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jrtrebor


Location: Michigan - 3 hours north of Chicago on the lake
Joined: Feb 10, 2010
Points: 539

Inside an R-Tek engine
Original Message   Feb 15, 2012 6:05 pm
Well I got the bolt stud welded, new old flywheel on, air gap set, good spark.  Put everything else back on the engine.
Still don't have the gov. vane so I just used the spring to keep the throttle at the idle position and used the idle screw
to bump up the idle up a little.  Put the engine back in the housing and it start on the third pull.
Was idling and running well, then I heard a knock, couple seconds later heard another one then another one.
So I shut it down.  Was one of those sounds you know isn't good, kind of a deep sounding clank.
It only made the sound maybe 3-4 times in about 20 maybe 30 seconds or run time.
Pull the engine back out and decided to take it apart to check the rod cap.
When I took the flywheel back off found that the new key I put in was sheared.
( could have had something to do with the knock)
Was really clean inside.



Intake port I believe



Exhaust port.  The two ports on the side run down into the crankcase.  Which is up in the photo.



Rod end on crank. You can see the roller bearings
Rod cap was tight.




Roller bearings in the cap.  Most of them stayed in place when I lifted it off.




I decided to put in the old crank I had from another R-Tek.  Same part numbers.
I put a few drops of oil on the crank journal so the bearings would stay in place.
There is enough space for one more bearing, but that's all that came out.
I guess once they all get spaced that's the way it should be.




A few photos of the difference between the two cranks.  Same part numbers.
Top one is the older one out of a CCR2400
The ends of the counter weights are clipped off on the newer crank. (bottom photo)
and the casting itself is a lot rougher.




New crank on the left.  If I remember to I'd like to weight them both.




Just for comparison.  Honda 11Hp crank on top.




Key way slot on the replacement crank.
Things were going well until I cracked a ring.  Hate when that happens.  There is an alignment pin in the
piston ring groove for both rings.  It keeps the end gap space of both of them aligned right above each other.  Which normally you don't do.
Unfortunately I didn't see the pins at first, pushed on the ring when it was on top of the pin not aligned in the end gap and.... snap.





This message was modified Feb 15, 2012 by jrtrebor
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RedOctobyr


Location: Lowell area, MA
Joined: Nov 5, 2011
Points: 282

Re: Inside an R-Tek engine
Reply #27   Feb 18, 2012 11:22 am
My little R/C nitro glowplug engines turn around 25,000-30,000 RPM, as I recall. With itty-bitty brass/bronze bushings at either end of the connecting rod. I believe there are ball bearings supporting the crankshaft at either end, at least in mine. Mine were small .12 in^3 car engines. The castor oil in the model fuel is apparently enough. As I recall, the oil percentages are higher than for mixed-gas 2-strokes. Seems like around 8%-12% or so oil is common. So there is much more oil than for 2-stroke OPE. I think most of the mess that comes out of the exhaust is the oil. You can lean up the engines for more power (and less mess, I suppose), but the temperatures will climb significantly, and it's not good for the engine. You can tell when the car is running out of gas, and starts sucking in some air bubbles, because the RPMs will just scream for the last few seconds, if you give it full throttle.

trouts, I don't think the flywheel's mass would really affect HP output or rating. It would affect how quickly the engine could speed up or slow down. But in terms of steady-RPM power output (at stock speed, or a higher speed), I don't think it would make a meaningful difference. Once the flywheel is up to speed, a heavier flywheel shouldn't really sap additional power to maintain that speed. Now if one flywheel had much larger cooling vanes, let's say, that could make a difference, as it would be using more power to move the additional air around. So less of the engine's gross power output would be left to drive the rest of the machine.
This message was modified Feb 18, 2012 by RedOctobyr
borat


Joined: Nov 10, 2007
Points: 2692

Re: Inside an R-Tek engine
Reply #28   Feb 18, 2012 12:05 pm
I agree that the weight of the flywheel will not have an overall effect on horsepower but it will have effect on how the power is delivered. 

