Laser Engines - Technical questions

[Chris Walby]

3 hours ago, Mike Mc said:

Laser 70 Prop

 

I finally got my new Laser 70 flying on a 10cc size Ultra Stick. It has more power than I expected, perfect for sport flying. I am running an APC 13x6, the flight performance is excellent, but it turns 10,100+ peak, fly at about 9,900. Is that too much RPM? Should I get a 13x7?

 

.

 

You can if you want, but Laser engines quote 

RECOMMENDED PROPS	12×7-8 13×6-7 14×4-5

 

So IMO 13x6 will be ok and it sounds like the engine is matched nicely to the model...no point just tootling around at 1/4 throttle trying to get it to die on you. Warm it up and then give it a right good thrashing...if its not fast enough pop a 13x7 on it and report back... just check the Ugly Stick manual for WOT power dives is ok! 

 

[Chris Walby]

Now just saying hypothetically a friend of my, well actually his mate has a an Acrowot XL that needs an engine.

 

So what would be the best one to fit in the nice uncut cowl?

[Ron Gray]

160FT

[Jon H]

8 hours ago, Mike Mc said:

Laser 70 Prop

 

I finally got my new Laser 70 flying on a 10cc size Ultra Stick. It has more power than I expected, perfect for sport flying. I am running an APC 13x6, the flight performance is excellent, but it turns 10,100+ peak, fly at about 9,900. Is that too much RPM? Should I get a 13x7?

 

.

 

 

You can run it at peak tune all day long so 10100 is not going to harm the engine. If you want to drop the revs a bit for noise then a 12x7 will do just fine. 

[Jon H]

2 hours ago, Ron Gray said:

160FT

 

Or a 200 even, the AWXL would handle the 200 with ease and i think the cowl should be mostly uncut

[Frank Skilbeck]

I've got an old 75, original supertigre carb, in a model, running on 5% synthetic (Southern Model Crafts). It starts really easily will tickover forever but on a 13 x 6 it peaks out at 7,600 rpm, it's not sensitive to the needle and that can be turned 180 deg either way with just a couple of hundred rpm drop , it has good compression and bearings are fine, I know from 20 years ago when my 61 would run a 13 x 6 at over 9,000 rpm (on straight). Valve clearances are OK, anything else to check, could the valve timing being out cause this.

[J D 8]

             If the timing were out doubt very much it would tick over or run, pick up very well.

[Don Fry]

I also run one of these. Mine is also one of the first production batches, I am the third owner, purchased as a non runner from the second owner who put new bearings in, and didn’t realise timing is important. It didn’t run. Cheap as chips.
mine has been in fairly constant use for most of the last 25 years. Easy starter, reliable tickover, good transition. Bit of a favorit. But powerhouse it ain’t. It’s way down on power from on either of my 80’s. 
It is what it is.

[Andy Stephenson]

Don,

Does your 75 have the dual ringed piston. Mine was new in 1986 and run regularly until it started to lose compression on starting. I sent it back to Neil who fitted the dual ringed piston which improved the performance but I didn't check by how much.

[Jon H]

On a 13x6 you should see 10k on a 75. If the carb is that vague it could be a cam, or it could be the carb jet is in the wrong spot...maybe a really gummy exhaust full of castor? that will kill performance. To check just take the exhaust off and see if it will go any faster. 

[Frank Skilbeck]

Thanks, I have several exhausts from the 3 61s I seemed to have acquired, I'll swap one over and see next time I'm down the field.

[Don Fry]

2 hours ago, Andy Stephenson said:

Don,

Does your 75 have the dual ringed piston. Mine was new in 1986 and run regularly until it started to lose compression on starting. I sent it back to Neil who fitted the dual ringed piston which improved the performance but I didn't check by how much.

Sorry, I bought it 25 years ago. It was a non runner, £20?. I knew the first owner was a Forman toolmaker at the undercarriage people over Gloucestershire way, my seller was a bit short of headspace. I adjusted the timing a couple of notches. Never touched it since. Looking inside engines is not my thing.

[Ron Gray]

You are aware that Laser make their own adapters, each one having 2 different internal thread dia to suit different spinners?

