New Laser engines. What do you want?

[David Ovenden]

Another vote for a 160 or 200 size boxer twin. A 3 cylinder radial would be great. I also think a 200ish size in-line twin would be a winner too. I can't wait!

[Former Member]

[This posting has been removed]

[Jon H]

A fuel pump is something I have been looking at for the reasons mentioned about ARTF models being a touch inflexible when it comes to tank position. Personally I have never had the problem as I have just cut out whatever was in the way and put the tank where it needs to be. However the number of calls I get about tank position seems to suggest that I am in the minority! I really don't want to move the carbs or put a bend in like os/saito as the engines can flood much more easily when inverted. currently it is impossible to flood a laser when inverted.

Gearboxes are something that I have again been thinking about but there are a number of issues to consider including the availability of propellers. I know most things are available now, but we need to be very careful when designing something that it can be supported all over the world.

ChrisB...Front carb? not quite sure I follow. Do you mean something like the old HB engines?

Ben, I regret that we have fallen well outside the realms of possibility here. Yes it would be cool, but totally useless in terms of power to weight ratio and extremely expensive due to the complication and very small market ( I mean it would be £2500 at least). I don't mean to be a party pooper, but at that size it would be totally unfeasible especially on petrol.

 

As a basic guide, there will be no engines of more than two cylinders with less than 50cc capacity because small multi cylinder engines are really gutless due to the mechanical losses.

 

The comments so far have surprised me a little as most of them are directed at engines far smaller than I expected with 20-30cc cropping up again and again. Radials seem to be in the 50-90cc range.

Is there interest in 40-60cc singles and 80-120cc V twins based on the same bore/stroke?

 

And a drone? with a laser? what is this madness!?

Edited By Jon Harper on 16/11/2015 21:26:37

[Ben Kenobi]

Guess I just need to build bigger - ah well - can't win a coconut every time. If I go much bigger than 26cc in my area the places you can fly disappear faster than a politicians promises post election - problem is that  the small engines tend to be too noisy (I don't like flying chainsaws).

Edited By Ben Kenobi on 16/11/2015 21:33:38

[Martin Harris - Moderator]

What are the (im)practicalities of a narrower V angle, Jon? WW2 models might benefit...

[ChrisB]

Thanks Jon. I was thinking of something like the OS55 front induction petrol but in 4s or something like the engine at the link below
http://www.moki.co.uk/eng30.html

Chris

[Jon H]

Chris those front induction engines are two stroke and so drawing in through the crankshaft is easy. I cant think of any 4 strokes that induct in that way. The HB engines had the carb at the front of the cylinder but they had a rotary valve in the head. It would be very awkward to try with poppet valves. We would need to turn the head sideways and have the cams parallel to the crankshaft. On a single there would be no advantages to this arrangement.

 

Ben is the issue with large engines noise related?

Martin we are likely to stick with the 90 degree V for numerous reasons like ease of manufacture. The main one though is balance and smooth running as the 90 degree V gives perfect balance and low vibration is ideal for models.

 

I just had a closer look at that link. The rpm figures they report for that 30cc are not fantastic. I can get more or less match that with our petrol converted 180

Edited By Jon Harper on 16/11/2015 22:27:15

[Ben Kenobi]

I'm pretty sure it is noise related I reckon if the engine was quiet enough nobody would be interested, I've never asked mind you but I can think of no other reason. I heard a Saito FG-30b running and it was impressively quiet even at higher RPM - whether this was exhaust or timing related I have no idea.

For what it's worth I plan to install something like the FG-30b in my TopFlite Cessna (despite many saying it's too big I could offer my reasons but this isn't the venue I think)

The only thing I am dead set on is 4 stroke and petrol, cost isn't a consideration.

Edited By Ben Kenobi on 16/11/2015 22:35:22

[Jon H]

For what its worth I agree with them, a 100 would fly that model really nicely. You might have trouble putting that must extra power in there.

Its interesting your comments about cost though, because many say the reason they don't like glow is the cost of the fuel and yet they buy a petrol engine that is often 50% more expensive than the glow version. I don't quite see how this is cheaper!

Incidentally, I know that another reason petrol is popular is its cleanliness. A simple solution is to use less oil in your glowfuel. We recommend no more than 15% oil and in fact 10% is a much better bet. I am also experimenting with much lower content down to 5% without trouble so far. My experiments continue....

[Moonpie]

Diesel??? There, I said it, the dirty oily word. Totally understand it will most likely never happen again being a very, very niche thing. Doesn't stop me from wanting one so bad it actually hurts a little bit though. Have seen a what I think was a 75 size Laser diesel in a Vintage plane at a St Albans event few years back. Was cooler than the cool side of the pillow.

[MattyB]

Posted by Jon Harper on 16/11/2015 21:23:46:

The comments so far have surprised me a little as most of them are directed at engines far smaller than I expected with 20-30cc cropping up again and again. Radials seem to be in the 50-90cc range.

Is there interest in 40-60cc singles and 80-120cc V twins based on the same bore/stroke?

