8081 RT


I have said it before; I really like set 8081. It has so many possibilities for improvement. After talking a look at RM8‘s design, I thought I should do a street version of the 8081 to follow up on the 4×4 8081 I built a while back.

The full gallery can be found here, and free instructions can be found here.

8081 RT Front

I took the existing bodywork and frame of the 8081, and chopped out the rear suspension unit to revise the rear suspension design. I wanted an independent setup with a differential. As I have used a couple of times before, I used a floating differential design. The differential is attached to the driveline much like a live-axle set up, but is connected to two independently mounted wheel hubs. I have used this before, and I like the way it works. It allows for a driven axle with independent suspension in a very narrow setup. This way each wheel can move independently, but it does not require two universal joints on each side of the differential. Since the differential is not fixed to the chassis, it has to be braced to the driveshaft. While this set-up is not often used in real cars, it works well for LEGO designs. I used the new wheel hubs, and attached them via a short upper arm, and a long lower arm so the camber would change through the suspension travel.

Moving to the front, I kept the V-8 as in my 4×4 8081, and built the rest of the front around the motor. I used a suspension design similar to 8081, where there are two equal length arms holding the steering pivot. A single shock absorber is used for each side. All told, the car is about two studs lower, due to the new suspension, and the new tires.

It is not much of a redesign, but sometimes I need a project that is not a significant, and allows me to just build something simple.

Happy Building.

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Bedford MWD


I have said it before, but my favorite things to build are Trial Trucks.  The combination of the driveline construction, forces on the truck, diversity of body style, and various propulsion systems offered by LEGO combine for a great building experience.  Because of this, I usually am building a Trial Truck, or have one built at all times.  But for some reason, this truck seemed to sit for a long time unfinished.  I struggle with deciding if a truck will be a model of something, or something fictional.  This decision is often made too late in the construction process.  After toying with a Daimler Scout body, I decided I needed to finish this project and the Bedford MWD body was chosen.

The full gallery may be seen here.

01

After some some experience with various designs, I decided to construct a truck around a simple locking differential idea I had recently designed.  Because I would need an extra IR Receiver for the locking function, I decided a simple two speed gearbox (1:6 and 1:10) could use the other IR channel.  I placed all the controls in the middle of the chassis.  The driveline and the steering axle would run through the middle.  On the left side was the Battery Box and the motor for the gear change, and on the right side was the XL drive motor, the gear box, and the motor for the locking differential mechanism.  The steering motor would hang out the back of the chassis over the rear pendular suspension unit.  Both axle were connected by my favorite linked suspension system.

zbedford

Each axle took a little bit of work.  I selected a simple design for the locking differential.  Basically, it is a 24 tooth differential placed directly next to a 24 tooth gear.  A pair of sliding 12 tooth double bevel gears slide back and forth one stud to connect only with the differential, or with both the differential and the neighboring gear locking out the differential.  After toying with some old flex cable, and some pneumatics, I figured I was making it too complicated.  I added a small pivot with a Small Technic Steering Arm, and connected it to a 9L link.  This way both axles could be connected, the suspension and lock could keep operating unaffected by each other, and it all could be controlled by a mini Linear Actuator.

Initial tests were positive, so I then decided to figure out a body for the design.  I worked for too long on a Daimler Scout body.  I had the structure made, but the paneling was just not happening.  After sitting on the project for 5 months, I decided it was time to make something new.  The Bedford design worked well, and helped my get excited again in the project.

Now, once I got outside to drive the truck a glaring problem occurred.  The bevel connection in each axle that transmits the longitudinal drive forces to transversal drive forces kept slipping.  You can hear it in the video.  Because of this, it did not matter if it had locking differentials, or if it had a two speed gearbox, or if it had working suspension.  Anything could stop it.  I though about reworking the axles, but then, I have been working on this for 11 months, it was time to be done.  I’ll use the locking mechanism again.  That worked great.

Thanks for reading.

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.

The full Gallery may be found here. Instructions may be purchased for $5 USD.  Buy Now Button

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.

Talon Track


Every once and a while I see something so creative I have to build something like it.  I happened with my HH-65.  It happened with my Zil 132.  And to some extent it happened with my Spitfire.  But when I saw the Urban Buggy from Chrismo, I though I have to make something like it.  It was such a fresh and creative design.  It had such great lines, a perfect stance, and a unique driveline setup.  But while imitation and outright plagiarism are the most sincere forms of flattery, I thought something of my own design would be a better contribution to the LEGO community.  I present my Talon Track Car.

