RE: SK ENGINES

RE: SK ENGINES
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RE: SK ENGINES - 10/23/2007 9:23:49 PM

Harry Lagman

Posts: 1153
Joined: 11/19/2003
From: Auckland, NEW ZEALAND
Status: offline

quote:

ORIGINAL: TestPilot6

Xjet,
I'd appreciate it if you can tell me any tips you found about the Easy Trainer to mount a .90. As it comes in ARF, Easy Trainer is a very sweet flying plane. Like SK engines, the price is very attractive.

Testpilot, the aircraft XJet was flying on the video is known locally as an "AT 40". It is made by some nameless concern in China.

The AT 40 has arguably been one of the most influential and important RC ARF models of all time in this country. It is the best flying, most versatile and toughest trainer I have ever flown, and, as an instructor, I've flown a few...

We have mounted all sorts of engines in these things and have successfully pylon raced them. I have one with a YS 1.10 in it, with two bays clipped from the wing. Amazingly, it still flies gently enough at low throttle to serve as a buddy box mule for training students.

It has a 65" span and comes with an integrated wooden beam mount, as opposed to a separate mount that bolts on to the firewall. Does this sound like the same model as your Easy Trainer?

(in reply to TestPilot6)

Post #: 451

RE: SK ENGINES - 10/23/2007 9:24:49 PM

OUTCAST

Posts: 880
Joined: 1/5/2002
From: ., NJ, USA
Status: offline

Sorry I bow to the guru of nitro.
I don't know whats wrong with me, I should have surmised you would know everything there is to know, far more than the factory that makes it, and still managed to get another plug in for TT
Outstanding work XJet, keep it up I cant wait for your next episode.

(in reply to Harry Lagman)

Post #: 452

RE: SK ENGINES - 10/23/2007 11:01:45 PM

spad4mebaby

Posts: 65
Joined: 8/14/2007
From: Bull Head, AZ, USA
Status: offline

I keep trying to come here for the SK engines.

I NEEDED TO POST SOMETHING HERE SO tHIS POST IS NOT IN ORDER.

Turk1 I would like to propose that an Sk 50 has a solid aluminum piston moving up and down in the crome plated brass liner. On the top of this setup is a small controlled explosion. Which heats up the top of the crome plated brass liner, and the alumilmum piston. Aluminum Brass and Chrome is supposed to be the best combination of materials for an air cooled alchocol burning engine. They work as one unit.

The pinch in a Sk50 is solid metal to metal which needs the uneven-heating of the top of the cylinder to get round. The pinch is done on purpose to make the engine last longer,make power seal better.

On a ringed engine the piston is a much looser fit. NOT touching the cylinder wall. But relying on the piston ring to seal. which should be the major thing touching the liner.
The pinch of an SK80 means the ring is loose on the bottom of the stroke and tight on the top of the stroke.
You may feel less resistance when turning the ringed engine over. But the piston ring is being compressed and loosened with every revolution.

Not following the break in instructions will probably shorten the life of the rings.

< Message edited by spad4mebaby -- 10/31/2007 11:25:45 PM >

(in reply to OUTCAST)

Post #: 453

RE: SK ENGINES - 10/24/2007 12:45:38 AM

rsad

Posts: 19
Joined: 11/22/2004
From: Westport, MA, USA
Status: offline

Just wanted to post a picture of my Robinhood 80 with the 90 on it. This has been a great airplane to try out engines with. That's an AstroFlight Porterfield Collegiate next to it.

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< Message edited by rsad -- 10/24/2007 12:48:09 AM >

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Post #: 454

RE: SK ENGINES - 10/24/2007 2:52:39 AM

XJet

Posts: 3462
Joined: 3/31/2003
From: Tokoroa, NEW ZEALAND
Status: offline

quote:

ORIGINAL: OUTCAST
Sorry I bow to the guru of nitro.

Gosh, I'm flattered at such a high accolade -- that is what you meant isn't it? :-)

quote:

I don't know whats wrong with me, I should have surmised you would know everything there is to know, far more than the factory that makes it

Gosh, let's see -- it's an engine made of very conventional materials (hyper-eutectic aluminum alloy, chromed brass, steel, etc) and there's no "magic metalurgy" involved so there is absolutely *no* reason why the basic laws of physics and engineering shouldn't apply to the SK -- hence there is similarly no reason to treat it any differently to your average ringed ABC engine during break-in. If SK knew as much as some people claim they do we wouldn't see their engines getting burnt up from faulty carbs and designs that (supposedly) won't even keep running if the prop is too small. We also would not have seen those God-awful TS engines that they made earlier.

quote:

, and still managed to get another plug in for TT

PLug for TT? Hell, the "frame of reference" on that airframe was the previous engine -- which happened to be a TT61. I'm sure most folks would like to know how the SK90 compares to other engines -- wouildn't they?

quote:

Outstanding work XJet, keep it up I cant wait for your next episode.

