Laser Engines - Technical questions

[Jon H]

Posted by TartanMac on 19/04/2018 21:44:34:

Is there any difference in power between Aspen and petrol ?

I think normal petrol is about 100 revs faster but have not really tested it that much

[Chris Walby]

Seagull Dual Ace update, it passed its noise test today and the changes were:

• Exhaust deflectors pointed reward
• 12 x 8 props fitted
• Upper servo arm travel limited (this is menu driven and can't be adjusted in flight or accidently) currently shows about 2 mm of throttle barrel when in wide open position
• Standing in the middle of the flying field with just the model and the tester

Additional measures had the above not been sufficient

• Fill the airframe with water proofed cheap sponges
• Gone to 12 x 9 or 13 x 8 props
• Limited the throttle even more

I have a couple of other challenges to sort out, one being the wing bolts keep working loos/falling out! and then I'll be ready to go.

Thanks to everyone who contributed suggestions, some I have used and others I'll keep for the next time

[Jon H]

loose wing bolt is more than a challenge!

[Manish Chandrayan]

Jon
What happened to the 180 testing? Is it on? I mean engines out with individuals and being given good exercise?

[Manish Chandrayan]

Chris, is the wing bolt metal? If it is, replace that with a nylon one and that is likely to solve your issue. I would also suspect that there is some considerable vibration for the wing bolt to keep coming loose. This may also have been a factor in the noise problem you were encountering

[Jon H]

Posted by Manish Chandrayan on 20/04/2018 02:35:36:
Jon
What happened to the 180 testing? Is it on? I mean engines out with individuals and being given good exercise?

To my immense frustration those engines have not yet been built. I am at least 5 months behind where I should be due to a lack of parts from the factory.

I am not at all happy about it.

[Bob Cotsford]

Posted by Chris Walby on 19/04/2018 22:36:42:

Seagull Dual Ace update, it passed its noise test today and the changes were:

• Exhaust deflectors pointed reward
• 12 x 8 props fitted
• Upper servo arm travel limited (this is menu driven and can't be adjusted in flight or accidently) currently shows about 2 mm of throttle barrel when in wide open position
• Standing in the middle of the flying field with just the model and the tester

Additional measures had the above not been sufficient

• Fill the airframe with water proofed cheap sponges
• Gone to 12 x 9 or 13 x 8 props
• Limited the throttle even more

I have a couple of other challenges to sort out, one being the wing bolts keep working loos/falling out! and then I'll be ready to go.

Thanks to everyone who contributed suggestions, some I have used and others I'll keep for the next time

Well done Chris. Did the prop change get rid of the airframe resonance that you mentioned earlier?

[Chris Walby]

Bob,

The 12 x 8 props have loaded the engines more so its not running quite as fast (need to take some readings and confirm the difference) + angling the exhaust deflectors away made the biggest difference.

The highest reading was front on (I would have expected tail on, but what do I know!), having slept since I think the nacelles could the a contributing factor as they are quite flexible with a good airspace between them and the engine/tank box.

The Speed Air (70 Laser) engine has freed up nicely and where it used to just squeeze past the resonant frequency before hitting max RPM does so easily, so oddly would probably pass its noise test easier now than when we did it originally (that was just under the 82dB).

I am still not happy about my installation of the nacelles (fit) and might see if I can make up a set of thicker fibre glass versions with some sound deadening, but that's for another time.

The sun is shining and I should be out flying...

[Chris Walby]

After work.

**LINK**    If the link does not work let me know as it my first one!

This is after the mods to get it through the noise test, the last part is an attempt to show the throttle barrel position. I just take a photo of that.

It still needs a bit of fine tuning (which I do without the throttle trim in and then set it back in for the final test (interestingly its even closer in RPM when trimmed down than when they are wide open. but only by a couple hundred RPM.

Edited By Chris Walby on 20/04/2018 21:16:42

[Jon H]

Its always the front Chris. The stalled prop makes a great deal of noise, noise which is gone once the model is in the air which is why I mentioned that the front test should really be ignored.

[Gordon Whitehead 1]

Posted by Jon - Laser Engines on 19/04/2018 20:48:16:

I have been able to fit my 155 petrol prototype into my pulse 125 and intend to get it in the air soon. Testing it on the ground it was peaking at 8800 on a 16x8 using aspen fuel. I was surprised by that but I will take it

That sounds like a pretty good figure Jon. Are the idle and throttling as impressive? Have you maidened the Pulse yet? Inquiring minds need to know :}

Gordon

[Jon H]

Idle and throttle response were what you would expect from a Laser

I did test fly it and sadly ran into a great deal of trouble. First a pipe melted when it touched the exhaust closing the vent line to the tank and causing the engine to stop, then I had tuning problems which took me a while to suss out. It seems the engine was drawing air from the tank at certain attitudes and that was causing the strange behaviour. I will be fitting a larger tank and giving it another go asap.

In fairness the whole experience was a good one as its given me plenty of useful info for the instruction sheet and getting air into the fuel system is a sure fire way to upset any engine.

