OK2Fly

Rcpilot, would you say this process works for all gassers? I want to try a similar method, but all this talk of engines getting fried on test stands have made me a little hesitant.

AussieBrett

Guys..i have recently purchased a few excellent test stands from the UK via ebay...and was about to use them...(always ran motors in on planes till now)....I have learnt to start the motor, let it run a bit (few mins rich) then turn off and cool, then repeat a few times (hot-then cold-hot then cold etc)...so i have learnt something from this thread...BUT, i cannot see how the air blowing from the prop doesnt cool the motor, and i cant see how the motor can be damaged if run on the richer side...surely no one is dumb enough to run a motor, anytime, anywhere (on ground or in plane) if it is lean and at max rpms..that is dumb...??.but....WHY doesnt the air from prop cool the motor....surely if motor running mostly at lower rev range and then up to 70 percent max for short periods (only 100 percent for say 5 secs) on richer side on a cool day (early morn or late arvo)...WOULDNT THIS BE OK...now help me with the air from the prop theory...and if someone really experienced using test bench run ins could post what is the best way to do it from start to stop....THANKS...P.S- i have about a dozen motors to run in, ranging from OS46ax to supertigre 90 to supertigre 3250 and supertigre 2300 as well as a few tigershark 120 and a heap of ASP/Magnum 91 and 120 fourstrokes for a dozen different projects my buddy and I are all working on..all 2 strokes have pitts mufflers...great advice wanted re test stand running in, pls experienced peoples., regards brett from australia.

captinjohn

Please read post #18 and #19 over again. Pat is one of the most experienced engine gurus you will ever meet. Best Regards Capt,n

AussieBrett

can i run motors in the way i mentioned...or not really!!..regards, brett

Tired Old Man

My Feedback: (1)

In theory, yes, but that depends a lot on what you consider "hot", and how you define that level. Running at high throttle for a minute or two then idling down to cool the engine, then back up to low middle to mid throttle for a minute or so, then back to idle for a few minutes, then shut down to cool. Keep the high rpm time to a minimum and use the low rpm levels to assist cooling. If only done for an extremely brief period the increase in throttle to high rpm will actually cool the engine, but only momentarily. Heat rises extremely fast after that.

Rather than attempt to debate how much air makes it through a prop, then througha cylinder head, try the smoke test and see for yourself. All I'll add is that a spinning prop acts very much like a solid disc when it's turning fast so how much air can travel through an 18"to 34" diameter dinner plate?

RCPAUL

My Feedback: (1)

We are saying that an engine on a test stand out in the open (not against a wall) will over heat on a test stand. That there is insufficient air from the prop at the head fin height to keep the engine sufficiently cool. Is that what your saying?

I don't believe it!

How does my weedwacker keep running - no fan in an enclosed housing.

How does my yard blower keep running - no fan only the head exposed.

How do guys with engines in cowls start, run them, then taxi out with the engine against a firewall?

I don't believe it. Let someone give temp data. Let someone with an anemometer put it behind the prop at full bore and measure the wind velocity.

Paul

Jake Ruddy

My Feedback: (40)

RCPAUL The yard tools you are mentioning are designed to run like that. As for the G-62 so is it really.

I don't understand why people have such a hard time grasping this.. if the air is not being directed through the fins then the engine is not being cooled properly and can lead to a fried engine.

Antique

My Feedback: (4)

Garden tools are designed to direct the airflow over the head (baffles). The fan on a garden tool is the blades on the flywheel. Too rich on the oil mixture will end up developing a load of carbon on the piston, combustion chamber and in the worst place of all, in the ring grooves.

BillHarris

Has anyone actually measured the cylinder/head temps on a test stand and in-flight with an Eagle Tree Systems data recorder? Just curious.

Bill

the Wasp

My Feedback: (1)

OK so lets just say the MVVS 35 is the only engine made well enough to stay cool while braking-in on the stand

Rcpilot

My Feedback: (78)

NO.

There are so many variables here. To say that ALL test stands for gas engines will lead to a burnt cylinder or fried engine is IMO misleading.

Can it be done successfully? Sure.

Is it necessary? Not at all.

Are you taking a risk by running an engine on a test stand? Positively.

Are you taking a risk by running an engine in a cowl without proper baffles? Positively.

Too many variables to say that it DOES work or DOES NOT work. It depends on how you set up the stand. Depends on the prop you are going to use. Depends on how you tune the engine on the stand. Depends on what fuel/oil mix you are using. Depends on if you're holding your tongue out the left side or right side of your mouth. [sm=tongue_smile.gif]

I know of one VERY popular and respected member on this site who uses test stands to set up pipes and headers on large and small gas engines. He probably doesn't run them for hours at a time, but it does take some running to get a pipe properly adjusted. Not just 10 seconds here and there. I seriously doubt he'd be doing it if he was cooking motors on that stand.

