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bench break in for gasoline engines??? - 1/24/2013 1:31 PM   
Brian Smith


 

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Status: offline 		When I'm looking for a good deal on a nice clean engine to buy used I tend to stay away from engines that were broken in on the bench.. Why do that anyhow? When I install a spankin' new engine on my model I always run it at home for 10 minutes or so to be sure it is adjusted properly/or close enough for first flights, and will start well when I take it to the field for the first time. When I have a new cowled in engine I make the first two flights/tank full of gas without the cowl.. I always thought it was a touchy deal breaking them in on the bench and chance them not getting enough cooling? Is the prop air enough for a new gasser? I have had at least a dozen G38s and G26s and never broke one in other than in the air. Some, the ones I still have, still running like new 10 yrs later. Just wondering. Folks just want to hear/see them run? Brian

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RE: bench break in for gasoline engines??? - 1/24/2013 1:45 PM   
Pete Bergstrom


 

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Status: offline 		Brian,

I totally agree with you.  Ground runs should only be used for operational checks and then do the break-in in the airplane in the air.  We do a lot of bench testing when developing new engines to get some baseline information before moving on to the next steps and head temps are always higher on a bench than they are in the air, cowled or not (assuming you have the cooling in the cowl correct).

Your ground runs should confirm that the engine is behaving as it should (repsonds to throttle and needle changes properly, draws fuel from the tank/fuel system properly, etc.) and that there are no apparent leaks or loose fittings.  After that the next runs should always be in the air.

Pete 

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RE: bench break in for gasoline engines??? - 1/24/2013 3:07 PM   
MTK



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Status: offline 		Yes, I agree as well. The only bench time should be just long enough to set needles, check vibes, etc.

If the engine is cowled, making certain that baffling directs as much ram air over the fins as possible, will usually result in adequate cooling. Hot air exits from the cowl don't need to be elaborate and don't really need to be huge (the old 3:1 rule)....I usually add hoods over the openings that create a slight negative. Hot air is drawn out of the cowling as prop blast blows past the hoods. They create a suction if you will...This way I don't need huge exit openings which look more scalelike.


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RE: bench break in for gasoline engines??? - 1/24/2013 3:08 PM   
Brian Smith


 

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Status: offline 		Thanks Pete
Last eve I saw a G38 for sale a man listed as brand new and had only 2 hrs of break in time on the bench.. Yikes!!!! Brian

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RE: bench break in for gasoline engines??? - 1/24/2013 3:38 PM   
Pete Bergstrom


 

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Status: offline 		Brian,

the nice thing about the G38 is that really the only damage that might have occurred is premature ring wear.  You could buy a new ring, hone the cylinder and you would virtually have a new engine.

Pete 

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RE: bench break in for gasoline engines??? - 1/24/2013 4:35 PM   
RCPAUL


 

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Status: offline 		So, is it true that running a gas engine on the bench is bad. Somehow, this doesn't seem right.

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RE: bench break in for gasoline engines??? - 1/24/2013 4:55 PM   
earlwb


 

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Status: offline 		I don't see bench running a engine as being a bad thing. I like to bench run all the engines, to get them adjusted, work out any problems and issues and get familiar with the engine. Heat cycling the engine probably does the fastest break in though. But after bench running for a while, I move the engine to a airplane to run and finish breaking it in.  But running a engine on the test stand for two hours probably didn't really break it in all that much. So it is likely fine, it just needs to be flown a while, carefully, before it is finished being run in.


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RE: bench break in for gasoline engines??? - 1/24/2013 5:04 PM   
rmh



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quote:

ORIGINAL: earlwb

I don't see bench running a engine as being a bad thing. I like to bench run all the engines, to get them adjusted, work out any problems and issues and get familiar with the engine. Heat cycling the engine probably does the fastest break in though. But after bench running for a while, I move the engine to a airplane to run and finish breaking it in.  But running a engine on the test stand for two hours probably didn't really break it in all that much. So it is likely fine, it just needs to be flown a while, carefully, before it is finished being run in.


Years back, you occasionally saw guys staking out a new model at the field - then running em wide open for a few tanks full-

very annoying as well as being counter productive .
With electrics we no longer see much of this Except for those who want to break in the batteries - -don't laugh - it all happens .

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RE: bench break in for gasoline engines??? - 1/24/2013 5:38 PM   
Brian Smith


 

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Status: offline 		I was more concerned about the heat than wondering if it was broken in. Brian
quote:

ORIGINAL: earlwb

I don't see bench running a engine as being a bad thing. I like to bench run all the engines, to get them adjusted, work out any problems and issues and get familiar with the engine. Heat cycling the engine probably does the fastest break in though. But after bench running for a while, I move the engine to a airplane to run and finish breaking it in.  But running a engine on the test stand for two hours probably didn't really break it in all that much. So it is likely fine, it just needs to be flown a while, carefully, before it is finished being run in.