A good example of flywheel weight variation and effect is the difference between a motocross race bike and an enduro race bike.  Motocross machines have a lighter weight flywheel to allow for much quicker throttle response to deal with the quickly changing terrain/obstacles/layout of the race course.  Some tuners actually change flywheel weight to match certain types of tracks (indoor vs. outdoor).  An enduro race is all outdoors and over much more varied conditions from rocks to swamps etc.  Tractability outweighs throttle response in an enduro race.  The heavier flywheel helps to sustain engine torque and keep power manageable.  Particularly in tight twisty woods trails where breaking the back wheel loose at a bad time will put you into a tree of off the trail.  Been there, done that, it hurts. 

On a piece of OPE, my preference would be for a heavier flywheel to sustain torque when the engine is subject to varying loads.  As in a snow blower or even a lawnmower.
This message was modified Feb 18, 2012 by borat
jrtrebor


Location: Michigan - 3 hours north of Chicago on the lake
Joined: Feb 10, 2010
Points: 539

Re: Inside an R-Tek engine
Reply #29   Feb 18, 2012 3:11 pm
trouts2 wrote:
  The newer flywheel is thinner and might have been a change for higher revs rather than metal shaving for cost.   Strange as you'd think they would have bumped the part number.  Would the amount of metal lessened contribute to HP via an rpm change i.e. make it a bit easier to spin.  ??

The new flywheel is definitely thinner an lighter.  But as others have said, having a lighter flywheel is usually about having a quicker throttle response.  A lighter flywheel would be
easier to spin up.  But it also has less inertia.  Which for a snow blower would really not be a good thing. 
 It takes more effort / force / resistance to slow down a larger heavier moving mass than a small lighter one.  Actually I don't believe the weight of the flywheel would have any effect
on the max RPM.  The governor is going to control that regardless of the flywheel mass is.
borat


Joined: Nov 10, 2007
Points: 2692

Re: Inside an R-Tek engine
Reply #30   Oct 15, 2012 5:07 pm
JRT:  Whatever happened with this project?  Did you ever get the subject R-tek engine running right?
jrtrebor


Location: Michigan - 3 hours north of Chicago on the lake
Joined: Feb 10, 2010
Points: 539

Re: Inside an R-Tek engine
Reply #31   Oct 15, 2012 5:36 pm
borat wrote:
JRT:  Whatever happened with this project?  Did you ever get the subject R-tek engine running right?

Yes, I did.
But we had so little snow last year I think I only got to use it once.
And that was on an amount of snow that wasn't even worth talking about.
Took quite a bit of time to get that one sorted out. 
But I think it's a pretty nice machine.
It was in excellent cosmetic condition, no rust anywhere.
Seems to run fine with the crank and flywheel swap.
That thing had some major problems.






borat


Joined: Nov 10, 2007
Points: 2692

Re: Inside an R-Tek engine
Reply #32   Oct 15, 2012 5:46 pm
That's some nasty stuff.  So what was the underlying cause of malfunction?  Bad crank? 
jrtrebor


Location: Michigan - 3 hours north of Chicago on the lake
Joined: Feb 10, 2010
Points: 539

Re: Inside an R-Tek engine
Reply #33   Oct 15, 2012 8:10 pm
borat wrote:
That's some nasty stuff.  So what was the underlying cause of malfunction?  Bad crank? 

Ha,Ha good question.  Kind of the chicken or the egg question.
Actually I think the flywheel may have been the initial problem.
That flywheel doesn't or didn't have a steel center hub.
Like the one I replaced it with.
I figured that the hub cracked or was cracked from over tightening.
The flywheel got a little sloppy on the shaft.
Started to maybe wobble a little, got a little more sloppy.
Which may have started to throw off the timing some.
Now it's firing at the wrong time.  More stress on the crank / flywheel
joint.  Then at some point things went from bad to worse real fast.
You can see how the key actually wobbled left and right in the slot.
So that flywheel hub had to be really loose on the shaft for that to happen.
That engine look so new inside and out.  There wasn't even any carbon
in the muffler inlet or outlet.  I think this may have been a factory assembly problem.
Or defective flywheel.
Just my somewhat educated guess.
This message was modified Oct 15, 2012 by jrtrebor
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