Sunday, April 29, 2001

RCKillough

While reading news in lugnet.technic I found a link to a very interesting page, Leo's LEGO Designs, there I found this page describing a pretty uncommon propulsion system named after it's inventor, Killough. I recalled that I had seen it before and that I thought it moved pretty spectacularly. So I decided to build one myself. I remembered that the one I previously saw was controlled with the Mindstorms RCX, but I went for remote control using the same radio control equipment I always use.

After studying several other LEGO Killoughs I left the computer and went to my building table and four hours later I was done. It took about three hours to assemble it and one hour to make it stronger so it would not fall apart and tweaking the RC stuff.

I really think that you should build one of these babies of your own! They are much fun to play with!

How?

Since this is a pretty remarkable"vehicle" I thought that I should try to explain how it moves.

It uses six wheels that are rounded and spins them in wrong direction, tilting them around instead of rolling them. The "normal" spinning axis is free to rotate. The reason there are three pairs of wheels is that when one wheel tilts it will loose contact with the floor unless it lowers it's chassis (gravity will) or something else holds the chassis in level, here's where the additional wheel comes in play. The wheels are mounted with a 90-degree displace to each other, thus, when one wheel tilts so that it looses contact with the floor, the other wheel gets contact instead. So there will always be a wheel that has contact with the floor.

Here is how that works, looking at the Killough from the side and only drawing the wheels. The wheels tilts in the direction of the arrows.

First


then tilting 45 degrees


finally tilting another 45 degrees



To drive in a straight line forward, two of the motors are turned on in different directions. Looking at the picture, it's the "red" and "green" motor that's turned on, creating the force displayed by the orange arrows. They add up to the black arrow and the platform moves in a straight line "forward". If the axles in the wheels were fixed this would create a lot of stress on them from the friction against the floor, now they can rotate freely and there for there is no skidding and the platform moves with ease.



If the green and red motor changes directions the platform will travel "backwards" or down in the picture.


video

If the red motor is turned off and the blue motor is turned on instead, the platform will change it's direction of travel as displayed by the picture.


video


If, in the previous case, the red motor never was shut off while turning on the blue motor the platform would perform a pretty big turn since the blue motor causes the platform to rotate..


video

If all three motors turns in the same direction the platform would rotate around it's center and not move in any direction.


video


If only two motors drive in the same direction the platform rotates around the center of the third pair of wheels. In the picture the red and green motor drives the platform around the center of the blue pair of wheels.


video

I forgot about only driving one motor when I played with the platform, but it causes the platform to rotate around the other two motors shared center.


Of course one can swap between these behaviors at any time and this is what makes the platform so versatile and maneuverable. And also so difficult to drive nice, I had some good exercise when I collected my brothers sons toys in a nice pile :)

video


Here is an overview pic to start with. Notice that I even took the time to cut the background out. The main factor that made me invest in a new camera is the trouble I had with video camera pictures and cutting out the background. Now I love this :)




It's always a challenge to fit non LEGO elements in the projects and rubber bands works OK mostly.




Tipping the Killough on it's side displays the underside, as always :) Notice that I added extra support in the center in form of black 1x6 beams.




Zooooming... I had to use some 1x2 plates with one centered stud to make the battery box fit. I still had to use a little more force then normal to stick it there so it don't fit great but it fit's good :)




I also used some external support beams. Notice the use of half beams to connect the technic beams with each other. They provide for a stronger fit then normal 1 x Y plates.




The platform is built up using three of these setups. There for this was a quick build when I had figured out how to make one I just built another two copies. cklickety-brick :)




And flipping... Notice the sparse gearing for less friction.




And as always, here's that ON | OFF switch fetishism of mine...




Displaying more radio equipment, here is the receiver.




Servo. It took some time to get that polarity switch up there. I cheated and used a rubber band to keep the parts together. I never tried with out it so I might have been fine w/o cheating but why take a chance?




Side view. It don't have very much of ground clearance but it's pretty though in rough terrain like carpets, door steps and thick cables.




Top view. Have you perchance noticed that I arrange my pictures in alphabetical order?