Once I worked out what was wrong and flew around it the engine was a monster and the pulse unlimited in the vertical.

[Gordon Whitehead 1]

It sounds as if a Laser 155 gas (155FG?) would be a winner Jon. Despite the fall-off in ARTF availability, there are still a lot of 20-30cc kits around that it would suit. I'm obviously biased, but having just sold all my bigger engines and the Jungie to downsize a bit to easier managed models, that capacity makes more sense to me than the 180 gas. And if club members would go for purring FS instead of howling DLE (I can dream), that would be a universal benefit.

Tygon is a bit stiff for use as a clunk line in small tanks. I seem to think that you don't like felt filter clunks, but one of those would stop air entering the system.

Gordon

[Jon H]

Can't use FG as saito use it already. I'm thinking GA for gasoline/alkylate but have not decided.

As for the 155 I was using a felt clunk but it was insufficient

[Gordon Whitehead 1]

We had a flier through the letterbox today from our local lawnmower agent to say they've started stocking both alkylate juices

Have you any video of the 155GA to show us Jon?

[Don Fry]

Jon, P would do. KISS applies. Don.

[Don Fry]

Or even G, if you have export ambitions to Trumpland.

[Manish Chandrayan]

Would it be right to assume that we will see a 155 Petrol available commercially before the 180?

[Jon H]

Given that petrol engines are usually sized by their cc not cui its likely to be GA25 and GA30 for the 180 version. I might go for GA25-CDi but cant decide if its a, naff, and b, too long. Assuming I'm happy with the testing the 155 and 180 should be available together.

Anyway I do have a small video to torment you all. I didn't record the cold start as I changed a few things and, frankly, it didn't occur to me. Once I thought about it I left it idling, found my camera, and the video then picks up the action. Sorry I'm looking at the non engine side, its just how it worked out.

In other news I have started building glow engines again. Our move is still on going but I have been able to start getting things together. I hope to have things available early in May assuming the rest of the move runs smoothly. Until then we are officially closed unfortunately, but as of Wednesday I should have a phone line at last so will actually be able to talk to people.

[cymaz]

LP25.....laser Petrol 25cc. Simples

[Gordon Whitehead 1]

Yup! Laser LP25 rolls off the tongue easily. As Lasers are uniquely British, there's nowt wrong with using "P for petrol" in the name.

Thanks for the video Jon. The 155 sounds very healthy and I've ring-fenced the dosh ready for my first Laser 25cc petrol when you achieve production.

Glad to note that glow production is restarting BTW.

[TartanMac]

Wow the engine sounds Brilliant throttle response is great. I like cymaz,s designation LP. Saito build for the American market and follow the American language (Gas). I would stick to something British sounding. LP sounds good kinda like the McLaren MC12. Whatever it's name will be its gonna go round the world as a great engine. I think Laser will be mentioned a lot more on the internet soon once they are in owners hands too.

[TartanMac]

Just wondering what size of prop was on it ?

[Jon H]

interesting comments on the name, the LP suggestion being similar to the L suggested by Mr Tidey. I'm leaning towards GA however as Zenoah are ZG, os are GF, Saito FG. Clearly G is the common theme, I assume for gasoline and in the case of Saito and OS, the F is for 'Four stroke'? Cant be sure, but it seems logical. Given that Laser is not as well known as perhaps we would like, naming the product in such a way that people know what it is just by its name could be handy. Google search results will also spit it out if the name is similar to the original search so keeping the G could be an advantage there.

Choosing a name is almost as complicated as getting the design right!

Anyway, I hope to have them ready soon but my recent experience with the 155 test flight (I was expecting a cake walk) has reminded me that nothing is certain and I have to test as much as I possibly can as each thing I test reveals aspects of the engine that even I had not considered. From the test I ran after I shot that video I think my other tank was causing the problems so I now have a section to write in the instructions about tank size and clunk setup as its going to be different from the norm.

In fact I think 'different from the norm' will be the phrase that best describes the whole engine, its design and its operation. No matter how much you think you know about operating engines you must read the instructions for this one. Its really simple, but the procedure is not the same as other similar engines. I'm tempted to send every customer who orders one a set of instructions and after 2 days give them a test. If they pass I send the engine, if they don't I send a dunce's hat and write a note to their parents

[Jon H]

Posted by TartanMac on 23/04/2018 22:36:41:

Just wondering what size of prop was on it ?

RAM 16x8. idle as low as 1500 (1600-2000 recommended idle range) and flat out at 8800.

Other props I have tested are APC 17x8 @ 7800 and a wooden (I forget the brand) 18x8 @ 7200.

On the bench at work I was only able to see 8600 from the 16x8. Fitting to a model saw a 200rpm uplift in performance. This is likely due to the blade being very close to the bench structure. I will be testing the 17x8 on the model once I am sure I have fixed the tank problems.

Edited By Jon - Laser Engines on 23/04/2018 22:45:52