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Laser Engines - Technical questions

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Doc Marten07/04/2020 13:04:37
539 forum posts
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Maybe some food for thought if another member finds themselves with a similar problem:

img_20200406_195558.jpg

img_20200406_195528.jpg

Edited By Doc Marten on 07/04/2020 13:06:21

David Davis09/04/2020 10:21:50
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3671 forum posts
688 photos

Two years ago I stalled my WOT 4 XL on landing and broke its back. I was going to throw it away until saw how much a replacement would cost. I repaired it and fitted my old Laser 150 V twin to it. There are some advantages to this lock down aren't there! smiley

There's still some work to be done but what size propeller would you recommend with this combination Jon?

Jon - Laser Engines09/04/2020 12:34:56
5413 forum posts
263 photos

16x8 i reckon. The 150v should do 8-8500 depending on the brand.

It should be a fun little combo

Tony Richardson27/04/2020 23:41:49
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636 forum posts
25 photos

Hi Jon, I have been waiting for your 180/30cc gas engine as I have been trying to move to gas engines over glow due to the availabiillity or lack of glow fuel in my location, this however is a question about your glow engines, ethanol is readily available here as is Klotz synthetic oil the problem is nitromethane, now will Laser engines run on fuel with no nitro? and if cleanliness is 100% how do you feel about home mixed fuel, I would be looking at a 120 to 180 size for an almost 1/4 scale SE5a, something that would swing an 18 - 20 prop, not looking for speed more pull and air flow..

This engine would be mounted upright if that makes a difference..

 

Tony..

Edited By Tony Richardson on 27/04/2020 23:43:48

Jon - Laser Engines28/04/2020 11:51:34
5413 forum posts
263 photos

Hi Tony

You dont need nitro for the engines to run fine so dont worry about that. However, they will only run on methanol when using a glowplug. We have had one chap use ethanol but he is also using spark ignition.

I would need to test it to be double sure, but im pretty confident ethanol will not work with a glowplug.

By all means try it though, you arent likely to break anything.

Keith England 128/04/2020 12:40:07
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15 forum posts
Posted by Jon - Laser Engines on 28/04/2020 11:51:34:

I would need to test it to be double sure, but im pretty confident ethanol will not work with a glowplug.

By all means try it though, you arent likely to break anything.

Jon, and Tony, an interesting experiment we did years ago in school was to heat a platinum wire red hot and hold it over a beaker of methanol. The platinum wire continued to glow even hotter as it catalysed the methanol vapour. That is what keeps the glow plug glowing in a glow engine. I don’t recall that this same reaction occurs with ethanol, but it just might do so. Tony could test this by healing a glow plug in the vapour from a small quantity of ethanol and seeing if it remains hot when power is removed - obviously be careful of it igniting

i know how Jon dislikes onboard glow systems but I would suggest you might need to use an onboard glow to replace that catalytic heating. I suspect it may well run fine then?

Don’t confuse methylated spirits or denatured alcohol as methanol. It is ethanol with a few percent of methanol as a toxic byproduct. I doubt it would be enough to keep a glow plug hot if ethanol doesn’t work.

Edited By Keith England 1 on 28/04/2020 12:45:21

Edited By Keith England 1 on 28/04/2020 12:46:13

David Davis28/04/2020 13:36:27
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3671 forum posts
688 photos

Got the old 150 V Twin going this morning in the WOT 4 XL. It runs well but it's a bit noisy.

first run up in years (9).jpg

Would a silencer from a modern Laser fit this engine?

Jon - Laser Engines28/04/2020 13:44:48
5413 forum posts
263 photos

Yea it was the lack of catalytic reaction with ethanol that is why im not convinced it will work. As you rightly point out though there are experiments that could be performed to test it, but truthfully i would just inject some into an engine and see if it fires at all. If so then mix up 100ml or something with 10% oil and see if the engine will run without the glow.

If not onboard glow might fix it but you would need to carry a heavy old battery as the current draw is really high. CDI would probably be a better option in this case as its current draw is probably 10% of a glowplug.

And yes, OBG systems are the work of the devil. 99% of the time they are a bandage on a broken leg and the amount of grief they cause is just not worth the bother. Especially when one could save themselves the trouble by correctly tuning the engine in the first place

The only exception i make to my OBG rule is single carb multi cylinder engines. They can sometimes need a helping hand as you cant tune each cylinder perfectly with only one carb. However, i would say that overall engine quality is a very important factor here as none of my 3 OS multi pot/single carb engines (1 twin and 2 4 cylinders) need OBG. My Saito 450 3 pot didnt either and since i upgraded its pistons to laser twin ring pistons neither does my ASP160 twin.

