tatra 813 new owner

[cranetruck]

Question about your "3-circuit brake valve", does it provide protection to the remaining air system if one circuit fails? If that what is does, I think I could use one on my 8x8, where one broken air line will cause a complete brake malfunction (except for the trailer protection valve, which separates the trailer air from the truck itself)....Unless it's in the system and I haven't found it yet.

Note: I see only one "stop light switch", so perhaps I'm wrong about the function of the valve.

Edit: Come to think of it, the kind of protective system used would depend on how the brakes are activated, air activated springs, air over hydraulic or 100% air (no springs to lock the brakes in case of air failure).

 

[duncan]

Duncan, I take it that the Wabco unit you installed is not an original Tatra part....what model # did you pick? Is it also a dryer or only a passive filter/oil/water/separator?
Where in the air circuit did you place it?

Dont know the part # by heart, but its not related to tatra in any way. I just went to the truck parts dealer and got a single-circuit air processor. You can get them as complex as you want, seen some with up to 6 circuit protection.
It's an air dryer, filter, separator, pressure regulator and one-way valve in one unit, and has an electrical air heater that automaticly kicks in below 45F.

I placed it halfway down the truck, so about 4 metres from the compressor. It's directly on the main air line running from the compressor to the first air tank.

The original system had a labyrinth-style water separator with manual bleed valve in this same position. Then the air went all the way to the back of the truck where the anti-freeze resevoir and the old pressure regulator and oil separator were located. From there it went back to the main air tank. That's all replaced now

Come to think of it, the kind of protective system used would depend on how the brakes are activated, air activated springs, air over hydraulic or 100% air (no springs to lock the brakes in case of air failure).

Ill answer this one first Theyre single chamber fully pneumatic brake cylinders. Newer 813's do have air over hydraulic. No spring locks for failure and handbrake.

The handbrake is mechanical and acts on a seperate brake drum which is on the main driveline. Essentially it does the same thing as leaving the truck in gear, it locks the driveline. It does mean you can not winch with the truck on handbrake, since the winch is powered directly by the driveline. You can see the drum clearly on that picture with the air processing unit.

Question about your "3-circuit brake valve", does it provide protection to the remaining air system if one circuit fails?

It does. It's a very basic but essential system, divided in 3 parts. On the picture from left to right (so on the truck from back to front):
- Trailer
- Rear 4 wheels
- Front 4 wheels and front trailer coupling (its for manouvering only anyway)



Ive rotated the picture so its in the same position as the valve on the truck. The air supply line is the on the bottom. From there it feeds 3 identical brake valves.
First the air passes through a one-way valve, so no air flows back from the brake system into the main system. Losing the main air doesnt mean you instantly lose the brakes. After that one-way valve the air is stopped by the actual brake valve. It goes through the lower ports into the 3 air tanks that are on the back of the truck. A seperate one for each circuit. I could lose an air tank and still have the other 2 working.
When you brake, the brake valves are pushed open with a calculated set of rods, springs and pins to make the truck use the rear brakes a little more agressive than the front. Or the other way around, or something. Either way someone thought about it The air can now flow from each brake-air tank to each system, seperately. It's a good system, and its mandatory on all modern trucks. As I mentioned before, nowadays they even go up to 6-way systems, and not just for braking.

I see only one "stop light switch", so perhaps I'm wrong about the function of the valve.

Well since all circuits are activated at the same time, it doesnt matter on which one you put the brake light switch.

If that what is does, I think I could use one on my 8x8, where one broken air line will cause a complete brake malfunction (except for the trailer protection valve, which separates the trailer air from the truck itself)....Unless it's in the system and I haven't found it yet.

You could connect the rear wheels' brakes to that trailer circuit Should be an easy change, and saves you from buying and installing a different brake valve.
It does ofcourse mean that if your trailer snaps a brake line you only have front axle brakes, but I assume you dont tow many trailers with it anyway.

Might actually be smarter to link the front axles to that trailer brake circuit, instead of the rear.
Could even go crazy a bit and make it selectable using 2 manual valves (or one double valve), one to connect 2 of the axles to the trailer system, and one to connect it to the regular system. You could then choose which brake system acts on those 2 axles.

 

[cranetruck]

Thanks for the reply! You got me thinking.