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RE: bench break in for gasoline engines??? - 1/24/2013 5:55 PM  1 votes
ahicks


 

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Status: offline 		I think that maybe a lot of bench running is done by those not familiar with the care and feeding of the engines (no matter the fuel/type?)? If their motivation is to familiarize themselves and maybe gain some confidence, I really don't see the harm? I'm surely no engineer, and cannot say I've tested hundreds of engines, but I can say I have no first hand experience myself or with any flying friends, where engine damage has resulted from bench/ground running?

Not that I endorse it, I don't. That's from a waste of time perspective. Nothing else... Just me though, FWIW, -Al

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RE: bench break in for gasoline engines??? - 1/24/2013 6:57 PM  1 votes
av8tor1977



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Status: offline 		I put all my engines on the test stand to test them. Once I verify that all is well, needles set, etc., then I run them for maybe a tank of fuel at varying throttle settings, but never at full throttle for more than about 6 seconds. (Long enough to set the high needle and get a tach reading.) I then let it cool down completely, and do the same for one more tank. Then it's time to fly it.

Any bugs that might show up should have done so in that time, and the engine starts to begin the break in process and will usually behave a little better on the plane. (Ever notice the difference between turning over a never run engine, and one that has been run at least one good time?)

AV8TOR

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RE: bench break in for gasoline engines??? - 1/24/2013 7:15 PM   
earlwb


 

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Status: offline 		Some new engines can really vibrate a lot when first run. I have had some litterally shake my test stand apart on me. I got a blister on my finger trying to hold the throttle lever on one engine. But as the engine got dialed in and loosened up some, much of the heavy vibrations went away. I can only imagine what that does to a model plane airframe when someone goes to test run the engine on the plane instead of a test stand.
That might explain some of the firewalls and engine mount systems coming apart on people.


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RE: bench break in for gasoline engines??? - 1/24/2013 8:21 PM   
acerc



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Status: offline 		I bench run mine to get it to a point where the exhaust is not billowing burnt oil. I do cheat a bit though, my Futaba T8FG has a servo cycle feature that I use. I get it set up to run from idle to mid range of the rpm's. Sit back and let her go for a gallon. Then install on airframe. If I didn't do it this way all the oil in the pic below would be on the belly of my scale, fabric covered plane forever. And that was only ten minutes running.

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RE: bench break in for gasoline engines??? - 1/24/2013 8:33 PM   
MTK



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quote:

ORIGINAL: earlwb

Some new engines can really vibrate a lot when first run. I have had some litterally shake my test stand apart on me. I got a blister on my finger trying to hold the throttle lever on one engine. But as the engine got dialed in and loosened up some, much of the heavy vibrations went away. I can only imagine what that does to a model plane airframe when someone goes to test run the engine on the plane instead of a test stand.
That might explain some of the firewalls and engine mount systems coming apart on people.


That's eaxctly the reason I soft mount all of my smaller gassies Earl. Up to 100 cc is not a big deal to soft mount. I've not run anything larger so I don't have first hand experience with larger displacement. Even when I set up for a bench run for needle setting, I install engines on their soft mounts for the tankful of bench running.

By chance, I didn't do that once on a memorable and enlightening first run of one 38cc engine. The run was made with the bench fastened to my wood deck in the back yard as I do normally. And as luck would have it, I ran the engine barefoot. The vibration my feet felt was uncomfortable. I stopped the test and mounted the engine properly; vibes to feet gone.

BTW- my firewalls for engines as large as the DLE55 are 1/4" cross grained balsa laminated with carbon cloth on both sides. I remove the center section of the firewall to further lighten them. Works great!! And folks shouldn't think that these things are heavy, they are not. A typical soft mount for a 35cc engine weighs 3 ozs give or take and the firewall maybe 35 grams.

< Message edited by MTK -- 1/24/2013 10:05 PM >


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RE: bench break in for gasoline engines??? - 1/24/2013 10:56 PM   
Indiomike


 

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Status: offline 		If the concern is that the engine will not get enough cooling air by bench running it, then do what I do. I place a fan in front of and below the engine test stand. It blows air directly at the cylinder head in addition to whatever air the propeller provides.

I have a high quality infrared heat gun that I can aim right where the plug enters the head to monitor temperature. I think that is the hottest spot on the engine. I recently ran a DLE 20 for about 30 minutes and never saw the temp higher than 267 degrees (F). To the best of my knowledge gas engine temps are fine up to a max of about 300 degrees(F).