I have performed the same piston swap on my SC400 radial so it will be interesting to see if it is still a useless heap or will now run more reliably once i finish the rebuild.

Jon - Laser Engines28/04/2020 13:47:14
5413 forum posts
263 photos
Posted by David Davis on 28/04/2020 13:36:27:

Got the old 150 V Twin going this morning in the WOT 4 XL. It runs well but it's a bit noisy.

first run up in years (9).jpg

Would a silencer from a modern Laser fit this engine?

Thats a negative. We changed the stub in 2016 so a modern one will just get mangled. We did discuss the fact that it would kill off the older engines and the overall sentiment was 'we discontinued them 24 years ago, enough is enough'.

I can have a forage and see if i have some used ones kicking around? If not just fly it. It wont be that bad in the air

Frank Skilbeck28/04/2020 16:17:00
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4671 forum posts
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Posted by David Davis on 28/04/2020 13:36:27:

Got the old 150 V Twin going this morning in the WOT 4 XL. It runs well but it's a bit noisy.

But what a nice noise wink

Also you could try adding a bit of silicon piping on the silencer outlet which would lessen it slightly.

BTW I have half your 150v, a 75 single, it's not very noisy at all.

SR 7128/04/2020 18:25:24
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429 forum posts
138 photos

Whats the fuel consumption rate for the Laser 360, just want to know for the tank size, i have acres of room in my Bucker Jungmiester

Thanks Tony

Jon - Laser Engines28/04/2020 20:44:33
5413 forum posts
263 photos

i have 28oz capacity in my 360v powered sea fury. I takeoff, timer runs for 8 mins 30 and im back on the ground for 10 mins with probably just over 1/3 of my fuel left although i have not checked that in ages. Given the nature of the model i dont spare the horses so something more sedate will probably use a little less

my tanks are two slec 14oz jobs taped together into one block for easy installation.

Scott Edwards 228/04/2020 21:30:11
212 forum posts
97 photos

So far I've had no problems using a single tank with two separate clunks in my own 360V. I use a Kavan 1000cc (34 Oz) tank which is a bit overkill, but gives a big reserve. I notice a change in CG after about 12 minutes and land with plenty to spare. It's a 12Kg o/d pattern ship and isn't flown gently 🤪 The engine is an absolute beast, I love it !

Jon - Laser Engines29/04/2020 08:16:32
5413 forum posts
263 photos

Yep, 2 clunks in a single works fine but i like the two tanks as it keeps the tank length down and that can be handy. Also..32oz..i suppose i can always rely on you Scott to go totally overkill!

Where do you fly that thing anyway? The buzzard strip isnt that big.

The c/g thing is interesting though as i have never noticed a difference when flying any of my scale models. Its why i am always amused to see conversations about moving a c/g position by 5mm or adding 10g here or there to get the desired effect. Its just not that sensitive in most cases although a patternship is likely to show it more than a warbird.

The only time i actually noticed the change was when i had a problem right after takeoff and needed to land right away. I did notice the added weight when landing with full tanks as i have the ele/flap mix etc set to trim the model for landing and this was obviously set to trim the model when the tanks were low.

Scott Edwards 229/04/2020 16:03:09
212 forum posts
97 photos

I went for a thin NACA airfoil which allows it to fly very slowly at high alpha to plonk it down on our short strip. As the wing leading edge is swept, the tank is a long way from the CG compared to a Warbird, so after burning half a Kilo of fuel you can definitely notice the difference, it's not a problem though.

AUW dry is 24lbs and with the 360V it will disappear vertically before you can say "HOLY F***". Pic below is before it was finished, fence is 6ft, the cowl and spinner are from a 1/5 Spitfire. It eats sky like you wouldn't believe, for the first few flights it frankly terrified the hell out of me !

imag1742_1.jpg

Chris Walby29/04/2020 16:14:07
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1193 forum posts
297 photos

Wow Scott that is just something else, just got to ask...how do you transport it?

Jon - Laser Engines29/04/2020 21:00:46
5413 forum posts
263 photos

thats awesome! i want a go :D

Tony Richardson01/05/2020 02:01:33
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636 forum posts
25 photos

Ok further to my previous question, Ethanol is out but where does Methyl Hydrate fall in this equation, it is also readily available here??

SR 7101/05/2020 02:36:19
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429 forum posts
138 photos

Love that Scott, must be 9 ft long

cymaz01/05/2020 06:20:26
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9182 forum posts
1181 photos

If that’s a 6’ fence, it’s got to be 10’+

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