Laser Engines - Technical questions

[Joespeeder]

Hey Jon,

Besides the Storch project I'm flying some other Saito warbirds and other stuff so I need to replenish my field box(and clean it out, it's a mess right now) with Glow Plugs and some other stuff.

I normally just get OS F plugs since everything I have is a 4s but got wondering what you recommend so I went looking on the threads and did a search for Laser Instructions which gives me a PDF instruction sheet. It took a little while since there are threads here, on RCU, and of course the web site.

I found you recommending the OS F in a few posts and the PDF say's this

Most standard 2-stroke 'Hot' plugs work well. We use Super Tigre and Model
Technics F5-7 but experiment with your favourite type first. O.S. and Enya
4-stroke plugs work well. The Fox Miracle plug and some others do not work
with the Laser.

Can you talk a little about your thoughts on plugs? OS F's are easy.

I know nothing about the other plugs and as long as I'm refreshing the box should I try something like an OS 7 for the Storch since it'll be at mid to low throttle most of the time? I get the feeling Glow Plug discussions are like asking the race car guys about oil.... Endless chatter and I've never really tried other plugs to have any feel for reality vs fiction.

My limited search finds the OS F is a medium heat range plug. When I tried to compare that to others I started to see lots of arguments about which others were as hot or not.... Blah blah blah....

Enya #3 seemed to be well received.

Looks like the hot plugs may be suited for straight Methonal ?

Sorry, I feel like I'm opening a Pandoras box. Would a hotter plug help the idle ?

Thanks Jon

Joe

[Jon H]

As far as i am concerned there are only two glowplugs in the entire world. The OS No8 and the OS F.

i use the 8 in anything two stroke and the F in anything 4 stroke. If it wont run on either, i am not interested!

[Joespeeder]

Perfect !!

Thanks Jon. The PDF got me wondering. I’ve always used F’s.

Didn’t know what I might be missing.

Joe

[Denis Watkins]

Posted by Joespeeder on 19/07/2018 16:45:39:

Perfect !!

Thanks Jon. The PDF got me wondering. I’ve always used F’s.

Didn’t know what I might be missing.

Joe

Already agreed Joe, F plug in 4 stroke, OS No8 in 2 Stroke

Enya No3 lasts a good long time

But rule of thumb as plugs are getting very expensive, and you may see some offered at sale price

Hot plugs go in small 2 stroke glow motors, say up to .60

Cold plugs, .90 upwards, as larger lumps of aluminum retain the heat more easily

[Martin McIntosh]

Re plugs. OSf or the identical YSf for four strokes, Enya 3 or maybe OS 8 for most other things. These can all be found on ebay for a fraction of the normal cost and the ones I have are genuine.

[Joespeeder]

Thanks Guys,

I started to doubt myself and then down the rabbit hole of the interwebs I went.

Next thing you know I’m reading all these options and “experts” posts.

I’ll just keep doing what I’ve been doing with the OS F’s.

Cleaning up my flight box is going to take a lot longer than this did !

Joe

[Chris Walby]

Had a couple of flights yesterday before the howling gale, rain and lightning set in! Second flight in long steep dives it sounded like (after 3 seconds of say 6 seconds dive) that the engine revs were dropping off. It was okay on vertical climbs and everything I could throw at it. Landed and checked the WOT setting and set slightly richer but still the same.

Was it just the 27C air temp, strong cross wind playing tricks or something else?

Can't be much as it was stonking good fun in the air (indication of the wind was a near spot landing when my time was up!).

Cheers all.

[Jon H]

what throttle setting were you at in the dive?

[Chris Walby]

Full throttle from start to finish of the dive (about 45 degrees angle). The revs didn't drop off much and it recovered after shutting the throttle (but buy then it had slowed and was no longer in a dive).

It was a bit like running it on the rich side of optimum (just where the max revs drop off a bit, but does not affect general running).

Or its just me!

[Jon H]

its possible the clunks were high and dry at the back of the tank so the engines went lean as the fuel in the lines was used up. Difficult to know for sure but certainly a possibility

[Martin Harris - Moderator]

We were discussing this at the field today and that was my first thought too. However, it also occurred to me that there might be a possibility of it going rich (I wasn't at the field when Chris flew so didn't witness the problem).

The model uses your recommended forward facing tank vent so could it be that the extra speed in the dive would give an extra squeeze to the fuel, coupled with going richer* as the engine rpm increased? In addition, the fuel head would also be increased by the 45 degree down attitude...

Full throttle dives with an elderly Speed Air and Laser 70 ... young Chris is turning into a hooligan!

* I always thought engines leaned as the rpm increased but I have seen your assertions in other threads so must accept this on Lasers at least. I would like to understand why this should be as my assumption was that as airflow through the venturi increased, the more viscous fuel flowing through the small spraybar hole(s) would lag behind.

Edited By Martin Harris on 28/07/2018 23:07:08

[Jon H]

if it was rich then the engines would misfire as opposed to loose rpm. While the net result is the same in rpm terms, one is seen as a misfire and one is not.

The key for me in chris's post was that it was time and not speed that seemed to be the factor that caused the issue. If the clunk was just sipping air it would get bubbles in the fuel line which would take a little while to work through.

