I have been tuning a new Tower Hobbies .46 with an 11X5 Nextstar red tip prop on it and at one point thought I was ready to go fly, however I was running a little hot at 340 degrees. I use 10% Wildcat Extra and was turning 12,500 RPM and blowing 65 MPH wind six inches behind the prop. I pointed it up at wide open throttle, pinched the fuel line and rpm's increased. I then came to idle still pointed upward and slow to moderatly advanced throttle the way I would if I were flying, she sputtered and went dead. In an effort to catch it I brought the throttle back to idle but it was useless, the flame was extigused. I sat it on the table and backed the low speed needle out 1/4 turn, recranked and now at half throttle it sputters and would scare the bejebies out of me if I were flying. I put the LSN back to where I was getting good transition, Rechecked and richened the HSN but temp was at 386 degrees, and RPM's were at around 12,000. I let the engine cool, put a hose to the carb, sprayed it with dishwashing soap and water and blew till I was tuning green, and could not find a leak. So now, am I too hot, wrong prop wrong fuel, or what? Oh yea, I am flying an Explorer, a 65 inch top wing trainer with symetrical wing and weighs in at 5.5 pounds. Thanks for you help.

Trav

You should be measuring the temperature around the glow plug

I would think anything over 300 would be getting hot.

The engine may need more running yet?

I will agree with the running hot issue, just trying to figure out why.

Trav

My Tower 46's had a rich mid range when the high speed needle was set correctly for wide open throttle

They never quit on me

Maybe I am being a little too careful. I removed the engine so I could check it really good for air leaks, found nothing. I can live with the rich at mid-range because it is just a little studder going through that and maybe when I reasseble the engine with sealant the problem will be gone like something wasn't sealing somewhere, although all seals and gaskets looked good. This engine is not going to last long getting 386 degrees I know, but I've got a 2 or 3 year warrenty at tower. Anyhow, thanks for letting me bounce ideas off and sharing with me.

Trav

Trav,


An IR thermometer photo, is probably what I would put next to a dictionary definition of 'booby-buy', as far as model airplane engines are concerned...

It 'lies' to you frequently and anything it is claimed to be capable of telling you, can easily be determined without it.


If your engine is set slightly rich of peak (i.e. it can be leaned further, increasing RPM), it is at its proper operating temperature; regardless of what its numerical value actually is.


And frankly, if using such a device 'determines' any point on the air-cooled outside of any sport glow engine is at 340ºF; and the engine is running properly, at a smooth two-cycle, it is faulty for sure (the IR Thermometer; NOT the engine).

Can you describe this a bit more? Did it cough, belch a bunch of smoke and quit or did it sag/hesitate and die? The first is a rich low speed needle and the latter is lean.

w8ye is most likely right about the engine needing more breaking in. Carb air leaks usually either make the engine difficult to kill with the throttle closed or cause the engine to run leaner, not richer.

After it's run in some more you can try a new OS A3 plug, too, which is a bit hotter, I think, than the Tower plug.

David

Yes the OS A3 is slightly hotter and my Tower 46 won't run good without it. Mine also does not like an 11 inch prop and runs much better and more consistent with a 10X6. With a 10X6, an A3 plug, and 15% Omega fuel it transitions very good and has never died. With an 11X6 and a Tower plug it would die in flight fairly often. I bought the engine used (less than 10 flights) and the reason he sold it was because of the quitting in flight. The 11X6 and Tower plug came with it and after flying it a few times I started changing things until I wound up at the configuration listed above and now feel it's a decent engine but I do have others in this size that are better. I hope you get yours figured out.

Edited for punctuation.

I measured the rpm on one of my tower 46's with a MAS 10-6 and it was turning 14,400

Regarding the I-R device, the blue anodize of the head may be throwing off the emissivity of the aluminum head?

If the engine runs good there is nothing wrong with it. I can tell if they are hot by the smell and looking at them when they quit. I don't use the I-R gun

Everyone else has addressed your overheating issue properly.

What I want to know is who sells your model? It sounds interesting because of the 65" wingspan, fully symmetrical airfoil and the very low weight. TIA


Ed Cregger

Ed, the plane has a wingspan of 65 inches, one degree of dihedral, wing area is 744 sq. inches and a body length of 49.2 inches. With movement total of 30 mm on aileron, 40 mm on elevator(I probably only use 20mm, 10mm up and 10mm down) and 50 mm on rudder this plane is a blast to fly, sort of a pattern trainer I guess, because it flys turns and spins straight as an arrow. I do 8-point and slow rolls, Cuban eights, inverted spins, Immelman turns, knife edge, avalanche, box and hexagons, snap rolls, hammerhead stalls, one guy at the field said I wouldn't be doing that long because the plane was not made to withstand the stress, he may be right. I only have the build sheet and it does not say who made it, only Explorer-40. It did tell me how to put the wing between two chairs with a fifty pound weight in the center to test spar strength before flight, and I beefed it up some with 3/8 inch oak round stock. Anyhow, don't get me started! As for my running hot issue, the muffler was hitting the fuselage a little so I clearance it, put it back together and she is purring at 12,500 RPM within 300 to 320 degrees at WOT pointing the lazer directly at the glow plug, transitioning nicely basically running as I would expect. Guess I ran across and inadvertantly corrected a sealing problem, guess I will try an A-3 plug, 10X6 prop and 15% Omega sometime to see if I can get into the 14,400 RPM range, but for now I am happy with 12,500 RPM on the ground and probly 1500 RPM more in the air would you say? What would you say?

Trav

The Tower 46 can run very good

I have no experience with the Tower .46 engine, but from what I've read, it does sound to be down on the expected rpm. Maybe Bax will jump in here with an idea or two.


