049 test stand dont's

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- Tim Wescott
  
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posted
15 years ago

Sat, Jun 28, 2008 3:00 AM

Got a Cox reed valve 049 engine going today, with a Davis head.

For a motor stand I'm using a Tatone stand with a piece of 1/8" angle iron on which the engine is bolted.

Don't do this, unless you want some practical education in resonances. At the 'bad frequency' (which was just a bit lower than what the engine really wanted to do) I could see the cylinder moving through a 1/4" long arc.

Very disconcerting.

But I could damp it out by hanging on to the engine, so I verified that it runs (and smells) normally for a little Diesel conversion, and I have the compression and mixture at a good setting to go on a plane.

Tomorrow I go flying.

Sometime soon I go get some nice thick T-bar and make a new test stand adapter for 049s!

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- Martin X. Moleski, SJ
  
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posted
15 years ago

Sat, Jun 28, 2008 3:23 AM

On Fri, 27 Jun 2008 20:00:23 -0700, Tim Wescott wrote in :

Gives me the shivers just thinking about it.

Sounds like the conversion worked and you and the engine survived the test run. All's well that ends well!

Marty

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- MJKolodziej
  
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posted
15 years ago

Sat, Jun 28, 2008 3:28 AM

Cool! How did you start it? Power or fingers? Fuel tank attached or apart?

mk

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- Morgans
  
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posted
15 years ago

Sat, Jun 28, 2008 4:10 AM

"Tim Wescott" wrote

Another thing you can do, until the engine sizes get really big (big enough to move a concrete block ) is to mount the stand to a piece of 2 X 8 (either using the steel between the engine mount and the wood, or not) and mount the whole thing on a 8 X 8 X 16" concrete block.

The block adds enough mass to purty much guarantee that the resonance will be too low to matter, and the wood helps even more to dampen out any small, fast vibrations.

That, plus you don't need to do anything except set your block out in the yard, and crank up the engine.

Like I said, until you go with a really big gasser, it ain't goin' nowhere!