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Laser Engines - Technical questions

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Percy Verance01/07/2018 08:15:06
7511 forum posts
144 photos

Hi Chris

Looks like JOn is still tucking into his bacon & eggs.  So, based on my experiences of the 1.50 - now out of production - I'd say go for the 155. It's a much newer design than was the old 1.50 (not that there was anything amiss with it!) but the 155 is both lighter and more powerful. I'm sure I noted somewhere it is Jon's first Laser design too.

The 180 is, I think, designed to cope with the larger sizes of warbird, and those scale bipes with shorter noses. It's intentionally a bit heavier specifically to fill that role. It's also intended to swing big (we're talking 20 inch) props at torquey revs, which isn't perhaps quite what you'd want for a Wots Wot.

See what Jon says when he arrives, but my guess is it'll be the 155 all the way. I have been wrong before though......


Edited By Percy Verance on 01/07/2018 08:19:18

Jon - Laser Engines01/07/2018 09:02:47
4412 forum posts
162 photos

Either engine will work well but the 180 will have the performance edge.

I flew a WWXL with one of our 155's and I was pleased/ impressed with the performance. It flew nicely and did not feel under powered with loops from level flight all easily done and reasonable vertical performance.

However, I did feel the need to use all the power it had on several occasions but this depends on flying style as I gave it more of a beating than its owner (Tim?? Where are you???) Anyway, the 180 would give a little more urge without being silly so could be an option. Percy is quite right when he says the 180 is a torque monster but that can be an advantage in an aerobatic model as you can use a big prop and get instant thrust out of it instead of having to 'spool up' a smaller engine. With correct propeller choice this added oomph may not translate into more speed and the only difference would be vertical performance.

The added weight of the 180 may also mean you don't have you use any lead in the front depending on how the WWXL balances.

SO to be honest, either would work fine and it depends on exactly what you are after. Also consider what type of model you will want you use the engine for once the WW bites the dust

Ron Gray01/07/2018 09:14:19
1299 forum posts
343 photos

I fly mine with a 160v and whilst it does have enough power to fly big aerobatics (F3A Clubman schedule no problem) it does need to be on full throttle for the vertical bits and does run out of steam. Having said that, the WWXL really excels (!) at slow manoeuvres and is a joy to behold just bumbling along at ¼ throttle.

I do have a 240v sitting waiting for a new airframe and the original intention was to swap the 160v for the 240v but as it involves quite a bit of work I’ve put it on the back burner but am still very tempted. So in my opinion I would go for the 180.

trebor14/07/2018 10:29:59
1840 forum posts
212 photos
Posted by Jon - Laser Engines on 15/12/2017 22:03:23:

Trebor, give Dave at motors and rotors a call. He might be able to help you with the ST carbs as he (and his father) were the distributor for many years. He may have more for you than that PDF shows. If all else fails I can supply new carbs for them as they are the later engine with the steel retaining clips but give the ST carbs a go first.

Jon, I seem to have a bent spraybar on one of the carbs and had no luck straightening it out. Don`t suppose you know the size of St carb for the laser 70 as I will give it a go trying to find one before replacing the carb. I have already sent Motors n Rotors a note.

Rocker14/07/2018 14:08:27
341 forum posts

I have Laser 180 in my Wot Wots XL fly it great ,in my opinion it is the perfect engine for the Wots Wot XL and sounds a lot better then a 30cc petrol engine

Rocker14/07/2018 14:16:55
341 forum posts

Now Laser have stop production of the 120 ,how close performance wise is the Laser 100 compare to the 120 .Saving my pennies to find a engine for a Seagull Spacewalker 120 .I am sure the Laser 100 should fly the Seagull Spacewalker OK ,just need to make sure .No hurry I see the the Laser 100 is out of stock so is the Seagull Spacewalker 120 (The Spacewalker 120 is due in about August not sure when the Laser 100 will be available no doubt Jon will let me know the answer to both these questions

Edited By Rocker on 14/07/2018 14:17:44

Percy Verance14/07/2018 16:09:41
7511 forum posts
144 photos

Worry not Rocker.

