Jack Banner Posted December 24, 2014 Share Posted December 24, 2014 Hi all, I am installing a well run in ASP 61 FS into a plane I am re-fitting. I want a metal spinner on it to match the cowl but have an issue. The drive shaft is not long enough to take the spinner back plate, prop, prop washer, main nut, lock nut and spinner nut all together. Ideally (to prevent a thrown prop in case of backfire) I should include the lock nut, as below (tightened up of course): However, can I have opinions on it being safe to run as below? (with the spinner bolted on of course). The alloy spinner nut has a good 10mm of prop shaft to hold onto and is tight. Arranged like this I can fit the spinner and tighten it up with the M4 bolt no problem. Is it safe though? I personally think it is OK but am really looking for some re-assurance. All help appreciated. Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted December 24, 2014 Share Posted December 24, 2014 Take the corners of the locknut so it fits inside first nut as the original would John Quote Link to comment Share on other sites More sharing options...
J D 8 Posted December 24, 2014 Share Posted December 24, 2014 Using two plane nuts to secure an item is a well known method.however on model engines the second nut has a taper and a split that compresses onto the shaft as it is tightened for extra security.many older engines did not have this but they still worked.[more chance of a prop spin off with a backfire]My Laser 150 has only one nut.For extra security you could use thredlock. Edited By john davies 8 on 24/12/2014 22:31:36 Quote Link to comment Share on other sites More sharing options...
J D 8 Posted December 24, 2014 Share Posted December 24, 2014 Unless you have the means to put the correct taper on the nut I would not go with john stones suggestion. Quote Link to comment Share on other sites More sharing options...
Andy Shailer Posted December 24, 2014 Share Posted December 24, 2014 Hi Jack, I have a plane with a .61 on the front with the same problem, its been set it up as your 2nd picture and I have had no problem what so ever and it been like that for 3 years! Andy Edited By Andy Shailer on 24/12/2014 22:37:04 Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted December 25, 2014 Share Posted December 25, 2014 It's a nut with a taper not Quantum Physics John Quote Link to comment Share on other sites More sharing options...
Chris Barlow Posted December 25, 2014 Share Posted December 25, 2014 I had the same problem with my Vmar Tomahawk and fitted the prop and spinner the same way and as John said I filed a chamfer onto the spinner adapter to fit inside the prop nut. Nice and easy as it's only plated brass nut! As a little more security I also used some blue threadlock and haven't had a problem with it throwing props or loosening off yet.. Quote Link to comment Share on other sites More sharing options...
Luke Lane Posted December 25, 2014 Share Posted December 25, 2014 Hi Jack, Just Engines stock the correct item. Ref: JW 0308 Steel Locking Adapter for four strokes. Hope this helps. Regards, Luke. Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted December 25, 2014 Share Posted December 25, 2014 You should be fine. Just tighten the nuts up really well. I would be tempted to replace the original inner nut with a normal type to give more friction area rather than rely on the rim of the recessed original nut.. I have had people whose props have spun off. I find that they do not tighten the nuts properly. Really heave on long spanners. IT seems that they were afraid of snapping the crankshaft!!!! Model Fixings also to special friction washers which you could use as belt and braces. Quote Link to comment Share on other sites More sharing options...
Paul Marsh Posted December 25, 2014 Share Posted December 25, 2014 I have several models where I didn't use the locking nut due to having to do the above. I know, 'cause I have a drawer full of locking nuts and many planes with ali spinners on them. To date not had a problem with any of them, apart from a couple using domed spinners, where I could only use the dome nut only. The better ones of them, mainly for larger engines is where a hollow is machined out, allowing a nut inside the dome spinner. Quote Link to comment Share on other sites More sharing options...
