Ron Gray Posted July 12, 2020 Share Posted July 12, 2020 Link to comment Share on other sites More sharing options...
Jon H Posted July 12, 2020 Author Share Posted July 12, 2020 not a fan of wooden engine mounts. they should be cut out and replaced with a glass/nylon jobby Link to comment Share on other sites More sharing options...
Chris Walby Posted July 12, 2020 Share Posted July 12, 2020 Weekend Laser Pro (lower oil content) update as if it needed any update really Saturday. Laser 180 pulling a YAK around. Very minor adjustment of the main needle followed by 4 flights no issues and I think its bedding in a bit or there is a bit extra in the way of engine performance Laser 70 whizzing a Acrowot all over the sky. Initial warm up and minor adjustment (as you do) and then 3 flights with no issues and running sweet. Sunday Laser 70 twins in a Dual Ace, no initial adjustments then 3 flights and on last flight something sounded a little off. So Mr Numpty landed and refuelled then started both and held them at WOT for a few seconds where promptly the port engine died, stopped the starboard, restarted and set the port engine up gave it a little adjustment (should have done that at the start). Then proceed to start the starboard and go flying...you know what I should have done! So because I had not taken the time to set the Starboard engine I was rewarded with a dead engine, needless to say it was a bit exciting and the other 70 performed faultlessly to get me back on the field safely. Summary All of that and only used 1/4 gallon, hardly any post flight cleaning and great performance its a thumbs up from me! Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted July 12, 2020 Share Posted July 12, 2020 Something niggling at the back of my mind... You had 3 successful flights and then the engines needed adjusting? Any idea why that would be? I would have thought that any adjustments should have been required during the first tank of the new fuel... Could the new fuel be flushing through oil residue in the carb or is something changing mechanically - valve clearances, ring sealing, something else? Link to comment Share on other sites More sharing options...
Chris Walby Posted July 12, 2020 Share Posted July 12, 2020 I have flown the Dual Ace on the new fuel before, it was just my fault for not doing the individual engine warm up and main needle adjustment (as I should have) instead of warming both up and holding WOT for a short time before flying. I follow Jon's advice and don't WOT them on take off and for the first couple of flights only used WOT a couple of times for a brief period. The third and much of the forth flight it was at WOT for longer periods. Perhaps a product of + 10C ambient increase and they are over propped for the noise test as they only needed 1/4 of a turn or less to get them spot on. Moral of the story...follow manufacturers instructions. Link to comment Share on other sites More sharing options...
Jon H Posted July 13, 2020 Author Share Posted July 13, 2020 Its not uncommon for engines to change a little over the day, especially if they have not been run in a while as it can take a little bit of time for the rings to fully loosen up, any oil accumulation in the crankcase needs to be spat out, oil residue in the carb can also take a little time to wash out (especially if its castor!). I dug out my twin 70 powered model a few weeks ago and it took 3 or 4 flights to fully dial it in as i changed fuel and the engines had not been run in about 5 months Link to comment Share on other sites More sharing options...
Eddy Dale Posted July 20, 2020 Share Posted July 20, 2020 Posted by Jon - Laser Engines on 15/06/2020 09:36:19: Ha! True enough, i love testing the 240v's on a 16x8 and watching the revs rise. So often the engine sits there at 9800-9900 and i am willing it on to the round 10k! Those revs are not ideal for a warbird though as you get that awful prop whine...unless i fitted a 1.7:1 gearbox on the front. 9000rpm on the engine, 5100 on the prop. Normally a 17x8 2 blade will do about 9000, with some maths i recon you could swap 17x8 2 blade for 21x14 3 blade using a gearbox like that. Sound like fun? who would pay £150 for a gearbox as an upgrade part? Edited By Jon - Laser Engines on 15/06/2020 09:36:45 Hi Jon, I really hope that you will start producing gears for your engines and would easily pay 150£ for one. Think that the option of installing gear on the engines will increase the popularity a lot. Many people would be interested in the possibility of putting large scale propellers on their warbirds operating on lower RPM’s. I guess the sound will be sweet too! Do you have any pictures or videos of a prototype? Link to comment Share on other sites More sharing options...
kevin b Posted July 20, 2020 Share Posted July 20, 2020 Looks to me like someone will have to gear up for mass production of large 3 blade props ! Link to comment Share on other sites More sharing options...
