CAT 573C Feller


LEGO takes up space.  We all know this, and yet we still seem to try to cram as many working functions into a MOC as we can.  Sometimes it works out well.  Sometimes we have to scrap a few functions.  Other times, the functions are so dense you really cannot believe you got it to work.  This is the story of my wheeled feller.

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CAT 573c Feller

I have been thinking about making a feller for about two years now.  It is a project I have never seen done before, with the exception of two tracked fellers (OK, and my other one).  Over this time, I have been planning, acquiring parts, and making plans, and over the last four months I have been building.  Nothing I have made has been so complicated or so dense.  There is no space left.

As I always do, I stared with the dimensions of the vehicle.  The schematics for the CAT 573C were easily available, so I stared with the chassis.  I knew space would be an issues, so the driveline had to be simple and compact.  The Power Functions XL motor would be geared down 3:1 and mounted just behind the rear axle.  A drive shaft would move through the steering pivot to the front axle.  The rear axle would have simple pendular suspension.  The steering would be completed by two linear actuators placed on either side of the pivot with a PF M motor on top.  Simple enough.

From here, things got complicated quickly.  The MOC would have four remaining functions.  The feller saw, the grapple arms, the feller tilt, and the feller lift.  Since trees are rather heavy, fellers are designed with as many of the system mechanics behind the rear axle.  As such, all of the functions I would add would need to be in the rear, as the front would not have any space.  I quickly learned this would not work.

Eventually, I found what would fit.  The IR Receivers would make up the rear bumper, and the battery box would be directly over them, off to the left.  Two PF Ms would be on the right and would drive two mini Linear Actuators.  These would move two pneumatic valves. These pneumatics would move the lift function and the grapple arms function.  An air tank would supply the pressure from a pneumatic pump placed on the driveline.  Another PF M would be placed over the front axle to give the feller head the tilt functions (it should be noted, 7 designs, and five weeks were spent on this feature alone).  The final PF M was in the feller head, and would drive the feller saw.

After packing, repacking, and packing again, all the features we set.  Then all the cabling and hosing were placed.  No easy task, as I was running out of space, and 25 or so hoses, and 10 cables take up a lot of room.  I added some comfort features to the cable, including a (half) chair and a roll cage.  And so Mr. Technic could get in, a little step.  Then a lot of paneling for the rear, including some access doors on the rear, and the model was done.  Here it is in action.

As you can see in the video, the MOC worked well, but some of the functions did not work as clean as I would have liked.  The drive and steering were fine, with an easy drivability.  There was a lot of mass in the back, so sometimes the torque from the drive motor would cause the back to tip.  The saw worked well enough, and for the most part so did the tilt, but the pneumatic lift struggled.  It was a little overloaded because the saw unit was too heavy.  The grapple arm worked well, but for both pneumatic rams were hard to control.  As always with LEGO pneumatics, they too often are off or on.

Until the next MOC, happy building.

Spitfire Mk IIa


I am not a very ambitious person.  Sure I made it through college and graduate school, and have managed to work well in job for a while now, but for me to do something challenging, takes a lot of convincing.  It doesn’t happen often.  This project was a little bigger than it should have been, and I got in over my head.  This is not the first time this has happened (1, 2).  The project was interesting enough for me to keep moving forward, even after six months.  I present my 1:12 scale Spitfire Mk IIa.  I hope you enjoy the work.

View the full gallery here, and the work in progress gallery here.  Flickr set is here, and full instructions may be downloaded here.

Spitfire 3/4

First, the whole reason I did this project was because of the excellent Baby Twin Otter of Cpt. Postma completed two years ago.  If you have not yet seen this creation, take a look at the above link.  When I first saw this model, I went home a made his variable pitch propeller   This was the first step to my Spitfire, though at the time I did not know it.

