MJD

My Feedback: (1)

I finally ran my OPS .15 today. I've been looking forward to running it for a long time, and I was having a bad day for myriad reasons.. so it seemed like a tonic for Eeyorian spirits. Fitted it up to my PSP test stand - I like this thing, it hold anything. I wonder if it is the first one they made whose first engine was a pulsejet..? Anyhow, I had a pair of Graupner Speed 6"x5.5" props picked out for it, and as per proper form - and ILJ's reminder - trimmed one down to let it spin up tp flight rpm on the ground in a rich two stroke on the pipe. It ended up at 5.25" diameter by the time I cleaned it up and balanced it, and looks stupid on the front of the engine with only the spinner backplate fitted. Don't have the right thread spinner nut yet.

So armed with flight box, some castor-added 15% fuel and high hopes, I carried the affair out back to the bleachers and got acquainted with the engine. P- me off though - I can't find my tach since the last flight session. So, no pipe tuning today but a couple of runs for fun seemed in order. I fueled up, warmed up the head, pulled it through a couple of times then hooked up the plug. One tap with the starter and it was off in a clean fast idle, so I let it warm for a few seconds as I got rearranged behind the stand, then started advancing the throttle while tweaking the high speed needle and alternately pinching the line to keep it going, coming in from very rich. No sweat, up on the pipe in a smoky but full two cycle, and ran like a song. After 10-15 seconds, I richened off a bit and it responded with a break, then back up and on again - I then tested the throttle response and it followed the movement of the arm as fast as I moved it - instant up and down without a burble or hiccup, and straight into a strong rich two cycle wham time after time. Cool. I promise to get tach readings as soon as I find the bloody thing or borrow/buy another one. But suffice to say I am very impressed with this little engine, it runs like an OPS - go figure. And still squeaky tight at top after 3 short runs - I warmed the head every time. I used the starter only on the first start - aftr that a half-hearted flip with the chicken stick and off it went. no fuss at all.

This is the first time I've run a Perry carb - wow, it works great, and adjusted very easily and predictably. The low end dial was stupid easy to tweak at maybe 1/4 throttle, up and down a couple of times and a pinch test to verify, done. Set the top end, done. Instantaneous throttle response, really, just ZING - purrrrr - ZING and spot on the top end mixture. I imagine the near total lack of inertia from that silly little prop helps the spool-up time.. . 5.25" x 5.5" prop on a .15, it just sounds silly.

Well, actually, it sounds sweet.. [>:]

MJD

combatpigg

My Feedback: (3)

MJD, that's the way to break in an engine, just like a weight lifter coming back from a muscle pull. I don't think 99% of the hobbyists understand this, they would rather overload the engine to keep the rpms down.

HighPlains

My Feedback: (1)

I use to use a wood 10/6 cut down to a 6/6 on my F1 pylon 40's for inital break-in. Ran an easy rich two cycle at 25K+ on the first run or the engines were tore down.

MJD

My Feedback: (1)

Reps man, reps - exactly. Light load = happy new two stroke. The folks you refer to are the same guys that write to an engine forum for help after scaring themselves with a .46 on a 9" sport prop..

It's also the way to treat ringed engines too, with the exception of mixture setting. Light load, rich rich and let 'em spin.

Now I worry about how fast it will pull that SWR delta.. more correctly, I worry about the test pilot.

MJD

daven

My Feedback: (1)

Sounds good, very similar to how many of us break in our racing motors.