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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: OS 40 four stroke, inverted?...
06/09/2019 23:57:07

i would say that the tank in pat's example is in fact too high. I would set it up as cuban suggests and essentially have the top of the tank level with the spray bar. This prevents a change in head as fuel is used.

06/09/2019 19:08:51

i agree with everyone else. Inverted should be no problem as long as the tank is in the right place. Make sure the tank isnt too high as the air bleed carb on the little OS will not tolerate a high tank

Thread: Morris gas conversion experience
06/09/2019 13:53:21

I love their enthusiasm, and as it happens it sounds pretty good. Transition is slow/rich but not like the other video.

Its a hefty old unit bolted on the bottom though. Its like another whole cylinder!

06/09/2019 12:25:06

A perfect example of the problems with these conversions. Flat out they can work, but low throttle is usually a mess. From the sound of the idle its only running on one cylinder and you can hear the other two come in as the throttle is opened up.

05/09/2019 20:41:17
Posted by flight1 on 05/09/2019 20:10:02:

the asp is not noisy like a 2 stroke engine and if you use a baffled silencer on each cylinder you will find the noise to be very amicable. two asp .60 size baffled silencers with suitable manifolds will do nicely or make your own.

as for fuel I don't know what you use down under but 15% fully synth modern oil works fine, once run in and if you like straight fuel and know what you doing a lower oil content can be used

Quite right. What i mean is other multi cylinder engines have a nice sound on straight pipes but from some reason the flat twins i have experience with sound really harsh. One is an OS ft300 and it was unbearable. I bodged up a pair of exhausts with parts from work and it then purred like a kitten.

As for fuel, 5% nitro and 15% synthetic is my starter for 10 on all engines these days. As the conrods are pure bronze in the 160 you would likely be fine with 10% oil and probably even as low as 5%. I have not yet run mine on anything less than 15% but there is loads of oil coming out at 15 so i think i will go for 10% when i finally get around to using it.

05/09/2019 15:35:32
Posted by Ted Khinsoe on 05/09/2019 15:15:52:

It’s slated for a 1/4 scale L4 Grasshopper so as long as it stays running I’ll be happy.

that is what mine was for. A friend and i both had models but his crashed before i built mine. As we wanted to fly them together i abandoned the project but kept the engine.

Piers, if there is interest i will step it up in priority from 'one day it might be fun' to 'something for the winter'

One final gripe about the engine is the sound...its awful, or at least it is on the bench. I have two flat twins (160 and 300) and they both sound extremely harsh when unsilenced. My now sold 3 cylinder saito, my 5 cylinder asp radial and OS flat 4 sound fine on straight pipes but for some reason my two flat twins sound really bad so a pair of silencers is recommended.

05/09/2019 09:01:55

I have an ASP version of this engine and my only gripe is the mismatch between the cylinders when it comes to the tuning. My right cylinder always runs rich vs the left up to half throttle. I have never flown it due to a change of plans, but in all my test running its never dropped out at random so i dont think its going to be a problem.

After i changed projects i did set about modifying my engine so it now has laser twin ring pistons and this has helped the compression somewhat. I needs new rings though, i only had worn ones to play with when i rebuilt it.

If i get time i might convert it to twin carb as that will fix everything

04/09/2019 14:44:54

My experience has been very poor.

Many customers return their engines to me for conversion back to glow as they didnt work following petrol conversion.

My own petrol development has demonstrated clearly that its really not as simple as carb swap and ignition. At least not for the level of performance that i deem acceptable.

Thread: Cambrian Spitfire
04/09/2019 14:40:07

Yea it looks much better in that side shot

04/09/2019 12:27:39

Lovely looking model Tim but i suggest you kick the undercarriage forward a bit or it will spend most of its life sniffing the dirt.

If you look at a full size spit the wheels do rake forward quite a bit

Thread: Small engine tick-over
03/09/2019 20:31:42

i wouldnt want to see more than 10500. While i agree 8x4 is a typical prop for a 15 if you can get revs up over 10k with a bigger prop then you are doing just fine.

03/09/2019 15:45:24

There are loads of variables but in general about 3k is reasonable for an engine like that on 'normal' props. Fit a big heavy prop and you might get down below 2500 but why worry.