As the owner of two Laser 100's ( yes, I liked mine so much I bought another) I can honestly say a 100 would have no difficulty at all pulling a Seagull Spacewalker. My 100's are quite happy on a Graupner 15x8, and that's what I flew my 1/4 scale Cub on, all 14 pounds of it. The Spacewalker will be around 9 pounds. You do the maths.

The 1.20 is a shorter stroke than the 100, and is more of a revving/sporty type engine. That isn't what you need for sport scale models. You need lots of grunty torque, and the 100 has that in spades.......

Percy Verance14/07/2018 17:52:33
7511 forum posts
144 photos


I forgot to mention earlier that Black Horse also do a 1/4 scale Spacewalker. It's probably the same one.......

And Airtek Hobbies in Yorkshire are showing it's in stock......eee by gum, grab it quick lad......

Airtek provide good service Rocker. I just ordered a Multiplex Funray from them earlier this week.  yes

P.S. The specs for the Seagull Spacewalker show the flying weight as 11 pounds. A bit heavier than I imagined Rocker, but still well within the capabilities of a Laser 100.....

Edited By Percy Verance on 14/07/2018 18:04:52

Jon - Laser Engines14/07/2018 21:13:19
4412 forum posts
162 photos

Trebor, im not sure of the size. I was only 10 when laser stopped using them! Im sure M+R can help you.

Rocker, the 100 would be plenty. As Percy says the 100 is a long stroke motor with plenty of grunt. The spacewalker is not a high performance model, a 15x8 would be my choice of prop and im sure it would putter around quite happily.

Alan Hilton15/07/2018 14:31:33
58 forum posts

Hi Jon

My next build is a chilton dw1 GAESZ it would make producing an accurate cowl much easer if the front bearing housing and prop driver were anodised red .Would this be possible on a new 155 .Have you got piston rings for a 150


Joespeeder18/07/2018 05:56:49
40 forum posts
13 photos

Hey Jon,

Flew the Storch !! Flew great. But I’m having trouble keeping the right side cylinder lit. It seems to load up and I’m getting a good amount of oil from the rocker cover.

My current thought is my drain is too small and loading that cylinder with excess oil.

I’ll swap the drain. Would a drain that’s too long, too small, or both load the right cylinder with oil and cause it to go out?

I ran the drain down the long landing gear struts to try to keep the fuse cleaner. But I think the lines I used were too small for the distance.

It’s going to be awesome once I get the cylinder to stay lit. 20lb plane 40lbs thrust and I as seeing about 7500rpm on a 22x6 Xoar. Once I get things settled I’ll report the final tune numbers. With both cylinder lit the Storch felt great on the sticks.


Jon - Laser Engines18/07/2018 08:49:55
4412 forum posts
162 photos

Alan, sorry i missed your post. In theory i can get them done red but as we never anodise anything that colour it would have to be a special. If so, it wont be cheap.

Joe, good to hear the storch has flown. You will have to remind me which engine you have as i have forgotten! Usually cylinders dropping is due to the tuning being out, most likely the slow run. The breather should not cause any running issues and the rocker covers should be full of oil if the engine is inverted so that is normal too.

Edited By Jon - Laser Engines on 18/07/2018 08:50:16

Joespeeder18/07/2018 11:56:30
40 forum posts
13 photos

Hi Jon,

It’s the 300v running 10 & 10 with Klotz. Ok, I’ll keep tuning and replace my breather pipe. It’s the only thing I can see that’s out of the ordinary.

I used standard fuel tank tubing brass tube along the strut with new black Nitro fuel line since it looked good. The length of my drain is about 1 1/2 feet, maybe a little more. As I think about this, that black line is very thin and flexible compared to standard silicone line I’ll check for pinching.

