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Member postings for Jon - Laser Engines

Here is a list of all the postings Jon - Laser Engines has made in our forums. Click on a thread name to jump to the thread.

Thread: Laser Engines - Technical questions
03/09/2018 23:54:34
Posted by Rob Tothill on 03/09/2018 22:32:14:
Thanks Jon,
It is an APC.

Should there be a gasket for the rocker cover? It doesn't have one and seems to be leaking a bit of oil. I'm not bothered about the dripping oil if it won't cause any problems.

it should seal on its own but if not clean it all with meths and give it a little wipe of silicone sealer

03/09/2018 15:33:04

dont get too crazy about valve clearances guys. as long as they arent stupid the engine wont really give a hoot.

If you dont have a feeling guage then tighten the adjustor down until their is no play, then back it off 1/8 turn and nip up the nut. You should be able to feel a little bit of play, if so, its all good.

15x6 apc (??) at 9k is fine for a 120.

Manish, to be honest im not sure. It could be fuel draw, could be turbulence, could be your fuel or something else. If its over revving i would expect it to behave as you describe..there's loads of reasons. Its not something i have ever noticed and if it runs fine in the air then dont worry about it. I would have test run the engine before i sent it so if something was wrong i would have seen it.

Thread: What cc petrol engine ?
02/09/2018 17:29:16

I would agree with Don. A DLE 20 is almost exactly the same as our 23cc 150 and slower than the 25cc 155.

It makes an awful noise though. Get an after market exhaust for it as its really not at all pleasant without it.

Thread: Laser Engines - Technical questions
30/08/2018 21:23:47
Posted by Martin McIntosh on 30/08/2018 15:05:30:

Not a question but a trap I fell into with my 155.

Found a Xoar 18x7 at the nats so decided to try it. Prop nut well tightened but after about 8 mins there was a nasty sound as though it was loose. The motor idled normally so I landed it for a look at the problem back home. The nut was still very tight but each time I attempted to start up it was thrown off. The washer was locked tightly onto the shaft and took quite some removing. The prop rear was burnt, with the burnt bits embedded into the driver.

It turned out that the prop was thinner at the root than those previously used so that the nut was only tightened onto the unthreaded part of the shaft and not really grabbing the prop. A thicker washer cured it.

props sure do make a weird noise when spinning slightly slower than the engine they are attached to. You get a weird optical effect through the blades too

29/08/2018 13:36:26

It sounds like there is a piece missing from your needle. They should have a washer for the spring to push on as shown below.

20180829_133413[1].jpg

Thread: Seagull Mosquito weight
27/08/2018 23:41:34

I would set the elevator rates as low as you can Chris. In general I take the low rate from the kit instructions and set my low rate about a bit lower and high the same. With a recommendation of 15 I would probably go for 10 and 15. I work on the basis that I should have my bases covered with this at least for the maiden flight. I start with high for takeoff but take great care to not yank at the stick until well clear of the ground. Its also my standard procedure to belly land somewhere soft in the event that the model is 'uncontrollable' in pitch. Its something I have done only twice but its better to do that than try to land and smash the undercarriage. I usually find that most warbird manuals have way too much elevator deflection so ignore them now. As you have a recommendation from Richard of 8 then I would use 8 low and 12 high? something like that.

Personally I don't use any expo until the model is flown and even then its rare I use any and I have never found the need to use more than 10%. I agree with Richard that the argument about whether to use it or not could rage for a week so best not to get into it. I think his recommendation is pretty sound, if you use it normally then use a bit, if you don't then don't.

As for balance, I would go right way up as Richard suggests with gear up and no fuel. This is going to be the model tail heavy condition the model will see so even if its a shade tail heavy two tanks of fuel and lowering the gear will fix it.

I would suggest getting the gear retracted asap on the maiden though. Get the drag off the model, clean up the airframe and go from there.

 

Edited By Jon - Laser Engines on 27/08/2018 23:44:09

Thread: ASP settings query
27/08/2018 22:07:08
Posted by ASH. on 27/08/2018 20:00:58:
 
"Remember too that rpm will drop as the engine heats up..."
 
