Inverting a Four Stroke? - RCCanada - Canada Radio Controlled Hobby Forum
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Old 06-25-2007, 09:49 AM   #1
supercub Man
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Inverting a Four Stroke?

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I would like to invert an OS FS 52S four stroke engine in the little Unionville Hobbies Otter I'm building. My friends tell me this is a bad idea as FS's do not like to be inverted! I am trying to totally enclose the engine in the cowl. An upright installation would stick out the top while sideways would also require cutting up the cowl. Any one have any thoughts on this? I haven't had a FS before so I'm a "newby" in this area! Otherwise I will go to an OS 46FS.
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Old 06-25-2007, 10:40 AM   #2
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Inverted Four Strokes

I have several four strokes inverted in my scale aircraft, and have no problems at all with them, althought they are 120's and larger. I do however use a on board glow system on the plug that kicks in when you are at low throttle. This also eleminates the need to attach a battery when starting. It's very impressive, you set up to start, and just put the starter on the engine.
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Old 06-25-2007, 10:53 AM   #3
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saito 1.80 in a 73" yak

engine is inverted and other than the odd hiccup due to tank location being quite far behind the engine and flying aggressive 3d no troubles even on startup just a bugger to get glow starter on plug when it's hanging but i like it so far!!
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Old 06-25-2007, 11:28 AM   #4
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I would think if there was a problem with them inverted then flying upside down would also be a problem.

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Old 06-25-2007, 11:39 AM   #5
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I have a few Saitos inverted from a .65, 72, 80, 91, 120, to a 1.50 and they all work fine. I have most of them slightly off the perpendicular so the so called fuel doesn't pool on the plug. you can also more center the exhaust under your cowl if you rotate the motor slightly.
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Old 06-25-2007, 11:44 AM   #6
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Otters don't usually fly upside down :P

Inverted mounting is okay, but you pretty much need an onboard glow system...if you could move the cylinder a bit so it is in the 5 o'clock, or 7 o'clock postition that is even better as the glow plug is not the lowest part of the cylinder. The main thing to watch out for is that the carb would be lower, so the fuel tank hight becomes more critical.........
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Old 06-25-2007, 01:10 PM   #7
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Never had to resort to running an onboard glow with any inverted 4 stroke. Saitos, Os, Thundertiger or YS. If set up properly there should be no need to have to run any type of onboard glow unless you wish it for easy starting.

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Old 06-25-2007, 02:16 PM   #8
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My Unionville 6' Otter has an OS52 FS mounted inverted and it runs and idles fine on 5% fuel without the onboard glow, which I use for starting only. I use an extension pipe which is a snug fit on the exhaust in lieu of the muffler and no one complains of the extra 1db of noise. The engine is a close fit within the cowl with the rocker box residing in the air scoop.
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Old 06-25-2007, 03:12 PM   #9
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I've had a Saito 56 mounted inverted on different planes, no problems whatsoever.

I've also got a Saito 80 mounted inverted, again no problems.

Both engines don't have an on-board glow set up, never needed it.

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Old 06-25-2007, 03:29 PM   #10
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Same here. Closest I can come to this setup is an OS .40 inverted in a unionville Tigermoth, no onboard glow.
Performed well for years with no hiccups and I understand she is still performing well for the new owner.

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