Fuzzy-Felt Bloke Posted September 29, 2023 Share Posted September 29, 2023 Good morning I came by a small diesel engine (DC Merlin) which appears to me gummed up. I've soaked in Glow fuel for two day without any luck and placed in an oven (220) for 15 mins, again without any luck. I assume the engine is seized. What are your thoughts and is there anything more that I could try? Thank you for reading this Kind regards Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted September 29, 2023 Share Posted September 29, 2023 Welcome to the forum fuzzy. I would try stripping the engine carefully - start by removing the backplate. Try to establish if it’s the crankshaft, piston or both which are stopping rotation - very carefully starting to unscrew the cylinder barrel would reveal if the piston has seized but beware of damaging the con rod. If seized, carefully tapping the piston crown with a brass drift as close to bore size as possible might free it. I would heat the engine again before trying to free any parts but it might be worth soaking in kerosene (paraffin) rather than glow fuel before you start. Quote Link to comment Share on other sites More sharing options...
Jon H Posted September 29, 2023 Share Posted September 29, 2023 i would try soaking it in some model diesel fuel if you have any. The Ether should really help soften it all up. If that fails then Martin's suggestion is the next logical step. If you can avoid stripping it completely that is good as the piston/liner have run in their current position for years and are well mated to each other. Moving them may result in a loss of performance. Whipping off the backplate is a good idea though to help get some juice inside the engine 1 Quote Link to comment Share on other sites More sharing options...
extra slim Posted September 29, 2023 Share Posted September 29, 2023 yep, diesel fuel, then some heat, then fresh out of the oven, nip a prop on, and gently rock away.. it should come free. The contra I imagine to be more tricky. Quote Link to comment Share on other sites More sharing options...
J D 8 Posted September 29, 2023 Share Posted September 29, 2023 As above you need some model diesel fuel, turn compression screw out and put a tad of fuel down the hole to soak. Tip out before replacing screw and leave half a turn back from contact with contra piston before trying to turn. Quote Link to comment Share on other sites More sharing options...
GaryW Posted September 29, 2023 Share Posted September 29, 2023 I'm gonna have the same job on my hands next week when I pick up 2 Diesel Powered gliders from a fellow club member which both diesel engines haven't run for around 20 - 25 years... But I know a man that loves playing with engines and he will get them running almost like new again.. Both engines are 1 & 1/2cc PAW's Quote Link to comment Share on other sites More sharing options...
Fuzzy-Felt Bloke Posted September 29, 2023 Author Share Posted September 29, 2023 Thank you for your suggestions. I'm trying to take the back cover off, removed both screws but it will not budge. Don't want to put too much pressure on it but assume it should pull off easily. Does the back plate pull off or is it screwed in? Kind regards Quote Link to comment Share on other sites More sharing options...
Jon H Posted September 29, 2023 Share Posted September 29, 2023 With the through screws removed it should pull off but you may need to give it a twist given how gummed up everything is and you might even need to make a small tool with two pegs that will give the leverage required. Its a faff having to make it, but better than shredding the backplate with mole grips. Before all that and as a starter for 10, sling the thing in a pot of model diesel fuel and leave it for a week. Dont muck about, just drown it in a jam jar for at least a week. Once you fish it out fit a prop and see if you can get it to budge at all. I would do this cold on the basis that it will still be wet with the fuel and once the castor seal is broken fuel will flow into these 'dry' areas and help free them up. Once you get it to move 99% of the job is done. I had to go through this little adventure with my Dads AM10 a little while ago and it did take a while to get things moving. 1 Quote Link to comment Share on other sites More sharing options...
Fuzzy-Felt Bloke Posted September 29, 2023 Author Share Posted September 29, 2023 Thanks Jon, will try your suggestion. Kind regards Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted September 29, 2023 Share Posted September 29, 2023 DC merlin, nice little engine... Find jam jar so whole engine minus prop can be submerged in ordinary car petrol and allow to soak for 2 days or so. You realise the FIRE risk ? With lid on the jar can be shaken, see castor "gum' floating about and resting on jar bottom. The back plate is held on by the two thru crank case bolts/nuts. With those bolts out you can turn the back plate to free it but gasket will be mangled. With back plate off you can use screw the cylinder head and remove the cylinder leaving the piston and rod in place The prop driver plate is a taper fit on crank. No "oil way" in crank case nose to clean. If a soak in petrol fails, try old small sauce pan ( or a new cheapo small sauce pan ) and car engine old. Submerge engine in oil and heat gently on a camping stove OUTSIDE on a gaurantee dry day. Once you see the nearest hint of the oil smoking, turn off the heat ! Hot oil is a very great FIRE and SKIN BURN risk, a very great risk !!! So no pets, kids ( or dumbasses ) anywhere near the hot oil !!!!!!!!!!!!!! Spectre.com iirc will have a report etc. on this little gem of an engine. Take note about rod/piston/cylinder alignment..... Try soaking in petrol to see if it will "free off and turn" but be gentle... Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted September 29, 2023 Share Posted September 29, 2023 Specterflight... Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted September 29, 2023 Share Posted September 29, 2023 While petrol may have a small effect, if you’re going to depart from the advice to use model diesel fuel, denatured alcohol might be a better castor solvent. 3 Quote Link to comment Share on other sites More sharing options...
