Unserviceable Lorries - Jul - Sep 44

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Re: Unserviceable Lorries - Jul - Sep 44

#286

Post by phylo_roadking » 16 Nov 2013, 20:14

....THIS; Tom...
This vehicle had been fitted with new standard pistons and rings. It was also fitted with two re-built exhaust valves, one modified Bedford exhaust valve and three re-faced standard Austin exhaust valves.

The vehicle was driven over normal roads, including two fairly steep gradients. For the first 300 miles the performance was good. The first sign of roughness occurred at 350 miles and this grew steadily worse until, at 480 miles, two cylinders began to miss badly. At the conclusion of the run, reasonable compression could be felt on all six cylinders.

Engine oil pressure was 48 lbs per sq. in. at 30 m.p.h. with an engine temperature of 160° F at the commencement of the test. This dropped to 40 lbs per sq. in. at the same temperature and speed after 150 miles and then remained consistently at this figure throughout the remainder of the test.

On completion of the test the cylinder head was removed for examination. It was at once apparent that heavy oil burning had been taking place. The combustion chambers of Nos 3 and 4 cylinders had a heavy deposit of carbonised oil and the sparking plugs were heavily oiled. There was an appreciable hard carbon deposit on all other cylinders.

All inlet valves were in good condition but the exhaust valve heads were distorted in all cases, and there were signs of pitting. One of the built-up valves was showing definite signs of leakage. There was excessive oil present on the guides of Nos. 3 and 4 valves.
...this reads to be a test of a number of possible workrounds that REME in Normandy came up with to deal with the valve/top end aspects of the issue.

But it was a failure :P It looks as if none of the kludges held up to the rigours of the test...and they had tested them in the face of the worst deeds of the culprit -"this vehicle had been fitted with new standard pistons and rings". And the piston/ring problem beat the best efforts of REME with what they had at their disposal in France :P

So...the affected vehicles REMAINED "at present frozen in V.R.Ds" until the end of the testing period on "..3.12.44..." - when "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 "test period" itself had lasted from some time before the 8th of November 1944...
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 intercahngeable 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.


....to the 3rd of December 1944.

And THAT was the official end of the Austin K5 problem in Normandy, as far as the Director of Mechanical Engineering at the War Office was concerned...having found a cure that involved "new and interchangeable piston rings of improved material and design".

Less blowby to contaminate the HD30 oil...which could therefore carry on being used; as could the "standard" (standard that is for the "assault" K5s) increased-clearance "wading" pistons. No contaminated, heavily-graphited "dirty" oil circulating around the engine creating high wear rates in the top end. No coking up of the valves or the combustion chamber, no oiled-up plugs.

And just to square the circle on the above - I doubt there is much coincidence to the fact that there were 1,400 Austin K5s in "wading" kit provided for issue before the start of June '44 to assault GT companies for D-Day according to other details that Tom found....and 1,400 Austin K5s in Normandy affected by problems of faulty parts and accelerated wear three months later; some with as little as 2,000 miles on "new" engines.

It's also worth noting that Tom had also discovered and recorded on the lorry thread on ww2talk that 1,400 K5s were pulled and prepared for issue to the assault companies in May '44...by Austins themselves...I wonder if THIS was when the increased-clearance "wading" pistons were fitted??? :idea:

Finally - the issue of the change to MT 80. We know from various locations and histories that this change on the eve of OVERLORD did cause problems...and that litany of valve problems on the REME "test" K5 does mention two symptoms of overheating/poor cooling of the valves - the pitting of the valve faces and the "definite signs of leakage" I.E. the valves not dsealing on their seats. It's a bit "chicken and egg" whether the SECOND of these would be down to the valves burning OR the valves rocking around due to the guide wear :wink: ....but pitting on the valve faces would be a sign of overheating/poor cooling all right...

One of the British Army veterans on ww2talk confirmed that the Austin manual for these engines (in 1946 at least!) DID contain instructions for advancing for retarding the ignition timing to match the fuel used...so as a problem this one was easily dealt with. But it IS interesting that Austins (and I presume the War Office!) thought it essential to fit "wading" pistons with increased piston skirt clearance to deal with extra thermal expansion A MONTH before D-Day! 8O THAT is definitely "last minute" stuff!!!

