Monday 12 May 2014

Lend Lease Impressions: M24 Chaffee


1. Armour.

The armour is insufficiently thick for modern requirements, as it does not protect even from anti-tank rifles and grenades. The front machinegun and removable hatch weaken the already insufficient armour further.

The hull shape is superior to that of previous American tanks (M3 light, M3 medium, M5A1), but is worse than modern domestic tanks.

Fig. 43: Hull and turret armour

The drawbacks of this shape include the insufficient turret armour angle and relatively large height. Advantages of the hull design include convenience of the hatch opening mechanisms and good visibility due to the commander's cupola.

2. Armament.

The 75 mm tank gun with a muzzle velocity of 610 m/s does not meet modern firepower requirements (penetrates 82 mm at 500 meters with the M-62 shell). Advantages of the armament include:
  1. Good accuracy and precision when firing from one spot, a high rate of fire of 9-10 RPM.
  2. Good accuracy when firing on the move at speeds up to 25 kph, due to the gyroscopic stabilizer.
  3. Good visibility and the commander's ability to control the turret increases mobility of fire and makes indicating new targets convenient.
  4. The compact recoil mechanism concentric with the barrel leaves a lot of room for the crew.
Drawbacks of the armament include:
  1. Poor optical sights, with a scale for only one type of shell.
  2. Leaking oil reservoirs of the recoil mechanism after prolonged firing.
  3. Only one turret rotation speed with the commander's controls reduces precision of aiming and makes pointing out targets difficult.
  4. It is hard to hold the periscopic observation device in place and the inconvenient location of the device in the commander's hatch makes it difficult to point at a new target and reduces mobility of fire.
  5. The front and AA machineguns lack sights, and make it difficult to provide effective fire.
3. Engine.

Two Cadillac engines provide satisfactory mobility to the tank. Scorching of the block pad is explained by poor tightening of the nuts, and is not a design flaw. Drawbacks of the engine include:
  1. High fuel quality requirements.
  2. The design is complicated, with many components and secondary systems, which require observation and maintenance.
  3. It is difficult to remove certain components such as fuel lines, starters, etc.
  4. It is impossible to discover an engine fault in motion, as the working engine will keep spinning the broken engine, and none of the instruments warn you of this.
4. Transmission.

The hydraulics, gearbox, demultiplexer, double differential and final drives work reliably. The M24 transmission has an advantage over the M5A1 transmission, as its engines are united into one power source.

The connection of the engines to the demultiplexer in the engine compartment, and not in the driver's compartment (like in the M5A1) introduces only one crankshaft instead of two, and makes the installation of the engine and transmission much easier.

The design of the gearbox makes it easier to detach each engine from the transmission. This design makes it difficult to drive the tank due to the nature of the mechanical demultiplexer. 

Advantages of the transmission include:
  1. Simplicity of controls.
  2. Reliability.
  3. Low maintenance requirements.
Drawbacks include difficulty in manufacturing.

5. Suspension.

The suspension worked reliably, with the exception of a rubber tire that fell off a road wheel. The torsion bars and shock absorbers work reliably and make for a smooth and highly dampened suspension.

Drawbacks of the suspension design include the track pins. The two pins and two holes on the tracks deform during use, and make disassembling and assembling tracks very difficult.

Controlling the tank:

The tank can be controlled from the seat of the mechanic-driver or his assistant. The hydraulic gearbox makes it so that the gears have to be changed rarely, and the driver mostly uses the accelerator and brake levers. This system makes it easy to drive the tank and reduces the level of training required for the driver.

During trials, there was only one case where the demultiplexer became misadjusted due to a lengthening of the parallel pulling. The adjustment mechanism is easy to access and readjusting it was not difficult. Otherwise, the mechanisms worked reliably. Signal lamps that indicate low pressure or high temperatures in the engine and gearbox make it easy to avoid problems. A drawback of the instrument panel is a lack of an oil manometer. 

Usage statistics:
  1. Average speed:
    1. Highway: 30 kph
    2. Dirt road: 17.5 kph
      These are worse than the speed of the M5A1, but better than the SU-76, and are satisfactory.
  2. Maximum speed:
    1. Highway: 55 kph
      With the effective hp/ton of 12.2, this is good.
  3. Average gasoline consumption per 100 km:
    1. Dirt road: 300 L
    2. Highway: 203 L
      This is high. The oil consumption is negligible.
  4. Off road performance is good.
  5. Range on dirt roads is 160 km. For this vehicle class, that is not enough.
  6. The amount of maintenance required is about the same as on tanks with a regular mechanical transmission, and can be done by the crew.
  7. The fuel used was B-70 with an addition of one cubic centimeter of R-9 per one liter of gasoline. This mix allows the engine to develop maximum power without deteriorations and breakdowns.
  8. Lubricating oil was used for the engine. It works well with this type of oil.
  9. MK oil was used for the differential and demultiplexer. Use lubricating oil in the winter.
  10. The fluid in the hydraulics was the American [illegible]-10 at all times of the year. A substitute was not used.
As the result of trials of the American light M24 tank, it was established that:
  1. The tank does not meet modern requirements.
  2. The following elements are interesting for domestic tank design:
    1. Recoil mechanisms.
    2. Ease and simplicity of driving the tank."


  1. Still, a much better tank than the T-70.

  2. Lol everything I read from these reports sound so "Better than"
    Fact is USSR had tons of crap. The way they paint the M18 was just funny seeing as it was much better than anything they had.
    Also as said the T-70 was way less than the Chaffee....So what light did they consider to have "Good Armor" or was "Good Enough" in that year?


    2. Hey, hey, hey, you should talk about the M18 in its own post, and they were actually quite positive on the M18. It has an accurate gun, a good rate of fire and is still pretty fast (the loss of ~25km/h of highway speed presumably had to do with the Russians sticking the petrol they'd actually use in).