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Test stands for break in (not good) - 5/14/2008 3:55:41 AM   
RC Extreme power



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Joined: 12/30/2001
From: AUBURN, GA, USA
Status: offline 		I know a lot of people think they need to break there engines in on a test stand or on the plane while not flying,

If you do this be care full and do not run for longer then a few min. at a time, You think that a lot of air is moving over the engine and cylinder but it is not, Most of the air is moving to the tips of the prop and not going over the engine, Plus most stands have a solid piece of wood behind the cylinder and air could not pass if it got there.

Even in the plane air is not moving over the cylinders and they will heat up if it is not flying.

I am rebuilding a engine now that was on a test stand and customer said he did not know what could have happened he just set it at about 3500 RPM and after 15 min. It just locked up, Well the cylinder and piston are cooked.

If you insist on breaking in with a stand or on the ground do it for short periods and let it cool between runs.

I will run maybe a tank through the engine while tuning and setting it up and then break it in where it will be running In the air


Milton

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RE: Test stands for break in (not good) - 5/14/2008 4:32:22 AM   
Whistling Death


 

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Status: offline 		What engine is it?

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RE: Test stands for break in (not good) - 5/14/2008 4:41:22 AM   
RC Extreme power



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Status: offline 		Ones that I sell, But put any engine under that condition and the same thing will happen.

Milton

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RE: Test stands for break in (not good) - 5/14/2008 6:23:41 AM   
the Wasp


 

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Joined: 9/29/2003
From: Rutland, VT, USA
Status: offline 		""But put any engine under that condition and the same thing will happen""

oh please, what condition, too lean ?, if you run it rich you wont have a problem !!

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RE: Test stands for break in (not good) - 5/14/2008 12:08:23 PM   
Jake Ruddy



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quote:

ORIGINAL: the Wasp

""But put any engine under that condition and the same thing will happen""

oh please, what condition, too lean ?, if you run it rich you wont have a problem !!



You should never run a gas engine rich... these aren't glow engines and all you do is foul plugs and stick rings.

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RE: Test stands for break in (not good) - 5/14/2008 2:39:12 PM   
Tired Old Man


 

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From: Central, CA, USA
Status: offline 		Milton is correct. What he has seen with this engine is quite common, and the engine manufacturer doesn't matter. All can suffer the same fate. Few that run an engine on a stand for extended periods of time ever disassemble the engine and check the condition of the rings and cylinders after running. The vast majority just remove the engine from the stand and hang it on the front of the plane. They fail to notice that compression has dropped significantly, or if they do they might thnk that the lower compression was due to rings "breaking in". If they were to disassemble the engine they might find the compression loss was due to the piston ring beginning to stick at the exhaust port side of the piston.

Without cooling air additional to what the prop provides there is a good chance that the engine can be damaged by long runs on a stand. The prop does not provide very much airflow through the cylinders, and without having the air ducted through the cylinders the air from the prop has little cooling effect. Simply using the exhaust side of a shop vac with the hose directed to the side of the cylinder will provide much better cooling and permit long runs on a test stand. Monitoring the cht with a thermocouple and live data feed is also important. Temp guns are useless for even coming close to the actual cylinder temps.

I have the feeling that Milton's customer lied to him though. At 3,500 rpm it would have taken quite some time to cook the ring and coke up the engine. It was liklely run continuously at full throttle for quite some time. The oil and mix ratio selected will have contributed to the problem as well. As Jake noted, there is no point in running a gas engine rich.

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RE: Test stands for break in (not good) - 5/14/2008 2:47:57 PM   
dick Hanson



Posts: 10066
Joined: 12/12/2001
From: slc, UT, USA
Status: offline 		Experience
I have repaired broken engines ,broken airframes -broken battery paks
The common thread is the info provided must be carefully reviewed.
some people do provide usable info- regarding what happened to the item.
However when it comes to screwed up engines the reasons for the failure are often very "interesting"

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RE: Test stands for break in (not good) - 5/14/2008 4:42:45 PM   
Whistling Death


 

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quote:

ORIGINAL: Milton

Ones that I sell, But put any engine under that condition and the same thing will happen.

