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AcroWot XL Build

A possible build thread if I'm very good at home

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cymaz10/02/2019 17:20:20
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That ain’t no Laser, you dark horse Jon. Do tell!

Jon - Laser Engines10/02/2019 18:22:16
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Posted by cymaz on 10/02/2019 17:20:20:

That ain’t no Laser, you dark horse Jon. Do tell!

Nope, OS FF240 Pegasus. I got the engine in a sorry state with extensive rusting of the ferrous parts, a bent conrod, broken valve springs etc. I did have doubts about if it was beyond rescue but i was able to work my magic on it and got it running again. I test flew it in another model, only 2 flights to see if it worked at all and it seemed to work well enough to justify a better model so i bought the AWXL as it was the cheapest model i could buy that would suit the engine and give the the opportunity to give it a good flight test and get some use out of it. In the long term i have my eye on the H9 Vans Rv4 but that is alot of money to spend if the engine lets me down.

At the end of the day, while i work for laser i must congratulate OS for building an engine like this. It was never going to be a money maker, and there are far more efficient powerplants available, but it really is cool and as an engine enthusiast i cant help but like it.

cymaz10/02/2019 19:26:23
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Jon, I bet it is vibration free. Any chance of a video....pleeeeeeeeeeease face 1

Jon - Laser Engines10/02/2019 22:50:04
4329 forum posts
159 photos

it does run pretty smooth. I have to make an exhaust for it and i hop the parts will arrive for that tomorrow. If so i will work on it through the week and hopefully run it up next weekend. It might even fly if the weather is good and the test runs go well.

Tim Flyer11/02/2019 09:02:55
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884 forum posts
145 photos

Gorgeous! ....would like to see how your air ducting works..that must have taken a fair bit of planing to get air to the rear cylinders in a fairly compact cowl. Makes me wish again for a Laser flat twin😉... I know they aren’t going to be made in the foreseeable future but I can still hope...

Jon - Laser Engines11/02/2019 09:19:11
4329 forum posts
159 photos
Posted by Tim Flyer on 11/02/2019 09:02:55:

Makes me wish again for a Laser flat twin😉...

Shhhh!! you will get them all started again!

anyway, the cowl air inlets have been opened up a fair bit and as you can see in the photo there are baffles right at the front to divert the air up into the top of the cowling. The air cant get out of the back as there is another baffle just behind the rear cylinders so it will all go down, through the cylinders, and then exit out of the bottom of the cowling...or at least that is the theory!

Frank Skilbeck11/02/2019 09:24:32
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4251 forum posts
101 photos

Be tempted to put telemetry temperature sensors on each cylinder to see if the rear cylinders run hotter.

Always puzzles me why some modellers get such an engine and then allow them to get into this sorry state.

Edited By Frank Skilbeck on 11/02/2019 09:25:50

Jon - Laser Engines11/02/2019 10:01:46
4329 forum posts
159 photos

I dont have a telemetry radio so that is not an option for me. I also dont really see it as being necessary as my baffle design should work. Clearly i will do some testing before getting into the air. Another thing that is on the engines side is that the carb pokes out of the bottom of the cowl so it will always draw in cold air and this will also help the cooling.

As for the original condition of the engine i agree with you. Someone had left fuel in the engine and it rusted the thing almost solid. Some of the valve springs had turned to dust the rusting was that bad!

I have a few photos of it here

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Alan Gorham_11/02/2019 11:12:33
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88 photos

Jon I'd be interested to hear more on how you sorted out that engine (perhaps in a new thread). I assume you restored the existing parts and didn't just buy and fit new replacements as that would be very costly?

Jon - Laser Engines11/02/2019 11:35:39
4329 forum posts
159 photos
Posted by Alan Gorham_ on 11/02/2019 11:12:33:

Jon I'd be interested to hear more on how you sorted out that engine (perhaps in a new thread). I assume you restored the existing parts and didn't just buy and fit new replacements as that would be very costly?

In retrospect i should have done a thread on the rebuild as i went along as it was quite interesting but at the time i got started i was more annoyed with it than anything else!

The short version is new bearings, valve springs and piston rings. I also renewed the rounded off screws. This was a challenge as there are 10 different sizes of screw in this engine and some are right oddball sizes like M2.6x7 and M2.6x8...why? just why would you do this?

