Axlebox coil springs.

[eightpot]

Is there any info available of a method of setting up these springs to get a reasonably even weight distribution on a 5" gauge loco? Also what is needed to do it.

[andyhigham]

You can't change weight distribution by altering the springs!
However if the loco is front or rear heavy stronger springs on the heavier axle will help level things out. Adding shims to the end of the springs will change the ride height

[coniston]

May 11, 2021 12:38:46 GMT eightpot said:

Is there any info available of a method of setting up these springs to get a reasonably even weight distribution on a 5" gauge loco? Also what is needed to do it.

As a starter, check out my thread (as yet not concluded) here: modeleng.proboards.com/thread/14222/axle-weighing-first-experiments?page=1

And yes setting springs will allow the most even weight distribution however that will only go so far unless the weight is relatively evenly distributed along the length of the loco.

Chris D

[robmort]

May 11, 2021 13:22:47 GMT andyhigham said:

You can't change weight distribution by altering the springs!

On the contrary, you certainly can! ... especially on intermediate axles

Take a simple example on an 0-6-0 where there is no or a very light spring on the centre axle. Then most of the weight is taken on the outside axles.

[andyhigham]

Unless the weight distribution is sorted first, you will never get equal axle loading
For a loco without leading and or trailing trucks the centre of gravity has to be above the centreline of the wheelbase to get equal loading.
Take a simple 0-6-0 if the axle loadings are 5Kg front 10KG centre and 15Kg rear. Adjusting the center axle springing will transfer some of the outer axle loading to or from that axle.
Adjusting the front centre and rear axle springing will never move 5Kg from the rear axle to the front
The loco also needs to ride level, the example above will ride tail down. Stronger springs in the rear will bring the loco level but it will still be 5Kg 10Kg 15Kg. A 10Kg weight over the front axle would bring the loadings to 15Kg 10Kg 15Kg, adjusting the centre springing could then give 13.3Kg 13.3Kg 13.3Kg

[robmort]

Seems there is a confusion about meaning of "weight distribution" and "centre of gravity".

As you say: "...if the axle loadings are 5Kg front 10KG centre and 15Kg rear. Adjusting the center axle springing will transfer some of the outer axle loading to or from that axle."

Hence you say you can indeed adjust weight distribution by adjusting the springs.

Of course for an 0-6-0 you need a centralised COG as a prerequisite for even weight distribution, but that's only one wheel arrangement.

[andyhigham]

It applies to any wheel arrangement, if the centre of gravity isn't in the middle of the rigid wheelbase there will always be a bias to one end. A loco with leading or trailing trucks can take some of the imbalance onto the truck at the expense of adhesion.
If our 0-6-0 was an 0-6-2, we could carry say 5Kg on the truck giving a loading of 5Kg 10Kg 10Kg 5Kg. If we wound the springs back on the centre and rear axles it may be possible to equalise the loadings but the rear buffer beam would be dragging along the rails

[don9f]

An interesting discussion....it is also important to consider the wheel loading at each end of each axle. What you don’t want is a vehicle’s weight being carried in such a way that diagonally opposite wheels are “unloaded”....this can be a major factor in flange climb type derailments full size, influenced by spring/suspension setup, frame twist etc.

Don