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Scale model Economy hit & miss engine builders wanted

I need to get my engine running

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John Wood1	28/05/2010 14:15:54
116 forum posts	Has anyone out there built and got working the model Economy hit & miss open crank engine from an Engineers Emporium kit? I have but can't get it to run so would very much appreciate talking to someone who has. Thanks, John Wood1
Vapeur89	28/05/2010 20:25:37
18 forum posts	Hi you could take a look at http://www.homemodelenginemachinist.com/index.php and place a question after the traditional welcome post It's a very friendly forum with a lot to learn. American machinist are keen on Hit 'n miss engines. I remember a thread on the trouble firing a vertical hit ' miss engine, but I could n't locate it anymore. regards.
John Wood1	29/05/2010 10:46:13
116 forum posts	Thanks for that. I have had a look and registered so I hope that this will prove fruitful. Much appreciated Cheers, John
JasonB	29/05/2010 11:55:01
25215 forum posts 3105 photos 1 articles	John, make sure you say its the Engineers Emporium one as most of the US kits for the Economy are from other sources. You could also try Smokestack forums, they have a model section towards the bottom of the page. Jason
John Wood1	29/05/2010 15:50:09
116 forum posts	Hi Jason, thanks for the tips. I have just visited Smokestack which certainly has a lot of gen on open cranks so could be valuable. It's nice to see all the goodies from the States! Thanks again John
Engine Builder	29/05/2010 16:07:59
267 forum posts	Hi John I haven't built the Economy but am now on my sixth hit and miss engine. I would set it to fire at TDC, if you time it before this there is a chance it will go the wrong way after this miss period. Most problems I have had have been with the ignition. One engine used a buzz coil and although this gave a huge spark outside the engine it just would not ignight the fuel. I switched to coil ignition and problem was solved. Another mistake I have made is to have too much compression. Reducing this has made the engines better running. I run mine on butane gas as a cleaner option. You can see some of my engines here http://youtube.com/myfordboy hope this helps. David Edit link doesn't seem to work, you may have to search manualy. Edit No 2 You will need to click on "see all" under uploads(29) to get past my casting videos. Edited By Engine Builder on 29/05/2010 16:09:53 Edited By Engine Builder on 29/05/2010 16:15:44 Edited By Katy Purvis on 01/06/2015 09:42:06
John Wood1	01/06/2010 15:15:24
116 forum posts	Hi Engine Builder. Most interesting....I have been setting the timing to a few (more or less) degrees before TDC but will certainly reset to TDC and see what happens. I am using a buzz coil at the moment and, you're right, it does produce a super spark outside the cylinder but, as you describe, I am of the impression that the fuel is not being properly ignited and put it down to carb adjustment. I can easily convert to an electronic system using a hall effect sensor and magnet which I bought from Just Engines and seems to work very well so I will try that. I could try to put together a 'traditional' coil and condenser system with contact breaker points but don't know enough about it to know what coil might be suitable. It's no geed me just buying one and finding it doesn't work because it's either the wrong item or I havn't connected it correctly! anyway, first things first. Very interesting about the compression. I wondered whether the compression was maybe too low to provide enough power to get the thing going, there is certainly a reasonable 'bounce' felt when turning over and the suction through the automatic inlet valve draws the fuel up from the tank OK so, from what you say as well I reckon it's probably OK. I have checked for obvious leakage (valve seats etc) so all looks as it should. Very interested in running on Butane, could you tell me what is involved and how would one go about changing over please? I have tried the engine over the weekend and can certainly get it to fire, in fact it ran by itself for about twenty seconds a couple of times but, by the time I could get to the carb adjustments it had petered out again. The cylinder and exhaust is getting warm but there is no obvious exhaust smoke, also the plug gets quite wet after a while, another indication of poor ignition? Many thanks for the advice, I'm sure it will help me get it going All the best, John
Engine Builder	01/06/2010 16:19:23
267 forum posts	Hi John I am not saying its definetly the buzz coil but the symptoms you have are the same as I had. It would fire once and occasionaly run for a short period. I have found a good source of small motor cycle coils that work well on 6 volts. I can send details if required. To run on butane you need a regulator in the gas line and an good source of small ones is from those single burner camping stoves that have a disposable cylinder in the horizontal position. I picked up some from a discount store for £6.45 once, may be a few pounds more now. You need to experiment by changing the spring inside the regulator to give different pressure, each of my engines seems to need a different pressure. The carb needs to incorperate a demand vavle or the gas will just run free to air when the engine is not firing. The carb on E T Westbury's Centaur engine, free pull out in a recent ME, has a suitable design. David
John Wood1	02/06/2010 19:27:08
