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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: Acrowot with laser 80
21/02/2019 20:31:24

The old 75 is heavier than our current 80 and the same physical size. You may find it difficult to fit it in the shorter cowl on the ARTF version but its worth a go. Certainly power will not be a problem

Thread: Laser Engines - Technical questions
19/02/2019 14:08:31

The cooling on more or less all of my warbirds, my Airsail Tomahawk and to some degree my acrowot xl would probably all get the 'experts' sucking air and shaking their heads.

Over the years i have seen cowls butchered to the point that i think you could fit/remove the engine without even taking the cowl off. I assume this is due to cooling paranoia? If so its unfounded and it should be noted than the most important thing is flow. If you can get cold in and hot out then you are likely to be just fine. You dont even need that much air to get the job done but it must be able to flow freely.

19/02/2019 10:59:56

Looks pretty good. There is a small gap round the rocker cover but its unlikely to be a problem. All you need now is sufficient outlet area and you should be all set.

You may want to add a support to your exhaust though as a long run of flexi pipe like that is likely to break if allowed to vibrate.

18/02/2019 15:17:42
Posted by Paul james 8 on 18/02/2019 12:30:15:

Interesting stuff Jon, good to get feedback from someone who has tried these mods. I modified an Irvine carb to fit one of my Lasers as I have the facilities to easily do so here. I found it was at least as good as the old Super Tigre style carb and a tad simpler to set up.

The ST carbs were good but under certain circumstances they could prove problematic. The same was true of the irvine carbs and the longevity of the irvine was also a problem. Its because of this that we now make our own.

18/02/2019 12:08:39

We have been asked before about offering an os/saito/every other 4 stroke style intake manifold and the thought process is as follows.

Yes it will work, the engine will run, its not going to damage it.

However, As we tested it years ago we know that throttle response, idle performance, reliability and flooding will all be negatively impacted by the change.

All engines come with certain requirements for their operation and tank-carb height is one of them for all non pumped engines. in our case this means lowering the fuel tank. This also applies to the OS flat 4 and OS/ASP flat twins as well.

The choice then is with the customer. Make the required changes to the model and enjoy the optimised performance on offer from our direct intake, leave the model and as is and have problems running the engine without modification, or leave the model as it is and tolerate less than perfect performance from a modified engine. I know which one i would choose and to date i have not found a model that was impossible to modify to suit the tank position required by the engine. That said, if everyone says they are happy with reduced performance in the interest of not having to modify stuff then i would say you were crazy but would see what i could do to help

I work on the basis that its only wood and my many tools will make short work of that

 

Edited By Jon - Laser Engines on 18/02/2019 12:09:44

Thread: AcroWot XL Build
18/02/2019 11:53:30
Posted by Nigel R on 18/02/2019 11:14:20:

Jon, must be some time sunk into baffling the cowl there! Is is just diverter pipes on the exhaust? Maybe some of those old OS style clamp on jobs that JE sell would sort it? I'm sure you've thought of that already.

I had a few ideas with the exhaust but in the end went for the simplest option which was to solder some brass tubes into steel strips, bolt them to the airframe and connect the tubes to the engine with silicone. I am hoping the silicone can take the heat but only time will tell. I cant hang any load on the header pipes as they will just break. I found this out the hard way on my ASP radial.

The baffles were time consuming but simple in design. I rejected my first idea as it was too complicated and just went simple again with the deflector plates at the front and baffle at the back sealing in the air and forcing it down through the fins. There is then a deflector plate on the outside of the cowl which creates an area of negative pressure in the outlet of the cowl and sucks the hot air out. Again, all of this is the same as used on full size cessna's and such so all i have really done is miniaturise it

Thread: left or right thrust ?
18/02/2019 09:29:56

On my twins i always mount the engines dead straight and i dont bother messing about with opposite rotation. Having owned 5 twins and a 4 engine Hercules the torque argument just dosent stand up. All of those have been i/c.

