Martin Wynne
Admin
- Location
- West of the Severn UK
- Info
@James Walters
Hi James,
I have just been watching your latest Bexhill West video about your cassette system:
That's very ingenious! But there is one thing worrying me.
Using aluminium alloy as running rails is a bad idea, especially for P4.
Aluminium has a very thin but hard oxide layer on the surface which is a poor electrical conductor. If you clean or cut into it, the oxide surface reappears within a fraction of a second in air.
This means that electrical pickup from a rolling contact on aluminium alloy causes significant sparking. Which creates a build-up of burnt crud on the wheels, which makes the problem progressively worse. You will be in for a lot of frequent wheel cleaning.
In P4 it is even worse, because P4 wheels have such shallow flanges that any significant build-up of dirt on the wheels can reduce the effective flange depth to such an extent that you start getting derailments. This is the well-known "Sunday afternoon derailments" effect on large P4 layouts at exhibitions (although there aren't very many large intensively-run P4 layouts around). Nowadays a lot of exhibition halls are air-conditioned, which has much reduced this problem from general atmospheric dust and dirt on model railways.
I suggest running ordinary nickel-silver rail along the cassettes instead of relying on the the alloy angle for electrical pickup. That might mean that the the angle doesn't need to be metallic and you can use something laser-cut instead.
If it was anything else sliding along aluminium alloy you could arrange some sort of sliding contact or pick-up plunger which would work much better than a rolling wheel contact. Unfortunately that's not going to look too good on a finescale P4 locomotive.
I just know that several folks will now say that they have been using aluminium-angle cassettes for years without any problems. But I remember hours spent cleaning wheels at club exhibitions, and the difficult-to-remove black line which appears along the angle after a long operating session.
There was a similar problem with the old H&M solenoid point motors when they changed from using brass contact rivets to aluminium rivets in the integral polarity changeover switch. I remember drilling out the burnt aluminium rivets and replacing them with roundhead brass screws and nuts.
I hope you don't mind my posting this publicly. I'm not keen on writing emails and private messages when I know the information will be of interest to many others.
cheers,
Martin.
Hi James,
I have just been watching your latest Bexhill West video about your cassette system:
That's very ingenious! But there is one thing worrying me.
Using aluminium alloy as running rails is a bad idea, especially for P4.
Aluminium has a very thin but hard oxide layer on the surface which is a poor electrical conductor. If you clean or cut into it, the oxide surface reappears within a fraction of a second in air.
This means that electrical pickup from a rolling contact on aluminium alloy causes significant sparking. Which creates a build-up of burnt crud on the wheels, which makes the problem progressively worse. You will be in for a lot of frequent wheel cleaning.
In P4 it is even worse, because P4 wheels have such shallow flanges that any significant build-up of dirt on the wheels can reduce the effective flange depth to such an extent that you start getting derailments. This is the well-known "Sunday afternoon derailments" effect on large P4 layouts at exhibitions (although there aren't very many large intensively-run P4 layouts around). Nowadays a lot of exhibition halls are air-conditioned, which has much reduced this problem from general atmospheric dust and dirt on model railways.
I suggest running ordinary nickel-silver rail along the cassettes instead of relying on the the alloy angle for electrical pickup. That might mean that the the angle doesn't need to be metallic and you can use something laser-cut instead.
If it was anything else sliding along aluminium alloy you could arrange some sort of sliding contact or pick-up plunger which would work much better than a rolling wheel contact. Unfortunately that's not going to look too good on a finescale P4 locomotive.
I just know that several folks will now say that they have been using aluminium-angle cassettes for years without any problems. But I remember hours spent cleaning wheels at club exhibitions, and the difficult-to-remove black line which appears along the angle after a long operating session.
There was a similar problem with the old H&M solenoid point motors when they changed from using brass contact rivets to aluminium rivets in the integral polarity changeover switch. I remember drilling out the burnt aluminium rivets and replacing them with roundhead brass screws and nuts.
I hope you don't mind my posting this publicly. I'm not keen on writing emails and private messages when I know the information will be of interest to many others.
cheers,
Martin.
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