Tanks heavy-v-speed

[Khaki]

I understand that tanks were evolving quickly, and credit is due to those whose imagination and technical skills put them in the field considering all else that was going on, but what was the primary cause of their low speed (apart from the terrain), was it the gearing system/ weight or engine capabilities or was it all three combined. I am not a 'mechanically' inclined person so please keep the answer simple.

khaki

[centurion]

All the British WW1 tanks had significantly improved speeds when fitted, experimentally, with decent suspension (the Mk 1 - V* had no suspension nor did the Medium A which when fitted with springs could do about 17mph as opposed to about 7mph normally). The German A7V was faster than its British opponents for much the same reason. However in muddy shelled areas which was the tank's normal environment such suspensions very quickly became encrusted with mud and broke. As the original tanks were intended to be infantry support vehicles Tritton and Wilson decided that walking pace was sufficient and it would be better to have a slow tank that could keep moving rather than a fast one which could not. It also made for a simpler production (and therefore more tanks available)

A Mk IV was fitted with a proper suspension system and got into two digit mph figures but it would probably not have done well in WF conditions

[Chris_Baker]

A Mark IV tank weighed 26 tons. It was propelled by a single 106 Brake Horsepower engine. The power:weight ratio is principally what determines the dynamics of the tank. Only 4HP per ton! No wonder it struggled.

To put it in context, 106 BHP is just above half of the power of say, a Mercedes E250CDI, which weighs 1.7 tons.(I think these figure are about right, anyway, after a quick calc from the Mercedes website!).

Chris Baker

Former Operations Director

Large automotive braking systems manufacturer

And powertrain nerd, obviously.

[Gareth Davies]

I think Cent's point about suspension is really important and often overlooked. Even if they could have squeezed a few more horses out of Daimler and Ricardo's finest, the extra oomph would not have been able to be easily used.

As an aside, does anyone know the torque output of the engines?

[centurion]

The standard Mk V with the 150 Hp Ricardo could do no better than 4.7 mph under ideal conditions. A Mk V with the same engine but fitted with a Fowler sprung cable suspension achieved 12 mph As a Rolls Royce graduate trainee I am fully aware of the importance of engine size but suspension did make a difference

Perhaps the ultimate was a Medium A with leaf sprung suspension and a Mk V engine and transmission that in 1918 did 30 mph - decent suspension and a bigger engine. Even the boy racer medium D only did 27mph. (and shed its tracks with monotonous regularity) As Gareth points out you need decent suspension to be able to use the extra power.

[centurion]

A Mark IV tank weighed 26 tons. It was propelled by a single 106 Brake Horsepower engine. The power:weight ratio is principally what determines the dynamics of the tank. Only 4HP per ton! No wonder it struggled.

To put it in context, 106 BHP is just above half of the power of say, a Mercedes E250CDI, which weighs 1.7 tons.(I think these figure are about right, anyway, after a quick calc from the Mercedes website!).

Chris Baker

Former Operations Director

Large automotive braking systems manufacturer

And powertrain nerd, obviously.

Those figures appear to be incorrect the Mk I and II which used the 105 Hp Daimler had an HP/ton of 3.4 (male) and 3.5 (female). The Mk IVs weighed 31 tons (male) and 30 tons female) and had a 125 hp Daimler and HP/ton of 4.0 (male) and 4.2 (female). Despite the improved power weight ratio the standard MK IV was no faster than the Mk I

[GRANVILLE]

Even if the early tanks could have been made to go considerably faster, could the poor chaps inside them have been able to cope with the conditions which were bad enough at 7mph?!

[Khaki]

Hopefully, fast enough to have avoided being an easy target for gunners etc,

khaki

[centurion]

Even if the early tanks could have been made to go considerably faster, could the poor chaps inside them have been able to cope with the conditions which were bad enough at 7mph?!

Well improved suspension would have helped, without it they'd have spent all their time just hanging on.

[chrislock]

Even if the early tanks could have been made to go considerably faster, could the poor chaps inside them have been able to cope with the conditions which were bad enough at 7mph?!

I agree with Granville.

As a former MBT AFV crewman I can assure you that a Main Battle Tank irrelevant of it's generation will always be restricted or enhanced by the quality, skill and experience of it's crew and especially that of the driver.

Power output, torque ratios, suspension etc of course are so important as us "Chieftain" cab rats knew only too well. Techno stuff will always only be one part of the complete story. Me? I would rather have a top notch commander, driver and crew any day over all the power and torque ratios Scotty could offer the bridge when the cloaking device had failed.

Driver advance.......

[centurion]

I

Power output, torque ratios, suspension etc of course are so important as us "Chieftain" cab rats knew only too well.

And as someone who got to review the maintenance stats at REME at the time can avow - the basic availability of those Chieftains which in terms of overhaul/engine change times etc were a disaster

[chrislock]

Totally agree and if linked with my personal experience, my observations remain in place.

[Chris_Baker]

Those figures appear to be incorrect

Quoted from "Tanks 1914-18: the log-book of a pioneer" by Sir Albert G Stern KBE CMG. Blame him! And he was there!

[centurion]

Quoted from "Tanks 1914-18: the log-book of a pioneer" by Sir Albert G Stern KBE CMG. Blame him! And he was there!

But not the most accurate writer I'm afraid but then he was a banker!

[MikB]

The German A7V was faster than its British opponents for much the same reason. However in muddy shelled areas which was the tank's normal environment such suspensions very quickly became encrusted with mud and broke.

The large nose and tail overhangs also severely limited the A7V's capability to tackle trenches and obstacles, and its high centre of gravity could cause it to topple sideways in a way not often (if ever) seen in British tanks - as in the first tank v tank action at Villers-Bretonneux.

Regards,

MikB

[centurion]

The large nose and tail overhangs also severely limited the A7V's capability to tackle trenches and obstacles, and its high centre of gravity could cause it to topple sideways in a way not often (if ever) seen in British tanks - as in the first tank v tank action at Villers-Bretonneux.

Regards,

MikB

Yes well known but on level ground they were faster because of the better suspension. The British rhomboid design was specifically chosen to give enhanced trench crossing and obstacle climbing capability which none of the tanks based on Holt suspension units (A7V Schnieder and St Chamond) had. A German attempt to combine the rhomboid design with Holt suspension (the A7VU) had to be abandoned because the Holt units were still too prone to clog with mud.. The truth is if you design an infantry tank capable of operating in a shelled area its going to be relatively slow. The best WW2 tank in terms of trench crossing and obstacle climbing was the Churchill which could traverse areas impassible to other Allied and Axis vehicles alike and it was also relatively slow (and shared the all round track design with the British WW1 tanks although it did have a suspension system)

[centurion]

And not being a technical person Stern possibly did not realise that whilst the engine in the MK IV was based on that in the Mk I power output was boosted by the use of an improved twin carb and aluminium pistons and it was run at higher revs.

[Beerhunter]

And as someone who got to review the maintenance stats at REME at the time can avow - the basic availability of those Chieftains which in terms of overhaul/engine change times etc were a disaster

I remember the track life of Chieftain was truly appaling and the so-called "pack change" a disaster area.

IIRC Challenger 1 corrected a lot of the engine problems by simply doubling the power.

Back to the topic. Another often overlooked part of an AFV is the transmission. It needs to be STRONG!