Chris Walby Posted January 17, 2018 Share Posted January 17, 2018 For information and bearing in mind this is based on number of turns on the pump to fill the tank, minutes run and turns to refill it and then turns to empty the tank (excluding filling/emptying the lines) for a Laser 70 and a bit of math for known tank size. I get 0.557oz per minute or 30p a minute. (this calculation is only indicative and only based on limited data, so prove me wrong!) PS When I get it running right (fault of the owner not the engine), it will most likely be more economic, but for me a nice low pass and the sound of the laser is worth more than the cost of the fuel any day. PPS I had a Honda motorcycle (250cc 4 valve twin carb with no flywheel and double speed countershaft) designed to be very snappy on the throttle pick up. Complicated, high maintenance and could not be messed about with, but served a purpose. Martin, if you are up at the club tomorrow we cold give it a tune, if so let me know a time, cheers Link to comment Share on other sites More sharing options...
Jon H Posted January 17, 2018 Author Share Posted January 17, 2018 Are you sure that's right? unless I did my maths wrong your fuel is 90 quid a gallon... Link to comment Share on other sites More sharing options...
Jon H Posted January 17, 2018 Author Share Posted January 17, 2018 Ok my maths was wrong, but it still comes to £48 a gallon. just to check the maths 1 gallon of fuel is 15 quid 1 gallon of fuel is 4.55 Litres or 160fl/oz 15/160 = 10.5p/oz My 70's run 8oz tanks and I think my timer is set for 8min 30 and I have some spare fuel at the end. Probably no more than 1oz. So 7oz in 8mins 30 is an average of .82oz/min or 8.61p/min? I have never actually measured any of this before. so many units Link to comment Share on other sites More sharing options...
Chris Walby Posted January 18, 2018 Share Posted January 18, 2018 Jon, Yep my maths is wrong. I'll take my socks off and try again. . Looking like nearly a magnitude out... Lucky I am not an MP submitting my expense form...but then again I would have got away with it.. I'll double check but it looks like mine is working out at 4p/min Edited By Chris Walby on 18/01/2018 07:01:53 Link to comment Share on other sites More sharing options...
Jon H Posted January 18, 2018 Author Share Posted January 18, 2018 Posted by Chris Walby on 18/01/2018 06:54:52: Lucky I am not an MP submitting my expense form...but then again I would have got away with it.. they should all have been locked up...sigh. Anyway, on the subject of fuel consumption i would like to be able to publish figures but its very hard to get meaningful numbers as so many things effect it. Also i can only go accurate testing on a bench really and that is not representative of real world usage. Link to comment Share on other sites More sharing options...
bert baker Posted January 18, 2018 Share Posted January 18, 2018 I have a choice of fitting a pump signal pressure line to lid of pump or fitting a nipple on the adaptor I have made Link to comment Share on other sites More sharing options...
Chris Walby Posted January 18, 2018 Share Posted January 18, 2018 Jon, The best you can do is set your own standard and measure your engines against it so a 70 does x and a 360 does y. If I fly around just pottering I will get one figure and thrash it about then a different figure and so on. Model manufactures state engine size "BH Speed Air 40" but my 70 powered one is a dream to fly and most likely came with an 8oz tank, just my fault for fitting a 10oz (only one they had at the shop) so to that end you can recommend and if people don't follow your advice its up to them. IC flight time is no different to electric on the same model and battery I can half the flight time if I stick bash. Once again, thanks for your time. Link to comment Share on other sites More sharing options...
Jon H Posted January 18, 2018 Author Share Posted January 18, 2018 Bert i suggest you try taking pulses from the intake if you can. Not that it matters really, i tried everything i could to make it work and it just wasnt satisfactory at all. You are also going to need a heat break between the carb and head. While we are here Laser do not recommend customers attempt to convert our engines to petrol. If it was as simple as is made out by some then i would have had laser petrol engines ready years ago! If you want to try it for the sake of experimentation then fine, but dont try it expecting to get a useful powerplant from it. Chris, i suppose i could give a max fuel consumption figure but it would only be a guide. We already show recommended tank sizes on our instructions so i dont know if it would actually be any use. Link to comment Share on other sites More sharing options...
bert baker Posted January 18, 2018 Share Posted January 18, 2018 Yup have made a insulator, Only doing for fun as I have stuff laying around. I wouldn't recommend it either. And totally understand where laser are with alterations to the engines. Link to comment Share on other sites More sharing options...
Ron Gray Posted January 18, 2018 Share Posted January 18, 2018 Second running of the 155 this time with a 17x 6 prop and adjusted low end. Now pulling 8900 https://youtu.be/odgyVfcSDCI Edited By Ron Gray on 18/01/2018 14:02:30 Link to comment Share on other sites More sharing options...
Jon H Posted January 18, 2018 Author Share Posted January 18, 2018 Nice Ron, thats over 2.5hp and did i hear a cheeky backfire on the overrun? Oh and i see you are still having trouble starting it, bloody glow engines Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted January 18, 2018 Share Posted January 18, 2018 Posted by Jon Harper - Laser Engines on 18/01/2018 14:15:53: Oh and i see you are still having trouble starting it, bloody glow engines Needs a bigger starting battery Link to comment Share on other sites More sharing options...