No problems -- I try not to disappoint my most avid fans :-)

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(in reply to OUTCAST)

Post #: 455

RE: SK ENGINES - 10/24/2007 3:02:10 AM

XJet

Posts: 3462
Joined: 3/31/2003
From: Tokoroa, NEW ZEALAND
Status: offline

quote:

ORIGINAL: spad4mebaby

I keep trying to come here for the SK engines. NOT the Xjet commedy hour.
Xjet are you a paid blogger, AKA Mickey$oft team 99, Scoble?
I believe you have all-ready destroyed the poor SK-50 you called supid tight. Is that is why you moved to the 90? What did that take about three weeks.
Do you work for P*ak Hobbies?
Why dont you just return the defective engines?

You guys crack me up!

Someone comes along with an objective assessment of the SK50 and SK90 and, just because I don't fall into line and say "it's the best engine ever, ever, ever at any price" -- I get castigated.

You also make all sorts of ridiculous allegations -- how do you know I "destroyed the poor SK-50"???

It still turns 14KRPMs on a 10.5x8 prop with just 5% nitro -- what's *destroyed* about that?

If you have an SK50 (do you?) how many RPMs can *your* engine do on that prop? Oh what?

I'm sorry that it's not as powerful as a TT or OS 46 but that's simply the fact of the matter. I'm sorry that it was ridiculously tight out of the box -- but again, that's just the facts of the matter and nothing *I* could do will change that.

And why ask if I work for P*ak Hobbies?

What on earth does that have to do with it?

Who said the engines were defective? All I did was point out that the SK50 is a cheap engine with a really badly matched exhaust system that tends to severely limit its performance on smaller props of the type usually recommended for a .46/50 sized motor. Replace that crappy exhaust with something decent and you get much better performance. It strikes me however, that rather than invest in a decent redesign of their exhaust, SK just chose to say "run big props" so as to avoid users encountering this design flaw.

As for the 90, I said it was a great-value little engine and that I'd be buying more. How does this (obviously) offend you?

Obviously there are some browsing this thread who really need to get in touch with reality :-)

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Post #: 456

RE: SK ENGINES - 10/24/2007 3:13:00 AM

XJet

Posts: 3462
Joined: 3/31/2003
From: Tokoroa, NEW ZEALAND
Status: offline

quote:

ORIGINAL: Harry Lagman

XJet,

That engine seems to carburate and generally run very sweetly. Analysing the frequency, I get about 9600-9800 rpm on the take-off roll, which seems a bit lower than a typical GMS .76 (a little over 10K with that prop).

Do you guys ever get a calm day down there? That's the second "Shrieking Winds Of Tokoroa" video I've seen now.

yep, that was easily 400-500 RPMs rich of peak so there's a bit more to come from that engine. That was also using regular Coolpower Pink oil at 18% (for the break-in) so there were a few hundred RPMs further improvement when we switched to the 12% Ester-synth/castor brew.

And what's this about wind?

Haven't you guys north of the Bombays had a bit of wind too? We get bored as hell flying on calm days now -- where's the challenge :-)

You guys up for some RC combat -- our CNC foam cutter is almost ready to go and we'll be cutting cores by the dozen for RC combat wings. Hamilton is signing up -- how about you?

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Post #: 457

RE: SK ENGINES - 10/24/2007 4:04:03 AM

rustypep

Posts: 342
Joined: 9/12/2004
From: Powell, OH, USA
Status: offline

I have more than 50 flights on my SK 50 mostly swinging a 12x5 and I am still a happy customer. The engine has great, vertical stump pulling power with that prop. It also sips the fuel even with all the vertical action. I also own a TT 46. The only drastic difference in my experience is that TT broke in much quicker. The engines are designed for different applications. I run an 11x6 (pretty sure) on the TT and a 12x5 on SK and they both get the desired result. More speed on one and more stump pulling power on the other. I have never had a dead stick on either one that wasn't self induced. If you are propping an SK to turn max RPM than you might as well buy a TT and find another thread.

< Message edited by rustypep -- 10/24/2007 4:07:01 AM >

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Post #: 458

RE: SK ENGINES - 10/24/2007 6:50:42 AM

XJet

Posts: 3462
Joined: 3/31/2003
From: Tokoroa, NEW ZEALAND
Status: offline

quote:

ORIGINAL: rustypep
I have more than 50 flights on my SK 50 mostly swinging a 12x5 and I am still a happy customer.

