Operation Grasshopper escapement

-


animation of grasshopper escapement in motion. shows modified version has counterweighted pallet arms , spring stops.


harrison developed grasshopper escapement conventional anchor escapement built turret clock go in stable block @ brocklesby park in lincolnshire. proved unreliable, needing repeated attention harrison inconvenienced, around 1722 modified escapement putting hinge in middle of each arm of anchor. hinged pallets both pointed same way, opposing rotation of escape wheel. escape wheel pushes pallet, hinge moves away escape wheel. pallet pivots contact point wheel pushes anchor. @ same time, other pallet approaching wheel. when contacts wheel, pushes backwards , contact between wheel , first pallet broken. both pallets tail-heavy naturally tend move away wheel. first pallet therefore moves out of path of escape wheel , job of impulsing pendulum passes second pallet.


the first pallet comes rest against stop holds in correct position when pendulum reaching end of travel, pushed second pallet, first pallet swings down path of wheel again. makes contact wheel and, driven momentum of pendulum, pushes wheel backwards slightly. releases second pallet, retires gracefully stop, having transferred task of impulsing pendulum first pallet again. small movement of pallet on hinge involves far less friction sliding contact in conventional escapement; needs no lubrication , there little wear harrison able make pallets wood. 1 of original pallets @ brocklesby park still working when clock renovated in 2005 while other replaced following accident in 1880. harrison later modified layout of escapement having 1 pallet pull rather push, putting little hook @ end of pivoted arm contact teeth of escape wheel. put both hinge axes on common pin.


when pallet pushing escape wheel backwards being driven hard against stop. prevent wear, or damage, stops designed give way. each stop hinged same axis pallet. pallets tail-heavy stops nose-heavy, tending fall towards wheel. stops sufficiently nose-heavy combination of pallet plus stop tends fall towards wheel prevented fixed pin on anchor. means pin holds stop holds pallet in right place engage cleanly escape wheel. when pallet meets wheel, pushes wheel backwards , lifts stop off pin. when wheel pushes pallet, stop comes down onto pin , parts company pallet. each stop lifted off pin once in each cycle momentum of arriving pallet.








Comments

Post a Comment

Popular posts from this blog

Independence United Arab Emirates

-
historic photo depicting first hoisting of united arab emirates flag rulers of emirates @ union house, dubai on 2nd of december 1971. zayed bin sultan al nahyan first president of united arab emirates , recognized father of nation. by 1966, had become clear british government no longer afford administer , protect united arab emirates. british mps debated preparedness of royal navy defend sheikhdoms. secretary of state defence denis healey reported british armed forces overstretched , in respects dangerously under-equipped defend sheikhdoms. on 24 january 1968, british prime minister harold wilson announced government s decision, reaffirmed in march 1971 prime minister edward heath end treaty relationships 7 trucial sheikhdoms, had been, bahrain , qatar, under british protection. days after announcement, ruler of abu dhabi, sheikh zayed bin sultan al nahyan, fearing vulnerability, tried persuade british honour protection treaties offering pay full costs of keeping british armed forces i
Read more

History Alexandra College

-
alexandra college (on right) circa 1890 the school founded in 1866 , takes name princess alexandra of denmark, school s patron. school colours, red , white, adopted danish flag in honour. alexandra college founded anne jellicoe, quaker educationist, in name of furthering women s education. under anne jellicoe, school grew small establishment focused on providing governess-style education irish protestant ladies pioneering force women s rights , education, providing education women equivalent available in boys schools, grounding in mathematics, history, classics , philosophy. alexandra settled role, anne jellicoe convinced major obstacle liberal education of women exclusion university campus. passionately believed until women admitted trinity college dublin (founded in 1592), voice of women not commonly heard in politics, literature or in academic debate. the royal university of ireland act 1879 allowed females take university degrees on same basis males. students prepared examination
Read more

Management School of Computer Science, University of Manchester

-
^ anon (2010). dai edwards: helping turing use manchester mark 1 . www.bl.uk. british library.  ^ anon (2014). voices of science: david dai edwards. born david beverley george edwards, 1928 . www.bl.uk. british library. archived original on 2014-01-16.  ^ kilburn, t. (1951). new universal digital computing machine @ university of manchester . nature. 168 (4264): 95. doi:10.1038/168095a0.  ^ lavington, simon (2001). obituary: tom kilburn (1921–2001) . nature. 409 (6823): 996. doi:10.1038/35059201. pmid 11241994. 
Read more