bert baker Posted December 26, 2017 Share Posted December 26, 2017 Planes under the hammer Link to comment Share on other sites More sharing options...
David P Williams Posted December 28, 2017 Share Posted December 28, 2017 Hi all, I'm struggling with the same old inverted laser/tank height problem. It's made worse by an angled cooling tunnel where I really need the tank to be. Anyway, I understand that the centre line of the tank should be level with the centre line of the carb spraybar/venturi. Does the style of tank make any difference, eg I have one of these Dubro tanks If mounted upright the fuel feed comes out of the top of the tank and if mounted inverted (any reason why you can't mount these style tanks inverted?)the fuel feed comes out of the bottom. Does any of this matter? I can't get my head round it. Should I just get a tank where the feed comes out of the centre? Thanks for any help and advice Link to comment Share on other sites More sharing options...
Bob Cotsford Posted December 28, 2017 Share Posted December 28, 2017 It's the centreline of the tank that matters David, where it feeds from shouldn't matter. On my Provost I hacked the tunnel so that I could drop the tank by an inch or so. There's still plenty of airflow, at least the engine hasn't complained. Link to comment Share on other sites More sharing options...
Jon H Posted December 28, 2017 Author Share Posted December 28, 2017 What Bob said Which model are you working on? got a photo of the installation? might help work out the best plan of attack Edited By Jon Harper - Laser Engines on 28/12/2017 15:22:31 Link to comment Share on other sites More sharing options...
David P Williams Posted December 28, 2017 Share Posted December 28, 2017 Thanks chaps. Jon - it's a 150 that I bought second hand from (I think) a deceased modeller's estate, DP M02 stamped on the mounting lug. It appeared to have had very little running. It's fitted in a SLEC/Apache Chipmunk, that I flew for the first time earlier this year. Four flights, four deadsticks. Seems to run fine on the ground, holds full throttle, idles fine, but take off and fly for a minute or two, and the engine either dies or it will run at low throttle setting but not throttle up. I was worried about overheating so the last couple of flights were without the cowl, with the same result. After the last one I restarted it on the ground - same thing, wouldn't throttle up then slowed and stopped with big puffs of smoke. Very disappointed and didn't want to further risk the model I had spent a ot of time on, so it went in the naughty corner. After seeing all your stuff on the forum about tank position, I though I would use the winter workshop season to try lowering the tank. The centreline is currently about 25mm above the carb, and I thought this might be part of the problem. Or is it just my rubbish engine tuning skills? Edited By David P Williams on 28/12/2017 16:17:13 Link to comment Share on other sites More sharing options...
Jon H Posted December 28, 2017 Author Share Posted December 28, 2017 nope that sounds like the tank. As the fuel level reduces so does the fuel head and that effectively leans the mixture and that is the cause of your issues. Lowering the tank shouldn't be too back on the chippy, we have had many lasers fitted to that model without issue. If it helps, you might be able to use a smaller tank as you shouldn't need more than 12oz for the 150. This might help squeeze it into the space if you have other stuff in the way that cannot be removed with some hacking. Link to comment Share on other sites More sharing options...
David P Williams Posted December 28, 2017 Share Posted December 28, 2017 Thanks Jon. It would have been easier to do it while building, but I should be able to lower the tank without too much trouble. I have a nice sliding battery tray below the tank, just need to swap it to above the tank plus find another 10mm or so- plenty of room to do that with the 14oz tank I have. Won't get out flying for a while now though, I'm becoming a fair weather flyer as I get older and the model is too nice for the muddy lengthy grass on the field at this time of year. Link to comment Share on other sites More sharing options...
trebor Posted December 28, 2017 Share Posted December 28, 2017 My pair of engines are making what I think are loud clicking noises after I've given them a good clean. I don't think it's the valves but more like the cams or push rods. I had a bit of trouble getting the valve adjusters to seat on the push rods once the rockers were in place but I cannot pinpoint what's causing the noise. Any tips appreciated. Can you hear clicking going on on a new engine ? Link to comment Share on other sites More sharing options...
bert baker Posted December 28, 2017 Share Posted December 28, 2017 Sounds normal to me, Link to comment Share on other sites More sharing options...
trebor Posted December 28, 2017 Share Posted December 28, 2017 I'm thinking that the followers are sticking maybe then clicking free. Link to comment Share on other sites More sharing options...
trebor Posted January 9, 2018 Share Posted January 9, 2018 Would it improve the fuel supply if I made a fuel tank air vent that pointed forwards behind the prop, for prop air pressure Link to comment Share on other sites More sharing options...
Ron Gray Posted January 9, 2018 Share Posted January 9, 2018 Jon advised me to do exactly that, point the vent tube forward where it comes out of the fus. Link to comment Share on other sites More sharing options...
Jon H Posted January 9, 2018 Author Share Posted January 9, 2018 What Ron said and the valve springs tend to click as they are compressed/decompressed. Its pretty common on all model 4 strokes and nothing to worry about. And Ron your 155 is about to fly the nest. Sorry for the delay. Edited By Jon Harper - Laser Engines on 09/01/2018 13:55:19 Link to comment Share on other sites More sharing options...
trebor Posted January 9, 2018 Share Posted January 9, 2018 I've never had a open vented fuel pipe before it's always been on the exhaust pipe. Should I loop the pipe to prevent spillage ? Link to comment Share on other sites More sharing options...