The 757 also uses 100% air (no hydraulics), so it offers a number of alternatives as you just described.
It also has 3 air tanks with check valves for limited safety and the hand brake works on the driveline like you described for the 813...

The water separator shown in one of the above posts, is not used in the brake circuit, but for the air used to pressurize the brake drums. It is separated from the circuit which pressurizes the axle housings.
No air dryer here, just an alcohol evaporator for the entire system, located in the intake plumbing of the compressor.

Was the Tatra brake valve discussed above, part of the original equipment in 1974?

 

[duncan]

Yeah that brake valve is tatra original.

A water separator (actually air processor in general) is vital to keeping the entire air system in good shape I think. With all the cylinders, valves, and not to forget the metal piping, moisture and dirt are something to be affraid of.
With the inside of the air system being kind of tough on the maintenance side of things, anything helping to preserve it will be well worth the time and money.

 

[EZFEED]

WOW! Duncan you have knocked a bunch of this baby out!

 

[cranetruck]

BTW thanks Chris (or was it Mike?) for fixing it so that this "Tatra" category shows up on the main page.

 

[duncan]

WOW! Duncan you have knocked a bunch of this baby out!

Yeah was lucky to be jobless for 3 weeks, spent all 21 days working on this baby from 8 to 6. The only thing keeping me from completely finishing it is a lack of finances right now. Apparently that comes with job-loss too
Started on a new full-time job this month. Leaves me with little free time, but I have to make up for those 3 weeks of not getting paid while spending a lot on the truck. Life tends gets very expensive very fast that way. It's looking good though, at this rate Im confident Ill have the money to finally buy that new cabin somewhere in january. Yeehaw!

The thought alone makes me smile A lot Got the car waiting, a trailer arranged, the trip all planned, just need a date and a wad of cash.

 

[EZFEED]

Well sounds like you got hit like me as well....didn't lose my job but my free time. Affects the same way though
But hey! Looks like you rebounded...at least you have income again and moolah to finish!!!!!

About your injectors....DO INDEED take them apart.....you wont believe the crud that you'll find in there!!!! Its amazing but they will still function fine dirty....just not effectively. You'll be burning fuel like crazy and probably smoking.
I've noticed my acceleration was getting less and less crisp and I had to advance the hand throttle a little more to get to the idle sound that I used to be at. At full sustained speed 60-70kmph (35-45mph) on the stretch from my house to Eunice, LA where the feed store is at I have noticed that I have gone from 12-14mpg down to between like 8 or 10mpg....thats a chunk also noticed my exhaust smells acrid and quite literally will make you cry if you stay in the shop while warming up.....doesn't smell sweet anymore....this is(was) the source of the unburnt fuel.

The filters in the extensions will filter down to 2 microns and the clearance in the injectors is greater than that. There are like four or five traps after the primary fuel filter that the fuel has to pass through before it gets sprayed into the combustion chamber so its safe to assume you are quite cool mechanical wise.
The injector pump is protected the same way as well as the individual injectors so you should have ZERO mechanical problems unless corrosion has eaten away the seats and sealing surfaces or particles smaller than that have packed up in the housings.
By the way...DO NOT TAKE THE I.P. APART.....

When I got to looking at mine I noticed the clamps were not tight (be careful torqing them back by the way...do in sequence as described in your manual. If you dont have this then let me know) and I was getting blow-by on combustion through the injector port. This also cause the tips to soot up and all of that crap got forced back up into the tip. Out of the 5 ports per tip I had llike 2 or 3 still flowing on 4 of the 6 injectors. Also I found water trapped in each injector and that was causing some corrosion problems on the spray needle but nothing serious...not where it counted actually. I am sure the water would have burnt out if the injectors werent loose and the gasses blowing by. That kept them from heating up.

These things are suuupppper easy to fix so dont worry bout it! The only thing you need to do is be careful to not try and force anything because the parts are heat treated and are hard enough to where they can break before they bend. Use a little ball peen hammer and tap while applying gradual torque pressure to them. Also.....FORGET trying to separate the nozzle nut from the nozzle itself. Most likely carbon has glued them in and also I have heard that sometimes they were locktited in place (or whatever the compund that was available back then) so if they wont slide out then dont worry bout it. The tips dont unscrew they are slip fit.

