{"id":9,"date":"2014-04-02T15:37:00","date_gmt":"2014-04-02T14:37:00","guid":{"rendered":""},"modified":"2025-06-09T13:10:07","modified_gmt":"2025-06-09T12:10:07","slug":"modifying-servos-for-continuous-rotation","status":"publish","type":"post","link":"https:\/\/blog.hslracing.com\/rcmodels\/2014\/04\/modifying-servos-for-continuous-rotation.html","title":{"rendered":"Modifying servos for continuous rotation"},"content":{"rendered":"

My son was thrilled by the “Super Ant Weight” (250g) Sumo Robot that he helped build and fight at the\u00a0Robot Wars<\/a>\u00a0stand at the\u00a0Model Engineering Exhibition<\/a>\u00a0at\u00a0Alexandra Palace<\/a>\u00a0earlier this year – he was beaming from ear to ear when his robot won first place overall out of 4 robots, 3 battles each round to determine the winner.<\/p>\n

I had a look at what was involved in making one and it looked pretty straightforward – a battery pack, a receiver and 2 servos converted to continuous rotation.<\/p>\n

He has been pestering me ever since to buy the items so he can make one, so with my last Hobby King<\/a> order, I finally ordered the parts.<\/p>\n

First off a 4 x AA battery holder <\/a>\u00a0at\u00a0$1.44,<\/p>\n

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then a couple of HK15138 standard analog servos<\/a> at $3.25 each<\/p>\n

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I already had a few OrangeRx R615 receivers<\/a> for which I paid $6.99 each<\/p>\n

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I actually bought these from the EU Warehouse because the UK Warehouse is almost permanently out of stock and the EU warehouse happened to have some.<\/div>\n
<\/div>\n
Next up the servos need modifying for continuous rotation.<\/div>\n
<\/div>\n
First unscrew the 4 screws and pull\/push off the top cover.<\/div>\n
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Remove the final drive gear<\/div>\n
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Close-up of drive gear with tab still attached.<\/p>\n

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Close-up of drive gear with tab removed.<\/p>\n

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I used a sharp knife to remove the tab, the two cuts took just a few seconds.<\/p>\n

Close-up of the rear of the drive gear showing where the potentiometer attaches.<\/p>\n

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Close-up of the same gear once this area has been drilled out with a 4mm drill.<\/p>\n

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I used a battery powered hand drill and just held the gear in my other hand with some tissue paper to stop it slipping or collecting any dirt.<\/p>\n

Gears re-installed and checking the central position with a servo tester<\/a>\u00a0($5.82 from\u00a0Hobby King<\/a>).<\/p>\n

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This step is not essential and can be done by eye, or simply left at the factory setting.<\/p>\n

With this tester minimum rotation is 70 degrees, maximum is 230 degrees, so the central point should be 150 degrees, however the transmitter still moves the servos with this as a mid point, so I set it at 149 degrees, which is also how the servo comes straight from the factory.<\/p>\n

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All the parts connected together for an “Super Ant Weight” Sumo robot, total weight including batteries is 198g, so 52g still available for cardboard body and decoration.<\/div>\n
<\/div>\n
You drive the robot like a tank, so each servo is on a different stick. Both up for forwards, both down for reverse, left up and right down for right, right up and left down for left, both in the middle to stop.<\/div>\n
<\/div>\n
All that is left now is to mount the items on a board and make some cardboard wheels to attach to the servo horns and we are ready to go.<\/div>\n
<\/div>\n
In all the cost of parts is $14.93 ($1.44 + 2 * $3.25 + $6.99) or just under \u00a39.00, well worth it in my opinion for hours of fun for children of all ages.<\/div>\n
<\/div>\n
The most expensive part will be the transmitter, although you can pick up a new\u00a0Devo 7E<\/a> for under \u00a340.00 on ebay<\/a> from China, that can then be flashed with the deviationtx<\/a> firmware.<\/div>\n
<\/div>\n
Just create a new model on the receiver set the transmitter type to DSM2<\/a>\u00a06 channel, disable the channels you are not using (I am just using Throttle for the left stick and Elevator for the right stick), bind to the\u00a0OrangeRx R615 receiver<\/a>\u00a0and you are good to go.<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

My son was thrilled by the “Super Ant Weight” (250g) Sumo Robot that he helped build and fight at the\u00a0Robot Wars\u00a0stand at the\u00a0Model Engineering Exhibition\u00a0at\u00a0Alexandra Palace\u00a0earlier this year – he was beaming from ear to ear when his robot won first place overall out of 4 robots, 3 battles each round to determine the winner.…<\/p>\n","protected":false},"author":1,"featured_media":30,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-9","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-uncategorised"],"_links":{"self":[{"href":"https:\/\/blog.hslracing.com\/rcmodels\/wp-json\/wp\/v2\/posts\/9","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.hslracing.com\/rcmodels\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.hslracing.com\/rcmodels\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.hslracing.com\/rcmodels\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.hslracing.com\/rcmodels\/wp-json\/wp\/v2\/comments?post=9"}],"version-history":[{"count":4,"href":"https:\/\/blog.hslracing.com\/rcmodels\/wp-json\/wp\/v2\/posts\/9\/revisions"}],"predecessor-version":[{"id":84,"href":"https:\/\/blog.hslracing.com\/rcmodels\/wp-json\/wp\/v2\/posts\/9\/revisions\/84"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blog.hslracing.com\/rcmodels\/wp-json\/wp\/v2\/media\/30"}],"wp:attachment":[{"href":"https:\/\/blog.hslracing.com\/rcmodels\/wp-json\/wp\/v2\/media?parent=9"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.hslracing.com\/rcmodels\/wp-json\/wp\/v2\/categories?post=9"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.hslracing.com\/rcmodels\/wp-json\/wp\/v2\/tags?post=9"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}