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Tatra 813 6-pack transporter
The beer must get through! This unstoppable off-road 8x8x4 is just a repurposed MOD of Madoka Arai's spectacular "LEGO Technic Tatra 813 Trial Truck" MOC.
About this creation
Please feel free to look over the images and skip the verbiage.

Just to be clear, this off-road 8x8x4 six-pack transporter is a repurposed MOD of the truly spectacular "LEGO Technic Tatra 813 Trial Truck" MOC by renowned Japanese builder Madoka Arai (aka Madoca1977 on YouTube and Rebrickable).

Madoka's own video and features on Eurobricks and Rebrickable show the starting point well.

To distinguish who did what going forward, "MOC" will refer only to Madoka's original T813 design, and "MOD", to my modification of it. All the photos and videos embedded here are of the MOD, but since I really didn't change much, all comments apply to both unless otherwise noted.





My own video below opens with the MOD at its fastest (high gear on a hard, flat surface with the hubs geared 1:1). Yes, fastest. The 2nd segment (0:52) opens with the MOD still in high gear but with Madoka's original 3:1 hub reductions instead. It then downshifts for the obstacle course. I've seen glaciers go faster.



I'd been toying with the idea of building a T813 for months when I ran across Madoka's T813 video. I put together a procurement list from his beautifully photographed online instructions on the spot. Three weeks and several costly BrickLink and shop.lego.com orders later, the MOD was afoot.1

Eastern European Technic builders have come up with some spectacular T813s, but Madoka's stands out both mechanically and cosmetically. Since he professes to have no technical training in this Rebrickable interview, I can only conclude that the guy's a mechanical genius.



Any Technic builder would do well to study his methods. His mechanisms are innovative, compact, and robust; his structures, strong but light. He makes liberal and very clever use of thin liftarms. And he's even more liberal with expensive Technic specialty parts, but always with good reason.

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Modifications

Compared to Madoka's contribution, my mods were fairly minor:
  • Made the portal hubs a little easier to regear for climbing or speed as needed.
  • Beefed up the chassis here and there, probably unnecessarily.
  • Changed the bodywork from red to yellow with black trim and tidied up the colors in general.
  • Revised the grille and cab slightly.
  • Added an easily detached flatbed, a pair of remote battery toggles, and tail lights.
  • Rewired the front and rear lights to monitor the propulsion and steering/transmission batteries, respectively.
  • Devised an ergonomic remote control handset with a T813-specific control lay-out.
The functional mods added a good bit of play value.



The flatbed comes off easily, but the red-handled remote battery controls eliminate the need to remove it just to toggle power.







The MOD was repurposed from trial truck to six-pack transporter at a recent show. I was demonstrating an early version on the floor when someone walked by with a bottle of beer. Looking back down at the flatbed, it struck me: "Hmmm, six-pack size!"



And what better way to insure an uninterrupted beer supply than with an unstoppable all-terrain 8x8x4?

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Background: The Tatra T813

The Tatra T813 (T813) is a legendary Czech off-road utility truck produced by the Tatra Company from 1967 to 1982. It's been used all over the world.

Each of the T813's 4x4x2, 6x6x4, and 8x8x4 platforms came in civilian and military versions. Madoka modeled the bare-bones civilian "cab-chassis" 8x8x4.

All versions used Tatra's unique full-length tubular backbone chassis, now widely known simply as the "Tatra chassis". Driveshafts running down the stiff backbone connected to the independently sprung swing-axles via locking differentials mounted on the backbone itself. The 8x8x4s were powered by normally aspirated 17.6L OHV V-12 diesels (199 kW, 990 N m stock).

The civilian cab-chassis 8x8x4 has become the quintessential extreme off-road truck (aka "trial truck") and is coveted by European enthusiasts to this day. A souped-up Tatra V-12 can belch enough black smoke to blot out the sun at a truck trial, but the exhaust note is magical.

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MOC and MOD review

If you're looking for a remote control trial truck to build from instructions, I can recommend this one wholeheartedly. Granted, it's my only trial truck, but it's hard to see how you could wrong with Madoka's masterpiece -- except perhaps for the cost.

The MOC is faithful to the real 8x8x4 "cab-chassis" T813 in the following respects:
  • True 8x8x4 chassis with all 8 wheels driven and the front 4 steered
  • Geared hubs
  • Independently sprung swing-axles all around
  • Tatra's signature positive wheel camber to increase wheel travel and boost traction on soft surfaces
  • Opening and locking cab doors
  • Working steering wheel and V-12 engine inside the cab
  • Windshield wipers
  • Bare chassis behind the cab
To that base, Madoka added a trial truck-style roll cage with front running lights.





There are 5 motors: 2 XLs for propulsion, 2 Ls for steering, and 1 M to shift gears. The current-hungry XLs have their own V2 IR receiver and PF Li polymer battery. A V1 receiver and a second Li polymer battery run the other 3 motors.











