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Member postings for Jon - Laser Engines

Here is a list of all the postings Jon - Laser Engines has made in our forums. Click on a thread name to jump to the thread.

Thread: Replacement Carb for OS FS70 Surpass?
22/11/2020 23:32:10

Out of curiosity why are you changing the carb? about 90% of the folks who call me for a new carb dont actually need one and a few O rings and a bit of cleaning is a bunch cheaper.

Thread: The Threat of Overpricing
21/11/2020 15:51:59

There are a great many things threatening the hobby, and one of them is modelers who want everything for free.

Normally i would be the first to call out a crazy price, but i have to confess i am really not seeing it this time. £200 for a fully functioning model that is ready to fly is cheap and dont forget that at least 20% of that is tax.

When i used to work at a shop i can recall instances where you would sell something like a £500 starter pack of a 40 size trainer, engine, radio etc etc and the profit from that would barely fold. I suspect there is more value in change on the floor of my car if i count up all the escaped coppers!

People used to spend a weeks wages on one servo. Frankly, i dont know how they can make it for the money.

Incidentally, that tube of epoxy you bought probably has up to 10 times the mark up on it that your acrowot kit does. Even more if you got it from BnQ.

Edited By Jon - Laser Engines on 21/11/2020 15:52:44

Thread: Laser Engines development.
19/11/2020 12:17:50

I received this as a pm but its likely others have the same question so ill pop the reply here

'Hi Jon, was wondering if you had any particular plans models in mind for the new inline engine you have been working on. Will they be produced in a range of sizes?'

Ok so i designed the 200 inline to fit the DB Spitfire. Why the DB Spitfire? because i have one and wanted an inline twin for it. It is also representative of other 80 inch WWII fighters of 18ish lbs so seemed a reasonable benchmark.

While musing about this with a customer he mentioned that his Mick Reeves 1/6 Spitfire would also be rather tasty with an inline and asked if it would fit. As it happens, it did, but the cylinders were too tall so the 160 inline was born. Same crankcase, shorter stroke and cylinders. A little investigation revealed that this engine would also fit something like a YT/ESM Mustang assuming it was appropriately modified.

While on the hunt for suitable models i checked out my precedent 1/4 stampe to represent tiger moths etc and settled on the dimensions we have. Essentially, i did check that the engine was within reason and used the models i had on hand/had details for to make sure it was all in the ballpark of fitting a given genre.

This was as far as i felt i needed to go as the models i checked would all need significant modification anyway so i was not looking for a drop in fit. The model will need to be built around the engine so i did not bother trying to mass a list of perfectly suited models as none of them are, all will need work to make it happen.

So, with all that said i would expect that any 1/4 ish scale inch tiger moth, chipmunk, stampe etc will accept the engine and i have a dedicated version in mind just for those models. I would also expect that 70-80 inch warbirds would also suit (i wish i still have my pica p40!) and there are plenty of models in both of these classes.

Over time i am sure we will build up a database of models that are best suited but in truth these engines are aimed at the sort of person who has a plan, a pile of wood, and the ability to adapt those to make it all happen with the engine. If that is too much for you its no problem, the 155 or 180 single cylinder will do the job. If you want the twin, its kinda part of the deal. That said, i have some other ideas and if everything works out i cant see why i could not work with someone like DB models and offer a conversion kit or something with the modified parts in the box. I cant do that with Brian Taylor models etc, but there are things we can do once we are further down the track.

As for larger sizes, i have two 5th scale WWII fighters in need of a 50/60cc inline. I have also had submissions of plans with dimensions from two other customers covering the Topflite Giant scale and ziroli 95 inch Mustangs so that any potential future engines are made with those in mind. Again though, my 89'' P51 seems very representative of the breed and i cant see any issues. If someone has a 3rd scale tiger moth plan that might be useful to measure up

Thread: Seagull Hurricane
15/11/2020 21:53:26
Posted by Robert Bean 1 on 15/11/2020 20:50:23:

Jon, you may be right. Just giving my opinion. Anyway, set up as it is my Hurricane now flies ok.

And to be fair, it flying well is all that matters. Im just annoyed that the model is such a moose as a great many people have been sucked in by a great looking model and i doubt many survive long

15/11/2020 15:00:38

Yea Tim's model is not tail heavy and its trim neutral in level flight. It would be fine if the rest of the aerodynamics were correct.

My smaller 62 inch hurricane had similar traits to the SG version and it turned out the incidence of the main wing was wrong. With this corrected as best i can it performs well with a scale size tail. Its not perfect, but i couldnt completely fix the wing.

The size of the tail is only relevant when control inputs are not being made. The Hurricane is over sensitive in pitch and this would be improved if the tail, and by extension the elevators, were smaller as they would be less powerful. Again though, the divergence we see is due to the c/l crossing the c/g and changing all the pitch moments. You can get around that by making the model nose heavy, as you have.

In the case of the design, they would have been better getting the wing section right, as its a mess at the moment, and then make sure the incidences are correct. I have also flown a number of scale models with oversize tails and it makes them worse. Certainly i always use scale tails on my models where i can and the ones with smaller tails do fly better as the elevator is less sensitive.

Flying inverted to test c/g is also not a great idea as it depends very much on wing section. A flat bottom wing model wont fly inverted very well at all no matter the c/g!

14/11/2020 14:12:32

Tim, when we get out of lockdown and i can come visit i might poop over with my incidence meter and see what we are working with as i have a sneaking suspicion its all wrong.