Peter Beeney Posted December 25, 2014 Share Posted December 25, 2014 Jack, I have a colleague that runs a four stroke with exactly your arrangement and his has been ok; but having said that he’s never had an incident of engine detonation to test it. When the engine is running normally the prop nut will constantly be tightened by the engine’s motion, it will never become undone, but if it stops suddenly, (cause - detonation!), the energy in the fast moving prop will cause it to unwind, often in quite a spectacular manner, it can fly forward a fair distance at speed. Also engine starters, when they are in good form, can spin off the prop because the starter is trying to undo the nut, again at fairly high speed and usually across the pits area; but this can apply to two stokes as well. So it’s quite important to makes sure the prop nut(s) are as tight as possible in the first instance. One small point, detonation will only generally occur when the engine is running near/at flat out. Thus it really is seriously a good idea to never ever stand in front of a running engine under any circumstances, that is your good self or anyone else. A locknut, of any sort, probably helps, but it’s still no guarantee, I’ve seen one instance where the clinch type lock nut, as in photo 1, was taken straight off as well, just as if it wasn’t on, and I’ve heard of other similar cases. And there was a case reported that someone was quite badly hurt when he was standing in front of a running four stoke. He open the throttle and ‘bang’, the prop buried itself in his thigh, and the spinner cone made a hole in his chest. This was a few years ago, now. Therefore provided I always took note of my own advice, and that’s not always a certain thing I have to admit, I would be quite happy to run your installation as it is. I believe Laser engines have a wedge shaped combustion chamber, which very much helps to prevent detonation; and I suppose in theory that the prop could be thrown off if the throttle was shut quickly enough. But for a variety of reasons the engine progressively slows down, so I’d think this an unlikely event; although it might happen with electric motors in some circumstances. PB Quote Link to comment Share on other sites More sharing options...
Former Member Posted December 25, 2014 Share Posted December 25, 2014 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted December 25, 2014 Share Posted December 25, 2014 Hi if you know anyone who has a lathe ask them to turn the end of the spinner but to match the original lock but. I regularly turn them on my models for added safety. If your stuck pm me and I will turn it for you . E.D. Quote Link to comment Share on other sites More sharing options...
Paul Marsh Posted December 25, 2014 Share Posted December 25, 2014 I had a laser 80 backfire in the air, and the prop/dome nut span off. No engine is immune to back-firing, just how intense it it. Had my OS 91FS backfire in my old Jamara mustang, and if loosened the nut, seemed to keep it contained. I got the AT-6 down minus the prop/ spinner, probably buried in Langar's surrounding field now... Quote Link to comment Share on other sites More sharing options...
Mark a Posted December 25, 2014 Share Posted December 25, 2014 Hi Jack I've run the exact same set up as you on my Wot XL running a ASP1.20fs with no problems at all just make sure its all tight and you will be fine. Mark. Quote Link to comment Share on other sites More sharing options...
Jon H Posted December 25, 2014 Share Posted December 25, 2014 i never use a locknut on my 4 strokes and they are perfectly fine, they never throw props. Just nip it up and crack on Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted December 26, 2014 Share Posted December 26, 2014 Never say never ! Some years ago I had a large dent made in my caravan when a prop and spinner came off a 120 that was running very nicely . Warning signs /sound were too quick to react to and prop and spinner smashed into my caravan parked in front of my garage. Quote Link to comment Share on other sites More sharing options...
Jack Banner Posted December 26, 2014 Author Share Posted December 26, 2014 Hey all, thanks for the replies and advise. I will probably run as is, with some threadless, and have a look at the just engines product. Happy Christmas all! Quote Link to comment Share on other sites More sharing options...
William Morrison Posted January 2, 2015 Share Posted January 2, 2015 You will do fine as is. Just make sure you really put the torque to the first nut. I do it all the time with not issues. Besides you will have a cone to collect the nuts if they should come loose. Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted January 7, 2015 Share Posted January 7, 2015 Agree with the others...this set up will be fine...I have several engines running just like this. I would however suggest the fitment of a plain washer between the two nuts to prevent the adaptor corners galling the internal surface of the prop nut..... Quote Link to comment Share on other sites More sharing options...
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