Posts Tagged: field trial report
Swedish impressions of the Sherman, part 2
Another report on the Swedish experiences with the Sherman. This is an earlier one, from 1947, and only covers the M4A2 and M4A4. It’s a lot terser than the first one, probably since was an internal report written for the 1946 armor committee by one of its members. The armor committees of the 1940’s were joint groups made up by people from both the Ordnance Administration and various army formations, including the armor school, tasked to figure out where armor technology was going and recommend appropriate responses to the higher-ups.
Without further ado, here’s the translation.
Supplement #1 to minutes of meeting held with the 1946 armor committee on June 16, 1947
Memorandum regarding experiences with tanks of type Sherman, M4A2 and M4A4
Steering gear
The differential steering offers very good performance on roads and on hard ground in terrain. On soft ground the downsides become apparent – the “differential effect” of the steering (translator’s note: it is not clear exactly what this refers to). There is no neutral steering nor any possibility to do a clutch-brake turn, which has turned out to be a noticeable downside since the turning radius is large. The steering levers are close to each other, so the driving position is comfortable.
(Translator’s note: The strv m/42 used a single radius geared steering system; pulling one steering level geared that track down by 2/3rds which produced a fixed turn radius of about 9 meters. However, you could also press a button on the steering level which clutched and braked the inner track completely and let you turn around a point about half a meter from the inner track.)
The steering gear has effective cooling and lubrication, and additionally the brake discs (TN: unsure about terminology here, the Swedish word used is literally “brake belts”) operate submerged in oil, so there is rarely any reason for adjustment. During a road march of about 150 km, the steering gear casing did become very hot to the touch, but the oil temperature never showed more than 110° F, while the maximum allowed is 160° F. There was no noticeable degradation of the performance of the steering gear; it was the same at the end of the march as it was at the start.
There is no parking handbrake nor any brake pedal, but the steering levers can be locked in the rear position. Hereby the extra devices needed for a dedicated braking system can be avoided.
Transmission
Easy to switch gears, effective synchronisation. Can be said to be on par with the transmission in the pvkv m/43. There is no overdrive. Separate oil coolers for the transmission and the steering gear.
Track assembly
Durable and effective, but vulnerable because the road wheels are mounted in pairs. The tanks move smoother and have a more even ride in terrain than Swedish tanks do. When driving on wet surfaces or in upslopes in terrain, the track with rubber pads shows tendencies to slip, which makes the steering not fully effective. Terrain driving performance and obstacle passing is otherwise about the same for the tank with the rubber padded track as it is for the tank with the steel track.
The steel tracks are heavy and make a considerable amount of clattering noise. They are likely to be more vulnerable than “skeleton tracks” (TN: it seems likely that by “skeleton tracks” the author is referring to track links with some sort of hole or gap in the link rather than ones that are completely solid). The arrangement of the guide horns in two rows on the outer sides of the road wheels is fit for its purpose, especially when driving in terrain. The design of the track links – whole links without holes – makes gravel and mud amass in the tracks when driving in difficult terrain and on loose soil.
Turret
The cast design causes certain unpleasant vibrations in the turret when driving. Since the tanks are tall, lurches and other movements are more noticeable than in Swedish tanks. These factors make the personnel show a certain reluctance to stand in the turret while driving in terrain.
Manual traverse is easy to handle because of the powerful gear ratio – 1/4 turn in 28 seconds (strv m/42 23 seconds). Power traverse by wheel turning (TN: no idea what is intended here, literal translation again) – 1/4 turn in 6 seconds, full rotation in 26 seconds. Power traverse with the control set at full power – 1/4 turn 4 seconds, full rotation 19 seconds (strv m/42 1/4 turn 7,5 seconds, full rotation 24 seconds).
The tank commander can power traverse the turret at full speed from his position in the cupola. The turret traverse braking is very effective – as soon as the traverse wheel stops turning, the turret also stops immediately. When power traversing, the turret automatically returns to the position it had when the wheel stopped turning. On the M4A2, the handle on the traverse wheel has a latch, which is pressed when traversing. When this latch is released, the turret is braked.
The turret design with a turret basket that the crew sits in is clearly superior to the strv m/42 (TN: which didn’t have one). The walls of the turret basket are made of perforated sheet metal, so you can see through them.
The gyroscopic stabilization affects the weapons and the telescopic sights, and seems to be effective and rugged.
