9398-B Alternate Model (4x4 Offroad Cab-Over Truck)

[DLuders]

I just built the Lego Technic 9398 4x4 Crawler's alternate "B-Model" -- the 4x4 Offroad Truck (with its tall cab-over-motor design). Using the downloadable PDF Building Instructions available from Technic.Lego.com, it took me around 4-1/2 hours to assemble the B-Model from start-to-finish (the same time that the A-Model took). From the 21 pictures I placed on my Flickr photoset, you can see from side-by-side comparisons that the B-Model is much taller, and has a different center-of-gravity balance point than the A-Model. The 9398-B has more extra parts (and hence is slightly lighter than the A-Model), but it is nose-heavy:

The two smokestacks and Power Functions Receiver will break off in a rollover crash (the kind that Sariel likes! ), since there is minimal protection. Once a rollover begins, the A-Model continues to roll over easier than the B-Model due to its more-rounded shape, and is much more robust (i.e., no parts break off).

The cab-over-engine design is more typical of European truck designs than American designs. I did not apply the stickers to the A-Model, and the B-Model's building instructions does not come with suggested sticker placement:

Overall, the "building experience" of the 9398-B Model's assembly was enjoyable. The first two-thirds of the build was identical with the A-Model's build, since the chassis is the same in both variants. They CRAWL the same but the B-Model's weight-forward design and top-heavy body shell makes it more prone to tipping over.

Modifying the 9398's body shell is easy; efferman already made an alternate "C-Model". You can design your own body shell using P4trickvH's 9398-B Model Lego Digital Designer (LDD) .lxf file. Although some parts are not included because they don't exist in LDD, you can easily see what is possible.

Edited July 29, 2012 by DLuders

[sama]

Very nice! I think the b-model should perform better than the a-model because it is lighter (by a few grams). But then again, the model is not very balanced. There are more pieces on the front than the rear (the cab).

[Traktor]

I would think that the extra weight gives better traction, so that it would not really matter, except if power is a big issue. For example a heavy truck would theoretically break (slow down) just as good as a car as long as both of them have breaks that allows the wheels to lock completely and they had the same friction to he surface. But of course there are many other factors in reality. But you get my point?

Edited July 28, 2012 by Traktor

[Paul Boratko]

Pretty cool.. This is the first time that I have actually got to see the B-Model built next to something...

[Traktor]

I do not really get if you are saying that it is the B or A-modell that is most likely to roll over? It seems like you are saying both...

Edited July 28, 2012 by Traktor

[DLuders]

The 9398-B model is more likely to roll over because:

1) It has a higher center-of-gravity.

2) It has a nose-heavy design, not centered on its four wheels like the 9398-A model.

I hope to prepare a YouTube video tomorrow to show these characteristics. Side-by-side comparison will show how the A-Model is the superior design.

[SheepEater]

I think it's ugly.

[timslegos]

The b-model doesn't actually look that bad.

tim

[Phoxtane]

I'm kind of torn. It looks nice from the front, but it looks pretty bad from the back, and IMO it raises the CoG too high for effective performance.

[rm8]

The first foto looks like render, cool, good contrast, color and background

I like THE B.

About heavy front: is it possible to move BB a little bit back to balance heavy front with BB MOVED BACK?

[Traktor]

The 9398-B model is more likely to roll over because:

1) It has a higher center-of-gravity.

2) It has a nose-heavy design, not centered on its four wheels like the 9398-A model.

I hope to prepare a YouTube video tomorrow to show these characteristics. Side-by-side comparison will show how the A-Model is the superior design.

I knew that already, but in the "review" you were saying this:

"The two smokestacks and Power Functions Receiver will break off in a rollover crash (the kind that Sariel likes! ), since there is minimal protection. The A-Model rolls over easier than the B-Model and is much more robust that way"

[DLuders]

I should have said that, if you want the 9398-A model to CONTINUE ROLLING downhill, the A-model's rounder body will allow it to roll. The more-boxy 9398-B model will START TO ROLLOVER easier than the A-model, but will quickly stop rolling due to its shape.

[dr_spock]

I think I like the look of B over A -- like a Dakar Rally truck. Would using the bigger Power Puller wheels and tires help with the center of gravity?

[DLuders]

Yes, using the heavy Lego Power Puller wheel/tire combination would lower the Center of Gravity, and help resist sideways rollovers. I hope to shop all of this later today in my YouTube video....

[jadedomg]

I like the look of the B model, I just wonder if moving the battery box would of helped offset the heavier front?

[Alasdair Ryan]

I like the look of the B model, I just wonder if moving the battery box would of helped offset the heavier front?

Or you could add some train weight's.

[Aussie BJ]

My ignorance didn't even realised there was a B model for this set. Looks pretty good and BIG. Thanks for posting it DLuders.

Now I really can't wait till this set hits the Aussie SALE market. Bring on the Xmas Sales!

[DLuders]

My son and I just made

. See the Lego Technic 9398 alternate B-Model in action against the A-Model. We tested:

1) The difference in performance between using 1.5V alkaline batteries and 1.2V rechargeable batteries,

2) The susceptibilty of the stock B-Model to rollover crashes, compared to the A-model's lower center-of-gravity,

3) The effect of swapping Lego tires to help resist rollovers. We tested the stock Lego 54120 balloon tires against the Lego Unimog's 92912 tire and the Lego "Power Puller" 32298 Tire.

No permanent damage was done to the two models shown in the rollover carnage!

[Edwin Korstanje]

My son and I just made

. See the Lego Technic 9398 alternate B-Model in action against the A-Model. We tested:

What a good video your made from the A and B model

[DLuders]

Yeah -- I didn't drive my 9398 into the water like Conchas did with his!

[subcaptian]

If the B model is nose heavy, then why do the European heavy duty truck mfgs make them like that? There must be some advantage.

[rm8]

My son and I just made

. See the Lego Technic 9398 alternate B-Model in action against the A-Model. We tested:

1) The difference in performance between using 1.5V alkaline batteries and 1.2V rechargeable batteries,

2) The susceptibilty of the stock B-Model to rollover crashes, compared to the A-model's lower center-of-gravity,

3) The effect of swapping Lego tires to help resist rollovers. We tested the stock Lego 54120 balloon tires against the Lego Unimog's 92912 tire and the Lego "Power Puller" 32298 Tire.

No permanent damage was done to the two models shown in the rollover carnage!

Nice testing polygon at 4:45. When i'll receive my 9398, I'll also made a polygon with wooden sticks, bricks, cuttings and nails. I found that sand can be simulated by sawdust - they are not so dangerous for plastic details...

3:20 - quarter mile race?!

You and Conchas are real crush-test maniacs:)

Edited July 30, 2012 by rm8

[Zerobricks]

That sure is some heavy duty, almost scientific-like testing! Power puller wheels sure seem to make the model stable!

[daniele]

Great video!

[DLuders]

If the B model is nose heavy, then why do the European heavy duty truck mfgs make them like that? There must be some advantage.

Their advantage is "minimal space" taken up on the narrow, congested roads in Europe. I lived in Berlin, Germany for 3 years and know that all of the American vehicles there looked ABSOLUTELY RIDICULOUS and out-of-place, due to their large size. American semi trucks (operating in the wide-open spaces) have a "longnose" design to allow for easier access to the engine compartment, and to allow for better "crumple zone" crash protection in the event of a front-end collision.