Bought a modifed Mamod.......

A very popular starting point for Live Steam. With their low cost comes a number of problems which can be discussed here
Post Reply
eiago25
Cleaner
Cleaner
Posts: 5
Joined: Thu Jul 03, 2014 6:38 pm

Bought a modifed Mamod.......

Post by eiago25 » Tue Jul 15, 2014 9:53 am

Sorry if this is a simple one, but my Mamod feet have only just landed - so I bought a modifed Mamod , and I've been overhauling and learning what makes it tick. One bit that has me confused is the on the smokebox , the clockhands has been replaced with what appears to be a 'valve' of some description. The 'steam out ' pipe from the reverser is routed through the chassis to this valve which appears to 'choke off' the steam through it before exhausting it to the chimney. Its a rotary type where a hole in a rod is rotated to give a shut off of not.. It seems to make no difference , exept the output noise is more of a shhhhh....shhhhh... Its that its only purpose in life.
Sorry if its obvious but I'm only just learning Mamods!

DLRdan
Driver
Driver
Posts: 1083
Joined: Wed Nov 12, 2008 12:05 am
Location: Blyth
Contact:

Post by DLRdan » Tue Jul 15, 2014 11:13 am

The valve is an exhaust regulator. It works in a similar way to the regulator in the cab but has one major advantage. It controls the speed in a similar way to a govenor. As the loco speeds up more steam passes through the cylinders. When the valve is partialy closed this creates back pressure in the cylinders slowing the loco. When the speed decreases, in a curve or climbing hills, the back pressure decreases alowing the loco to pick up speed again. For this to work the cab regulator is normally left fully open and the speed controlled with the exhaust regulator. It has been used on many locos but is an unusual addition to a Mamod
Dan,

James: "Dan, can you use your hearing and tell me if that trains coming ?"
DLR
www.freewebs.com/dlrail

kandnwlr
Trainee Driver
Trainee Driver
Posts: 998
Joined: Fri Dec 02, 2011 3:14 pm
Location: Alsace, France

Post by kandnwlr » Tue Jul 15, 2014 11:54 am

DLRdan:102680 wrote:The valve is an exhaust regulator. It works in a similar way to the regulator in the cab but has one major advantage. It controls the speed in a similar way to a govenor. As the loco speeds up more steam passes through the cylinders. When the valve is partialy closed this creates back pressure in the cylinders slowing the loco. When the speed decreases, in a curve or climbing hills, the back pressure decreases alowing the loco to pick up speed again. For this to work the cab regulator is normally left fully open and the speed controlled with the exhaust regulator. It has been used on many locos but is an unusual addition to a Mamod
Thanks. That also helped me get my head around it. A precise and neatly argued description of a technical Innovation.

eiago25
Cleaner
Cleaner
Posts: 5
Joined: Thu Jul 03, 2014 6:38 pm

Post by eiago25 » Tue Jul 15, 2014 2:19 pm

Thanks for that explanation - thats a good and easy to understand explanation- very interesting as I have never come across one before... Brilliant and thanks again..

User avatar
IrishPeter
Driver
Driver
Posts: 1400
Joined: Wed Feb 23, 2011 3:24 am
Location: 'Boro, VA

Post by IrishPeter » Tue Jul 15, 2014 5:07 pm

The exhaust regulator performs the valuable service of keeping a Mamod on the rails and below Mach 1!

Peter in AZ
Traffic Pattern? What pattern? Spuds out; grain in, but cattle, sheep and passengers are a lot less predictable.

Post Reply

Who is online

Users browsing this forum: No registered users and 3 guests