116 forum posts	Hi David Thanks for the extra info. I have had a quick go using the electronic system and, so far it seems encouraging but I do need to fiddle a bit more with the timing etc. I would appreciate the info on motorcycle coils please at some time when it's convenient, an e-mail or PM would be fine thanks. I will look into the Propane gas system. Are the normal fixed regulators which come with, say, a small gas barbecue or burner running from a larger orange cylinder suitable do you think? I note the probable need to change the spring pressure. I have actually built a demand regulator to a design found on an American site on the web, it is based on a carburettor diaphragm from a Tecumseh mower carb. It seems to function but I'm not too sure how to employ it. My trouble is I have no experience of gas and am a bit aprehensive of it in case I do something stupid and cause an accident, which is why I am trying to get some practical advice such as you have offered. I have learnt more from you in these couple of posts than I have been able to pick up in a long time so thanks very much. I hope others viewing these posts will also benefit. All the best John
Engine Builder	02/06/2010 20:29:25
267 forum posts	Hi John I have used both the orange propane regulator and the blue butane ones modified with a diffent spring. I have a Calor gas butane regulator in which I have replaced the spring and fitted a knob so I can ajust the pressure to suit the engine. When I am happy it runs ok I can make a dedicated regulator for that engine. The beuty of the camping stove regulator is that they are very small,cheap and can be hidden under the engine complete with gas cylinder and coil. Regards David
Engine Builder	04/06/2010 11:49:49
267 forum posts	Hi John I have just been checking out some of my engines for a rally at the weekend and remembered another tip that may be helpfull. I find a good squirt of WD40 on the piston before the initial run helps the starting. David
John Wood1	04/06/2010 15:04:38
116 forum posts	Thanks again David, much to go at so I shall be busy this weekend. Good tip about the WD40 - makes sense. I will certainly be looking into the gas option. I have ordered a coil as per your PM so that gives me a good start, Have hooked up the electronic ingition and almost got it to run, then I discovered the battery was a bit low after a few tries so have charged it overnight, will have another try tonight.....I shall press on then.....! All the best John
MichaelR	05/06/2010 18:13:12
528 forum posts 79 photos	Hi John, If you go the Propane way with your engine have a look at this article, for Propane running hit and miss engines Here scroll down to Hint 3, there is a PDF file for a demand regulator.
John Wood1	06/06/2010 19:31:54
116 forum posts	Thanks Stick, that should certainly do the trick I reckon, the gen is now on paper. All the best John
John Wood1	19/08/2010 09:50:03
116 forum posts	Just an update. I still can't get this Economy hit and miss running properly although much headway has been made. I can now start it up fairly readily and it will run for up to about 30 seconds but it always slows down and stops no matter what I try. I have tried three different carbs, all work similarly and none give any indication that they would solve the problem. I have also had it running on gas (once) but again, only for a short period. I have not been able to start it again on gas since. I have settled on a conventional points/coil ignition system using a motorcycle coil and contact set, it works fine although I am at present making an inline spark tester as per Jan Ridder's design, just to make sure although I have tried three spark plugs. I have tried many ignition timing settings ranging from well (30deg plus) before TDC to a bit after and found the best setting is anywhere between about 10 before to just on TDC. I have checked the exhaust valve timing which starts to open at BDC at the end of the power stroke and shuts a little before TDC. I have had the head off and checked for leaks, the valves have been re-ground (again) just to make sure. There is decent compression indicated by a firm bounce when the engine is turned over. Both flywheels are fitted and run true etc. etc. What the heck else can I do?? There is a tendancy for starting to be somewhat easier at the beginning of a test when everything is cold, often it's difficult to get decent firing after things have warmed up a bit - clue? In order to ensure a decent fuel flow to the carb I do have to elevate the fuel tank a bit higher than the design calls for (tank normally located inside the engine base casting), there is not really enough suction otherwise to ensure no air bubbles in the fuel line. My overall impression is that ignition is not taking place on EVERY stroke for some reason and this must surely be due to either incorrect fuel mixture or intermittent sparking so I am continuing along those lines. I just can't believe how difficult this seemingly straightforward project is proving - ah well! Regards to all readers, John
Richard Parsons	19/08/2010 10:18:52
645 forum posts 33 photos	John Look at the plug. Sometimes the insulation degrades as the plug warms up. Have a look for fine filaments of carbon forming across the points. These often break as the plug cools. Small plugs can be the very devil with this problem. It is often caused by too much lube oil sloshing around in the cylinder, in the fuel. As you are ‘running it in I will bet that you are keeping the engine well ‘oiled’. Also try placing a small spark gap in the plug line. This also helps by making the plug fire ‘harder.’ These things can be bought as ‘performance improvers ans are often found in plug caps.
