8110 - Seeking for answers

After the photo coverage of the Unimog building process few days ago, several mistakes have been reported and some new doubts/questions were raised by AFOLs, who carefully studied these photos.

First issue concerns with the way the L4 engine gets connected to the main drive shaft. Common sense says it should connect to the central differential, instead of any other of differentials in the front and rear axles. However the photos available doesn't explain how is it accomplished. Furthermore it is shown a misleading central 3L diff (62821), while a few indicia tell us, the older 4L diff (6573) should be used in its place.
Allan Porter (Allanp) was the first to point at EB the possible evidence for the mistake, and Menno Gorter edited the photo to cut the building instructions where we can find a notice, warning the users that the old diff should be used, instead of the new one.

Another discussion has been around the pneumatic pump cylinder. Despite it being released in a new color (LBG), some also observed that it looks a bit longer than usual...
The fact is that pneumatic pumps used in official LEGO Technic sets, like 8868 (Air Tech Claw Rig) and 8049 (Tractor with Log Loader), use the Small Pump (x191c01) in combination with a Technic Engine Crankshaft (2853) in order to achieve a 1L displacement. Despite this pump cylinder is capable of a 2L displacement, it doesn't fit within a linear setup over a Technic beam as we can see from the photo below, where Menno Gorter also tries illustrate this limitation.

In order to achieve a 2L displacement (double stroke) and optimal pump efficiency, some other arrangements might be used, like a bent liftarm (6-4) or even some old school studmore designs. However such arrangements wouldn't fit properly in the Unimog and would also require more space available. That's probably the reason why the LEGO Technic Designers may have developed a new pump cylinder, half stud longer.
Optimal use of the pump cylinder maximum displacement, is very important for a faster and smoother operation of the pneumatic cylinders on the crane arm.
If the former 1L displacement pump solution was already a bit under-performant on the 8049, with a third cylinder on the arm, it could become a disaster for the Unimog... if one tries to actuate several of the pneumatic switch levers simultaneously, or at a fast pace.


And the Unimog different new parts amount, increases again to eight:

• Pneumatic nozzle (PPTO)
• 6L mini-pump cylinder
• Torque tube (outer joint)
• Torque tube (inner joint) - This one comes attached to a kind of C-frame
• Portal axle gearbox
• Steering hub (new design to fit with the new portal gearbox)
• 9.5L shock absorber (Extra stiff)
• New tire (94,3 x 38R)

Finally another issue that raised also some interest. As stated in a previous post, it wouldn't make any sense to develop all new parts like the gearbox hubs, for the portal axles, if we won't have one way to drive movement to the wheels. It happens that existing similar previous steering hubs [1, 2] doesn't provide any mean to accomplish such function, what raises the doubt whether the new part allows to do it, or not!?

My opinion was that it should somehow provide an axle connection, inside the hollow that also exists in the previous parts.
This time it was Gerard and later Menno, who decided to take the quest to find evidence of it. Some searching, a little of Photoshop and that's it... An axle hole at the end of the hollow!

Another doubt solved!