14/11/2020 10:19:52

HI Robert

Your comments back up my original thinking in that there is a major aerodynamic issue with the model. Namely, the c/g and c/p are very close together and they cross each other in flight which makes the model very unstable in pitch.

Your solution, essentially making the model really nose heavy, solves the problem by moving the c/g out of the way but this obviously demands the undercarriage mods as well.

On the bright side, i suppose this proves that the model itself is just broken and nothing we have done has caused the problems. Its not like we got the dodgy friday afternoon model either as we now have at least 3 models documented with these same problems. Its also good to know that there is a 'fix' of sorts that means the models can at least be flown and not condemned to the bonfire.

The downside of course is that a great many people will buy these in good faith only to be badly let down by its flying performance.

Thread: Wing accuracy
14/11/2020 10:12:43

Cuban is right. I always aim for as close as possible but i dont waste time measuring everything to make sure its mm perfect so dont loose sleep over it. As long as both wings are similar, you will be fine but pay attention to twists in the wing. This is far more important than an extra half inch of span.

The only thing that really matters beyond the wing is that the tail is square to the wing. you can do this by eye. I have measured up models in the past and got them spot on, only for the whole thing to look crooked when using MkI eyeball.

My method is to assemble the model, then stand about 8 feet away in front of it and sight down the fuselage by kneeling down. Normally you get to a point where one side of the tail 'touches' the wing but the other does not. I then adjust it so they match. standng up on a chair and looking down on the model is normally enough to get the tail straight.

Thread: Identifying Laser Engines
12/11/2020 08:17:17
Posted by robert chamberlain on 12/11/2020 03:49:46:

So,-----I am still confused on Laser identification. Just what do the model numbers mean? If I see an add for 180 it means nothing to me. What is it referring to?

Cymaz has it right. All glow engines since forever have their capacities given in cubic inch. Petrol, for some reason, have theirs given in cc. So a 25cc petrol and a 155 glow are the same size more or less in terms of capacity.

In basic terms, a 60 is 10ccc, a 90 15cc, a 120 20cc, 180/200 is around 30cc etc.

In the past model diesels would often be sized in cc like the AM10 at 1cc, AM15 at 1.5cc, PAW149 at 1.49cc...

Thread: Gary's Brian Taylor P-47 build
11/11/2020 16:47:06

Looks really good Nick.

The exhaust is a concern as my thermal gadget tops out at 300c and it reads overload when i pointed it at the muffler body. The EGT is likely to be higher. I recommend you install a shield of some kind between the exhaust tubes and the tank as any break will blast hot gasses on the tank. It wont take long to burn a hole through the tank and that could be a bad day!

I had an exhaust break on my 360v once and the exhaust gasses burnt through the fibreglass fuse and half way through the 3/8 ply firewall in under 5 minutes.

I dont want to be a harbinger of doom but i would not be confident about its long term survival. I could be wrong, and hope i am as it looks cool, but i would keep a really close eye on it.

Thread: 100 degree retracts
09/11/2020 18:58:33

check out electron retracts in spain. a customer told me he was very impressed with them

Thread: Laser Engines development.
08/11/2020 21:26:11

There have been so many alterations over the years even i struggle to keep up. If you take our 100 as an example, it was introduced in 1992 and has 5 distinct versions and at least 2 more variants of the same version. Most of the other engines in the range are similar and its why i always need a photo when it comes to working out what an engine is as there is more to know beyond its size.

08/11/2020 14:52:33
Posted by John Stainforth on 05/11/2020 19:02:02:

Jon, actually my 200V does 6800 rpm on a 20 x 6 prop, not a 20 x 8. Also, it is difficult to compare the sound with your video properly, because on the 20 x 6 prop my 200V was really chucking out the dB's.

That sounds right. I expect 7k +-200 on a 20x6 for a 200 and thats why the inline surprised me a bit doing nearly that on 20x8.

Chris, thanks for that. The petrol has not been forgotten, its just that this project is on the go and i want to get it finished so its not hanging like the petrol was.

Nick, yep, but then again that would not be difficult

Andy, we have made our own carbs in house since 2006.

05/11/2020 10:49:51
Posted by Nigel R on 05/11/2020 10:40:55:

Jon, is the inline firing 360 apart? Compared to, 270 apart on the V?

yep, 360

05/11/2020 10:30:20
Posted by John Stainforth on 04/11/2020 17:56:36:

Sounds identical to the 200V. Also the RPM is the same as I got on that engine with a 20" prop.

Tim, I have managed to start my 200V with only one glow igniter.

Thats interesting John. At the factory we have all agreed that it sounds quite different to the V and might even think it sounds better. I have not tested a 200v with a 20x8 recently but last i checked it was slower, around 6400 if memory serves. That might not have been an apc though, i cant remember.

Next time i run a 200 i will check it out

04/11/2020 16:52:56

Ok, you wanted a video so here we are.

Prop is a 20x8 apc, quite a load for a 200 4 stroke but as you can see, its no problem at all!

Sorry for the wobbly video, i need more arms. Also the mount is not the one it will come with, just something for testing

Edited By Jon - Laser Engines on 04/11/2020 16:53:27

Thread: Laser Engines - Technical questions
04/11/2020 16:07:52

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

04/11/2020 14:53:45

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.


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

Thread: Laser Engines development.
04/11/2020 14:40:59

Hi Andy

Im going to kick this over to the technical questions thread so we dont get too far down the rabbit hole over here.

04/11/2020 13:49:17

A little off topic but ill pop it here anyway

For those worried about setting 2 carbs, its as easy as it looks. This video was done for a customer who wanted to see their engine on its factory test run. The engine was new and had not been run prior to the video.

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