Why is it not possible to get a 240 of Plain Bob Doubles with every different change occurring once at handstroke and once at backstroke? Such a 240 can be got with extra calls in addition to the bobs, but why not with bobs alone?

​

First, it is important to see how a normal 120 works. Each of the four possible 120s that use normal bobs are made up of three courses. These three courses can be described as starting with the lead ends 2345, 4235, 3425 (though 4235 and 3425 are sometimes rung backwards, in which case they start with 4325, 3245.)

​

Bobs are used to link the three courses together. We start in the plain course and the bobs add two more courses, and this is how we get our 120.

 

A 240 is made up of all six different courses, which can be described as starting from lead ends 2345, 4235, 3425, 2435, 4325, 3245. But because the groups of bobs can only ever add two courses, when we try to extend our 120 (which is three courses long) we can only get five courses. There is no way round this problem.

 

In 2014 I came up with this 240 of Bob Doubles, which is as close as you can get to a 240 with every change once at hand and once at back. It was a 'true' 220, made up to a 240, with 22 different backstroke lead ends and two repeated.

 

240 Plain Bob Doubles

  2345

  3524    2435

- 3542  - 2453

  5234    4325

- 5243  - 4352

  2354    3245

  3425    2534

  4532  - 2543

- 4523    5324

- 4532    3452

- 4523    4235

  5342  - 4253

  3254    2345

 

Composed on 26th August 2014, I'm sure that someone else will have come up with this before I did. The section with three bobs in a row is where the 220 had been extended to 240. That was the missing B-Block (bob course) rung in reverse.

 

Though I can't seem to find the figures, at about this same time I came up with a bobs-only 239 of Bob Doubles, which did have every change once at hand and once at back, except for Rounds which doesn't occur at backstroke, because the touch doesn't come round!

I'm sure I can't have been the first to have discovered this 239. Instead of ending in Rounds, you get either 4235, or 3425, depending on whether you call a bob there or not. This does mean, though, that the touch can be tripled to make a 720 in which every change occurs six times: thrice at handstroke, and thrice at backstroke. A three-part 720 by Mark Lynch does have this property, though I'm not sure whether it stems from the same 239 or not.

 

There are other 240s of Bob Doubles in which every change occurs twice, though of course not once at hand and once at back. These include the three 3-parts published by John Pladdys in the 1960s.

 

Interestingly there are some Plain Doubles methods not too dissimilar from Bob Doubles (in the respect that they have four leads in the plain course) where it is possible to get a 240 with every change once at hand and once at back. One example is Reverse Bob Doubles. These are the methods where the bob only affects two bells, rather than three, so the groups of bobs only ever add one course at a time (the bob is more like a single in this respect.) This makes it easy to add single courses until you get all the six different courses required for a 240 with every change once at hand and once at back.

 

480s of Bob Doubles and St Simon's with every change twice at hand, twice at back are possible. I came up with a 480 of Bob Doubles that was based on my 240, and another 480. These were composed on 2nd January 2019. The 480 of St Simon's was composed on 3rd January and is made up of B-Blocks rather than P-Blocks, so is distinctly different and cannot be called to Plain Bob:

 

480 Bob Doubles

RBP

2354 5

3452 2

4253 2

4235 1

2534 2

5432 2

5423 1

2543 4

5342 2

4532 4

5234 2

3524 4

3542 1

4352 4

3254 2

5324 4

3425 2

2345 4

Every change twice at hand, twice at back.

​

480 Bob Doubles

RBP

  3542 2

  5243 2

  4523 4

  4532 1

  4523 1

  2453 4

  5243 4

  3452 3

  5342 4

  2453 3

  4352 2

  5432 4

  5423 5

  2543 4

  4253 4

p 2345 1

Every change twice at hand, twice at back.

Extended from my 240

​

480 St Simon's Bob Doubles

by RBP

3542 2

2435 1

5324 1

3425 2

5234 1

5243 3

3452 1

4253 2

2354 2

4523 1

3245 1

5432 5

2354 1

4523 1

2453 4

3524 1

4235 1

2534 2

4325 1

5243 1

5234 3

4352 1

2543 1

5342 2

2453 1

3524 1

5423 2

3254 1

4532 1

2345 1

Every change twice at hand, twice at back.