So - one set of problems brought on/complemented the other??? Need for increased piston skirt clearance due to overheating in waterproofed engines -> fast bore/ring wear 'cos the new pistons used the old design/grade of rings -> high oil consumption AND carbon blowback contaminating engine oil -> worn valve guides...which are ALSO going to be hit by overheating issues anyway because of the MT 80...

It's worth noting that from everything I've read, and comments from several members on ww2talk - that while altering the timing on internal combustion engines to prevent pre-detonation etc. with higher-octane fuels is one action that's necessary...it doesn't ACTUALLY make the engine run any cooler! THAT is a problem that an engine still has to cope with....or in the case of the K5, exhibit overheating valve issues as well as worn valve guide issues.

However, looking at that final closure of the book on the K5 problem as of 3/12/44 by the War Office - I think we have to assume that the overheating issues brought on by MT80 were "officially" thought to be by far the lesser issue involved compared to the damage done by the fast-wearing piston/rings issue. Once THAT was addressed, the K5s could handle a little overheating...??? :lol: :lol: :lol:




(I put that last caveat in there, because the K5 doesn't seem to have had that long a career in the British Army after the war, it seems to have vanished out of khaki toot sweet! The K6, with the same engine but lower compression and lower power output had a MUCH longer Cold War career in many and various uses and is still favoured by restorers today...maybe it ran cooler? :P :lol: )
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Re: Unserviceable Lorries - Jul - Sep 44

#287

Post by Tom from Cornwall » 17 Nov 2013, 21:42

Phylo,

Thanks for all that... :) It will take me some time to process though.

I think I might have to look at the later dates as well - maybe Dec 44 throught to say March 45 to see if the flow of Austins started up again.

Regards

Tom


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Re: Unserviceable Lorries - Jul - Sep 44

#288

Post by phylo_roadking » 17 Nov 2013, 22:15

Part of the problem has been us all contributing to a number of threads at once; It was only on checking today that I noticed there was no mention on here of Wellworthy's "consulative" role in developing the new piston ring spec for Austin's, for example :wink: THAT was something you and I turned up on ww2talk...

And the importance of the D.M.E. meeting and the other, October meeting accounts didn't fully hit home until I put everything in date order and the relevance of the "test period" for the new rings, and its coming to an end early in December, became obvious...

In effect we really DID see the resolution of the problem first! But because of how the rest appeared in dribs and drabs, and some of the HMVF-supplied details turned up very "late in the day", so to speak...which NEITHER of us was ever going to find out on our own!...the "big picture" was like one of those objectionable jigsaw puzzles where you MAY indeed have the picture on the box....but ALL the "edge bits" are the same colour! :lol:

It took a lot of cutting and pasting into a Wordpad document over an evening to realise we really DID have an end-to-end account!

In the meantime - how is this relevant to Rich's concerns? Well -

It reveals that everything recorded in the 21st AG Admin History from the middle of September to the middle of December...good and bad...occured with up to "3,000 vehicles frozen in V.R.Ds"!!!

Looking again at all the above - it struck me that your post on ww2talk about one GT company having its faulty K5s replaced by Bedford OYs didn't appear here; thus we DO have proof that the shortfall created by the K5s was being made good from the reserve.

Something else I've noticed in the last few hours - somewhere between the middle of September and the 3/12/44 - the problem actually GREW from 1,400 K5s to 3,000 in V.R.Ds!

I think we've missed....or just not been looking!...that Austin K5s were STILL coming out of the factory in the problem spec when the issues arose at the end of the summer! In other words - as well as the 1,400 "wading" K5s specifically converted in May, the WO D.M.E. meeting account confirms that NEW K5s on the production lines would have to get the new-spec piston rings I.E. whatever number of them was built new THROUGH the summer was similarly affected!

