Brand new RCV58-CD, feels like having slack on cranckshaft (Full Version)

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hmeijdam -> Brand new RCV58-CD, feels like having slack on cranckshaft (1/10/2011 8:52 PM)

Hello All,

After a "pause" of 30 years I started modelflying again last year. I put my trainer through its excercises and enjoyed it a ton!. For this year I opt for a nice 4-stroke in the nose of my plane. After researching the internet I decided that the elegance of the RCV engine is just what I want.

I received my engine today from Weston in the UK and while examining the engine I noticed that it feels like the engine has slack inside. I can turn the propdriver about 3 degrees left-right without feeling any resistance from the engine. The rotating valve does not move then. At both ends I hear and feel a soft "clunck" and then the valve starts to rotate. Like a lot of slack in the gears between cranckshaft and rotating valve. But I would expect at least to feel resistance from a brand new piston in the cylinder, but to be honest, I dont feel that.

If I compare the feeling with a 2 stroke engine, it feels like a 2 stroke with a completely worn out big-end.

Now my newbee question is ofcourse "is this normal and the case with all RCV 58 CD engines? Or do you fellow RCV owners don't feel this in your engine, which would mean I better not try to start the engine.

Best regards,
Hans Meijdam
The Netherlands



N99JH -> RE: Brand new RCV58-CD, feels like having slack on cranckshaft (1/10/2011 10:26 PM)

Hans

I am no expert on RCV but have been running my 120SP extensively lately and have the same "Slack". I think that what you feel is actually the Backlash which is the correct engineering term for the amount of controlled play between the gear teeth. Since the rotating barrell is geared 1:2 in the case of the CD, it feels like a lot of "Slack" but is actually normal. My 58CD feels about the same. I would suggest that you go ahead and break it in, you will probably love it.

Joshua



mboland -> RE: Brand new RCV58-CD, feels like having slack on cranckshaft (1/11/2011 2:54 AM)

I have just checked the two 58CD's I have and each has about 1deg of 'slop' evident when cold.

Both engines have been sitting for some time and both have had a lot of running in the past.

3deg does sound a bit much.

Have you contacted the suppliers. That would be the place to start.
RCV's customer support was unparalleled and I have heard Weston UK are just as good.
An email to them personally might get you some good advice on whether it is OK to run the engine.



hmeijdam -> RE: Brand new RCV58-CD, feels like having slack on cranckshaft (1/11/2011 8:12 AM)

 Hi all,

Thanks for your prompt responses and taking the effort to compare with your engines. I did mail to Weston-UK yesterday as well, so I will wait for their response. I am intending to start-up the engine over the next weekend, for some running-in time. I can imagine that the engine needs backlash between the teeth of the 2:1 gear. I was just wondering what is the right amount of backlash. Too little and the teeth will be grinded. Too much and the teeth will be hammered. I found an arc in the meantime, so that I can measure the amount of free rotation of the prop driver as the 3 degrees was my gut-feeling estimate.

Edit:  in the meantime Alan from Weston-UK responded to me as follows:

This is quite normal because with the CD range you do not run a very tight gear mesh. The motor will run fine, do not worry, start it up, you will be impressed!

So I will start the running-in as per the instructions in the manual over the weekend.

Thanks again,

Hans



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