Laser Engines - Technical questions

[Bruce Collinson]

Danny,

Really interested that you haven’t flown IC for ages. Nothing better than a Laser. Laser 5 and OS Fs are commonplace; is it too late to amend your MSL order? I recall there’s a deal on carriage. MSL always have F plugs in stock.

If yours is run in, speak to Jon about the low-oil fuel as my pals are using it and it is much cleaner. If you start on standard 5 it will need slight tuning, there’s proportionally more methanol in it.

Interesting too that Martin, clearly a very experienced modeller, advocates exhaust pressurisation which Jon dislikes. Pals have fitted chicken hopper systems to overcome tight installations and I have one to maiden in an F3A with a 120 and a tight cowl. There is a slight suspicion amongst said pals that running exhaust gas through a tank then draining the tank back into the fresh fuel may lead to discolouration in the fuel and then starting and running issues. I can attest to at least two containers of Laser 5 which became distinctly discoloured and weren’t reliable thereafter.

My clubmate Steve Dunne, also highly experienced, put a good graphic of a chicken hopper installation on here about 3 years ago. Start with 2 yards of fuel tubing .....

looking briefly at the image of the Chippy, I doubt whether you will have any difficulty in achieving a satisfactory tank height.

I’ve found your build logs and contributions helpful and I hope you find this so. Let us know how you fare.

BTC

[Danny Fenton]

Hi Bruce, great info and thanks for sharing, though I am at a loss as to what a chicken hopper is??

I gave up on IC ten years ago. When I was in my twenty's and starting out flying R/C my engines would not stop. But move forward 20 odd years when I took up the hobby again and the blessed things would stop at the drop of a hat. A group of us were dabbling with LiFe batts from DeWalt power tools and getting great results, we even had to design our own chargers.I gave away all my glow field equipment and never looked back.

I am not going to go into a discussion of which is better, each to their own, but having just one dead stick in the last 12 years speaks for itself, (that was down to a dodgey Deans connector, I stopped using Deans after that).

A Laser ticks the sound box when flying in competition. Yes I have several models with sound modules, but for me the technology is not there yet.

Let's see if this laser will run reliably.........

Cheers

Danny

[Ron Gray]

This is Steve’s setup as mentioned by Bruce, I’ve copied it from the Chicken Hopper thread.

Here is a sketch of my chicken hopper tank system, as shown in the Laser Tech thread.

The initial problems in draining the bottom tank were overcome by fitting a T-valve in the carb line.

It now flies very well in the Spitfire, fully (scale) aerobatic.

Please note: When filling the tank you must ensure that the top tank is completely full so that it starts feeding the bottom tank. Stop filling when the bottom tank starts spilling.

To empty the system, first drain the top tank, then invert the aircraft and drain the bottom tank.

The air release tube fitting is a fuel bottle fitting.

When building the system, ensure that the bottom tank spill tube end is above the bottom of the air release tube, so that the fuel level does not reach the spill tube before the air release tube is blocked by the rising fuel surface..

How does it work?

When the fuel level in the small tank falls, it allows air up the release line, which then allows fuel to come down the fill line into the small tank. When the fuel level in the small tank rises to block off the release line, a partial vacuum forms in the top tank, stopping the fuel feeding out and down the fill line.

Even the chickens can work it!

So far the system has worked very well for me, in a H9 81" Spitfire.

Steve.

[Danny Fenton]

Thanks Ron, looks quite complex to me. I will try and keep it simple.

Cheers

Danny

[Bruce Collinson]

Having done one, it is. Last resort if you cannot get the tank to locate within (unpressurised) Laser parameters. If you are in that position, as it were, look at Sullivan tanks. In my Infinity F3A, which was evidently built around a Yamada with the tank way back over the C of G, I very nearly coaxed a Sullivan Flex Tank into the lower cowling by dint of lots of hot air gun, rounded sticks and thick gloves. If the chicken hopper installation proves impenetrable, it may well be Plan C (B involves a Saito with its pressurised fuel system).

Sullivan has an extensive range of tanks including V-shaped for boats, some of which could find a home in a cramped installation. Having said that, looking at your skill sets, you could make one! Built in tank ... compartment fully lined with glass and much epoxy ...then drill and fit the pipe exits, seal with high tech silicone ... erm the lid is difficult ...

BTC

[John Stainforth]

I found the chicken hopper system works well. The plumbing is rather confusing, so it is best to get it sorted out and working on a test bench first (with the tanks at the required levels), before putting the whole thing into the plane. IMHO, the chicken hopper set-up is far preferable to trying to accommodate a normal tank arrangement by hacking away at the plane.

[Engine Doctor]

I use the same set up in a twice size lady Bird with an Enya 60 4C power.as there is little room for fuel tank any bigger than 4 ounces behimd the firewall I use a second 4 ounce tank mounted higher up in the cockpit area that is level with the rocker cover on the engine and it works a treat . No syphoning or other fuel problems .

