Wednesday 10 May 2017

Hellcat Mobility Trials

" Table #5

Speed in kph
Braking distance in m
Time to brake in sec
8
0.5
0.6
16
3.4
1.4
24
7.65
2.8
32
14.4
5.7
40
30.1
9.4

When driving at 50 kph, the SPG drifts to the side when brakes are suddenly applied. When the brakes are applied gradually the SPG does not drift, but the braking distance is very long (70-80 meters).

4. Mobility data

a. Average movement speed

Table #6 shows the average movement speed of the SPG

Road conditions
Distance traveled
Average speed in kph
Movement speed
Overall speed
Cobblestone highway
172
38.4
38.4
Paved highway
116
47.6
47.6
Dirt road
430
23.8
23.8
Cross-country over snow
117
19.4
19.4
The table shows that the movement speed is equal to overall speed, which indicates that the SPG is reliable.

The highway speed is limited by poor stability of the SPG, especially when driving on a highway covered in iced-over snow. At high speeds (50-60 kph) the SPG drifts to the side.

Driving along the dirt road was mostly done in second gear. Driving in third gear is limited by insufficient drive torque provided by torque converter. 

Driving in the snow was done in first gear. In second gear, the torque drops significantly due to slipping of the torque converter. The movement speed drops to less than the speed in first gear at the same engine RPM.

b. Fuel and oil consumption

Data on fuel and oil consumption in various road conditions is summarized in table #7.

Road conditions
Engine work hours
Consumption per one hour of work in Liters
Consumption per 100 km of travel in Liters
Fuel
Oil
Fuel
Oil
Highway
9 h 45 min
78.5
1.61
203
4.17
Dirt road
17 h 45 min
80.5
2.64
357
11.3
Cross-country
5 h 50 min
130.7
3.95
708
20.2

The table shows that the fuel consumption is significantly higher than the established norms for vehicles of this class.

The increased fuel consumption is explained by the uneconomical engine and insufficient drive torque provided by the torque converter.

5. Off-road performance and obstacle negotiation

a. Driving on dirt roads and off road

The trials established that:
  1. The SPG has insufficient traction with the ground. Because of this, the vehicle is unstable on packed and icy roads. 10-12 degree slopes can only be negotiated in second gear after a running start.
  2. Driving along a dirt road with deep holes and loose soil is impossible due to insufficient torque from the torque converter.
  3. The SPG cannot cross roadside ditches covered in snow that are deeper than 0.75 meters due to insufficient torque from the torque converter.
    It is possible to drive off-road if the snow is no more than 0.5 meters deep. The SPG cannot drive through snow more than 0.5 meters deep due to insufficient torque from the torque converter.
Photo #19. Driving the SPG along a smashed forest road.


3 comments:

  1. Good info, but why is this russian information? Didn't the americans test their own tanks anymore, or is that info not available anymore?

    dtic.mill is currently the site for anything from the US millitary that has been declassified, but a lot of it has been blanked out...

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    Replies
    1. They did, I imagine, but all vehicles offered through Lend Lease were tested in the USSR as well before ordering a large batch. I wasn't able to find anything on the Hellcat in DTIC at all, the stuff that's scanned is only a tiny part of what's available in their physical archives.

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  2. So Hellcat in War Thunder was historically accurate when it first came out. It had sooo bad acceleration with low rpms and rarely you could use third gear because it would just bog down. Too bad they changed it to "normal" 5 speed transmission, probably too many players complained about it. Personally I liked it, it gave the Hellcat some character and uniqueness :)

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