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!
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
On Fri, 27 Jun 2008 20:00:23 -0700, Tim Wescott <t...@seemywebsite.com> wrote in <B6-dnQFFFODdNPjVnZ2dnUVZ_uudn...@web-ster.com>:
>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. ...
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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> 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!
> 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?
> 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.
Another thing you can do, until the engine sizes get really big (big enough to move a concrete block <g>) 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! <G> -- Jim in NC
Morgans wrote: > "Tim Wescott" <t...@seemywebsite.com> wrote
>> 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.
> Another thing you can do, until the engine sizes get really big (big enough > to move a concrete block <g>) 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! > <G>
I'm pretty sure this resonance was the angle iron flexing in the stand, which wouldn't change much if it were on a concrete block.
I'll know more after I get the 'right' adapter built.
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
>> 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!
>> 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.
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
>>> 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!
>>> 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.
>>>> 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!
>>>> 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.
It still is. Cheap, too, as long as the bucket-o-engines holds out.
I haven't done it for a while, so I expect to get dizzy -- this is the driver behind the small tank, and may also lead to some BB's or bits of Teflon in said tank until my middle ears adjust.
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
> I'm pretty sure this resonance was the angle iron flexing in the stand, > which wouldn't change much if it were on a concrete block.
> I'll know more after I get the 'right' adapter built.
Is the stand made of the said angle iron, or is the mount mounted to the angle iron?
I pictured the angle iron mounted in direct contact to the wood, for its whole length, and on both legs, just to give the mount some real firm footing to mount onto. Perhaps even some construction adhesive along with some screws, making the angle have direct contact in it's entirety. -- Jim in NC
> Got a Cox reed valve 049 engine going today, with a Davis head.
About to run my Surestart engine tomorrow.
> For a motor stand I'm using a Tatone stand with a piece of 1/8" angle iron > on which the engine is bolted.
I'm using a lump of pine that was being used to make engine mounts for a Gremlin.
> 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.
Probably not good for the mount or the engine but it would take some experimentation to prove it.
> 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 h
