phylo_roadking Posted November 19, 2013 Share Posted November 19, 2013 (edited) All - between myself, Tom O'Brien and a number of members at HMVF, we've managed to produce a VERY good timeline for the legendary problems the Austin K5 "Screamer" 4x4 suffered in 21st Army Group hands beginning in September 1944...until its resolution with new-specification piston rings in December. The BRIEF version is that the famous problems the K5 came to suffer....very accelerated piston ring wear, leading to burnt and contaminated oil; very worn valve guides and bent/damaged valves, and heavy carbon/burnt oil desposits in the combustion chamber...ALL arose from a combination of the following; 1/ a new piston fitted to the K5s prepared for "wading" in May '44; these had increased clearance for the piston skirt because (possibly) of an earlier overheating issue - which led to the pistons "rocking" and the rings wearing far too fast - in turn because... 2/ Austins used old-spec rectangular-edged piston rings on these new pistons, and they gave marginal sealing; certainly not enough to prevent accelerated wear and oil contamination, or cope with the pistons rocking; 3/ There was very fast valve guide wear, leading to BOTH oil in the combustion chamber and badly damaged valves - both because of the contaminted, heavily graphited oil AND because of local overheating - the latter possibly because of... 4/ The changeover to 80 octane "MT 80 Pool" iin service just before D-Day....which was KNOWN to cause local overheating and hotspots in some older engines, particularly ones designed to run on a lower octane rating fuel - and finally... 5/ that new, increased-clearance piston fitted in May? It very possibly led to problems with the new, low viscosity "HD30" high-detergent oil grade that had come into common use , along with other HD grades, in late 1942; this oil had prviously given no problems - but the new pistons and fast wearing rings meant that the oil film wasn't being scraped off the cylinder walls properly - leading to oil drag, increased wear in turn AND burnt oil due ti blow-by on the worn rings. The whole problem - after various attempts to find other cures - was put right at the start of December by the fitment of a new specification of piston ring that would fit in the existing, increased-clearance pistons; these rings, in a much harder grade of cast iron alloy that was a patented product of Wellworthy's, the piston ring specialists....had a tapered edge for better support of the "rocking" piston and of course wouldn't wear anything like as fast. Both the compression rings AND the oil scraper ring was revised - and because of the taper they were "one-sided" they could only be fitted one way up - and THAT side was marked...."HD30"!!! And thus the famous problem was resolved - or at least the Director of Mechanical Engineering at the War Office thought so! Obviously...any overheating due to the MT 80 could be coped with once all the piston ring wear and dirty/burnt oil issues were removed from the equation. BUT HERE'S THE PROBLEM... In May, 1,400 K5s were "recalled" and fitted with those new pistons at Austins; these lorries had ALREADY been waterproofed and issued to assault companies....and REME had to waterproof them AGAIN! So this particular activity - the fitting of the new pistons LESS THAN A MONTH BEFORE OVERLORD - must have been a rapid reaction to some OTHER problem!!! And given that it was "solved" by increasing the piston skirt clearance to allow for more thermal expansion - this problem must ALSO have been something to do with overheating... So my question is very simple - is anyone aware of, or ever heard of, problems with the Austin K5 4x4 BEFORE D-Day? Edited November 19, 2013 by phylo_roadking Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted November 19, 2013 Share Posted November 19, 2013 And given that it was "solved" by increasing the piston skirt clearance to allow for more thermal expansion - this problem must ALSO have been something to do with overheating... Hi Phylo, Good assumptions, but something I should point out. The increased piston clearance for the K5's destined to possibly having to wade was not because of overheating, in fact quite the reverse. When on the landing craft prior to disembarking the engines would be run up to ensure they are warm and running well, as soon as they were immersed the water would instantly bring the cylinder block temperature down, yet the pistons would retain a certain amount of heat at that moment and with normal clearance would tend to seize, this is why more clearance was given. Nothing to do with allowing the piston to expand more, it was the block contracting that was the concern. This problem may well have come to light in the weeks before D-Day with all the wading practise going on across the country with the vehicles. regards, Richard Quote Link to comment Share on other sites More sharing options...
