Laser Engines - Technical questions

[Jon H]

6 minutes ago, Paul De Tourtoulon said:

what do you think Jon

 

I think the engine has run successfully for over 30 years with no oil hole, so there is no reason to think it needs any modification. if it aint broke and all that 🙂 

 

As for the piston, its for weight saving. early pistons were solid but they changed it before i was even born. 

[Paul De Tourtoulon]

Thanks, no head gasket either, and small markings on it, some obviously official Laser markings, others doubtful. So probably opened up or are they also  'Laser' markings ?.

[Martin Harris - Moderator]

Odd looking carb elbow and unless it’s very old, shouldn’t the inlet valve be larger?

 

I wonder if this is a genuine Laser - I believe there were some unauthorised copies on the market at one time. 
 

Jon will know…

[Artto Ilmanen]

On 29/04/2023 at 12:01, Jon - Laser Engines said:

I will check the number on the bottle when i get back to work on tuesday. Right now, im off flying

 

Hi Jon,

 

If back at work - could you kindly check this, please?

 

 

[Jon H]

sorry i forgot, post Bank holiday madness 

 

The number is 638, available on amazon

 

https://www.amazon.co.uk/Loctite-Strength-Retaining-Compound-Adhesive/dp/B00NY203C6/ref=asc_df_B00NY203C6/?tag=googshopuk-21&linkCode=df0&hvadid=310744208542&hvpos=&hvnetw=g&hvrand=15084034057458431361&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9045629&hvtargid=pla-585923539119&psc=1

Edited May 4, 2023 by Jon - Laser Engines

[Jon H]

41 minutes ago, Paul De Tourtoulon said:

others doubtful

 

yea most of those look like modeller mods. That donk on the top of the liner will leak like crazy so you might want to try and lap it out. 

[Mike Mc]

What's the recommended oil content for those older early 90's engines?

 

[Jon H]

anything after 92 will be fine on 7%. older than that 15%

[Paul De Tourtoulon]

"Finished",,,,

 

9.000 rpm on 10% nitro and an APC 14 x 6 prop,,,,😇

[Jon H]

On a 90? Seems slow. I expect that from an 80 and a 100 does those revs on a 14x7. Both on 5%. Might be a bit rich or the ring is on its last legs

[Paul De Tourtoulon]

The piston ring was a bit tired but for what I am doing with it at the moment it doesn't really matter, I see that the .62, .75 and the .90 all had the same bore, maybe someone has a new ring in a drawer somewhere, or I could beg for one,,,

[David Davis 2]

14 minutes ago, Paul De Tourtoulon said:

The piston ring was a bit tired but for what I am doing with it at the moment it doesn't really matter, I see that the .62, .75 and the .90 all had the same bore, maybe someone has a new ring in a drawer somewhere, or I could beg for one,,,

 

Gavin Carter over on eBay will sell you one. https://www.ebay.co.uk/str/gcpistonrings

[Paul De Tourtoulon]

Thanks, David, I have had half a dozen from him, the problem is Brexit, my last ring was 12€ delivered with taxes 27€ !

 For a club members OS 120,,,,

Edited May 5, 2023 by Paul De Tourtoulon

[Artto Ilmanen]

20 hours ago, Jon - Laser Engines said:

sorry i forgot, post Bank holiday madness 

 

The number is 638, available on amazon

 

https://www.amazon.co.uk/Loctite-Strength-Retaining-Compound-Adhesive/dp/B00NY203C6/ref=asc_df_B00NY203C6/?tag=googshopuk-21&linkCode=df0&hvadid=310744208542&hvpos=&hvnetw=g&hvrand=15084034057458431361&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9045629&hvtargid=pla-585923539119&psc=1

 

Thanks, Jon

[Jon H]

1 hour ago, Paul De Tourtoulon said:

the problem is Brexit

 

dont i know it. 

[Artto Ilmanen]

On 28/04/2023 at 19:39, Artto Ilmanen said:

Ok, thanks for Jon's kind help I was able to dismantle my both 150s for bearing change. I first tried to remove the prop driver with a 2-claw puller: the result was tears in the eyes as the only thing I was able to achieve was to get some (yet small, fortunately) marks on the prop driver -> so next attempt was to press the crank with a quality press which did the job without any further hassle. I also pressed the pinion drives out with a press. Then I applied some heat to get the pinion drive bearings out - this helped and the bearings came out very easily with just a tine help of a screwdriver and a very slight knock. 

 

Now the next phase will be to remove both front and rear bearings of the front housing. Jon must have some black magic trick to do the job easily but I plan to test to heat the front housing at 200°C and I hope this will help removing the bearings as aluminium is expected to expand more than the steel bearings.

 

Let's see how things proceed.

 

As I side note, on one of the crankcases there are fairly symmetrical marks (not quite, though) around the pinion drive bearing pocket? I wonder if they are a result of earlier bearing change or alternatively they could be some minor marks that came during the casting process?

