{"id":3337,"date":"2020-11-11T13:42:01","date_gmt":"2020-11-11T02:42:01","guid":{"rendered":"https:\/\/carcrank.org\/wordpress\/?p=3337"},"modified":"2020-11-11T13:46:35","modified_gmt":"2020-11-11T02:46:35","slug":"the-trigonometry-of-timing","status":"publish","type":"post","link":"https:\/\/carcrank.org\/wordpress\/?p=3337","title":{"rendered":"The trigonometry of timing"},"content":{"rendered":"\n

The Chummy has no visible timing marks unless you remove the \u201cbacon slicer\u201d starter motor that lives in the passenger compartment on top of the bellhousing, it\u2019s heavy and it\u2019s dark down there so not easy to do a quick timing check. Luckily the head has the spark plug holes in the right place to allow a dial gauge to check top dead centre (TDC) so if I knew what 8 degrees of crank rotation was in piston travel it would be good.<\/p>\n\n\n\n

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The App<\/figcaption><\/figure><\/div>\n\n\n\n

I was a terrible student, what I did retain was lost soon after the exams but I have been saved by technology, firstly spelling and now trigonometry as they say \u201cThere\u2019s an App for that\u201d and on my Android phone I use a free app called aptly \u201cRight Angle Triangle\u201d<\/p>\n\n\n\n

To cut a long story short, literally working on the back of an envelope there are 2 triangles in this calculation, the first one has a hypotenuse of half the stroke and the angle is 8 degrees, using my trusty triangle app I get the adjacent and opposite measurements. The second triangle is stacked on top with an hypotenuse of the distance between centres of the big and little ends on the conrod and the opposite side is the same as the first triangle\u2019s opposite side from that we get the adjacent measurement. Lastly add the two adjacent measurements together and subtract them from the sum of distance between centres of the big and little ends on the conrod and half the stroke and bingo we have 0.46 mm.<\/p>\n\n\n\n

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The Envelope<\/figcaption><\/figure><\/div>\n\n\n\n

So I zeroed the dial gauge at TDC disconnected the low tension lead to the distributor and connected my multimeter across the distributors LT terminal and earth, then cranked the motor (with the handle) and on the compression stroke the buzzing stopped at 0.45mm before TDC.<\/p>\n\n\n\n

A bit of a letdown really as my original guess was\u00a0 just about dead on so no easy jump in horsepower so back it tracking down the oil leaks of which there are many.<\/p>\n\n\n\n

As an aside this is the internet where everyone is an expert so feel free to shoot down my mathematics.<\/p>\n","protected":false},"excerpt":{"rendered":"

The Chummy has no visible timing marks unless you remove the \u201cbacon slicer\u201d starter motor that lives in the passenger compartment on top of the bellhousing, it\u2019s heavy and it\u2019s dark down there so not easy to do a quick … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[21],"tags":[],"class_list":["post-3337","post","type-post","status-publish","format-standard","hentry","category-austin-7-chummy"],"_links":{"self":[{"href":"https:\/\/carcrank.org\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/3337","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/carcrank.org\/wordpress\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/carcrank.org\/wordpress\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/carcrank.org\/wordpress\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/carcrank.org\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=3337"}],"version-history":[{"count":3,"href":"https:\/\/carcrank.org\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/3337\/revisions"}],"predecessor-version":[{"id":3347,"href":"https:\/\/carcrank.org\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/3337\/revisions\/3347"}],"wp:attachment":[{"href":"https:\/\/carcrank.org\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=3337"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/carcrank.org\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=3337"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/carcrank.org\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=3337"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}