phylo_roadking Posted November 19, 2013 Author Share Posted November 19, 2013 Hi Richard - that certainly makes sense! Are you aware of anywhere where this particular aspect of the problem was recorded? Or possibly - when K5s were first waterproofed for training prior to D-Day? Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted November 19, 2013 Share Posted November 19, 2013 Hi Richard - that certainly makes sense! Are you aware of anywhere where this particular aspect of the problem was recorded? Or possibly - when K5s were first waterproofed for training prior to D-Day? Hi Phylo, I have been wading back through your other thread on this subject, and no where can I see that some of these K5 were partly prepared for wading on production. They were fitted with a special waterproof Clayton Dewandre vacuum brake servo and also in the workshop manual the references I gave you regarding pistons with extra clearance. Another thing I should point out is that these engines have cast iron pistons and normally run a tighter skirt clearance than engines with alloy pistons. I am quite familiar with these old Austin engines, hence my interest. I cannot pin point batches but a wild guess here is this, the REME report where they tested a particular K5, its census number was L5192471, now that was part of Contract No. S2552, numbering 2,030 K5's. It has to be assumed this was the problem batch. I think these vehicles were built at the factory with the extra clearance on the pistons as it is written in the manual, they probably performed well in immersion testing, but the oil consumption problems only came to light when they started using them on the road. The waterproofing of electrics, engine, ignition, etc would have been done prior to embarking, this was in general an army task. regards, Richard Quote Link to comment Share on other sites More sharing options...
phylo_roadking Posted November 20, 2013 Author Share Posted November 20, 2013 (edited) Hi Richard... and no where can I see that some of these K5 were partly prepared for wading on production. No, what I meant is that from the comment from December... According to the War Office D.M.E. progress report for period ending 3.12.44, "new and interchangeable piston rings of improved material and design should be incorporated into production now, and fitted to the 3,000 vehicles at present frozen in V.R.Ds". ....and... Further to the article appearing on page 98, Volume 8, of this Journal, the engines of 4x2 vehicles first fitted with the modified compression and scraper rings, part numbers 1K1420 and 1K1421 respectively, are as follows:- 2-Ton W.D. Ambulances, engine no. 75090, during Contract S.3165 2-Ton (4x2) R.A.F. vehicles, engine no. 71804, during Contract S.6566 ...do those mean that from May on Austins were using the increased-clearance pistons for ALL K5 production??? Even vehicles that would never see any wading? If they didn't have the increased-clearance piston, they wouldn't need the new rings - the OLD spec K5 engines had been fine for several years! :-) Until the seizure-on-wading problem had materialised... EDIT: Just had a minor Eureka! moment :-D Surely we should be able to tell this from the manuals??? There should be one single part number for pistons for both GS K5s....and all K5 variants...from May 1944 on??? And this should be different from the piston part number from BEFORE May 1944 :-) Edited November 20, 2013 by phylo_roadking Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted November 20, 2013 Share Posted November 20, 2013 Hi Richard... No, what I meant is that from the comment from December... ....and... ...do those mean that from May on Austins were using the increased-clearance pistons for ALL K5 production??? Even vehicles that would never see any wading? If they didn't have the increased-clearance piston, they wouldn't need the new rings - the OLD spec K5 engines had been fine for several years! :-) Until the seizure-on-wading problem had materialised... EDIT: Just had a minor Eureka! moment :-D Surely we should be able to tell this from the manuals??? There should be one single part number for pistons for both GS K5s....and all K5 variants...from May 1944 on??? And this should be different from the piston part number from BEFORE May 1944 :-) Hi Phylo, I think you are confusing yourself here, and I should point out that referring to engine spec changes in 2 ton ambulances or trucks only muddies the water. They had the 3.5 litre engine, bore sizes different, no link, never heard of them being built for wading. Just to elaborate on my last post, there were two types of brake servo shown in the 1946 workshop manual, the conventional Clayton and a special waterproofed version, different construction, that along with the details in the book re. piston skirt clearances, it looks as though there were a particular batch of K5 built to sustain wading. As I have come across another forum with this subject on it, Axis? I see there has been a lot more said, but a lot of misleading info from people who appear to know little about this particular vehicle. Interesting discussion though, especially all the info being found in archives. cheers Richard Quote Link to comment Share on other sites More sharing options...
