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07-23-2006 05:35 PM  14 years ago
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starstructure02

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Trinity, Florida USA

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Question about a .37SZH
Hello all,
I'm having a problem with the temp of my .37OS in a hawk pro.
From the beginning I have never been able to get the motor to run cool. Right now I can't keep my finger on the back plate for more then a second or 2. Based on what boiling water feels like I would say the motor is close to 200 on the back plate which I know is too hot.

A few things, One I have an excessive amount of micro air bubbles in the main tank and know this would make for a lean mixture. I installed a header tank that helps as long as the main tank is more then 1/2 full but after the micro bubbles show up in the header tank as well. I heard someone else had this problem and after installing the constant tail drive option it seemed to get rid of the bubbles.

Second, There is oil coming from between the head and cylinder case on the engine. It is dripping inside of the canopy. I took the head off and see that there is a slot on the lower side of the cylinder. I am assuming that this is a place for excess oil to collect and then drip out. Is this correct?

I have run this motor to the point that it’s so rich that I can just barley hover. After about 1 minute of running the motor is still to hot too touch for more then a second or 2.

I seem to have plenty of smoke. I live in central Florida, so low altitude and high humidity.

I can get the copter to fly good with plenty of power, I’m just concerned that I’m burning this motor up. I have cut hole in the canopy to get more air flow.
The motor has about 3 gallons run through it so it’s broken in. (note although during the break in it always ran hot)
I am running 30% with 18% oils purple in color.
My pitch curves in idle 1 is -6 / -2 / +2 / +6 / +10
My throttle curves are a work in progress (I do have the throttle linkage set up right with 100% ATV and the carb barrel in the middle of travel at 50 % stick) I can’t seem to get my head speed at a happy medium because I haven’t been able to get a stable mixture. When I take off it's good but after a few minutes of flight my head speed can vary as much as 400 RPM's.
TIA,
Mike

PS. I just wanted to add that when I first got the copter together and was tuning the motor I followed the directions. With the motor set from the factory I began by hovering the model. It was very rich with the factory settings. I then had to close the idle mixture screw to get the copter to hover clean and have good power in forward flight. I then made small adjustments to both the idle mixture screw and needle valve. I did manage to get the model to fly nice and smooth with plenty of power just always ran hot.
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07-23-2006 06:21 PM  14 years ago
Al Austria

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Sacramento, CA - USA

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200 degrees is not too hot. Quite the contrary it's right around where you want to be with a 30 size engine. However, I would not gauge the temperature with my finger because 2 seconds is not long enough. What is your main needle setting and the idle setting relative to the factory position? The main needle on an OS 37 should be somewhere between 1 to 1.25 turns out. If you're gettting bubbles in the main tank, try richening your idle mixture because it is probably too lean.
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07-23-2006 08:28 PM  14 years ago
MikeInMobile

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Mobile, Alabama

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The bubble in the tank (and fuel line) is the reason that the engine temps run hot. Try using a 2oz header tank to reduce the bubbles in the fuel system. The header tank, properly isolated, will remove the air from your fuel supply, making engine adjustments a lot easier and more accurate. The bubbles lean out the engine. Since the flow of the bubbles is not constant, the mixture leans out, then richens up.

I have found that header tanks are almost a requirement on these Hawks unless you get them TOTALLY vibration free, which is almost impossible. These machines are extremely light and are susceptable to vibration issues.
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07-23-2006 10:30 PM  14 years ago
starstructure02

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Trinity, Florida USA

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Thank you guys for your input, I do have a header tank and it's insolated pretty good. I notice that after the tank gets below half I start to see micro bubbles building in the header tank as well. The copter seems to fly very smooth, I'm at a lose to understand how to make it smoother. It hovers like a rock. Like I said it flies and hovers very nice it's just running hot At least as far as I can tell by holding my finger to the back plate. Now I want to add that I have flown for 10 minutes in basic flight and never had a problem with the engine cutting out so...........I do want to also note that when in foward flight and I put it down and check temp with my finger it's a little cooler but there is no way I could hold my finger there for up to 4-5 seconds. 2 at the most and it's hot.