After going through them, hook them up to the hand pump and set to whatever your book says to set them at. Mine has a measurement in ATM, BAR, and Kiloponds....came out to 2,418psi. Just hook it up, loosen the jam-nut, and screw the threaded sleeve in or out depending on desired amount. Clockwise to increase pressure, counterclockwise to decrease. Tighten the jam nut once set.
Oh...and the this central part of the injector is just for overflow. I only even get some overflow when I'm at high RPM. This overflow just dumps back into the tank.

The injector works like this. In the I.P there are 8 pumping elements, one for each cylinder. Each is set to squeeze diesel at a certain pressure for a certain amount of time into the injector line at a certain point with respect to cam position. This amount will be slightly greater than what the injector is pop set to. When the pressure increases the diesel is squeezed into the lower portion of the injector tip and because of clearances (more room for pressure to act upon the bottom of the spray needle) when this pressure increase happens it acts upon the lower part of the needle and tries to shove the needle up against its spring pressure. Once the pressure exceeds the pop setting, the needle lifts and immeadeatley diverts to the area of least resistance....out of the tip. Once pressure drops the needle closes once again. For my truck this is set to 170 Kiloponds per square cm which is 2,418 psi and that pressure is held for like half a second to allow sufficient spray into the combustion chamber.

 

[dejv]

Hello guys! I've seen a site about conversion of one T-815 to mobile home. After long googling, I could find a small overview about that car and info that it was for sale:
Expediton Vehicles

Do you know anything about fate of that vehicle?

Kind of reminds me of "Tatra around the World" vehicle that run the expedition in 1987-90.

 

[duncan]

EZFEED: thanks for the wikipedia-sized reply Really helpful. I forgot to make some scans of my paper drivers manual, it has more info on the injectors than the workshop manual. Apparently they consider it the drivers job to clean and adjust the injectors... try asking that to a modern car owner Anyway, I'll definately go and clean them after reading that. Just not sure when, its a non-vital job that can be done easily when the truck is reassembled, so it doesnt have priority at the moment.

A thing that does is my diesel tanks. One was rusted up pretty bad because it hadnt been used for year and left empty. The other one seemed ok, and I drove off that. When I removed it a while ago it sprung a leak when I sat it on the ground. I rolled it over to have the leak on the top and it sprung 2 more holes. **** happens, guess both tanks are fubar.
Got a quote for new tanks but that's going to cost me somewhere around $1100... go figure! The second, obvious choice is to make my own tanks. The original ones are very thin walled, looks to be something like 0.8mm. So Im now looking at buying some sheet metal to make a new tank, and make it a little more solid. Waiting for a quote on a 3x2 metre sheet between 1 and 2mm thick. We can cut that in 2 long small strips, bend them and weld covers on. Cut the filler cap and fitting out of the original tanks and weld them in the new ones. Should be a piece of cake, and a lot cheaper, not to forget stronger.

Do you know anything about fate of that vehicle?

Ive seen that site but never found any more info on the project. Guessed it was either rusting away somewhere abandoned, or happily cruising remote places of the world where keeping-an-internet-blog-up-to-date is not high on the list of things to do.

 

[duncan]

Ow and more info on the "Tatra around the world" thing, if you havent found it already, is here:

Tatra kolem svìta - Tatra 815 GTC

Its in foreign gibberish though, but the photos are here: Tatra kolem svìta - Fotogalerie

 

[duncan]

Just to kill the time a little

 

[EZFEED]

Hey....same thing here. My tanks are eggshell thin as well and in some places you ca poke little holes in them. I wouldnt throw them away just yet though.

Do you have a tractor? How about a gravel road?
If so then take your tanks off, plug up the pickup hole up as best you can (do not leave the tube and block attached! They are soft copper!) a good way to do this is use a piece of cardboard over it and tape it down with duct tape. Also tape up the little holes in it already. Now open the filler cap and scoop in several handfulls of loose small gravel (best to find lime bean sized pieces, also be sure to put in plenty of the sand and broken little particles of rock that you can find) followed by about a gallon of muratic acid.

Ratchet strap or bungee cord that sucker to your tire and drive around slowly for an hour or so then flush out. That sucker will look CHROME LINED after you are done HAHAHAHA!
Also all of the bad spots will be found and you can epoxy/braze/or fiberglass over these.

