Laser Engines - Technical questions

[Don Fry]

Posted by Frank Skilbeck on 15/07/2019 15:40:00:

Just reading the last couple of posts for large slow biplanes with a 180 using a 20 x 6 prop, I have just acquired a Mick Reeves 1/4 scale Camel with a 200v , it's currently fitted with a Graupner 16 x 8, would a 20 x 6 be more appropriate, I have a wood Powermax 20 x 6 I could try.

Edited By Frank Skilbeck on 15/07/2019 15:44:28

Please tell me, either the motor, and/ or the airframe is a wreck.

[Frank Skilbeck]

All, thanks I'll start with the 20 x 6.

Don, sorry no, the motor hasn't had much running and the airframe although built quite a while back has only flown a couple of times. Just need to replace the undercarriage and tail skid "springing".

[Don Fry]

Cow.

if not a state secret?

Edited By Don Fry on 15/07/2019 22:23:30

Edited By Don Fry on 15/07/2019 22:24:51

[Dirk Witvrouwen 1]

How critical is the methanol purity for the engine's health? Meaning, as of what purity % is the methanol OK for use?

I understand that lasers can run without nitro, if not too cold. Above what temperature are we talking to hold a fair idle? Or is this rubbish; and is the 5% nitro a necessity for all but the brave?

I'm asking since the locally available glow fuel seem dodgy, they don't even state the oil % properly, let alone the type (I called the hobby shop to check, they did not find the oil %).

[Frank Skilbeck]

Well I ran the 200v on a 20 x 6 and it started and ran well, no test flight though as a faulty throttle servo wouldn't let me get a slow enough idle. But the laser sounded superb and was very smooth, much much smoother than a DLE 32cc petrol I have in another model.

I ran it on on Southern Model crafts 10% nitro synthetic initially, but think I'll try 0% nitro synthetic next time (having run my Laser 61 on 0% in the past with no issues).

[Jon H]

Dirk, i would always recommend you find the best quality methanol you can. Any water in the fuel can cause erratic running, poor reliability and corrosion within the engine. You are right to be wary of fuels that do not list their ingredients. We do not warranty engines run on fuels where the contents is not known.

On the nitro side, more than 5% is not of any real advantage and does little to improve performance. Above 5% nitro fuel consumption will also increase exponentially as % of nitro increases.

[Dirk Witvrouwen 1]

Thanks for the replies relating nitro percentages.

Once my 180 arrives, I'll probably be using Hobby-In mix initially. Their standard mixes use a minimum of 20% Klotz though.

https://hobbyin.nl/product/brandstof-met-klotz-olie/  (edit, added link)

I'll await the arrival of my 180 before purchasing anything; assuming the engine comes with break-in instructions/requirements.

Edited By Dirk Witvrouwen 1 on 21/07/2019 12:26:57

[Don Fry]

Dirk, given that your proposed fuel has a high oil content, it could be mixed 50/50 with laboratory purity methanol (99.85% or better), to give a 10% oil fuel. Use a 10% nitro methane base, if you want to end up with 5% fuel at 10 % oil.

if you are nice to Jon, and supply a list of ingredients I believe he will OK it's use with the warranty still valid.

[Jon H]

Don beat me to it. Grab 10% nitro and 20% oil fuel then cut it in half. 5 nitro and 10 oil will be fine.

There are instructions in the box but assuming you have the right prop and plug fitted,  follow these simple steps for running in the engine. 

Start engine
Tune for max power. 
Fly

Thats more or less it. Dont run it rich, dont faff about on the ground for hours and hours, dont panic. Just start and fly. 

Edited By Jon - Laser Engines on 21/07/2019 16:20:37

[Frank Skilbeck]

Sorted the servo out on my 200v, on 10% nitro, it's turning the 20x6 around 6300 rpm, does that sound about right?

Plenty of thrust, should get to fly the model this week sometime.