Richard Harris Posted August 30, 2020 Share Posted August 30, 2020 Jon, One of my club mates has a Laser 120 vee twin, it's blown a few plugs of late and he cannot remember what they were as they were purchased 30 odd years ago along with the engine. What would be the right plugs to be purchasing as spares in this day and age? Rich Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted August 31, 2020 Share Posted August 31, 2020 Blowing plugs is often a sign of failing bearings so it would be as well to check it over carefully before any major damage might occur from a disintegrated bearing. Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted August 31, 2020 Share Posted August 31, 2020 One thing I've read in other forum posts is that having too long a tube on the crankcase vent is bad for the engine, is there any reason for this and what is the recommended maximum length. I've got a 200v installed inverted in a model and would like to route the vent externally, this would be around 200mm long, is this OK? Link to comment Share on other sites More sharing options...
Ron Gray Posted August 31, 2020 Share Posted August 31, 2020 I use OS F plugs on all of my Lasers and can’t remember the last time I blew one! Regarding the oil breather pipe, I don’t think it makes any difference how long, or short it is, well apart from redirecting the ‘mess’ that is. Link to comment Share on other sites More sharing options...
J D 8 Posted August 31, 2020 Share Posted August 31, 2020 The crankcase vent pipe on my Major Mannock's Enya 90 is all the way down the UC leg, never been any problem. Link to comment Share on other sites More sharing options...
Eric Robson Posted August 31, 2020 Share Posted August 31, 2020 The RCV. instructions state the breather tube should be 2-3 inches max. and I think OS is the same, the reason being that if it is too long the breather does not clear the oil quick enough, Laser engines recommend a lower oil content in the fuel so it may not be a problem with them. Link to comment Share on other sites More sharing options...
Eric Robson Posted August 31, 2020 Share Posted August 31, 2020 Hi JD8, you posted as I was typing , could be the position of your breather the airstream is helping to clear the pipe. Link to comment Share on other sites More sharing options...
ken anderson. Posted August 31, 2020 Share Posted August 31, 2020 nowt to do with the laser engines(off topic) but the reason behind the length of the breather tube on os engines was because the way they work, after the engine has ignited the fuel the oil go's down the bottom to lubricate the bearings and crankshaft,as this is a constant on going process the breather nipple provides the exit.if the tube was too long the stuff doesn't get away in time and the next lot cant exit... hope that makes sense(whatever that is)... ken anderson...ne..1....sense dept. Link to comment Share on other sites More sharing options...
Denis Watkins Posted August 31, 2020 Share Posted August 31, 2020 The breather on my Tiger Moth is down the U/C leg too, and I have found this ok. The motor is an inverted Saito, so the oil has to find its way up then down. After a 10 minute flight, and the resulting 30 minute chit chat between flights, the tube drains all but clear Link to comment Share on other sites More sharing options...
Chris Walby Posted August 31, 2020 Share Posted August 31, 2020 Jon can have the final say, but IMHO the pipe should be a short as possible, why? For total loss (lubrication) engines you are relying on the pumping action + a bit of piston blow by to push the oil out. if you have a very long drain pipe it will increase the pressure in the crankcase due to oil resistance against the pipe wall. This will result in used oil not being dispatched or worse lying around in the crankcase doing no good. If you increase the crankcase pressure then the oil blowing by the piston won't get to the bearings and valve gear and it will all wear out quicker. However if the piston/cylinder clearance is larger then you will get more blow by, but you then get poor low rpm running and when rolling to inverted can upset engine running so not a good thing. I don't think having the pipe in the slipstream will make any difference, there are no other forward facing "ram" type inlets to the engine crankcase. In fact this would be counter productive when trying to push the oil down the breather pipe. There are some engines that connect the breather to the inlet manifold, but would you want to eat your own waste? If the pipe has to be long then increase the ID of the pipe, ideally so that oil can pass in one direction and air in the other as in self draining. PS other engines may not be made to the same tolerances and thus be able to pump oil long distances. Link to comment Share on other sites More sharing options...