Anyway my main needle is right at 1 3/4 turns out. Based on what your saying I'm a little rich. My idle mixture needle is about a 1/2 turn IN from the factory setting. At the factory setting it was way to rich to the point that I could not get any RMPs or power.
Is there any other reason that this motor would run hot.
Mike

PS. does anyone know what the back plate temp should be on this motor. Also has anyone found those bubbless clunks to work. http://www2.towerhobbies.com/cgi-bi...p?&I=LXXF25&P=Z
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07-23-2006 10:58 PM  14 years ago
Al Austria

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Sacramento, CA - USA

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Anyway my main needle is right at 1 3/4 turns out. Based on what your saying I'm a little rich. My idle mixture needle is about a 1/2 turn IN from the factory setting. At the factory setting it was way to rich to the point that I could not get any RMPs or power.
Your main needle is so far out that you had to lean out your bottom end to compensate and that is the sole cause of your bubbling tank. If you do a search you'll find that in most cases, a lean idle mixture will cause a Hawk/Falcon/Raven tank to bubble. I'd say lean out your main needle to about 1.25 turns out and reset your idle mixture back to the factory setting. Your idle mixture might be a bit on the rich side so it might need some leaning out but it shouldn't take anymore than a 1/4 turn in from the factory setting. The key with the OS 37 is that you have to set the idle mixture rich to the point to where you need to finesse the throttle to keep the engine from dying when spooling up. Usually a hotter plug will help with this. I run an Enya #3. My OS 37 runs just warm with amazing power and the fuel in my tank hardly moves at all.
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07-23-2006 10:59 PM  14 years ago
MikeInMobile

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Mobile, Alabama

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The bubbles are caused by high frequency vibrations in the airframe. To help to remove them, balance the fan and clutch before mounting them to the engine using a high point balancer. The clutches are usually the culprit with the high frequency vibration and can be balanced using a small pin drill. Once all of the components are perfectly balanced, mount the fan and clutch and check for runout in the fan. The runout should be minimized to further reduce the high frequency vibration.

Most of the vibration on these Hawks comes from the engine, rather than from the rotating mass. Engine vibration is a high frequency, so you will not usually see it, but you can feel it bl holding the back of the tailboom firmly ..... you will be able to feel the vibration!
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07-24-2006 12:11 AM  14 years ago
starstructure02

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Trinity, Florida USA

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Al,
I just got back from doing what you said. All I can say is thank you for putting me in the right direction. I have the main needle set to about 1 turn out and the idle mixture is about a 1/2 turn OUT from the factory setting. You were right the bubbles in the main tank although not totally gone are much less. Also, the motor is running much cooler now. I still can't hold my finger on the base plate as long as some say but I can hold it for 2-3 seconds I would say about 10 to 15 degrees cooler. Now I need to reset my pitch curves and throttle curves for sure. It seems that I have more power at mid stick and the rotor speed has increased with my present pitch / throttle curves. I'm sure once I set my curves right I'll get the motor temp down a bit more, I‘m over pitched, the copter was hovering at ¾ stick now it‘s hovering at just over ½ stick. Also, I'm just hovering right now, goosing the throttle and watching it climb out. I'm sure that the motor will naturally run a little hot as apposed to forward flight. I’m getting more smoke out of the pipe, more like what I see out at the fling field from other copters.
Al, Thanks again,
Mike
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07-24-2006 12:52 AM  14 years ago
Al Austria

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Glad that you got it sorted out.
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07-24-2006 01:32 AM  14 years ago
starstructure02

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Trinity, Florida USA

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Al,
I'm new to nitro helis, obviously. I've been fling electric from the beginning. This is my first experience with tuning a heli engine. I've also just started fling nitro planes as well. The plane engine was a piece of cake to get running right. The heli engine now that I've taken your advice is pretty easy to understand as well. My point, I started to tune the engine just like the instructions said. Basically they say to begin by setting the idle mixture screw first. Since the main needle valve was rich to begin with, I had to lean out the idle mixture to get the copter running right….right???. Then they say to finish up with the needle valve which I did. Like I said, the motor ran good but introduced bubbles in the system and resulted in a hot running engine, both of which could have resulted in a dangerous situation. As a newbie I was very reluctant to go the other way with the needle setting. To be honest in never dawned on me to do so.
Point of this is I most likely took some life off this engine by running it hot all this time and that really sucks. Other then places like this how does one find out how too set these things up correctly. Just my 2 cents.