Ron Gray Posted January 18, 2018 Share Posted January 18, 2018 Yes, you did detect the backfire, truly excellent! What a joy it is to start, after the vid I did a backflip start no problem so really chuffed with it. As I had nothing better to do and as I had it out for its prop, I thought that I’d fire up the 160v as I have some problems with it only starting on 1 cylinder and it taking a while to get the other one going. I spent about 15 mins playing around with the low end as the top was showing 9000 I felt that there wasn’t much point in playing around with that. Eventually after much tweaking left then right then back to left etc I believe that I’ve got it much better and it now fires up on both and slow running is much smoother. Can’t get it to backfire on overrun though 🙁 Link to comment Share on other sites More sharing options...
Jon H Posted January 18, 2018 Author Share Posted January 18, 2018 Its great when they pop and crackle. If you do get a backfire its usually a sign that the slow run tuning is spot on. Its super childish but doing a large full power loop and jamming the throttle shut on the way down will give you a long stream of pops and crackles. no flight of mine is complete without a few of those. My La7 crackles like mad at the moment due to the prop thats on it. With both cylinders poping away its just a thing of beauty Not all of our engines backfire regularly, usually its only the larger ones that do it on command but i have had all of them do it at one stage or another. The only other engines i have had do it are the large enya 4 strokes. In fact my enya 155 on the overrun is more like a pulsejet than a piston engine! Its good you had a go at the 160 low end. Now its got some time on it there were probably gains to be had anyway and if its running smoother now thats a good sign. Link to comment Share on other sites More sharing options...
Manish Chandrayan Posted January 18, 2018 Share Posted January 18, 2018 Yeah, "bloody glow engines"Get them petrol ones out Jon Link to comment Share on other sites More sharing options...
Jon H Posted January 18, 2018 Author Share Posted January 18, 2018 getting closer Link to comment Share on other sites More sharing options...
Ron Gray Posted January 19, 2018 Share Posted January 19, 2018 Took the, powered by Laser 155, Taylor Craft up to the filed today for its first outing with the Laser. Started no problem for the first flight but subsequent flights got progressively worse, starting wise. Is it possible that, as it is a new engine, the 'slow running' setting gets weaker as the problem seemed to be getting the fuel into the carb? Due to the carb's location I cannot get my digit onto the intake trumpet to choke it so turn the prop over in WOT position then with throttle closed. Link to comment Share on other sites More sharing options...
Jon H Posted January 19, 2018 Author Share Posted January 19, 2018 That's a bit it odd. it didn't ingest something did it? also did it run ok once it was going? Link to comment Share on other sites More sharing options...
Ron Gray Posted January 19, 2018 Share Posted January 19, 2018 No problem once it was running including lots of aerobatics including stall turns and spins which involved fully closed throttle then powering up. Engine didn’t cut out once and landings with varying low rev throttle changes were fine. Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted January 19, 2018 Share Posted January 19, 2018 Ron, just a thought, as you can't choke it to draw in fuel, turning it over at WOT wouldn't draw in much fuel as the engine is turning over at too low a speed to drop the pressure in the venturi and "suck" fuel in. What maybe better is to briefly block the vent while you are filling the tank this will then prime the carb ready for starting. Link to comment Share on other sites More sharing options...
Ron Gray Posted January 19, 2018 Share Posted January 19, 2018 Good thinking Frank, I’ll try that next time. Link to comment Share on other sites More sharing options...
Don Fry Posted January 19, 2018 Share Posted January 19, 2018 WOT = wide open throttle? Link to comment Share on other sites More sharing options...
Ron Gray Posted January 19, 2018 Share Posted January 19, 2018 Yep WOT = wide open throttle Link to comment Share on other sites More sharing options...
Jon H Posted January 19, 2018 Author Share Posted January 19, 2018 If the engine was cold at the time its possible there was oil blocking the carb as the ML70 does get very viscous when cold. I do as Frank suggested on my La7 when its cold as there is no other way to prime the cylinder. The 70's in my twin pulse take at least 20 seconds of cranking to fire when its really cold, it just takes a while for them to draw fuel and then reach a point where they can fire. That said, it was working before so that's a bit strange that its not working now. Its possible that now the engine has some more flight time it just wants a touch more on the slow run but that too is unusual. Good to hear it worked well in the air though Link to comment Share on other sites More sharing options...
Ron Gray Posted January 19, 2018 Share Posted January 19, 2018 @ Jon. I know that you mentioned the compression on this motor but boy has it got some. The starter I use is designed for big gas engines but it really struggled with the 155! In terms of performance, unlimited vertical and totally non scalelike top end speed so that end of the performance spectrum was only used for huge and I mean huge loops. But it was great fun. PS no popping / backfiring in the air today. PPS air temp was about 2 degrees although with the wind it felt a darn sight colder! In fact my soup when I started it was on the only from the edges heat scale but when I got to the bottom it was cold! Link to comment Share on other sites More sharing options...
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