class T9 chassis rot

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class T9 chassis rot

Postby GWR_fan » Sun Sep 27, 2015 10:42 pm

Just read on another site of Mazak issues with the Southern T9. I will need to investigate as I have four sitting unused in their train packs, tested when received but never seen since. Fingers crossed!!!!!!!!!

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Re: class T9 chassis rot

Postby GWR_fan » Sun Sep 27, 2015 11:46 pm

Well, a 50% pass rate. When I received the four sets some two years ago one locomotive would not run (even though a certificate enclosed by the dealer assured me that the loco had been test run successfully). When I investigated I put the cause, a broken rear motor mount, down to intransit shipping damage as the loco also suffered cosmetic damage as well (crushed cab and broken off running plate steps). The dealer was decidedly unhelpful when informed.

To fix the locomotive, knowing spares were unavailable, I simply glued the motor back to the chassis. This fix while very unsatisfactory, at least worked. When tested today, the 'fix' is still functional. This locomotive came from the '1938 Suburban' train pack (T9 #312 in olive green livery).

OK, fast forward to today and the loco from my second '1938 Suburban' pack exhibits the same problem. The rear motor mount is Mazak and it has simply cracked/separated away at its base. On the T9, the forward gearbox cover is held in place by the squeeze fit inside the loco body. There is no physical restraint at all, such as mount screws. Thus when the motor rear mount separates the motor is free to move, resulting in the gears disengaging. I commented on this poor design some time ago on this forum when initially reporting my findings when the set packs were originally received.

The fracture line on the mazak casting is indicative of 'corrosion/stress' failure. Odd that is is only the two locomotives from the '1938 Suburban' packs that are affected (T9 #312). The two locomotives from the 'Imperial Airways' setpacks seem to be OK, although with a 50% failure rate so far and all four locomotives have less than five minutes running each, I am not confident for the future. The rear mount plate is obviously not capable of performing its task and will fail. I find it odd that Mazak was used for such a thin casting when an engineering plastic would have been perfect for the task. The weight difference between the mazak and plastic casting would have been inconsequential to the final weight of the locomotive.

I seriously doubt the availability of a spare part being available, plus the wires pass through the mount so a rewire would be necessary to change the mounting plate, thus I can see another 'glue' repair being needed. Not a happy Hornby customer at the moment!!!!!!!

Edit: on reading back through the forum it seems that one of the '1938 Suburban' pack locomotives received about one hour's running time as it had a surging issue with poor power pickup from the tender.

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Re: class T9 chassis rot

Postby GWR_fan » Mon Sep 28, 2015 12:11 am

Photograph showing fatigue fracture of the T9 motor mount plate (the plate normally slips over the rear bearing journal cover on the motor and is screwed to the chassis). This is my second failure of this type. Not obvious is the rough fatigued surface of the break.
Attachments
t9a.JPG
T9 failure
t9a.JPG (74.02 KiB) Viewed 4025 times

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Re: class T9 chassis rot

Postby GWR_fan » Mon Sep 28, 2015 1:15 am

When I removed the chassis a piece of mazak approximately 0.250" X 0.250" fell out. I have no idea where that comes from. Against my wishes I glued the drive back together and now have it running OK. A compromise for sure but a certainty is no more Hornby small locomotives.

I should have listened to all the faults reported when the loco was first released a couple of years ago, but until today I believed my first broken motor mount was due rough shipping handling. Now with a second failed mount, I am sure that I am not alone. These locomotives are simply far too fragile for general usage. These are a timebomb awaiting detonation.


Edit: I checked the Hornby service sheet for the T9 and the end mount plate is X9945. The motor sits on a saddle that is not available as a spare part. Surprisingly, the gearbox cover is actually part of the saddle casting and yet I have not seen a loco disassembled that the gearbox cover was integral with the saddle. I assumed the cover was a separate part, loosely fitting and secured by its tight squeeze into the loco body. However, when one looks at the saddle casting there are two unpainted nodules about 1 mm square, at the forward end which are the cast connecting points to the cover. The cover should not be separate to the saddle. This final info is not crucial to loco operation but does complicate reassembly.