This would go back a few months to the brief discussion on here you and I had regarding "new" B vehicles coming across by their hundreds each week and into the reserve, if you remember; I would guess that Austin K5s, complete with problem-spec piston rings, were streaming across the Channel along with every other make of truck!

And this would possibly be where the "extra" 1,600 Austins "frozen in V.R.Ds." come from ;) We don't have it specified by name, but as "new" vehicles were being taken out of the reserve and pressed into service, K5s must have CONTINUED going U/S for a time! I wonder - did the D.M.E. ever order the issuing of K5s halted until the problem was dientified/resolution found...?

The above comment has reminded me - putting everything in "time" order has allowed me to identify a few things we don't have yet - though they're not "needed", really. Here's an example...
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 intercahngeable 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.
We have no more detail on THOSE tests; who's idea they were, when it was decided on - was it another REME test in the field, or an Austin's project? It doesn't really matter, we know the results - but it provides a hint of what's been missing from the visible papertrail for decades ;) All that previous discussion. The stuff that should...should have been...somewhere but seems lost to posterity now.

As for this...
APPENDIX ‘A’

PERFORMANCE REPORT ON AUSTIN 3-TON 4 X 4 W.D. No. L/5192471
...similarly it shows what else must be missing now from the records/diaries/files at Kew now if a problem major enough to force REME into THAT sort of a test had indeed manifested itself. We should be seeing more sign of the problem than we are; again, it doesn't matter now, but it shows...as does Don Juan's Covenanter thread...how patchy the files really are 8O
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Re: Unserviceable Lorries - Jul - Sep 44

#289

Post by Don Juan » 17 Nov 2013, 22:34

phylo_roadking wrote: Less blowby to contaminate the HD30 oil...which could therefore carry on being used; as could the "standard" (standard that is for the "assault" K5s) increased-clearance "wading" pistons. No contaminated, heavily-graphited "dirty" oil circulating around the engine creating high wear rates in the top end. No coking up of the valves or the combustion chamber, no oiled-up plugs.

And just to square the circle on the above - I doubt there is much coincidence to the fact that there were 1,400 Austin K5s in "wading" kit provided for issue before the start of June '44 to assault GT companies for D-Day according to other details that Tom found....and 1,400 Austin K5s in Normandy affected by problems of faulty parts and accelerated wear three months later; some with as little as 2,000 miles on "new" engines.

It's also worth noting that Tom had also discovered and recorded on the lorry thread on ww2talk that 1,400 K5s were pulled and prepared for issue to the assault companies in May '44...by Austins themselves...I wonder if THIS was when the increased-clearance "wading" pistons were fitted??? :idea:
phylo_roadking wrote: So - one set of problems brought on/complemented the other??? Need for increased piston skirt clearance due to overheating in waterproofed engines -> fast bore/ring wear 'cos the new pistons used the old design/grade of rings -> high oil consumption AND carbon blowback contaminating engine oil -> worn valve guides...which are ALSO going to be hit by overheating issues anyway because of the MT 80...
Are you suggesting that the 1400 K5's that had the engine problems were built to the wading spec? And the wading spec had increased clearance (i.e. smaller diameter) pistons?

If so, the piston rings must have been a new design (at least a smaller inner and outer diameter design), even if they were made with the standard material. i.e. even if the REME described them as "standard" rings they weren't really - they were "specials".

So, if I'm interpreting your version of the history correctly, it seems that the K-5 had a design of piston and piston rings that operated satisfactorily up to early '44. Then, because K-5's were required to be able to wade, a new design of piston and piston rings was fitted in order to deal with anticipated higher engine temps. Then, when these wading (or "assault") K-5's were needed later on to supplement the MT pool, issues with blowby and other combustion problems emerged (due to lower loading in non-wading use), so a new set of piston rings had to be designed to fit the reduced-diameter pistons.

So we have:

Original design - standard pistons, standard piston rings
"Assault" design - reduced dia. pistons, reduced inner and outer dia. piston rings
Final design - reduced dia. pistons, reduced inner but standard outer dia. piston rings

If my above understanding is correct, then the material change on the final design might have been partly due to the rings simply being larger ("standard" outer dia. + reduced inner dia.) as much as changes in oil and fuel spec.
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Re: Unserviceable Lorries - Jul - Sep 44

#290

Post by phylo_roadking » 17 Nov 2013, 23:37

Are you suggesting that the 1400 K5's that had the engine problems were built to the wading spec? And the wading spec had increased clearance (i.e. smaller diameter) pistons?

