Mazak Rot has unfortunately blighted some models in the hobby, across many manufacturers and for a while. It frequently manifests itself after a period of time often years, and that’s the problem you don’t know if you’re going to end up with it, and in fairness neither do the manufacturers.
I have to say I’ve been lucky with this, and yep, you’re right there’s an ‘until now’ coming! So, whilst looking at a forthcoming project I dug two BR era Hornby Stanier 4-6-0’s out. They’d been in stock for a few years, tested and checked on arrival, and then stored in temperature controlled dry environments. Being a Royal Scot and Patriot they share the same chassis and motor components, and they were pretty much concurrently released.
On checking both they had similar symptoms, very ragged and erratic running and a clicking noise when stationary with the motor under power. I assumed that I was going to be looking at split gears, an occasional problem which affects plastic gear trains. Choosing the Scot first, I very quickly realised that split gears was unlikely to be the issue.
The crazing around the front of the frame is typical of indications of Mazak Rot, this came as a bit of a surprise, as I don’t associate the Hornby Scots or Patriots with this problem.
Removing the bogie shows further fractures, I’m now thinking this isn’t going to end well! The screw above holds the chassis in place with two lugs at the cab which are the three mounting points.
The DCC mounting plate covers the gear train fixing which is a cast cover. But holding the casting tight to the chassis, the chassis runs, so it’s not a split gear I’m dealing with. I removed the mounting plate and the gear train/boiler casting was loose, undoing its screw made no difference. Lifting the wiring loom allowed the casting to fall to one side, showing the fixing location had sheared.
Not just once but twice, leaving a cross section slice!
This single mounting with this screw is the kingpin of this chassis. If it’s damaged (as these are) the chassis is unusable. There is a potential fix with a longer screw, but almost certainly a pillar drill and a thread tapping being required. As these were concurrently released I immediately wondered if the Patriot would be the same issue.
Immediately the Mazak issue was evident. Removing the chassis meant the front section came adrift.
This chassis exhibited an identical fault, the gear casing casting fixing has sheared/fractured where the screw fixes to the chassis.
So two identical faults and Mazak damage. Refitting the Scot body and pressing the front of the chassis into position, it too gave way.
It’s particularly frustrating as neither model has had any real use, just been stored appropriately. Whilst it’s Hornby’s responsibility, it’s not their fault, that failure lies with the contractor that supplied poor quality material chassis. They’re too old to get a refund, so now it’s time to try and get a replacement pair of chassis’, and revisit the project they were for. I’ll update with any news in due course.