Oscillating engine problem - not turning all the way

[student123]

My novice build of the littlemachineshop oscillating engine resumes…

http://littlemachineshop.com/Projects/OscillatingEngine.php

piston brass, a paper gasket , all else aliminium
testing on compressed air.

The engine turns only part of the way.

Heres a link to a vid of it:


http://img26.imageshack.us/img26/4315/d4m.mp4

sorry no sound on my camera

and a couple of pics:

First question : is what I'm doing (hand turning) safe ? - am I risking getting trapped fingers etc? I feel reasonably safe, otherwise wouldnt have tried it, but just to check.
If unsafe, then how else to test it?

Second : any ideas whats wrong? I do have one suspicion , but would appreciate any advice

Mike.

 

[kjk]

Does the engine turn over freely by hand when no air is supplied? Any binding will stop the engine from running. If there is binding try to isolate the source and fix it.

Re-check your measurements. I tried an experiment where I shortened the piston/conrod of my elmer's #25 and it behaved exactly as yours is behaving now.

 

[FIXIT]

Just a stab in the dark but it looks to me that the piston is under full air pressure at the bottom of the stroke where it should be under transition to the exhaust stage
as Woodguy advises is if it rotates freely with no air then check your dimension's around the valve timing area

 

[SBWHART]

Could be the crank pin out of square this will pull the cylinder away from the port face losing air, at top or bottom on the stroke depending on which way its out of square.

Stew

 

[student123]

Thanks guys
Problem solved : now running!
Sorry but not exactly sure what caused the problem : some fiddling & oiling
& now going!

Mike

 

[kjk]

Congratulations. Now let's have the video.

 

[student123]

Woodguy

Sorry, should have linked, already posted over on finished projects:

http://www.homemodelenginemachinist.com/index.php?topic=11510.0

Excited at present, heaps of photos to sort thru to pick a few out,
& of course thanks to be given out. Intend to get to it soon.

Mike

 

[AllThumbs]

Nice job.

My guess is with the light aluminum flywheel it just needed a little bigger push (spin) to start it.

 

[student123]

Allthumbs

Thanks for the reply.

Your guess may be a good one. I've since thought about what I did to get it going.
In the above vid it went from 10 o'clock to 6 o'clock (anticlockwise!) i.e. about 120 degrees.
There had been some binding, so I dismantled , felt around for the cause of binding - (the flywheel felt a little tightly screwed toward the upright), oiled, put it back together this time with the flywheel slightly less tight against the upright.

Then it went round maybe 180 degrees. So intuitively I started to spin it & away it went.