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2 strokes Oil and a Clutch

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knowvne(at)aol.com
Guest

Posted: Wed Apr 02, 2008 6:44 pm Post subject: 2 strokes Oil and a Clutch

Keep in mind that 503s that have oil injection,Â 

  vary the amount of oil ingested depending on throttle applied at the time.

  

 

  

 

  GaryÂ 

  QUESTION FOR YA...

  

 

  What about Long steep dives that Wind Mill the Prop and Raise Motor RPMs ?

  

 

  In this situation, ARE we destroying the motor because were rapidly cooling theÂ 

  Motor whileÂ depriving it of needed oil due to a retarded throttle setting ???

  

 

  Isn't this happening with both Oil Injected and Pre Mixed systems???

  AND if this is true, Isn't this a good justification for using a Clutch on the Prop??

  

 

  

 

  

 

  Mark

  

 

  

 

  

 

  

 

  

 

  50 to 1 may be enough at full throttle,but more than needed at partial throttle.It may not be as critical as we make it An extra ounce in 5 gal doesn't seem too critical.Too much oil builds carbon,thats why oil injection is desirable.The total amount of oil used per 5 gal of gas is less than 50-1.

 

  ---

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Dana

Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA

Posted: Thu Apr 03, 2008 3:03 am Post subject: 2 strokes Oil and a Clutch

At 10:40 PM 4/2/2008, knowvne(at)aol.com wrote:



  	  Quote: 	
		  What about Long steep dives that Wind Mill the Prop and Raise Motor RPMs ?



 In this situation, ARE we destroying the motor because were rapidly cooling theÂ 

 Motor whileÂ depriving it of needed oil due to a retarded throttle setting ???



 Isn't this happening with both Oil Injected and Pre Mixed  systems???

 AND if this is true, Isn't this a good justification for using a Clutch on the Prop?? 	


 It IS a concern (for reasons of lean mixture alone regardless of oil ratio, see the article at http://curedcomposites.netfirms.com/twostroke.html ).  However, at ultralight or Kolb speeds, just how much does a reduction driven prop on a 2-stroke prop really windmill?



 -Dana

 --

  The family that shoots together..... shouldn't be messed with!    [quote][b]

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gaman(at)att.net
Guest

Posted: Thu Apr 03, 2008 4:33 am Post subject: 2 strokes Oil and a Clutch

Mark,

Possible,but my 503, which idles at 1750rpm to allow slow steep descents, has shown no ill effects in over 550 hrs.The cyl hd and exh temps are both low during steep dives with throttle at idle.Could be that a closed throttle acts like a choke under these conditions.If the throttle is only partially closed, the exh temps really go up.But as soon as I close it completely they come right down.

---

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knowvne(at)aol.com
Guest

Posted: Thu Apr 03, 2008 5:15 am Post subject: 2 strokes Oil and a Clutch

Hmmmm interesting.. 

 

  So are there advantages disadvantages to using a clutch?? Â 

  

 

  I figured they'd be helpful in reducing engine wareÂ on long steep decent's.. Â 

  You seem to be saying it's not an issue as long as you keep the throttle partially open..

  Do you premix or have an Oil Injection system on your 503?Â 

  A 503 w/ Injection was what I was considering Â just so to avoid the mixing issue

  flying XC...

  

 

  

 

  I must admit these 2 cycle system are like were dancing on the tip ofÂ 

  a needle atÂ times.. hahaha 

  

 

  

 

  

 

  Â Pros / Cons Â for Clutch on the Prop

  

 

  Pros

  Safer on the ground,Â 

  Less ware on a starter,Â 

  

 

  Cons

  More weight effecting Gross and CGÂ 

  One more thing that could fail..

  

 

  Are there others????

  

 

  Mark

  

 

  

 

  

 

  

 

  

 

  --

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lucien

Joined: 03 Jun 2007
Posts: 721
Location: santa fe, NM

Posted: Thu Apr 03, 2008 6:07 am Post subject: Re: 2 strokes Oil and a Clutch

 	  knowvne(at)aol.com wrote: 	
		  Hmmmm interesting.. 

 

  So are there advantages disadvantages to using a clutch??  

  

   Pros / Cons  for Clutch on the Prop

 

  Pros

  Safer on the ground, 

  Less ware on a starter, 

  

  Cons

  More weight effecting Gross and CG 

  One more thing that could fail..

  

 

  Are there others????

  

 

  Mark

	




Yes, some cons too but the pros vastly outweigh the cons:



- as for the weight, the overall addition is only about 3lbs, which is pretty minimal

- failure is almost a non-issue, as the rk400 is a very well made, precision unit. It's also surprisingly long wearing.



Other cons:

- engages at 2700 rpm, which may be a perfect taxiing rpm as it was on my old FS II, changes the way you taxi the plane.

- expensive sucker, at about 500 bucks.

- makes a mess at removal of the box, lots of dust that needs to be blwon out.

- windmilling prop adds drag in the air at idle.



Pros:

- eliminates any and all stress on that expensive crankshaft at idle as prop is completely disengaged below 2700 or so.

- vastly easier starting, basically eliminates need for expensive, heavy electric starters. Pulling the rope is just like on your lawn mower or snomobile.

- eliminates the extra spinning of the engine in a low-throttle or idle descent that can be hard on the motor. Pull it back to idle and descend at Vne if you want to, you no longer need to worry about this being hard on the motor (PS, no shock-cooling is not an issue, but shock heating is - that's another thread entirely)

- windmilling prop adds drag in the air at idle, adds an extra feature to your plane, a poor-man's drag brake which can be useful in adjusting a high approach.

- stopped prop at idle is quite a novelty on the flight line....



Personally, I'll never NOT use the clutch again on a 2-stroke/C box combination. The advantages are so much more than the disadvantages; I still have my old clutch and C box here in the apt., just in case I get hold of another 503 powered plane at some point.....



LS



  

 

  

 

  

 

  

 

  --[/quote]

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_________________
LS
Titan II SS

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