Delta Whiskey Posted February 3, 2009 Share Posted February 3, 2009 I have what looks like an OS 52 FS fitted in a Super Chipmunk I brought recently, and I wanted to remove the cowl to check on the engine, and lenghten the fuel filler tube, but I cannot seem to get the prop off ! It has a locking nut that screws inside the main nut, the locking nut comes undone easily enough, but if I try to undo the main nut, the engine turns over as I can see the spindle turning. I've tried putting the locking nut back on, and but the spindle will still turn. Any ideas, or is it a duff engine giving little or no compression to resist agaisnt ? Quote Link to comment Share on other sites More sharing options...
Bruce Richards Posted February 3, 2009 Share Posted February 3, 2009 Your engine is probably fine. You need to lock up the engine some how. You could try taking out the glow plug and putting a piece of wood through the plug hole the resist the movement of the piston. But be careful not to use too much force in case you damage something or break the wood inside the engine. You can buy specially made tools to lock up the engine but try the wood first. The nut should come loose quite quickly, hold the prop and the spinner back plate with one hand and turn the nut with the spanner in the other. Hope this helps Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted February 3, 2009 Share Posted February 3, 2009 Before you start stuffing bits of wood anywhere, slipping prop nuts usually respond to holding the prop with one hand, putting a well fitting (preferably ring) spanner on the nut (steady the spanner with a spare finger) and giving the spanner a sharp tap with something reasonably hard and heavy... This is quite a common problem with cheap hard plastic spinners. Quote Link to comment Share on other sites More sharing options...
Delta Whiskey Posted February 3, 2009 Author Share Posted February 3, 2009 Thanks, I'll see if I can find a suitable strong enough piece of wood, though as its a small diameter, I hope it will hold! My LHS was useless, they said they did not even know of a stop / lock tool ! Quote Link to comment Share on other sites More sharing options...
Delta Whiskey Posted February 3, 2009 Author Share Posted February 3, 2009 I'll try Martins suggestion too first ! Quote Link to comment Share on other sites More sharing options...
Hamish Posted February 3, 2009 Share Posted February 3, 2009 Try pulling on one side of the prop to hold the shaft while you turn Quote Link to comment Share on other sites More sharing options...
Myron Beaumont Posted February 3, 2009 Share Posted February 3, 2009 Must agree with Martin --Destroy the prop if you have to if shock treatment doesn't work -BUT It should ---Cheaper than engine internals I'm sure Think of the stresses you could cause inside that beautifully made engine ! compared with another prop ? Myself I have a few "pullers "I've made for exactly this sort of situation .The prop boss was probably not drilled correctly and over time under compression has "grown" onto the propshaft . Quote Link to comment Share on other sites More sharing options...
Mark Lubbock Posted February 3, 2009 Share Posted February 3, 2009 If you do need to 'lock' the engine, it is much better to flood the cylinder with fuel than sticking things through the plug hole, exhaust on a two stroke etc. This spreads the load across the whole piston surface. You shouldn't need too much force to undo the nut & better than pliers on the prop driver etc. Quote Link to comment Share on other sites More sharing options...
Delta Whiskey Posted February 3, 2009 Author Share Posted February 3, 2009 Right, I've tried shock and force and managed to shift it almost to the end of the shaft, even with two of us, one levering two flat head screwdrivers forcing the prop forward, the other holding the prop still while using the spanner, but it's stuck there! (remember the lock nut you can see at the front does come off so it's not the thread! I tried more shocks, but it will still not budge, and I'm worried I may bend or damage the shaft! I think I'll try to flood the engine next after warming up, it cold in my garage! Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted February 3, 2009 Share Posted February 3, 2009 Are you saying that the prop nut is stiff on the threads and has been unscrewed bit by bit towards the end of the thread? Quote Link to comment Share on other sites More sharing options...
