EM gauge: increasing B2B

[philsandy]

I have one loco (Bachmann 4MT tank) whose wheels occasionally bind when negotiating the check/wing rails of a 36"/28" radius curved point . I know these radii are a bit on the tight side for EM gauge, but all my locos are fine going round it.

The B2B are set at 16.5 mm. My question is, would slightly increasing the B2B to say 16.6 or 16.7mm. on this particular loco cure the problem?

[Mark Forrest]

Difficult to say for certain, but probably worth a try. What wheels are you using?

[Enterprisingwestern]

Depends which wheels you are using.

Pedantically it's not the B to B measurement that ultimately regulates smoothness of transition through pointwork.

How does the wheelbase compare to oyher loco's, and what "slop" is there in the centre axle?

 

Mike.

[philsandy]

Difficult to say for certain, but probably worth a try. What wheels are you using?

 

Depends which wheels you are using.

Pedantically it's not the B to B measurement that ultimately regulates smoothness of transition through pointwork.

How does the wheelbase compare to oyher loco's, and what "slop" is there in the centre axle?

 

Mike.

 

I have used the original Bachmann wheels after reducing the flange widths to 0.5mm.  I have also done this with 2 other locos.

The wheel base is virtually the same as the locos, and there is plenty of sideways movement on the axles, approx. 1.5mm on the centre and 1mm on the other 2.

As I said It does not always bind, and it is only slightly, but noticeable.,

When it does, I have lifted it off the track to inspect , when replaced back and I send it through again it's fine..ie. the wheels are now at a different position in relation to the "binding " point.

[Mark Forrest]

Could there be any misalignment of wheel to axle? If they aren't on squarely you'll end up with a back to back measurement that varies as the wheels rotate, which might give the sort of intermittent fault that you are seeing.

[Happy Hippo]

Our EM area group started working with 16.5mm  but gradually, after some experimentation, are moving over to 16.75mm b2b on all our stock.

 

We have had no problems with either b2b setting when running through the points and crossings using the EMGS gauges.

 

If anything, the stock  seems to ride more smoothly through points and crossings when set to the wider b2b..

[t-b-g]

I would check the dimensions on the point work carefully first. When you are working with a small radius, you need a good curve through the point as any "straight" bits mean that the radius elsewhere has to be even tighter. The gap between rail and check rail needs to be pretty accurate too.

 

Some RTR wheels will open up to EM and run just fine but others have quite thick flanges and will struggle to get through the EM 1mm check rail gap even on a large radius. So that is worth looking into.

 

If possible, hold the loco with one end raised clear of the track and just push one set of wheels go though the point. If it jams, have a look and see if it is against the checkrails (in which case the check rails might need moving slightly or the B to B might need opening up.

 

With modern wheels, such as Ultrascale and Gibson (and with older but fine wheels like Sharman's) a B to B of 16.7 or thereabouts is quite practical and works well. I do know that the EMGS were having some discussions about updating standards now that most people have better wheels but I don't know how these talks went.