[MOC REVIEW] Kenworth W900 by Jurgen Krooshoop

[Blakbird]

I had the pleasure of being one of the test builders of Jurgen Krooshoop's new Kenworth W900 truck. What follows are my impressions of the build and the completed model. Note that I used a pre-release version of the instructions, so any issues that may have been found have since been fixed.

As you can see, this is a big model and like any big model it uses a lot of parts. Beyond that though, there were a couple of parts which were quite difficult to procure. Neither white, green, or orange are particularly common in Technic. On the one hand, this makes the model very disctinctive. On the other hand, it makes part acquisition a challenge! The worst were the 3L green liftarms on the hood. These have only come in one EV3 expansion set and there was only one seller in the world and they only had two of them. Luckily I was able to use 3L thin liftarms instead, a change which Jurgen later incorporated in the instructions. The white flex axles on the roof were also challenging to find (only available in Williams Racer), and the trans clear jumper plates on the headlights technically don't exist at all according to Bricklink, but I was still able to buy some! 11L orange liftarms are also a challenge. Some of the other orange and green parts are uncommon, but not exactly rare. If you want to avoid some of these challenges, Jurgen has created another version which uses more readily available colors and parts. Functionality is the same.

Some statistics:

• Parts: 2594
• Gears: 98
• Pins: 757 (various styles)
• 3 PF M motors
• 2 PF XL motors
• 2 PF IR Receivers
• 3 sets PF LED lights (3 sets of lights are shown in the instructions, but many more lights were used in Jurgen's personal model in his photos)

Let's start building! this first image shows the rather tremendous pile of parts. This is among the greatest proportion of liftarms I have ever seen for a model. The number of panels is relatively small, as is the amount of wiring considering the size of the model. You can see a big pile of 5x7 frames which are critical for rigidity.

Here the chassis is nearly completed. The dual rear axles are both driven with differentials, and also suspended. The suspension uses soft shock absorbers as well as rubber 1x2 liftarms. You can see the detailed V-6 up front. Drive is handled by twin XL motors convincingly disguised as fuel tanks. The frame is nearly all black which I think looks very good. Typically, large Technic trucks like this tend to have rather twisty frames just due to the limitations of liftarm construction, but this particular model is uncommonly rigid. In fact, I think it is the sturdiest Technic truck I have ever built. At the point the wiring is a bit of a mess, but the instructions due a good job of showing all the wiring which is well thought out. There is no problem stowing it all.

The real jewel of this model is the transmission, shown in the following 3 images. The first shows the lateral differentials. Each of these is positioned over a red driving ring which can be seen from the bottom in the next image. Unlike a normal LEGO transmission in which the driving rings are in parallel, these are in series. The input side of the transmission uses double gears in parallel for extra strength. In a normal LEGO transmission the driving rings are driven by the motor (or wheels) and then the clutch gears are output. This XMSN is the opposite. The clutch gears of the first stage are driven at different ratios and then the central driving ring axle is the output to the second stage. In the second stage, the driving ring axle is input and the clutch gears are output. Another difference here is that normally in a XMSN only one driving ring is engaged at a time. In this XMSN you must have both engaged. This gives 4 possible permutations resulting in a series transmission with 4 gears + neutral.

     

This render helps show how 2 motors can be used to engage the different gears. You might think that one motor just controls each driving ring, but that's not right. Each motor actually controls BOTH driving rings. This means one motor can be used to select 1st and 2nd gear, and the other motor can be used to select 3rd and 4th gear. The result is that the two sticks on your remote command discrete gears at discrete positions. This means your remote is like a real gear shifter! Move to the upper right quadrant and you get 3rd gear every time, no matter which gear you started in. How is the accomplished? The M motor in the foreground of the image drives the axle under it which has a pair of worm gears. These worm gears drive transverse axles that feed the left side of the differentials. The right side of the differentials is locked because the other motor isn't turning (and worm gears don't backdrive). This forces the ring gear of the diff to rotate. The ring gear shifts the driving rings. But wait, there's more! The aft of the two worm gears just moves with the motor. That means when you move the motor forward, it shifts forward and when you move the motor in reverse, it shifts backward. But the forward worm gear is different. It can slide along the axle and engage two different 8 tooth gears which rotate opposite directions. This means that the forward worm gear ALWAYS shifts forward no matter which way you run the motor! In this way the left hand motor always selects a single position of the 1st stage but can change positions of the second stage. The right hand motor always selects a single position of the 2nd stage but can change positions of the 1st stage. Viola! Any gear can be selected directly! You might think all this complexity comes at the cost of durability (I admit I suspected it), but you would be wrong. This XMSN drove the truck around all day and worked flawlessly. The XMSN alone is a good enough reason to build this model.