So, what's to see here? Perhaps the blue antenna mounted in a setup of 2x4 technic plates and a short pin? Nah...


Tuesday, April 24, 2001

Hexapod Study

First!

Before you flame me for owning six turntables and 12 large pneumatic cylinders I must say this; A year ago when I had just crawled out of my dark ages cave and started searching the net for AFOL's I was amazed when someone had more then one turntable and I thought I'd never own one myself!

Then, in August 2000 I bought my first 8480 Space Shuttle and I had my first turntable, after that I rather quickly bought another 8480 (on sale, I could have walked over dead bodies to keep it in my arms after I had picked it up) and two 8462 Tow Trucks. Now I had four turntables and six large pneumatic cylinders

I then ordered some large cylinders from LEGO Service while they were still shipping spare parts..

In Mars 2001 I bought me another two 8480 Space Shuttles when I was lucky enough to find them in a toy store in Sweden.

What I want to say is; I'm crazy enough about LEGO to spend a lot of money on this hobby, hence the parts. If you want to feel envy, feel it for my luck in finding those 8480 and having the money to spend at the time!

:) This was written mostly as a joke to a friend of mine who claimed that he hated me when he saw this study IRL :)

Information

After the Hercules I felt that a robot might be in order before my next serious project. I thought about the robots I've done so far and decided I liked the walkers best. I had already done a Biped and a Octapod so why not do a Hexapod?

Thinking some more I decided I wanted to do a pretty large platform that could carry my radio control equipment and maybe some cool weapon or something.

To build large and simple I thought that the leg should have three joints, a "knee" and a "hip" and also the turning function in a hip. I used MLCad to test a idea I had. One pneumatic cylinder for the "knee", one for the "hip" and a large turntable for the rotation in the "hip". It proved to be doable in MLCad so I was thrilled when I found out I own 12 large pneumatic cylinders, at first I counted to eleven but I had forgot one used in my Hercules at the moment.

Yes, I plan my next project while building the current. That's probably why I always get sidetracked and loose interest in the current project, ah well...

The reason I wanted a "knee-joint" was that I wanted the robot to be able to do nice turns and also walk like a crab, sideways by not using the turntables and also forward by not using the knee-joints but the turntables and hip-joints.

I made a nice control scheme for how to make all this work with my five channel radio.

After I've built the project as I had planned I realized that the legs were far to weak to give the performance I wanted so I skipped the knee-joint and made that part stiff and took the cylinder to make a dual cylinder in the hip-joint.

Now the legs were strong enough but I got serious concerns for my turntables, they tended to separate when I drove around the platform, and that was before adding any weight. Afraid to ruin 6/7ths of my turntable collection I decided that this project was a design study and that the study proved my theory wrong in real life. Damn!

I might fix this turntable issue by placing the turntable underneath the platform so that the platform stands on the legs instead of hanging in them, more on this further down among the pictures when you have a chance of understanding what I mean. It would have been a total rebuild of the drivetrain to make this at the stage I was in so I decided to lay this to the past and perhaps come back to the idea when I feel motivated enough. I build for fun and so should you :)


The numbers represent the name I gave the legs. The circles are the turntables, the colored rectangles the legs and the color markings show witch legs move in unison.




For example, when the robot walks forward it first lifts the blue legs, 1, 3 and 5 from the ground. Then it turns all turntables. The blue marked turntables turn in one direction, putting the leg forward and the red ditto turn backward thus pushing the robot forward since the red legs are on the ground.

The schematic picture to the left tries to describe this state. The arrow is the direction of travel.

Then the robot puts down the blue legs 1, 3 and 5 and lifts the red legs instead, 2, 4 and 6. Then the motors drive the turntables so that the red legs moves forward and the blue legs backward (now on the ground) so that they pushes the robot forward. And so on...





When the robot turns, the robot don't move all red legs forward and blue backwards and vice versa. Instead one of the colors on one side moves back while the others in the same color moves forward, giving the robot a form of tank steering.