If you have opposite rotation props and intend to use them then in theory torque is zero so there should be no side thrust needed.

Edited By Jon - Laser Engines on 18/02/2019 09:30:43

Thread: AcroWot XL Build
18/02/2019 08:44:55

Sounds good to me. As the engine is unsilenced i dont know if it will be deemed too loud where i normally fly. From past experience its a little chrisp on the ground but in the air its not loud at all. We will see. If they dont like it then you are likely to see it quite often!

17/02/2019 23:10:04

Nice work Tim. Good to hear the 180 has the oomph!

i am really looking forward to getting mine in the air and i expect to do semi scale aerobatics with it. I really dont want to be ringing its neck, its just not what i am looking for.

When Nick gets his done we should have a meeting of the wots up at the field

17/02/2019 15:40:23

Hi tartan

The grey baffles direct the air up in to the top of the cowl. There is then another baffle at the back that prevents the air escaping and forces it all to go down, through the fins, and then exit out the bottom of the cowling. Its the same setup as used on full size lycoming and continental engines.

The crank is a 3 part affair with the front section containing the prop drive section, front and rear main bearings (in the engine nose case) and then the two crank throws for the first pair of cylinders. The rear section contains the rear pair of throws, a journal for the rear bearing and the gear for the camshaft. Both sections are machined with flats on them and a joining sleeve keeps them together and supports the two middle bearings. For those keeping count its a 5 bearing crank using 3 different sizes of bearing.

Fortunately the crank pins were not in a totally awful state and were cleaned up with some fine wet/dry paper.

One thing OS recommend is that after each flying session the crankcase drain plug is removed and all oil in the crankcase drained out to prevent rusting. I have been following this procedure and the amount of oil that drips out is quite considerable. While the engine is running the drain plug is closed but there is a 2nd nipple for crankcase ventilation.

I am super keen to get it in the air. I just need to get the rocker cover screws, a new rx battery and a sort out a few other small jobs and its good to go

16/02/2019 19:33:38

This engine is the first multi cylinder single carb engine i have used that really needs no on board glow. All of the ASP and saito efforts i have used needed it to keep them alight. If each cylinder had its own carb then glow is never needed but when they share a carb its impossible to match mixture so OS have done well here to keep the mixture pretty even across the cylinders.

I ran the engine again today with the cowl fitted and was pleased with the results. The engine runs hot but happy and it didnt seem to mind a full 5 minutes at half throttle followed by a 20 second run at full power. It didnt falter at all and with the increased cooling it will see in the air i am very confident its going to work nicely.

Thread: Laser Engines - Technical questions
16/02/2019 15:48:43

8500 is good for an apc 16x8 and what they always used to do. I do think they have changed them though as i cant get any of my new 16x8s to run faster than 8200 even on 155's. I cant understand why they would change the design of the prop but even engines i know used to run that fast on 16x8's now run 500 revs slower, even though the run at expected revs on other props. Most strange. APC what did you do?!

Thread: AcroWot XL Build
16/02/2019 12:07:12

Me? never angel

16/02/2019 10:30:26
Posted by Rich too on 16/02/2019 07:47:49:

Haha! I was expecting you to be much older too! That engine sounds awesome - love it. I can’t see how you restrained the model?

I was going to get my restraint but the tail wheel got hooked on the wooden board and was very secure so i left it. I did hang on to it during high power runs though as i didnt think my parents would enjoy having it crash through the window of the dining room.

Today i am going to cut the cowl to clear the exhausts, tidy up the glow cables and order the screws i need for the rocker covers. They are M2.6x7 which is a really stupid size. Thanks for that OS. I also have to do the valve clearances...on all 8 valves :'( 

In terms of performance though the thing is going to be a right beast. The prop was a 19x8 menz wood and she peaks at 7300rpm. thats a calculated 19.8lbs thrust and 2.8hp! i think it will be pretty speedy. 