Why is that Jon ? I would like to know the technical reason for that? Is it because the chrome plated cylinder expands?

yea the whole thing expands, valve clearances go larger, the fuel charge entering the cylinder is warmer/less dense. There are many reasons

27/08/2018 18:18:43
Posted by Ronos on 27/08/2018 16:19:19:

Hi Jon ,it's Masters Airscrew K .

Those will be a bit slower so mid 9's is probably fine

27/08/2018 15:54:44
Posted by Ronos on 27/08/2018 13:35:57:
13x6 Jon.

they should be revving like crazy if they are APC. I expect 10000 out of that prop on a laser 70 and a friends OS70 was slightly up on that if I recall. Another friend has an SC70 and he used 13x7 JXF props but I cant recall the rpm. I think it was mid 9000's

27/08/2018 13:24:00
Posted by Ronos on 27/08/2018 11:24:27:

Hi Jon, been using the ear on the high needle, then dropping a could of clicks as it loses revs, then doing a pinch test but using the tacho setting the idle and doing a pinch test at that. the idle is nice at a steady 2300.

ok that's good. Personally I have never used the pinch test and instead slam the throttle open from idle to check the pickup is strong. That said, 2300 is a good idle rpm for an ASP 70 so its not really important how you got there.

What props are you running on them?

27/08/2018 11:03:15
Posted by Ronos on 27/08/2018 09:11:15:

Setting the high needle yesterday, was a little frustrated, while leaning it out, screwing in the needle about 1/8 at a time, at full throttle, the engine was very slow to respond to the change, became very erratic going to about 9300 revs from about 8400 revs, then back again. sort of got the high end set but not happy with it because of the inconsistent revs. Tried a new plug (F type,OS) still the same, and new fuel. I have ordered some Laser 5% to see if they run better, they recommend to 5% I am using optifuel 12% because been using it on my Escale Seafire SC120FS and that's fine. Any idea? new engines or am I being impatient.

ASP needles are not known for their accuracy and can leak air slightly when you twiddle them as they move in their housing. Try sliding some fuel tube over the joint between the needle and the carb, this might help.

Remember too that rpm will drop as the engine heats up so if you are spending a long time at full power trying to tune it then you will start chasing your tail. Don't tune with a tacho either as this will also lead to rpm chasing.

I have seen rpm chasing many times with customers as they tach the engine on its first run up to full power and see, for example, 8500rpm. They then tweak the needles, check revs again and find 8300-8400. This is normal and due to the engine heating up. They then spend the next few minutes at full power screwing the life out of the needles trying to get their 200rpm back. All the while the engine gets hotter and hotter, and slower and slower.

Tune them by ear, it should take no more than 10 seconds to find the optimum position. Then hold full power for 15-20 seconds and if there is no noticeable sag in the revs during that time then its ready to go.

Listen too for a sharp cracking noise. Its subtle, but if you hear it then you are knocking slightly and might need to go 1 or 2 clicks rich.

26/08/2018 16:19:15
Posted by Ronos on 26/08/2018 11:13:56:
Can I jump in and ask something, I have two ASP70FS for my mossie, both have went through the running in process via manufacture instructions and a extra tank for good measure. Setting the high needle, full throttle, leaning it out untill reaching highest rev, with a tacho, then dropping it down a couple of hundred rpm. After stopping the engine I wound the high end needle in to see how man turns it was from fully closed, just short of one turn. Is this OK, is every engine different, my SC120FS takes about two turns for fully closed?

I always tell my customers that the correct settings for the needles are the settings at which the engine runs correctly. There is no one size fits all X no of turns gets the job done answer to this question so if your engines are happy as you have them set then its all good.

Thread: Seagull Mosquito Laser build
24/08/2018 08:29:14
Posted by Chris Walby on 24/08/2018 06:29:19:

You will probably have finished yours before I get the engines in mine as I am still messing about with the cowls and beefing up the nacelle box.

And waiting for me to send him the engines im working on it, dont panic!

Thread: 7.4v Receiver pack/batteries/servos
22/08/2018 16:38:09
Posted by Gary Manuel on 22/08/2018 13:02:50:
Posted by Jon - Laser Engines on 21/08/2018 16:54:51:

What's confusing about avoiding the use of lead in a model to keep the weight down?