Thus the motor mount has two issues. Firstly the rear mount plate is not robust enough and secondly, the fragile saddle casting results in the gearbox cover separating from its casting with the saddle. Overall, a very poor design. Hopefully, Hornby have made alterations to motor mounts on later locomotives.

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Re: class T9 chassis rot

Postby GWR_fan » Mon Sep 28, 2015 5:12 am

Looks like I am not alone. As I stated some time ago, this design of motor retention is poorly executed and plain dumb!!!!!!!! My failure is the same as those failures described over on the other place. Apparently, Hornby are unresponsive to this problem (ostrich head in sand phenomenon).

http://www.rmweb.co.uk/community/index. ... -retainer/


Edit: most failures found refer to #312 from the "1938 Suburban" train pack (3 axle tender). Given the history, I await failure of the two watercart tender models as well.

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Re: class T9 chassis rot

Postby skyblue » Mon Sep 28, 2015 7:51 am

I had never heard of Mazak rot being a problem with any steam locomotives, although the handrails on my old Hornby Castle Class are now very brittle and flakey, which someone said could be Mazak rot but as I understood it Mazak is only used for large castings?

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Re: class T9 chassis rot

Postby GWR_fan » Mon Sep 28, 2015 8:15 am

skyblue wrote:I had never heard of Mazak rot being a problem with any steam locomotives, although the handrails on my old Hornby Castle Class are now very brittle and flakey, which someone said could be Mazak rot but as I understood it Mazak is only used for large castings?


Not only the T9 but apparently the Hornby "Royal Scot" class could be the next 'class 31' fiasco. The Railroad -9F tender chassis that used the housing of the old tender drive locomotive has been sporadically reported as suffering the rot.

As most locomotives these days, whether steam or diesel outline, use mazak in their construction the risk is always there as most likely the process worker in the casting department is not a metalurgist.

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Re: class T9 chassis rot

Postby alex3410 » Mon Sep 28, 2015 10:04 am

its such a shame your having these issues as the T9 is a lovely little loco

i know its not much help but its been interesting reading your 'troubleshooting' etc so thank you for posting :)

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Re: class T9 chassis rot

Postby GWR_fan » Mon Sep 28, 2015 10:29 am

Alex,
the T9 is a beautifully modelled locomotive with exquisite detail. It does run extremely smoothly, but in my opinion the drive is simply too fragile. It has been engineered to fit inside a very narrow locomotive dimensions, although the choice of mazak for such a thinly moulded motor mount saddle is a poor decision. The saddle mount and rear plate should have been moulded in a more robust material.

I believe the gearbox cover portion of the saddle breaks away, leaving the saddle mounted by just the thinly cast rear mount. It is just not up to the job and breaks away. Embrittlement would aggravate the eventual destruction of the mount plate. The motor is then free to disengage from the idler gear.

In days of old it was common with fitting can motors to brass chassis to use a sealant to 'bond' the motor. This allowed a degree of flexibility. However, generally in these circumstance the motor was mechanically secured at the pinion end by a gearbox. With repairs on the T9 one is relying on the glue to retain the gears in mesh. I am not overly confident of it being a permanent fix.

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Re: class T9 chassis rot

Postby Bigglesof266 » Mon Sep 28, 2015 10:32 am

Thanks for the heads up Tim.

Why am I unsurprised?

If they were a $20 toy from ALDI then one mightn't complain given expectations commensurate with price. But they ain't.

I have two T9s, one from each train pack. The one you refer to from the Southern Suburban has had the most running. Although I haven't run her for a few months now awaiting a spare part from Peters to fix her brake main frame rod holders I'd been meaning to do ever since receipt. Broken off when I received it, nothing floating around in the box. Ha. Such is Hornby QC.

I'll have a squiz at mine to see the condition. But it would seem a bad batch casting thing, so if it's still intact, evidently it'll just be a matter of time nefore mine breaks off too.