[David P Williams]

Danny -

I'm sure you won't need to bother with any complicated plumbing with the Chipmunk, there's plenty of room to mount the tank at the correct height.

I have a Laser 150 in my 1/5 Chipmunk. Initially, I had the tank where the kit position was and it would run fine for take off and about four circuits, then refuse to throttle up and gradually die. I moved the tank down by 20 - 25mm or so to the position recommended by Jon at Laser and it has been totally reliable ever since.

Just have the carb spraybar level with the top half of the tank and the vent facing forward, and all will be well. It will sound great, and if you use the new low oil Laser 5% mix from Model Technics there will be hardly anything to clean off the airframe.

[David P Williams]

Forgot to say - pay attention to correct baffling for cooling. As you know the scale air inlet is on the wrong side as the prop rotates the opposite way to the full size Gipsy Major. Easy to reverse for electric of course.

Also - if you think you might go electric anyway and sell the Laser on, don't run it until you've made the decision. If it hasn't already been run it may be worth a bit more as NIB unrun.

[Danny Fenton]

Thanks David, I picked up the engine second hand, its in great condition, and apparently Jon has given it the once over for the previous ownere.

Can I just clarify, what size tank for say a 15 minute flight, fairly sedate aeros, and how should the tank be positioned? clunk in line with needle valve?

Cheers

Danny

[Nick Somerville]

16oz ought to be big enough for 15 mins. 20 oz I suppose if you want additional security. Clunk about 5 cms below the spraybar works on my two 180 models and have allowed for the same in my P47.

[Jon H]

Welcome to the club Danny

Just a quick one from me as i am on holiday at the moment and doing my best to forget about work all together but..

Yep, Laser 5 fuel and OS F plugs are winners as already recommended.

Exhaust pressure not needed, if it was we would fit a nipple. The only exception is in cases where tank position is dodgy. My P39 uses tank pressure as the tanks are a long way behind the engine and even at the right height i can suffer a little in long vertical. Treat it as a last resort.

Chicken hopper, not recommended. Its not that it cant work, its that its viability is totally dependant on a given person correctly interpreting the instructions and then correctly building it. Its adding more things that are beyond my ability to troubleshoot on the phone when there are problems so we dont recommend them. Keep it simple and all that. Lowering the tank is always the simplest and easiest way to go. Get the top of the tank in line with the centre of the carb and it will be fine. Should be easy on a chipmunk as its got loads of room.

I had a 14oz tank in my stampe when it was 180 glow powered. 20x6 prop (cheap hobby king prop, i am told falcon 20x6's work very well, dont use master airscraw) and i think i flew 25 minutes once or twice when cruising around late in the evening. 16oz would really be more than enough in a slow flying model like this

Model shop leeds stock both the normal laser 5 (ok for all engine brands) and the new Laser 5 pro low oil (only for laser). They will also post it if you cant collect.

If you need anything more i will be back at the coal face..in 2 weeks ish? the boss didnt tell me when i was supposed to come back!

Edited By Jon - Laser Engines on 28/09/2020 17:30:42

[Bruce Collinson]

Jon,

Enjoy your break, sorry to disturb it (?).

could/should I run in my NIB 155 on low oil or is that reckless?

BTC

[Danny Fenton]

Thanks Nick and Jon I will follow your advice.

The only Hobbyking prop I can see is an Aerostar 20 x 6 wooden, is that what you meant?

Cheers

Danny

[Nick Somerville]

The Menz wooden props are a great match and from MWMWarbirds they are very reasonably priced. 20x6 on my Stampe and a 18x8 on the Extra. 330sc

[Martin McIntosh]

I have been using 18x8 Menz, Falcon etc on my 180 powered Stampe, 180 powered Spit. and the other 155 Spit. for a long time. The Graupner G-Sonic composite is the same price and very good indeed. Recently been flying the Stampe on a Falcon 20x6 to improve the loops but the lack of speed spoils the rolls. Probably a good choice for a Chippy.

Regarding the tank set up, from the drawing it looks like the tank could be placed quite low and considering that it is not likely to be flown inverted I would not worry about it anyway.

I really cannot see how that chicken hopper could supply fuel when inverted. Pics of my dual tank installation on the Stampe thread somewhere but not clear in the pics; it looks more complex than it really is and I can fly inverted as long as I like despite the carb being very low. Could draw it out here if anyone is interested.

[Tim Flyer]

Danny I don’t think you will have tank problems on your Chipmunk. As Jon said the chipmunk is very roomy . I managed to get the tank in a fairly good position on my SLEC Apache Chipmunk also powered by an inverted Laser 180. I didn’t need any fancy tank arrangement or pressure feed. The 180s are a real classic engine and a pleasure to operate.

Edited By Tim Flyer on 28/09/2020 20:09:27

[Steve Dunne]

Martin,

Inverted flight is no problem, unless you are doing it for minutes at a time!!
The 4oz tank acts just like a normal tank setup - the carb draws fuel as long as there is fuel to draw.
The hopper fill line allows air to get to the top tank, breaking any vacuum, but that just lets more fuel descend once the aircraft is right way up again.