Ed Cregger

He's running a 11 X 5 Nexstar prop so he's not doing too bad

1/4" adjustments are HUGE adjustments,so be careful with that. And it surprises me that your temp claimed to increase when running richer,it is supposed to drop because the added oil going into the engine should cool it more. With some engines....when you lean the low,you must richen the high a little to even it out(dont ask me why) and vise-versa. This means that sometimes when you adjust one setting it affects the other. This tends to really stump some people when tuning engines,particularly the cheaper ones that people claim cant be tuned. This may be the case with your engine. So,just keep this in mind when your tuning.

Also,I like to put a small piece of fuel tubing around the needle valve to help prevent difficult to find air leaks around the needle valve threads that you might not notice. This seems to work wonders on some engines too.

The reason why I was running an 11X5 prop is because I was having to take off from a new grass runway which was mud and water through December and I didn't want long roll outs. Now (Jan. 24) the grass has covered the runway and holes filled with sand to level. I just came from Hobbie Town with two balanced and reemed wood MAS props, an A-3 glow plug and a gallon of 15% Wildcat Extra, tomorrow I'm going to fly and see if I can get the same RPM's as w8ye! I wonder though, is there any voodoo involved like bee's wax? Thanks!

Trav

Trav,


Do yourself a big favor and trade that IR thermometer to an R/C car user, who may have slightly better uses for it, or get in trouble instead of you [>:]...

Just keep away from that POS, for your own good!

Your problems are because the infrared tempgun needs to be calibrated. Take it outside to a safe place and place it on top of a pole. Go back to a distance of about 60 feet and bring out your BB-gun, .22lr or bigger (shotgun works too) Start shooting at the temp gun, when it falls down from the pole the callibration is completed

My temp gun doesn't worry me about accuracy, and it has been helpful in finding A/C trouble and full size engine problems, I am a Master Mechanic by trade. Usually the people who do not like IR temp guns are the ones who do not know the value of one or how to use one. It helped me this time to stave off an air leak which would have fried and flaked my piston and liner eventually. All I can say is it is a constant reading, more accurate than you can feel or smell, if I shut my engine down and wait thirty seconds to check it, the temp will have dropped 100 degrees, how much more do you think it drops comming in and then taxiing to you? If it goes up beyond what I can control with richening, I ain't flying y'all. Speaking of R/C car people, at the hobby store last night there were people who were wrapping aluminum foil around their engines to hold in heat and get the temp around 140 degrees, I didn't have my gun but will next time and I am taking it to the flying field today to shoot other people's engines and see what they are getting. I appreciate your advice Darzeelon and Asmund, you seem really informed, but I will keep my temp gun.

Trav

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Oops! I missed that. That would explain it.


Ed Cregger

I have a Tower .46 in a Sig Senior, running a 11x6 Zinger, on 10% nitro, castor/synthetic blend. Engine likes the prop fine has been very reliable. Oh, I'm at 1700'.

CR

Edit: Let me remind you that the Tower .46's muffler is really a mini-pipe and you have to set your hi-spd needle accordingly.

Charley, I dont mean to be stupid, wait a minute, cancel that! How do you set your high speed needle? I just came from the field and it took a lot of encouragement to get the Tower .46 to fly reliably, but when I got it man alive, she flew like a champ with an 11X5 prop, it sounded like it was over-reving in the air. I don't know what you think but I am going back to the 11X7 prop to make the plane jump up off the ground and it will still turn 11,000 RPM'S at around 320 feet above sea level, slow and Harrier just fine. I never should have experimented with different props but you never know until you try.

Trav

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For most people, the problem isn't the IR thermometer. It is the lack of baseline information regarding the proper operating temperatures of our model engines. There are tons of variables, as I'm sure you know. Even such mundane things as the type of glow plug, fuel, prop selection, needle tweaking and the cooling environment in which the engine resides can all seriously affect our engines. It takes a lot of previously learned knowledge in order to know how to use the information that the IR thermometer provides. Many folks coming to the RCU engine forums are newbies that are bewildered by what they discover thermally about their engines. That is why many of us recommend forgetting about the IR thermometer until folks have more operating experience with their glow engines.

Many glow engine traits and characteristics vary quite a bit from traditional automotive engine traits and characteristics. I've seen many a good auto mechanic humbled by the lowly two-stroke glow engine in my time. I also know a few master level auto mechanics that are quite good at handling their model glow two-strokes, but many will admit that there is very little crossover between automotive training information and the practical use and maintenance of glow engines. Of course, many auto mechanics got their first engine experience handling model glow engines. I did. I was once a fair automechanic, but couldn't continue working in the field because of not being able to work over my head. Damage from polio made working overhead very painful.

I fail to see the usefulness of the IR thermometer in many applications. A thermocouple with an RF link to a laptop would be much more useful. I do see the use of an IR thermometer in troubleshooting A/C systems, automotive or otherwise.

I hope you get it all sorted out satisfactorily (Tower .46) and all is well. I'm sure it will be.


Ed Cregger

Hello Travhit:

Does this look like your plane?

http://www.nitrorcx.com/trex40nigasr.html

Bye, Ian

Thanks Ed, I am going to take everyone's advice and leave my IR gun at the house. I've got it set now to take off from about a 15 foot run using an 11X7 prop. It will pull vertical till you can't see it anymore and will stay up for more than 15 minutes on 8 ounces of fuel. I do not know what people are doing to get close to 14,500 RPM's out of this engine, but I was unsucessful using the same 10X6 MAS wood prop, 15% Wildcat Extra and an OS A-3 glow plug, all I could get was 13,300 RPM. My hat is off and I am humbled by you w8ye! By the way, I am turning 11,400 with a 11X7 ASP, 12,900 with a 11X5 Nexstar Select all on 15% Wildcat Extra, I didn't get the chance to try the 11X6.

Trav