The main mechanical departures from the real thing include the following:
  • Lack of a tubular backbone
  • Lack of differentials. Overall, this is a winning trade-off. It greatly stengthens the MOC's drivetrain against gear skipping, but it does hinder maneuverability on surfaces that don't allow wheel slip.
  • Single 2-speed transmission rather than a 5+R with separate overdrive and auxiliary gearboxes
  • Portal rather than inline hubs with spur rather than planetary reduction gears
  • LEGOŽ shock absorbers in lieu of leaf springs
  • Lack of a PTO
Aside from the flatbed I added, these last 2 lists describe both the MOC and MOD.

The heavy-duty 2-speed remote control transmission at the center of the chassis gears down the hard-coupled XLs by 2.79:1 in low gear, but high gear is a 1:1 direct drive.



An additional 3:1 reduction occurs at the inboard end of each half-axle. The result: Pre-hub reductions of 8.37:1 and 3:1 in low and high gear, respectively.



Madoka geared his portal hubs with the 3:1 reductions seen below to enhance climbing and rough terrain performance. I followed suit in the 2nd part of the video.



The resulting 25.1:1 final reduction in low gear allows the T813 to climb slopes a good bit steeper than 30° and to overcome step-like obstacles up to a wheel radius in height without skipping. For a LEGOŽ vehicle weighing almost 3 kg, that's phenomenal.

The bad news: The original 3:1 hubs make the T813 painfully slow in high gear and downright glacial in low -- even on "ideal" (smooth, hard, flat) surfaces.

The good news: Terrain permitting, gearing up the hubs can be a simple and effective solution to the speed problem.



LEGOŽ portal hubs are designed to accommodate 3:1 and 1.67:1 reduction, 1:1 direct drive, and 1:1.67 and 1:3 overdrive ratios. The overdrive options cause too much gear skipping to be of use on any surface, but the remaining 3, shown below, are viable.



Short of full steering lock, the MOD can traverse ideal surfaces at decent speed with 1:1 hubs without skipping, and 1.67:1 hubs can deliver a bit of extra speed on gentle terrain.

Hub jobs take 10-15 minutes with practice. Next to the MOD below is the regearing kit I take to shows. The small Allen wrench makes easy work of pushing out the structural axles that hold the portal hubs in place.





Final drive ratios can range from 25.1:1 to 8.37:1 in low gear and 9.0:1 to 3:1 in high with 3:1, 1.67:1, or 1:1 hubs.

I designed the T813-specific remote control handset below to be reasonably ergonomic for adult hands.



The green levers control the XL propusion motors (which are meant to be operated in unison), the yellow steers, and the red shifts the 2-speed transmission. The layout allows one-handed operation in most circumstances.





The cab can easily shadow the twin IR receivers, and cargo can do the same, but one of the Bluetooth-based sbricks I have on order will fix that. It will also free up both IR receivers.

More importantly, however, the sbrick will make this off-road 8x8x4 a reliable performer in its natural habitat -- outdoors.



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MOD specifications

Subject:8x8x4 cab-chassis Tatra T813
Construction:Studless
Overall dimensions:592x214x245 mm (LxWxH) including roll cage
Scale:~15:1 length, ~1:13 width, ~1:11 height
Mass:~2.9 kg excluding cargo
Outfit:Flatbed
Platform:8x8x4
Steered wheels:Front 4
Suspension:8 independently sprung swing axles with positive wheel camber
Transmission:2-speed remote control
Useful geared hub reductions:3:1, 1.67:1, and 1:1
Final drive ratios:25.1:1 to 8.37:1 in low gear, 9:1 to 3:1 in high depending on hub gearing
Motors:2 XLs for propulsion, 2 Ls for steering, 1 M for gear shifting
Electrical power supply:Two 7.4V Li polymer PF rechargeables
IR receivers:V2 for propulsion, V1 for steering and shifting gears
Lights:2 sets of PF LEDs front and rear
Modified LEGOŽ parts:None
Non-LEGOŽ parts:Cargo only
Credits:Relatively minor MOD of an original MOC by Madoka Arai

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Footnotes

1 I nearly always find the lowest prices on LEGOŽ electricals at shop.lego.com, and the motors needed here were no exception. Everything else came from either my own collection or BrickLink. Good prices on the LEGOŽ parts I typically buy come along so rarely on ebay that I've stopped looking.