Like this (I'll try to explain):

First the robot lift all it's blue legs (assuming all six legs were on the ground), then leg 1, 3, 4 and 6 move forward while leg 2 and 5 move backward. This makes leg 2 pushing it's side forward while leg 4 and 6 pushes their side backwards, thus the robot has to turn (unless something brakes).

Now it should look like the pic below. The arrow is the direction of travel.

Then the robot puts down the blue legs again and lifts the red legs instead. Now the leg movement reverses, leg 1 and 3 pushes their side forward while leg 5 pushes it's side backwards.

I hope you understand this, it took me a while to grasp it my self while building, how the legs should move I mean :) I'm not sure if I could explain this in Swedish either LOL!





This is the first version with the knee-joint that I skipped in the second half-time.

Did I just use a sport metaphor? I did, didn't I? Yuck..

Anyway, in this pic leg 1, 3 and 5 are raised so the robot stands on legs 2, 4 and 6. Leg 1 and 3 is stretched out using the knee-joint.





Another angle, same status.




Same status, yet another angle.




Detailed view of the leg.




When the robot moves, either forward/reverse or turns, the corner legs always move in another direction then the center leg. Thus the drive axle had to spin in a different direction at the center then out in the corners, this is how I made that work. I first thought about several gears and chain links and stuff, then I realized this would work with less friction. It felt great to fell the brain kick in like that twhapping my stupid first thought. I wish it could happen more often :)




This is the second version of this hexapod as far as I built it. Now the knee-joints are long gone and the knees are stiff. I had to skip crab walk and smooth turning when I skipped them. I might have put in some springs in the knees to allow smooth turning never the less. What a thought. Gotta try that on my next hexapod!




One set of legs lifted from the ground (I don't know what numbers but it does not matter :) ).




Close up of the "hip". The leg is mounted on top of the turntable and the chassis in the bottom. This means that the robot "hangs" in it's legs instead of standing on them. Pretty stupid construction of me there. But at least I know how to make it next time :)




This is what the turntable looked like after a short drive. When I noticed this I chickened out and decided to make this an ex. project.

Placing the chassis on top of the turntable and the leg underneath it would probably solve this. It meant to much work however so I never tried it.





Top view. Why do my tummy feel like eating spaghetti now?




Close up of the drive train. I had a similar setup in the other end of the robot although reversed. The two motors drive the same axle and the other drive axle is slaved via the gearbox setup. I had a gearbox in order to allow the steering and forward walking. See schematics in the beginning of this page. When it walks forward the two drive axles has to move in different directions and when it turns they have to turn in the same direction, hence the gearing.




Looks cool eh? :)

It has a nice ground clearance and it seemed to be able to do a lot of terrain driving, damn I would have loved to take this one out in the bushes. Stupid turntables, or is it stupid designer? Nah!





The bottom is nådd! Sorry, Swedish joke. This is the chassis any way.

Not much to see, I tried to keep it flat and nice for off-road action.

Well, it would not have been much action any way, it drove painfully slow...





Zooming in underneath this beast the secret of the gearbox is visible. The two z24 gears are there to reverse the direction of the output shaft. I used a odd number of gears on one side of the gear lock mechanism so it had to be a even number on the other side. Power comes in on the center axle from the motor, the two axles in the top and bottom of this image are the drive axles for the turntables. More on the gearbox on page two.




Continuing where we took off, here's another shot of the gears. I like gears :)

The difference from the previous shot it that here some of the gears to the left is visible that were hidden behind a beam. Also, the two z24 don't show off as much.





When I made the gearbox I made it as another part while the platform with all it's legs and such had to wait. I found it more practical to make a smaller version with the parts that were relevant and work from there. This way I could explore the limits w/o having to get tangled in a lot of pneumatic hoses 8) Uhm, this reggae music is making me wishy-washy, what happened to the metal that was pumping from my speakers a minute ago? Bah!




Another view of the drive train. Notice that I mounted the engine upside down on the yellow gearbox. I fixed the gearbox to the beams using 3/4 pins, the dark gray type you know..