phylo_roadking Posted November 21, 2013 Author Share Posted November 21, 2013 (edited) I think you are confusing yourself here, and I should point out that referring to engine spec changes in 2 ton ambulances or trucks only muddies the water. They had the 3.5 litre engine, bore sizes different, no link, never heard of them being built for wading. Richard, here's what I mean; Tom has since been back to the "big" D.M.E. file and found THIS regarding the pre D-Day issue... ....13th Meeting of DME W/P Committee for 5 May 1944 which I found in WO229/76/0/1: 3. Austin 3 ton 4 x 4 and 3 ton 6 x 4 DME made a statement with reference to the re-working of the engines of these vehicles which had failed owing to engine trouble due to inadequate piston clearance, on large-scale trials at No.1 M.T.C. WEYMOUTH. Austin Motor Company is re-working all engines required for vehicles for Assault Force, and the vehicles should be completed by 17 May 1944... Reserve vehicles of these types are not having their engines re-worked as the defect is only experienced when wading. Now - that WOULD indeed make it look as of only one set of vehicles, those for the assault companies, were intended to be waterproofed for wading...to wade...and need the increased-clearance pistons, as you say... ...but some time AFTER that something at Austins seem to have changed... A representative of D.M.E. attended a meeting between T.T.2, C.I.E.M.E. and the Manufacturers on 8.11.44. The manufacturers offered new and completely interchangeable piston rings, both for new production and re-working of "frozen" stocks of new vehicles. Tapered Compression rings (2 off) in D.T.D. 485. Scraper rings (1 off) in D.T.D.233. Tests on three vehicles fitted with these rings show satisfactory oil consumption and a steadily rising m.p.g. at 2,500 miles. It was agreed that in view of the satisfactory preliminary results and complete interchangability of rings, the new rings could be introduced into production as soon as supplies are available. It was also agreed that if the test results continued to be satisfactory after 5,000 miles re-working of the "frozen" bank of vehicles with the new rings might commence. According to the War Office D.M.E. progress report for period ending 3.12.44, "new and interchangeable piston rings of improved material and design should be incorporated into production now, and fitted to the 3,000 vehicles at present frozen in V.R.Ds". ...the engines of 4x2 vehicles first fitted with the modified compression and scraper rings, part numbers 1K1420 and 1K1421 respectively, are as follows:- 2-Ton W.D. Ambulances, engine no. 75090, during Contract S.3165 2-Ton (4x2) R.A.F. vehicles, engine no. 71804, during Contract S.6566 ...and the NEW Wellworthy rings in DTD 485 and DTD 233 were going to be out into NEW 6-clyinder engines on Austin vehicles on the production line. So do we read that as Austins fitting the new-spec rings (or the War Office WANTING them to!) to vehicles that weren't intended for wading and didn't have the New "May" spec increased-clearance piston...and didn't need them..."are not having their engines re-workedas the defect is only experienced when wading"...and had been running happily on HD30 for some two years... OR... In the interim....SINCE May and the resolution of that earlier problem... had Austins at some point settled on a single piston specification - the increased-clearance one...for ALL their K5/K6 engines? I hope that explains better what I'm trying to find out Edited November 21, 2013 by phylo_roadking Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted November 21, 2013 Share Posted November 21, 2013 Hi Phylo, Firstly from the Workshop Manual for the K5, and to quote " piston skirt fitting has been increased from .0025"-.0028" to .004"-.0045" to make engines with new pistons immediately suitable for wading through water without fear of siezure. Pistons with the original smaller clearance can be used for engines which it is known will not be called on for wading". OK, I first interpreted that as only those vehicles with waterproof servos having the increased clearance as they might have been the one specially set aside for wading. There is a contract of K5's which just have the word "Water" after the vehicle type, I am certain these were not water tankers and can only think that these were the ones prepared as above. There appears to be 500 lorries in that contract. Reading the manual again and it is dated 1946, so after the event, and after final