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Comments

Jeremy McCreary
 I like it 
White Shapes
  December 2, 2015
Your writing is always extremely interesting, Jeremy! Madoca's creations are endless sources of inspiration, and adding explanations based on real re-construction is more than valuable.
 I made it 
  December 2, 2015
Quoting Kurt's MOCs Beautiful work! The mechanics and details are great. Too bad you lost the beer bottles though!
Thanks, Kurt! We had to test all the beer to make sure that it hadn't been shaken up too much coming over the pass. It hadn't.
 I like it 
  December 2, 2015
Beautiful work! The mechanics and details are great. Too bad you lost the beer bottles though!
 I made it 
  December 2, 2015
Quoting White Shapes Your writing is always extremely interesting, Jeremy! Madoca's creations are endless sources of inspiration, and adding explanations based on real re-construction is more than valuable.
Too kind, WS! Couldn't agree more: Every Technic builder should study Madoka's methods. Too bad he doesn't post here.
 I made it 
  December 2, 2015
Quoting Nick Barrett Madoca is a genius, and you don't need to change his truck much! Thoughtful mods and thanks for the tech. specs; Tatras are a very Eastern European thing - not seen elsewhere - but they must be pretty good.
Thanks, Nick! Genius indeed -- I learned a great deal from building this Madoka masterpiece. Stay tuned: I have one more to post.
 I like it 
  December 2, 2015
Madoca is a genius, and you don't need to change his truck much! Thoughtful mods and thanks for the tech. specs; Tatras are a very Eastern European thing - not seen elsewhere - but they must be pretty good.
 I made it 
  December 2, 2015
Quoting Topsy Creatori Technical magic aside... looks great in the outdoor shot too! :)
Thanks, Topsy! It's much happier in its natural habitat.
 I made it 
  December 1, 2015
Quoting Nerds forprez Yea! Wonderful build Jeremy, I love all the exhilarating spinners you create, but love that you made something different even more. As with Gabor.... I also see a problem that no one else has noticed. The "beer" is non-alcoholic! So... Does it really need to get through? Lol...
Thanks, NFP! Darn, you caught me. (Just trying to establish plausible deniability in case the moderators freaked out.)
 I like it 
  December 1, 2015
Technical magic aside... looks great in the outdoor shot too! :)
 I like it 
  December 1, 2015
Yea! Wonderful build Jeremy, I love all the exhilarating spinners you create, but love that you made something different even more. As with Gabor.... I also see a problem that no one else has noticed. The "beer" is non-alcoholic! So... Does it really need to get through? Lol...
 I made it 
  November 30, 2015
Quoting T.J. Brammer That's one nice truck you have there!
Thank you very much, TJB!
 I like it 
  November 30, 2015
That's one nice truck you have there!
 I made it 
  November 30, 2015
Quoting Oliver Becker What a great vehicle, Jeremy! Maybe, getting the beer coming in by airplane from Bremen/Germany must be a lot more expensive than the bill for the bricks...?! ;) LOL
Thanks, Oliver! They must ship the beer pretty cheaply (container ship?), because I could get many, many cases of Becks for what this baby cost.
 I like it 
  November 30, 2015
What a great vehicle, Jeremy! Maybe, getting the beer coming in by airplane from Bremen/Germany must be a lot more expensive than the bill for the bricks...?! ;) LOL
 I made it 
  November 30, 2015
Quoting Elk Guard Amazing work, well done!
Thank you very much, EG!
 I like it 
  November 30, 2015
Amazing work, well done!
 I made it 
  November 30, 2015
Quoting matt rowntRee The beer must flow! Seems that alcohol and Lego go quite well together. Plus, you can get sloppy, wreck the truck, then rebuild it and your insurance won't go up. WIN WIN! Awesome modifications there, my only problem is that there seems to be no more beer. Brilliant!
Thanks, Matt! Don't worry, it's already headed back for another load. The good and bad news: It's so slow that our blood alcohol levels will be back to zero by the time it gets here.
 I made it 
  November 30, 2015
Quoting Seaman SPb Fantastic work!
Many thanks, Seaman!
 I made it 
  November 30, 2015
Quoting Nils O. What a practical use for such a great model. The modifications are cool, the new purpose even more ;-)) Great job! :-))
Thanks, Nils! I believe in making my LEGO earn its keep.
 I made it 
  November 30, 2015
Quoting Gabor Pauler Even it is a MOD, it is also a masterpiece. Sometimes modifications jump to new level of quality. I have only one problem: I cannot find TLG part 'Becks 6 pack' in LDD. Can you write me its part ID? (If you have time, you could model Becks 6 pack also from lego, hehe...)
Many thanks, Gabor! Unfortunately, TLG doesn't have a beer-making license, but a LEGO 6-pack carton is a great idea. Wouldn't be all that hard, either, but this was arguably my most expensive Technic build ever, and the Mrs. would kill me if I spent another penny on it.
 I made it 
  November 30, 2015
Quoting Stephan Niehoff Ohhh yeah, I love the Charge, Cheers. That puts the car into the background.
Thanks, Stephan!
 I like it 
  November 30, 2015
The beer must flow! Seems that alcohol and Lego go quite well together. Plus, you can get sloppy, wreck the truck, then rebuild it and your insurance won't go up. WIN WIN! Awesome modifications there, my only problem is that there seems to be no more beer. Brilliant!
 I like it 
  November 30, 2015
What a practical use for such a great model. The modifications are cool, the new purpose even more ;-)) Great job! :-))
 I like it 
  November 30, 2015
Even it is a MOD, it is also a masterpiece. Sometimes modifications jump to new level of quality. I have only one problem: I cannot find TLG part 'Becks 6 pack' in LDD. Can you write me its part ID? (If you have time, you could model Becks 6 pack also from lego, hehe...)
 I like it 
  November 30, 2015
Fantastic work!
 I like it 
  November 30, 2015
Ohhh yeah, I love the Charge, Cheers. That puts the car into the background.
 
By Jeremy McCreary
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