Jon H Posted September 29, 2023 Share Posted September 29, 2023 7 minutes ago, Rich Griff said: Find jam jar so whole engine minus prop can be submerged in ordinary car petro Not recommended as castor oil is not soluble in petrol so it will not soften the castor like the ether will. as pointed out, its also a greater fire risk than using the model diesel fuel. 1 Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted September 29, 2023 Share Posted September 29, 2023 Sceptre flight.com Quote Link to comment Share on other sites More sharing options...
Fuzzy-Felt Bloke Posted September 29, 2023 Author Share Posted September 29, 2023 Thank you Rich. Will try the petrol first as its cheap and I have some. I've been on the Specterflight web site and great deal of detailed information there, fantastic site. Kind regards Quote Link to comment Share on other sites More sharing options...
Fuzzy-Felt Bloke Posted September 29, 2023 Author Share Posted September 29, 2023 OK, will use diesel fuel Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted September 29, 2023 Share Posted September 29, 2023 I know someone who makes 80 percent alcohol which works really well but is dangerous stuff and gives me a splitting headache. Shifts burnt on carbon and everything but absorb moisture like mad and evaporates quickly.....as said, dangerous stuff... My d1000 is how much a litre these days ? Modern petrol had "additives" these days...easily available and is a fire risk, but what of glow and model diesel fuels ? This hobby is full of risk as we know......so act accordingly. Take care out there... Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted September 29, 2023 Share Posted September 29, 2023 What ever "solvent' you use in the jam jar, don't forget to put the lid on. Quote Link to comment Share on other sites More sharing options...
Fuzzy-Felt Bloke Posted September 29, 2023 Author Share Posted September 29, 2023 Thank for all of your help guys Backplate off, will now give it a good soak in model Diesel fuel. Quote Link to comment Share on other sites More sharing options...
Wilco Wingco Posted September 29, 2023 Share Posted September 29, 2023 Fit a prop, "borrow" the wife's hair dryer, apply gentle heat and GENTLY rock the prop back and forth gradually increasing the arc of movement back and forth over time. As the castor heats up the motor should free up. When you can turn the prop through 360 add after run oil and turn the prop to distribute in the engine. Works for me every time, a word of caution, ware gardening gloves as the motor will get hot. 1 Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted September 29, 2023 Share Posted September 29, 2023 (edited) Think good quality " geometry/engineering drawing set" and thickish brown envelope for the new gaskets... No real need to remove the prop driver plate ( taper fit ) as no crank case " oil way"...... Enjoy this little gem of an engine. Ps is your back plate central spigot hole threaded by chance ? 😀 Edited September 29, 2023 by Rich Griff Quote Link to comment Share on other sites More sharing options...
Fuzzy-Felt Bloke Posted September 29, 2023 Author Share Posted September 29, 2023 Hi Rich Yes, the spigot is threaded. What is this for? Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted September 29, 2023 Share Posted September 29, 2023 (edited) If you intend cleaning the crank then the prop driver plate will need to come off. Remove the finned cylinder head then the cylinder ( if it free of the piston that is ) then the piston/rod off the big end journal noting which way round the rod is..... Then the prop driver plate can be removed. It's alloy so will expand more quickly than the crank. Threaded spigot, for alternative tank, or use the "squarish " plastic tank. Alternatively a "remote tin tank ". You have some dc advertising of the era ? Edited September 29, 2023 by Rich Griff Quote Link to comment Share on other sites More sharing options...
Jon H Posted September 29, 2023 Share Posted September 29, 2023 With the conrod in the position it is i would favour turning the engine backwards (clockwise viewed from the front, anti clock viewed from the rear) as this will put the conrod under tension and not compression meaning you are far less likely to bend it. There may also be accumulated debris on top of the piston which will be incompressible so once its at bottom dead centre and moving freely make sure you can see through the exhaust ports across the engine. If you have an air line handy a quick blast through the exhaust port wouldnt hurt. When it comes to turning the engine right over make sure the combustion chamber is not full of fuel to prevent hydraulic lock. Turn the engine over slowly and gently. If it seems like its hitting something solid stop and find out what it is. Quote Link to comment Share on other sites More sharing options...
PatMc Posted September 29, 2023 Share Posted September 29, 2023 5 hours ago, Fuzzy-Felt Bloke said: Hi Rich Yes, the spigot is threaded. What is this for? Later versions of the Merlin had plastic then metal tanks retained by a single central screw. Early Merlins had smaller plastic tanks retained by the same backplate screws. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.