I chose to do the Mk IIa version Spitfire for a couple of reasons.  First, the model had to have a three blade prop, because I wanted to use Cpt. Postma’s design.  Spitfires stopped using a three blade prop somewhere in the middle of the MkV series.  Second, I wanted to model a eight gun variant, rather than the cannon variant because I think it has a cleaner look, and I love the red and yellow leading edges on the eight gun variants.  Finally, while it would have been great to do a early model Spitfire with the dark tan camouflage  adding both the dark green and dark tan would have been too expensive, and even more ambitious.  I found a number of pictures of a certain MkIIa with all the features I wanted.  I chose a Spitfire flown by Lt. Tomas Vybiral, who was a Czech pilot with the French Air Force.  The plane was Spitfire P8081 when he flew for the British in Squadron No. 312.  It had simple markings for me to recreate, a camouflage pattern I would be able to do (read afford), and I found some good documents to help my modeling.

Next came the internal planning.  The Spitfire would have working ailerons  flaps, rudder, and elevators (with correlating pilot controls), prop, prop pitch, V-12 engine, and retracting landing gear, all within the 1:12 scale.  Once I had the dimensions calculated, I started placing things in a simple “placeholder” model on my floor.  I constructed the engine, the propeller spinner, pedal/joystick assembly and placed them in the placeholder.  Then I made the placeholder 3D.

It took two months to get the rest of the internals all set.  The required moving various parts of the 3D placeholder, and adding additional parts.  The joystick is connected through various liftarms to the rear elevator, and by axles to the ailerons   The pedals connected though a shaft to the rear rudder.  You can see the gears on the rudder.  The flaps have a simple lever in bottom left side of the cockpit.

The rest of the functions are controlled via Power Functions.  The small 8878 battery box is placed behind the cockpit, as is the IR receiver.  A PF M is housed under the V-12 and drives four mini linear actuators for the landing gear.  It is strong and simple, and works well.  It does not have the correct Spitfire landing gear geometry, but if someone can figure out a way to do it at this scale…well, I can’t figure it out.  A second PF M is used to power the propeller   It is placed directly behind the V-12.  Finally, a third PF M is placed behind the V-12, and works through a system of gears to power two mini linear actuators to move the pitch of the prop.  It’s messy inside, but it has everything I wanted.

After the internals, I had no idea how hard the rest of the Spitfire would be.  LEGO, you need to make more parts in Dark Green.  I know how selfish that sounds, but it would have been more helpful.  Thank to some newer sets, like the 10226 Sopwith Camel, and the  21016 Sungnyemun, it made it much more possible, but still limited me in many places.  I spent the next four months acquiring parts, and placing small plates over the rest of the plane.  With some help on the roundels from Dieterr89, it eventually came together.   The bodywork took a long time.  Too long.  And the lack of some parts in Dark Green forced me to make some concessions.  The canopy frame should be all Dark Green, but it was not going to happen with what is available.  The camouflage is not as clean as I would have liked, and there are some abrupt steps where some plate limitations made the transition for one part to another not smooth enough, such as on the rear fuselage.  Also, try as I might, I could not get the leading edge of the wing to be perfect.  The dihedral did not help either, nor did the yellow leading edge.  Also, the gaps between the control surfaces and the fixed part of the wing and stabilizer was more than I would have liked.  But this has happened before.

I am please with how it turned out, but there are some parts that I wish would be better.  I never seem to remember this when I start a project in this scale, but free moving functions just do not operate well as you hope when you keep adding parts.  The control surfaces work, but they could be smoother and lighter.  The powered functions worked flawlessly. I was very please with the way the markings turned out.  They are not as flush with the plane as painting would cause you to believe, but they make the Spitfire clearly identifiable.

My father would always tell me “never say never,” but it may be a long time before I do another large plane.  But I guess I said that back in 2008.

I hope you enjoy.  Thanks for reading.

CAT D5K


Construction equipment was pretty much designed for LEGO Technic.  I learned this while designing my MB Axor Refuse Truck.  Yellow bricks are pretty popular and accessible, the equipment usually has many functions which can be replicated, and working models with power functions can be made to reenact various construction projects for great playablility.  After finally getting some large track links, I figured it was time for me to do a bulldozer.