The weapons are loaded from the left side of the gun – that is, with the right hand. Why is it not done like this in our tanks? It seems appropriate for the heavy rounds in question here.
The observation cupola is used as a ring mount for a 13 mm anti-aircraft machine gun.
Instrumentation
There is a tachometer, which is very important on these tanks since they don’t have a speed governor. The drivers quickly learn to switch gears based on the tachometer readings.
All instruments are electrically signalled, even the oil pressure. Signal lamps are used to a large extent, for example to indicate that the engine has the proper working temperature. The same gauge is in several cases used for different purposes, for example indication of oil and fuel amounts in various tanks – a switch is used to control which device is measured.
Automatic fuses are used consistently in the electrical systems. They are placed easily visible on the instrument panel.
Internal equipment
There’s plenty of room for ammunition – 96 7,5 cm rounds, 300 13 mm, 6750 7,65 mm – and for equipment. The connection plugs for the microtelephones (TN: intercom microphones or entire headsets?) are worth copying. On the M4A4, the commander can stop the engine from his position.
At the rear of the tank, there’s a box with connectors for external telephone lines to the tank commander as well as for connecting an extension cord. There’s also a call buzzer button that alerts the tank commander here.
There’s a separate auxiliary generator motor that charges the batteries and powers the turret traverse and radio while the main engine isn’t running.
There is a fan in the turret for venting smoke and fumes.
The swivel connector seems very effective and reliable.
The seats are practically designed with a spring loaded mounting, which makes adjusting the seat height easy.
The periscopes are made in two parts, so only the top part needs to be replaced in case of a hit or other damage.
The antenna isolators are simple and robust, and are made entirely out of rubber.
In the engine compartment on the M4A2 there is a starter button for each engine, which is very useful during checkups or maintenance work.
External equipment
Stowage boxes for the crew’s personal equipment as well as for the tank’s equipment are mounted on the outside of the vehicle.
The refilling points for fuel, oil and water are clearly marked with text, covered by sturdy hatches and surrounded by a ring of armor. Large and sturdy design.
Service, etc
A large number of informative signs as well as the well illustrated manuals ease the service and maintenance of the tanks. The electrical system is practically designed and easily comprehensible, with cables gathered into a small number of runs that are connected in switch boxes. Plug-type connectors are provided for the devices that are intended to be removable, such as the engine.
On the M4A2, removing and replacing the engine takes roughly the same time as on the pvkv m/43. On the M4A4, only about half this time is required, since most devices remain attached to the engine when it is lifted out of the tank.
The general impression of the tank is good. It is easy to drive, practically designed and durable. There have been no problems with training conscripts on the tank and its various systems. Few repairs have been necessary.
Hans Malmgren
Major
Stridsvagn 103 trials in the US, 1975-1976
Two strv 103’s were sent to the US for trials in 1975-1976. Seven US crews were trained and the tanks were subjected to a variety of tests, in which they were compared to a variety of odd vehicles, ranging from the mundane M60A1 AOS (add-on stabilizer) to a T-62, an RVT-2 (a West German experimental vehicle with 1800(!) horsepower – see the comments section for more information) and an XM808 TB (8-wheeled Lockheed experimental vehicle). The report from these trials is over a thousand pages long, but I have only managed to find a small part. I’m working with the national archives to get the entire thing declassified, but it’s been met with some bureaucratic issues due to the US classification levels.
Nevertheless, I’ve obtained a few summary pages that in themselves contain a number of interesting tidbits. For example, did you know that when comparing gun laying times against a stationary target from the short halt, the strv 103B was faster to fire (although somewhat less accurate) than the M60A1 AOS? In the stationary vs stationary case on the other hand, the strv 103 layed slower but hit better. When averaging about 400 fired rounds of various types in a variety of situations against a variety of targets at different ranges between 500 and 2000 meters, the strv 103 hit an average of 77% of shots and took an average of 13.1 seconds to open fire, while the M60A1 AOS hit an average of 72% and took an average of 12.7 seconds to open fire (it should be noted here that the M60 was using its coincidence rangefinder, while the strv 103 had no rangefinder at all). In a mixed driving trial, the strv 103 was slightly faster than the M60 but accelerates slower.
You can read the fragments in PDF form here – and for once, they’re mostly in English.
