RE: ringed engine break in?  
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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Glow Engines >> RE: ringed engine break in?
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RE: ringed engine break in? - 6/2/2006 11:34:05 PM   
loughbd


 

Posts: 2111
Joined: 11/29/2003
From: Bremerton, WA, USA
Status: offline 		Hey Baxter,

I agree with everything you just wrote. I differ a bit from you. I will use a smaller than normal prop for break in. Say on a 60 I'll use an 11x7 cut to 10 inches. It will run at a reasonably high rpm but being very rich won't overheat. I usually do a series of 5 minute runs getting leaner each time until I use the 11x7 and the engine will hold a two cyclew without sagging. Thing I fly it still a bit rich until it haa about a half hour on it. That's how I break in most ringed glow engines.

(in reply to Bax)
       Post #: 101

RE: ringed engine break in? - 6/2/2006 11:55:20 PM   
dick Hanson



Posts: 9929
Joined: 12/12/2001
From: slc, UT, USA
Status: online 		do not over prop - do not over heat - do not overheat and do not overheat also vary engine speed and do not overheat - that is a good break in sequence - use plenty of good oil 20% min on ANY glow engine
also do not allow to over heat .
we ran .049 engines in --1949 or 1950 I forget - but it was the same then . do not overheat .
the worst tolerances in an engine, which also needed refitting very often was- FOX - some of the engines we had to refit twice to get proper running clearances. Early Enyas were a close second fit far too tight in many instances. The Chinese early engines were simply almost unusable- horrible fits.
Cox did the best job of temperature controlled machining - and could hold better tolerances than anyone .
Any of the current engines I have run - typically just needed a few trial run ups to see how they handled heat - NO extended running -I can tell in ten seconds if the fit is OK to fly- Then we fly varying th rpm and if I did not mention it - making sure to not overheat it.

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(in reply to loughbd)
       Post #: 102

RE: ringed engine break in? - 6/3/2006 12:19:37 AM   
loughbd


 

Posts: 2111
Joined: 11/29/2003
From: Bremerton, WA, USA
Status: offline 		Hey Dick, is it true we shouldn't overheat an engine while breaking it in? Over propping is the surest way to cause overheating. That's why I use a smaller prop and run very rich during break in.

Yup Cox had the tightest tolerances of any engine manufacturer.

When Clarence Lee makes one of his custom K&B61's part of the procedure is to measure the pistons and cylinders and get the biggest piston in the smallest cylinder with out over doing it. Ie, the piston still has to be a shade smaller than the cylinder. Ganging of tolerances is what makes a poorly fit engine. Cox had the best fitting piton/cylinder fit overall.

Some of the old lapped Enyas had very tight piston/cylinder fits but when properly broken it had unbelievable compression. They could sit a TDC for 5 minutes and still pop out when turned. Johnson's were like that too.

You are right. Some of the old Fox engines were horrible and the Chinese stuff was one step above junk.

< Message edited by loughbd -- 6/3/2006 12:22:59 AM >

(in reply to dick Hanson)
       Post #: 103

RE: ringed engine break in? - 6/3/2006 4:08:00 AM   
dick Hanson



Posts: 9929
Joined: 12/12/2001
From: slc, UT, USA
Status: online 		Now thanks to production equipment that measures as it goes etc., poor fits are a rarity.
The best stuff - for years -- the OS line - I did .61abc (actually not abc) pattern engines -for me and others - I could purchase pistons and liners - separately and drop a piston into a liner - --they all fit and stopped at almost exactly the same place in the bore . and the same finger pressure to move to "solid" fit.
the current line of OS four strokes are still a favorite .
powerwise the Saitos beat em for power to weight but the OS 70/91 four cycle engines are bulletproof
I ran em on 40% nitro and 20% oil for hours - no undue wear and simply fantastic power for the size. None of the gasoline engines have hit this mark of overall precision----yet-- but they are rapidly getting there ---

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(in reply to loughbd)
       Post #: 104

RE: ringed engine break in? - 6/3/2006 4:32:06 AM   
loughbd


 

Posts: 2111
Joined: 11/29/2003
From: Bremerton, WA, USA
Status: offline 		Haven't you heard?? According to the people here, OS is turning out junk now.

(in reply to dick Hanson)
       Post #: 105

RE: ringed engine break in? - 6/3/2006 4:37:29 AM   
William Robison



Posts: 20269
Joined: 11/10/2002
From: Mary Esther, Florida, FL, USA
Status: offline 		Not junk, Bruce, just not worth the money. And yes, that's an opinion; mine.

Bill.


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AMA 25139 - More than 40 years.

(in reply to loughbd)
       Post #: 106

RE: ringed engine break in? - 6/3/2006 7:10:51 AM   
DarZeelon



Posts: 6975
Joined: 4/9/2003
From: Rosh-Ha'Ayin, ISRAEL
Status: online 		Bruce,


Most current sport .61 engines are under-propped with an 11x7 prop.

The late 70s/early 80s piped F3A engines, like those used by Dick Hanson on his Tiporare and by other pattern competitors in those days, which would spin an 11x7-11x7.75 prop, around 14,300-15,300 RPM, in ground static condition, would unload for more RPM in flight, reaching their real HP peak RPM of 16-17,000.

Most current sport .61 engines, as they come, with their original silencers, peak around 13,000 RPM, despite anything their manufacturers claim they can do...


So the right size prop is a 12x6, or a 12x7 (or one of equal load) that will have the engine spinning around 11,500 RPM on the ground.

The 11x7 size will not cause the engine to overheat, but if extra cooling is desired, a higher pitch prop of equal load will be much better than chopping the 11x7. A 10x9 is the best choice, if over-heating is feared with an 11x7.

< Message edited by DarZeelon -- 6/3/2006 7:11:58 AM >

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(in reply to William Robison)
       Post #: 107

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