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Posted (edited)

Hello,

My latest model is the Panzerkampfwagen. I Ausführung B, a German Light Tank developed during the inter-war period.

Building Instructions are available to purchase over on Rebrickable: https://rebrickable.com/mocs/MOC-119345/Tarix819/pzkpfw-i-ausf-b-light-tank/#details

goNxsbr.jpeg

 

HISTORY

The Pz. I was the first widely successful tank to enter service in the German Army. The Ausf. B model, the successor to the Pz.Kpfw. I Ausf. A, featured a number of upgrades including a new water-cooled Maybach six-cylinder engine, which required the hull to be lengthened to accommodate it. The crew count remained two men (Driver and Commander).

MODEL FEATURES

-A custom brick-build sprocket design inspired by the work of @Milan

-Weight: 5.2kg.
-Scale: 1:8.
-Full drive, each track driven by two PF-XL motors.
-Twin PF battery boxes for powerplant, the model is controlled using two SBricks.
-Working and historically accurate suspension - the frontmost roadwheels are suspended on pivoting arms which connect to a coil-spring, whilst the remaining road wheels are paired together on four bogies suspended using leaf-springs.
-Working headlamp.
-Functional track tensioners.
-360-degree rotating turret.
-Elevation and depression of the main guns inside the turret.
-Accurate detailing, including sledgehammer, storage box, exhaust, aerial and vision slits.

BUILDING THE MODEL

I chose to build the Pz. I because it was a relatively simple, straightforward design; there was no heavy firing mechanism or bridge deployment mechanism, basically just a chassis with a rotating turret and moving guns. The real aim behind it was to test out the new sprocket designs, and to see how they would run on a tracked vehicle weighing above 5kg. In the end I was very pleased with the performance of the sprockets and I will likely be using them on future models. As I will explain, they are an enormous upgrade to the rubber tyre system that I was previously using to engage the tracks. Otherwise, the tank is sturdy and looks good, although the suspension is somewhat fragile. I am very happy with its overall performance and I hope that fans of early German inter-war and WWII tanks will be pleased to see it.

SPROCKETS

As you may already know, my specialty here is large-scale tanks and tracked vehicles, weighing in the range of 4kg upwards.
Building at such a large scale allows me to incorporate a great amount of detail and functionality into my models, however this requires me to use custom Lego tracks built from axles and lift-arms instead of the conventional Lego-produced caterpillar tracks, which are limited by their width and sprocket size.
I have been using these types of tracks for about four years now, however since there was no specific sprocket design available for them, and certainly not at the required sizes (10st/12st/14st diameter), I have instead used Lego wheels with rubber tyres as the driving wheels, since, at least for lighter models, the friction between the tyre and the track is enough engage the track and drive the model along.
In April 2020, I built my A34 Comet tank model, the weight of which was roughly 5.9kg. It was driven by two PF-XL motors connected to tyres at the rear, but had some trouble steering and reversing as the tyres were slipping on the tracks. The solution to this problem was provide front and rear drive, increasing the number of PF-XL motors to four.
I first used this setup in my Vickers Mk. E model in August 2020, and the slipping problem was fixed; it worked very well on that particular model. But since then I have built a variety of other vehicles of different weights and sizes, using the same setup, and a number of problems have come up:

1) Weight Distribution
-My most recent model, the AMR 33, was particularly rear-heavy as motors had to be installed at the back (in addition to the front), where the turret was.

2) Historical Accuracy
-There was excessive bulk on my Matilda I model caused by the front wheels requiring a drivetrain connected to motors. The front lower glacis on that model is too far forward to make room for the drivetrain. This was not necessary on the real-life vehicle, which simply had idlers. It was a similar case for the rear idlers on my Vickers Light Commercial tanks models.

3) Track Tensioning
-Having track tensioners means the motor, direct drive connection and the wheel itself all need to be movable, which adds unnecessary complication.

