Tatra T815 my saga ...,

[T815]

They are a independent swing axle design housed in a central drive tube, ever seen a Pinzgauer ? There many in the US, designed by Erick Ledwinka the son of the Tatra driveline originator Hans Ledwinka, engine removed, front spring suspension with airbag rear axle (no air)

 

[Haf-E]

Tatras (along with pinzgauers and haflingers) are built with solid half axles that pivot at the differential which is attached to a central tube that forms a backbone for the chassis. The angle of the wheels changes as the axles flex. Seems crazy but they are a simple, rugged and well handling solution for trucks which carry loads. The ride is surprisingly soft. Uneven tire wear can be a problem though. These three trucks were designed by the same guy (well sort of- his son designed the pinzgauer...)

 

[Haf-E]

Here is a good graphic of the axles / chassis of a Tatra

http://www.team-bhp.com/forum/attac...navy-airforce-vehicle-thread-tatrat8158x8.jpg

 

[T815]

Here is a cut away of Tatra axle & drive tube with remote locking Diff's & inter axle diff, these photos I took at the Factory on one of there open days

 

[Haf-E]

That's a great photo of the internals on the Tatra - the differential is similar to the Pinzgauer's with the dual ring gears (one for each axle) which eliminates the need for CV or U-joints for the alxes - the ring gears rotate around the pinion as the axles flexes. The amazing part of the tatra is that it has inter-axle differentials and diff-locks - I've been told that an 8x8 tatra truck has 7 differentials and 7 diff-locks in its drivetrain - is that correct?

The Pinzgauer is a much simpler version - even the 6x6 Pinz only uses three diffs - there is no "interaxle" differential and, although they each have their own diff lock mechanism, the rear two are actuated together at the same time with a single lever. The Pinz does have portal axles with the smaller wheels, while the Tatra uses planetary since the wheels are so much larger. The central backbone chassis is very similar.

 

[BuffaloFunk]

Interesting. Looks very simple yet very effective.

So, the entire axle and ring gear can rotate/flex laterally around the central back-bone tube? What prevents the two ring gears from hitting one another if, say, both wheels were to come off the ground (axles flex downwards) or hitting a large bump caused the axles to flex upwards?

 

[T815]

I have worked on Pinz's but not there driveline, so you know more than myself,.
Tatra 8x8 will have inter axle diff in front of the transfer case then the R&P diff's are on the rear side of ft axles & front side of rear axles so in total an 8x8 will have 5 diff's. & 8 R&P's, on the lockers they just have 2 switches 1 press & hold for all axle lockers, 2nd on/off for inter-axle which Tatra calls moment divider, I plan on converting the system to just air signal from cab with Bendix lever switch 1 for rear, 2nd for front + 3rd for inter, factory uses elec/air solenoid system with relay & fuse so going straight air will greatly simplify.

Driveline ground clearance is about the same Pinz's. V Tatra with mil tires

 

[T815]

Interesting. Looks very simple yet very effective.

So, the entire axle and ring gear can rotate/flex laterally around the central back-bone tube? What prevents the two ring gears from hitting one another if, say, both wheels were to come off the ground (axles flex downwards) or hitting a large bump caused the axles to flex upwards?

The R&P's are slightly staggered so 1 side of swing axles is slightly ahead of the opposite side, the bearing journal segments for the swing axle run in the same housing the R&P's cannot collide, openings in the housings also limit, there is some work to do here as the factory bump stops do limit the travel from the max available but have to be careful to not overdo increasing travel to stop swing axle from hitting the opening

 

[Undy]

What prevents the two ring gears from hitting one another if, say, both wheels were to come off the ground (axles flex downwards) or hitting a large bump caused the axles to flex upwards?

Pinzgauers have limit straps at each wheel to prevent the axle from dropping too far down and causing damage. It's common to have one or more tires lift off the ground on really rough terrain.

 

[T815]

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[biotect]

Hi T815,

Great thread! I'm a real fan of the Tatra 815, gradually learning about it over the last year or so. It's a terrific vehicle, and I hope that Tatra survives.

How would you say the Tatra T815 stacks up agains the MAN SX series of trucks?

Should be clear that I am coming at this more from a “design” point of view, as opposed to engineering. I am a designer living in London, whose MFA thesis project will be a “fully integrated” expedition motorhome based on either a MAN SX-44 6x6 chassis, or the Tatra T815 6x6. Started a thread on ExPo to explore some of the issues, titled “Fully Integrated MAN or TATRA 6x6 or 8x8 Expedition RV with Rigid Torsion Free Frame”, at http://www.expeditionportal.com/for...-8x8-Expedition-RV-w-Rigid-Torsion-Free-Frame .

