test fit, showing the arrangement of the equipment in such a way to directly drive the turret- the same way it was used in the Razorback. I can see that there is plenty of room, so this stuff will remain pretty much unchanged (sorry razorback... you can keep the lighting/radar spinner though). That blue servo is pretty small, and I though it was as small as they get...

until I found this:Note the not so subtle pricetag in the background... yeah.. once you get the radio, the rest of the stuff has gotten super cheap over the years.

Here is a size comparison shot, to give you an idea just how tiny it is, and how suitable it will be for this vehicle design.

And now, for the mechanics of how its all supposedly going to work:

I plan on removing the nosegear box, and sinking the box of the servo into the hole, with the cut off landing pad covering the bottom, and hiding it all. The servo will have it arms, and the linkage wires (an example of one top right) will go from that spinning drive arm to the nose (on the left/right side arms), while the drone cradles will attempt to be driven left and right by a pushrod going from the foreward facing drive arm out through each wing, hooked onto the drone disks... somehow (still an initial plan)After some carefull looking and positioning, it looks as though I could drill a tube within the wings, at the rear of the wing, to make the wire reach the drone disks... the problem is the pivoting connection of that rod so that, if it is pushed in and out, the disk will pan left and right. I dunno at the moment: but possibly I could notch the edge of the disk, where it butts against the cradle, allowing the wire to get to the inside of the disk, to attach to the drone. Its complicated, as you can imagine, the angles of all this stuff will change as it moves. And I have to ensure it doesnt just push the drones off of the wing. Plus, I want it to be all unseen.

Well, these are the challenges. There is room. I have the parts. Its just the details of the mechanics of it all... Any suggestions are definitely welcome!!