Before I came up with the version above this is what I made. It uses 17 gears and one chain instead of 11 gears. Also, this version has two gear pieces that has to move in place in order to shift gear. Not good, so I decided to give it another go and then the version above was born. It's good to redo things when building.




Another shot of the first (not used) gearbox.




And yet another. Why do I even bother to tell ya' folks I failed the first time and then show you so much photos of that failure? It's beyond me and far in on the intelligence of a hen! (Swedish saying translated word by word, always fun). I need to change this music!




Caught in the middle of a step..




Another view of said step. The center legs are parallel so this baby is walking, not turning.




A cool feature was when I raised all six legs and let the robot lay down on it's belly. It looked nice when I "told" it to get back up again :) It always raised one end first. Probably due to friction/efficiency of the pneumatics.

Sunday, April 8, 2001

Hercules

This is the biggest project I ever built. It's over two meters between the wing tips and is made from over 3000 pieces. This project was in the construction state for over seven months.

It's a 1:20 scale replica of the Hercules C-130J by Lockheed Martin. The C-130J Hercules is a transportation aircraft for the military. The 'J' model is an improvement from the first Hercules and the most visible improvement is the six-blade propeller. For more information about this aircraft, please visit it's official homepage at Lockheed Martins.

During it's construction I got sidetracked several times but at the end I was so short on pieces that I couldn't be sidetracked any more. I was rather sick of building this model and I wanted nothing more then to get it finished and documented so that I could tear it down and build other projects that were evolving within my head. Hence the resulting model is far from my best, never the less it was completed. I feel I could improve the model a lot, but I didn't want to since I was tired of the project. If you feel like it, please finish it ,)

Facts

This project uses 3302 pieces in a very colorful scheme. This is because I didn't have enough pieces of the same color to build it monochromatic. Also, the project is but a skeleton since I don't own enough plates to cover it up. But the Technic line is supposed to be skeleton like and show the internal workings, right?

It has a 202cm (79.5 inches) wing span and approx.. 150cm (59 inches) from nose to tail. It weighs around 5kg (11 lb..). The pneumatic system uses almost 10m (11 yards) of tubing. The project also got six 9V motors.

The Hercules has the following functions:

Elevator rudder, controlled by a large pneumatic piston
Side rudder, controlled by a small pneumatic piston
Ailerons, controlled by two small pneumatic pistons that work in opposite directions
Retractable landing gears, controlled by five large pneumatic pistons
Opening/closing loading hatch at the back, using one small and one large pneumatic piston that work in opposite directions
Steerable nose wheel, using one geared down 9V motor
Main engines rotate the propellers, uses four old style 9V motors
Automatic pneumatic compressor

I built it in 1:20 scale because it's the scale of the Technic man if he would be 180cm (59 inches) in real life.

I used a 1:48 scale model by Italeri to measure the different parts, it proved quite valuable to be able to measure everything from wheel dimensions to length of propeller blades.

I took large sheets of paper and drew templates for the wing, fuselage under carriage, tail and fin. I then built the different parts directly onto said templates.

Credit

I'd like to thank everybody that helped me with the design of the propeller.

Geoffrey Hyde, Selçuk Göre, Andy Lynch, Klaas H. Meijaard, Bram Lambrecht and Jennifer Clark Thanx! And a extra special thanx to Travis Cobbs that came up with the final solution!

Se the request for help here.


A panorama view of the Hercules with a background by Joe Pries. Visit his excellent web pages here.




A 360-degree tour of the Hercules, starting with the back of some reason. As you can see, the engines are running and the tail is a skeleton design.




Moving along to the side, with a slight angle from the back we can see the colorfulness of this beast. I used the panels from the 8448's to cover the largest holes in the fuselage.




Arriving to the nose and front view we can see I used some yellow parts and the flexible cross axles from the 8448. I'm far from happy with this design, but it resembled the shape from the original. It's quite ugly on the real thing too...




Looking at the other side we se nothing new, except it's -well- the other side :)




Almost back where we started we see the 8448 panels on the other side. Also we see the controls on the middle of the wing.