You may find the full gallery here, and the instructions here.

I designed this car to be fast and stable, just like a track car.  I started with a drivetrain that would be reliable and effective.  A PF XL for drive, and a PF M for the steering.  I placed the PF M in the front mounted directly on the suspension unit, with a return to center spring in the middle of the mount.  The system is set up differently than in my Rumble Bee, but uses the same return part.  Each suspension arm would have a single shock absorber.  Directly behind the steering motor was the XL for the drive.  It was geared up with a 20z/12z ratio, with the driveshaft connecting directly to the 20z gear that turned the differential.  The rear suspension used an independent setup that was developed a long time ago for my Red Car Bigger (great name, huh).  If it’s not broke, don’t fix it.  The suspension was planted.  I placed the rechargeable battery box and the IR receiver behind the rear axle.

The car was quick, and didn’t have any problems, but faster would have been cool.  The return to center system worked well, especially for the quickness of the car, and the quickness of the steering.  It was easy to control.  The car was robust, and crashed well.  So go ahead and build your own.  Enjoy.

Flat 6


Every once and a while I get picked up by another LEGO blog. I am honored when it happens as it show others value my work. However, it seems to happen when I lease expect it, and in creations I find fun, rather than significant.  Thank you none the less.

Thanks to the Lego Car Blog for posting my Dune Buggy and my Zil 132, and The Brothers Brick for Posting my Rumble Bee.  Spreading thirdwigg is deeply appreciated.

THE LEGO CAR BLOG

This monster dune buggy was unearthed by the Elves on MOCpages. K Wigboldy has included steering, all round independent suspension and, best of all, a huge six cylinder engine hanging out the back.

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Mack Marble 5T


I confess.  I took the bait, and started on the 2012 You Design It, We Build It before the final rules had been confirmed.  I should know better.  After all my schooling, you would think I have a good idea about how to follow directions.  The first direction is, wait for directions.  But, with all LEGO building, I enjoy what I am creating, and so even after the rules and directions have been given, I still want to contribute to the LEGO community.  So, my next MOC is another Trial Truck, built with the intention of being easy to play with, easy to build, and tough enough to handle child play.  All with instructions, so you can build one.

See Instruction Page

I built this model based on what I thought could be improved on set 9398.  While this new set was a great step forward for the LEGO company, I felt there where a couple of changes that should be made to make the model a better off-roader.  Because I was working with the assumption that this would be something LEGO would produce, I gave myself a couple of constraints.  First, the model had to be less than, or equal to, the cost of 9398.  Second, the model had to have improved off-roading skills.  Third, the model had to have easy playablity, so the drivetrain had to be reliable, the battery should be easy removable, and it should be easy to drive.

I started the frame before the axles.  I placed the battery box directly over the driveshaft.  An XL motor was place behind the BB and three 16z gears above the driveshaft.  One 16z gear went up to the fake motor shaft.  The driveshaft would connect front and rear to the two axles through the new ball joints from 8110.

I then built the two axles, starting with the rear.  To keep the speed of the Mack similar to the 9398, I would gear down the XL motor to about 1:4.  The driveshaft came out of the ball joints and connected to the differential.  I chose two 12z/20z gear sets as the final reduction.  This would keep the driveline a little stronger, and help keep various axles from working their way out of the gears, much like the design of the 9398.  The final gearing was 1:3.89.  It’s not a stump puller, but it could still move up most hills.

The front axle was a little more tricky.  Basically, it had a similar setup, with a PF M motor placed on in it to work the steering.  This was by design.  To keep the driveline reliable, and limit the failure of steering, I kept the steering part of the axle, rather then having components placed in the chassis, and then connected via a shaft to the front axle.  The steering is a little quick for my liking, but it works flawlessly.  To understand more about the axles, check out the instructions.

Through a little trial and error, I connected the suspension, and tweaked it so it would function in a way that was robust, and allow for great movement.  I am still not pleased with how it turned out aesthetically  but it functioned without problems, it supported the model well, and allowed for sufficient articulation, so I left it.

I then added a simple body, a basic rear bed, and added some engine components such as exhaust,  intake, and a simple turbocharger behind the fake motor.  When I was done, I noticed the cab looked a little like an old Unimog.  This seems to be a theme with me, as I love the look of the Unimog.  On the other hand, I do not like the look of too many cabover truck designs, as such, many of my trucks have the slight setback cabover design that is very similar to the Unimog.  My T55 is like this, and this is why I have built so many Unimogs.