Edited By Jon - Laser Engines on 16/02/2019 10:34:29

Thread: Seagull Hurricane Laser
16/02/2019 10:28:17

that looks ok Chris, i think you will be fine. I see what you mean about the left hand elevator being low. They dropped a hinge point by the look of it. Also the chap that covered your elevators needs a slap! Unusually poor from seagull there.

One thing i forgot to mention was that with the elevators at a rate low enough to make the model nice in the air you may find it is very reluctant to takeoff. I ended up storming down the runway with full up in and it totally ignored me until it was ready. That is why we added the +15% elevator mix with the gear down, and + another 10 with flap down. What i recommend you do is leave the mixes off (or perhaps 2% just so you know its working) for the maiden but leave the tranny on the elevator flap mix screen. Then, takeoff, get the gear up, trim, fly...whatever. When it comes to landing drop gear and flaps at a high altitude and get an assistant to add to the mix until you get to a point where you feel you are at a good landing approach speed. Then you are all set.

This is how we set Tim's model and it worked out well.

Thread: AcroWot XL Build
15/02/2019 21:21:14
Posted by SR 71 on 15/02/2019 21:12:24:
Wow who is that young handsom chap in the video,
I had an image of a much older Jon
Nice engine and soound

everyone seems to assume im really ancient. Do i come across like a grumpy old man? if so thats probably not gonig to be a good thing in years to come

15/02/2019 17:33:52

Well boys and girls, you asked for it.

Still a bit to sort out. The glow leads need a tidy, cable ties on the exhaust pipes and an extension on the needle. Beyond that, i think i created a monster

Thread: Are all watts created equal?
15/02/2019 12:14:08
Posted by Nigel R on 15/02/2019 11:41:34:

Jon, yes "bigger" props have more braking effect and are inherently more likely to be a lower pitch for a given IC, which suggests more pull at lower speed vs 'getting going' at speed. As you say, suits the model and the flying style. I wouldn't say my sport model choices would be the best fit for scale or slow fly. And a step further away from 3d.

Your pitch comment is interesting as i usually fly with about 8 inches on most of my models. My slower biplanes have 5 or 6 inches, sport 7-8 inch and warbirds are running 8-10. Although this conversation is a bit off topic im just curious what you define as a lower pitch

Thread: Fire Extinguishers?
15/02/2019 11:22:14
Posted by supertigrefan on 15/02/2019 11:15:17:

A couple of CO2's, a bucket of sand and a bucket of water for incidents on the strip, (ncluding dealing with any minor burns) and a few beaters for small fires beyond the strip would be a flexible and responsible plan.

Posted by Jon - Laser Engines on 15/02/2019 09:37:24:

When clearing out the old factory i found an old halon job. Its in my flight box now!

Halon are very effective, just avoid breathing in the products once exposed to a naked flame.

Yup. I only have it for my petrol powered stampe. Im sure a squirt in the cowling intake will do the job. I can then run away from the fumes!

Thread: Seagull Hurricane Laser
15/02/2019 11:20:48
Posted by Chris Freeman 3 on 15/02/2019 09:47:18:

I like to test fly with a little down trim as you will have less chance of the plane taking off at a slower speed than it should and it is easier to hold up than down.

i would probably agree with that, but at this point im so used to holding sticks wherever they need to be that i just dont care any more.

if the trim is badly out the best thing to do is FLY THE PLANE! dont worry about it, dont start trying to sort it out the moment it leaves the ground, dont start trying to faff about with the undercarriage if the thing is a handful, just fly the plane. Get it into circuit, gain some height, get the power back a little and then deal with whatever the problem is. If the model is only slightly out of trim then get the gear up asap, but if you are riding a bucking bronco then forget about that, just get the thing level and then worry about it. If its really bad get someone to beep the trimmers for you. Dont make life difficult by trying to do 3 or 4 things at once and you will get in a muddle and it will end in tears.

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