If so, the piston rings must have been a new design (at least a smaller inner and outer diameter design), even if they were made with the standard material....
What we have is an increased-clearance piston....but piston rings that don't appear to have changed.
i.e. even if the REME described them as "standard" rings they weren't really - they were "specials"
Except that if Austin's were still fitting on new vehicles UNTILthe D.M.E. directive of the first week of December....they weren't "specials" they had become standard fitting at the factory for the K5.

SOMETHING must have happened in the early Spring to cause the urgent fitment of the increased-clearance piston in May to all K5s from that point forward...UNTIL that stops and the new-spec rings are ordered into place in December.
So, if I'm interpreting your version of the history correctly, it seems that the K-5 had a design of piston and piston rings that operated satisfactorily up to early '44.


Seems so; perhaps WHY we don't hear any problems on the K5 before then? OR something else happened around then that made the change to the increased clearance necessary...
Then, because K-5's were required to be able to wade, a new design of piston and piston rings was fitted in order to deal with anticipated higher engine temps.
As above - pistons but seemingly not rings. According to the HMVF manual information - AND a little detail buried in the minutes of one of the D.M.E. meetings - see below.
Then, when these wading (or "assault") K-5's were needed later on to supplement the MT pool, issues with blowby and other combustion problems emerged (due to lower loading in non-wading use),


It appears that the "first" 1,400 were kept in service...until their problems became SO bad in early September that they couldn't be ignored? But meanwhile "new" low-mileage K5s that were in the reserve in Normandy would have been being added to the MT pool...and THEY started accruing miles, and thus THEY TOO ended up forzen in VRDs by December?

Is that why the number of affected K5s went UP from 1,400 in September to 3,000 in December...?
...so a new set of piston rings had to be designed to fit the reduced-diameter pistons.

So we have:

Original design - standard pistons, standard piston rings
"Assault" design - reduced dia. pistons, reduced inner and outer dia. piston rings
Final design - reduced dia. pistons, reduced inner but standard outer dia. piston rings
There's nothing so far to say that the "assault specification"....that over the next few months became the standard production spec for the K5...included reduced inner and outer diameter piston RINGS. In fact, courtesy of HMVF and members there checking manuals for me, the actual DIMENSIONS of the rings didn't change.
If my above understanding is correct, then the material change on the final design might have been partly due to the rings simply being larger ("standard" outer dia. + reduced inner dia.) as much as changes in oil and fuel spec.
Except we have manual details from 1943 and 1945 that confirm there was NO change in the dimensions of the rings between those two years.
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 intercahngeable 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.
Note the above in bold - "completely interchangeable" I.E they'd fit into the same dimension slots on the existing pistons, and as we've seen there's no recorded change in the technical records of a dimension change.

This is where the work done on ww2talk comes in - "Tapered Compression rings (2 off) in D.T.D. 485. Scraper rings (1 off) in D.T.D.233"..."new and interchangeable piston rings of improved material and design"... Those seem to be two proprietary cast iron alloy grades used by Wellworthy; they were supplying rings in D.T.D 485 for Merlins by mid-war, according to their advertising blurb. It thus looks as if faced with a major issue Austin's consulted with an external piston ring specialist to find a cure - which they then passed on to the D.M.E..

For information - D.T.D. 485 was registered by Wellworthy as Patent No. 539,922 under the name "Lymalloy"; Wellworthy's factory was, as you can see from that advert, in Lymington...
Last edited by phylo_roadking on 18 Nov 2013, 00:19, edited 2 times in total.
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Re: Unserviceable Lorries - Jul - Sep 44

#291

Post by phylo_roadking » 17 Nov 2013, 23:54

Now - maybe it's my imagination - but look at this later advertisement for Wellworthy's products...Wellworthy disappeared in 1947, bought up by AE Pistons, along with Hepco and Brico. AE still exists today, as AE PLC....

