Grouser vents on M4A3s.

[Bullbasket]

My understanding (I could be wrong) is that M4A3s didn't have grouser vents, but when Israel converted a number of M4A3 (76mm) into M51s, they appear to have them fitted. My question is, did they fit them at the same time as the engine change from Ford GAA V8 to R975 radial? Why did they need them?

TIA.

 

John.

[Kingsman]

You are correct that M4A3s were not factory-fitted with the grouser cover vents. Nor were M4A2s.  The only late-hull type to have them was the M4(105), of which IDF acquired a fair few in the early days.

 

I've just re-looked at the Gannon book and the welded M51 pictured on p294 does indeed have the vents whereas the welded M1s pictured earlier do not.  I had never noticed this.

 

I might offer 3 suggestions.  First, the Cummins conversion did indeed need them: but why?  Second, the A3-based M1s were re-fitted with the Continental radial somewhere between the photos, although Gannon suggests they arrived in Israel already converted and without the vents.  The factory radial engine setup needed the vents.  Third - and possibly most likely - is that what appears to be an M4A3 could in fact be a hybrid 76mm turret on an M4(105) hull.  Picture 544 in Gannon's book on p307 is postulated to be such a vehicle.  It is not the same one as picture 518, which Gannon also suggests began life as a 105mm tank.  As the M4A3(76), M4A3(105) and M4(105) were all built concurrently by Chrysler, telling them apart by hull alone is very difficult without seeing the engine deck or hull rear, especially after IDF had played about with them and changed those areas and other potential identifying features like travel locks and ranging stake stowage.

Edited November 6, 2020 by Das Abteilung
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[Bullbasket]

10 hours ago, Das Abteilung said:

especially after IDF had played about with them and changed those areas and other potential identifying features like travel locks and ranging stake stowage.

And with that, I think that you have it in a nutshell. A lot of identification features are missing or altered, thereby making it difficult, but thanks for your thoughts Peter on the subject. I appreciate them.

 

John.  

[Kingsman]

Yes, well we happy / sad / obsessed [delete as appropriate!] bunch who like IDF Shermans need to pool our understanding of this complex subject.

 

I've come to understand 3 things about the subject. 1 - Pareto's Rule applies: the last 20% of research will take 80% of the time.  2 - Sherlock Holmes' (alleged) Rule applies: remove the impossible and whatever is left must be the truth, however unlikely.  3 - tearing your hair out with the fiddly stowage bits is obligatory!  Don't get me started on jerrycan racks......

 

The liquid-cooled M4 engines didn't need the vent covers as the fuel tank cooling problem affected the air-cooled radial.  But, strangely, that was only discovered on M4s despite several thousand earlier radial-engined M3s with an essentially identical engine bay setup.  I suspect that the pepperpot exhaust setup under the rear overhang corners may have masked the problem and that it only became apparent with the revised central exhaust setup.  And the M3 didn't have the grouser compartment to vent anyway.  That being said, the M4A4 did need them - even with its massive radiator.  I guess 5 straight sixes in a box got a little warm........  So you only find them factory-fit on M4, M4A1 and M4A4.  I believe that most if not all M4A2s had the apertures with blanking plates, probably for parts commonality, but M4A3s never had them.

 

There was a cooling airflow problem with the Cummins installation, most notably with the cast hull.  Many of these were fitted with the "airflow extension" of the upper rear hull overhang.  IIRC the longer-hulled M4A4 did not suffer this problem, and of course did not need the lower hull extension either.  M4, M4A2 and M4A3 hulls do not seem to have been fitted with a similar extension, so there is perhaps a plausible line of thought for fitting the grouser compartment vents on A2 and A3 hulls with Cummins engines - noting that A3s would need the apertures cut out.  But I don't know of any definite evidence for this.  Their presence seems to be more incidental than deliberate.

[Bullbasket]

I think that it's a given that Shermans in the service of the IDF, are a minefield. I used to have Military Modelling, way back in the 70s, and even then there were arguments raging in it's pages. If I remember correctly, the good Doctor had a very public disagreement with a well known modeller and writer (whose name escapes me) over how various M51s should be designated. Another well known modeller modeller and military historian stated that M51s were never built on anything other that cast hulls. And don't even get me started about the name "Isherman".

 

John.

[Kingsman]

Just leafing through Gannon again looking for something else.

 

He mentions elsewhere in the M50 section the appearance of the vents on converted M4A2 hulls.  But photo 433 on p248 shows the M4A4-based M50 that used to belong to Budge.  The right vent cover is missing and in the aperture is a section of ribbed tubing.  This is not original as that space was just an empty compartment to store the track grousers.  Now, the tubing could just be randomly stood in the empty space.  But it could also indicate that the vents did indeed have a purpose in the Cummins conversion.  But what?  The engine breathers came in through the fighting compartment firewall as per standard M4s.  Any air intake would need a filter somewhere.  The APU was on the opposite side. Too big for a crankcase breather.  Oil cooler would need forced airflow.

 

[Kingsman]

Just spotted an image on Sherman Minutia on the French Transforme page in the context of the M4A4T radial engine conversion.  Not seen it before.  It shows the airflow purpose of the vents to provide cooling air over the fuel tank tops.  If the same tank setup was retained - and there isn't anywhere else for them to go except in the sponsons - then presumably the same problem might have occurred with the Cummins V8.

 

But the fuel tank problem was with soldered joints failing (whyever weren't they welded?) and as part of the Cummins conversion new stainless steel tanks were fitted.  You might think that the problem had therefore been resolved.

 

For some reason I can't link the image itself, but here's the page.

http://the.shadock.free.fr/sherman_minutia/m4a4t/transforme_tanks.html

 

Interesting why the M4A2 did not have them: did the twin-6 GM6046 really run that much cooler?  But they were quite low engines - certainly lower than the radial and multibank - and perhaps there was enough airflow circulation above it anyway.

Edited November 16, 2020 by Das Abteilung
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