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Which engine for my old Junior 60.


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I have an old Junior 60. In fact I learned to fly on this model.

junior sixty (1).jpg

Last year I bought it back from my cousin to whom I had sold it many years ago. He had never flown it.

It was orginally fitted with an Irvine 20 but I couldn't get it to run satisfactorily even after replacing the original carburetter, so I installed an HP VT 25 four-stroke. That would not pull the skin off the proverbial rice pudding and the model had to be hand launched. However, once in the air it flew well enough if extremely slowly.

Like most established aeromodellers I have more engines than I need but an SC 32 is the smallest engine I have. So, do I install the SC or should I fit my Merco 35 or OS 48 Surpass?

Or should I just buy a new two-stroke ASP from Just Engines. If so, should I chose the 21 or the new 25S?

Or should I convert it to electric power? I have a number of motors, speed controllers and 3S and 4S LiPos skulling about doing nothing.

I intend to use the model as a trainer for nervous elderly learners.

The opinion of the cognoscenti is urgently sought! wink.

Edited By David Davis on 29/07/2017 07:51:01

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An SC 30 four stroke would be perfection but the OS FP 35 would be more than enough.

An ASP 21 would fly it well. A modern 25 would over power it.

One in our club was absolute perfection on the old OS 30. The one with the clamp on silencer. I always called that engine the poor man's four stroke.

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I, too, used an irvine 20 and learned to fly with it in a J60. As I reckon Irvines are probably the best 2 strokes out there I wonder what you did wrong to fail to get it to run properly.

Mine was a diesel and, after I got fed up with the gunge down the side of the plane I converted it (with the free glow head that came with it) to glow and I didn't even touch the low speed needle.

I have another J60 now with an os 26 surpass but want to change it for either an os 20 fp or 25 fp, both of which overpower it to some degree. Failing that I still have the irvine 20 but regrettably it's too noisy for me.

Incidentally it's possible that an exhaust manifold extension of about 10 mm will be required to clear the cockpit with the OS engines.

If you want an OS 20 FP I have one that has only been run in in my J60, at my age I'll probably never use it. If you're interested pm me as I need some more cash for my coffin fund.

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Posted by gangster on 29/07/2017 09:23:22:

For the job you intend maybe electric is the answer would be totally reliable on a couple of hundred ways and 11 inch prop. Failing that go for the SC21

I've just noticed the Thunder Tiger 28 at SMC. That looks tempting at just over £60.

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I flew a friend's J60, he had an OS 25FP in it, and it was perfect IMHO. Full power was ideally used to climb, but then once to height, the engine was throttled back to little more than idle. So, I do see the 20FP as an option.

I had a Merco 35 in a Shuco Hegi (spelling?) Snoopy, which was a German Super 60 type model at 5lb, and again, that was a perfect option (bought from the local German model shop). If you use the Merco, please do put a ring of silicone tubing between the needle valve and spraybar to stop air leaking down the screw thread - it makes a massive difference to the throttling.

Regards,

John

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Posted by Braddock, VC on 29/07/2017 09:27:02:

I, too, used an irvine 20 and learned to fly with it in a J60. As I reckon Irvines are probably the best 2 strokes out there I wonder what you did wrong to fail to get it to run properly.

If you want an OS 20 FP I have one that has only been run in in my J60, at my age I'll probably never use it. If you're interested pm me as I need some more cash for my coffin fund.

The carburetter was faulty on the Irvine. I got another different carburetter from Just Engines but it was a bit too small in the spigot to fit the hole in the Irvine's crankcase. On the suggestion of others, I wrapped masking tape around the spigot and squirted in some silicone to seal everything. I too was disturbed by the Irvine's noise so fitted a Just Engines strap on silencer. I could get it to run alright on the ground but it kept cutting out in flight. Maybe I'll persevere with it once the house I'm renovating is finished.

junior 60 with irvine 20 (2).jpg

I may take you up on that offer of the OS Braddock, and yes I'll have to relace that undercarriage!

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Posted by Hangar 9 nut on 29/07/2017 11:29:18:

I have an OS 40fs pre surpass flys for 25 mins on a 4onz tank and an 11x4 prop !

I tried one in my J60, very good match though I used either a 12x4 or 13x4 apc, can't remember which only took it out to try it in an 84" w/s southerner major, marginal in anything either over or under a 5 mph breeze.

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david...I must admit the one I have(built 1991) and now on its 2nd 4/st (OS 30),would have been electric from day one had it been around then...now I wouldn't even think about an ic engine...ok if you like the sound etc...but for quick clean and no dead sticks etc...it has to be Lecky....wont be long afore ic is probably banned for the emissions angel

ken Anderson...ne...1...... jnr 60 emissions dept.

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This is my Peyret Mauboussin Type 11. Powered by an SC 30 FS. It flies for about 20 minutes on a 4 ounce tank. Climbs to an incredible height in the hands of its new owner (I can't see it that high!!) and floats around all afternoon.

No oil or mess and super quiet.

Model is 76" span and flies like a big glider in spite of that fat fuselage. Sounds like a vintage model with that engine

peyret mauboussin pic 1.jpgpm 11 (15).jpg

I am planning to use my SC 30 in a Sig Kadet Seniorita Which is just like a light weight Super 60.

Now if that doesn't persuade you to go for the SC nothing will

Edited By Peter Miller on 29/07/2017 18:42:25

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As I mentioned on another blog I have just fitted an OS 20 in my 55 year old Keil Kraft New Junior 60 to replace the ED Racer purely to give me an extra 3 ounces of nose weight as fitting an elevator for the first time meant that the C/G of the plane was affected. Fortunately the OS 20 fits the same bolt / bearer spacing as the ED Racer as does my Enya Super Sport 30's and my old Enya 19 so I have got plenty of scope for engine testing.

pb030178.jpg

p7150087.jpg

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The last Junior 60 I had was a very heavy tired old plane but flew really well on a clapped out old OS 20 MAX . I have flown a lot of similar models for people over the years and all the slightly heavier ones flew better . The really lightly built models suffered from being blown around too much in anything other than perfect conditions. Any half decent 20 ish engine should do the job.

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Not wanting to detract from Braddock's pension fund, I do feel that there may be some misunderstanding as to where the Merco 35 fits in all of this. I found the Merco 35 totally useless in 40 type aerobatic models of the 70s, and as a low power loop scavenged engine, it is probably less powerful than the original OS FS 40 (which I also owned and used, and saw giving perfect service in J 60s).

The FPs are extremely refined, start easily, and run at low throttle settings for very long periods of time. Unlike the Merco 40, 49, and 60 (all of which I have owned and enjoyed, and all had alloy pistons), the Merco 35 has a cast iron piston, which does provide greater vibration, but has a character all of it's own!

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Thanks for all of the advice gentlemen, I think I will procede as follows:

  1. Repair the undercarriage.
  2. Try to get the Irvine 21 running more reliably but failing that install the Merco 35.
  3. Over the winter convert it to electric power and re-cover the fuselage and tailplane.

I haven't the heart to re-cover the wing as I've made such a good job of it! i have however managed to build in a warp which means that the model has to fly with considerable right rudder trim! An SC 30 fourstroke would be nice but I hate spending money and renovating my new house is costing me thousands so a new engine is out of the question!

surprise

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