Re: 049 test stand dont's

Tim Wescott wrote:
> MJKolodziej wrote:
> 
>> "Tim Wescott" <tim@[EMAIL PROTECTED]
> wrote in message 
>> news:B6-dnQFFFODdNPjVnZ2dnUVZ_uudnZ2d@[EMAIL PROTECTED]
>>
>>> 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!
>>>
>>> -- 
>>>
>>> Tim Wescott
>>> Wescott Design Services
>>> http://www.wescottdesign.com
>>>
>>> Do you need to implement control loops in software?
>>> "Applied Control Theory for Embedded Systems" gives you just what it 
>>> says.
>>> See details at http://www.wescottdesign.com/actfes/actfes.html
>>
>>
>> Cool!
>> How did you start it? Power or fingers?  Fuel tank attached or apart?
>>
> It's got a Babe-Bee tank.  Unfortunately it's going onto a plane that's 
> got a Golden Bee right now, and will need a spacer to get the prop out 
> far enough to clear the cowl.  So, maybe I fly Sunday.
> 
> Cox 049s without mods don't do well being started with an electric 
> starter.  It can be done, but the prop drive and crank case are both 
> aluminum, so they get chewed up pretty quick.  There were supposed to be

> some marine engines that had bronze or brass prop drives which are 
> supposed to work better.
> 
> I've been thinking of taking one of my chewed-up crank cases (guess how 
> they got that way!) and fitting a steel collar at the end of the crank 
> case to run against the prop drive; dunno if I'd go to the trouble of 
> turning out a brass prop drive.
> 
> At any rate, this one starts with a generous prime and a few healthy 
> flips by hand.  I had been using a chicken stick, but did you know that 
> rubber turns to black gunk in the presence of diesel oil and ether? 
> Fingers don't...
> 
> The big challenge was getting the needle and compression adjustments 
> sorted out the first time; now it should go without adjustment.  I need 
> a tach, but it's turning a 7-4 prop 'good and fast' -- it sounds barely 
> slower than a glo 049 with a 6-4 prop, so it should pull my slightly 
> oversized control line job around pretty well.
> 


Good Gawd!  You mean someone actually still flies .049 Ukies?  I have 
done that since I was a kid.  It WAS fun though.

Jim