production so it might indicate if vehicles were being prepared for water, then this is the data. Just to confuse things further, I have a document, Inspection Standards (Provisional) for the Austin K6 6x4, issued by REME Central Inspectorate. Handwritten on the cover are the words "Comments by 26 Feb 1955". In there is some interesting wordings and bear in mind this is 10 years later; "Pistons must be selectively fitted to obtain clearance. Feeler gauge applied to thrust side of the piston skirt, tight .0045" and loose .004" will suffice for practical purposes. When assembled and on test, piston slap will be apparent and is permissible" The clearances mention are the increased ones stated for wading, so maybe they set all the 4 litres up this way, in case of the eventuality. Further on in the engine testing data there is a another mention; "NOTE: Due to increased piston to bore clearance piston slap will be apparent and is permissible." I have more thoughts on all this but will have to find time later on to relate them. regards, Richard Quote Link to comment Share on other sites More sharing options...
phylo_roadking Posted November 21, 2013 Author Share Posted November 21, 2013 Hi Richard - THIS is particularly intersting... Firstly from the Workshop Manual for the K5, and to quote " piston skirt fitting has been increased from .0025"-.0028" to .004"-.0045" to make engines with new pistons immediately suitable for wading through water without fear of siezure. Pistons with the original smaller clearance can be used for engines which it is known will not be called on for wading". OK, I first interpreted that as only those vehicles with waterproof servos having the increased clearance as they might have been the one specially set aside for wading. There is a contract of K5's which just have the word "Water" after the vehicle type, I am certain these were not water tankers and can only think that these were the ones prepared as above. There appears to be 500 lorries in that contract. Reading the manual again and it is dated 1946, so after the event, and after final production so it might indicate if vehicles were being prepared for water, then this is the data. Does that mean there was a contract of 500 with the increased-clearance pistons in them straight of the production line...in addition to the 1,400 that were modified for wading with the new pistons in May '44? Just to confuse things further, I have a document, Inspection Standards (Provisional) for the Austin K6 6x4, issued by REME Central Inspectorate. Handwritten on the cover are the words "Comments by 26 Feb 1955". In there is some interesting wordings and bear in mind this is 10 years later; "Pistons must be selectively fitted to obtain clearance. Feeler gauge applied to thrust side of the piston skirt, tight .0045" and loose .004" will suffice for practical purposes. When assembled and on test, piston slap will be apparent and is permissible" The clearances mention are the increased ones stated for wading, so maybe they set all the 4 litres up this way, in case of the eventuality. Further on in the engine testing data there is a another mention; "NOTE: Due to increased piston to bore clearance piston slap will be apparent and is permissible." Looks like the new pistons in Wellworthy's proprietary cast iron alloy grades provided a longterm cure then! Piston slap, yes...but no accelerated wear Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted November 21, 2013 Share Posted November 21, 2013 Hi Richard - THIS is particularly intersting... Does that mean there was a contract of 500 with the increased-clearance pistons in them straight of the production line...in addition to the 1,400 that were modified for wading with the new pistons in May '44 Phylo, Before getting too positive on this, I would suggest checking the Contract out, the details are here; L4892640 - 4893194 Austin 3 ton 4x4, Water Contract no. V5093 You could contact the Tank Museum as they hold a lot of these cards which have delivery dates on them. There were actually 555 lorries in that contract. I am certain the word 'Water' was meant to indicate water proofing, but it does not mean to say that the pistons had greater clearance, at that time. At least it is a possible clue. I cannot date the contract and they were often delivered up to a year later than when the contract was signed. regards, Richard Quote Link to comment Share on other sites More sharing options...
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