Laser Engines - Technical questions

[Ron Gray]

1 hour ago, Andy Joyce said:

impossible to lower as it currently sits flush with the wing seat

If this means that the tank is sitting on top of the wing then cut out a 'box' in the wing, line it with lite ply or balsa then glass it. That's what I've done with my warbirds:

 

Mustang

 

 

 

Hurricane

 

 

 

 

[RottenRow]

Andy, are you sure that’s a 70? The glowplug being at the front suggests it's an earlier engine (61, 75 or 90 perhaps?). As does the small silencer.

Anyway, the Super Tigre carb that is fitted has its spraybar assembly fitted the wrong way around (180 degrees out). It’ll never run correctly like that. Remove the two screws, lift out the spraybar assembly (the whole brass bit shown in your photo where the fuel pipe attaches), turn it through 180 degrees and refit it. Then try the engine again.

This is necessary to put the jet orifice in the correct position in the airflow, which is towards the engine.

Brian.

[Mike Mc]

On my 70 the size is stamped on the left mount. My 70 also has two valve cover screws.

 

[thebluemax]

Hello Jon,

Any updates on when the FT-310's will be ready?

thanks,

Bill

[Jon H]

15 hours ago, Andy Joyce said:

 

 

Having just had a look at the tank it will be impossible to lower as it currently sits flush with the wing seat.  So assume I will have to live with the dripping fuel from the carb.

 

its why they invented power tools, nothing is impossible 🙂 Whatever is in the way, just cut it out. If what you cut out was important, build something new to replace it. 

 

The engine will never perform correctly with the tank in the wrong place and i cannot troubleshoot any engine if its installed incorrectly. If asked to, my answer will always be the same...move the tank. 

 

I commented on another thread that there is a 'that'll do' attitude in aeromodelling and my answer is always the same, it wont do. Get the basics right, install everything correctly and go from there. So many problems are down to bad initial setup and while it might be a bit of work to move the tank, modify the wing and fuz etc, is it more work than fighting with a model week in and week out? worrying the engine might stop and generally not enjoying your flying as the engine is not offering you any confidence is hardly a rewarding experience. I have seen so many times people take a shortcut on a build to save themselves a few hours only for this to compromise a model which may be flying for many years. I am not trying to single you out Andy or 'name and shame' anyone, its just that I made this mistake myself a long time ago and now i just do what needs to be done. Its so much less hassle long term and i just had to stop myself being lazy. i always knew the right way to do things, i just didnt as it seemed less work to bodge it. Sadly, it isnt. 

 

Ron's suggestion is spot on and i mod my leading edges in the same way. You could probably do the whole job in an hour and i suspect you will spend longer waiting for the epoxy to dry and you will doing the work. It looks intimidating but it isnt a big job. 

 

RR is also correct, the engine is one of our discontinued line (probably a 75) and looking at the needle it was manufactured some time before 1986. His comments about the spray bar are also correct most of the time, but there are a few engines out there where the position you have is correct. They are a rarity though. I recommend you do as he suggests but double check the slot in the spray bar is facing towards the valve even if that means you put the thing back together exactly as it is. 

 

Bluemax, wrong thread mate 😉 I am waiting on crankcases still. As soon as i have news i will post it on the development thread. While im waiting i think i might take some time off soon as i have only had a week off all year and i cant get much done at the moment due to the continued valve spring saga. I have some saved for the bigger FT's, but that is all i have so nothing much else is happening. 

[thebluemax]

3 hours ago, Jon - Laser Engines said:

Bluemax, wrong thread mate 😉 I am waiting on crankcases still. As soon as i have news i will post it on the development thread. While im waiting i think i might take some time off soon as i have only had a week off all year and i cant get much done at the moment due to the continued valve spring saga. I have some saved for the bigger FT's, but that is all i have so nothing much else is happening. 

Oops, sorry, my bad.  In the future I will make sure I am in the right thread.  Thanks for the update.

[Jon H]

5 minutes ago, thebluemax said:

Oops, sorry, my bad.  In the future I will make sure I am in the right thread.  Thanks for the update.

 

no worries, it just gets complicated having the tech and development stuff all in a jumble

[Andy J]

19 hours ago, RottenRow said:

Andy, are you sure that’s a 70? The glowplug being at the front suggests it's an earlier engine (61, 75 or 90 perhaps?). As does the small silencer.

