813 kolos

[Eastblock]

Is the one from Excalibur? It does look at bit rough in the pictures.

[paulob1]

they got a load of them I think from Mortar investments, and they are not great...been sitting about for a long time...I thought they had some newish stock but they don't...

[Luke]

that is a clever design, but it doesn't look to be a 'free' diff, it looks like a perminantly locked one to me :? do tatras have a selectable diff lock or are they perminantly locked?

Luke

[FridgeF]

I think the diff is actually longitudinal, but yes they have a full set of difflocks electro-pneumatically operated from two switches on the dash, one for the rear, one for the front. If they didn't have diffs they would be pretty hard to get round a corner :shock:

[Luke]

I think the diff is actually longitudinal, but yes they have a full set of difflocks electro-pneumatically operated from two switches on the dash, one for the rear, one for the front. If they didn't have diffs they would be pretty hard to get round a corner :shock:

thats what I was thinking! I imagine it would have handling characteristics of a pregnant whale especially on the road. I can't fathem how that diff works though, there just aren't any spider gears :? so how could it work unlocked?

Luke

[Abrs]

It uses elliptical gearing and is located in the tube ahead of the crown wheel/pinion housing, the diff can be locked simply with a toothed ring slid into the assembly locking it so both pinions/crown wheels turn at the same speed, the inter-axle diffs operate in the same manner.

[paulob1]

still means I don't have one yet...and it is YET.

[FridgeF]

Having paid off the credit card I'm also tentatively on the look out again

[Abrs]

Some more tech pictures and a nice little vid showing the operation of the half axle design.

[youtube]http://www.youtube.com/watch?v=CRAqzv-bHS0[/youtube]

Differential arrangement:


Gearbox: (later type - 22 bearing constant mesh)


Nothing complicated there really :mrgreen:

[Luke]

ever so clever really, nice video on you tube....but, looking at that diagram,

the differential is between each 'axle' (i use the term loosly) rather than between the wheels on the same axle, I can only assume that with the hub reduction drive there is enough backlash in the gears, or even.... because it is so long, it might not even need an inter wheel diff,

Luke

[paulob1]

lovely...I will never pay off my credit cards, I have too many and they give me too much credit so i use it all the time. Mind you my plan is to be free of them by mid year...unless I have to buy three more trucks..tatra star and new 4320

[FridgeF]

ever so clever really, nice video on you tube....but, looking at that diagram,
the differential is between each 'axle' (i use the term loosly) rather than between the wheels on the same axle, I can only assume that with the hub reduction drive there is enough backlash in the gears, or even.... because it is so long, it might not even need an inter wheel diff,

Luke

Luke, I think you're missing something - the differential unit is in the yellow part and drives the blue/pink parts accordingly, being locked together by the inter-axle difflock which is the green part. The service manual lists both cross-axle diffs and inter-axle diffs.

[paulob1]

so the orange part ıs the ınteraxle dıff....whıch has a green bıt whıch then can be locked to the next ın lıne paır...

so asumıng these are all ındıvıdually controllable could you could start wıth front wheel drıve then workback untıl you have 8 wheel drıve and vıce-versa...

Or does ıt go ın a set pattern ıe rear ınner set fırst then rear set and or rear front paır then the front paır....ıf ıts vıa a tube central shaft that seems logıcal...

[Luke]

I see! your right I had missed that blue pinion has the pink bit running inside it at a different rate.....I thought they were fixed! do'h!

another question....... when its a through diff for an intermediate axle, which side drives the next set, it looks like the pink drives it through, but i'd have thought it would need a seperate locked shaft to carry on the drive, that way..... (another bit of lateral thinking) if the pink sided of the diff wheel was stuck and it put all the power to the blue diff side wheel, the power wouldn't be transmitted to the axles after this one, so applying that logic.... I'd have thought if you put your foot on the loud pedal it would spin up the first 'blue' wheel on the drive train rather than powering the entire drive system,

if you see what I mean!

Luke

P.s. I'm sorry I'm pestering with all these questions

[FridgeF]

The locker switches lock one end of the truck (front 4 / back 4) so maybe that helps explain things?

[paulob1]

so its 4 wheel or eight wheel drive with dif locks on each axle and between each set of four wheels but not between the pair of wheels, is that right...it means that each pair of wheels can rotate on one shaft (relative) when the other wheels are driving...hmm its not as good as I thought...this must reduce the effort exerted...if its right?

[paulob1]

hmm no I guess the rear two and the front two are locked together by not having a diff between them..a la zil and ural...ah now i understand...i think...am i right you guys who know?

[FridgeF]

I think, to save having seven separate switches on the dash, they gang the lockers together so you can lock the back end and/or the front end with a single switch.

Basically, everything has a differential and everything has a locker as far as I can tell.

That means, in reality you have the potential for it to be one-wheel-drive (fully unlocked) or 8-wheel-drive (all locked) or a load of other combinations.

I will stress that this is what I believe to be the case from deduction, looking at the manuals, a couple of test drives, talking to owners, and YouTube ;)

The last guy who we visited (who also has an 815) pointed out that the Tatra is rare in having a full set of lockers, as the temptation amongst the inexperienced (AKA squaddies) is to just lock everything and plant it - which of course breaks things, especially in front axles. The MAN KAT trucks for example do not have front lockers at all to make them more "squaddie proof", if you check some of the truck trial / rally videos on YouTube you'll see them make more of a meal of things than Tatras and other old-school stuff (made before common sense was outlawed).

[Abrs]

Ok, this is a little tricky to put into words :? , but basically each axle diff operates as a normal open diff when not locked, in the diagram it looks as if the two pinion gears are attached to the same shaft, however this is not the case, the pinion nearest the differential is only sleeved onto this pinion shaft and can turn independently of it, this shaft itself only turns the pinion furthest from the differential, however another main drive shaft is hidden inside this outer pinion shaft, it's this internal shaft which caries drive to the planetary geared axle differential via one of the three inter-axle differentials (torque dividers) unless it's the diff closest to the torque divider, in which case the toque divider is bolted directly to the axle diff. With all diff locks off this system can allow the largest proportion of drive to be sent to any one wheel (although this is unlikely) - whichever one is easiest to turn or is turning the fastest, this helps prevent the drive-train from being subjected to wind-up which would otherwise be encountered during turns or going over rough ground.

If that makes any sense :lol:

[Luke]

:mrgreen: It all makes sense now, Its nice to know how things work