 

 

@Jon - Laser Engines I believe you said the other day Loctite 638 is the recommended adhesive to secure the pinion drive bearing? (small amount of it is recommended on the bearing pocket)  You also said one could use Loctite 595 for the same job? The latter is more attractive as any future bearing change will be much easier with it as the Loctite 638 is a strong adhesive.

 

So could I skip the Loctite 638 and go for the 595 or did I miss something?

 

Ok, it turned out my home tools did not seem to be up to the task to press & glue the pinion drive bearing in the crank case. So I went to a small machine shop where I got the bearing and pinion drive pressed in - and the adhesive used to hold the bearing in the bearing pocket is Loctite 638.  First the bearing and then the pinion drive. No heating / freezing was applied.

 

Anyways, neither of the parts (bearing or pinion drive) required much force to press them in place. For the peace of mind I measured the pinion drive flange to see if the pinon drive axle was straight.  Both of the engines shew about 0,06mm play when measured. Now as the bearing itself has some play I hope this is ok. At least no excessive force was used. 

 

 

 

[Paul De Tourtoulon]

Finished ( at the moment) fiddling with my Laser .90, it seems to like running over 10.000rpm, I got between 10.200rpm and 10.400rpm in different configurations🤐 on a Graupner Sonic pro 13 x 7, good enough for me, I can see why Jon uses less oil in the Lasers, it chucks it all out and oiled our club table, unlike my Saito 100 that I also had with me, it burnt most of the oil up.

[Jon H]

7 minutes ago, Paul De Tourtoulon said:

Finished ( at the moment) fiddling with my Laser .90, it seems to like running over 10.000rpm, I got between 10.200rpm and 10.400rpm in different configurations🤐 on a Graupner Sonic pro 13 x 7, good enough for me, I can see why Jon uses less oil in the Lasers, it chucks it all out and oiled our club table, unlike my Saito 100 that I also had with me, it burnt most of the oil up.

 

the 90 gives its best around 7500-9000rpm. there is no advantage to running it faster. For oil, the 90 needs 15% and will not tolerate the lower oil fuel as it used different materials and processes in its manufacture. if large amounts of oil are coming from the breather this too suggests the ring is not happy. 

[Paul De Tourtoulon]

Yes the ring is worn out I saw this when putting it together, it didn't like the 15 x 8 airscrew, 7.300rpm or the Graupner ( old grey one )13.5 x 8 at 8.750rpm, I did try a few others, but it wasn't very happy on them, all it did was shake the club table like an Earthquake.

It's running on a mix of two different fuels, one a French one that is so dammed oily that all the club members are complaining about, the other ( 50% mix )  of that British blue stuff that you hate.

 

I won't bother looking for a new ring, too expensive and not worth the bother, there is plenty enough power for what I want to do with it, now where will it go ?.

[Paul De Tourtoulon]

I flew my trusty old Hurricane this afternoon with my old OS .90fs that I bought second hand in 1991, there was no compression when I got to the model field and as I didn't have any feeler gauges with me, I used a folded piece of paper from my last credit card payment, and it ran up 10.400 rpm on the Graupner 13 x 7 prop which is 1.000 more rpm than the laser, so what next, buy an overpriced piston ring or flog it.

[Don Fry]

10 minutes ago, Paul De Tourtoulon said:

I flew my trusty old Hurricane this afternoon with my old OS .90fs that I bought second hand in 1991, there was no compression when I got to the model field and as I didn't have any feeler gauges with me, I used a folded piece of paper from my last credit card payment, and it ran up 10.400 rpm on the Graupner 13 x 7 prop which is 1.000 more rpm than the laser, so what next, buy an overpriced piston ring or flog it.

A bit of patience, a friend is coming over in about 5 weeks. Will that suit?

[Paul De Tourtoulon]

11 minutes ago, Don Fry said:

A bit of patience, a friend is coming over in about 5 weeks. Will that suit?

You mean order a piston ring from Jon ?.

 

 

Well, Jon, have you one ?.

Edited May 7, 2023 by Paul De Tourtoulon

[Don Fry]

I don’t think Jon has rings for a 90, perhaps that bloke on e bay. 

[Paul De Tourtoulon]

36 minutes ago, Paul De Tourtoulon said:

I flew my trusty old Hurricane this afternoon with my old OS .90fs that I bought second hand in 1991, there was no compression when I got to the model field and as I didn't have any feeler gauges with me, I used a folded piece of paper from my last credit card payment, and it ran up 10.400 rpm on the Graupner 13 x 7 prop which is 1.000 more rpm than the laser, so what next, buy an overpriced piston ring or flog it.

I made a mistake, it was giving me 10.200rpm on the 13 x 7 with an OS  7 mm carb and 10.400 on a ST 7.5 mm carb.

 

 Thanks, But I made a mistake, as you can see.

 

Yes Gavin, I have had a few from him, they are better than the originals,,,

[Jon H]

Sounds like you might need to buy some bigger props. 13x7 is too small for a 90 of any brand. I would use 14x7 as a minimum and prop them for about 8500 max.