Anyway, the Super Tigre carb that is fitted has its spraybar assembly fitted the wrong way around (180 degrees out). It’ll never run correctly like that. Remove the two screws, lift out the spraybar assembly (the whole brass bit shown in your photo where the fuel pipe attaches), turn it through 180 degrees and refit it. Then try the engine again.

This is necessary to put the jet orifice in the correct position in the airflow, which is towards the engine.

Brian.

Well it could only get worse and it did! Went to check the direction of the spray bar orifice and found it was NOT 180deg out as the orifice faces the engine block. On refitting unfortunately although one screw went back in ok the other cross threaded and sheared.

Tried to drill the screw out but the drill followed the softer path and broke out of the casting.

So if this is an ST carb then probably need a replacement. Possible the single screw may hold the inner barrel in place but have my doubts.

 

Edited September 28, 2022 by Andy Joyce

[Jon H]

6 minutes ago, Andy Joyce said:

Well it could only get worse and it did! Went to check the direction of the spray bar orifice and found it was NOT 180deg out as the orifice faces the engine block. On refitting unfortunately although one screw went back in ok the other cross threaded and sheared.

Tried to drill the screw out but the drill followed the softer path and broke out of the casting.

So if this is an ST carb then probably need a replacement. Possible the single screw may hold the inner barrel in place but have my doubts.

 

 

oh dear. Those carbs were discontinued in 1986 and spares are non existent. Current carbs will not fit so you might have to glue the beggar in with loctite or epoxy in addition to the remaining screw

[Andy J]

1 hour ago, Jon - Laser Engines said:

 

Well going on your advice Jon I applied both lock tight to the existing screw and some araldite to the inlet so don't think it will now come lose.  Whilst that was drying also applied the  to the wing retaining bulkhead to remove about 1/2 inch which will allow a lower tank position. Once the tank is re-installed I can then hack a hole in the wing as per Ron's design. Just hope the effort is going to be worth it!

11.2v Rx power Lipo also had to come out, but cant see how I can refit this above the tank so have reverted to a 1500mah 6v subC but have concerns this will too low in capacity given the heavy duty electric retracts I fitted last month.

[Paul De Tourtoulon]

I have an old ST carb barrel int 9mm the engine side 15mm, it looks like this one,,, any good to you ?.

 

Edited September 28, 2022 by Paul De Tourtoulon

[Andy J]

Thanks very  much for the offer Paul. Whilst 90% of your carb looks the same the big difference is the fuel-air extension pipe that allows the carb to sit behind the cylinder.  Not at all sure how this part is removed  or changed.

[Nigel Dell]

To be honest you would have to get a spare from a laser, I am sure Jon will advise how this put together, as long as the spigot is the right size it should be a straight forward swap, the added bonus is Paul’s carb has the later ratchet needle assembly.

personally I would look into this route  as being a doable solution.

[Nick Somerville]

Regards the power for the retracts:

I have Er40 Electron retracts in my P47 but power them with a separate battery in the wing connected to the sequencer. It’s a 8ooma 2s LIPO  and lasts for ages (10+ sorties and several months between charges. Peace of mind knowing there is no possible drop in voltage/current to the rest of the model when deploying gear. A small 500ma would be more than adequate and hardly a weight concern.

[Jon H]

Im with Nick, always use a separate battery for electric or servo driven retracts. 

 

Lowering the tank will be worth it but only if its lowered enough. Top of the tank, centre of the carb. Line 'em up and its all good. This is how my 63 inch Hurricane with an 80 fitted ended up looking 

 

 

Nigel. The intake stub extension is a pressed item and its doubtful you could remove it without damage. Current intake stubs are not compatible with the ST carb or the 75 engine. I deliberately modified the design in 2016 to break compatibility. Why? We were in a position where we could take £100 off a customer for carb and exhaust replacement and the engine would still be rubbish with no other spares available. These engines are over 30 years old and its time to throw them away if they are broken.  

[Andy J]

Well managed to accommodate the current 3S lipo Rx battery by letting it into the servo tray so will go with that for the moment.

 

Shame about the spare ST carb not being an option as that would have been a simply solution to the problem.