I'm not advocating one way or the other here. I'm saying that I did it once and it worked. I'm also saying that I don't think it's necessary. I did it to my G-62 when I was a newb to gas engines and I had no idea how reliable they actually are. I don't use a test bench anymore. I bolt it up to the firewall and tune it a little bit rich. Then I pour the coals to it and fly it like a hate it.

Properly tuning of a gas engine is NOT rocket science. It just takes some time and know-how. A properly tuned, propped and baffled engine should never overheat. It's not the RPM,s that kill your engine. It's heat and sudden impacts with dirt.

OK2Fly

Sounds good.

It was pretty cool how you hooked it up to a 5 gallon jug and walked away. That's a hell of a break-in period. I'm convinced...no benches. Just for short runs, tuning exhausts, and any long period run should be done with some kind of effective cooling system besides the propwash (if a bench is used.)

Tired Old Man

My Feedback: (1)

I use the Eagle Tree products for my personal toys. Both well illustrate what takes place in and at an engine with one system going waay over the top in information.

There's some very knowledgeble and experienced engine people out there, such as Dick Hansen and a few others, that won't get into trouble because they know how to set up, what rpm levels they can run at, for how long, and use effective oil mix ratios, but there are far more that don't have a clue what they are doing. The responses from those that can't or don't understand how air does or doesn't move through a propeller are proof of this. Those that elieve that extended running on a bare test stand is a good way to break in are another group that don't have a clue.

For the average person, a simple tuning run on a test stand is just fine but the break in process should be done on a plane.

BillHarris

SO, how do the test stand and in-flight cylinder/head temperatures compare?

No answer? Urban legend.

Bill

RTK

My Feedback: (1)

Yep, I have done a lot of testing with in flight temp recorders. In fact you can tune some engines to run cooler at WOT than at mid range. A lot depends on how much fuel is going in, air flow and load. As many have mentioned, I set the needles to get it running right and consistent on the ground then fly. Then I adjust to how it runs in the air from there.
Remember one thing. You won't burn up an engine running it too rich, but you sure will running it too lean with adequate air flow

RTK

My Feedback: (1)

Upon landing if you temp the hottest part of the cylinder you can expect (if not properly baffled) to hit more than 100* above that in flight when pushing it. Also, The front of the cylinder can vary anywhere up to or more than 60* compared to the back of the cylinder depending upon baffling.

Tired Old Man

My Feedback: (1)

An open test stand can and usually runs much hotter than an engine in flight. That supposes all else is close to equal in tuning and oiling. One part of the cylinder controls almost completely how long the engine is going to survive and that's the part on the exhaust side of the cylinder. Just about all of the newer engines intended for aero use have cylinder fin designs that are absolutely terrible for adequate cooling so we get to jump through hoops to correct the design deficiencies. But hey, we have a lighter engine, right? Then again, even if the cylinders had the right amount of fin area in the right places we would still need to baffle in order to direct the air where it needs to go.

A poorly baffled twin won't matter where you run it. Toast is toast if it doesn't get air through the right places. A hidden cylinder single can suffer a similar fate. A 50cc single needs well over 20 liters of air per second running through the fins to cool it, and you still need to slow it down as it passes through the fins to absorb and carry away the heat. Next you have the extraction process...

RTK

My Feedback: (1)

Low pressure lips and louvers do wonders for extraction

Rcpilot

My Feedback: (78)

I just got lucky. I could have fried it.

Thats why I said that I don't recommend it. I did it ONCE and it worked.

The neighbors were not real happy with me. Do you know how long it takes to run 5g of gas through a 60cc engine at WFO? HOURS and HOURS. I could have been flying it. [:@] But I was a newb and I thought I was doing the right thing. Just got lucky.

the Wasp

My Feedback: (1)

rather it is or not better to brake-in an engine in the air I would bet if we did a poll~ we would find that many more engines have been damaged in flight during the braking-in process than being broke-in on the stand !!,,

and,, more planes have been crashed while engines have been broken-in while flying than broken-in on the stand..

the Wasp

My Feedback: (1)

""A 50cc single needs well over 20 liters of air per second running through the fins to cool it""


boy am I glad you didn't say a specific amount like 23 liters or 27 liters !!

Jim

Antique

My Feedback: (4)

Anybody remember the oil tests run by rcbugman ???? Heavily loaded engines run for about 6 hours at a time, WOT....None burned up....
Do a search, the results and pictures are there....Then come back and justify your position on how running an engine at WOT on a test stand will burn it up....

the Wasp

My Feedback: (1)

yes, and wasn't it a 3W ???

RTK

My Feedback: (1)

It also was about 32 degrees OAT

jeffk464

Ok are we talking the modded glow to gas engines with small cooling fins or are we talking the engines with large cooling fins? It seems to me they would have a huge difference in cooling air requirements. Is it ok to run engines with the large cooling fins on a test stand? I see people at my field running Desert Aircraft engines cowled up with no special baffling all the time. One has been running a DA100 in an extra type plane cowled up for as long as I've been going down to the field (about 4 years). All these guys do is cut holes in the cowling to allow air to flow through the cowling.

I just ordered my first gasser so I kind of need to know.