[tigerman]

Having real problems with my Laser 80 .it has not had a lot of running .It started going dead stick on me a lot .Tried everything I can think of ,clean the carb out ,check the valves etc .Finally took it out of the model and put it on a test bench to make sure the tank and everything was in the correct place .Now it will only run for a few seconds and stop .It does not seem to be drawing in the fuel .Mind you I have made things worse but completely fiddling with the idle setting .Now I do not have a clue how many turns the idle setting should me .I really have screw the setting up .Might have to see if Jon can fix it !!!!!!!!!.Looks like a phone call to Jon tomorrow and hope he is not to busy and then hopefully send it off to Jon 

Edited By tigerman on 16/09/2019 20:01:58

[Former Member]

[This posting has been removed]

[tigerman]

Thanks Andrew .That could be the problem .Just looks it up and the correct setting for the idle jet was 7 turns out .Mmmm mine was 3 .Just set it at 8 turns out turn and it cough and splutter but then it sprung into life and look promising .It is a bit dark out there at the moment but I had it running for about 5 minute and then shut it down .( do not want to upset the neighbor .I will give it another go tomorrow when it is not so dark .I take it the idle jet was almost closed with only 3 turns out .Would that affect the running of the motor or would that only effect the slow running of the motor ? Any how it is a lot better now Thanks

[Martin Harris - Moderator]

The idle needle setting is significant to probably 3/4 throttle and works in conjunction with the main jet throughout its range. It looks like Andrew has hit the nail on the head...

You may have (or have had) a partial obstruction inside the carb. If I suspect this and can coax the engine to run at full throttle (judicious finger on the exhaust or air inlet if no pressure is being used) once running at WOT, that finger gets used to choke the engine momentarily and draw the obstruction through. If you do try this, be extremely careful though.

Alternatively, a wide open needle valve and my u/c pressurising bicycle pump applied to the fuel inlet performs a similar function - cycling between that and removing the needle and pumping with the magic finger over the carb throat a couple of times usually works wonders...

[Former Member]

[This posting has been removed]

[Jon H]

The correct settings on the needle are the settings at which the engine runs correctly. What those settings are for your engine in your model is anyone's guess

To be clear, starting at 2 on the main and 7 on the slow will more or less guarantee the engine will start but it will still need to be tuned up from there.

So much depends on the specific installation you have in the model and then obviously things like prop, plug and fuel all play their part as well.

When i took my 300v out of my La7 and fitted it to my P39 i had to make huge changes to the settings even though both models had the engine inverted and i was using the same prop, plugs and fuel. Just the fuel system setup was different and it made a huge difference to the needle settings as the mains went from only 3/4 open to just about 1.5 turns open. I cant remember what the slow runners did, but they moved a bunch as well.

The fact that your engine was working in the model and now isnt suggests a fuel system problem or a blockage. I have this exact issue with the right cylinder of the 300v in my P39. It keeps going out after about 6 minutes in the air and as the engine has been reliable for years and cleaning the carb has not fixed it then there must be something wrong with the tank or plumbing. Clearly you are in the same boat.

playing with the idle needle is not a problem, in fact many issues can be fixed with a slow run needle adjustment as they can creep over time. If the original settings have been lost it should be a very quick job to fix it as the engine will usually tell you everything you need to know.

If you have compression, glow, and fuel the engine will fire. It might not run, but it has to fire. If it wont fire at all one of those 3 is missing.

If the engine runs for a short time and stops, especially if you prime it before the start, again the engine has told you the problem and is waiting for you to fix it. Simply put, it ran on the prime and then exhausted its supply of fuel. Clearly it needs more fuel at idle, and that is controlled by our good friend the slow run needle. Just open it a bit and try again. If that isnt enough, keep going until it works!

I keep meaning to try and shoot a video showing how to diagnose this sort of thing but its both difficult to shoot and i am too cowardly to stand in front of a camera

[tigerman]

Now reset the idle jet to 7 turns out then done some fine adjustment to get the tick over and pick up just right then reset the main jet and the Laser is working fine again .Lesson 1 DO NOT MESS WITH JON SETTING .Leave well alone and the Lasser will be fine !!!!!!!!!!!!!!!!!!

