Thursday, 31 July 2014

Tiger II Trials: Mobility

At Ogledow, the Soviets captured a number of Tiger II tanks perfectly intact. One of the tanks was shot to bits, but another got to live. It was run through trials to see how well this mysterious new vehicle performed. This article will cover mobility trials, with gunnery trials in another article.

"Mobility Trials

According to the speedometer, the tank already travelled 444 kilometers. The following trials took place:
  1. Gunnery trials
  2. Mobility trials
Special trials could not be carried out due to the tank breaking down prematurely. During mobility trials, the tank travelled 113 km over dirt roads with many potholes and slopes up to 10 degrees. The roads were dry.

The tank was fuelled with KB-70 gasoline. The engine and transmission were filled with aircraft oil, and the suspension was lubricated with solid grease.
...

Results of mobility trials

Average speed:
A dry stretch of road 35 km long was used to determine average speed. The following was determined:
  1. Average speed in motion: 13.4 kph
  2. Total average speed: 11.2 kph
The tank moved mostly in fifth gear, on short flat stretches of road it could move in sixth or seventh gear. The significant difference in speeds was caused by an oil leak of the right fan, which required constant stopping to inspect and refill it.

Fuel consumption:
As a result of trials, it was determined that fuel consumption on a dirt road is as follows:
  1. For 100 km: 971 Liters
  2. For 1 hour of running the engine: 130 Liters
The tank has enough fuel to drive 90 km on a dirt road. The German instructions claim that fuel consumption for 100 km should be 700 Liters. The increased fuel consumption observed during trials is caused by a worn engine.

Engine temperature:
Figure 7 shows the graph of water temperature and oil pressure.

Figure 7: Graph of water temperature [top] and oil pressure [bottom. Time scale is in minutes, oil pressure is in kg/cm^2, water temperature is in degrees Celsius]

From the graphs, it can be seen that:
  1. The water temperature does not pass 95 degrees and stabilizes slowly.
  2. The oil pressure stabilizes quickly and holds within 6-7 kg/cm^2
Turning speed:
The turning trials were done on a grass plain with a hard clay surface. Trials showed that the planetary turning mechanism lets the tank turn well. The tank can turn in neutral gear. The following table contains data characterizing the tank's agility.

Gear
Time to turn
Engine RPM
Turning radius (meters)
Right
Left
Neutral
1:10
2200
2.2
2.25
1st
1:10
2100
4.3
-
1:15
2000
-
4.15
2nd
1:00
1700
5.9
-
1:01
1700
-
6.15
3rd
1:12
1700
8.75
-
1:05
1700
-
9.2
4th
1:15
1600
14.95
-
1:20
1600
-
12.10
5th
1:05
1800
25.8
-
1:35
2000
-
18.2
6th
2:00
1400
51.2
-
1:15
1500
-
33.2

It was not possible to determine the turning radius in 7th and 8th gears, as the previous turns destroyed two track links and 12 track pins. Due to brittleness, the track pins fall apart into several pieces.

Reliability

After capturing the tank, it drove 110 km on its own to the railroad station. The driving occurred over the following terrain:
  • Stone highway: 60 km
  • Asphalt highway: 10 km
  • Dirt road: 25 km
  • Sand road: 15 km
During this march, the following breakdowns occurred:
  1. The ball bearing of the left idler was destroyed.
  2. The right engine group overheated.
  3. The gearbox was overheating due to insufficient cooling and external air temperature over 30 degrees.
  4. A large amount of track pins were destroyed, especially when making frequent and wide turns.
  5. The tracks become loose quickly and have to be tightened every 10-15 kilometers.
After being offloaded at the proving ground station (the speedometer showed 444 km), the right final drive jammed. Upon opening the right final drive housing, it was discovered that it was completely destroyed. The reason for this was not discovered. It was replaced with the final drive from another Tiger B.

After the conclusion of mobility trials, upon disassembly and inspection of the final drives, it was discovered that the right final drive was once again broken (the roller bearing of the drive bar was completely destroyed). Inspection of the final drives shows that their drive bar bearing design is unreliable.

During mobility trials, the following breakdowns occurred:

  1. At the 86th kilometer (530 km on the speedometer), the left drive wheel broke. All of the bolts holding the external gear rim broke. Two teeth of the external gear rim and one in the internal were broken (see fig. 8).

    Figure 8: Destruction of the gear rims of the drive wheel.
  2. On the 103rd kilometer of trials (547 km on the speedometer), the left drive wheel was once again destroyed, and the torsion bar of the front left road wheel was destroyed. All bolts holding the gear rim were destroyed, and the gear rim itself snapped in two.
The cause of the destruction of the gear rim bolts in the first case was that the balancer of the front left road wheel was bent, as a result, the road wheel was not in the same plane as the rest, and was somewhat tilted compared to the rest. The small spaces between the road wheels led to the road wheel striking the ends of the bolts when it hit an obstacle, cutting off the bolts one by one. The teeth broke due to incorrectly engaging the track after being improperly attached to the drive wheel and being worn significantly. 

The cause of the second breakdown was the destruction of the torsion bar of the left front drive wheel. After the torsion bar was destroyed, the wheel, having no rigid connection and being tilted at will, cut off the bolts of the gear rim.

Having analyzed the causes of the breakdowns during trials, it can be concluded that the Tiger B's weakest components are its final drives, drive wheels, and track pins."
CAMD RF 38-11355-2860

2 comments:

  1. Hello

    Great work, this is probably one of the most famous Soviet documents. Is there any specific reason for using aircraft oil? is it because it is suitable for petrol engines?

    ReplyDelete