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Engine basics => Engine set up tips => Topic started by: frank mccune on April 02, 2020, 08:30:38 AM
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Hi All:
Are fins on the cylinder head necessary? I have engines with none, with only half of the head covered with fins and heads with no fins. I was informed that a Stunt engine must have fins to run well. This seems counter intuitive as the Stunt engine may run the coolest of all engines.
Thoughts/comments?
Be safe and be well,
Frank McCune
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Engines with cast iron piston can be happy with fins eventually.
All engines with aluminum pistons do not need fins at cylinderhead at all.
With healthy parameters (12-15° free outlet before scavenging begins), most engines are over-cooled.
To keep them warm, comes the free outlet down to 7-8° and super tight silencer, etc.
This is good to get from a .76 - .80 engine same power (same torque) like a .51 :)
I never forget our first experience 30 years before, when we tied a canvas ribbon around a commercial ex-RC engine's head, it looked like a samurai, and ran like a Fox-35... :)
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YES the fins are NEEDED and are a good thing, many engines ruined by people milling the fins off, It is easy to make them hotter, HARD to cool down without fins, You can also make more stable power with fins
Randy
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YES the fins are NEEDED and are a good thing, many engines ruined by people milling the fins off,
But they saved a gram and a half, so still better. No?
Brett
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Does anyone have an idea why the HP .40 Silverstar has no fins?
Always wondered , John L.
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Does anyone have an idea why the HP .40 Silverstar has no fins?
Always wondered , John L.
That is one of the several engine I ran test on, I cut fins into the stock head, and use an old head with fins, and the no fin head, The engine behaved much better with fins, It showed runaway and slow, too slow cycling with the no fin head, So many of them were RC versions, and those ran 2 cycle, so not a problem with RC application.
Other engines I tested showed the same, cycling was much quicker with the fin head engine, especially the ST 46 and 60
Randy
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Does anyone have an idea why the HP .40 Silverstar has no fins?
Always wondered , John L.
Dear John, Mr. Paul Bugl was one of the really most talented engine designers. (Sorrowfully he passed 'round his early fifties. ) He really did know, what he was doing.
Well, I used HP 40's from 1983 up till 1999, and one model of mine still exist with HP.
As HP forties was made originally for R/C, I made some mods, as follows:
-sleeve lower by 0.8 ÷ 1.0 mm
-inlet closed from 190-200°s to 170° (only by Gold Cup: Silver Star was not so extremely open)
-we used the black plain cylinderhead, or machined off the fins of GC head's fins...
-and I collected the original nozzle-type carburettor from the oldschool friends, who stubbornly bound theirself to the spraybar-version.
Our engines were absolutely in contest with the ST-46. We used 12x4 Tornado or 12x6 Modela (wide wood) props mostly.
Istvan
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I've been told to drop the liner ...
Thanks.
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The HP Gold Cup 40 had fins. Didn't they come out before the Silver series?
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The original Enya 61CX (ringed with head button) has fins but the later ABN (red head and no button) has no fins.
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A billet aluminum head is quite adequate to absorb and dissipate heat. Cooling fins just make it look more like an engine. Look at the Fox 35, do you think those little nubs on top really do much?
Motorman 8)
NOT in stunt, where people want to cycle quickly, R/C or racing where your running a constant 2 cycle, is quite different than Stunt runs, I made deep fin heads for the FOX 35 back in the 1970s, They works much better, and the FOX 35 would cycle faster , you could get more power out of it, and slow returns from LEAN was improved, When I designed the Smith Fox hemi head, that is the reason it has more fins and deeper fins, Most of them also had extra cooling fins around the circumference , These work better, a lot better. AS I wrote earlier, I also test much the same on many other engines, More area to dispel heat, IS almost 99 % of the time better. Shaving the fins off is mostly 99% worse !
Randy
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Just one detail does not make it right🙃. L
Oh hell NO ! WAY TOO MANY FINS , you get right back on those machines and trim all the fins off that motor !!! mw~ mw~ LL~ LL~ LL~ ~> n1 ~> ~> ~> ~> ~>
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Oh hell NO ! WAY TOO MANY FINS , you get right back on those machines and trim all the fins off that motor !!! mw~ mw~ LL~ LL~ LL~ ~> n1 ~> ~> ~> ~> ~>
I have a file right here, let me take care of that for you...
Brett