Image

....is that a stylised Austin K5 GS? :lol: :lol: :lol:
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Re: Unserviceable Lorries - Jul - Sep 44

#292

Post by Don Juan » 18 Nov 2013, 00:19

phylo_roadking wrote: What we have is an increased-clearance piston....but piston rings that don't appear to have changed.
The only way you can increase the clearance of the piston is by decreasing its diameter. You can't decrease the diameter of the piston without also decreasing the internal diameter of the piston ring. Think about it.

If the piston was given increased clearance due to higher anticipated loads when wading, leading to greater expansion due to heat, why would you keep the outer diameter of the piston rings the same? - the rings form the outer edge of the piston assembly - they will foul with chamber walls first. Surely an increased-clearance piston requires increased-clearance rings?
phylo_roadking wrote: SOMETHING must have happened in the early Spring to cause the urgent fitment of the increased-clearance piston in May to all K5s from that point forward...UNTIL that stops and the new-spec rings are ordered into place in December.
phylo_roadking wrote: Seems so; perhaps WHY we don't hear any problems on the K5 before then? OR something else happened around then that made the change to the increased clearance necessary...
I'm confused now. Surely the increased clearance pistons were fitted precisely for the wading role?
phylo_roadking wrote: Except we have manual details from 1943 and 1945 that confirm there was NO change in the dimensions of the rings between those two years.
I think this needs looking at again, tbh.
phylo_roadking wrote:
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 intercahngeable 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.
Note the above in bold - "completely interchangeable" I.E they'd fit into the same dimension slots on the existing pistons, and as we've seen there's no recorded change in the technical records of a dimension change.
Yes, they would be interchangeable, because they are both for the increased-clearance (reduced diameter) pistons. The big difference I think is the change in piston diameter, which provokes what I believe are TWO revisions to the piston rings (one May 44, the other the corrective change of Dec 44).
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Re: Unserviceable Lorries - Jul - Sep 44

#293

Post by phylo_roadking » 18 Nov 2013, 00:33

The only way you can increase the clearance of the piston is by decreasing its diameter. You can't decrease the diameter of the piston without also decreasing the internal diameter of the piston ring. Think about it.

If the piston was given increased clearance due to higher anticipated loads when wading, leading to greater expansion due to heat, why would you keep the outer diameter of the piston rings the same? - the rings form the outer edge of the piston assembly - they will foul with chamber walls first. Surely an increased-clearance piston requires increased-clearance rings?
Did you notice that the change in piston design from May 1944 was specifically the piston skirt clearance? Rather than the piston crown? Historically there were several ways of achieving this as you know - several motorcycle applications in the WWII period used slotted piston skirts to allow for different heat expansion from the piston crown, for instance, and to allow for known "hot spots" in various designs.

On this..."If the piston was given increased clearance due to higher anticipated loads when wading, leading to greater expansion due to heat, why would you keep the outer diameter of the piston rings the same" - to do this in MAY, only weeks before D-Day - I smell some degree of panic about the measure for some reason :P Waterproofing the vehicles for the assault, exercising beach landings etc. should have been in progress for months, surely - was the May change inadequately tested, perhaps?

Or had an even worse problem, one we know nothing about, emerged in the early Spring with the "wading" engines that led to that urgent recall and fitment? 8O
I'm confused now. Surely the increased clearance pistons were fitted precisely for the wading role?
Yes - but RETAINED in the K5 engines built from new after that requirment, including a number of K5 variants...ambulances etc....that wouldn't have been wading. In the Austin Service Journal - War Department Issue, Vol. 9 (commencing January 1945) there's a note regarding the new-spec (December 1944)) which says the following regarding the K5 batches in construction at Austin's when the change was approved on 3/12/44 -
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
Unfortunately the HMVF member who supplied the above didn't have a copy of Volume 8....which might have been VERY illuminating! Nor did any of the other contributors to the thread :(

The big difference I think is the change in piston diameter, which provokes what I believe are TWO revisions to the piston rings (one May 44, the other Dec 44).
D-J....PLEASE....and I'm not being cheeky here, anything in addition to what we have brings more information to this - if you have anything other than a belief or know more, please let's hear it.

