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Laser Engines - Technical questions

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Percy Verance08/04/2018 17:41:28
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6263 forum posts
110 photos

That's odd Martin. I bought mine new in 2006, and it definately has a radial mount. I can't recollect speccing it, and I'm assuming they were all like that......

Martin Harris08/04/2018 18:17:48
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7436 forum posts
186 photos

When I was looking to buy my 200v it was listed as an optional extra but when I bought it, the website had changed and it came as part of the package at a slightly higher price. Perhaps Jon changed back to a similar practice from when you bought yours?

Bob Cotsford08/04/2018 18:24:18
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7079 forum posts
404 photos

My ex-160V had radial mounting lugs as part of the crankcase, but you could get an accessory 30mm deep radial mount giving a larger PCD and more mounting area. Take a look at the photo at the top of the previous page and you can see the mount bolted on the rear of the crankcase.

Chris Walby16/04/2018 20:32:58
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405 forum posts
65 photos

With regard to running twin engines what's the typical (acceptable) difference between engines at various RPM's?

I am not obsessed at this stage, but just noticed today that at some RPM one was faster by 500 and then slower by 500 further up the RPM range (didn't hold it flat out as still taking it gentle at this stage).

It might get a bit closer once I have tweaked the bottom tick over throttle settings later on.

PS...they do sound nice wink

Jon - Laser Engines16/04/2018 20:43:50
3585 forum posts
144 photos

+/- 100 is fine. 500 is excessive though and could be down to linkage geometry or tuning. I would suggest you ignore the slow run needles for now, set the main needles for max rpm and then see how the top 2/3 of the throttle range are as this is where you will be most of the time when flying.

When I tested the engines they were near as makes no difference identical at idle, full and half throttle so double check those linkages and adjust if you need to

I forgot to mention, when tuning a twin for full throttle I recommend you set up each engine on its own, then start both and get up to full power. Run full power for AT LEAST 20 seconds and see if the slow engine can be leaned out further. Invariably the engines will need a slightly leaner mix when hot so make sure you get the engines up to full operating temperature before you finalise the tuning.

Edited By Jon - Laser Engines on 16/04/2018 20:48:00

Chris Walby16/04/2018 21:15:59
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405 forum posts
65 photos

Cheers Jon,

I have gone wrong in a number of places having seen your advice blush and will thus have another go doing it the right way. Its just a case of taking some time and working through anything I have done during the build.

I have a more immediate issue, but its not Laser related!

Jon - Laser Engines16/04/2018 22:14:18
3585 forum posts
144 photos

Its ok Chris. Its kind of a standing joke in some respects as the instructions (and i on the phone) clearly state that the engines should not be run rich and should be tuned for maximum performance straight out of the gate. As a general rule, everyone ignores me and goes into new engine auto pilot and runs them 'a bit rich' etc.

I'm not having a go at anyone, far from it, I just wish I knew how to convince everyone that you really can go for it from the get go and don't have to stroke and cuddle the engine.

My assumption is that it comes out of concern regarding damage of a new engine. We have all heard the horror stories with melted conrods etc and I suspect that is what causes the most concern. but if you use the fuel we recommend, with the prop and plug we recommend, and run it in as the instructions state and you have a problem I guarantee you I will sort it out.

I have only once refused to warranty an engine. it was 3 weeks old, the user mixed his own fuel and I refused due to the unbelievable state it came back in with dirt, grit, glue and sawdust all over it as well as down the carbs. Add the fact that it had no oil at all inside it at all, and it was the 2nd engine this chap has killed that week. I gave him the benefit of the doubt on the first, but two? in a week? I don't think so. I have all the photos somewhere if anyone is interested.

In the case of your engines specifically when I test ran them I leaned them off for maximum performance and saw 11000rpm from both of them on a 12x6 prop. This is the same procedure as every other engine I have assembled in my time at laser. Get them warm, tune them up and just go for it. You wont break them I can assure you.