4) Heavy Vehicles
-Even with both wheels driven, heavier vehicles will still suffer slipping between the wheels and the track, especially on rougher terrain. My Bridge Carrier model weighed between 7.7kg and 9.4kg, was powered by six PF-XL motors and suffered from this a lot. Moreover it could not actually drive onto its own bridge because the wheels kept slipping and the tracks would come off.

5) Steering
-Tracks of course would not always be locked in properly by the rubber tyres. This wasn’t a problem on most of my models, but I remember my T.13B3 and Vickers M1937 occasionally threw their tracks when making tight corners.
 

The solution to these problems was to develop a sprocket that would engage with the custom track properly. And here they are:

https://imgur.com/a/q71kRuh

(I will try to make some building instructions for these)

I had not yet come up with a design due to the complicated geometry of custom-built wheels, and the difficulty in building with Lego elements accurate to the millimeter, however with some inspiration from Milan’s excellent Brick-built wheels book, I have designed two sizes (12st and 10st diameter) of custom sprocket that work smoothly with the custom track. Everything is built from 100% genuine Lego elements, no illegal connections or 3D printing is required.

The first that I built was the 12st diameter sprocket. This uses 1x2 plate hinges arranged in a decagon, which is held taught by rubber connectors fitted in the center. Each tooth is built using two Bionicle pieces. In between each tooth there is a rubber connector which helps keep the track round as it traverses the sprocket.

The principles of the 10st diameter sprocket are the same, however the hinges are arranged in a nonagon, and each tooth is made using one Bionicle piece and a 1x2 flat lift-arm. There are only four teeth on this sprocket, meaning there is a gap of two on one side. This has no effect on the sprockets performance so long as a gap is left every link on the track rather than every two links. It is this size of sprocket that my model of the Pz.Kpfw. I Ausf. B uses.

 These sprockets certainly have great potential and I am confident it is possible to construct them from at least 8st diameter and upwards. With the correct arrangement/modification they should also be able to fit any width of track of at least 5st, and any arrangement of track teeth (Either one row in the center or a row on each side). This will be extremely important for my future models as historically tanks have had sprockets of a great variety of different sizes.

 

IMAGE GALLERY

More images can be found over on Imgur, I shall put some up on my Flickr shortly, too.

https://imgur.com/gallery/jyhtIhN

Edited by Tarix819

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Posted (edited)

Deservedly so too, first impressions looks fantastic and the more I read the more I like it. Superb build, very impressed, thanks for taking the time to do a write up.

That sprocket and tread design are particularly interesting, might have to check out the instructions, when they are done.

Edited by Johnny1360

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I would really like if Lego released such a great custom chain/ sprocket design. To me it would feel more Lego than their standard track / sprocket design made from "special" pieces and just look great :)

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On 8/1/2022 at 9:36 PM, Johnny1360 said:

Deservedly so too, first impressions looks fantastic and the more I read the more I like it. Superb build, very impressed, thanks for taking the time to do a write up.

That sprocket and tread design are particularly interesting, might have to check out the instructions, when they are done.

Thank you! I am hoping to get them done in the coming few weeks.

2 hours ago, LEGODrongo01 said:

This is beyond outstanding. 

Thank you! I am glad you like it.

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19 hours ago, 1Ruben said:

Incredible work! The amount of details is insane

 

 

10 hours ago, LEGO Train 12 Volts said:

Another awesome tank! :wub:
Beautiful detail of the frame with the suspensions :thumbup:

Thank you very much! I think historical accuracy is one of the most important features to have a this scale.

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Amazing tank! I like this one best of all your tanks I have seen so far.

As someone who faced the issue of not having a proper sized drive sprocket (but at a much smaller scale) I really love the brickbuilt drive sprocket! Incredible. Wish that were possible at smaller scale :oh:

Well done M8.

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8 hours ago, Gray Gear said:

Amazing tank! I like this one best of all your tanks I have seen so far.

As someone who faced the issue of not having a proper sized drive sprocket (but at a much smaller scale) I really love the brickbuilt drive sprocket! Incredible. Wish that were possible at smaller scale :oh:

Well done M8.

Thank you! I was honestly very surprised it worked when I first designed it.

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