Mike

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RE: bench break in for gasoline engines??? - 1/24/2013 11:04 PM   
oneaew@msn.com


 

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Status: offline 		guys bench run there engines 40 yrs ago i put mine on the plane start it and go no bad luck yet so do what ever you feel like doing and enjoy it

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RE: bench break in for gasoline engines??? - 1/25/2013 12:41 AM   
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Status: offline 		  + 1  Indio   if it is not HOT  it wont hurt any thing     Just run it       

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RE: bench break in for gasoline engines??? - 1/25/2013 1:34 AM   
Propworn


 

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Status: offline 		Break it in on the bench or in the airframe. Before anyone gets bent out of shape is there any empirical data out there that shows which is the best way. I’m not talking about personal preference or what you have been doing for 150 years I’m talking scientific evidence that speaks to the question with data not someone’s opinion.

I sort of do a combination of both. I bench run mine in the position it’s going to be mounted upright, horizontal or inverted with the fuel tank as close to the engine as possible and the centerline of the fuel tank on the center of the spray bar. Yes even for gas motors I align the center of the tank with the center of the carb. I figure this is as close to the perfect installation as one could plan. I do this to tune the engine and get it running the best I possibly can. Now if I mount it in the airframe and it runs any different than it did on the stand that tells me my installation is possibly lacking. It allows me to make alterations to get that engine to run as close to the way it did on the stand. By this time the engine should be running well and have no dependability issues and its time to go flying. My cowls always have fiberglass air dams that direct the flow of intake air around the cylinder and block making sure the openings for exiting air is greater than the inlet. Engine cooling is enhanced by directing the air around the cylinder and block allowing for tighter cowls and more scale like cowl openings. Nothing in my opinion looks worse than a beautiful model with half the cowl cut away for cooling.

I personally have test run model engines on test stands and in wind tunnels at the university when the team was doing dynamic testing of different props sometimes putting them through some grueling runs with no noticeable problems.

If I were buying a used engine I would be more concerned with the experience of the previous owners than where the engine was broken in.

Dennis


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RE: bench break in for gasoline engines??? - 1/25/2013 1:55 AM   
acerc



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Status: offline 		Dennis I'm sure someone has done such. I personally don't think it matters either way. I only use the stand for motors that are going on something that can't be cleaned. My Ultimate has mono or ultra-coat, easily cleaned, so I did not use a stand but fabric covered, not happenin.


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RE: bench break in for gasoline engines??? - 1/25/2013 3:28 AM   
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Status: offline 		Start em up run em fat for a flight, then pound on em. Dennis

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RE: bench break in for gasoline engines??? - 1/25/2013 3:35 AM   
oneaew@msn.com


 

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Status: offline 		i just got h..l sort of for saying what i thought but flying for 40 yrs plus and being 80 i guess i dont know to much

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RE: bench break in for gasoline engines??? - 1/25/2013 4:19 AM   
freeonthree



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Status: offline 		Im sure you know what works for you by now. In this hobby, we have to do what feels good to us, and if someone asks a question, they will usually get alot of different opinions, then it's up to the asker to use their comon sense, and decide what sounds the best to them. Dennis

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RE: bench break in for gasoline engines??? - 1/25/2013 5:31 AM   
Ernie Misner



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Status: offline 		The engines from Valley View all get a nice 20 minute run on the bench before being sent out. Tom said he wanted to give an XYZ 20cc a good test so he cranked it wide open and then went out to lunch for a while. When he got back it was still very happily screaming away.

Are gassers any different than glow engines for breaking in on the bench? I've broken in all my glow engines on the test stand and they've done me well.

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RE: bench break in for gasoline engines??? - 1/25/2013 11:33 AM   
Propworn


 

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Status: offline 		Exactly. I’ve been in the hobby for a long time starting off at 11 years old knowing very little and growing the habits and techniques that I am comfortable with today. These work for me and I have confidence in what I am doing. If someone wants to know I will gladly share that information with them. I know others that are just as successful doing things their way so I know there is more than one way to skin a cat. Which one is the best? Who can say? Start out by finding the guy locally who seems to be the most knowledgeable and successful in what ever technique you are interested in, be it engines or setting up an aircraft. Politely ask if he would be willing to share his methods with you. You will be surprised to find how many are wiling to do this. You will also find that you may choose what information you will use and which you will discard thus growing the habits and techniques that you will have confidence in and you know they will work for you. There is always something new to learn or consider so try to keep an open mind some of the very best ideas come from some of the most unlikely sources.

Dennis


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RE: bench break in for gasoline engines??? - 1/25/2013 11:52 AM   
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Status: offline 		All of these approaches have merit. I warm up a new engine, lean out the needles til satisfactory, then run out the tank at 4k til it runs dry. I use an air hose for the pump breather so when I reattach the cowl, the needle settings don't change. I then fly it and set the high-end according to what I hear. Works for me. Plus, the landing practice is always good!

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