Edited By Jon - Laser Engines on 16/04/2018 22:15:09

Gordon Whitehead 116/04/2018 22:55:38
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191 forum posts
109 photos

Regarding matching rpm on twins, years ago when I flew a couple of small OS .15-size twins a lot, I'd tune both engines for max rpm, chuck the plane up, and the airflow through the props then made them run at just about the same revs at full chat. Revs would be in the 12k range. Dunno if 4-strokes would be so accommodating though.

Gordon

Jon - Laser Engines17/04/2018 07:56:27
3585 forum posts
144 photos
Posted by Gordon Whitehead 1 on 16/04/2018 22:55:38:

Regarding matching rpm on twins, years ago when I flew a couple of small OS .15-size twins a lot, I'd tune both engines for max rpm, chuck the plane up, and the airflow through the props then made them run at just about the same revs at full chat. Revs would be in the 12k range. Dunno if 4-strokes would be so accommodating though.

Gordon

Yup. I had a model with two 25fp's in it and one was much slower on the ground. After a circuit or two it had come on song!

The opposite can also be true though as i set both the 70's in my pulse for the same rpm on the ground but the left engine was not happy in the air. A quick lean off and it was spot on after that. A friend had a similar experience with an enya 46 fs powered twin. It all came down to the long run up and making sure both engines were well up to operating temperature.

Alan Hilton17/04/2018 08:16:33
46 forum posts

Hi Jon

I am mounting a new 180 in a 1/4 scale extra 300 to run the engine in .I am thinking an 18-8 prop is that OK.How is the move progressing ? I may be interested in a 360 at some point if I can get back onto my flare stearman build

Alan

Scott Edwards 217/04/2018 14:36:16
152 forum posts
90 photos

I ran my 180 in last year on an 18x8 Master Aircrew Classic, and am still using the same prop in a big Spit. The 180 is such a beautiful engine, an absolute joy to install and operate. It took a couple of hours flying (largely flat out) for it to really come on song.


bert baker17/04/2018 15:51:59
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1087 forum posts
228 photos

I am getting just over 12000.rpm on a Menz 18/8 wooden prop with my petrol conversion,,,

Although I have had some fun doing it so far I think I shall wait for the production version to be avalible,,,

I was warned it wasn't easy to get one running as reliable as you would expect from a manufacturer..

The issue is getting a good pump signal,,and summer is now here

Getting a spark in the right place is easy to do,,,the carburation isn't that easy,,,unles you know the exact carb needed

Alan Hilton17/04/2018 18:29:41
46 forum posts

Thanks chaps

Alan

RC Plane Flyer17/04/2018 19:17:17
418 forum posts
15 photos

Appreciate not a Laser Engine link but in January I said I would be trying Laser 5% fuel from my Formula Irvine 5%

What a great move it has been. Easy start, great tick over and did not need to adjust top end

Edited By RC Plane Flyer on 17/04/2018 19:17:42

Manish Chandrayan17/04/2018 19:27:03
368 forum posts
56 photos
12000 with 18x8 on petrol power? You are on to a winning formula for sure, care to share with us that secret?

Edited By Manish Chandrayan on 17/04/2018 19:27:38

Edited By Manish Chandrayan on 17/04/2018 19:27:57

bert baker17/04/2018 19:40:56
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1087 forum posts
228 photos

img_2344.jpg

Scott Edwards 217/04/2018 19:48:38
152 forum posts
90 photos
12,690 RPM from a Laser on an 18inch prop 😂 Are you sure you haven't got the tacho set to 3 Blade?
bert baker17/04/2018 19:50:35
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1087 forum posts
228 photos

This was slowest I could get it without cutting out,,, the throttling up is to be desired img_2348.jpg

bert baker17/04/2018 19:51:48
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1087 forum posts
228 photos
Posted by Scott Edwards 2 on 17/04/2018 19:48:38:
12,690 RPM from a Laser on an 18inch prop 😂 Are you sure you haven't got the tacho set to 3 Blade?

Nope the meter clearly shows two blade setting,,

bert baker17/04/2018 20:46:38
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1087 forum posts
228 photos

Maybe wishful thinking ,,, it might have been a sun spot

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