Engine Doctor Posted August 31, 2020 Share Posted August 31, 2020 As per above post keep the small bore tubing that fits the nipple short up to two inches or so then fit a larger bore tube to guide the use oil away. The larger bore allows air to get past the oil that is impossible in the thinner bore tubes. This was the case with older engines when we used Castor oil , thick horrible stuff. With modern synthetic oils that are thinner and used in lower ratio in the fuel a longer thinner tube may work fine. If it still cloggs then fit a larger bore tube as above. Don't forget that the crank case pressure pulses from positive to negative so if oil in tube can fill the tube it will only be pushed so far down the tube by the positive pressure. Then piston starts it's upward travel causing a negative pulse and this draws the oil back. This can cause a build up or excess of oil in the crank case . I have to say I haven't experienced this since the old Castor days when 20% of the treacle sorry Castor was the norm . Oh and some will remember the special four-stroke oil from yesteryear. That I believe had even more treacle in it started this whole subject off. Edited By Engine Doctor on 31/08/2020 11:21:49 Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted August 31, 2020 Share Posted August 31, 2020 I understand that the breather pipe location is often designed to encourage airflow (and thus oil flow) past the camshaft/cam follower area - the area requiring maximum lubrication in an engine due to the loaded scuffing action. I discovered this while researching the function of an air pump on a 180 degree common crankpin Saito twin - as there is no change in crankcase volume due to the opposed pistons the pump was there to create the airflow provided by piston oscillation on singles. As Saito had gone to the trouble and expense of providing an air pump, my conclusion is that piston blow-by can't be sufficient to provide this function. I strongly suspect that the recommendation to limit outlet length is to promote free passage for the benefit of this lubricating flow rather than it simply oscillating in the tube. Link to comment Share on other sites More sharing options...
Jon H Posted September 1, 2020 Author Share Posted September 1, 2020 Bit late to the party but glow plugs are real simple. There are only 2 in the whole world. The OS F for anything 4 stroke, and the OS 8 for anything 2 stroke. If it wont run on either of those then im not interested! Oil pipe length, we have never tested it to be honest. We have run the engines with the pipe blocked completely and they still work. Everything the other guys have posted is more than reasonable so dont loose sleep over it. Link to comment Share on other sites More sharing options...
Bruce Collinson Posted September 1, 2020 Share Posted September 1, 2020 That's interesting. In my formative stage with 4 strokes I tried inadvertantly to take off with my Laser 80 oil pipe still bunged and it cut out twice just before takeoff. Apologies for the split infinitive. BTC Link to comment Share on other sites More sharing options...
Paul james 8 Posted September 1, 2020 Share Posted September 1, 2020 I'm sure we can overlook the split infinitive but the misspelling of the word "inadvertently" is unforgivable! 😂😂👍 Having been involved in flow measurement in my business for many years the debate over crankcase breathers is quite interesting. It isn't just the diameter of pipe that has the influence, overall "dead volume" will also have an effect. On my four strokes I use the shortest run of breather possible with, as others have suggested, the shortest length of small diameter pipe possible, then on to a bigger diameter to the outlet. It is easy to see the effect of a long length of small bore pipe by simply blowing down it. The resistance can be felt quite readilly. When we think about it, the same volume of air is displaced in the crankcase as the capacity of the engine, both on the up and down stroke. If closed to atmosphere the crankcase pressure will just fluctuate up and down with each stroke. It will reduce power if not relieved in some way, or as in the case of your engine cut the engine out. Blow by will potentially increase the positive pressure on the power stroke by more than the return of the piston on the exhaust stroke so we end up with an overall positive pressure imbalance, the breather deals with that. Edited By Paul james 8 on 01/09/2020 14:09:06 Link to comment Share on other sites More sharing options...
Bruce Collinson Posted September 1, 2020 Share Posted September 1, 2020 It's a fair cop. BTC Link to comment Share on other sites More sharing options...
Paul james 8 Posted September 1, 2020 Share Posted September 1, 2020 Forgot to mention that on most four strokes some degree of blow by is essential for lubrication of the bottom end of the engine, hard to believe that it is sufficient lubrication to keep them going but it obviously works. It makes proper crankcase ventilation even more important to the wellbeing of our engines.👍👍😊 Link to comment Share on other sites More sharing options...
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