Jim Burton 1 Posted September 16, 2011 Author Share Posted September 16, 2011 Yes, I think a trip to the Modelling Shop to inspect the spinner design rather than 'buying blind' on the internet might be safer - I could then match backplate to prop. TT recommendation for props for the 54 are shown below - I'm running in on the 11x5, I have a couple of 11x6s and the 12x7 is there for comparison if I need it: 'scale' as described = slow and steady I assume, and with my piloting skills that will be just fine by me. Thanks to all for humouring my 'paranoia' - or 'pursuit of wisdom and truth' as I prefer to term it! Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted September 16, 2011 Share Posted September 16, 2011 Blimey a 12 x 8 on a 54 4 stroke.... That's a darn big prop.......I suspect if you used that you might need to lower the compression ratio a touch to prevent pre-ignition...... (blue touch paper now well & truly alight he retires to a safe distance...) Quote Link to comment Share on other sites More sharing options...
Shaunie Posted September 30, 2011 Share Posted September 30, 2011 Here's my tuppence worth. I don't believe the lock nut system on fourstrokes is there to keep the prop tight, ultimately I think it is there to keep the prop ON. I too have seen a fourstroke throw its prop off. Early O.S 61 FS if I remember correctly. Reminds me of the real reason why we use spinners, it's somewhere to find the prop nut when this happens. I would rather the prop came loose if the engine kicks back rather damage the engine. I feel that the cause of engine kick-back is ultimately an operator error, good mixture control should almost completely prevent it occurring. The problem is that there is a danger point at both ends of the mixture window, detonation if excessively lean and the twin spectres of pre-ignition and hydraulic lock at the rich end. Excessively rich mixture reduces headspace at TDC due to incompressibilty of the fuel this increases effective compression which will advance the ignition point and as a result cause pre-ignition. Personally I am not a fan of excessively rich mixtures for running-in, a couple of clicks maybe and then manage the heat build up by sympathetic throttle handling. Another point that has not been discussed here is starting method. I have an O.S 40 FS (which is the only FS I am using at the moment) but I never put an electric conrod bender on it. I prime the engine until it is nicely wet and floppy turn it anti-clockwise until I feel compression then smartly snap the engine over backwards by flicking the spinner, rather like snapping your fingers. Get it right and the engine just bumps into compression backwards, backfires, changes direction and promptly starts itself! I use this method on two strokes too. I have just run-in a TT Pro 46, primed it up and started first flick using this method from brand new. The only time I ever put my finger through the prop is priming. The only proviso is it does not work well on tired (or very hot) engines. Shaun Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted September 30, 2011 Share Posted September 30, 2011 Posted by Steve Hargreaves on 16/09/2011 14:57:13:Blimey a 12 x 8 on a 54 4 stroke.... That's a darn big prop.......I suspect if you used that you might need to lower the compression ratio a touch to prevent pre-ignition...... (blue touch paper now well & truly alight he retires to a safe distance...) erm, I'm running a 13*6 on my SC52 and a 13*7 on an OS48 Surpass in the Eros and they run just fine Quote Link to comment Share on other sites More sharing options...
Matt Theron Posted October 13, 2011 Share Posted October 13, 2011 Hi Folks, I hope this is the right place to go a begging. I am in need of a back plate for a Thunder Tiger 54 four stroke and do not want to pay the price of a new engine to replace it ............... can anyone help please? Cheers Matt Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted October 13, 2011 Share Posted October 13, 2011 Why would you need a whole new engine?? Or are you saying that the cost of a spare backplate is nearly the same as a new engine ?? Amerang are the importers of TT motors....they would be the ones to ask for spare parts....or else this chap might be able to help.... There is a "begging section" just here where you might find a second hand one.... Quote Link to comment Share on other sites More sharing options...
Matt Theron Posted October 13, 2011 Share Posted October 13, 2011 Hi Steve, Thanks for the info ........and I meant as a joke that the cost of a spare backplate is nearly the same as that of a new engine . I would rather prefer to obtain a second hand one though . Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted October 13, 2011 Share Posted October 13, 2011 Are you sure they are that expensive Matt....? I've just checked the rear cover for an SC52 & they are £6.65 each ....so you could buy quite a few for the cost of a new engine..... Might be worth checking with Amerang.....TT motors are not that common...in fact I've never seen one at our club.... so you might struggle to find a second hand one.... Quote Link to comment Share on other sites More sharing options...
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