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Working Dimensions and Tolerances

Working Dimensions and Tolerances

The numbers refer to the table on Track and Wheel Standards and correspond with those on the other pages in this section.working dimensions and tolerances

ScaleSeven Standard Dimensions

mm

in

1

Track gauge (straight track)

min

33.00

1.299

2

Gauge widening

max

0.45

0.018

3

Tyre width (loco)

min

3.16

0.124

 

Tyre width (loco)

max

3.26

0.128

 

Tyre width (coach and wagon)

min

2.90

0.118

 

Tyre width (coach and wagon)

max

3.00

0.118

4

Back-to-back

min

31.20

1.228

max

31.30

1.232

5

Effective flange

 

0.66

0.026

6

Back-to-back + one effective flange

min

31.86

1.254

max

31.96

1.258

7

Check rail gauge

min

31.98

1.259

max

32.08

1.263

8

Crossing flangeway (straight track)

min

1.00

0.039

max

1.08

0.043

9

Over check rail faces

min

30.85

1.215

max

31.08

1.224

10

Crossing flangeway – effective flange

min

0.34

0.013

max

0.42

0.017

         

Verification of Clearances

11

Minimum check rail gauge – (maximum back-to-back + one effective flange)

= 31.98 – (31.30+0.66)

= 0.02 minimum clearance

12

Minimum track gauge – (maximum back-to-back + two effective flanges)

= (31.30+1.32)

= 0.38 minimum clearance

13

Minimum back-to-back – maximum over check rail faces

= 31.20 – 31.08

= 0.12 minimum clearance

Tolerances

These standards define the manufacturing limits within which all ScaleSeven components are manufactured. From these limits the manufacturing tolerances are calculated, taking into account the component, the manufacturing process and the cost limit.

Wheel Position

The most dangerous situation occurs when the left-hand wheel has its back hard against the check rail when approaching the nose of the crossing vee. If the wheels are too far apart, or the check rail gauge is too small, then the right-hand flange will strike the nose of the crossing vee. Therefore, the minimum dimension 7 must never be less than the maximum for dimension 6, eg 31.98–31.96 gives 0.02 clearance. Since the effective flange is measured at a tangential point, see Wheel/Rail Relationships, the actual clearance is greater.

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