I think this is to be expected given the models I see flown at the patch these days. 20-30cc aerobats and warbirds are relatively affordable and a common site amongst the average club pilots. Any bigger than that though and they become more trouble than they are worth in terms of storage space, transport, rigging and total cost. Given Lasers fantastic reputation I am sure there would be a market for almost anything you choose to make, but at >30cc they are unlikely to become a common sight IMO.

Posted by Jon Harper on 16/11/2015 21:23:46:

As a basic guide, there will be no engines of more than two cylinders with less than 50cc capacity because small multi cylinder engines are really gutless due to the mechanical losses.

I can get understand that, but did you see Brian Winch's review of the new Saito FG-19R3 in the last RCM&E? He recorded ~8500 on a 15x6; for comparison their FG-21 single does 8800 on a 16x6, so whilst no powerhouse it looks to have enough to be usable in a 15-20cc sized Corsair or Thunderbolt. Probably going bigger in the radials does make sense though - the first generation Saito Radials have got a very mixed reputation, so there may be a gap in the market.

[Bob Cotsford]

re noise - we operate an 80dBA limit and standard Laser silencers on a 160 V twin don't pass. In fact it's hard to get anything over a 1.20 to pass partly due to the noise generated by the large props but mainly because the simple silencers supplied (even with 4 stroke glow motors) are too simple. So how about a slightly larger, baffled silencer? Even if it added to the purchase price it would probably still be cheaper than messing with extended or additional aftermarket exhausts.

As for narrow V twins, Aprilia went that route with the V60 twin motors. To reduce vibrations to an acceptable level they needed complex balance shafts, which mean additional weight and complexity.

As for any form of in-line, I had a Sunbeam S7 motorbike many years ago, a 500 aircooled in-line twin. What was the major issue with both this model and Ariel's 'Square Four'? Keeping the rear cylinder/s cool. Don't go there. In-line engines really need to be water-cooled else they need complex air ducting to avoid heat induced warping in the rear cylinders.

[Dave Bran]

Jon,

Thanks for the chance to comment!!

Firstly, Petrol is a lure with people I know because:-

1. It's considered much cleaner on the plane.

2. Getting it does not involve an inconvenient trip to a poorly stocked model shop you otherwise would never visit.

3. You do not have to fly with one eye on a timer.

From much discussion the 20-25cc petrol power/size/weight is what people round here want, and the major constraint is noise. They therefore need something that they can be SURE will install without hassle and pass BMFA noise tests, while throwing their model around the sky with abandon.

Personally I don't care whether its a single or V12, or even what it looks like, I'm not buying jewellery to show off, I'm buying reliable easy starting economical to run QUIET POWER, and the more power per size the better.

I love fuel engines but increasingly am going Electric as I cannot find what I need, though in their case 3 above is the major issue.

I have two Lasers, my Outdoor 55" span plus hangar looking like:-

7 i.c. powered planes, three being four stroke, one petrol 26cc (Zenoah).

and in i.c. powered Helicopters, 1x70, 4x53, 6x30 class, all two strokes with expensive quiet pipes.

That is less than 20 i.c. models out of a total hangar of well over 100.

I have had a new DLE 30 for more than two years, still in its box. It's supplied "silencer" is a joke and I could not see how it could be installed into any of the planes in build in that time and meet noise regs.

The club I most use (being in several) is mostly populated with 46/53 two stroke or 70 4 stroke powered models. Another has more space, and there it seems most i.c is 20cc plus petrol, though IMO they are getting into more trouble re: noise than is comfortable or sustainable.

Noise, Noise, Noise.....................................................

[Braddock, VC]

As a smaller, lighter laser is ruled out then I'm afraid my answer is not a lot.

[Jon H]

Moonpie, if you want a Diesel i will build you one. I have recently reworked them and have 80's and 100's available as diesels. The run quite nicely now but do require special fuel and are in no way as refined as the glow engines and aimed at enthusiasts who dont mind spending a few hours getting to know the tricks of extracting the best performance from the engine. If you want more info best to give me a call.

 

Bob i am surprised by the news that the 160 cant get through your noise test as the exhaust note is (typically) very soft on the small engines. I would be interested to know what prop you were running as the engine is very quiet when flying on something like a 17x8. That said, exhausts are another thing we can look at and a simple experiment would be to use the large exhaust on the smaller engine. I can get one welded up and will test it asap.

 

Braddock i am sorry, but smaller engines just dont make any money. as i said before we had to discontinue our smaller engines over 20 years ago for this exact reason. Noone bought them and they were expensive to produce. I would love to do a smaller engine, but there just is no chance i am afraid as they would need to be sold at the same price as the 70, and i dont think people will pay 210 quid for a 50 4 stroke.

 

Dave i think you are right. It also seems to confirm what i have often though in that we need to almost have two tiers of products. Smaller 20-30cc stuff for club modellers and bigger stuff for 'show' models. As i said before, i am working on the basis that club level warbirds get to about 80 inch before they become impractical. This means engine up to about 40 or 50cc. Beyond that we are into big stuff that most of us cant deal with. 