I'm bettting Hornby will remain silent unless 'beseiged' with a unified group approach as a single "what are you going to do for us about it?" voice they find difficult to deny with an answer of silence. Regardless the semantic or pedantry re warranty obligation or legal liability, as it's apparent the cause is a manufacturing flaw encumbered by poor design lending fragility to the part, their attitude to their customers will be reflected back at them in how they deal with this. Call me cynical, but my expectations of them actually doing anything about it worth a tinkers damn can't be described as exuberant.

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Re: class T9 chassis rot

Postby GWR_fan » Mon Sep 28, 2015 10:43 am

Keiron,
as stated in my initial posting I thought the failure a result of poor shipping handling as the loco itself suffered substantial body damage (repairable fortunately). It was only perchance I saw the posting today on another site that got the little grey cells working and to test the other three locomotives. After repairing the drive (second failure) and giving it a good run I went looking further and found the second link with the same damage as mine had been previously reported. It never occurred to me that the original failure could be mazak related as after the class 31 fiasco a sensible observer would think that Hornby would improve its production to eliminate the future possibility of a failure occurring.

Alas, it seems the rate of failure factor at play. Like a large American car company weighing up a recall option for a known defect or simply paying out an insurance claim should it occur. Hedging one's bet is a likely outcome to minimise the cost of a total recall.

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Re: class T9 chassis rot

Postby Bigmet » Mon Sep 28, 2015 1:30 pm

I'd encourage writing it up to Hornby, with R number. That's the way it will most quickly become apparent that there is a systematic problem with a particular batch of a model.

One hopes they have left this problem behind since disengaging from manufacture subbed out to Sanda Kan: but there are half a dozen production shops working for them now.

skyblue wrote:I had never heard of Mazak rot being a problem with any steam locomotives, although the handrails on my old Hornby Castle Class are now very brittle and flakey, which someone said could be Mazak rot but as I understood it Mazak is only used for large castings?

Mazak can be used for very small castings, and has long been the dominant choice for cast parts on RTR model railway products. Most recent notable mazak failure on OO steam models: the early versions of the SR N class 2-6-0 from Bachmann had footplates cast from contaminated mazak, which very thoroughly deformed and then disintegrated. Bachmann supplied replacement castings.

There's plenty of alternative alloy choices that could be employed, but there isn't a low cost casting alloy out there that doesn't have a significant degradation problem/vulnerability of some sort. Mazak is established as the standard choice as it possesses a basket of favourable qualities at a relatively low price, which delivers a sharp casting of useful mass with minimal tool wear; and has decent life expectancy, provided that the melt is uncontaminated. It's all down to process discipline - which means investment in controls and staff training - in the production shop.

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Re: class T9 chassis rot

Postby Bufferstop » Mon Sep 28, 2015 2:12 pm

This is the same problem that a year or so ago afflicted the Toby the Tram chassis. It's the purity of the Mazak that determines it and it was recognised in the UK in the late 1930s, post WW2 production by most companies had the benefit of very high purity levels which eliminated the problem. The situation with Chinese manufacture is complicated by the practice of sub-contracting the production of parts to smaller companies, where it is diicult to enforce quality standards.
However, from the description of the chassis it may not (or not wholly) be down to rot, it sounds as though cross sectional areas of parts of the casting may simply not be sufficient to withstand normal usage. Presumably Mazak is cheaper than other alloys/engineering plastic, back to those smaller companies again equipping for plastic injection moulding would probably be beyond their finances and the purity of other alloys would be suspect.
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skyblue
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Re: class T9 chassis rot

Postby skyblue » Mon Sep 28, 2015 2:21 pm

Bigmet wrote:Mazak can be used for very small castings.


I was aware of it's use for castings such as the footplates you mention (I was considering them to be large in comparison to the handrails on a steam loco) but is it likely that handrails could be made from Mazak?

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Re: class T9 chassis rot

Postby Bigmet » Mon Sep 28, 2015 2:39 pm

Certainly have seen examples of such, cast as a piece. Nowadays usually just the knobs cast, with drawn wire as the handrail.


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