The model worked well.  the suspension and stability was perfect.  The truck was stable, and did not roll over, all while being able to handle various terrains.  The gearing was sufficient and would be great for a playing child.  It was easy to change out the 12z/20z gears in the portal axles to a 8z/24z setup which made the truck a little more strong.

It would be a great model for many LEGO fans due to cost, reliability  stability, and playability.  So I have posted instructions for people to enjoy the model as well.  I think it would have been a great LEGO set, then the rules were released.

Next time I’ll wait for the rules.  Thanks for reading.

Full gallery is here.

International FTTS


It has been a little quiet in Thirdwiggville for the last month.  I have been working on a project that is taking a lot of time and resources, so my posts have slowed, even though my building has not.  But just wait, it’s going to be awesome.

Last summer I wanted to do another Trial Truck that would utilized some features I have never used before.  I wanted something complicated to see how it would work.  I wanted a model that would use four wheels steering, independent suspension, and have a simple two speed gearbox while being low to the ground.  After spending some time at the Chicago Autoshow, I saw a FTTS concept, so I thought this would be a great vehicle to model for this next truck.

This model would be built around an independent suspension.  After seeing it used so effectively in a truck by ATRX, I wanted to give it a try.  Each of the four wheels would use a simple double a-arm set-up with a wheel mount attached at the outside.  The wheel mount would house the portal axle and connect the steering linkage.  After a couple of different designs, I also decided the wheel mount would also connect the the shock absorbers.  This was a little unorthodox, as most independent designs mount the shock absorbers directly from the frame to the a-arms.  I did this for two reasons.  First, the model would be heavy, and I could not get the support I needed when the shocks were connected to the a-arms.  Second, and most importantly, I noticed too much suspension flex when the shocks were mounted to the a-arms.  The force applied to the wheel would go up the wheel, to the wheel mount, through the pivot, halfway down the lower a-arm to the shock.  LEGO is relatively stiff, but all these steps complied too much flex.  I would not have it.  I mounted the shocks on the wheel mount, and created a simple MacPherson strut set-up.  This worked well, as it allowed for full steering movement, long suspension travel, and adequate support of the truck.

The front and rear suspension axles both had a PF-M motor driving the steering.  Each were on independent PF channels connected to a single 8878 Battery Box to allow for individual steering, crab steering, and to solve steering drift commonly problematic with four wheels steering vehicles.  Both axles were connected with dual drive shafts running the length of the truck.  One drive shaft would then connect through a simple two speed gearbox to the PF-XL motor.  The final gearing was 1:6.2 and 1:10 for the truck.  This gave the truck sufficient top speed, with an effective crawler gear.  The Battery Box used for the drive motor and the gear shift motor was placed directly behind the front suspension, and in front of the drive motor.  This placement was perfect for stability.  It helped give great traction to the front wheels, kept the center of mass low and to the center with a slight forward bias.

I then finalized the model with a simple removable body built on a Technic frame.  While the hood was little high, and the rear body a little too short, it looked pretty close to the rear FTTS.  Fans seems to like the look, as it is still one of my more popular model.  See the full gallery here and the Work in Progress gallery here.

The model was a lot of fun to drive, and due to its squat design, it was very well planted.  The truck did not want to role over.  I think it could have used a little more suspension travel, and having four wheel steering was crucial to give it some maneuverability that was lost due to the suspension design.  The gearbox was flawless.  The truck did have some trouble skipping gears at the portal axle.  It seemed to happen when a single wheel was over-stressed as the driveshaft could have used stronger bracing in each suspension unit.  This placed a lot of strain on the particular wheel.  So would I do the independent suspension again.  Maybe, but it would need some strengthening and redesign.  Maybe it’s time for another truck like this.

Thanks for reading.  Something big is coming.

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.

Freightliner M2


For some reason, I often find myself building two trial trucks at the same time.  While I was building my ZIL 132, I also wanted to try something with floating axles.  The model would use 6 wheels, a 3 speed transmission, and fully suspended live axles.  I also wanted to model the Freightliner M2 Business Class truck as closely as I could.

