Thread: New Crawling Skeleton (Dual Motor) PT. 1

Tweet

NEW CRAWLING SKELETON
(Dual Motor)




[ame=http://smg.photobucket.com/albums/v630/DaveNTracy/Version%202%20Crawl%20skeleton/?action=view&current=0023.flv][/ame]




PARTS LIST
(1) 4 FT. X 1/4" thick Craft Board (or similar) NOTE: This board actually measures 3+1/2" by 1/4" thick.
(2) 5 RPM Gear Motors (Electronic Goldmine)
Section of 1" X 2" wood (about 1 foot)
(1) AC/DC Adapter, 500 milliamp (or more) (Electronic Goldmine)
(1) Foam Skull
(2) Blucky Skeleton Arms
1/2" Plywood (about 1 square foot)
1/2" Diameter PVC Pipe (about 4 feet)
(2) PVC 1/2" 90 degree Elbows
(1) Large L-Bracket
(2) Small L-Brackets
(2) 1/4"-#20 X 1+1/2" Carriage Screws
1/8" thick Flat Aluminum Stock (about 5 inches)
(2) 1/4"-#20 X 1/2" Machine screws
(5) 1/4" Lock Washers
(5) 1/4" #20 Nuts
Coat Hanger Wire
2 Feet small gauge WIRE
(8) #8 X 1" Wood Screws
(2) 1+5/8" Deck Screws
(4) #8 X 3/4" Pan head Screws
(4) #8 Flat Washers
(2) #10 X 2" Machine screws
(2) #10 Nuts
Clear Tubing, 3/8" Diameter (about 15 feet)
3/4" Diameter PVC pipe (about 2 feet)
(1) #10 Lock Washer
(2) 3/4" diameter PVC 45 degree Elbows
Paper Mache Solution
Paper Towels


PART 1: CHASSIS ASSEMBLY

STEP 1: Take the 1/4" thick craft board and cut it to a length of 14+1/2". We need to cut a rectangular shaped notch out of the bottom of the board starting at 2+1/2" from the front end. (This notch will fit OVER the 1X2 piece.) Butt the end of the 1X2 against the side of the craft bd. Trace the shape of the 1X2 with a pencil and cut out the notch. Saw off the front of the craft bd. at an angle (see picture), starting on top about 12" from the rear.
Cut the 1X2 to a length of 10+3/4".



STEP 2: Measure 3" back and 1+3/4" up from the rectangular notch and drill a 9/32" hole. (These motors have a small nipple molded on the back side, just opposite of the motor shaft. This hole will help to position the two motors with their shafts exactly opposite of each other.)

MOTOR PREPARATION: Take the ½” long, ¼” diameter #20 screw and hold it on top of the square hole in the motor shaft. You will see the screw is slightly bigger than the square hole in the shaft. What we want to do is use a screwdriver to force the screw into this square hole, basically “tapping” a threaded hole for this screw, which will later hold the crank to the motor. Use a pair of pliers tightly around the outside of the motor shaft to hold it while using your screwdriver and turn the screw clockwise and force it into the square hole. It might help to brace the motor against a wall or table top (while still holding the shaft with the pliers) to be able to use enough force to get the screw started. Be patient, sometimes it goes easy, sometimes it takes a while. Once the screw starts to rotate into the shaft hole, try to keep the screw as straight as possible as it goes further into the hole. Keep turning it until the head of the screw is about 1/8 inch above the top of the motor shaft. Just leave the screw in for now.

The easiest way to solder the DC Adapter wires to the motors is to open the motor casing and solder the wires straight to the internal motor terminals. Use a small flat head screwdriver to pry the 5 tabs on the side of the motor. Hold the motor with the SHAFT SIDE DOWN and lift off the REAR of the motor casing. --NOTE: Be careful not to allow the inside gears to fall out!-- Lay the motor flat on a table. You'll see the two gold colored pin connectors below the small silver motor. Grab each of these and give a slight pull to remove and discard them. Note the two small terminals on the bottom of the silver internal motor. Cut two 6 inch pieces of spare wire and solder one wire to each motor terminal. (You can lift the motor slightly from it's housing to make room for attaching the wire.) After soldering the two wires take the REAR motor casing and look inside. A small bit of plastic needs to be trimmed from this piece at the area where it sits right on top of the two motor terminals. ( The wire and solder we used, even though it's very small, is enough to cause the two motor casing pieces to not snap together properly when re-assembled.) So just trim about 1/16" of plastic on each side of the little half circle and this should allow the motor halves to go back together properly. Before snapping back together, run the two wires toward each other and down (through the area where the two gold outer pins used to be) and out the bottom of the motor half. One on each side. Make sure they lie flat in the small grooves. Finally, snap the REAR motor casing back on and make sure all tabs are engaged.
Repeat the above steps for MOTOR #2.





Cut a piece of 1/8" thick, flat aluminum stock approximately 2 ½ inches long. This will be the CRANK for our motor. Drill a 1/4" hole at one end.
TIP: When drilling through a thick piece of metal I start with a very small drill bit and then keep using slightly bigger bits until I finally move up to the size bit that I want the hole to be.
At the opposite end of the crank drill another 1/4" hole, measuring exactly 1+3/4 inches from the first hole (center to center). Put one 1/4" nut onto the 1+1/2" Carriage Screw and turn it until it is at the top of the screw. Add a 1/4" lock washer behind the nut. Leave these in place for now. Insert the carriage screw into one of the 1/4" holes. Install another 1/4" lock washer and nut onto the carriage screw on the back side of the motor crank. Turn the nut until the bottom of the it is flush with the bottom of the screw. Lastly, tighten the first nut (near the top of the screw) down toward the motor crank until it is tight. Remove the ¼” screw from the motor shaft and slip a ¼” lock washer onto it. Insert the screw through the large crank hole and screw the crank onto the motor shaft until it is tight.
NOTE: A specialized part called a "Spherical Rod End" (see pic) can be used in place of the carriage bolt as an option for turning the arms. I have found this particular part to be difficult to find, but I used these on my original version of the Crawling Skeleton and they are very useful for this application. Different mounting procedures would be needed to attach the rod end to both the motor crank and the arm PVC.
Repeat these steps for MOTOR #2.





