Laser Engines development.

[Paul De Tourtoulon]

Ground running is one thing, I think the unloaded prop in the air is more important, My Dle 20ra and canister with an 16 x 8 does

8.800 rpm on the ground but 11.800 in the air,,

 

 

Edited February 14, 2022 by Paul De Tourtoulon
forgot video

[Jon H]

That video is just a blank screen?

 

Anywho all propeller benchmarking is done on the ground as the speed of the model in flight will impact the rpm of the engine. If you do a full throttle dive revs will rise significantly and the final rpm you reach is driven mostly by the airspeed reached. Its the old equal and opposite forces thing. An engine has an fixed power output and a fixed load, rpm is a result of the two. Reduce the load with high speed and rpm will rise as the increase in the airspeed of the relative airflow results in a decrease in blade AoA. This reduces drag load on the blade while power is constant. The above is an over simplification as engine power may rise with rpm but the point is, you cant use flight rpm as a reference as it is too dependant on model speed. 

 

Its also pointless trying to measure propeller performance only by rpm as they are not comparable due to blade area, profile and efficiency causing differences in thrust produced. As its thrust that gives us a feeling of power rather than actual HP or KW power the propeller itself is the defining factor when it comes to aircraft performance. Master airscrew props rev well and on a calculator will give high engine power (torque x RPM) but have low efficiency resulting in low performance. Similarly an electric motor will use plenty of power (watts) due to high current draw caused by the inefficient prop having high drag. This would also be true for an over propped electric motor. The watt meter says more watts, so that means more power? Watt meters only show power used and not power (thrust) out. Master airscrew props also tend to be noisy and this relates to their inefficiency. Noise is energy, energy taken from your engine and not used to make the model go faster. A loud prop might sound like it is giving loads of power (thurst, whatever) but the model performance may well be lower. Biela props are very quiet but have excellent performance as they convert more of the power put into them into thrust instead of noise. 

 

All you can do is use a known propeller as a fixed load to compare engine output and that is all the numbers mean. For example i can compare the 200 inline, flat and v to eachother using a known load and they all perform the same. If the 200 flat was slower for example, it might point to a timing error or some other issue. I can also compare my 200 to a saito 200 or another other engine using the same fixed load prop as a reference. Saito might quote a higher HP on their website, but on the same prop if the engines rev the same they have the same power. This is where torque curves, bore stroke ratio and other engine nerd stuff comes in as some engines give more power at high rpm and others at lower rpm. The only way to compare is a fixed load compared between the two. Its just a benchmark still, but its all we have. 

 

I benchmark our engines on APC props and know what they should do. I can use this frame of reference when diagnosing if an engine is performing correctly or is down on power. Often a customer will say they need a bigger engine or their engine is underperforming, and very often i recommend an alternative propeller that is better suited to their model and performance of the model is improved. Even changing 14x6 of one brand to 14x6 of another can make a huge difference. 

 

This situation with propellers is not unique and going back to WWII the first spitfires and hurricanes had almost identical performance when flown with the 2 blade fixed pitch props they were using. Once upgraded to variable pitch while using the same engine and then constant speed props the spitfire took the lead in terms of its performance. Both aircraft used the same engine and the performance of both was hampered by the 2 blade prop. Changing the prop meant the limit to their performance was now airframe related so the sleeker spitfire saw more of a performance uplift than the hurricane with its thicker wing. 

 

Hope all that made sense. 

 

 

 

[Jon H]

Been a little while but the first batches of flat twins are now more or less ready. 

 

The 5 160's are done with 2 of the 5 200's also finished. As soon as i get more piston rings the other 3 will join their friends. I also have another 200 inline done with 4 more to follow in the coming weeks. My bench is getting rather crowded!

 

 

The production FT160 features a revised cam timing for improved performance and it now has even better response than it did before. The FT200's i ran today were complete animals and hit 9600rpm peak on an APC 17x6. 