The less mass a model has, the less lift it will need to fly, which means it can get sufficient lift at a lower speed. i.e. lighter models fly better.

If possible, I always adjust the CoG of a model by choosing / using the most appropriate equipment / positioning. I don't think I own a single model with added lead. I dare say I might need to add lead if I flew scale models but I'd always try to use "useful weight" (larger engine maybe) before adding lead.

up, cant disagree with anything you say...but, if you have an engine that is of adequate power for the model, and is X weight + Y lead to balance, and swap it for an engine that is equal in weight to X+Y the model remains the same weight and yet the engine is likely to have cost you more adding to the overall cost of the model. Its also likely to use more fuel so you need a bigger tank which makes it heavier if anything. The added power is of no use to you as you had enough before. It may also be louder which could upset the man with the noise meter. As an example, this would be like taking a 63 inch spitfire and swapping its perfectly adequate 90fs for a 120fs. In this instance the 120 is likely to make the model more difficult to fly due to its higher static thrust (for landing) and torque swing on takeoff.

I agree that all efforts should be made to minimise ballast by shoving the equipment around and making things lighter down the back end but their comes a point where you just need to add the lead. My Sea Fury is a case in point. 60cc engine in the nose with a heavy ali spinner, as well as two sub-c batteries as far forward as they can go. This was not enough so there is 1.5lbs of lead on board just under the engine. I couldnt have done any better.

Thread: 4 Strokes - fuel tank position
22/08/2018 10:04:50
Posted by SR 71 on 22/08/2018 10:00:46:

I have the TN Lancaster with four ASP52 fs in it, never flown as I cannot get all the engines to run on low or tick over throttle, tanks are on the centre line of the carb, I've been advised to fit on board glows to come on at low throttle setting,baby advise welcomed as I've had it five years now, and it needs to fly,

Thanks Tony

 

 

If you have to resort to OB glow something is wrong. ASP engines are not the best (obviously cheeky ) but they should idle fine.

My guess is its a slow run tuning issue as most ASP's come slobbering rich on the slow run.

To cover the bases what props, plugs and fuel are you using?

 

Edited By Jon - Laser Engines on 22/08/2018 10:05:48

22/08/2018 09:49:12
Posted by Ronos on 22/08/2018 08:32:48:

Thanks Jon, I had a idea it would. Out with the Dremmel.

yes

From what Chris tells me the nacelle boxes fall apart very easily so it should not be an issue. I recommended to him that he add another 1/16th ply laminate on the inside of the box to beef it up a little as they are a little wimpy. For electric or 2 stroke they are probably ok, but a big 4 stroke has so much more grunt and it may cause issues down the line. Its much easier to beef them up now before its all oily!

I would mount the tank with the outlet at the level of the old tank bay floor. From the photo that looks about right

22/08/2018 08:28:46

Yup, that will cause issues. I recommend you cut through the bottom of the tank box and lower the tank. You can then build back the structure with another plate above the tank. Should be a pretty simple mod and well worth the effort. you need maximum reliability for a twin so there is no point in messing about.

Thread: 7.4v Receiver pack/batteries/servos
21/08/2018 16:54:51

cant beat a good smirk. And its not just you, the whole argument confuses me, and as you say you an dig a much bigger hole with lead.

Anyway if you use mini servos, digital or otherwise, i suspect they will be quite happy on a 1200 4.8v pack. If you use spektrum then 6v is a better bet

21/08/2018 13:42:43
Posted by Flyer on 21/08/2018 11:09:44:
So would hoping this would be 'useful' weight rather than ballast. If that makes sense.

This always makes me smirk. Lead, or any type of ballast is useful weight. It keeps the thing in balance!

Perhaps dual purpose weight would be a better description

In any event, would a nimh be lighter? also which servos are you powering? I use 6v nimh to drive 10 digital jobs in a warbird, 3d would probably be different

Thread: Austerity BF109G
21/08/2018 11:08:49

Looks good to me, makes me want to engage it in 'combat'. I have a 5th scale La7 or P39 to choose from

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