CAT 573C Feller

June 10, 2013 Leave a comment


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.

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.

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Mini Feller

November 18, 2012 6 Comments


Building with Lego is a continuous formation of compromise.  While my ideal of what my Mini Feller would include was significant, what I could actually accomplish was a compromise of space, function, realism, and frankly the amount of frustration I was willing to tolerate.  So while the final result is a watered down version of what I would have liked, it was the result of me compromising amidst the situation.

Instructions can be found here.

I wanted to make a small model go with my Mini Skidder.  The MOC had to be the same scale, have a decent level of fuctions, and work with my Skidder.  A feller seemed like a good option.  As I looked at what function this MOC would have, I ambitiously stated it must have a working blade, working steering, working grapper, and a working tilt function.  All these functions would be controllable on the back or on top of the cab.

The steering was simple enough.  I added a small turntable at the bottom of the chassis to give the frame some support.  The HOG steering axle would come out at the top of the cab, and join the front and the rear with a small link arm.  Simple enough.  Likewise, I added a differential in the rear part of the chassis, geared up the rotation, sent it though a couple of universal joints to the front of the Feller, connected it through a pair of 12z bevel gears, and attached a saw blade.  Again, simple enough I had steering and a working blade.

It got complicated as I tried to add the arm features.  The lifting of the arm would be done with a 8z gear with a worm gear.  Because there was a driveshaft to the front blade, the 8z gear needed to be placed on the axis of the arm, but out of the way of the driveshaft.  The required a 1 stud offset that also needed to be directed back through the steering axis to the rear of the Feller.  I used a CV joint to allow the axle to slip as the feller would steer.

The tilt feature would require a parallel control that would allow the elevation happen while keeping the feller blade parallel to the ground.  This would require another 8z worm gear connection at the lower rear pivot point of the arms.  I was running out of space.  Of the 7 studs to work with, one was used for the universal joint, one was used for the lifting gear, one for the mounting liftarm, and one for the lifting arm.  I could not add another worm gear system, while being able to actually lift the feller blade.  Additionally, adding a link for the gathering arms would also have to work through this pivot point if I wanted to isolate the movement from the lifting and tilting feature.  I had to give.  A compromise was necessary.  I felt the stability of the feller blade had to be paramount, so I added another support arm.  I also felt gathering arms must remain as they are essential to a feller.  Sorry, but the tilt feature got the ax.  It was the correct decision, but it still tasted a little sour.

It was a great little MOC, and I had a good time creating it.  I hope you enjoy building your own.  The full gallery can be viewed here and the instructions can be viewed here.

Thanks for reading.

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Mack Marble 5T

October 23, 2012 Leave a comment


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.

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International FTTS

July 30, 2012 Leave a comment


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.

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CAT D5K

July 1, 2012 Leave a comment


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.

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Zil 132

May 4, 2012 3 Comments


A couple of months ago I was struck by a new design by Waler.  It was refreshing to see a well made Trial Truck based on something a little different.  I wanted to make a model of my own.  Thanks to him for the inspiration, and for the great ideas on the cab and the fenders.

From the beginning I knew this truck was not going to be a serious off road contender, but I wanted to redesign the whole drivetrain.  I decided to go with a pendular suspension for the first and second axle and a trailing live axle for the third axle.  All three axles would have a differential and a a set of portal axles.  The first and the third axle would also have steering linked together.  As is often the case with my trucks, I had the pendular axles held by a turntable with the steering function passed through the turntable by use of a differential.  The second axle was held by a turntable in the front, and the steering differential passed through to provide steering to the final axle.  The drive function powered all three axles and would connect to the transmission and motor in between the first and second axle.

The third axle was a suspended live axle that had a trailing setup created with the new 8110 pieces.  This would allow for rotational and vertical articulation while connecting the drive shaft and giving space to the steering function above.  The steering shaft would allow for movement via a CV joint.  The Power Functions M steering motor was placed in the rear, and used a simple 1:9 reduction.

A Power Functions XL was used for the drive funtion and was placed between the front two seats.  The motor was mounted on a sliding assembly for the gearbox function, much like the design pioneered by ATRX.  I used my three speed changeover design to move the motor through three gears, for a final ration of 1:7.5, 1:4.7, and 1:3.  The gearshift worked perfectly.  While the drivetrain was a little complicated, the gearing was rather simple.  The battery boxes were place above the second axle side by side.  This kept the weight centered, and as low as I could get it.

Finally I added a cabin and a cargo area.  The cabin was straight from Waler’s design, as was much of the fender area.  I used technic panels to create the cargo area, which also gave me a space to place the two IR receivers.  This also hid the two battery boxes, and the wiring, and generally cleaned up the truck.  I created two small doors in the top to assist with picking up the ZIL.  I was done.

Over mostly level ground the ZIL was one of my better designs.  The differentials and steering worked flawlessly to make the ZIL drive easily.  The gearbox worked well and eased the drivetrain over slight irregularities.  But once the  pavement turned to dirt the ZIL struggled a little more.  It was not designed to have too much suspension travel, and this showed.  It struggled on some of the bigger bumps, as the tires would scrape the wheel-wells.  Overall, I was pleased with the design, and was happy with the way it turned out.  It looked great, it was fun to build, and it was a blast to drive.

