Edit: report on Evolution .36
 

On the evolution .36 piston there is a portion of the bottom circumference of the piston that has a slight upward curve to it as seen in the picture below. When I disassembled the head and pulled the crank shaft out, I failed to notice whether this curved area was facing to the front (towards the carb) or to the rear(towards the backplate). I cannot tell for sure, the piston will go in either way, in the picture the curved area is right in front of the camera, facing to the rear. You can see it clearly in the picture below. Anyone know? I can get it back together no problem, I just want to be sure that I have the piston oriented the right way.

RE: Evolution .36 reassembly question
 

The cut out goes towards the front.

If you didn't remove the rod from the piston, this can be confirmed by looking at the big end rod bushing. The side that goes towards the crankshaft has a chamfer on the inside edge. The back plate side is straight.

RE: Evolution .36 reassembly question
 

OK thanks!

If I understand you correctly then, in the picture the piston is sitting 180 degrees opposite of what it should be?

RE: Evolution .36 reassembly question
 

Not sure about that...
Is there a "notch" or recess in the backplate for piston skirt clearance when the piston is at bottom dead center?
The engines I have dealt with, that curved bottom of the piston skirt is usually for backplate clearance.


Edit: Taking another look...it could be for counter-weight clearance?

Mike, can you post a pic or 2 of the backplate?

RE: Evolution .36 reassembly question
 

Mike, Tom,


This is exactly what this cut-out is for.

Some engines have a flat in their back-plate, so the uncut piston-skirt will have clearance.


On the rotating crank-web and the rear bearing, such a flat cannot be machined... so the cut-out must be in the piston skirt.


Many engines may have no such 'cut-out' in their original, small displacement version.
But when the manufacturer 'strokes' the engine to offer versions of increased displacement, the piston will have a cut-out at its front; or if there already was one, it will be larger for the stroked version.

This way, the piston can descend further down without hitting anything solid...

RE: Evolution .36 reassembly question
 

I found the exploded view of the engine and it appears that the cutout goes to the front. Reading what you guys have been discussing, it makes perfect sense that the cut out is oriented so that the piston can clear the crankshaft counterbalance. The backplate has a cutout in it so that the piston skirt clears. Seems logical now.

RE: Evolution .36 reassembly question
 

If you didn't take the connecting rod off then the chamfer should make it clear which way it connects, as Jim pointed out.

By the way, how do you like the engine? I've never really looked at the .36.

RE: Evolution .36 reassembly question
 

:eek:,
I have not even run it yet. I accidentally messed up the crankshaft threads a little so I am just replacing the crankshaft. Never damaged threads like that before, this was a first. I did not think that I had tightened the prop nut all that much but when I backed it off the threads were damaged. I just ordered a new crankshaft and it should be here on Wednesday. It was really easy to disassemble so putting it back together should be a snap. I plan on flying the plane next weekend. Its for a review project here on RCU so I will let you know when I get it done.

RE: Evolution .36 reassembly question
 

Great. I have the .45 and .46NT, so I'm interested in how this one runs. You may want to experiment with hotter plugs than the OS 8. The Tower plug gave my .46NT a whole lot more power and it now runs the way it should. The .36 may be the same way....who knows....

RE: Evolution .36 reassembly question
 

Barry,


Which Tower plug?

There is now the [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXJA89&P=RF]Tower Power[/link] and there previously was a hotter version that was even cheaper...

The problem is the Tower Power plug is supposed to be an OS #8 equivalent; i.e. medium heat range.
This doesn't agree with your 'hotter than the OS #8' statement.


The hotter plug Tower offered, that seemed to appear like the OS A3 is no longer on offer...

RE: Evolution .36 reassembly question
 

He's talking about the "Tower Power". It appeared to be remarkably warmer than the OS8 we removed. It was my Tower Power plug that he put in there. The plug was unused but probably 6 years old.

I always considered the Tower Power to more like a A3 It sells for less money than the A3 I doubt if it is like the #8

From the Tower site about OS plugs.....

R5 OSMG2694 Coolest
A5 OSMG2693 Med Cool
#8 OSMG2691 Med Hot
A3 OSMG2690 Hottest

RE: Evolution .36 reassembly question
 

The .45 and .46NT both had problems when starting. It took a long time before fuel would be burned off and I could slowly advance the throttle to WOT. The engines still had a lot of power compared to a couple of others. The Tower plug made a huge difference. First, I can now crank and not worry about advancing to WOT right away. It has nice, full power right away. Also, the .46NT had a whole lot more power in the air. It is very noticable and the engine really runs smoother. I can't hover, but I sometimes try to hold a Somethin Extra and maybe try a tail slide. With the OS 8 I would guess that I was using 3/4 throttle for this. With the Tower plug I am just under half throttle for the same things.

RE: Evolution .36 reassembly question
 

I have to use only stock gear for the review, but if it is not enough power I will try the glow plug upgrade.
The Evolution manual recommends 10-15% fuel but also in another place says that 10-30% fuel can be used. I am a pattern flyer so I have cases of Cool Power 30%. Anyone run 30% in these little engines?

RE: Evolution .36 reassembly question
 

Well I finally flew the Evo .36 today on a 3# 14oz profile 3D plane and all I can say is WHOA! What a little powerhouse. Fired right up and ran like a TOP. It did burn out the factory glow plug on the first flight, but after a quick change it was on. Thing starts instantly and runs perfectly. No load up or issues with the high needle limiter. It turned up fast and ran nice and smooth. Its brand new so I am not sure about longevity, but it sure runs like a bat outta hell out of the box..

RE: Edit: report on Evolution .36
 

Mike,

Good to hear that the .36 is a screamer too. Same thing with my .45 and .46NT. I think that I have over 200 flights on each of those engines and they still run strong.