Edited By Jon Harper on 17/11/2015 09:00:01

[Bob Cotsford]

Jon, I've run both 16*8 3 blade Master and 17*8 2 blade APC. While the noise level may not be excessive to the MkI lughole, it won't get below our club's 80dBA limit as tested on a calibrated meter. I note more and more clubs seem to be adopting 80dBA rather than the 82. The way of the future?

[Jon H]

80 is pretty low, and no doubt the test is being done with the meter set to record peak value? if so that is wrong and it should be set to average. i am also assuming you fail in the front reading? if so its the propeller making the noise and this noise will vanish when the model is flying as the prop is not stalled.

All of that said, noise is an issue as it always has been. I will get an exhaust or two welded up and see if it makes any difference.

[Tomtom39]

Hello Bob,

This issue of noise has been raised previously in various threads and is a rather tricky one . At my club (and I've was involved with obtaining planning permission). We have over the years tested our models at the pre-requisite distance with a ceiling of 81db (not too sure how this was reached but assume to show it would be below the recommended 82db). I was therefore amazed to find the Environmental Health Officer from the local council was not particularly interested in this. As far as he was concerned it was a case of noise (nuisance) perception at the point of the nearest dwelling. I understand that the 82db is used as a guideline and that different councils/EHO seem to have ideas on how they go about granting permission for an activity that is likely to cause noise nuisance or a complaint . As a consequence we not only test our models but also on a regular basis drive  close to the nearest houses to listen as to how the "noise" can be heard etc . We have had to request members to give some consideration as to how they fly and use of throttle etc (the alternative being that we lose our strip!).

Just to confirm with one exception, I've had all my models fitted with Lasers pass the club test .

Edited By Tomtom39 on 17/11/2015 10:31:20

Edited By Tomtom39 on 17/11/2015 10:37:11

[Tomtom39]

Should read " ideas on how to go about granting permission for any given activity which may create a disturbance / complaint"

[Bob Cotsford]

I can't be certain but I think it was a side reading that was peak. As for whether or not it should be an average, I'm afraid that is up to whoever made the agreement with the council that got us planning permission.  I'm pretty sure that Paul does actually test using the 4 reading average.

I do know that using a baffled 1.80 size exhaust on an ASP 1.20 four stroke makes the crucial couple of dB difference.

So Jon, as a final derail for this thread, is there a larger silencer that will fit on the 1.60?

Edited By Bob Cotsford on 17/11/2015 10:50:15

[Jon H]

There is currently no larger silencer for the 160v but i have already spoken with the boss and we are going to make a few prototypes using the current exhaust of the 150 single. Much larger can volume so it will be interesting to see if it has any effect. If you email me a photo of your installation to [email protected] it will give me a clue as to whether this new muffler will fit.

And tomtom is quite right. The actual noise we make is (almost) of no consequence, it is how annoying it is to folks nearby.

[Martin Harris - Moderator]

One tip that may apply to Lasers in particular due to their exhaust geometry is to avoid angling the exit pipe into the prop wash - one that I was noise testing failed miserably but then passed easily with a simple silicon pipe cut at an angle facing backwards (like the old style diesel filler vents). You could also use an angled deflector.

[Bob Cotsford]

Thanks Martin, that is certainly worth trying.

[Derek Stevenson]

Jon, I'm intrigued with your oil comments, this seems to come up when we talk about fuel. If the Laser runs better on 10% surely it is waste running it on 18% never mind almost twice the mess. A difficulty we have in Northern Ireland is fuel must be transported across the sea, to get a decent price we have to buy bulk (as a club) so our choice is 5% or 10% & oil content may be unknown (as some fuels will not declare it). 5% oil must scare some folks but it is interesting to hear an expert looking at it. I just recently purchased a second hand Laser 70 cheeply 😆 as I've been jealous of a fellow club member who flies nothing else. Mine, like his runs like clockwork and a beautiful tick over. Hopefully the magazine will publish you findings on oil quantity when you finish your testing?

[Jon H]

Hi Derek

our oil testing came about following my experiments with our petrol engine. I simply could not run it on 20:1 because of the god awful mess it made. I switched to 40:1 very quickly and now am running 50:1 in an engine with identical mechanical parts as the glow engine. 50:1 is 2% oil and given than it uses about half the amount of fuel a glow engine would its is in effect 1% and after more than a gallon the engine is perfect internally.

Neil has been running his glow engines on 10% oil and 5% nitro for over 2 years without any ill effects. We have a few customers doing the same.

I have put a full gallon though a 150 at 4% oil and again it didnt seize up so all is well there. 4% is very low though so more testing is required before we recommend this but 10% is perfectly ok.

 

If a low oil glow engine would keep the masses happy then we can make one of those. With 5 nitro and 10 oil it would only be about 15 quid a gallon.

Edited By Jon Harper on 17/11/2015 16:05:08