How did they make this in the 1800's?!

Video Description

As if making the escape wheel, the very heart of the chronometer escapement is not normally hard enough, the Arnold type adds a whole new layer of difficulty. Welcome to this video covering the manufacture of a replacement escape wheel for a John Roger Arnold marine chronometer. The marine chronometer was developed heavily in the late 18th century and gradually settled into a pretty standardised form, but in the lead up to that various makers were inventing new improvements to increase accuracy, reliability and ease of manufacture. J R Arnold led on from his fathers pioneering work, but continued to use a form of escapement designed by his father. Although his father invented the pivoted detent, as the innovation of Earnshaw's 'spring detent' took hold J R Arnold used a spring detent, but continued with his father's very clever 'cycloidal' impulse type of escape wheel. The main difference between the two styles is that the detent unlocks the wheel whilst moving towards the centre, rather than outwards as with Earnshaw and what became standardised practice. The impulse delivery is also very different with the Arnold style transferring impulse to the balance via a cycloidal curved tooth that rolls smoothly along the impulse face of the roller. The issue with the Arnold system is that it is prone to wear a notch in the tooth as it drops which can over time lead to reliability issues. The Arnold type wheel is also much harder to make, having a curved face, and a relief cut to consider. In this video I make a replacement wheel as part of a large restoration project. Follow along with all my projects by subscribing to my channel and following me on Instagram @tommy.jobson If you feel willing and able to support me making these videos I also have a Patreon page: https://www.patreon.com/c/tommyjobson Please do consider becoming a Patron as for as little as the price of a coffee each month you will be able to help support me as I move towards my goal of building a horological masterpiece for all to see here on YouTube. Thank you! My main website is: www.tommyjobson.co.uk Thanks for watching! Tommy. Video Content: 0:00 - Intro 0:44 - Arnold Escapement 1:50 - Planning the work 2:56 - Preparing the material 3:23 - Taking measurements 4:10 - Machining the blank 4:48 - Machine set-up 6:00 - Making the first cut 7:09 - Changing material 9:05 - Second cut 10:10 - Cycloidal cut 13:20 - Machining the centre 13:50 - Cutting the face cut 14:50 - Parting off and facing 15:50 - Crossing jig 22:20 - Crossing out 24:09 - Competed wheel 25:04 - Testing the impulse 27:25 - Completed and running