It can't be that horrible a little tank. It was the main component of the Panzer divisions that wercked France in 6 weeks.
Improved Early War British Tanks?
- Thread starter Paul_Sussex
- Start date
McPherson
Banned
Numbers. Not found is a 38t, but I can find this as a comparator.
i mean the PZ38T, even as a tank hunter variant, was tiny, cramped, and a horrible design even compared to a near contemporary and badly designed R35, which was about as effective in its assigned role. This is my opinion and YMMV and probably should.
Now compare the 38t tank hunter to its contemporary, the Archer.
Ad-hock the Archer is arguably better than the 38T tank-hunter.
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Hmmmmm...thought I'd finished here, but there's always one more little snippet of information to tease out.
Regarding tank engines and everybody's perennial favourite, the Rolls Royce Kestrel I'd always thought that Nuffield had an early license for the Liberty engine, but this -
- seems to indicate that this was actually only from early 1937.
At the time, Rolls Royce were still producing the Kestrel, already a mature design first run in 1926/7, but were putting more effort into the Goshawk/Peregrine and the new PV12 which would become the Merlin. Various other engines were being considered, so would it be ASB for Nuffield to go for a Kestrel license instead? The dimensions are comparable -
- and this would not rely on RR production. So, a derated version to run on pool petrol, a more up to date design and potentially fewer problems, unless Nuffield cock up the installation? But a longer A13 to accomodate the Kestrel, compared to the OTL version -
I've always been a little wary of Kestrel proposals, but if it can be done without using RR capacity...?
Edited to add - the Kestrel was making 630hp on 87 octane. Does anyone have an idea what this would drop to on pool petrol?
Regarding tank engines and everybody's perennial favourite, the Rolls Royce Kestrel I'd always thought that Nuffield had an early license for the Liberty engine, but this -
- seems to indicate that this was actually only from early 1937.
At the time, Rolls Royce were still producing the Kestrel, already a mature design first run in 1926/7, but were putting more effort into the Goshawk/Peregrine and the new PV12 which would become the Merlin. Various other engines were being considered, so would it be ASB for Nuffield to go for a Kestrel license instead? The dimensions are comparable -
- and this would not rely on RR production. So, a derated version to run on pool petrol, a more up to date design and potentially fewer problems, unless Nuffield cock up the installation? But a longer A13 to accomodate the Kestrel, compared to the OTL version -
I've always been a little wary of Kestrel proposals, but if it can be done without using RR capacity...?
Edited to add - the Kestrel was making 630hp on 87 octane. Does anyone have an idea what this would drop to on pool petrol?
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Might as well have a five wheel design with that length; much more even distribution of weight.
Yes - the A13 was just a quick cut and paste. But in effect a slightly longer Crusader would do the same thing. But then a longer A13 could look like this?
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A Merlin was installed in a Crusader with very little modification to the engine bay so that trials could take place. If you can fit a Merlin a Kestrel should be fine. A chunk of the extra length of the Kestrel over the Liberty would be the supercharger which is not necessary for a tank as they don't often fly at altitude.🤪
How much power at ground level do you loose taking the super charger off the Kestrel?
We have 2 flat 12s
The 12 cyclinder DAV engine of 300 BHP used in the Covenanter and the later 12 cyclinder "Twin 6" 350 HP used on the Churchill but I am not sure when this was developed.
These both present themselves as being more readily available for the early British Tank designs in that British industry was better able to develop and make them.
Now while the Twin 6 was barely powerful enough for the Churchill it would double the power in the late 30's designs such as any Cruiser or Matilda II setup.
While the Meteor is the obvious point of arrival and a Kestral equivalent is desirable for its power output I think its a push getting this for a 1939/40 tank
The 12 cyclinder DAV engine of 300 BHP used in the Covenanter and the later 12 cyclinder "Twin 6" 350 HP used on the Churchill but I am not sure when this was developed.
These both present themselves as being more readily available for the early British Tank designs in that British industry was better able to develop and make them.
Now while the Twin 6 was barely powerful enough for the Churchill it would double the power in the late 30's designs such as any Cruiser or Matilda II setup.
While the Meteor is the obvious point of arrival and a Kestral equivalent is desirable for its power output I think its a push getting this for a 1939/40 tank
marathag
Banned
Meteors ran at 550-600HP for the same displacement as the old Liberty, with no supercharger.
Kestrel is 1296ci. vs 1650, so straight calculations lead to 470 HP, and maybe a bit less, since the Merlin III the Meteor was based on, was a better design than Kestrel.
Many early supercharger were for normalizing, so that the engine would get Sea Level pressure at 10-15000 feet.
The Sherman Radial still had its supercharger, but ran at less boost, as it was needed for better fuel distribution to the cylinders, not for more power. More power means more heat, and the need for better cooling.
Make that 745 HP on 87 oct (+3.25 psi boost), for supercharged engines, late marques.
Unsupercharged - on 87 oct it made 610 HP at 2900 rpm, 520-560 HP onn 2500 rpm; also late marques.
Unsupercharged (mid-marques) - on 77 oct it made 530 HP at 2700 rpm, 480 HP at 2250 rpm (with full throtle for take off it was 546 HP).
The lowest figures for engines that still allow for 73 oct fuel it was still at least 480 HP on 2250 rpm.
What kind of octane rating was for the pool petrol anyway in second half of 1930s?
The unsupercharged Kestrels were with compression ratio of 7:1, vs. the supercharged Kestrels with CR of 6:1. Of course, there is no brain surgery to make unsupercharged Kestrels also share the 6:1 CR if the octane rating of the pool petrol demands it.
(note that, at least, the wartime Meteors were still sharing the 6:1 CR from Merlin )
Depends on what kind of gearing the existing S/C was using. At any rate, the drop in performance will be of about 50-150 HP.
Only thing I've found so far quotes a figure of 74 octane here - http://www.austin7.org/From the Past/From the Past 5/
So from the above, should be possible to derate to slightly more power than the Liberty, to allow for extra weight, and maintain reliability?
So from the above, should be possible to derate to slightly more power than the Liberty, to allow for extra weight, and maintain reliability?
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If you want decent reliability you're also going to have to make sure the cooling system is properly designed and avoid cock ups like having the air filters positioned in just the right place to pick the maximum amount of dust and grit thrown up by the tracks.
marathag
Banned
I've seen lower than that, mostly in the 65-67 range.
UK Ford engines were set at 4.6:1,that was good to 60 Octane. The older Model T was 4.2:1, and 45 for thats nearly Kerosene.
Ford of Germany had 5:1 compression, they had higher octane for road use.
US Army decided that vehicles would use 80 octane, and Jeeps and most Trucks had 6.5:1 compression. As far as I can tell, US shipped only 80 and higher to the UK after 1942.
EDIT
Austin Seven had 4.8:1 compression until 1936, when it was bumped up to 6:1, for a six HP increase.
Normally that would need 77 Octane.or so.
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McPherson
Banned
At traction, an astonishing 40%. Remember, watts is taken and measured at PTO for book, NOT at the drive sprocket.
60 Octane to 70 Octane depending on whether British or American refined. 65 is the historical average from 1922-1939.
Venezuelan source? A bit low. More like 70 Octane.
In either case, we'd probably want to have the tank-Kestrels with 6:1 CR - just in case.
So even if de-rated to 400 HP it will propel a 25-30 ton tank into a reasonable speed.