This is something that crops up often when discussing petrol vs glow. Some use 800 or 900rpm idle vs 1800 for a similar glow as a pro for petrol. My question is why? If the model wont trundle forward on its own at 1800 rpm then any lower than that is of no advantage at all. Its a similar story here. If the idle you have is well suited to your purposes then dont worry too much about it

Thread: Precedent Stampe 1/4 Scale
03/09/2019 15:40:03

Yup, true enough Steve. My stampe seems to stall its top wing first. I can feel it in loops and it also nods forward if you get too slow on landing.

Wing sweep also makes a difference as swept wings tend to pitch up at the stall. Something like a pitts has one straight and one swept if i recall so setting -1 on the top wing vs the bottom would make sense. A great deal would depend on the wing section too. 

I think on my next stampe i am going to build some sort of adjustment into the rigging to allow tweaking if i so desire it.

Edited By Jon - Laser Engines on 03/09/2019 15:41:03

03/09/2019 08:40:29
Posted by bert baker on 02/09/2019 20:48:23:

Does that mean the bottom wing stalls first

You want the top wing to stall first ideally as it makes the aircraft more stable.

On the many biplanes the lift of the top wing is fwd of the c/g, and the lift of the lower wing is behind it. Assuming both are producing similar amounts of lift the forces balance and everything is stable. If you were to then stall the bottom wing only the nose down pitch force it generates will be gone leaving only the pitch up force of the upper wing. This is not very helpful in a stall! As a consequence you normally want to top wing to stall first leaving a nose down force created by the bottom wing to help get you out of the poop.

Thread: A stubborn cam cover on four stroke
02/09/2019 10:00:01
Posted by Martin Harris on 02/09/2019 08:53:06:

Jon's method should be very effective if all else fails - just be sure that the outer cam follower has been removed before you try it!

You may be lucky but that follower is not always easy to remove from the outside, especially on a neglected engine . A strong magnet might help.

Edited By Martin Harris on 02/09/2019 09:00:17

A good point to remember!

But yes, you basically drill a hole through the middle of the cam chest on the side that normally wont open. When i did it on an ASP52 i was very surprised how thin the material was as my drill barely touched it and i was through. A few taps later and the deed was done.

I covered the hole with piece of foil tape if i recall as there is no load on it and its only there to stop the oil sploshing out

Thread: Precedent Stampe 1/4 Scale
02/09/2019 09:55:37

Interesting stuff Bert. Normally i would expect a little more incidence on the top wing of a biplane

Thread: A stubborn cam cover on four stroke
01/09/2019 23:47:26

This problem can indicate that the cam is rusted into the bearing in the crankcase. On a few occasions i have had to drill through the case and push the cam out from the other side.

A 3 or 4mm hole in the opposite side of the cam case will make no difference structurally and it can be sealed easily enough once its all apart and cleaned up.

Thread: OS 40 FP Mixture problem
30/08/2019 13:58:39

Sounds good Roger, just hadnt seen it mentioned

30/08/2019 12:44:12

Forgive me if i missed it, but has the model flown?

I ask as all this faffing about on the ground is fine and worth an investigation, but the problem may in fact not be a problem in the air with the engine zipping along and right up up full temperature. The fuel pooling situation ED mentions is quite right but usually happen at low rpm. when flying around at half throttle or more its usually not an issue.

If its a problem in the air then fair enough, i was just curious if the model had flown or if this was all ground school

29/08/2019 21:31:08

It might go against the grain but you could try running it without exhaust pressure. This would lean it out across the board and might at least be worth trying even if you dont fly with it like that. If it works like this lowering the tank may well be the answer.

I agree with the other comments about the fp series being good engines. I used a pair of 25's in my first twin, my dad still has another pair of 25's in a twin and i have used 15, 20 and 35's in other models with great success.

I current have a 15fp that runs brilliantly on laser 5 with an OS8 plug so that combo should be sound. I am personally not a fan of the enya 3 but it should still work as should the os8 and i think the a3.

I would lean it right out as cuban suggests. If its not sagging then its still got more to go so just keep leaning a click or two at a time until the revs drop a bit and then go back one.

if you like post a video so we can see the beast in action

 

Looks like i was beaten to the post. I also missed cuban suggesting no pressure. Im getting slow in my old age 

 

 

 

 

Edited By Jon - Laser Engines on 29/08/2019 21:33:08

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