The full gallery can be viewed here.  Also, a big thank you to The Lego Car Blog for posting this model on their blog.

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Mercedes Benz Axor Refuse

May 1, 2012 1 Comment


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.

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JCB 930 Forklift

April 29, 2012 Leave a comment


It was time for me to to make something that was a little smaller with a lot of functions.  I kept driving by a JCB forklift on the way to work, and I thought I could make that.  I wanted manual functions, including a working fork tilt and dual stage lift, working steering and drive, and a yellow bodywork.

I always start with the hardest part of a model.  For this model, that was the fork.  I wanted to use a dual stage lift as to get the forks to a substantial height.  This design would require a chain that would wrap over a moving frame, and connect on one side to the forks, and on the other side to the body.  The moving frame would be moved by a screw, thereby lifting the forks.  I used a number of worm gears on two 12l axles, connected through the bottom to move the moving frame.  This setup allowed for a pivot point, and a lifting mecanism that would function much like the real JCB 930.  The moving frame consisted of two rows of liftarms, and the forks tied everything together between the moving frame and the worm gears.  A chain went up and over the full assembly to work move the forks as the moving frame was lifted.  It works like this.

I then worked on the driveline.  I added a 3 cylinder motor in the rear, driven by the front wheels, working to keep the functions out of the way of the fork mechanism.  I added a steering axle on the rear, and gave it a pendular suspension setup.  This allowed for some stability on uneven ground, while keeping the front wheels planted for the load as it had no suspension.

I then built the body after the JCB 930, and as I did, I added a tilt freature to the fork.  This feature did not work too well, but it gave me the ability to adjust the pitch of the forks, which we a design requirement.  It was not too stable.  After a little work to the body, and a HOG steering link out the top of the cab, the model was done.

The model worked well, particularly the lift feature.  I was a little disappointed with the tilt feature, as it was a little too wobbly. The drivetrain worked well, and the steering allowed for tight corners.  The suspension give good stability, and offered a little bit of off-road prowess.

The full gallery is here.

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Kenworth T55

April 28, 2012 6 Comments


Traction.  It’s all about traction when designing a trial truck.  Because of this, many builders have tried a number of different solutions in designing their own trucks: differentials, gearboxes, various numbers of wheels, various gears ratios, countless suspension designs, and on and on.  So why would it be any different for my trucks?  Every truck I make is a reaction to some set of problems I have encountered with a previous truck.  This is my current solution.

The full gallery is here.

The Kenworth T55 started as a proof of concept, and turned into a design of a fictional truck.  I wanted to somehow see if there was a way to use differentials in a successful trial truck.  For this to work, two things had to be accomplished.  First, there had to be a way to keep the tires from spinning uncontrollably when they lost contact with the ground.  And second, the torque going through the differential had to be low enough that it would not shred the gears inside the differential when the truck encountered an obstacle.   Could I make axles that had a limited slip differential while having all of the gear reduction at the hub?

Enter turntables.  I have seen some ideas before, most sigificantly from Borec, including this truck, so I went to work.  I designed a mount for the wheels and tires, and placed the universal joint as close the wheels as I could.  Then I used a limited slip differentail design, and sent the driveshaft back to the body.  A simple steering design was used, and the two fuctions passed through the common design of using a differental body through a turntable.

The chassis was designed to keep the weight low, both is mass and location.  As is common, I used the Power Functions XL motor for drive, and I decided to use the 8878 Battery box as it was significally lighter than the other design.  In addition, I would have a drive shaft and a steering shaft running the length of the truck, so the motor and power pack needed to set on both sided of the truck.  Also, because I used the turntables, the drive shaft was very high.  This gave great ground clearance, but I needed to keep the heavy components low.  By having both large components on the side, I was able to keep a short wheelbase of 30 studs, and keep the mass centered and low.  The driveline was complete.

Ever since my GMC 2500, I have held to the belief that a linked suspension is the most efective setup for four wheel trial trucks.  The design keeps all four wheels firmly planned, and does not have the wobbling feel of many pendular suspension designs.  But as is often the case, I ran out of room to place a link rod between the two wheels so I opted with useing the rubber connectors to keep the axles level.    I added a body, and a steering motor, wired everything together, and I was done.

So how did it work.  As you can see in the video, the suspension was effected by the steering and drive shafts.  This further confirms my thoughts on the linked suspension.  Second, the turntables did not really add much.  They added a lot of friction to the driveline, and though they kept the differentials safe because of the tall final gear they did not really isolate the forces on the differential as much as I would have liked.  Third, the limited slip differentials worked well, but still allowed for too much wheel slip.  I ended up replacing the rear with a locked axle, which seemed to work well.  So, for the next truck, bring back the linked suspension, and find a better differential solution.  Maybe then I can find some more traction.

 

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