daven

My Feedback: (1)

I have a Nelson q40 engine that has always stopped at TDC after the fuel line is pinched. This made it real easy to set the prop at 9 and 3 and the prop would be safe on landing. In Florida over the weekend, after about 7 heats, the dang prop started stopping just shy of compression or in the 12 and 6 position. I got lucky on the first 2 landings, but broke a good wood prop the 3rd time.

Where does the prop normally stop, and anyone have any ideas why this engine just suddenly started stopping in the wrong place?

I don't have many good wood props, and I wasn't too happy about wrecking that prop. Any help would be appreciated.

Thanks,

DHG

My Feedback: (7)

Dave,

Was the "fit" loose and squishy? I can't remember ever having one that went all the way up to TDC. Normally it stops running and the prop bounces back and forth a couple times, then the windmill action pushes it a little way into compression, where it finds equilibrium and stays put.

At least, I think that's what's happening.

Maybe this one broke in a little more and now it's going past TDC ... or maybe it got warm, the piston grew a little, and it's got a tighter fit. Dunno.

Pink Punk

bl10

Dave:
It’s been my experience that really tight engines tend to stop at top dead center most of the time and well broken in ones tend to cycle through TDC and stop just coming up on compression. All my best well broken in engines usually will not stay at TDC if I manually put them there. They snap off compression one way or the other. So I set my prop so it’s not vertical no matter which of the two ways it stops. Breaking wood props is the reason I am in favor of the black prop. I know at the PHX JR Bruce Coffey and the 3 or four guys running his props went through something like 20 props. Way to much work for me. I know several guys who almost never break a wood prop no matter where it stops but they land much smoother than I do.



Good Luck
Barry

daven

My Feedback: (1)

Considering this is my oldest q40 motor, and the one I have used at every race for the past 4 years, I would have hoped it was broken in prior to this weekend. It would stick tight at TDC after every run prior to this past weekend. Its set up with pretty high spacing (.196 and .016), maybe its time to lower the sleeve a tad. Its always been a very strong motor, but it just didn't seem that fast this weekend compared to previous races. I will play with it, thanks for the tips, I guess I had a freak engine.

luv to race

My Feedback: (1)

DN,

Find the nearest trash can.... and chuck that fishing weight in th bottom of it... JK

Get that other tach of yours fixed, leave that other tach on the bench at home. Start taching it each time you go to race a heat. Expecially when you are switching props between rounds. I'm going to sit down and crank out some wood props....I'll keep you in mind and try to bring you a couple for the Nats.

*** I seem to be missing big pieces of my FAI wing.... fly's pretty bad with no ailerons.

smoke

Bill Vargas

My Feedback: (5)

DN, I always set my prop to the index groove on the spinner backplate. Could be possible that your backplate is worn out. I had the same thing happen to me,,, changed out the backplate and the prop stopped moving.


BV