MichaelR	19/08/2010 19:09:08
528 forum posts 79 photos	John, have you given any thought that your engine may be seizing up, I had the same problems with my RLE engine, it would start OK, run for a short while then stop. I don’t know what made me do this but while the engine was running I squirted WD 40 on the piston as it cleared the open end of the cylinder and the engine continued to run, it now runs and starts with no trouble and has run long enough to bed the rings in. My theory is the engine was seizing through lack of cylinder lubrication and initial tightness, I know all this sounds a bit weird but it worked on my engine
John Wood1	20/08/2010 10:23:57
116 forum posts	Thanks for the input gents. I have just put an inline spark gap in the plug line to check the spark presence although I have not tried it actually running, I did however open up the plug gap and that seems to have helped. Stick; your theory certainly has much merit and I do think that this may have been hapening here as well because, as I have progressed,the run time has certainly improved and I also note an increase in compression which also indicates that the rings are bedding in. Since yesterday's post though I am happy to report that I have now had several longish runs and even the hit-and-miss governor started working for the first time although I still need to learn how to correctly adjust this. I wish I could report a single change which caused it to start working but, having gone through everything as detailed in the above posts, it all came down to learning how to adjust the simple carb. As you would expect it needs full choke to start but, as soon as it starts firing the choke needs opening up and also the mixture jet needs closing a bit, also the throttle has to be wide open at all times it seems. One thing I have noticed which was quite unexpected is that whenever an adjustment is made it seems to take a long time for the engine to respond, I think this was holding me back previously as I expected an almost instant response, much like a modern engine. Anyway, so far so good and let's hope It still works next time! Many thanks again to all those who have given advice without which I would surely have failed. All the best, John
Ian S C	20/08/2010 13:11:33
7468 forum posts 230 photos	Most hit and miss engines I know don't actually have a throttle (these are full size). One engine for example came with of all things, a carb of a Model A Ford. I made a mixer valve. If you'v got E.T.Westbury's book;Model Petrol Engines there is a diagram of an elementary carburettor on page 115, I can't remember the bore of the venturi, proberbly about 1/2", the intake end has a sliding cover that acts as a choke, at min dia of the venturi is a needle valve, and the fuel comes direct from the fuel tank about 6" bellow.To start, close the choke and open needle valve 1 1/2 turns, turn the motor over 2 or 3 turns. Turn on ignition, open choke, crank motor, should start on two or three turns. set the needle valve for smooth running. This thing is in its self a bit of hit and miss, but it works well. It was made in a bit of a rush (2 or 3 hrs), out of scrap steel, I was going to make another out of brass, but this one works so well that i'v just left it. The motor is about 2hp. I imagine that for a motor the size of yours John a venturi of 1/4"would maybe be too big, I'm putting together a motor with a 2" bore and 4" stroke and i'm going to try 3/8" for a start (the basic design is about 120yrs old).Ian S C Edited By Ian S C on 20/08/2010 13:13:40
John Wood1	21/08/2010 09:39:13
116 forum posts	Hi Ian Yes I do have the Westbury book you refer to and certainly know the diagram in question. I do think a bit of experimentation is required here and I thought a reduction in venturi size might be interesting to try. I didn't realise that H & M engines mostly didn't have a throttle which makes sense really. The carb I am using sounds much like you describe but I do have trouble lifting the fuel from the tank. As you describe I close the choke etc and watch the fuel come up to the carb OK but it keeps dropping back causing air locks in the tube which starves the engine and makes it peter out. By raising the tank to not much below the carb I can eliminate the problem and all is then OK. I suspect the non-return valve on the end of the feed tube in the tank is not working properly so I am looking to replace that soon. Is there normally a non-return valve in the fuel line of H & M engines? I suspect there must be. Thanks for the post Ian, it all helps me to understand what I'm doing, what I shall try for is to get hold of a real H & M stationary engine to play with so I can see all these things for myself. All the best, John

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