But at the minute we have no information at all regarding a MAY '44 change in the rings, or a dimension change in December - only a design and material change as noted twice by the D.M.E..
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Re: Unserviceable Lorries - Jul - Sep 44

#294

Post by Don Juan » 18 Nov 2013, 01:00

phylo_roadking wrote: Did you notice that the change in piston design from May 1944 was specifically the piston skirt clearance? Rather than the piston crown? Historically there were several ways of achieving this as you know - several motorcycle applications in the WWII period used slotted piston skirts to allow for different heat expansion from the piston crown, for instance, and to allow for known "hot spots" in various designs.

On this..."If the piston was given increased clearance due to higher anticipated loads when wading, leading to greater expansion due to heat, why would you keep the outer diameter of the piston rings the same" - to do this in MAY, only weeks before D-Day - I smell some degree of panic about the measure for some reason :P Waterproofing the vehicles for the assault, exercising beach landings etc. should have been in progress for months, surely - was the May change inadequately tested, perhaps?
Ah, so it was just the skirt. So I'm guessing the chamber wasn't lubricating as well, and the rings were wearing prematurely? Therefore a material change?
phylo_roadking wrote: Yes - but RETAINED in the K5 engines built from new after that requirment, including a number of K5 variants...ambulances etc....that wouldn't have been wading.
This may have been just rationalisation - they didn't want to have two specs, and thought they could get away with the wading spec. for normal use.
phylo_roadking wrote: D-J....PLEASE....and I'm not being cheeky here, anything in addition to what we have brings more information to this - if you have anything other than a belief or know more, please let's hear it.
I'll not be taking lectures on non-speculating posts from YOU of all people. :P
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Re: Unserviceable Lorries - Jul - Sep 44

#295

Post by phylo_roadking » 18 Nov 2013, 01:30

D-J....PLEASE....and I'm not being cheeky here, anything in addition to what we have brings more information to this - if you have anything other than a belief or know more, please let's hear it.
I'll not be taking lectures on non-speculating posts from YOU of all people.
Well, so much for me stating I wasn't being cheeky...if you go back to the start of this thread and read forward - this entire subject has been clouded for nearly seventy years by beliefs rather than facts - not least those American opinions preserved in print. Substantiating those beliefs....or removing them from the record...has been part of what this thread is all about.

Which is WHY there has been so much work done by so many people over the years - historians, amateur historians, vehicle restorers both "amateur" and professional, etc...
...and the rings were wearing prematurely? Therefore a material change?
At a guess. A good one given the materials change...Lymalloy ("D.T.D 485") was noted/marketed for its toughness over other common ring materials :wink: But all the REME test from Normandy says is "on completion of the test the cylinder head was removed for examination. It was at once apparent that heavy oil burning had been taking place..." And given the shagged condition of the valve guides ALSO noted, it's impossible to say how much had come down the guides past the equally damaged valves themselves....and how much oil had got up from below.

But Tom found a couple of other "period" REME references that seem pertinent...this one is typical;
"150 Austin 3-ton 4x4 lorries are now in Adv Base Wksps for fitting new pistons and rings" in the last week or so of September 1944.
In other words - that's what they were seeing up at the pointy end - rapid piston/ring wear...and that was all the cure they had available at the Advanced Base Workshops, and that cure STILL didn't work ;) The K5s were still "wearing out" fast....or rather, displaying all the evidence of advanced wear ;)
Yes - but RETAINED in the K5 engines built from new after that requirment, including a number of K5 variants...ambulances etc....that wouldn't have been wading.
This may have been just rationalisation - they didn't want to have two specs, and thought they could get away with the wading spec. for normal use.
Very possibly. Unfortunately that's part of the currently "invisible" PRE-D-Day events at Austin; in regards to your earlier suggestion of contacting the Heritage Motor Centre, a contributor to this thread did so some years ago - they don't have Austin's wartime records, apparently they were destroyed :( Which is why we've been reduced to building up a picture from "circumstantial evidence".
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Don Juan
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Re: Unserviceable Lorries - Jul - Sep 44

#296

Post by Don Juan » 18 Nov 2013, 01:38

Phylo - do you know if the piston skirt was reduced in diameter all the way around its circumference?

