Repairing a Class 31 with Mazank Rot......

[dogbox321]

Hi all, after finding my 31270 looking like something in a scrap yard, or thats had a collision.  Unfortunately it had suffered from Mazank Rot, then I have done this thread to update on progress - I am sure a few people have the same issue! Plus to ask a couple of questions along the way.

 

I have tried running it - and it don't run - occasionally the lights start, but then it displays a red light on the Gaugemaster Controller, which I expect means a short circuit.  Can the rot cause a short somewhere?  Or is that something else.

 

So three things.....

1) - Repair the body

2) - Amend the chassis to remove the expansion from the rot

3) - Get it to run!

 

Best Regards,

 

C.

[Trevellan]

This is a well-known and much debated topic which you can search for on RMweb.

 

As an alloy, mazak is prone to problems with impurities, which in turn can cause the metal to expand and/or crumble. The Hornby 31 is by no means the only offender. I have a Heljan 47 with similar problems.

 

Your crumbling chassis is only likely to be useful for yielding a few spares. As I said, the issue has been well-covered on RMweb and you would be well advised to spend a little time on research before making any decisions.

[34theletterbetweenB&D]

4 minutes ago, dogbox321 said:

...I have tried running it - and it don't run - occasionally the lights start, but then it displays a red light on the Gaugemaster Controller, which I expect means a short circuit.  Can the rot cause a short somewhere? ...

Quite possible.  Could be the detached parts of the castings that provide the cab floors might be shorting across the tops of the wheels, but there are plenty of other potential causes.

 

But there's no point speculating, remove the mechanism from the body, and start testing now that you can see what you are doing. I have had no difficulty with the running of the four Mazak rotted chassis that I purchased in that state. (Hornby thoughtfully put a splined slide in the drive shafts so that even if the chassis block lengthens significantly the drive remains engaged between the motor and the worms on the bogie gear towers!)

[dogbox321]

Hi, thanks for the info gents.  

 

Firstly, I have had a go at repairing the body, which I think is pretty good.  I would have preferred not to, but its better than when I opened the box!

 

Second - (a couple of photos of the chassis), as it is at the moment. 

 

If it is shorting, I'd be very happy to know where its likely to be.  One end far more damaged than the other, with a large bow.  The chassis I believe sits below the cab fronts, so I am wondering whether I could get away with just removing some of the plastic on the front of the light unit, and thinning the side a little where the crack was, so the body sits on the chassis ok.  I've also had to glue the brass bushes in, and rebuild the plastic that holds them, as all 4 bushes were broken off!

 

Best Regards,

 

C.

[Tallpaul69]

Hi Dogbox,

This is useful especially the pics-I have three of these to try to fix!

 

I will be interested in further updates on your progress with this project?

 

Cheers

Paul

[Tallpaul69]

On ‎03‎/‎02‎/‎2020 at 16:22, 34theletterbetweenB&D said:

Quite possible.  Could be the detached parts of the castings that provide the cab floors might be shorting across the tops of the wheels, but there are plenty of other potential causes.

 

But there's no point speculating, remove the mechanism from the body, and start testing now that you can see what you are doing. I have had no difficulty with the running of the four Mazak rotted chassis that I purchased in that state. (Hornby thoughtfully put a splined slide in the drive shafts so that even if the chassis block lengthens significantly the drive remains engaged between the motor and the worms on the bogie gear towers!)

Hi there,

Any writeup/pics on how you dealt with the chassis you bought would be appreciated!

 

Alternatively, do you want to buy three more, or would you consider taking on my three to repair for me as a commission?

 

Best regards

Paul

[34theletterbetweenB&D]

21 hours ago, Tallpaul69 said:

...Any writeup/pics on how you dealt with the chassis you bought would be appreciated!

 

Alternatively, do you want to buy three more, or would you consider taking on my three to repair for me as a commission?

Thanks for the offer but I am replete; sure there will be others here who might like them. And I couldn't take money for my 'conversion'. In short: chop the wires holding the dangling ends on, remove the board and fan mechanism, hardwire decoder. Take one old Airfix GMR Brush 2 body, (long ago tidied with flush glazing etc.) clear interior, skim down interior ribs of the body for a snug push fit, ram home modified mechanism.

 

This old body looks like a Brush 2 in the critical respect which the current Hornby model has wrong, the inset cabside windows, with the step out to full body width immediately behind the cab door. With the new mechanism 'installed' it now has the sweet and quiet running characteristics that Airfix GMR's mechanism could not supply.

 

(I very much liked the Hornby mechanism but couldn't bring myself to buy this misshapen lump despite its many other merits, and especially the sweet running drive. I likewise escaped buying mazak rotting Heljan Brush 4s too, as the tubbiness was 'all wrong'! Clearly mazak rot is accelerated by aesthetic errors...)