The model started as my trucks usually do; with the axles.  The second and third axles would be identical, and would be connected with a simple pulley wheel universal joint between the two.  To keep the speed through the universal joints high, and the torque low, I used as 12z/20z gearing after the universal joints, then the knob wheels to rotate the axis, then the normal 8z/24z gearing on the portal axles to finalize the drive.  This also allowed me to keep fewer knob wheels as the second axle had the drive shaft from the transmission pass uninterrupted to the rear wheels.  The final drive ratio for the two rear axles were 1:5.

The front axle was a little more work.  I wanted to have the steering motor mounted on the axle so I would not need to have a steering shaft connect to the front axle.  This proved too difficult, as it would raise the PF XL motor that I was going to use for the drive to high on the truck.  I decided it would be better to mount the steering motor on the frame and connect to the front axle via a CV joint.  Once I made this decision, the front axle became easier.  I used a 1:3 gearing on the portal axles, a knob wheel, and then a drive shaft back to the transmission.  The steering axle would exit just above the drive shaft on the axle to move to the right for the steering motor.

The frame was pretty simple.  Once I had the transmission placed, and the axles spaced, it was simple to place the suspension components, and the shock absorbers.  Each axle had two steering links mounted vertically which connected to a 3×5 liftarm which would activate a shock absorber; very much like Lyyar’s design.  Each axle had a steering arm to keep the axle from swaying laterally.  Finally, all three axles had a number of 9L links to keep the various movements maintained.

The transmission was going to be placed behind the PF XL motor which was under the hood.  The changeover mechanissm would be placed in the center of the truck with the changeover motors mounted longitudinally, on both sides of the truck.  The PF XL motor was place directly above the first axle, and was mounted on a moving frame that was moved by the changeover.  This allowed a moving frame to work its way through the three gears.  The ratios were 1.25:1, 1:1.25, and 1:2.  This allowed for final ratios of 1:4, 1:6.25, and 1:10, which was more than capable for most terrain.  The drive and steering Battery Box was mounted over the second and third axles, and the gearbox 8878 battery box was just behind the changeover in a little box on the bed of the truck.

Finally, like always, a simple body was mounted.  I had a little trouble getting the look I wanted on the front of the hood, as the suspension components kept getting in the way.  I added a bed, covered the changeover and motors, and a couple more details and everything was finished.

The model was not my best driving truck, as six axles do not want to always work together.  The suspensions was supple, and I was getting no drive or steering input on the suspension.  The truck worked well over various terrain, but struggled on some on step obstacles.  The transmission mounting worked well at changing gears, but gears did not have a strong support, and I found they liked to skip at times.  I liked how the suspension worked, but I do not think it brought enough of a valued to use this system again.  It had moderate improvement on dealing with terrain, but it placed a lot of stress on a number of parts, such as the frame, the axles, the driveshafts, and the universal joints.  The next truck will use a pendular set up again.

The full gallery may be found here.

Power Functions 4×4 8081


For most LEGO enthusists, when they purchased the set 8081, they quickly modified the set with a Power Functions drivetrain.  It makes sense.  LEGO models are a little more exciting when they are motorized.  But I guess I went a little backwards.  I wanted to do the fun stuff first, and make the most complicated and compact drivetrain I could make.  I posted the instructions here, and they can also be viewed on Rebrickable.com.

But the comments kept coming from people who wanted to see my model motorized.  So I thought it might be a fun addition.  I added a two PF M motors, a 8878 Battary Box, and an IR receiver.  I tried to keep the modifications simple, so I could easily add the motors to the MOD, and take the system out if I wanted to.  The drive motor was placed on a simple mount that connected to the frame.  The power was fed thought a 8z gear to a 24z gear which then connected directly to the V8 driveshaft.  The driveline was unchanged from the V8 down.  The steering motor was mounted laterally in front of the rear seats.  A 20z double bevel gear drove a 16z gear, then a worm gear moved the final 8z gear which was mounted on the existing HOG steering axle.  I removed the passanger seat which is where I placed the battary box, and created a simple mount for the IR receiver.  The added weight required a new shock absorber, so I added that as well.

The model worked alright.  The drivetrain did well to handle the new power, and I could easily control the Crusier.  The steering motor was a little too powerful for the upside down facing steering rack.  It skipped a little under load, which was a problem over rougher terrain.  The drive motor was a little taxed, so a PF XL would have done a little better.  I guess I could add that, but I am ready to move on to my next model.  Stay tuned.

The full gallery may be found here.