SD APPLICATION NOTE 1
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and
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There is a subtle aspect of these calls that is sometimes misunderstood. The rims are the ends, and the hubs are the centers. The people who do the circulate or the <anything> are the original rims or hubs. First, a little background. These calls appear to have been originally intended for use in thars:
```
```
```                        3G>
3B<
4G^ 4BV 2B^ 2GV
1B>
1G<

3B>
2G<
4B^ 3GV 1G^ 2BV
4G>
1B<
```
```
```
When the formation is a thar, it is easier to see the analogy with a wheel. Each miniwave is a spoke of the wheel. The hub is the center, and the rim is the outside. At present, this call is most commonly used from waves. On a ‘rims trade back’, everyone does a trade, and then the original rims (ends) circulate. They are of course the centers after the trade. When the call is done from a tidal line, there is a convention that the centers and ends are determined in each 4-person line.
```             4B^  3GV  4G^  3BV  1B^  2GV  1G^  2BV
```

The boys are the rims and the girls are the hubs in this case. Why do we define it that way? The answer seems to be that the definition of “centers” and “ends” isn't well agreed-upon in a tidal setup in any case, and this definition seems to allow some popular and interesting applications. There is a lot of existing precedent for things like this:

```
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```             4B^  3GV  4G^  3BV  1B^  2GV  1G^  2BV

3BV            2BV
3G^     4GV    2G^     1GV
4B^            1B^
```
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```
When we go into columns, things get very interesting. The centers and ends do not change during a trade in columns. Therefore the common rule that ‘rims trade back’ means that everyone trades and then the centers circulate won't work. The original rims are still the new rims. So, on a ‘rims trade back’, everyone trades and then the new ends (who are the same as the original ends) circulate.
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```                  4B>   1B>   1G<   2G<

4G>   3G>   3B<   2B<

4B>   3G<   3B>   2G<

4G>   1B<   1G>   2B<
```

The ends traded and then circulated, finishing back where they began.

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When we apply the ‘yoyo’ concept, things get even more interesting:
```
```
```           4BV  3B^  3G^  4GV  2G^  1GV  1BV  2B^

4BV
1G>   1B<
4G^

2GV
3B>   3G<
2B^
```
```

```
Here is another example:
```
```
```                        1B<   3G>

2B>   4G<

2G>   4B<

1G<   3B>