Milton

I was just wondering because I have run one of my Zenoah G62's (on a test stand) through several full tanks of fuel (32oz.) with no ill effects. I have since had it converted to EI and it is currently on my Giant Aeromaster. It flies like a bat of of h##l.
I am not saying a guy won't ruin an engine on a test stand and don't advocate doing it, I am just saying it didn't ruin my engine.

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RE: Test stands for break in (not good) - 5/14/2008 6:52:45 PM   
the Wasp


 

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you don't have to run it that rich !!!!

Jim

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RE: Test stands for break in (not good) - 5/14/2008 6:58:08 PM   
Jake Ruddy



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Joined: 5/22/2005
From: Bear, DE, USA
Status: offline 		So tell me, just how rich is that rich? It doesn't take much... oil is either getting burned or building up.. there isn't much room in the middle.

Either way no sense arguing.. I dont even see the need for bench run ins anyhow.. throw it on the plane add Penzoil 50:1 tune it properly from day 1 and fly it. All this other stuff is a waste of time.

Next we will be talking about what oil to use again

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RE: Test stands for break in (not good) - 5/14/2008 7:48:14 PM   
Hughes500E



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Status: offline 		2 strokes don't need oil, its in the gas

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RE: Test stands for break in (not good) - 5/14/2008 8:02:13 PM   
the Wasp


 

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Status: offline 		I guess you didn't see that reply whereby the guy brakes-in his Zenoah G 80 twins on the bench by setting the RPM to 4000 and letting it set for a couple hours !!

"how rich" I ran my MVVS 35 about 700 RPMs below it's peak RPM on the bench, but I didn't run it to full throttle for a good 4 tanks,,

think about it, how much oil do you run in 5 gallons at 50 to 1, only about 15 oz, even less at 80 to 1, well in the 70s I ran 32 oz to 5 gallons in my Trials bikes, these are low revving engines and I very very rarely ran them over 15 MPH all day long, stop and go all day long and they never over heated never fouled a plug..

I ran my MVVS at 28 to 1 for the first gallon on the bench, then I leaned the mixer to 32 to 1 on the 2nd gallon on the bench,, 3rd gallon was 36 to 1 in the air, 4th gallon was 40 to 1 in the air..


""2 strokes don't need oil, its in the gas"" LOL Hughes LOL
Jim

< Message edited by the Wasp -- 5/14/2008 8:15:07 PM >

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RE: Test stands for break in (not good) - 5/14/2008 9:18:23 PM   
Jake Ruddy



Posts: 3035
Joined: 5/22/2005
From: Bear, DE, USA
Status: offline 		It's just like an oil debate... some want to bench run them and some of us don't see the point. Thats 4 wasted hours when I could be flying it

Might also like to consider where Zenoah comes from.. its designed to take abuse which is part of the reason why they are generally heavier.. more material to help disapate the heat.

There are many rc engines that wouldn't stand up to that. They are designed to be light and powerful and require proper cooling. Just look at the fins (or lack of) and how thin they are.

My 60 has run from day one on 50:1.. 50+ gallons later still running like a charm and looks great inside.

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RE: Test stands for break in (not good) - 5/14/2008 9:25:43 PM   
the Wasp


 

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From: Rutland, VT, USA
Status: offline 		now I will give you that, that was well said and understandable,,, thanks god I have a MVVS

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RE: Test stands for break in (not good) - 5/14/2008 9:44:36 PM   
Tired Old Man


 

Posts: 11537
Joined: 2/25/2002
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Status: offline 		Try running a BME 110 or an older 115 on a stand for a few hours without additional cooling air. You might get lucky, but the odds are against it if the rpm level is much beyond 50%.

< Message edited by Pat Roy -- 6/4/2008 5:37:29 AM >

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RE: Test stands for break in (not good) - 5/14/2008 9:56:37 PM