 

The dumpy mufflers everyone voted for are also done (we are on version 3 already!) so you at least get something with the engine. I may be able to offer inline additional exhausts later but the one i flew with the older dumpy exhausts was very quiet in the air anyway. The mounts are WIP and i hope to ship the first engines mid-late next week. 

 

This is a video of the first production engine (in custom bare metal finish at the customers request) with the new cam timing. 

 

 

 

The first customers on the list have already been contacted so all of the current engines are spoken for. I will be doing a follow up batch asap but even this will not clear my list. If you want in, let me know and i will see what i can do. 

 

I do need to take a bit of a break from the new stuff though as stocks of normal engines are being neglected while my focus is on these so it might be a month or so before i get back to them after the first batch is done. I will see how things go. 

[Jon H]

Just a quick update. 

 

Production FT engines due to go out this week following a covid induced delay. All of the current batch of 200's are spoken for but one 160 is left alone, cold, frightened. 

 

If you would like to take in the stray 160 and give it a home then by all means give me a call. 

 

I have a 2nd batch coming which will be another 4 of each size. The 200's are already spoken for as are two of the 160's (i need a pair for a customer building a twin so my current lonely one cant help). 

 

It looks like a 3rd run of 200's will be needed just to clean the initial demand but these will have to come after a run of 200 inline's and at some point i should probably build some single cylinder engines. If you want a 200 flat we are already looking at at least 2 months for any sort of availability. 

 

 

[Nick Somerville]

Pretty sure I asked already, but is a 300 flat on the cards Jon?

[Jon H]

4 hours ago, Nick Somerville said:

Pretty sure I asked already, but is a 300 flat on the cards Jon?

 

eventually

[Jon H]

Just going to take a moment to mourn the passing of the Laser 120 and 240v, both of which are now discontinued.

 

They got the chop as other engines in the range are better value, sell better, and we needed to thin the herd a little with all the new stuff coming along. Both will be supported for spares and service so dont panic if you have one. 

[richard dalgleish]

Hi Jon

What Laser would you now recommend for the BT 70" Spitfires and the Hurricane? I thought the 120 would of been a good seller. 

[Jon H]

1 hour ago, richard dalgleish said:

Hi Jon

What Laser would you now recommend for the BT 70" Spitfires and the Hurricane? I thought the 120 would of been a good seller. 

 

so few of these models are built now that it is pointless for us to build an engine just to suit them. I guess we sold maybe 3-5 engines a year for BT Spitfires, Mustangs, Hurricanes and 109's combined. I know they have an almost mythical status, but realistically there are better options these days and i have never been impressed with the BT models. Yes they look great and fly very well, but their designs are out of date and often not well suited to the rigors of week in week out club flying. 

 

The 120 has never sold well and its had more lives than a cat in terms of avoiding the grim reaper. But we have run out of all its parts at the same time on this occasion and its simply not worth making more. I have a handful of crankshafts and cylinders left, and these will be held for spares support going forward. 

 

 

[Scott Edwards 2]

Alas poor 120, we knew him well,

But like the 240, it did not sell.

With the right size prop it came alive,

But wasn't as nice as the 155.

 

 

Laser 120 RIP.

Send no flowers.

[Ron Gray]

10 hours ago, Jon - Laser Engines said:

mourn the passing of the Laser 120 and 240v, both of which are now discontinued.

What a great shame, I love my 120 and 240v, brilliant engines, but then so are all the other Laser engines I have!

[David Davis 2]

So there's nothing between the 100 and the 155. Would either of these power a Brian Taylor Spitfire?

[Jon H]

2 hours ago, David Davis 2 said:

So there's nothing between the 100 and the 155. Would either of these power a Brian Taylor Spitfire?

 

Not really. the 100 is a bit small and the 155 a bit big. Tank placement could also be problematic. 

[Jon H]

10 hours ago, Ron Gray said:

What a great shame, I love my 120 and 240v, brilliant engines, but then so are all the other Laser engines I have!

 

Yea mechanically both engines are just fine. The problem is, we never sell any. 