If it was this might go some way to explaining the change in the shape of the new rings, and why they had to be fitted a particular way up - it would have been to compensate for the likelihood of increased rocking at the top and bottom of the chamber due to the reduction in diameter of the skirt.
Very possibly. Unfortunately that's part of the currently "invisible" PRE-D-Day events at Austin; in regards to your earlier suggestion of contacting the Heritage Motor Centre, a contributor to this thread did so some years ago - they don't have Austin's wartime records, apparently they were destroyed :( Which is why we've been reduced to building up a picture from "circumstantial evidence".
Well if it was a rationalisation, I think it would be more likely to have been requested by the War Office, and not an internal Austin decision.
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Re: Unserviceable Lorries - Jul - Sep 44

#297

Post by phylo_roadking » 18 Nov 2013, 01:46

Phylo - do you know if the piston skirt was reduced in diameter all the way around its circumference?
No. But Likewise I haven't been told otherwise...
If it was this might go some way to explaining the change in the shape of the new rings, and why they had to be fitted a particular way up - it would have been to compensate for the likelihood of increased rocking at the top and bottom of the chamber due to the reduction in diameter of the skirt.
Something else to bear in mind...THIS old friend - read it very carefully again...
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 intercahngeable 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.
THESE two sentences leap out at me...
The manufacturers offered new and completely intercahngeable 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.
Is the taper on the compression rings the "design change"??? If not - why specify (sic) it in the very spartan minutes? 8O I know we're used to the outer edge of compression rings being tapered nowadays, but in vintage/veteran days and into the interwar period, I'm sure I've read that in low compression applications - lorry/bus engines etc. - ring technology remained quite...primitive...for quite a time!

And of course - the taper would necessitate the rings being fitted right way up! So the fact that the new rings were marked for correct one-way fitment and the old ones weren't would ALSO hint at the taper being...new?
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Re: Unserviceable Lorries - Jul - Sep 44

#298

Post by Don Juan » 18 Nov 2013, 02:08

Well a tapered design has less surface contact I believe, so lower friction and a lower lubrication requirement. The ring pack can be responsible for up to 50% of engine friction, although I'm not sure they were aware of this at the time. I suppose the new material would have allowed the taper design to have been created, so there would have been a double benefit in adopting it.
"The demonstration, as a demonstration, was a failure. The sunshield would not fit the tank. Altogether it was rather typically Middle Easty."
- 7th Armoured Brigade War Diary, 30th August 1941

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Re: Unserviceable Lorries - Jul - Sep 44

#299

Post by phylo_roadking » 18 Nov 2013, 02:21

Well a tapered design has less surface contact I believe, so lower friction and a lower lubrication requirement
So...less wear...and after all, if the oil scraper ring design was revised too...
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".
...that's possibly how they achieved lower cylinder wall lubrication - given that they stayed with the May-revised, increased-clearance piston design; they weren't going to be removing excess cylinder wall oiling that way.

Here's a question; leaving aside all the issues of wear for a moment - I take it it's axiomatic that less oil on the cylinder walls means less oil TO be contaminated by blow-by?
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Re: Unserviceable Lorries - Jul - Sep 44

#300

Post by Don Juan » 18 Nov 2013, 02:36

Well, I think the blow by will contaminate the oil in the crankcase anyway, so I'm not sure it makes much difference.

The other advantage of taper rings is that the combustion gas acts obliquely against the taper face, so there's a degree of pressure relief that tends to suppress the blow by to a certain extent. I'm assuming the original compression rings were rectangular faced?
"The demonstration, as a demonstration, was a failure. The sunshield would not fit the tank. Altogether it was rather typically Middle Easty."
- 7th Armoured Brigade War Diary, 30th August 1941

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