I don't do extended inverted flight with the Spit so cannot prove it, but long slow rolls are a regular and problem-free maneouvre.
Having said all that I can't argue with Jon's comments - you have to get it right, and to understand what you are doing with the fuel feed. Like anything else, really!?

Steve.

[Jon H]

i have not tested every prop under the sun but menz, aerostar, falcon, apc, fiala, xoar all give good performance in my experience/customer reports. Master airscrew are good for turning rpm into noise but not much else. Great boot scrapers though. Im not a massive fan of graupner super or G sonic for various reasons, mostly noise related, but the gsonic 20x10 i have on my P39 is awful when it comes to downline braking and will howl like a banshee if it unloads.

The 20x6 HK prop i am using seems to have gone from their website. not a great loss, it was nothing special but ok in my stampe.

Low oil fuel on the new 155 is no problem. I test run all the new engines on it so by all means crack on.

[Danny Fenton]

Thanks Jon, I picked up fuel and a Mentz 20x6 from Webbies yesterday. So I think I am good to give it a go at the weekend. Bike clips at the ready......

Cheers

Danny

[Jon H]

Im dragging this question over from the other thread as it belongs here.

'My Laser 300 was bought second-hand some years ago it is the earlier mark with the square design and Irvine carbs. I have flown it a few times but it quite often has a problem when one cylinder goes out. I checked the carbs and the link rod was set so that they were not working in synch. Not only were they were not opening together but the control arms were set at different angles which meant the linearity would have also been different. I don't think the previous owner would have messed with this. I re-adjusted the carbs to work together as accurately as I could but still had problems with dropping one pot. I am now considering using an OBG but this shouldn't be necessary. I am using Irvine contest10 fuel and OS F plugs.

Any advice would be gratefully received.

Andy.'

Yep OBG is not needed and not recommended. If a cylinder is dropping out then its politely telling you something is wrong.

We set all of the link rod lengths and arm angles at the factory before the engines leave. If they are wrong, its because someone messed with them. I know, its unheard of for a modeller to mess with something, but it happens. Engines are now shipped with fixed length link rods to try and discourage the fiddlers.

Ok so F plugs are recommended and no problem there, contest 10 is awful in almost every way (messy, expensive etc) but it will not be causing this problem. If you fancy a fuel upgrade grab some laser 5 (use in all engines) or some laser 5 pro (use only in lasers). Both have less oil, less mess, are cheaper, and offer greater economy.

The first thing i would do is check for end float in the carb barrels. Irvine carbs wear over time and eventually the carb barrel is flapping up and down with engine induction pulses. This changes the mixture and makes it almost impossible to get a nice reliable idle as well as generally messing up the tuning. To check them, open to half throttle and push/pull the barrel in/out and see how much it moves.

If they are ok then the next things i would look at is what prop you have and what rpm you see at full power. This will give an overall impression on the health of the engine. Then its the usual. Is compression strong and (most importantly) even across both cylinders, are the valve clearances ok, does the engine over heat, does it always stop at the same time in a flight, is it always the same cylinder, are you running it 'a bit rich for safety' (if so, dont), and finally does it die at idle, full power, in the middle?

Answers on a post card

[Andy Stephenson]

Jon,

Some of your questions I don't have answers for right now but I'm fairly sure the carb barrels are free as I closely attended to them when I was adjusting the linkages. The valve clearances were set using the Norton method as originally recommended by Neil. I'm running a 20x8 Airflow wooden prop. The compression is good on both cylinders, I have just checked this but it has some thickened oil in it so I can't be certain.

It's a while ago when I last ran the engine so I can't say if it was always the same cylinder that stopped firing. When this happens there is still enough power left to get the plane down safely but the loss of power on a 6 foot biplane is noticeable. I will invest in some laser specific fuel before next season.

Andy.

[Jon H]

Hi Andy

Thats fair enough, its rare people have all the answers!

As for the carbs, its not the rotation that is an issue its in/out end float. Its a problem as moving the carb barrel in leans the mixture and this happens each time engine sucks for more fuel. Not ideal clearly

Not familiar with the norton method. A google search gives me something to do with bikes? Its not important as there is only one way to do it really. TDC on compression stroke, both valves closed, .1mm or 4 thou when cold. So simple even a politician could do it

[Andy Stephenson]

Jon,

I just now checked the end floats and they are OK. Originally back in the 80s when I bought my first Laser engine(75) when Neil was still involved, the instructions for adjusting the valves was to tighten until you can feel the slightest free movement and that will get you to the correct clearance. As the 300 didn't come with instructions this is how I have been doing it. Is it more critical than that with the newer series of engines.

Andy.

[Andy Stephenson]

Jon,

I have been stripping down my Laser 150 in order to de-gunk it and fit new bearings. I am having trouble removing the prop driver to get access to the bearings in the front housing. My hub puller simply won't move it and applying large amounts of heat has no effect. Do you have a trick for getting it to break the taper.

Thanks,

Andy.