Now if you wanna get fancy and add a little strength to it...find a decent fuel tank liner to follow up with after a thorough rinse. Any good radiator shop will have a sloshing compound. Dont worry here...you can actually use the cheap stuff for this. See with gasoline, if you use the cheap stuff it will sometimes flake off and plug the pickup. With diesel you can use the cheap stuff and not worry about it because its not harsh at all on it.
If you have a little patience these tanks are quite fixable but I agree they are woefully thin.
Making new tanks as you stated would be great too but a decent about of work over fixing the originals. Would be great to make some stainless ones

Yep injector work is easy! You should remove them and clean them thoroughly though before you do any serious driving because you could possibly damage the injector nozzles by running them dirty. I drew some pics for you and notes using some of the illustrations from the big PV3S manual. I couldnt post them though because I dont know how to transfer from PDF to JPEG. I will scan them in from home later.

 

[duncan]

Hmmm, but even if coated, the tanks would be a weak spot. No access to a tractor of any kind either, such it city life. The only thing with tractor sized tires it the truck itself.

Stainless is too expensive. I did look into using 4mm aluminium to save on weight, but it'd mainly save weight in my wallet just like stainless. Proper steel is the way to go, just dont leave the tanks empty for a long time. Either way if the original flimsy tanks survived 35 years of outside in the rain without maintenance, then surely some heavy new onles will last me a lifetime!

I got a pic of the drivers manual page on the cleaning of injectors, but I cant seem to move it to the PC. Will fix that later!

 

[John C]

I agree completely Re. injectors, on the old Zetor tractors we own which as I've said before use the same injection equipment as the Tatra/Praga (PAL), the injectors are a fairly regular service item, they will run for years and years without them even being touched but the engine will start to run a bit roughly and dirty unless they're serviced once in a while. The only hard part about the process is finding an injector test pump/gauge, I made my own out of an old Bryce injection pump which are used on old single cylinder Peter/Lister engines, then I just got a pressure gauge fixed in-line for setting the injector pressure. The other good thing about them is tips are quite cheap if you do need new ones - saying that the 813 is going to need twelve of them if you decided to treat it to a full set, which would still cost a reasonable amount.

Re. Fuel tanks. You might be best getting an alloy one off some other wagon at a scrapyard - would think it should be cheaper and you won't have to worry about corrosion again.

Regards.

 

[duncan]

Right, just a little update from abroad then. Tried to get the old cab's diesel heater to work, but failed. I have no clue how its supposed to work, but theres a glow plug of some sort, 2 electrical fans, and a bunch of wires. The dashboard has a key-switch with 4 positions (Off,1,2,3), and a push button for glowing. The old wiring has been messed with so cant trace it.

So far Ive found a ground wire, 2 wires that run motors (one for the exhaust, one for the blower), and a thick wire that makes the glow unit heat up massively.
Then theres 3 others. One seems to trigger some kind of magnetic valve in the fuel line. One makes both electrical fans run slower, sounds like it might be shorting the thing. The last one connects with the thick glower wire somewhere halfway the system. Im lost

I cleaned the filters, replaced the circuit breaker (twice) just to be sure, but cant get it to start. Help would be much appreciated.

 

[cranetruck]

How is the flow of fuel controlled? It is possible that the fan(s) run at a slower rate during the ignition phase.

I have spent a considerable amount of time on the American (Stewart Warner and Benmar) heaters and would be interested in more info on the construction of yours.

The fuel rate on the above mentioned units is in the neighborhood of 15 to 20 cc/min.

 

[duncan]

Well the fuel is gravity-fed from a tank mounted behind the cab. It goes through the filter into a unit that looks like a magnetic valve. From there the fuel line disappears in the inside of the unit.

 

[cranetruck]

Well the fuel is gravity-fed from a tank mounted behind the cab.......

Simplicity rules.

I have spotted this "Channel lock" type tool several times in your images...I like it, looks like the jaws stay parallel at all times. What brand is it? I have an antique version of non-locking parallel jaws pliers that come in handy now and then made by Sargent & Co.

 

[cranetruck]

Found this on the all knowing web. It may or may not apply, no picture to go with the instructions.