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Laser Engines - Technical questions

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Jon - Laser Engines14/05/2020 17:11:09
5511 forum posts
268 photos

Yea i know, horses dont give a rats. The rich people that own them on the other hand demand a 10 mile exclusion zone.

MT Laser 5 fuel is currently 15% oil so you can thin it some for sure. I wouldnt use more than 3/4 gallon though as the ratios get all complicated.

While on the subject of power, i just test ran a 200v. 9400rpm on apc 17x6. Thats 3hp

Martin McIntosh14/05/2020 17:36:43
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3420 forum posts
1213 photos

Jon, are we talking about ADMFC re the horses because this is the first I have heard of it. Got their mail yesterday which said that we can go up next week but nothing else as yet.

Oil. All of my Lasers run very clean anyway but may give the 7% a try.

Jon - Laser Engines14/05/2020 17:47:09
5511 forum posts
268 photos
Posted by Martin McIntosh on 14/05/2020 17:36:43:

Jon, are we talking about ADMFC re the horses because this is the first I have heard of it. Got their mail yesterday which said that we can go up next week but nothing else as yet.

 

Oil. All of my Lasers run very clean anyway but may give the 7% a try.

yep. I asked Peter about flying this weekend and was told its going to be electric only. I asked Mick and he told me its going to be at least 2 more weeks

Its not completely the end of the world, i mean i can fly my electric heli, but as its not flown in 3 years you can tell how much i enjoy flying it vs my planes!

Edited By Jon - Laser Engines on 14/05/2020 17:47:54

Martin McIntosh14/05/2020 18:23:13
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3420 forum posts
1213 photos

I do wish that they would make this clear to the membership. New horses have never been bothered by our models in the past.

Many of my new builds are electric EDF which will all need a hand launch which I don`t want to do on a maiden by myself (+ one i/c, hand launch only). I really just want to go and run motors on the ground at the moment so that should not bother the nags too much. Can probably find a leccy or two to have a go with, Lancaster maybe?

Chris Walby15/05/2020 20:35:04
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1246 forum posts
308 photos

20200515_095542.jpgNew Laser fuel report from todays flying, no problems with social distancing as most of the time it was just me and then the single person turned up for a bit.

 

First up was the trusty 70 in the Acrowot, lovely combination of minimal weight and enough power. Minor problem with the tank bung, but after that started no trouble and warmed up. Once up to temperature WOT needed a tweak (1/4 turn in) and it was maxing out no problem. bottom end and tick over seemed a bit rough, but pick up was no issue. Had a nice flight and seems to pull and pick up very well. It was still a bit rough at the bottom end even at the end of the flight so next time out I'll have the cowl off and set everything back up. Minimal cleaning required smiley

 

Next up was the 180 Yak, fuelled and started no problem and was running just okay as was. Now this beast presents a problem to me as the engine is inverted, exhaust points slightly towards the main needle. I have to tie the tail to the bench, kneel under/to one side and adjust form there, I'll adjust things when I change the cowl for easier adjustments. Once warm it was adjusted with a small turn in the main needle. Taxied out and flew the usual routine of big aerobatics. I normally fly it half to 3/4 throttle, but today it seemed happy to do that or WOT for the nice big verticals and loops. Hardly any cleaning required

Last but not least as I ended up having 4 flights with the pair of 70's in the dual Ace. Start, warm up and adjustment of main needle only to both. Taxi out and a very clean pick up to 3/4 throttle for take of with a nice climb out. Took a couple of circuits to get my thumbs trimmed back in. Slow low passes, fast drop in passes, rolls and loops with not a hint of a problem, Bit of cleaning because the exhaust rubber deflectors had rotated to face the fuselage!

Summary

  • No problems just swap over fuel
  • Minor adjustment on the main if its set up correctly, if not it might benefit from a standard tune up
  • Tick over, pick up and WOT all seem very good and it might even rev out a bit higher or it could be because it seems a bit cleaner between 3/4 and WOT

Right that's me converted and I am actually looking forward to getting the Mossie out (pair of 70's) and seeing how that goes, I think with a bit more pull out of the Lasers it will really suit the more draggy airframe.

As ever, big thanks to Jon for all of his hard work in building, testing and putting up with my questions.

 

 

 

Edited By Chris Walby on 15/05/2020 20:39:35

Tim Flyer15/05/2020 22:55:56
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1290 forum posts
236 photos

My Laser 200v ran great on the new fuel today ... just a bit of main needle tweaking .. I even did a post flight throttle test 😊

**LINK**

Edited By Tim Flyer on 15/05/2020 22:56:50

SR 7116/05/2020 00:24:31
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450 forum posts
140 photos

Where in England are Laser based,

Jon - Laser Engines16/05/2020 01:00:17
5511 forum posts
268 photos

**LINK**

Silver Wolf17/05/2020 17:38:06
174 forum posts
170 photos

Just an initial look at some cooling baffles, I was hoping not to have to cut the cowl. dscn0474.jpgdscn0475.jpg

dscn0472.jpg

A rough estimate gives equal area for inlet and outlet if no cut out in cowl. Not sure if the baffles will enable me to get away with not having to cut the cowl.

dscn0478.jpgdscn0476.jpg

dscn0477.jpg

With the area marked on the underside of cowl, gives a 2:1 ratio, if no cut out on underside then it is 1:1 for outlet to inlet.

dscn0479.jpg

The area marked on lower side of cowl is for a dummy exhaust, this may reduce the efficiency of the baffles.

dscn0482.jpg

Options 1: Cooling baffles and no cut outs.