That's great news, I'm pleased for you.

quote:

The only drastic difference in my experience is that TT broke in much quicker.

Generally a sign that it was machined to closer tolerances but that's reflected in the price.

quote:

The engines are designed for different applications. I run an 11x6 (pretty sure) on the TT and a 12x5 on SK and they both get the desired result. More speed on one and more stump pulling power on the other. I have never had a dead stick on either one that wasn't self induced.

Yep, that's fine too -- I've got no problem with that -- with its standard exhaust, the SK does perform better at lower RPMs than at higher RPMs -- it's just a shame that its full potential is reduced by that exhaust. Throw a decent muffler on and it'll still turn large props but also turn small ones -- I can't see how that's a bad thing.

quote:

If you are propping an SK to turn max RPM than you might as well buy a TT and find another thread.

You fanboys continue to amaze me.

If I don't agree with you that the SK is the best thing since sliced bread I'm invited to leave the thread.

A closed mind gathers no knowledge -- but ignorance is bliss so I'll leave you to it.

It's starting to look as if the very *worst* aspect of the SK engines are the parochial owners who frequent this thread. Perhaps the box should come with a warning "caution, buying this engine may compromise your ability to think and reason rationally"

Let he who questions the SK ultimate superiority above all else be cast out and let he who dares bring objective facts and first-hand unbiased observations into the discussion be scorned and ridiculed for his lack of worship at the altar of SK (ROTFL).

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Post #: 459

RE: SK ENGINES - 10/24/2007 8:17:12 AM

fiery

Posts: 1010
Joined: 2/2/2002
From: Hervey Bay Queensland, AUSTRALIA
Status: offline

Gents

Can we quit the carping and get back on track? We don't want the moderator's locking this thread up.

I for one look forward to seeing more user reports, findings and tips on the SK line.

Regards to all

fiery

(in reply to XJet)

Post #: 460

RE: SK ENGINES - 10/24/2007 8:27:29 AM

spad4mebaby

Posts: 65
Joined: 8/14/2007
From: Bull Head, AZ, USA
Status: offline

I am thinking of getting a SK-90 instead of 2 Sk's

< Message edited by spad4mebaby -- 10/24/2007 8:43:57 AM >

(in reply to XJet)

Post #: 461

RE: SK ENGINES - 10/24/2007 9:07:49 AM

Turk1

Posts: 645
Joined: 10/8/2004
From: Istanbul, TURKEY
Status: offline

quote:

ORIGINAL: XJet

As I suggested earlier -- maybe these ones are ported differently (although I doubt it). It's more likely that SK (the people who brought you the atrocious Tiger Shark engines) don't realize that the exhaust system on the 50 is all-wrong and significantly compromises its performance at anything above modest RPMs.

Hi ANZAC.I want to mention that my 3 SK 50 s are all earlier Kangke origin engines and their crankase exhaust openings are flat machined on both inner sides.I have seen later engines(all from Kangke) have got oval shaped machined inner upper wall of crankase exhaust outlet openings.I think they are aware of that problem and tried to give a better relief from liner to muffler inlet.Also I can agree with you on possibly faulty muffler design despite I didnt have any experiments-tests like you.
BTW,please go on postings,I like to read your posts and have something to learn everytime.

< Message edited by Turk1 -- 10/24/2007 9:18:04 AM >

(in reply to XJet)

Post #: 462

RE: SK ENGINES - 10/24/2007 10:05:14 AM

XJet

Posts: 3462
Joined: 3/31/2003
From: Tokoroa, NEW ZEALAND
Status: offline

quote:

ORIGINAL: Turk1
Hi ANZAC.I want to mention that my 3 SK 50 s are all earlier Kangke origin engines and their crankase exhaust openings are flat machined on both inner sides.I have seen later engines(all from Kangke) have got oval shaped machined inner upper wall of crankase exhaust outlet openings.I think they are aware of that problem and tried to give a better relief from liner to muffler inlet.Also I can agree with you on possibly faulty muffler design despite I didnt have any experiments-tests like you.
BTW,please go on postings,I like to read your posts and have something to learn everytime.

Thanks for the info Turk.

I'm going to tune the mousse-can setup this coming weekend and see if I can get some more power out of the 50 (not that it's too bad now anyway).

I've also got some more props coming (larger ones) to compare the performance across the rev-range.

I'm also going to load-up the 90 and do some side-by-side comparisons with the ST90 (probably this engine's closest rival in the USA).

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(in reply to Turk1)