 

 

Edited April 9, 2023 by Ron Gray

[Moth Flyer 1]

I wasn't aware of that, Ron.

 

Thanks for the heads up on the matter. An ingenious answer to the issue. I always wondered what the centre thread in the Laser nut was for. My lack of attention.

 

To protect Jon's place in the market place, may be our Moderator could delete my post on the nut issue? My bad I'm afraid. Naughty step for me....

 

Humble apologies.

 

Mike

[Jon H]

6 minutes ago, Moth Flyer 1 said:

My lack of attention.

 

These were my idea and i thought the double ended thread was common sense really. As for a lack of attention, in fairness we dont actually advertise them. Probably because i have been waiting nearly 3 years for an official price to list them at, and because it means i have to take the photo, edit it, do battle with the broken website, copy html code as the online editor is busted...

 

The problem with all my bright ideas is the work they generate and the support they rely on. Alas, the latter is lacking and the former all falls to me. Like i dont have enough to do. 

 

Anyway, if you need one they are available in M8 and 10 o/d threads. 5 quid plus post until someone tells me different. 

 

 

 

The proble

[Artto Ilmanen]

4 minutes ago, Jon - Laser Engines said:

 

These were my idea and i thought the double ended thread was common sense really. As for a lack of attention, in fairness we dont actually advertise them. Probably because i have been waiting nearly 3 years for an official price to list them at, and because it means i have to take the photo, edit it, do battle with the broken website, copy html code as the online editor is busted...

 

The problem with all my bright ideas is the work they generate and the support they rely on. Alas, the latter is lacking and the former all falls to me. Like i dont have enough to do. 

 

Anyway, if you need one they are available in M8 and 10 o/d threads. 5 quid plus post until someone tells me different. 

 

 

 

The proble

 

This adapter is an excellent product

 

But how do you tighten it? As no socket head?

[Ron Gray]

Tighten with your fingers then a locknut tightened against the prop nut, works a treat.

[Artto Ilmanen]

2 minutes ago, Ron Gray said:

Tighten with your fingers then a locknut tightened against the prop nut, works a treat.

 

Ok, I see. Thanks, Ron!

[Don Fry]

What is the frontal width of a 200 V. That’s the distance between the outer edges of the cooling fins of the cylinders.

[John Stainforth]

3 hours ago, Don Fry said:

What is the frontal width of a 200 V. That’s the distance between the outer edges of the cooling fins of the cylinders.

I've just grabbed a ruler and measured it. Looks like almost exactly 160 mm. That's the absolute maximum width between the outer extremities of the cooling fins.

[Artto Ilmanen]

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 - tjios helped and teh 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?

 

 

[Artto Ilmanen]

..edit to my earlier post:

 

I came accross some information claiming the Loctite 595 does not withstand oils or fuels? I wonder if this is false information?

 

 

Or is there 2 different products with similar names?

 

Anyways,  I assume any adhesive silicone  withstanding oil and fuel should do the job?

 

Edited April 28, 2023 by Artto Ilmanen

[Chris Walby]

Artto, I think you are over thinking this. Clean and dry matting surface with a little silicone sealer will be more than sufficient IMHO

• These are close fitting machined surfaces
• They are not under any significant pressure 
• They are staggered and not just a flange so less likely to leak anyway
•  At worst the oil will leak out so I doubt anything will get in!

 

[Martin Harris - Moderator]

Has a previous owner suffered from a loose bearing?  It looks like someone has attempted to stake the bearing with a centre punch and I rather doubt that was done at the factory!

[Artto Ilmanen]

35 minutes ago, Chris Walby said:

Artto, I think you are over thinking this. Clean and dry matting surface with a little silicone sealer will be more than sufficient IMHO

• These are close fitting machined surfaces
• They are not under any significant pressure 
• They are staggered and not just a flange so less likely to leak anyway
•  At worst the oil will leak out so I doubt anything will get in!

 

Chris, 

 

You may be right. However, I’m not concerned about some leaks from the joints between the crankcase and the front housing or the back plate. My question is related to securing the pinion drive bearing to help with holding the bearing in its place. But also, using adhesive that permits any future bearing change. 

 

 

Edited April 28, 2023 by Artto Ilmanen