Tatra’s famed and proven central backbone tube, with independently suspended swing half axles, guarantees sublime off-road capabilities. But to maximize the possibilities the Dutch legislation offers, the factory 8×8 set-up needed some modifications. The final outcome: over 100,000 lbs street-legal GVW on just eight wheels.
Thanks to the wide spread axle conversion -at least 180 cm axle spacing is required- each axle (a couple of swing half axles, in Tatra’s case) is now rated at an axle load of 11.5 metric tons, which is the legal maximum for a drive axle. Furthermore, the rearmost axle was changed into a steering axle.
Also, the factory air suspension is combined with hydraulic cylinders. You must have noticed the super singles all around, so this Tatra is a true eight-wheeler indeed.
That’s a simple sum, add up the axle loads and the result is 46 metric tons (101,413 lbs) GVW. The payload capacity, also stated on the dump bed’s side, is 27.8 metric tons (61,290 lbs). Thanks to its three steering axles and an overall length of only 9.25 m (30’4”), the burly Tatra can make tight turns like a champ.
The cab and engines for the Phoenix-series are sourced from DAF, the transmissions come from ZF. The inline-six turbodiesel is either the 10.8 liter MX-11 or the 12.9 liter MX-13.
Some action on a sand track, featuring the same demo-truck. An advice to the videomakers: next time, when a heavy off-roader is the main character, just play the authentic diesel engine roar as music.
The Tatra Phoenix (available as 4×4, 6×6, 8×8 and 10×10) trucks and tractors are sold and serviced by multiple DAF dealerships throughout the Netherlands, as these are a welcome addition to DAF’s factory product line (photo courtesy of ESA Trucks Nederland). Hang on there!
Related article (with plenty of central backbone tube and swing half axles pictures):
CC Global: 2017 Tatra Phoenix 4×4 Tractor – The Famous Tatra Features Are Included
Agree about the soundtrack. The music was tolerable but the Shut up and sit down lyrics seems a poor choice for an otherwise very entertaining video.
Ha, I didn’t even notice the “lyrics”. I only played the video with the volume utterly close to mute, right from the start.
What a beast! I had some experience aligning twin steer concrete pumpers, I would love to see the setup they use to align this setup. Also curious to see the central backbone tube.
xr7, click on the link at the bottom of the article for some backbone tube pictures. And here’s a photo from Tatra’s website:
Regarding aligning, here’s a Dutch video (ca. 10 years old), showing the alignment of a self-propelled crane with multiple steering axles:
About ten years ago, the Czech embassy in Washington, DC hosted a show of Tatra products and other Czech vehicles, and I was able to visit there. This included about a half-dozen spectacular vintage Tatra cars, about a dozen motorcycles (not Tatra… I remember a few Jawas), and some big new trucks.
Inexplicably, all of my pictures from that day have vanished, except for this one, of my then four-year old daughter in front of one of the big Tatras (sorry, I don’t know the specs). The trucks were very impressive to look at, and quite a treat for those of us who would never otherwise see one.
It was a great show – the cars and motorcycles were privately owned, but I assume the Tatra Company (or the Czech gov’t) paid to have the trucks shipped to the US for that event, which must have been at a pretty hefty cost.
Incidentally, they offered spirited motorcycle rides around the embassy grounds to anyone who was interested (Helmet laws? Who needs ’em… we’re on foreign property!). My daughter got two fun rides on vintage cycles. Sadly, no such rides were offered for the cars or trucks.
Thanks, that must have been an interesting event for sure! Too bad about your pictures, but fortunately you still got the one that matters from a family point of view, so to say.
Eric703,
as I own a Tatra T2-603, The embassy asked me to bring my car to that event, but I had other obligations out of the area, and could not attend. I have always regretted not being able to be there.
Wow, that’s neat. As an attendee, it was amazing to see so many Tatra cars together – after all, just seeing one would be almost monumental. Unfortunately, I can’t remember the details of the cars themselves, except that a few of them came from Florida.
The event itself was held in conjunction with a larger “open house” type weekend that many Washington embassies put on simultaneously for PR purposes, and these open houses tend to attract significant crowds, but few in the crowd were auto enthusiasts. Still, it was a great event, and great weather for the outdoor event, too.
Thats quite a truck for off highway use 8 wheelers are almost useless in mud and sand especially unladen you need weight over the drive axles and as much as possible and 8 leggers distribute the load far to well, worse if you are pulling a trailer as well. Dunno about 46 tonne without a trailer I dont reckon that would be allowed here even with super singles.
…and to think Tatra even offers a 12×12.
I’ve been a serious Tatra person, and have owned a couple of the cars, but never the trucks. When the US investors bought the company back in the 1990s and converted to building regular ladder chassis trucks with solid axles and water cooled engines, I lost interest in the trucks.
I’m glad to see someone at the Tatra Truck factory realized buyers wanted trucks with the flexible axles. For many people, they don’t know how these trucks can be made without any u-joints [u-joints are the most common big truck drive line failure parts]. Here is how it works;
Inside that central tube runs a multi-section drive shaft. Where each axle is located, there are a pair of ring gears that face each other. Each axle half is connected by a pinion gear that is able to swing in the same arc as the ring gear surface. As the axle travels up and down, it’s always in touch with the ring gear.