Here we see the pneumatic piston that moves one of the ailerons. It's a quite simple construction really. The only problem I had with this design was to get both ailerons centered at the same time...




Here is the bay doors closed. Note that the door is made from two parts, one upper and one lower part. The lower part also doubles as a ramp.




...and now the doors are open, amazing amazing... :) *sings* "It's a kinda magic. Magic!" Note that the top part opens inwards.




This is how the doors look like from the inside of the fuselage when they're closed. The blurry part in the top left corner is a electrical wire for the main engines.




Now let's open the door and step out and turn around to look into the fuselage.




Okay, this whole door thingie is starting to get a little boring, but here's the large piston that lowers/raises the bottom part of the door.




And here is the top part piston. This one works in opposite direction from the bottom dito. They are both controlled by the very same pneumatic switch. This is the last picture of the door, promise ,)




This is the cockpit window. I used some Technic string to get the different windows correct. As you can see I decorated the cockpit with a couple of chairs, that's it.




This is a picture of the compressor and pressure switch. I used Ralph Hempel's Double-Acting Compressor. Note that since I stole this design it has changed to use medium pulley wheels outside of the z24 gears to allow the compressors a longer stroke.

See a comparison study of different compressors here.





This is another shot of the pressure switch. I had to design my own since Raplh Hempels used a small pneumatic piston and I was all out of them. When the pressure builds up enough the bent liftarm moves the polarity switch so that it cuts the power to the compressor motor. When the pressure drops down again the reverse happens. The amount of pressure needed are "tuned" by the white rubber bands. The pressure built up aint enough to lift the Hercules with the landing gears. But what aircraft uses it's landing gears in such a way?




Here are the controls in a more detailed view. You can see that I equipped the pneumatic switches with longer handels. This is to provide a more accurate control of the pneumatic system.

The polarity switch that has a yellow lever is the main power cutoff.





Pneumatics from left to right; Landing gears, Bay door, Ailerons, Elevator and finally side rudder.

Polarity switches from left to right: Main power, Nose wheel steering, Main engines* and finally compressor on/off.

*I allowed this one to switch to both forward and reverse to simulate the real Hercules ability to make the propellers push, used as brakes. The real version uses tilt of the propeller blades though.





This is a close up of the crew standing next to the plane. The real Hercules uses a five person crew, but my Hercules is simplified so it only takes four men to operate smoothly. Perhaps Lockheed Martin want to buy my design ,)




This is the pneumatic piston that controls the elevator rudder. It's smooth operating piston. One of my best.




Our cat Lisen inspects the Hercules. I did think about shooting a picture of her inside the fuselage but I reconsidered, don't think she would have liked it much...




This is a pic of me playing with the finished Hercules and no, it never crossed my mind to try to fit inside the fuselage..




This is a shot of the turntable I used to move the Hercules around it's own axis to film the 360-degrees. I used a normal technic turntable in the middle, some support beams and four wheels that rolled along a circle on the base plate. This is a quick and dirty construction to get the shot done. My g/f Anki wanted to watch the TV and the sheets I had hang over it was in her way, she claimed :)




As you can see the turntable was way geared down, still it had a lot of slip in the gears before it got started turning...




This is one of the four support wheels on the platform. I was afraid that the wheel would pop off it's pin but it all went smooth :)




Here is a view of the landing gear. It uses two large pneumatic cylinders per wheel pair and the wheels from the 8462 Tow truck. I wanted to use some other wheel but then the dimension of the wheel would have been totally wrong or the Hercules would have looked like it had flat tires. It weighs ~5kg (11lb.) I must remind you.




Here is another pic shot from the inside of the fuselage. It displays the piston better. I can think of a number of ways to improve this design but it was a basic part of the fuselage and would have taken a long time to reinplement and I wanted the Hercules finished ASAP :/




Here is a zoom in on the front and the nose wheel.




Zooming in some more on the nose wheel we can see that is uses a large pneumatic cylinder and a technic turntable. The center hole of the turntable is filled with a z24 gear for steering so the pneumatic tubing had to be drawn on the outside of the turntable. Hence I had to be careful not to spin the nose wheel around to much... I'm pretty satisfied with this design since it's very close to the original.