Options 1: Cooling baffles and exhaust cut out

Options 1: Cooling baffles, exhaust cut + an area on underside of cowl.

Any comments and suggestions chaps.

Kind Regards

SW

cymaz17/05/2020 17:45:28
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9254 forum posts
1196 photos

If it were me I would have a opening in the bottom..see if you can get the baffles tighter to the fins.

Jon might have an idea or two

Martin Harris17/05/2020 17:52:46
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9343 forum posts
252 photos

Chipmunk?

My 1/6 scale version is powered by an OS 52FS and uses the scale outlet area at the back of the cowling with a tight exhaust outlet, tiny scale fuel priming access port and small needle valve hole being the only possible exit holes in the cowling. It needs no baffling and has never overheated in the 17 years since I built it.

Chipmunk cockpit

Edited By Martin Harris on 17/05/2020 17:54:40

bert baker17/05/2020 22:01:04
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1609 forum posts
331 photos

Would it help it the propeller went clockwise

Martin Harris18/05/2020 00:00:29
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9343 forum posts
252 photos

Depends which way you look at it but flying backwards would do nothing for the cooling airflow! I suppose it would help scale fidelity though.

...or have I missed the point?

bert baker18/05/2020 00:58:42
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1609 forum posts
331 photos

On the full size the prop goes the other way round and the cooling air goes in onto the cowl on the port side

Often wondered with chippy and Moth models if it would be better air flow into the cowl from prop wash if the opening was on the wrong side

Jon - Laser Engines18/05/2020 09:07:12
5511 forum posts
268 photos

The cooling should be fine SW. That cowl lip will draw the air through nicely so i dont expect any problems.

Prop rotation? at our scale its a non issue. Full size sure, but we fly very much faster in real terms than full size and we are dissipating nowhere near as much heat.

Silver Wolf18/05/2020 13:55:32
174 forum posts
170 photos

Chaps thank you for the replies.

Martin, yes a chipmunk (D Bryant). Taken a few years to build started the project as part of Danny's scale class.

Jon, unless i hear otherwise will continue with Options 2: Cooling baffles and exhaust cut out.

No need to rush for reply plenty to be getting on with.

Kind regards

SW

David Davis21/05/2020 07:16:21
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3759 forum posts
718 photos

I am using an old but sound Laser 150 V in a WOT 4 XL. I have rigged up two sets of remote glow connector cables to each glow plug, one on each side of the fuselage. I power one glow plug with a glow stick and the other with a glow connector connected by cables to my flight box.

The engine always starts on one cylinder because the glow stick even after charging all night, is too weak to heat the glow plug. With the engine running on one cylinder I transfer the glow connector to the non-firing cylinder and after a few seconds, that cylinder chimes in as well.

One of my French colleagues, a retired aircraft technician has suggested that if I soldered together the cables which go to the glow plugs, I would not have to use the glow stick. In other words I could power both glow plugs from a single point.

Would this work? My flight panel has a variable resistor on it enabling me to vary the current going to the plugs.

On the other hand, I could always buy a better glow stick.

Chris Walby21/05/2020 07:52:41
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1246 forum posts
308 photos

Depends on the current/power rating of the flight box glow unit, if it can handle the current draw of two glow plugs at the same time then its possible to wire both glow plug connectors in parallel. Not too sure what happens to the current flow once the engine is running and if it would effect the other glow plug, but worth a try (as log as the flight box unit can handle the increased current.

The alternative is to run the glow plugs in series, but you would need to double the voltage of the flight box output which is possible, but you might find the running glow resistance drops which would then lower the current in the one you actually want to glow!

Details of your flight box controller and I an sure we can all assist?

PS - I don't have a flight box, but three glow sticks.....can normally get one to work !

Frank Skilbeck21/05/2020 07:54:50
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4734 forum posts
101 photos

Yes, but the problem maybe that it they are in parallel you will need to delivery >2 amps to light them both and the resistance the power panel would see is half that of a single plug, not sure if the power panel would be happy with that, and if one plug became open circuit then the other plug may then burn out. So a big single 1.5v cell powering both plugs maybe a better way than the power panel.

On my 200v I have wired the plugs up in series and power them from a 2v lead acid battery (accumulator?) seems to work well.

*Edit - Chris posted while I was writing"

Edited By Frank Skilbeck on 21/05/2020 07:56:04

David Davis21/05/2020 08:12:17
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3759 forum posts
718 photos

If it's any help the power panel is a JP Power Pro. Guess I'd be better off with a decent glow stick.

power-panel-jp-4444410.jpg

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