The opposite side axle is in touch with the other ring gear, but as it’s on the other side of the central tube, and the ring gear is facing 180 degrees from the other ring gear. So both axle drive shafts are rotating in the same direction.
As long as the big rubber flex seals between the axle shafts and the central tube frame are not torn or leaking, everything is protected from dirt & moisture. It’s really a very simple design.
When the big tatra trucks had air-cooled engines, they offered a special dump body with inner and outer walls, and the hot air from the engine was ducted into the dump bed. This was very popular in the Soviet Union where the warm dump body sides kept the contents of the bed from freezing to the sides of the bed.
In my mind’s eye I can visualize that, but apparently not quite, because one ring-gear keeps turning backwards. Lol
So were are the differentials located?
Axle differentials and inter-axle differentials?
Watch this carefully. You mind’s eye will now see it properly.
Paul, thank you for the video. The older Tatra trucks I saw had the ring gears on the main drive shaft, and the pinion gears on the axles, but with my poor memory, I might have it backwards!
What the video does not show is that when the axle pivots upwards, the gears are still in total mesh. It was a brilliant design, and remains the only big truck to not have a single u-joint in the drive line, yet have independent suspension on all wheels.
The video also shows a planetary 2-speed setup on the input side of the diff.
Okay, obviously a different design than Bill’s description, that took care of the backwards turning ring-gear. lol
Bill, the “planetary 2-speed” is the missing differential I was looking for. Unusual because the differential work is done on the input side, via inner/outer pinion shafts. Different than typical differentials, located at the output side, within the case.
If you use your mind’s eye to strip away all but two pinion gears, one pink, one aqua, you can conceptualize the differential’s operation.
But wait, now think about passing power along to the next axle… If inner and outer shaft (turning at different speeds during differential operation) both pass-through, how does that affect “downstream” activity? Does the downstream differential work to reverse the mismatched speed from upstream?
Of course the second axle may also send power downstream even further, to a third axle, and, there could be a simultaneous need for differential action at that axle.
I’m getting a headache. lol
The central drive shafts running in the center tube frame, are all connected in one long shaft front to rear.
Is this of any help?
Thanks Dutch, however the link doesn’t click. I’m guessing it was this?
https://youtu.be/yAXoiSQUCJc
Again, not so clear on power flow. The graphic indicates only a single driveshaft. Watch the components as they “telescope” together.
So, for example, at 0:30 the blue pinion shaft sees 50% of load, pink sees 50% of load – fair enough. However, if a second (or more) axle is “daisy chained” to the blue colored pinion, that would place 100% of downstream loads on 50% of upstream components. So, with three axle configuration, blue pinion shaft would see 5/6 of load, with blue pinion shaft at just 1/6.
That is: 1/6 (50% of #1 axle) + 1/3 (100% of #2 axle) + 1/3 (100% of #3 axle)
That’s 5/6 of load on blue pinion shaft, and just 1/6 of the load on pink pinion shaft.
Okay, so we supersize blue shaft to handle nearly all of the load, problem solved? No, because torque would be split along the same lines; a new quandary.
Obviously the design is workable, so my guess is that the graphics are not detailed enough to answer my original pondering.
And here’s a still graphic from Tatra’s web site. You might want to go there:
https://www.tatratrucks.com/why-tatra/tatra-vehicle-design/tatra-vehicle-design-1/
Thank you.
Although I still couldn’t find anything on the ancient Chinese secret used to execute differential operation with multiple axles. My mind’s eye could see where wheel slip could compound speed up to 2x for each differential in the “chain” to the slipping wheel.
Interesting that the site shows Tatra simultaneously having significant investment in rather conventional construction of chassis and drivetrain for rough terrain trucks. Apparently the cost/complexity/application of either system doesn’t suit all customers?
I’m so glad you said that, JimDandy – me too!
And thankyou for the vid, Paul, (though to nitpick, one’s mind-eye doesn’t need to operate if one’s eye eyes can see it in the vid, surely?!)
It’s quite brilliant, really. Elegant, even.
Thanks for this look at these remarkable trucks. I never get tired of seeing them in action.
I have 2 Tatra factory promotional vodeos from the Paris-Dakkar rally in 1986, but the factory would not give me permission to post for the public, it shows the Tatra 6X6 truck at high speed over a bump, with all 6 tires about 1/2 meter off the ground!
The closest I can find to the 1986 P-D rally that features Tatra is this video from 2017, where Karel Rosenkranz at the Tatra Museum brings the original 1986 6X6 out to a sand quarry with the 2017 Tatra 4X4 P-D rally truck, and they run around the quarry. That video is here:
https://duckduckgo.com/?q=tatra+paris-dakar+rally+video&t=chromentp&iax=videos&ia=videos&iai=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DCpQ58AhT7VQ
I worked for Tatra in Holland during the holidays and it was the best job ever.