I wanted to model the CAT D5K for a couple of reasons.  First, it used a two wheel track for each side rather than a three wheel track for each side.  Second, I wanted to do something by CAT.  Third, I decided on the D5K because for dozers of this size I think it looked the best due to its stance and overall balance.  Plus, when I started looking at the scale of the dozer I was to model, I learned the D5K would work best with the parts needed such as the tracks and blade, and work with the internal space allowed.

The base D5K really only has three functions: drive, blade lift, and blade angle.  I had no intention to add a ripper, because, frankly, I ran out of space.  Space became an issue very early.  I had 9 studs to work with between the tracks, and I needed to add four motors, a dummy motor, a battery box, and two receivers, all while retaining the appropriate look.  All the gearing had to be compact, and the linear actuators needed to be placed efficiently.  The real D5K has a manual adjustment for the blade pitch, but all of my designs left something more to be desired, so I took it out.

Both tracks would have their own motor, and I wanted to link them to a dummy engine, which required a differential.  I connected the motors directly to a worm gear which drove a 8z gear.  This gear was on the axle for the rear drive wheel, and connected on the other end to a differential which connected both drive wheels.  This differential functioned as a power take off for the dummy motor in the front of the bulldozer.

Two more motors were placed under the dummy motor.  One connected though a 12z/20z gear reduction for the blade angle.  It proved difficult to supply power for the blade angle function through the blade tilt pivot without taking up too much space.  The second motor was used to adjust the blade height.  After a simple reduction, two mini linear actuators were used to move the blade up and down.  It worked well, and was plenty strong.

I added the battery box under the driver’s seat, and placed the two IR receivers in the top of the cab.  It was not optimal aesthetically, but it seemed to work well for control.  And again, I just ran out of space.  I worked on the body, gave the model a working hood, and built a cabin.

The model worked well, but building with tracks is always a little bit frustrating.  Like it or not, LEGO plastic will never be fully smooth, and this is compounded with the track system.  Also, I found that the dummy motor would lose its connection to the drive wheels, as the axles connecting to the differential would slip out every once and a while.  This seems to be a commom problem with Technic builders, so we will see if the new axles will help.  I liked the size of this model, and it had a good amount of functions.  Now I need to use the tracks for something else.

Maybe another tank.

The full gallery may be found here.

Mercedes Benz Axor Refuse


I am a big fan of garbage trucks.  For some reason I find the combination of a smaller truck,with many features all with a complicated compaction device is a great basis for a complicated LEGO Technic model.  Plus, trucks are fun.

The hardest part was going to be the rear compaction device, so that is where I started.  I decided to use a Geesink Norba design as it would give me the largest opening for the trash in the rear because the mechanicals would be on the bottom on and the top of the opening.  13 studs wide is not much space.  In addition, this would allow me to have the rear hopper pivot up to let the trash out when it was full.  I would need to have three functions going though the pivoting hopper.  One at the pivot, and two connecting at the base when the hopper was closed.

The dumpster lift would be driven through a knob gear when the hopper was closed on the bottom.  The compation device would be operated with a gear on the bottom and a mini linear actuator on the top.  This mini linear actuator would also function as the opener for the rear compactor.  All the motors would be housed on the bottom, with one motor placed next to thebattery box.  The extractor would be operated by another mini linear actuator using a scissors mechanism to move the ejector plate.

The chassis was constructed with a PF XL in front of the steering axle.  The motor would power both the drive, and the extractor changed by a changeover.  The steering motor is placed on the right of the truck.  On the left, another PF M motor powers both the dumpster lift and the lower hopper compaction device.  All power came from a 8878 rechargeable battery box, through two PF IR receivers, and powered four motors: One XL for drive and the extraction plate, one M for steering, one M for the dumpster lift and lower compaction, and one M for upper extraction and hopper opening.

The model worked well, particularly steering and the drive.  However the extraction and the hopper opening was a little less reliable.  The hopper was too heavy for a single mini linear actuator, and the compaction device was not stiff enough.  It happened to get caught on some of the internal edges on the inside of the hopper.  The next garbage truck will need to be built a little more sturdy.

The full gallery may be seen here.