 

 

[Jon H]

19 minutes ago, Andy Joyce said:

 

 

Shame about the spare ST carb not being an option as that would have been a simply solution to the problem.

 

 

 

That carb was discontinued by ST themselves around 1986 and replaced by another type which we stopped using in 1995 and was totally out of production by...2005? Something like that. In any event, as both the engine and carb were discontinued 36 years ago its never going to be an easy job to keep the engine serviced and maintained. 

[Ernie]

Hi Jon, I've got a laser 150 that I intend to use in a 1/4 scale fokker E111....For various reasons,  I'd like to extend the crankshaft length of the laser (by just a wee bit, say 10mm)

Question, Is this OK, if so, how much is practical, and, in general terms what's the best way to do it?

And yes, I've got a wee yellow lathe

ernie

[Andy J]

On 29/09/2022 at 09:48, Jon - Laser Engines said:

Lowering the tank will be worth it but only if its lowered enough. Top of the tank, centre of the carb. Line 'em up and its all good. This is how my 63 inch Hurricane with an 80 fitted ended up looking 

 

Tank now lowered using the methods suggested! Yet to run the engine so it will be interesting to see if its made a difference.

[RottenRow]

Perhaps I’m interpreting your photo incorrectly Andy, but it looks like the bottom of the tank is level with the carb.

it should be the top of the tank that is level with the carb.

Brian.

[richard dalgleish]

My Taylor Hurricane had a similar tank position to the carb, Laser 120.

It ran perfect for 12 years until i retired the model, no siphoning at all. 

[Jon H]

Ernie - I dont recommend crank extensions as they add load to the front bearing but if its only 10mm then it should be fine. I would just drill a crankshaft size hole through a piece of bar, true up the o/d and part it off at the required length. Then get some 1x2 inch rectangles of 400 grit wet n dry, fold in half and glue to make 1x1 squares with grit on both sides, drill a hole in the middle and place one between the original prop driver and the spacer, and then another between the spacer and the prop/spinner backplate. IF you have the ability to knurl the faces you can probably omit this but i was forced into this exact position on 2 models which were originally set up for other engines. 

 

Andy - Still too high mate, down another inch by the look of it. Tank lowering is an all or nothing sort of situation as anything less than perfect is simply wasted effort. You might save yourself some work by changing the tank to a flatter one. Radio active tanks are wider than they are tall and this is an advantage over the slec. 

 

Richard - If i could have your phone number that would be great. Ill divert all the tank placement related technical support calls/emails i get to you and see how long it takes for you to become homicidal trying to solve them. Im not trying to be rude, its just that you have no idea how many problems this causes. running one engine in one model and having it perform to your satisfaction is not an acceptable level of quality assurance testing to conclude that it is a viable route for everyone to take. If it didnt matter, why would even bother having this completely redundant argument every week? Fitting the tank as i recommend guarantees it will work in every model, on every fuel and on every engine no matter where you are in the world. If you deviate from this and have trouble the only advice i will give is to lower the tank. I cant troubleshoot the fantasy inventions of every modeller on the planet and make no apologies for not trying. If its all installed by the book and running on the right fuel, prop and plug there are very few things that can go wrong and its much easier to troubleshoot. 

 

 

Anyway. Im on holiday until the 10th so you guys are on your own for a bit. 

 

[Martin Harris - Moderator]

19 hours ago, Andy Joyce said:

Tank now lowered using the methods suggested! Yet to run the engine so it will be interesting to see if its made a difference.

 

It's probably the angle the photo is taken from but the engine centre line looks rather low.  It's a very long shot but have you been flying without the cowling fitted and could the engine have been mounted through the bearers on the other side of the mounting originally?  It's most unlikely I know with the lead placement although IIRC those mounts are double sided but it can't do much harm to brainstorm these matters...

[Andy J]

Did ponder last night why the engine C/L is so low in the RW Hurricane but everything does align correctly with the cowl fitted.  Anyway did a quick engine run today. Only a slight drip from the needle prior to start but thereafter once running all seemed ok with no drips. Engine runs the same prior to the mods with a slow tick over and a clean acceleration so it will be interesting to see how it performs in the air. Certainly the fuel supply to the carb is better now having lost a big U shaped bend.

[Andy J]

Is this picture below a latter version of the ST carb?