Merco 61 Posted January 9, 2018 Share Posted January 9, 2018 Hope this question is not interrupting the flow too much.I am about to swap out a much longer engine and replace it with my Laser v200.It will entail a1.5 inch spacer of some sort.Ive made up ally standoffs and long bolts in the style of many modern petrol engines,but it looks rather ungainly and I,m a bit concerned that I might be putting the Laser mounting lugs at risk in the event of a noseover into the rough.Would appreciate your views.Thanks. Link to comment Share on other sites More sharing options...
Jon H Posted January 9, 2018 Author Share Posted January 9, 2018 Posted by trebor on 09/01/2018 14:19:30: I've never had a open vented fuel pipe before it's always been on the exhaust pipe. Should I loop the pipe to prevent spillage ? No need. Once the engine fires it starts drawing fuel and this suction keeps everything where its supposed to be. Merco, no problem at all. Just laminate some ply to the required thickness and seal with epoxy. Once thats done drill though the block and use long bolts through the engine, block, and firewall into captive nuts. These will pull the whole lot together and be nice and secure. Link to comment Share on other sites More sharing options...
Ron Gray Posted January 9, 2018 Share Posted January 9, 2018 @Merco61 Link to comment Share on other sites More sharing options...
Ron Gray Posted January 9, 2018 Share Posted January 9, 2018 @ Jon, thanks and hope you're feeling better! Link to comment Share on other sites More sharing options...
Geoff S Posted January 9, 2018 Share Posted January 9, 2018 Is this fuel tank installation OK? Like Trebor I've always used a pressure feed from the silencer. Here I've put a piece of soft aluminium tube through the firewall . If I need to put the tank any higher then the feed to the carb will get progressively longer which I assume should be kept to a minimum. You can just see the forward tip of the tank over the top of the bay. The vent/pressure pipe is just near the carb and exits alongside the engine bearer just forward of the throttle linkage. I'm hoping to test fly the Laser 62 some time this week. Just got to set up the throttle servo and check the CoG. Geoff Link to comment Share on other sites More sharing options...
trebor Posted January 9, 2018 Share Posted January 9, 2018 The top of the tank just looks higher than the carb intake, I would think that's ok. Mine carb is about 3/4" higher than the centre of the tank and outlets. Link to comment Share on other sites More sharing options...
Jon H Posted January 9, 2018 Author Share Posted January 9, 2018 it should be fine Geoff but with a tank that size you will be up there for hours! you could use a smaller tank and shuffle it forward just a bit. Remember that the vent pipe is also the fuel overflow pipe when filing so make sure it is somewhere that will not make a mess Edited By Jon Harper - Laser Engines on 09/01/2018 18:45:49 Link to comment Share on other sites More sharing options...
Chris Walby Posted January 9, 2018 Share Posted January 9, 2018 Jon, are there any fuel consumption figures for Laser engines? Its just I track battery performance based on recharge data, but all I do with the 70 is fly, refuel fly, drain put away, the repeat the cycle next time I go flying! Not sure how 1/2 gallon equates to time in the air but its earning its keep at the moment and taking the inclement weather conditions in its stride. Best regards Chris Link to comment Share on other sites More sharing options...
Geoff S Posted January 9, 2018 Share Posted January 9, 2018 Posted by Jon Harper - Laser Engines on 09/01/2018 18:45:10: it should be fine Geoff but with a tank that size you will be up there for hours! you could use a smaller tank and shuffle it forward just a bit. Remember that the vent pipe is also the fuel overflow pipe when filing so make sure it is somewhere that will not make a mess Edited By Jon Harper - Laser Engines on 09/01/2018 18:45:49 It's just a tank I found in my drawer. There are others, I think, but this one was the cleanest How big a tank would be reasonable for a 62? As you can see, the tank bay is quite roomy and, as I fitted a hatch for battery changing, supremely accessible. With the engine sticking out like a wart on the front of my beautiful Ezee Pzee (I jest!) the vent pipe is well clear of anything. Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted January 9, 2018 Share Posted January 9, 2018 Just be very sure that the ball joint retaining nut is securely locked - a detached linkage, partial throttle on an economical engine and a large tank can make time drag a little... Link to comment Share on other sites More sharing options...
Jon H Posted January 9, 2018 Author Share Posted January 9, 2018 Posted by Chris Walby on 09/01/2018 18:58:59: Jon, are there any fuel consumption figures for Laser engines? Not really. The problem is it depends on so many factors like throttle use, fuel/prop/weather/glowplug, accuracy of tuning etc. When I assemble a new model I set the timer for 5 minutes and then fly the maiden until it goes off. I then land and inspect the tank to see what is left. If I used half the tank in 5 minutes I set my timer for 8 and off I go. Martin, you are right there. I had a throttle servo fail on a Laser 150 once and it flew for 25 minutes on the slec 14oz tank that was fitted to it. I am also worried about my Stampe with the petrol in it as it retains the 16oz tank it had fitted when the engine was glow. Assuming the throttle servo gives up at the end of my normal 15 minute flight I estimate I have at least 12oz and thus another half hour fuel on board. This might cause annoyance if said failure occurs at a public display and I have to keep flying round and round until it stops. I might have to investigate a kill switch :\ Link to comment Share on other sites More sharing options...
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