Anyway, i was able to very gently straighten the bent conrod (its bronze and i wasnt spending 90 quid on 2 new ones) using the press here at Laser and put it all back together after a long period of shot blasting the rusted components.

As my order of bits just arrived i hope i can get the exhaust sorted out this evening ready for test runs later in the week

 

 

Edited By Jon - Laser Engines on 11/02/2019 11:42:32

Alan Gorham_11/02/2019 11:51:13
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657 forum posts
88 photos

That's good to know Jon thanks. I guess it helps being surrounded by the right kind of tools and machinery.

I changed all the bearings in an old Gemini twin last year and it was "interesting". As you say, odd bearing and screw sizes.

Jon - Laser Engines11/02/2019 12:55:09
4329 forum posts
159 photos

yup, if i remember rightly the flat 4 uses 6 different bearing sizes. Again, why you do this OS?!

Tim Flyer11/02/2019 13:56:02
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884 forum posts
145 photos

Probably as they need to sell the “unique “ spares at high prices , as you said it’s very hard to make any money from the the engines and they probably have to to recoup some costs possible by selling spares

Edited By Tim Flyer on 11/02/2019 14:03:32

Paul Marsh11/02/2019 19:29:11
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3482 forum posts
963 photos

I have a 320 Pegasus. Lovely engine. So the 240 is around 40cc. Don't think it will be over-powered, but they sound nice.

Video:

Edited By Paul Marsh on 11/02/2019 19:33:17

Jon - Laser Engines12/02/2019 08:40:44
4329 forum posts
159 photos

I was able to make my exhaust last night but im not very happy with it so i think a MkII will need to be sorted out during the week

Tim Flyer12/02/2019 09:57:41
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884 forum posts
145 photos

I ripped out the elevator snakes last night . I just wasn’t happy with them. They had a bit too much slack for my liking and didn’t properly return to centre. I had to be firm with myself...if I don’t like something that important there is no way I’m going to fly with it on Model. I’m going to use the tail servos I think like I did on my WW and similar to Paul’s. That will mean battery relocation into cowl and possibly nose weight. I don’t think I will use the rod as my internal mods for the snake stop ends will need removing and that’s a fiddle.

Edited By Tim Flyer on 12/02/2019 09:58:20

Paul Marsh12/02/2019 20:00:37
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3482 forum posts
963 photos
Posted by Tim Flyer on 12/02/2019 09:57:41:

I ripped out the elevator snakes last night . I just wasn’t happy with them. They had a bit too much slack for my liking and didn’t properly return to centre. I had to be firm with myself...if I don’t like something that important there is no way I’m going to fly with it on Model. I’m going to use the tail servos I think like I did on my WW and similar to Paul’s. That will mean battery relocation into cowl and possibly nose weight. I don’t think I will use the rod as my internal mods for the snake stop ends will need removing and that’s a fiddle.

Edited By Tim Flyer on 12/02/2019 09:58:20

I hate snakes as well, any slop will be amplified at the end, and can rise to flutter ending up with structural failure. Dead easy to mod, just cut the holes apart, to clear the servos and put some reinforcement on the inside, and dead short links. There is not even 1mm of slop on either surface, and added to that if one servo goes south, you have some control.

Jon - Laser Engines12/02/2019 22:16:36
4329 forum posts
159 photos

I have new exhausts now. MkII is satisfactory.

Pictures to follow as i only just got done and its time for dinner, shower, bed!

Chris Freeman 313/02/2019 05:07:44
142 forum posts
156 photos

Gee that is a good looking motor, I hope it rewards you with lots of reliable flights. I am sure it must have been heartbreaking to see it in the original condition and became a bit of an obsession to fix.

Tim Flyer13/02/2019 09:01:33
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884 forum posts
145 photos

Cheers Paul . The worst bit was clearing out the mess as I had “gone to town” as usual putting the snakes in . However luckily I had used epoxy. That is quite easy to remove with heat. A soldering iron on my metal bracket and screws soon had that out. The inner supports were more of a fiddle and the dremmel with permagrit grinder came in handy. I also had to remove the batteries from their current position near the tank and will make a mount on the firewall. I quite enjoy the construction bit but going backwards and removing bits is a pain. I’m going to put some Savox SC1251 low profile servos on the tail as they are only just under 16.5mm deep. I also have them on the tail of my WWXL and Wot 4XL and they are good. Anyway I wonder why I tried the snake experiment ! But at least I know better now 😊

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