Without flying the model myself its always tricky to work this sort of thing out

[Martin Harris - Moderator]

He did describe it as "It was a bit like running it on the rich side of optimum (just where the max revs drop off a bit, but does not affect general running)." You certainly get a misfire with a rich transition but running at full throttle and richening the mixture while tuning does simply drop RPM unless done to excess.

Like you, I wasn't there to hear it but Chris knows his way round (larger) methanol burning engines so I can believe his description.

The temperature might be another factor but there shouldn't be any cooling problems in his installation. It will be interesting if he can reproduce the problem...

[John Tee]

Hi. I hope Jon or one of you other experts can help me. I have bought an old timey model ( enlarged Spook) complete with a Laser engine. I have been told it is a 90 size but there are no markings I can see without taking it out of the model. A previous owners initials are on the right hand mount - R A P, not the same as themodeller I bought it from.

It starts easily and runs well - approx 8000 rpm on a 16 * 6 master prop. but the front bearing housing gets hot after about 2 minutes running. I was told that the bearing had been changed. I'm not that up on four strokes so my question is is this normal.

John

[onetenor]

If the bearing gets hot that soon there is something not right. Either it's misaligned or tight in the housing. Maybe even dry for some reason. I would replace it again using the ones from Laser if you can get them. An afterthought is the shaft bent or the propdriver rubbing on the case nose? Jon might suggest more.

Nice motor though.

Edited By onetenor on 30/07/2018 22:18:51

[John Tee]

Onetenor. It doesn't feel stiff or tight and flicks over nicely. No noise that I can hear but hearing not my strong point - only one working ear courtesy of a strong hearing aid.Shaft I would say must be ok as no vibration. I have seen the model/motor fly many times at the Brean model holiday over the years and know it has not been crashed.

John

[Jon H]

Hi John

If the bearings feel smooth and there is no whining or graunching sound when the engine is running then the bearings are probably ok. As the front housing is connected directly to the crankcase it is not unexpected for it to heat up as much as the rest of the crankcase so do not be concerned if its too hot to hold on to.

If in doubt, remove the front housing complete with crankshaft by removing the 4 screws on the front of the engine. Be sure to use a sharp/new 3/32 allen key for this and clean any debris out of the bolt heads. Once off you can rotate the crank on its own and see if there is any feeling of roughness.

[John Tee]

Many thanks for the replies. I feel happier now, didn't think of heat being transferred from the crankcase. As I say the motor runs happy enough with no sign of distress and is very easy to start.

John

[Jon H]

In that case John just go with the flow. Other than the bearings there are no spare parts available for the engine anyway so try not to loose/break it. We discontinued the 90 in 1992 and your example is pre 1988 as that carb went in 88. Our current spares dont fit it so if anything is lost or damaged its done.

Once it finally bites the dust, our current 100 is a drop in replacement.

Edited By Jon - Laser Engines on 31/07/2018 14:17:23

[John Tee]

Hi Jon, I did wonder how old it was as I have never seen a silencer like that, but didn't realise it was more than 30 years old!!! Also I have to renew the remote glowplug (nothing to do with Laser) as it goes through two adaptors, 1* standard remote glowpug and then through a phono socket and then the glowplug - a recipe for bad connections. Looking forward to using it. If all else fails will make a good addition to my collection of older motors.

John

[onetenor]

I said Jon would know the right answer.

[onetenor]

I said Jon would know the right answer.

[Chris Walby]

Jon, Martin,

Again not ideal flying conditions up at the field yesterday and things will have to wait for someone else to have a go as the engine is now out of the Speed Air although I think I have come to a conclusion. The engine performance was faultless despite spins, loops, inverted 8's and dive tests...some but not all at WOT for extended periods.

Conclusion...Its me So thanks for you help.

I think two things are happening, firstly the engine starts to load up as the dive angle decreases and secondly its the Doppler effect as the poor old Speed Air airframe is whistling so I think its at its VNE Time for another project..

[Jon H]

Posted by Chris Walby on 01/08/2018 07:09:31:

its the Doppler effect as the poor old Speed Air airframe is whistling so I think its at its VNE

I am reminded of a poster i saw at a full size flying club once. It depicted an aircraft minus its wings with a traumatised looking pilot sat plunging toward earth. The caption read 'VNE is not a challenge'

How true!

John, you are not alone being shocked at the age of an engine. In general i tell my customers to add 8 years to however old they think their engine is.

A while ago I had a customer return an engine for service that was '4 or 5 years old'. When i got it i called him to let him know the service cost etc and to mention that he had misplaced 10 years as the engine was actually from about 1998!

I think the other thing is that most people assume that engines over about 10-12 years are getting well past it anything over 15 is long on the scrap heap. In most cases this is quite true, but with our engines they not only last a long time, but their owners also seem to have a tendency to flog the horse long after it died when it should be given a decent burial. Many also sit in loft's for long periods and are usually rusted up a treat and essentially useless.

As shocking as it may be, even a Laser engine will wear out and when it does, its time to throw it away.

In this instance grief counselling is available in the form of a 10% px on a new one. Assuming i have them

[Joespeeder]

Hey Guys,

I guess this is kinda technical. I needed a way to mark my fuel jugs to see at a quick glance my Laser fuel from the 30% CoolPower I use for Saitos. Both look identical.

I found these and they are very well built. I got 5 of them and I'm very happy with them.

LINKY to Cool Tags

Enjoy.

Joe

Front and Rear of the same tag.