Introduction: K-9 From Doctor Who

I have wanted to have my own K-9 from Dr. Who since I first saw him on TV back in the 80's. Now that I can, I decided to build one as part of my costume for the Emerald City Comicon in Seattle. I made the decision in January and K-9 needed to be done for the end of March. What follows is a mostly picture documentary of how I put him together. Almost all of the small parts are things I have been collecting for years and were not bought for this project just made to work. The plans I used have moved several times but the most recent place I found them was at Here's the link to the plans for those interested in building their own dog.

Step 1: Plans and Frame

To begin I started by drawing the full sized outline on some scrap styrofoam. Paper or cardboard would work but I had this laying around. Once I had full sized drawings, I used them to determine the lengths needed for the frame. A few pieces of scrap wood and some old casters and it's on wheels.

Step 2: Body Shell

Next came the body panels. I made these out of 1/8" hardboard. This was left over from another project so I didn't have the full 4 x 8 foot sheet. Hardboard worked extremely well for creating the body. I was able to draw the panels right on the hardboard. I then cut the hardboard with a sharp razor knife using light passes and slowly cutting all the way through.

Step 3: Blue Tape and Body Panels

I ran out of the darker hardboard and had to get another sheet. Unfortunately they didn't have the same material. I had to go with a single sided finish board which was slightly thicker and had a rough texture on the back side. This caused some problems but also created a better surface for gluing too.

Step 4: Taped Up Doggie

Lots of cutting and blue tape later and the shell is almost whole. He's a little bigger than I thought he would be.

Step 5: View Screen

The opening for the monitor screen was enlarged from the plans to fit my iPad and allow it to be the display screen. To make the ring around the outside of the monitor screen, I used foam paper cut into strips and glued together to make a thick yet bendable strip the right thickness and width. Then I super glued the foam to the edge of the opening and spliced the ends together.

Step 6: Insets

The inset panels on K-9's lower sides were more than a little tricky. the panels are all at different angles and trying to hold everything together while I glued it up was frustrating to say the least. I used lots of blue tape and hot glue on the corners to hold things while the super glue set.

Step 7: Head

The head also turned out to be quite tricky to glue up. I'm guessing the original was made of metal panels that could be bent and formed. The hardboard can be bent somewhat but won't hold the shape. I had to make several wooden frame pieces with multiple angles on the ends to get everything to curve and line up right.

Step 8: Getting a Handle on Things

To control my K-9 I decided on a leash set up. I took a length of nylon rope and removed the inner core. Then I cut the end off of a Cat-5 computer cable and slid the cable through the center of the rope. For the handle I used a short length of PVC pipe. The control buttons are micro buttons salvaged from an old printer panel. I cut the pc board around the buttons to get one strip with two and another with three buttons. I then carefully drilled matching holes in the PVC to just fit the micro buttons. I passed the cut end of the cat-5 cable into the handle through a hole drilled into the center. After soldering the buttons to the cat-5 cable, I pulled all the extra wire back into the handle using a piece of leather cord I had laying around. Once glued in from the backside, the buttons just extrude out above the smooth handle. The end caps were made from two plastic drawer pulls. I broke the center out of the pulls and shaved the inside slightly, to get them to press on to the PVC pipe. After testing the buttons to ensure everything worker, I filled the handle with hot glue to prevent the buttons from pushing back into the handle. As an added bonus the handle looks like a robot dog bone and works great for pulling him over rough sidewalks and over door frames.

Step 9: IPad Display Screen

After painting the screen side panel and getting the iPad lined up, it looks pretty good. I burned several episodes of Dr. Who into my iTunes so I can play them on the screen.

Step 10: Train Drive, Drive Train

To move my K-9 I used the drive system from a kids ride on train. The train is rated for up to 50 lbs so I knew it would move him. I mounted the motor/ wheel assembly to a hinged sub frame to allow the wheel to move up and down, somewhat. I planned to put the batteries in boxes on the subframe so that most of the weight is riding on the wheel for better traction. I attached the brake assembly from an old wheelchair to the front of the sub frame to allow me to lift the wheel off the ground in case the batteries died or something malfunctioned. With the drive wheel off the ground the caster wheels roll smooth and K-9 becomes a giant pull toy.