 

 

[Martin McIntosh]

A 155 is currently in one of my TN 72" Spits and fits OK so I would have thought that the BT one should be fairly similar. Best of luck with a BT design though.

[Ron Gray]

47 minutes ago, Martin McIntosh said:

Best of luck with a BT design though.

?

[David Davis 2]

7 hours ago, Jon - Laser Engines said:

 

Not really. the 100 is a bit small and the 155 a bit big. Tank placement could also be problematic. 

That's interesting.

 

According to the information from Sarik on the Brian Taylor Spitfire Mk 1a plan which has a 69" wingspan, an 80-90 four stroke or a 60 two stroke  would be adequate to power it. https://www.sarikhobbies.com/product/supermarine-spitfire-1a-69-plan/

 

I cannot find any reference to a Brian Taylor Spitfire with a 72" wing span.

[Martin McIntosh]

69 or 72 would not make that much difference. If the BT Mossie I tried to build is anything to go by, the construction is very flimsy and the hidden hinging a nightmare. A couple of competition flights a year would have been all it could have withstood had I not abandoned it. If very light then a 90fs may do it, but who would want to fly a Spit on a 2st? An OS 120 would seem to be the best option.

Sorry that this is rather off topic.

[Jon H]

Do you have one of these models awaiting build DD?

[David Davis]

4 minutes ago, Jon - Laser Engines said:

Do you have one of these models awaiting build DD?

 

No but years ago I bought a Brian Taylor Harvard from an old boy in Somerset. He'd made a lovely job of it, retracts, oleos etc but I've always been too scared to fly it. Since retiring to France, my flying has improved, especially my landings.  IIRC he'd flown it only once powered by an OS 70. I have an old but sound Laser 90 which I could use.

 

https://www.sarikhobbies.com/product/north-american-at-6-texan-harvard-68-5/

[Jon H]

2 hours ago, David Davis said:

 

No but years ago I bought a Brian Taylor Harvard from an old boy in Somerset. He'd made a lovely job of it, retracts, oleos etc but I've always been too scared to fly it. Since retiring to France, my flying has improved, especially my landings.  IIRC he'd flown it only once powered by an OS 70. I have an old but sound Laser 90 which I could use.

 

https://www.sarikhobbies.com/product/north-american-at-6-texan-harvard-68-5/

 

Wrong DD ? 

[David Davis 2]

5 hours ago, Jon - Laser Engines said:

 

Wrong DD ? 

No I'm the same David Davis. It's just that when I use my lap top in bed first thing in the morning with a cup of tea by my side, I'm David Davis 2 and when I use my PC I'm David Davis with a nice picture of me carrying my Big Giff after its maiden flight!

 

I'm not very good with computers!

[Jon H]

ohhh i see. 

 

Well the AT6 is an easy one as the engine can mount sideways so fuel tank placement is a non issue. Given the performance of a t6 and assuming it is around 10 lbs an 80 or 100 should do just fine. Your 90 would also fit the bill. 

[Jon H]

FT update

 

Initial customer feedback revealed a design issue with the engine mount (my bad). As the fuel pipes come through the bulkhead behind the engine the exit into the engine mount but have nowhere to go. So i made a small tweak to get around this issue. 

 

You have a number of choices with the new setup. 

 

First, twin tank or twin clunk single tank. A nice neat pipe run to the carbs can be done with the two outer holes. The inner one can be a fill or left open.

 

 

There are also holes at the bottom of the mount for fill/drain/vent lines as required

 

 

These also come in handy if you decide to use a single tank/clunk and a T in the fuel line. For this you use the middle hole in the top

 

 

 

So there we are, small upgrade but it should make the engines easier to install. If anyone already has an engine and wants their mount upgraded post the mount back to me ASAP and i will sort it as the machine is running them now and we can get them upgraded. 

 

All engines that leave after today will have the upgraded mounts. 

[Ron Gray]

Too late!

 

Before -  Laser 180

 

 

After -  Laser 200FT

 

 

Fortunately the twin fuel lines come from below the engine mount so it won't affect the installation.

Edited March 31, 2022 by Ron Gray