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Vibration level on a 60-SP???

Old 08-30-2008, 09:20 PM
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N1EDM
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Default Vibration level on a 60-SP???

I'm planning on a pre-WWI scale model. The cowling is tight, and I didn't want a cylinder head to show through.

To that end, I started wondering if Santa might bring me a 60-SP, but then I had another thought.

Airplanes of this vintage were often frail with minimal construction and vibration is going to be a major issue for an airframe such as this (planning a 6-ft wingspan). I was wondering what the vibration levels were on a SP-series engine compared to something with a piston that is perpendicular to the crankshaft, such as the RCV58-CD?

Does anyone have any comments/experience/thoughts on how this engine performs, vibration-wise?

Thanks,

Bob
Old 08-31-2008, 03:09 PM
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Default RE: Vibration level on a 60-SP???

in a word - extreme.
The very design of the SP means excessive vibration. I would imagine it could rip a light airframe apart without too much trouble.
Even worse, it is a twisting vibration.
On the other hand the CD motors are rather docile.
Old 09-01-2008, 06:53 AM
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Default RE: Vibration level on a 60-SP???

Thanks for the comment, mboland. Do you have one yourself, or have you actually seen one in action? I figured that with the back & forth motion of the piston in the SP, there would be some shake... but wasn't sure quite how much. And, that Blackburn Monoplane fuse will be very fragile...

I'm re-thinking about the CD. Depending on the comments that I get here, I might just ask Santa for a new CD instead of a SP.
Old 09-01-2008, 02:18 PM
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Default RE: Vibration level on a 60-SP???

I currently have a 60SP I purchased from a clubmate, a couple of 58CD's and did have 3 120SP's which gave so much trouble RCV took them back (after 2 failed).

It's not so much the forward and back piston that causes the vibration, it's the twist as each power stroke spins up the heavy liner/valve/prop driver. Even in a strong model you have to beef up the firewall (and I would suggest all the way back to the wing seat) to cope with the twisting stresses. Mounting an SP requires that you sandwich the firewall between the special mounting plate provided and the engine.

The CD's on the other hand are probably one of the smoothest 4 strokes I have tried, but can produce some really strange gear noises.
Old 09-01-2008, 04:49 PM
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Default RE: Vibration level on a 60-SP???

Hi mboland...

Thanks, the 'strange' gear noises might just add a bit to the plane overall. Have you run these inverted? If so, how have they been compared to running a 2S or a standard 4S inverted...

How would you compare the CD smoothness to that of a good quality 'standard' 4S like Saito (which I'm familiar with)?

Bob
Old 09-01-2008, 05:57 PM
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Default RE: Vibration level on a 60-SP???

The 58CD's are generally run inverted as it seems the only way with scale to keep it all in the cowl.
I have found no difference in running them upright, side ways, or inverted. They seem very tolerant of attitude.

I also run a few Saito's (72's and 125's) and would say the CD has a bit less vibration, probably due to it's mass and the heavy liner/valve rotation being perpendicular to the crank.

Do be aware that they are quite a bit heavier than other engines which may or may not be a good thing (heavy engine is better than adding lead).
Old 09-01-2008, 08:51 PM
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Default RE: Vibration level on a 60-SP???

Thanks, that weight might be a consideration. I have a friend who built one years ago (1/4 scale, not 1/6 scale like mine will be) and he had a nose weight problem. I'll have to check the difference in weight between the RCV and a Saito .82. I'd sure like to find a way to use that RCV though...

Thanks a lot,

Bob

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