Step 11: Neck

I decided to use a fixed neck for now. Later I might try and make his head move. I made the bottom circle with a large hole saw and some scrap plywood. I had to guess on the angle but by comparing the plans and pictures to what I had I think it came out about right.

Step 12: Drive Motor Fit Problem

I didn't measure the spacing and the motor leads hit the inside of the panel. I moved the motor and wheel over as much as I could and shifted the whole shell slightly to the side. Even with that it just barely clears. Note to all builders, measure twice, cut once.

Step 13: Ear Drive

Using some 1/4" lexan I made a bracket for the ear drive system. I hooked a toy gear motor to a small crank unit taken from a car tire compressor. A small lexan link connected to some old RC car bits and I have two shafts that rotate in opposite directions. The ears themselves are made from short lengths of fiberglass rod and stainless steel screening. The blue around the outside is 1/8" airline sliced down the length and super glued on. The ears fit down into the shaft in a groove cut with a jewelers saw and are held in by small screws from the back with RC ball connectors as the little forward directional antenna. The shafts ride in short lengths of lamp tubing and have small lengths of shrink tubing around them acting as bushings.

Step 14: Eyes and Tail

The eyes are small flashlight reflectors. For the tail I commandeered one of my daughters toys. Along with a piece of brass pipe and some RC truck springs the tail can "wag" back and forth when touched. I plan to make it powered at some point. The white grid is a couple pieces of small shelving that fit almost perfectly inside the shell on top of the lower panel brackets. This allows me to pack stuff into his top half like a trunk.

Step 15: Eye Panel

The plastic panel that makes up his eyes was made from one large piece of lexan and several small strips "glued" together with MEK. The back side and the area between the strips will be painted red after everything is fit together.

Step 16: Inside the Head

This is the view up through the head with the lights on and the panel in. You can see the end of his antenna hanging down in the middle. The second picture shows the tiny little space I had to work on K-9 in. While some might see a cluttered mess, including my wife, I believe in organized chaos.

Step 17: Nose Blaster

I knew that one of the main things that had to function was the nose blaster. It not only needed to light up but I needed to make it extend and retract reliably. I started with a piece of copper pipe as a prototype and then went with a small length of stainless steel tube that I've had in my parts bin for years. Inside the end of the tube, I glued a 1/4-20 nut. Using a 6" 1/4-20 carrage bolt inside the tube, I could spin the end of the bolt and if the tube is kept from spinning it will move up and down the bolt. Some 1/2" HDPE made a perfect low friction mount for the tube and I made some small brackets to hold it to a lexan guide. I secured the tail end of the carriage bolt through an old RC car hub with bearings that were almost perfect. To spin the bolt, I coupled the gear box out of a thrift store RC truck through a length of PVC air hose and half of one of the "dog bone" shafts from the RC truck. This worked out perfect, I can take either part out of the head without having to disconnect anything, they just plug together.

Step 18: Mounting the Blaster

The guide rail/frame for the nose blaster is attached to two small blocks in the nose and to the back side of the frame member, just under the eyes. To keep the gear box's differential from free spinning, I used a small screw and connector to lock the rear output.

Step 19: Missing Pieces

Up until now the rear was held together through the side panels and some clamps. A couple of very odd angled pieces and some JB weld and the rear frame is all one piece. Now it just needs the last little panel. At this point, I also made the holder for the iPad. Another piece of lexan (I got a bunch of this stuff as scrap and it looks cool) and some air filter replacement wing nuts from the hardware store and I can tighten the iPad in but not worry about crushing it.

Step 20: Coming Together

A quick look at the basic parts going together. If you look to the top of the shell you can see that I have made two frame strips and now the front and back are connected permanently. I also cut two strips of hardboard to act as guides in the front and back. These are glued to the base plate and form the bottom of the front and rear body panel recesses.

