Suspension Question

[A.R.]

Hi All, 

 

I wondered if someone could advise me on leafsprings. 

 

I understand a leafspring but note many on diesel or electric loco bogies have coil springs also attached. On the drawing below, I assume that as the axlebox rises up, the leafspring bends upwards, pivotting on its anchor points to the bogie frame at the two points in green. Therefore, my question is how do the coil springs come into it, where are they "anchored" so to speak and how do they contribute to the suspension system overall? (Please excuse the crude drawing!)

 

 

Any help would be greatly appreciated. 

 

Kindest regards, 

 

Alex 

[ISW]

1 hour ago, A.R. said:

Any help would be greatly appreciated. 

 

Alex,

 

A coil spring is generally under compression under 'normal' circumstances. Hence the arrangement on a Class 40, 44, 45, or 46 bogie is as follows:

 

Ian

[A.R.]

Hi,

 

Thanks for the reply and the information, it's very helpful. Just to ask a couple of follow up questions: what's the point of the coil spring, especially if it's under compression in normal conditions? And is the leafspring fixed to the bogie frame anywhere?

 

Cheers,

 

Alex

[Wheatley]

The leaf spring provides primary suspension - ie it is the point at which the load acts directly. It in turn is mounted on secondary coil springs which allow more movement without requiring the leaf springs to be ridiculously long or thick. The leaf spring is itself mounted on springs. 

 

There are several ways of doing it, on a 15x series DMU the primary spring is usually a coil spring on a swinging arm, and the secondary suspension is the air bag between the bogie and the body.  You can't put the secondary suspension between the bogie and body on a 45 because the bogie pivot takes the buffing shocks (bogie mounted buffers and drawgear). 

Edited October 23, 2021 by Wheatley

[45125]

4 hours ago, Wheatley said:

The leaf spring provides primary suspension - ie it is the point at which the load acts directly. It in turn is mounted on secondary coil springs which allow more movement without requiring the leaf springs to be ridiculously long or thick. The leaf spring is itself mounted on springs. 

 

There are several ways of doing it, on a 15x series DMU the primary spring is usually a coil spring on a swinging arm, and the secondary suspension is the air bag between the bogie and the body.  You can't put the secondary suspension between the bogie and body on a 45 because the bogie pivot takes the buffing shocks (bogie mounted buffers and drawgear). 

The coil springs also have rubber block between steel plates these act as dampers on the coil springs. The leaf spring with this type of mounting also controls the lateral movement of the ale.