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6498-1 or 2/ Cannon Pinion and Ampliture

smcchr00
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smcchr00 Member

smcchr00

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Hi All, 

I'm in a bit of a pickle. I have an ETA 6498 (Baylor) that I picked up off of ebay. I'm not sure how to tell whether or not this is a -1 or -2, with the only difference being beats per hour, 1 being the lower of the two.

When I run it on the timegrapher, it shows 18800 bph, which would indicate that it is a -1, but it's also currently running at low amplitude (around 220°). I assume that once I get the amplitude in order, this will increase the beat rate, so perhaps it is a -2? 

For some reason, I was thinking this was a -2 movement, with a 21k BPH, so I picked up a new seconds wheel (for a -2) with the extended pivot for the seconds hand. If this is indeed a 6498-1, would this wheel be causing low amplitude? I plan to stick the original wheel back in this weekend and do my own testing, but my thoughts are that the gearing is slightly different between the beat rates. 

Though the cannon pinion wouldn't effect the amplitude, I picked up a cannon pinion for the -2, with the higher beat rate. Would this cannon pinion be good to use on either version, or would it again be a slightly different gearing when engaged with the minute wheel?

Thank you for any help you can provide. 

Sean

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nickelsilver Distinguished Member

nickelsilver

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Count the teeth in the 4th wheel and escape wheel, and the leaves (teeth) on the escape pinion. Multply the number of teeth in the 4th wheel times the teeth on the escape wheel, times 2. Divide that by the number of leaves in the escape pinion. This is your beats per minute. Multiply by 60 for beats per hour.

I don't know the tooth count on that watch, but a typical one would be 70t 4th wheel 15t escape, 7L on escape pinion. 70x15x2/7 = 300, x 60 = 18,000.

Some watches with 21,600bph have 15t escape wheels, some with a higher count. Again, I don't know on this caliber but I think it's 15, so to make it work with 21,600 they usually modify the 4th wheel and escape pinion, keeping all else the same. Here if they went to 72t 4th wheel, and 6L esc pinion, you have 72x15x2/6 =360, x60 =21,600.

You said you're reading 18,800, seems your hairspring might be sticky or caught on something.

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meanoldmanning Watch Enthusiast

meanoldmanning

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I doubt an old Baylor is going to have a -2. If it’s running at 18,000 I think that’s what it’s going to run at regardless of amplitude.

 

Iirc there are several different parts between the -1 and -2: the balance wheel is smaller diameter on the -2, the barrel, 4th wheel escape wheel etc. have different teeth counts.

 

 

Sent from my iPhone using Tapatalk

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smcchr00 Member

smcchr00

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3 hours ago, nickelsilver said:

Count the teeth in the 4th wheel and escape wheel, and the leaves (teeth) on the escape pinion. Multply the number of teeth in the 4th wheel times the teeth on the escape wheel, times 2. Divide that by the number of leaves in the escape pinion. This is your beats per minute. Multiply by 60 for beats per hour.

I don't know the tooth count on that watch, but a typical one would be 70t 4th wheel 15t escape, 7L on escape pinion. 70x15x2/7 = 300, x 60 = 18,000.

Some watches with 21,600bph have 15t escape wheels, some with a higher count. Again, I don't know on this caliber but I think it's 15, so to make it work with 21,600 they usually modify the 4th wheel and escape pinion, keeping all else the same. Here if they went to 72t 4th wheel, and 6L esc pinion, you have 72x15x2/6 =360, x60 =21,600.

You said you're reading 18,800, seems your hairspring might be sticky or caught on something.

Checked the gears and you were correct; 70 15 and 7, so it's a 6498-1. Thanks again!

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