Only two of the three motor mounting holes will be used to attach each motor to the vertical board. (See picture for correct orientation of the RIGHT side motor.) Make sure the small nipple on the back of the motor is in the 9/32" guide hole. The top (unused) motor mount hole will stick up above the board. This will be used later for attaching the rib cage to the unit. Mark the location of the REAR motor mount hole. Drill a 3/16" hole thru the board at this mark. Hold the right side motor in place and position the LEFT side motor on the other side of the board. The LEFT side motor will be mounted UPSIDE DOWN from the RIGHT side motor. This allows the two rear mounting holes to line up for the mounting bolt. Insert a #10X2+1/2" long bolt through the left side motor's mounting hole, thru the board, then thru the right side motor's mounting hole. Add a #10 flat washer, lock washer and nut to the bolt and just hand tighten the nut for now.
Hold the RIGHT side motor tight against the board, making sure the nipple is in the guide hole. Insert a 1+5/8" wood screw thru the FRONT motor mount hole and tighten. Repeat this step for the LEFT side motor. Lastly, tighten the nut on the #10 bolt holding the rear motor mounts. The two motors should be flat against the board and secure now. Lay the 1X2 bd. flat and mark the middle of it. Stand the 1/4" craft bd. up and place the notch over the 1X2 board. Use a large "L" bracket to secure the two pieces together at the middle you just marked.
(NOTE: You may have to trim away a portion of the bottom (unused) mounting hole on the LEFT side motor in order for the unit to sit flat on the ground like it should.)



STEP 3: WING BOARDS: Saw two pieces of 1/2" plywood measuring 4" X 6". Take one board and measure 4+1/2" horizontally and 2" up vertically and mark this spot. Drill a 1+1/2" hole at this point. Trim away the top 1" of the wing board and cut an angle on the front of it. (See Picture). Lay a section of 1/4" plywood under the 1X2 chassis board as a spacer. Stand the plywood wing on its side, flush with the front of the left end of the 1X2. Drill a pilot hole thru the wing and the 1X2. Screw in a 1" wood screw to connect the two pieces. Install a small "L" bracket at the corner on the rear where the wing bd. and the 1X2 meet.
Repeat these steps for the RIGHT side wing board.





ON TO PART TWO....... New Crawling Skeleton (Part 2)

OMG dave, that's amazing! The work is intimidating but it looks amazing

Thanks!
I tried to make this version as easy as possible so that anyone could make one.
But, I will admit some steps seem kind of difficult.
If anyone needs more details of any step of the build, feel free to PM me!

WOW!! can't wait to get started on this!! Should be exciting with my lack of mechanical/ electrical/ everything else ability. LOL

Dave this may be a dumb question, but do you reverse wire one motor so they both rotate the same direction. Because when I wire my motors up and look at them face on they rotate the same direction(clock wise), but when I place them back to back as in your mounting instructions, because they rotate in the same direction one is turning front to back, and the other is rotating back to front, in my opinion, I'll have a skele that will then go in nice neat little circles, so how did you overcome this?

Partsman, yes reverse the wires so the motors are turning oppisite of each other.

DaveintheGrave, Great job on this prop and tutorial, well thought out. One thing I was wondering was , is there a reason for using 2 motors vs. one like this:

http://http://www.servocity.com/html...ar_motors.html

a bit pricey would the 10 rpm be too much? just a thought as something to reduce # of parts and make it a little easier to assemble. Again great prop and tutorial!!

Originally Posted by partsman

Dave this may be a dumb question, but do you reverse wire one motor so they both rotate the same direction. Because when I wire my motors up and look at them face on they rotate the same direction(clock wise), but when I place them back to back as in your mounting instructions, because they rotate in the same direction one is turning front to back, and the other is rotating back to front, in my opinion, I'll have a skele that will then go in nice neat little circles, so how did you overcome this?

No, not dumb question at all. If you read STEP 4 in Part one of the tutorial I have a description of how the motors are wired to get forward motion from both sides. The left side motor (looking from the rear of the chassis) needs to turn counterclockwise and the right side motor needs to turn clockwise. If it's still not clear after you read that part feel free to PM me.

Originally Posted by bfjou812

DaveintheGrave, Great job on this prop and tutorial, well thought out. One thing I was wondering was , is there a reason for using 2 motors vs. one like this:

http://http://www.servocity.com/html...ar_motors.html

a bit pricey would the 10 rpm be too much? just a thought as something to reduce # of parts and make it a little easier to assemble. Again great prop and tutorial!!

Thanks, bfjou812! That link takes me to a RoadRunner page of some sort, so I can't see the motor. Is it a dual-shafted motor? I built my first two crawling skeletons using a dual-shafted motor, but they weren't available anymore.
I used these motors because they were cheap and so am I. LOL
I don't think 10 RPM will be too fast, if it's affordable. When I have time I'm going to try making one with a 24 RPM motor and see what happens!

very cool skelly.

Yeah , I think it has something to do with switching to IE8, tthis isn't the first time it's done this. Anyway, the web site is ServoCity and the motor is in the robot section. It is a thru shaft motor, a portion of the shaft sticks out on each side of the motor. Hope this helps, sorry about the bad link!!

Try this Robotzone Gear Motors

It works I edited it on my laptop, IE6!!!!