The left side cylinder never dies and the right side it really wet around the back of the head and started to leak dark oil from the rocker cover. The engine is still breaking in. I looked to see if the carb was seated or I had some other issue. Everything seeems tight. I lost the cylinder in flight at about 1/2 throttle cruising and trimming the Storch.

I’ll keep tuning, the one cylinder gave me fits and I never trust myself.

Thanks Jon.


Jon - Laser Engines18/07/2018 12:21:19
4412 forum posts
162 photos

Hi Joe

The left cylinder (right when inverted and viewed from behind) lends to run slightly leaner on the slow run than its best mate. Its just to do with the firing order and its why we use two carbs.

Its likely that as you have installed the engine inverted its slightly richer than it was on my test bench which is why that cylinder is now protesting. Anything at or below half throttle is slow run needle territory so its likely that is where the trouble is.

also at idle you should be able to hear the cylinders individually if you listen carefully. I suspect that the good one is idling with a relatively constant tutt, tutt, tutt, note where as the one that stops is not running so smoothly. If it sounds more tutt, pff, phutt, tut and lacks the constant and obvious exhaust pulses of the good cylinder then it is likely too rich and the slow run should be leaned off.

Before that, make sure both main needles are set for maximum rpm by leaning them off in turn until the cylinders loose power. This is the only way to set them accurately. I have added a video at the bottom showing me testing a 300 and setting the tuning. Its not the best video but its all i have got at the moment. Listen very carefully at 2.20-2.25 and you can hear the right cylinder drop out slightly. It was still firing, but you can hear its missing quite a bit where as the other cylinder is still thrubing along nicely. After i lean it off you can hear from 2.35-2.39 its firing evenly on both pots. 

18 inches is very long for the breather. Its unlikely anything will escape from there but that said it shouldnt cause the engine any problem. I have run my engines with breathers blocked off before now and it makes no difference.


Edited By Jon - Laser Engines on 18/07/2018 12:22:36

Joespeeder18/07/2018 13:08:15
40 forum posts
13 photos

Thanks Jon,

I’ll revisit it in the next day or two. I hate having to ask questions you’ve gone over and over. Thanks for the video, I wasn’t sure about the breather.

I know an 1800rpm idle is really well tuned. I was shooting for 2,500-2,600 since I’m still breaking in. What do you target for a new 300v idle range?


Jon - Laser Engines18/07/2018 14:46:04
4412 forum posts
162 photos

1800-2000 is fine for idle. The performance of the engine will not change much during the run in. TO be honest, they give about 99% of their performance from the word go

Joespeeder18/07/2018 18:31:01
40 forum posts
13 photos

One last question, I'm running the flexible extensions. Would I do better with the mufflers? I would put them about 4inches away from the head by using the flex extensions and some silicone tubing as connectors.

Would the back pressure help my idle?


Jon - Laser Engines18/07/2018 21:03:11
4412 forum posts
162 photos

nah, the exhausts wont make much difference at idle. Also, the 300 will melt silicone in about 5 minutes so don't waste time with that!

Manish Chandrayan19/07/2018 04:02:03
531 forum posts
65 photos
Does that mean, that a 150 will also melt a silicone exhaust joiner or extension? Given that a 300 has two 150 pots.

Edited By Manish Chandrayan on 19/07/2018 04:03:18

Jon - Laser Engines19/07/2018 08:33:53
4412 forum posts
162 photos
Posted by Manish Chandrayan on 19/07/2018 04:02:03:
Does that mean, that a 150 will also melt a silicone exhaust joiner or extension? Given that a 300 has two 150 pots.

Edited By Manish Chandrayan on 19/07/2018 04:03:18

Any 4 stroke over about a 90 will make short work of silicone tube. Once you are above 120 its really getting into a per flight rate for consumption!

A friend and i both have Enya 155's and the exhaust on those is so hot it might as well be the depths of hell itself. They run so hot in fact castor oil wont even burn onto the exhaust as it just turns to ash! Brutal engine mind, its only let down by the old school air bleed carb so i updated mine to a laser carb and its much better

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