Report from terrain trials with T-80U
In late 1993, following the de-escalation after the end of the Cold War, the Swedish army borrowed two Russian T-80U’s and subjected them to a number of trials. Unfortunately, they arrived too late to compete directly with the M1A1, Leclerc and Leopard 2, which had been tested earlier as a part of the procurement of a new MBT for the Swedish army. In the end, the Leopard 2A5 with some Swedish modifications was chosen and entered service as the Strv 122 – you can read more about the procurement process and trials on Rickard O. Lindström’s excellent page. Most of the test results are still classified, but a friend got a report and some video tapes from the T-80U terrain trials declassified recently. The report originally contained comparison values with the Leopard 2 and the M1A1, but unfortunately those were blacked out by the national archives before they agreed to release the report to the public. Russian secrets are not as secret in this country as American and German secrets are.
The videos from these trials are available on YouTube (note that this report only covers the autumn trials, not the winter ones):
Part 1 (autumn 1993)
Part 2 (winter 1994)
Read the entire report as PDF (34 MB)
Some translated quotes from the report:
Summary
With 26 hp/tonne, the T-80U drives and accelerates very well in general. The difference in engine power between the T-80U and strv 104 (re-engined Centurion, nominal top speed 50km/h) is very noticeable on surfaces with some resistance, such as grassland or plowed fields. The T-80U is generally twice as fast as the strv 104 on these surfaces.
The suspension is good and allows high speeds over terrain without much discomfort for the crew.
Despite the antiquated steering system, with a good driver the tank does well in rough terrain, mostly thanks to its high engine power and good visibility for the driver.
Driving in rough terrain or narrow passages in the dark is considerably more difficult, mostly because the driver’s night vision periscope has a very limited field of view.
The tank has a very low reverse speed, which – among other things – limits its tactical options in prepared fighting positions.
The T-80U also does well with various obstacles such as steep slopes, trenches and road banks. The performance is however limited by the lack of self-cleaning tracks, which makes it tend to lose traction.
Re-positioning between prepared positions
If the re-positioning only involves driving forwards, the T-80U performs on par with modern western tanks. If reversing is involved, the T-80U is slower because of its low reverse speed.
In daylight, both the tank commander and the driver have good visibility forwards. When reversing, the commander has some problems with his visibility backwards since equipment on the turret are in the way.
When reversing in darkness, the tank commander has to turn the turret to the 6 o’clock position in order to get night vision so he can direct the driver.
Driving in difficult terrain
In daylight
T-80U average speed: 19.3 km/h
T-80U fuel consumption 201 liters/10 km
Strv 104 average speed: 14.4 km/hIn darkness
The same track as in the daylight trial was attempted, using the driver’s combined vision port (active IR and image intensifier). The trial was aborted after the tank had driven 300 meters in 60 minutes. Leopard 2 and M1A1 both have night vision devices well suited to this kind of driving.Summary
When driving in daylight, the T-80U could maintain a relatively high speed. The driver’s visibility, the engine power and the steering system are all good enough for this kind of driving.Driving in darkness, however, is very problematic. The driver’s field of view is so narrow he cannot see the tank’s corners. Since the turret has to be put in the 6 o’clock position to avoid damage to the gun, the tank commander cannot help him either.
Fuel consumption when driving in this type of terrain is very high.
Vertical obstacles
With the splash guard fasteners removed (20 minutes of work), the tank climbs a 1 meter tall vertical obstacle without any trouble. Without removing them, the tallest climbable obstacle is 0.8 meters.
Steep slopes
The tank does well up to a slope of about 25 degrees. The engine power is sufficient and if the surface is dry the track traction is good.
Top speed
On pavement, forward: 70.3 km/h
On pavement, backward: 11.3 km/h
On a grass field: 49.8 km/h
On a plowed field: 37.7 km/h
Slalom driving
Since every gear on the T-80U has a fixed turn radius, the tank has to be driven on the lowest gear to be able to make the tight turns, and it gets a result on par with the strv 104 despite being capable of much higher speeds.
The driver has some difficulties seeing when he’s past an obstacle; the commander has to direct him.
Time to prepare for fording
Depths up to 1.8 meters: 5 minutes
Depths exceeding 1.8 meters: 30 minutesIt is quick and easy to prepare for shallow fordings (up to 1.8 m).
Reports in French on the Swedish trials of the AMX 13
Various reports in French from the Swedish trials of the AMX 13. These are just translations of the corresponding Swedish reports, but I thought they’d be more interesting to French people than to Swedish people, so the French version it is.
Archive reference: SE/KrA/0062/D/01/016:H/F I, various volumes from 1952