Edited By tigerman on 17/09/2019 16:12:06

[Jon H]

I always recommend messing with the setting as there is no way i can set it right from the factory to suit every model.

Good to hear its working though.

[tigerman]

Next Question .Now I have the Laser 80 working fine I put it in a Seagull Junker C1 According to the manufacture this model needs a 90 4 stroke .Mmm should of listen to my brain and not the manufacture ,just maiden the Junkers C1 with a Laser 80 and wow to much engine .The most you need in this model is a 70 4 stroke ( or even a 60 4stroke ).To get the Junkers to fly scale like with Laser 80 I am flying it on just over tick over , I am using a 14x6 prop .Would I be better buying a 15x6 prop or would this make it worse .I do not have a 15x6 prop to try it ,just thought it would be better t get an expert advice before I brought a 15x6 prop

[Martin Harris - Moderator]

Posted by tigerman on 17/09/2019 16:05:47:

Now reset the idle jet to 7 turns out then done some fine adjustment to get the tick over and pick up just right then reset the main jet and the Laser is working fine again .Lesson 1 DO NOT MESS WITH JON SETTING .Leave well alone and the Lasser will be fine !!!!!!!!!!!!!!!!!!

Sounds like you've got a result.

As a general rule of thumb on an unknown engine, I always start deliberately rich on both top and bottom ends (a rich engine runs badly and cool, lean may not start and may run too hot if it does) and tune the top end first (remember that the feed to the idle jet is influenced by the main needle setting) then tune the idle and recheck the top end as the idle setting has a small(er) influence over the top end. Recheck until neither need further adjustment.

[Former Member]

[This posting has been removed]

[Martin McIntosh]

I have a few Lasers and YS`s, all of which run on the factory settings with just a few minor adjustments. Managed to buy a number of YS motors at half price because the guys did not know the start up procedure and started to fiddle with them. No way that one of these will start if the idle needle is screwed out more than 1 1/2 turns or the pressure not built up before applying the glow.

I did not need to touch anything on my latest Laser 180 but it will require minor adjustments after a few runs no doubt.

Occasionally you may need to tweak the top end to suit conditions on the day but I see a lot of dead motors at the field due to the carb. fiddlers; after all, you do not tune up your car or lawn mower every day, do you? If a motor was running fine the last time out then a problem must be due to a plug/fuel blockage or a leak.

[Jon H]

Posted by Andrew Ray on 17/09/2019 16:32:40:

Posted by Jon - Laser Engines on 17/09/2019 16:08:32:

I always recommend messing with the setting as there is no way i can set it right from the factory to suit every model.

You are too modest Jon

Not really, i can only set the engine to suit my test bench so they always need adjusting to suit the model they are fitted too. It might only be 1/16 of a turn on the slow run, it might be a full turn, but they will all need a little tweak

 

Tigerman, just looking at the specs for the Junkers i would agree with you. At 9lbs and just shy of 70 inch i would recommend the 70 as its the smallest engine we do. If you want to tame the beast a little then a 15x6 will help as it will reduce rpm and make the model feel better. I use a 15x6 wood (cant remember the brand) on my 80 powered Hurricane and the performance is good. I keep meaning to get a master 15x6 as it will suit this model even if they are rubbish props.

Kit manufacturers dont always get their engine recommendations right and they usually lean towards overpowering to guard against heavy builders and (i suspect) the american market. The topflite 60 size warbird series are a classic example as the top end 120fs they recommend is just crazy in a 60 inch model. Seagull did the same with their gipsy moth (120 recommended when an 80 is plenty) and black horse did it with their 45cc chipmunk which is just fine on engines as small as 20cc. 

 

Edited By Jon - Laser Engines on 18/09/2019 08:30:35

[tigerman]

Thank Jon I will try a 15x6 prop and see what happens

[Chris Berry]

Thanks to Jon for his advice today.

My 300v in my Flair Stearman was dropping to one cylinder once the glow stick was removed at low throttle. A quick call to Jon and engine was sorted and I flew it two more times.

A lean out on the slow needle and all was well.