Especially the T 813 they sold was a real best, 8 x 8 which was a hardly known configuration from other brands, you had 6 x 6 Mercedes, Henschel, king Magirus and its direct air cooled opponent the Tatra 148.
I helped to prepare new trucks for the Dutch market, changing Barum tires to Michelin on tri-lex rims, change head and tail lights, and install proper gauges from VDO binning the Czech ones, one could not read what they were there for.
I also drove the company Ford Transit Mk I bus and commuted some collegues to and from home which was great because I had it for the evening to go around and the guys in the workshop made a beast of this Transit.
The big boss was a Czech guy who was invisible but he drove the only Tatra 613 on non diplomatic plates in Holland. And although we were over 50% Czech State owned, this company was run very liberal .
We always had to test modified T 813’s and 148’s before they were further prepared in tne paint booth and we had a few oldtimer dumptruck drivers who gave demo’s to potential customers and they also brought trucks to the companies that supplied and instalked the dump bads like Piet Ruizeveld. These retired drivers were great guys, one of them said to me : ‘you changed the tyres and the lights, you do the test drive and bring it to the dump bed company, I’ll take the transit. He put it on green Dutch dealer plates and there I went for a test drive with me behind the wheel and him in the Transit!
The screaming air cooled Diesel,the gear lever that was impossible operate, the heavy brakes, the steering everything worked like you were fighting a Gorilla !
But that day nobody was able to wipe the smile from my face.
Nice tale.
What Justy says!
The Piet Ruizeveld company you mention is still very alive and kicking. And speaking of a Tatra/Ruizeveld combination, here’s a Tatra Phoenix 10×10 with a Ruizeveld dump body. Note the 4 steering axles. Or 8 steering swing half axles, if you wish.
My worst nightmare – not two, not four, but eight swing axles, all trying to oversteer and tuck under eachother and kill me, like some tangled-up poisonous spider! Eeek!
Not really, of course.
There’s just such wonderful and simple elegance about the caterpillar effect these flexy axles have over the landscape.
Mind, these are the only application of Rumpler Sticks* I have respect for, I do have principles, you know.
*sometimes also called “swing axles”
Swing axles were highly popular in the days of Count Basie, Duke Ellington, Glenn Miller and others. But of course I’m telling you nothing new.
Oh! You are, and you’re quite right. I’m always In The Mood to Jump on that One O’clock A-train, anytime.
Still, modern tech is as amazing as the old wasn’t, but the music sure ain’t, so mebbes the two never match up!
For those who have not seen what the Tatra 8 X 8 Trucks can do on very uneven surfaces, here is a great YouTube video:
On YouTube search, type:
Tatra 813 8×8 compilation – best of V12 Sound offroad 2012-2021
The Tatra 813 is a Czech Army vehicle, 8×8 with a large 6 passenger 4 door cab hanging over the front axles, a very powerful and effective vehicle for traversing places where there are no roads. The videos are mostly active displays of what they can do.
Thanks Bill for your comments!
Tatras are also widely used in agriculture, as straight trucks and tractors (coupled to massive forage semi-trailers, for example). In the logging business too, naturally.
An example of a Tatra Phoenix 8×8 “agritruck” chassis-cab with a hook lift system:
I spent some time discussing available info on the Tatra truck rear axles. one of my Czech friends sent me a link to a wonderful video of a Tatra truck repair facility in the Czech Republic, this video shows the entire Tatra 815 TP 6X6 rear axle, from the point where it is dissassembled, all the way thru a complicated rebuild and assembly process, to instalation in the truck, and as the head mechanic bows and doffs his hat, he drives the truck out of the shop.
He also explains [in Czech language] how the power is transmitted thru the 2 ring & pinion gears, and by using his hands he makes it possible for non Czech speakers to follow the power flow.
It also shows the planetary reduction system for the rear axle, as well as additional planetary gear reduction at each hub as well, all powered by air lines to the various actuating levers. I guess this means the driver can adapt each axle AND each wheel to different speeds, should they have traction problems.
I have watched some videos where it appears the various tires on the 8X8 chassis are rotating at different speeds, now I think I know how that’s accomplished. I can imagine the dashboard of a Tatra 8X8 equipped with a planetary gear reduction at each axle, and additional reductions for each wheel, and what the dashboard’s drive line controls must look like!
To anyone here who has mechanical and rebuilding capabilities, and understands how things generally work, but not exactly how this complicated axle assembly works, this can be a very fascinating video. I learned a lot from watching it. I now understand why these trucks can not just participate in the brutal Paris-Dakkar race, but WIN!
And do keep a watch for the 2 little mushrooms!
https://www.youtube.com/watch?v=aNkwMC6iN98
The above YouTube link is titled: Tatra 815 TP 6×6 montaż półosi – tylnego mostu, krok po kroku.
Thanks; great video! Yes, I caught the two little mushrooms.
For those who like their swing axled off road goodness in a smaller package the Puch Pinzgauer offers the same spine tube and swing axle architecture in a light duty package.