Step 21: Hooking Up the Leash

The leash is attached with a carabiner to a rather robust handle. The connector from the leash sneaks inside through a small hole at the top of the recessed panel. Inside the leash, the cables from the head connect to standard Cat-5 connectors. These are attached to the main frame with velcro to allow the shell to be removed.

Step 22: Paint

As everything starts to come together, I decided to get some of the painting going. Here you can see the main base getting some auto undercoating and the inside of the shell is getting a Tardis blue primer coat. Ok so it's really just a regular blue house paint but it looks pretty close to the Tardis' color to me. I also gave K-9's head some gray

Step 23: Batteries

Not much to look at here. 6, 6 volt batteries. One will run the toy train motor, now K-9 primary mode of transit, for about a half hour with a 50 pound child on it. I should get several hours out of them tied together in parallel. I'm going to use 2 together in series to get a 12 volt supply and 4 of them in parallel to power the motor.

Step 24: Powered Up

Now that I have the batteries, it's time to hook up the relays to make things move. I am using relays for most of this project for several reasons. First, I have a bunch. Second,it's relatively simple to figure out what is going to turn on or off using a relay. Third, and most important, is that the current draw for this motor would require a sizable speed control and some other way of connecting everything. With the relays, I can have a small voltage go through the leash and its tiny buttons, activating the relay to connect the motor directly to the batteries. I am also using solder less breadboards for the relays and electronic components so I can change things easily.

Step 25: Almost Ready for Show

So he's almost done. He drives and talks and his ears will move. However I am still working to make his nose blaster fully functional. The original concept was for a separate control board that would cycle the blaster in and out with a single button and then trigger the sound with another button. This proved to be impractical. I am now working to make it a two button system to extend and then trigger the sounds on one button and retract and trigger different sounds on another. After all was said and done K-9 made it to Comicon but had some functionality problems. The biggest problem I ran into was that my relays were powered from a single 9 volt battery and of course that was the only thing I didn't have a spare of. As the battery started to die the relays wouldn't latch and K-9 would refuse to move. I ended up dragging him around for awhile till I could rig up a different power supply for the relays. Even with the problems, K-9 was still a huge hit and we couldn't walk more than 20 feet before being stopped for pictures.

Step 26: Upgrades

Well after the issues at Comicon I knew I needed to make some changes. To start with I reworked the 12 volt power panel to include a two position switch which will be used to change the motor power from 6 to 12 volts. I also wired a 12 volt car socket through a fuse to run the adapter for the iPad. The 12 volt system also powers a set of computer speakers to give K-9 a much louder voice. One speaker is mounted in the head and the second (with the volume control) is mounted inside the body. The Adafruid sound FX board got its own special place and I modified a battery holder to give it the lower voltage that it needs.

Step 27: Wiring the Nose Blaster

With all the major parts finished it was time to get the blaster working. I decided to use two buttons to run the blaster, one button would move it out and the other would move it in. I wired the limit switches so that each circuit went through the normally closed side. With this set up I can push the buttons and the motor will run the blaster in or out until it gets to the switch and then it stops. I also wired the "out" limit switch to activate one of the sound files and turn the blaster light on. Now all I have to do is hold down the button and his nose will extend and then he will do one of his sayings. I can then retract the blaster just enough to reset the switch and then trigger it again for the next sound file.

Step 28: Final Assembly

Finished! Well for now. Now that the wiring was all set it was time to put him back together, Assembly is really quick. The chassis, main frame, head and body panels all just screw together with 1/2" sheet metal screws and a couple of sheetrock screws to hold the head on. As you can see he also has a new neck made of heavy duty PVC and not the cheap dryer hose from before.

Step 29: Done, for Now.

Here he is, K-9. He is not quite fully finished, he needs more body work and some more paint to cover the blue edges. However just about everything else is finished to my satisfaction. Or it is until I decide to make him full RC control and need to build a whole new chassis for him. That will have to wait till next year though. Thank you for checking out my instructable and I hope this helps someone else build the K-9 of their dreams too.

Step 30: Sound Files:

The sounds of K-9.

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