Re: 049 test stand dont's

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.

-- 

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