DAY 14 - More stuff and a complete tear down.

(for those who only want the bling - scroll down for a video without all the "blah, blah")

OK, so here is the reason for the complete tear down.... actually a couple of reasons.  First, I was not too pleased with the fit of the skins.  Although they looked OK in the photos, there was a gap on the lower portion of the back door that would not stay closed without a good amount of effort.  In order to get the skins off, pretty much everything else has to come off.  Surprisingly, the entire droid breaks down into Frame, Dome, Legs, Feet and Skins in about 15 minutes.

Now that I have the frame alone on a bench, I can work on getting the skins to fit better.  I looked for any obstructions on the inside that may be holding the skin away from the frame, but could not find any.  I (SHUDDER) think that a little grinding of the O.D. of the back of the frame will allow the skin to sit in the correct position.  Some builders have left a gap at the sides of their units, and others have filled the gap with a strip of aluminum or ABS.  I have gained enough confidence in this build that I will remove some of the material from the frame itself to achieve the correct fit.

If I make a major mistake, all I have to so is shim the skin.  I sound all confident now - the results will be coming in future posts.

Reason #2 for the complete tear down:  The center leg.  After getting a lot of really great constructive criticism from the Astromech boards, I found that my center leg was, indeed, short.  I was also reminded that I needed to add the skirt at the bottom of the center foot shell.  This was something I knew I had to do, as during initial assembly, I really struck out on this part of the build.  The skirt is on the foot, but it is simply too high.  I used CA glue to hold the foot shells together which pretty much equates to scratch building a new skirt.  No problems there.... here is a photo of what it should look like (courtesy of Thomas' R2D2 Build Blog).

The reveal under the vented panels along the bottom is where my problem lies... I have no reveal.

Reason 2(a) of the tear down: Center foot mobility.  I am under the impression that I can have a manual 2-3-2 droid.  Meaning, I can convert him from a 3 leg mode (used for driving around) to a two leg mode (for glamour shots with Alex in his 3P0).   He has such a distinct look in both positions, I want to be able to have the options of converting him.  This will not be an automated system.... yet - that may come in the future.

I toyed around with about 30 different ideas on how to make the center leg mobile.  The ideas ranged from drawer slide (not beefy enough) to nested square aluminum tubing (not enough height inside the frame to accomplish the move).  While researching linear actuators,  I came across linear slides.  These linear slides are used in router tables and CNC machines.

Below is what I received last week.  15" long x 3/4" diameter linear slide with 4 pillow block bearings.
Mmmmmmm.... Pillow blocks.  Each of the bearings is rated at 600 lbs, so I think that they will do the trick.  The idea is to mount these linear slides on either the sides, or the front and back of the leg within the frame.  The leg then rides up into the body on the rails below.  The problem is all of the additional hardware that I need to mount these inside the frame and the flange that will mount to the foot.  All of those goodies are on their way this week.

I can't wait to get this together and functioning.  It works like a charm in my little brain - now all I have to do is get it all together in the real world.  I am excited as this will be my first scratch built assembly, and it will test my mettle as a builder.  I plan on documenting this well, so stay tuned for the results.

Now to the really scary part of the build.  Something I have less than zero experience with, the electronics.  Watts, Volts, Amps, Receivers, Transmitters, Motor Controllers, Dip switches, mixed modes, binding, wire gauges .... and so much more are items that are not part of my collection of useless knowledge that I have accrued over the years.

I did a BUNCH of research on the Astromech boards, YouTube and various RC boards.  As with anything on the inter web, you have to take the results with a grain of salt, because rarely do you get the EXACT answer for your application.  Without boring you with the details of how many setting I went through and how many dip switches I threw.... here are the results.

I will document the setting here for (mostly) my reference and to assist any other user who may need the help of someone who (almost) thinks he knows what he is doing.

Here is my little bench test setup.  I wanted to get the receiver talking to the motors outside of the droid.  These motors are much smaller than the ones used to drive R2, but are used for testing purposes.  The theory is that if the setup works on the bench - all you have to do is hook up the motors in the droid, and everything should work just like it did in these tests....  theories .... Hopefully next weekend, I will have a "proof of concept" moment, and we will see a little droid moving about the house.

For the uninitiated (like I was about 8 hours ago) here are the parts in the photo below:

- Upper left hand corner Spektrum Dx6i RC transmitter radio

- Center left - battery pack for the RC Receiver

- Center right - RC Receiver (this picks up the signal from the remote) tiny....

- Bottom center - Sabertooth 2X25 motor controller.  This unit accepts the signals from the receiver and converts it into power for the individual motors.

- Bottom left and right - Test motors

Here is a close up of the Sabertooth Motor Controller.  Notice the green light.. green is good.  The main power comes in from the bottom in the middle and is output on the left and right to the individual motors.  The two white leads in the upper left are from the RC receiver.  They are from two individual channels - basically the up/down and left/right motion of the joystick on the transmitter.

A wider shot showing the bench power source in the upper left that I am very proud of.  It supplies from 0 - 24 volts of juice to test setups like these without having to connect it to the batteries.  Necessary ?  Probably not, but dang - it makes me feel like I may know what I am doing.

So, here is a closeup of the receiver for my own reference.  When I hook this up again in a week - I hope to recreate the results that I had today.  You may notice the channel markings on the receiver... this particular radio is designed for use with a plane or a helicopter.  That is why there are many settings to tweak in order to make is usable as a tank-style motor driver thingy.

Here is a video of my WIN this afternoon.  Again - if all goes as planned, all I have to do is hook up the batteries and motors in the R2 unit - and I should have a droid that moves about the room.

For those who care (and for my reference throughout the build) here are the specs on my setup:

Spektrum Dx6i Transmitter settings:

AERO Mode

Mix 1

Elev -> Aile ACT

Rate  L 0%   R 0%

SW ON    TRIM ACT

SETUP menu / REVERSE

THRO - N     AILE   -  R

ELEV  - R     RUDD - N

GEAR - N     FLAP  -  N

Receiver Settings:

Aux 1 : Battery / power supply (brown wire on top / orange wire on bottom)

Elev : Black Wire on Top / White Wire on Bottom - White Wire output to Sabertooth S1

Aile : Black Wire on Top / White Wire on Bottom - White Wire output to Sabertooth S2

Both Black wires from Receiver are tied together and input on Sabertooth 0V input.

Sabertooth 5V input is NOT used and both Red wires from receiver are capped and unused.

Sabertooth output :

Left Motor - M1A Red wire    M1B Black Wire

Right Motor - M2A Red wire    M2B Black Wire