Just recently I put the same question to egn, the other main participant on that thread -- see http://www.expeditionportal.com/for...pedition-RV-w-Rigid-Torsion-Free-Frame/page26 and http://www.expeditionportal.com/for...pedition-RV-w-Rigid-Torsion-Free-Frame/page29 :

So which would be better, a MAN SX-44 (if one can find one...), or a Tatra 815 6x6, either commercial or ex-military, of the sort that Jago Pickering used for his expedition motorhome? On the plus side:

•....a used Tatra Phoenix or T 815 6x6 chassis would probably be easier to find than an SX-44 chassis
•....a Tatra chassis would probably cost much less than a comparable SX chassis, whether built new, or found used
•....a Tatra chassis would be even stiffer and more torsion-free than an SX-44 or SX-45 chassis

But on the downside:

•....Tatra is a small company in comparison to MAN, and Tatra's service network is not nearly as large
•....Tatra's ownership has changed a number of times over the last two decades, and Tatra's future always seems somewhat in doubt – see for instance http://www.opinicus-sro.com/Tatra-et-son-futur-en-point-d
•....The Tatra 815's central tube-frame might be heavier than a comparable MAN SX-44
•....The Tatra's 815's fuel consumption might be comparatively high

[egn], are you certain that the weight of a new Tatra T-815 military-grade truck would be more than the weight of a comparable SX-series truck? Remember, I checked the weight of a commercial Tatra Phoenix 6x6 truck, and it did not seem to weigh more than a comparable Zetros 6x6.

Are you also certain that a Tatra's fuel consumption would be much worse than an SX-series truck, especially now that Tatras can be fitted with lots of different engines, from different manufacturers? Again, see http://www.tatratrucks.com/why-tatra/tatra-vehicle-design/tatra-engine/ , http://en.wikipedia.org/wiki/Tatra_815 , http://www.tatratrucks.com/trucks/product-catalog/t-815-7/ , http://www.tatratrucks.com/trucks/c...-trucks/6x6-high-mobility-heavy-duty-chassis/ , http://www.tatratrucks.com/underwood/download/files/tatra-t815-790rk9-6x6-chassis_en.pdf , http://www.tatratrucks.com/trucks/c...-trucks/8x8-high-mobility-heavy-duty-chassis/ , http://www.tatratrucks.com/trucks/c...ity-heavy-duty-universal-cargo-troop-carrier/ , http://www.tatratrucks.com/trucks/c...ility-heavy-duty-universal-container-carrier/ , http://www.tatratrucks.com/underwood/download/files/tatra-military-vehicles_en-2.pdf , http://www.military-today.com/trucks/tatra_t815_78or89.htm , and http://www.military-today.com/trucks/tatra_t815_7mor89.htm .

It would be great to have your input on this.

Also, if you know something about the MAN-KAT and HX/SX series of trucks, and if you'd like to answer any of the other questions that came up in the thread with regard to the same, would be great to have your input on those, too. And if I made any mistakes in the thread, please correct me!

All best wishes,


Biotect

 

[T815]

As for stable platform Tatra wins hands down, reason it's been top choice worldwide in military applications. MAN is conv' as in rest of the world truck, Tatra is unique, MAN has more articulation + designed chassis flex, Tatra in comparison is rigid triangulated chassis - drive tube design has more limited travel, less articulation but also due to its independent suspension the truck remains far more level than beam axle truck on the same terrain. Tatra is far more user repairable than MAN along with parts prices probably at least half of MAN
I have video on YouTube 2007 DVD show in UK you can see from my free hand camera how much smoother the T817 8x8 V MAN 8x8


Sent from my iPad using Tapatalk

 

[madtom]

Hi from Czech republic - nice to see, that also in US Tatra looks unique.
Look here for a RC model: http://www.rctatra.com/model
Some years ago I was driving 8x8 Tatra. Later as a passenger tried it on trucktrial on with Dakar race truck during testing. It cannot be compared to my Land Rover Discovery2. it is much bigger. Even on test track in the Tatra factory it is quite different.

 

[T815]

Tatra T815 transport & dis-assembly



Back in Oct 2014 I finally made the trip from MT - MD to collect my Tatra from storage, after loading I made a detour north to Eastern Surplus in Philadelphia and purchased a set of NOS Hutchinson forged alloy 2-piece military wheels + beadlock inserts




I unloaded the truck in ND at the company I work for, between Thanksgiving & Christmas I stripped the truck down to a rolling cab & chassis, I scrapped all the rusty rear bed, side skirts, fenders, removed the winch, tow hook, 5th wheel, cut approx 12" off the rear frame to reduce rear overhang






During that time I also purchased Detroit Diesel 8V92ta from a Gov' Liquidation Auction, it was missing a few parts however I didn't know exactly how much as like most people I purchased site unseen, it turned out they (Army) had removed a few internal parts, however I did buy a very good unit with very low hrs,
Currently due to all the mud in our yard, spring thaw, I am focusing on the engine as this is a large psychological stage to accomplish, having a running engine ready for the installation.


Gov' photo from auction

Prepped and ready for re-assembly, I should have it running by end of April

 

[dwh]

Progress yay! Been looking forward to hearing something about this one for quite a while now. The pictures in the snow make it look like it's located somewhere in Siberia. Looks right at home.