Iveco XTR


After a couple of more complex projects it is nice to take a break to do two simpler projects. When I need a little bit of a design rest, I do a trial truck, and usually a fictional one, so I can build as I please.

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

Iveco XTR

After building a number of trial trucks, I have found some features I like to have on my trucks. Note, these features may be prioritized differently if I was participating in a Truck Trial race. These features I like are linked suspension, PF XL motor for drive, tall clearance, and a center mounted battery box. As I was making this truck for my own pleasure, I forced myself to include all of these features.

I usually start a truck with the axles, and the Iveco was no different. I created the axle with a portal axle build around my favorite piece for both the front and the rear. I also added the space to fit both a differential, or knob wheels for the final drive (though the pictures only show the latter). This would allow me to switch the traction of the truck, and allow for a minor gearing change. While the changeover takes a little bit of time, it’s a nice feature and the gives the truck some versatility. I placed the steering motor directly on the front axle with allowed the middle of the truck to be simplified vastly. In the center of the truck is the battery box mounted longitudinally, and a Power Functions XL motor in the rear. This keeps the heaviest components of the truck in the center and low.

The linked suspension is a setup developed by other that connect two pendualar axles together. Each left side has a linkage that connects the two left wheels together, and the right wheels have the same. This keeps the wheels planted as the pressure from the terrain is balanced across all four wheels. When one wheel has to go up to follow the terrain, the rest of the wheels adjust. It is simple, effective, and keeps the truck a little more planted than a suspension utilizing shock absorbers. Otherwise the truck bounces a little during an obstical.

As you can see in the video, the battery box is getting a little tired, and the snow as a little mushy, but the setup worked well. The truck stayed planted, and it was nice to have two final axle options. It is a simple design that does not require too many hard to find parts, so if you need a good little afternoon project, give the Iveco XTR a build, and tell me what you think.

OK, off to some more complicated builds. Check The Queue. There is some fun stuff coming. Until then, happy building.

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.

Zil 132


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.

Kenworth T55


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. Instructions are 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.

GMC 2500


This trial truck vehicle was my first modern truck.  It was the first time I used a number of verious developments in the new truck, including studless frame and body, functional portal axles, power functions, and the new 94.8 tires.  I built this truck with function in mind first.  Because of this the truck ended up looking like a GMC HD, rather than being designed after it.

I started the build with the axles, and then filled in the driveline.  I place the battery box behind the rear axle to keep the majority of the weight low and in the rear.  I linked the front and rear axles so the suspension would work together to add to the stability of the truck.  This also keeps the truck from tipping as an independent setup would have.  Gearing was 5:1, with 3:1 portal axles.  The truck was powerful, light, stable, and quick enough.

With so much focus on the stability, the truck could have used a little more traction.

All pictures can be found here.

Follow

Get every new post delivered to your Inbox.