Minerva Teddy Bear, a cautionary tale...

Jordan

Jordan

Mid-Western Thunderer
Just a word of advice for those who own a Minerva 7mm Class 14/D95xx/Teddy Bear.

As some of us found out at purchase, a crank pin or two could be loose. Now mine has not done much mileage at all, and I came to run it for the first time in several months the other day - it didn't run well at all, with that dreaded 'click click click' as a loose crankpin hit the cab steps with every wheel rotation.
I decided to check all the crankpins, and every single one was loose - some, very loose!!!
This is most surprising and disappointing, but all the more so considering how little use my model has had, so I urge everyone who has one of these locos to regularly check all the crankpins, especially if your's does a fair bit of running.
For a Back of the Class type question, is there a proper tool for tightening them?, as they are very slim & the flats are shallow, my tweezers aren't much good on them but flat nose pliers are a bit of overkill, I don't want to over tighten them...
 
Jordan

Jordan

Mid-Western Thunderer
Eastsidepilot said:
I would suggest that crank pins and/or nuts should be fitted with a touch of thread lock such as Loctite 243 ( Blue), this will stop them coming undone but will still release when required.


Col.
Click to expand...
Yes, "but".... here at the Back of the Class introducing any sort of glue to parts like crankpins runs the very real risk of gumming up the whole lot, rods and all..!! :confused: :oops: :shit:

I suppose at least if the whole lot was glued up solid so the loco couldn't move at all, the problem of loose crankpins would be solved!! :) :))
 
MarkR

MarkR

Western Thunderer
I use a tiny drop of nail varnish, bright red, but other colours are available!
Mark
 
Eastsidepilot

Eastsidepilot

Western Thunderer
Jordan said:
Yes, "but".... here at the Back of the Class introducing any sort of glue to parts like crankpins runs the very real risk of gumming up the whole lot, rods and all..!! :confused: :oops: :shit:

I suppose at least if the whole lot was glued up solid so the loco couldn't move at all, the problem of loose crankpins would be solved!! :) :))
Click to expand...
:rolleyes: ..........you're not supposed to use the whole tube Jordan:headbang::D
 
Yorkshire Dave

Yorkshire Dave

Western Thunderer
Jordan said:
I suppose at least if the whole lot was glued up solid so the loco couldn't move at all, the problem of loose crankpins would be solved!! :) :))
Click to expand...

Problem solved :) - it would be modelled as sitting around just after withdrawal from service prior to being sold on..... :rolleyes::))
 
Osgood

Osgood

Western Thunderer
Well you try finding a Blue Loctite meme :))

Anyway - its Blue for the back of the class, Red for right up there at the front.
Nail varnish seems a safe bet.
 
simond

simond

Western Thunderer
Purple…

Red Loctite threadlocker​

Red Loctite threadlocker is considered to have high adhesion strength. It cannot be removed by simply applying torque, but requires special heat in combination with torque (or special chemicals) to disassemble the components after the red Loctite threadlocker has been applied. It is available in either a semisolid anaerobic or liquid form, and once applied to the threads it will cure in 24 hours. Common versions are: Loctite 262, Loctite 268, Loctite 271, and Loctite 272.

Green Loctite threadlocker​

Green Loctite threadlocker is considered to have high adhesion strength for wicking. It is ideal for preassembled fasteners, like set screws. It cannot be removed by simply applying torque, but requires special heat in combination with torque (or special chemicals) to disassemble the components after the green Loctite threadlocker has been applied. It is available in a liquid form, and once applied to the threads it will cure in 24 hours. Common versions are: Loctite 270 and Loctite 290.

Blue Loctite threadlocker​

Blue Loctite threadlocker is considered to have medium adhesion strength. It can be disassembled with high torque, but it is easier to disassemble with special chemicals and/or heat. It is available as a tape, semisolid, or liquid form, and once applied to the threads it will cure in 24 hours. Common versions are: Loctite 242, Loctite 243, and Loctite 248.

Purple Loctite threadlocker​

Purple Loctite threadlocker is considered to have low adhesion strength. It can be disassembled with low torque with the same hand tool used to install it. It is available in a liquid form, and once applied to the threads it will cure in 24 hours. The most common version is Loctite 222.


What is the difference between Loctite threadlocker colors?. Usual disclaimers, indeed, I’m not a customer satisfied or otherwise, it was the simplest explanation I could find. Given the Henkel are a global company, you’d think they’d want one simple visual product chart, but there seem to be hundreds…

Also, I’m interested by the concept of “special heat”. This flies in the face of all the physics I’ve ever learned…
 
Richard Gawler

Richard Gawler

Western Thunderer
simond said:
What is the difference between Loctite threadlocker colors?. Usual disclaimers, indeed, I’m not a customer satisfied or otherwise, it was the simplest explanation I could find. Given the Henkel are a global company, you’d think they’d want one simple visual product chart, but there seem to be hundreds…

Also, I’m interested by the concept of “special heat”. This flies in the face of all the physics I’ve ever learned…
Click to expand...

There is a Henkel chart here with examples of applications and explanations:
Common Projects that Utilize LOCTITE® Threadlockers

The "special heat" is now called "localised heat" so something we can comprehend.

I will make a guess, the "special heat" has come from a translation of "localised heat" into Simplified Technical English, this is a controlled vocabulary widely used in the aviation industry.
 
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S

Simon H

Member
A cautionary note about thread locking compounds, hoping I'm not trying to teach my grandmother to suck eggs (and bearing in mind I'm unfamiliar with the model you're applying it to)...are the threads you're screwing into metal, or plastic?
Many years ago there was a comment in MRJ about thread locker attacking some plastics, such as the ABS used in some model locomotive wheels and other components.
About 25 years ago, we had a problem at work with some ABS components that had a spring attached to them by a screw, which passed through the moulding and into a threaded spacer, Loctite thread locker (243 IIRC) being applied to the threads to prevent them from working loose. A large batch of these was rejected as the ABS had cracked and begun to disintegrate around the area where the Loctited screws had passed through; on checking the data sheet it was found that the 243 was not compatible with some plastics, the effect in this case being quite dramatic! I've a feeling that the information was not that obvious and needed to be looked for (which was why Production Engineering and QA missed it).
I hope this isn't a problem, but just in case...Simon.
 
simond

simond

Western Thunderer
I’d add to that, these compounds work by swelling when they “set”, and in general are metal-catalysed.

So if you don’t have at least one metal component, they won’t work at all, and,
If your female component is plastic, it will be under considerable load which may cause cracking of eg a wheel hub
 
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