But wait, it turns out this model is not just a chassis and a transmission. Here are some pictures of the completed model. You can see the detailed engine and interior. You can see the lovely sculpted hood, body, and sleeper. Steering is controlled by an M-motor through a white clutch. You might think a servo would be better, but I actually found it quite controllable with the "bang bang" remote. The front axle is also suspended, by the way. i should also mention that the battery box is quite easy to change. The whole back panel of the sleeper pops off and the battery is attached to it. There is even a clever switch to allow you to turn it on and off from the outside (visible above the spare tire).

     

 

     

 

     

Beyond a doubt this is one of my favorite trucks. Besides looking great, it is as technical functional and durable as you could hope for. I highly recommend it.

Instructions are available at Jurgen's Technic Corner. Bigger versions of all pictures at Bricksafe.

[grum64]

Excellent review of Jurgens excellent model.

Thank you Blakbird

[IJsmuts]

Very nice truck and review Blakbird, thanks! And great work again on BI! You must be realy busy lately! Now the only thing you need to do is update the show your collection topic with a photoa of your recent built MOCs ;)

[jantjeuh]

Nice review, the DELUXE edition of this is on my to-build list. Already got all the parts!

[Rishab N]

Great review I think this is one of Jurgen's best models

[Blakbird]

Very nice truck and review Blakbird, thanks! And great work again on BI! You must be realy busy lately!

I did not make the instructions for this model. This is entirely Jurgen's work.

[legoman666]

Any chance of getting a video of it in action showing the gears shifting?

[SilenWin]

Any chance of getting a video of it in action showing the gears shifting?

Here it is -

[phoenixtroy]

Is it compatible/appropriate to 2lego's trailers and designer han's lowloader? Is it possible to get a photo of it attached to those trailers and next to 2lego's trucks?

[SilenWin]

Is it compatible/appropriate to 2lego's trailers and designer han's lowloader? Is it possible to get a photo of it attached to those trailers and next to 2lego's trucks?

I think it's possible to attach these trailers, but you should change the 5th wheel's construction. Easier way is to create your own trailer, based on ideas of 2lego and Designer Han.

It took me an hour to make a trailer for Jurgen's truck. I never built anything like this before, and I liked the result =)

[phoenixtroy]

I think it's possible to attach these trailers, but you should change the 5th wheel's construction. Easier way is to create your own trailer, based on ideas of 2lego and Designer Han.

It took me an hour to make a trailer for Jurgen's truck. I never built anything like this before, and I liked the result =)

I already have those mentioned trailers constructed and was more concerned if the sizing of this truck connected to those trailers looked appropriate.

[SilenWin]

I already have those mentioned trailers constructed and was more concerned if the sizing of this truck connected to those trailers looked appropriate.

Look, truck itself is 21 studs wide and the 5th wheel's height is 10 studs. So if the trailer dimensions is approximately the same - truck and trailer will look great together.

[me00rjb]

Great model and review, definitely one to add to the list of things to build! Any chance of a quick CAD picture to see how it would look with the orange parts changed to lime? The only part that doesn't seem to be available in lime is the 'Axle and Pin Connector Perpendicular Double Split', but I'm sure a work around could be found...

[jantjeuh]

You want to combine green and lime?

[me00rjb]

Yep

Well, maybe... hence the request for the picture!

[jantjeuh]

Why not orange? Price of orange parts has gone down a lot recently on BL.