Richard Duvall Posted February 3, 2009 Share Posted February 3, 2009 It's funny how when you don't want a prop to come off................................. Quote Link to comment Share on other sites More sharing options...
Delta Whiskey Posted February 3, 2009 Author Share Posted February 3, 2009 Thats right Martin, I have got it to move a bit another 10 rev will see it off. Quote Link to comment Share on other sites More sharing options...
Brian Parker Posted February 3, 2009 Share Posted February 3, 2009 Why don't you stop playing around and just split the nut? Quote Link to comment Share on other sites More sharing options...
Delta Whiskey Posted February 3, 2009 Author Share Posted February 3, 2009 How? Cut it somehow? I've never done this before ! Quote Link to comment Share on other sites More sharing options...
Brian Parker Posted February 3, 2009 Share Posted February 3, 2009 If you don’t have access to a nut splitter. Then, with assistance, support the prop nut firmly on one of its flats and with a sharp cold chisel on the opposite flat strike firmly with a hammer, the nut will split with one strike, the shaft threads will be undamaged and the nut will fall off. Quote Link to comment Share on other sites More sharing options...
Hamish Posted February 3, 2009 Share Posted February 3, 2009 It is quite simple if you have done it before. You need a sharp cold chisel. Put one flat of the nut on a solid surface, eg a vice., and hit in the middle of the opposite face with the chisel to cut through. You do not need to go right through as the nut will split and you can then unscrew it. Take care not to cut the thread. If you are unsure try your local garage and they may do it for you Quote Link to comment Share on other sites More sharing options...
Delta Whiskey Posted February 6, 2009 Author Share Posted February 6, 2009 Update and successful removal !! I brought a nut splitter from Halfords...........but....... ......... none of you came up with this idea!! .......A friend come round helping with my heli rebuild, and he said while looking at the stuck prop "have you got any string?" Next to us in the garage was an old boot, so we pulled out the lace, wrapped it a few times around the shaft behind the prop, wrapped the two loose ends around a spanner, twisted it taunt, and pulled forward while undoing the nut with another spanner, and hey presto......it worked ! One for the archives I think !! I will return the unopned nut splitter and get my £10 back ! Quote Link to comment Share on other sites More sharing options...
Hamish Posted February 6, 2009 Share Posted February 6, 2009 Glad to hear of your success. Quote Link to comment Share on other sites More sharing options...
Delta Whiskey Posted February 6, 2009 Author Share Posted February 6, 2009 Thanks, seems the boot lace was tight enough to stop the shaft turning while we undid the nut. I will lenghten the filler tube, and connect the tank back pressure up to the exhaust, as it appears it was not configure this way.....and see if she will fire up! (in between sleet, snow & rain showers that is !) Fingers crossed! Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted February 13, 2009 Share Posted February 13, 2009 A hydralic lock will lock any engine enough to remove the most stubborn nut. Just remove glow plug turn engine to the bottom of its compression stroke and fill the cylinder with engine oil . Replace plug and undo nut . itsabit messy but wont damage your engine like puting wood etc the the plug hole . The article in rcme about a piston stop tool is great for two strokes if the plug screws down vertically onto the piston but F/S plugs usually screw in at an angle to the piston and any tool screwed into the plug thread to stop the piston will seriusly damage the engine. Glad you mamaged to undo it . make sure the shaft is clean then lightly oil the thread before fitting a new prop. E.D. Quote Link to comment Share on other sites More sharing options...
Bruce Richards Posted February 14, 2009 Share Posted February 14, 2009 That's me told in no uncertain terms Quote Link to comment Share on other sites More sharing options...
Delta Whiskey Posted February 14, 2009 Author Share Posted February 14, 2009 Engine fired up fine, after getting the needle value set right, I notice after the engine started, that when revving the engine, you could see the value moving ! I need to get a new clip thingy, that fits around the needle value to stop it moving, I've tried pinching it with pliers, but it still moved! Quote Link to comment Share on other sites More sharing options...
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