David Davis Posted October 20, 2021 Share Posted October 20, 2021 A gentleman in the USA, having seen my Big Guff photographed in flight, has offered me a Brown Junior Type D together with a coil, condenser and HT cable for the cost of the postage to my home. I've decided to take up his offer. The Brown Junior a 10cc side port petrol two-stroke was the first successful model aeroplane engine to be produced and was fitted to the original Good Brothers' Big Guff in 1938. I have never owned a "sparky," so bring a wealth of inexperience to the project. The closest experience I can offer is when I competed in Pre 65 motor cycle trials on a magneto equipped BSA Bantam! Consequently I have a number of questions. 1. What sort of battery is required? 2. Where can I find a wiring diagram? 3. The original plug and points system seems to work satisfactorily but I believe that modern transistorised ignition systems are available for these old engines. Where can one buy one and what advantages do they offer? 4. I am aware that the Brown Junior is not fitted with an R/C carburetter as fitted to modern engines but that it is capable of operating at a wide speed range by adjusting the ignition timing and fuel mixture. The Big Guff is currently fitted with a Laser 62 turning a 14 x 4 propeller and straight and level flight is achieved just above tick-over. I plan to adjust the engine so that it is turning over at 3000-4000 rpm which I guess is about the same rpm as the Laser throttled down, before releasing the model. Any opinions? 4. I would like to have a remote control throttle-cut so that if the engine was not developing sufficient power to allow take off I could abort the take-off before the model careered into the long grass. Is this possible? I am not expecting the engine for at least two weeks and doubtless will have further questions when it arrives. Happy Landings Gentlemen. 1 Quote Link to comment Share on other sites More sharing options...
Geoff S Posted October 20, 2021 Share Posted October 20, 2021 Despite being just about 100% electric as far as flying goes, engines interest me, particularly old ones like this. If you use electronic ignition then organising an engine cut shouldn't be too difficult using an electronically controlled switch on the battery supply but as for the rest - I'll be watching and learning along with you. Geoff Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted October 20, 2021 Share Posted October 20, 2021 Bit of info here, 3v coil so 2 NiMh cells should do the job. Quote Link to comment Share on other sites More sharing options...
PatMc Posted October 20, 2021 Share Posted October 20, 2021 Peter Chinn's engine detailed engine test from 1957 here. Quote Link to comment Share on other sites More sharing options...
John Wagg Posted October 20, 2021 Share Posted October 20, 2021 (edited) 3 hours ago, Bob Cotsford said: Bit of info here, 3v coil so 2 NiMh cells should do the job. Or one Lipo' or would 3.7v be to much ? Edited October 20, 2021 by John Wagg Quote Link to comment Share on other sites More sharing options...
David Davis Posted October 21, 2021 Author Share Posted October 21, 2021 I'm told that i need a "servo operated micro switch" in order to be able to turn the ignition off in flight. I've never even seen one! What do they look like and where can I buy one from? Quote Link to comment Share on other sites More sharing options...
Don Fry Posted October 21, 2021 Share Posted October 21, 2021 (edited) eBay, or any supplier. Cheap, couple of euro. You need a low voltage miniature one, but in that bus, a mains voltage one will do. Ask a club mate, they aren’t rare. Once you see it, you will immediately realize how a small servo will switch it. Edited October 21, 2021 by Don Fry Quote Link to comment Share on other sites More sharing options...
Alan H Posted October 21, 2021 Share Posted October 21, 2021 (edited) This period wiring diagram might help you. Capacitor is not critical, 0.1uF 250V or thereabouts. Substitute a servo operated microswitch for the flight timer. Edited October 21, 2021 by Alan H Quote Link to comment Share on other sites More sharing options...
Sparks Posted October 21, 2021 Share Posted October 21, 2021 Hi David, Here is an example of a servo operated micro switch. No doubt you could make your own bracket from a small piece of ali sheet. Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted October 21, 2021 Share Posted October 21, 2021 Have look at "Sceptre Flight " engine tests. They list a BrownJunior model D from 1938 tested and reviewed by Peter Chinn in 1958. An excellent site for engine enthusiuasts . Quote Link to comment Share on other sites More sharing options...
PatMc Posted October 21, 2021 Share Posted October 21, 2021 27 minutes ago, Engine Doctor said: Have look at "Sceptre Flight " engine tests. They list a BrownJunior model D from 1938 tested and reviewed by Peter Chinn in 1958. An excellent site for engine enthusiuasts . I think you'll find it was 1957. ? 22 hours ago, PatMc said: Peter Chinn's engine detailed engine test from 1957 here. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted October 21, 2021 Share Posted October 21, 2021 Nice example of a simple home built switch courtesy of Jon Harper. Quote Link to comment Share on other sites More sharing options...
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