The biggest difficulty I ran into building this Hercules was the sag of the wing. Even without the motors and rudders it sagged more then 5cm (2") so something had to be done. I could not build it much thicker so it took some thinking.

The final solution was to build a long row of 2xY plates along the main beam of the wing. These plates were placed between the pegs of the beam to make the wing more difficult to bend. It worked quite well. The whole wing with all parts assembled only sags about 5cm (2").

The row of 2xY plates are connected using 1x4 plates to keep the ends of the plates together





Another view of the supporting plates. The total thickness of the wing is still below the limits of the real Hercules (calculating with the scale of course).




Here are a shot to show how the propeller is built. It uses two medium pulleys, some cross axles, three #3 liftarms, 12 #4 liftarms and 12 2x6 Technic plates per propeller. I also added some colorful 1x2 plates on the propeller blade tips for design. A neat design that keeps the blades aligned. The 2x6 plates are mounted with an offset to simulate the rounded shape of the originals tips.




Here is a shot of one propeller in action.




Zooming out to fit two running propellers, guess what the next picture will show ,)




Yes, you were right. It's zoomed out to fit all four of them. I actually had to use two battery boxes to provide the power to these four 9V motors running. If I used but one the battery box shut the power off due to heat buildup. I connected the dual battery boxes in parallel to offer 9V using 12 batteries instead of 6. This helped.




Here's how the propellers look like. It's kinda hard to make it out when they are all blurred... Like I mentioned earlier, the top 2x6 plates are connected with a one stud offset to give the illusion of a roundness to the blade since the original blade aint straight but "bent" like a 'j'.




On both sides of the Hercules fuselage I made hatches that open for easy access and service of the model. This aint realistic ,)

This is the last shot for this page, see more at page three..





This picture displays the shape of the nose.




Here is the small pneumatic piston that controls the side rudder. It was difficult to move the side rudder without moving it from it's extremes in a fraction of a second.




This picture is one of few shots where I managed to get the whole Hercules in one shot. Our living room is far too small :)




Don't try this at home kids! The brave (or stupid?) Technic man is standing directly beneath the propeller!




This is a classic! During air shows they always have someone standing in the hatch waving to the crowd, during flight of course ,) Personally I think the Hercules is kinda boring on an air shows, except when they show their extreme landing techniques. But the air shows around here always have to small landing strips for the Hercules to actually come down :(




Another "from above" shot of the Hercules. This is what it looks like flying over it...




Going back to the detail shots, here's the tubing in the wing. I used pneumatic tubing as well as the styling pipes that come with "modern" Technic sets. It feels good to find use for them :) I actually sort those in my "pneumatic" bin :)




I was reluctant to cut my longer pneumatic tubs so I arranged them to travel a further distance then necessary. The long tubing parts made the whole design kinda floppy, like if there would have been airtanks.




This is a shot of the tubing for the tail rudders and the bay hatch. The left part of the picture is towards the front of the aircraft.




This is the motor responsible for steering the nose wheel. It's geared down via a worm gear allowing for smooth operation. The gear box is also visible in the picture.




In this pic. you can see both of the battery boxes used. I located them both in the front of the fuselage to give the whole aircraft a good center of gravity. I've been around some when my father and brother trims the center of gravity on their model airplanes and I could say that the center on my Hercules is very realistic for flight in deed! It's about an third of the width (not wingspan) of the wing in from the tip of the wing

In the back of the picture the steering motor is visible and in the front is the compressor. I tried to get as much of the weight to the front as possible.





This photo displays the stomach of the Hercules. It was actually strong enough to be lifted to allow this shot. You had to know where to lift and where to not, though. Putting it back on the floor almost generated a total collapse when I near panicked after a better grip. I did not know where to lift ,)




Wave good bye, 'cause the Hercules is moving away to be sorted into it's atoms! Yes folks, this is the final picture. At this homepage at least ,)

If your viewing pleasure aint satisfied yet, browse to my Brickshelf account to see more pictures, uncommented but more pictures :)