Found the attached on the old Tanks! website. A US Mark IV SPG - looks like a St Chamond SPG with the US 240mm howitzer fitted. According to the text the gun vehicle had its own motor/generator that could move it around at low speed on good ground. Apparently tested at Aberdeen in 1920/21. Anyone know anything more about this vehicle?
Regards,
Charlie
-- Edited by CharlieC on Tuesday 29th of May 2012 09:32:16 AM
It's in Kosar's book on heavy guns, along with the US Mk III 240mm SPG. If you can translate the attached, you're in a better position than I am.
EDIT: Here's what Babelfish makes of the relevant text:
From co-operation with France however still another further type of attempt developed. On the chassis of St Chamond with its two gasoline-electrically propelled vehicles put the Americans on instead of the 280-mm-Mörsers the 240-mm-Haubitze. After the French model they maintained thereby the double-return using the inclined level and the roles of the upper carriage. Only the ammunition supply changed by mounting of a lateral projectile crane. The length rose to 9,3 m and the height even on 3,96 m on. With the ground pressure 104 kPa (1.06 kg/cm2) were measured. However one inserted with 110 KW (150 HP) stronger engine to one. In this form that received Vehicle the designation 240 mm of self-propelled gun carriage Mk IV.
So it sounds like it was basically a conventional St Chamond vehicle but with a more powerful engine (150hp instead of, IIRC, 120hp) and a new shell-crane. How accurate that is I cannot say, hopefully one of our French contributers will chip in with some more information.
-- Edited by Roger Todd on Tuesday 29th of May 2012 10:46:47 AM
I presume then that the ship's wheel on the side is for elevation then - I'd been stumped by those on the French machines.
Just to be pernickety, PS does not equate exactly to HP; 150 PS works out around 147 and three-quarter HP, or 147 and a half if you calculate from the KW. Not that it makes a difference
The German metric horsepower is a bit confusing to me; since 1HP is 746W, I'd have thought it would make sense to make the metric HP = 750W, but the Germans went the other way and chose a smaller value than 746
I presume then that the ship's wheel on the side is for elevation then - I'd been stumped by those on the French machines.
Aye, they were detachable. On a couple of high-quality photos in the B&M No74 article, you can see that the elevating mechanism used a square-section axle sticking out, so presumably they just slotted on and off for ease of use.
TinCanTadpole wrote:
Just to be pernickety, PS does not equate exactly to HP; 150 PS works out around 147 and three-quarter HP, or 147 and a half if you calculate from the KW. Not that it makes a difference
As far as I know the ship's wheel thing is to turn the gearing to pull the gun up the sloping ramp. For transport the gun was lowered to 0 deg. elevation and pulled up the ramp. The elevation wheel on the 280mm howitzer is just below the trunnions and probably is the same on the US 240mm howitzer.
The engine power isn't so important with these vehicles since they were petrol/electric - the 110 kW was a significant increase in power over the St Chamond SPG. The brief note in Tanks! says the max. speed was 9 mph (14 kph) which is a significant increase in speed over the 280mm howitzer St Chamond (5 - 7 kph).
The different crane is interesting - looks as if the Americans loaded the shells directly onto the loading platform of the howitzer and didn't use the charging trolley the 280mm St Chamond used.
I think the German text is saying that the Mark IV was only a prototype with only one vehicle being produced.
Certainly worth a mention as part of the St Chamond developments though.
As far as I know the ship's wheel thing is to turn the gearing to pull the gun up the sloping ramp. For transport the gun was lowered to 0 deg. elevation and pulled up the ramp. The elevation wheel on the 280mm howitzer is just below the trunnions and probably is the same on the US 240mm howitzer.
I bet the soldiers tasked with cranking the gun up the ramp wished that some of that electric power was used to do the job!
Interestingly, it says on the first page of the German article that the MkIII and IIIM1 had engines of 210PS and 225PS - rather more than the MkIV.
As for the text, I ran the caption for the photo through Google Translate (I tried Babelfish once but didn't like it) and it seems to confirm what the Babelfish translation Roger posted suggests, which is that it is basically a St Chamond chassis.
According to the data in Tanks! the Mark III weighed in 106,000 lb (48,180 kg)
the Mark IV at 71,000 lb (32,000kg). Not surprisingly the Mark III had more power but had a max. speed of 3.6 mph (5.8 kph).
The Mark III looks like it was built by Holt - there are similarities with the Mark I & II SPGs, also built by Holt. I note the radiator was mounted on the side of the vehicle with the driver opposite the fan - must have been really fun to drive in cold weather.