Thanks again Al and Mike in Mobile for your help.
Mike
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07-24-2006 01:57 AM  14 years ago
Al Austria

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Sacramento, CA - USA

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The OS 37 is a little strange when it comes to tuning. When I broke in my first one I was surprised how lean it needed to be to run well. Most OS engines needles need to be set around 2.5 turns out for break-in and usually land between 1.5-2 turns fully broken in. The OS 37 at most needs its needle to be 1.5 turns out with the factory set idle mixture in order to even spool up. Fully broken-in the OS 37's main needle should land between 1-1.25 turns out depending on the idle mixture setting. One thing to watch out for is that its rear bearing is prone to failing (kinda like case with the OS 50's). If your engine one day starts idling poorly and makes a new noise, check your rear bearings ASAP.
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07-24-2006 03:30 AM  14 years ago
perfesser zero

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Dublin, VA., USA

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OS .37 and tuning...
Thanks guy's, you've just answered all the questions I may have had on this engine. I just bought one and needed to know all this. Hope to have it ready by next weekend and try it out in the Hawk Sport. As for now it's replacing a Toki 40 that lost a crank last weekend. That'll go into the Raptor 30 that I have now once it's fixed.

Later...

Scott!
Tiger 50 - OS 50SX-H
Hawk Sport - OS 37SZ-H
Raptor 30 - OS 37SZ-H
JR 10X/R950S
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07-24-2006 05:29 AM  14 years ago
BC Don

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Calgary, AB Canada

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Well, I had my OS37 running really well. But with the last crash it ran wild at full RPM for a couple of minutes (the battery and Rx had been "removed" from the Heli in the crash). By the time I got the Heli it had stopped.

My compression is way down and in taking the engine apart I can see a pretty good series of score lines along the liner and piston and the ring has been sorta siezed in place by the scoring. So I'll have to check on the price of a new sleeve, piston and ring.

In the meantime, I'm putting the TOKI in to see what it'll do.
Got Money? Send it to me, I'm a Heli Addict.
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07-24-2006 11:05 PM  14 years ago
starstructure02

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Trinity, Florida USA

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Hello all,
I just want to come in and say I got out to my flying field today and played with the mixture settings and the pitch and throttle curves. I got it pretty good and am much happier with the performance.
I ended up with the idle mixture set at about 5/8's of a turn OUT form the factory setting and on the needle valve about 3 clicks open from one full turn. After completing about 6 minutes of basic forward flight I landed to check temp on the back plate. I could hold my finger for about 4 seconds with no problem. I’m thinking that’s pretty good. I know I’m probably on the rich side, but that’s OK for now. One thing that happen today, after the first flight I was coming in for a landing and I noticed that I was loosing power in the decent. I was able to land and when I back off the throttle the motor just died. I was confused. The back plate was very hot and to say the least I was pissed. I went to start the motor again and no compression. Again pissed !! To make a long story short I found that the center pin on the glow plug was loss and there was the compression loss problem. What a relief !! Anyway I still need to fine tune the throttle curve but I think I’m on my way to understanding this nitro thing a lot better. Thanks to all for your input.
Mike

PS. Personal note: As you all know the Pro Hawk comes with some pretty crummy decals, I didn't want to paint out the canopy until I got more confidence with flying so I did some custom decals check it out.

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07-28-2006 03:17 AM  14 years ago
perfesser zero

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Dublin, VA., USA

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Ahhh, Dude!!!
What's with those Futaba decals? Just joshing yah. Fly what you like. I prefer JR, but to each his own. I do however use Futaba servos and I also use two (2) 401 gyros and 9253 servos. Now having said all that, I got my new OS .37 this afternoon and have mounted in the vacant place that used to house the Toki. I'll fix that up and put it in the Rappy 30 later. I hope the OS .37 will do me as good as the Toki (minus the broken crank). We will see this weekend. I'll be breaking it in for the next few flights so I don't expect allot out of it, but I'm excited about seeing how it performs.

Later...

Scott!
Tiger 50 - OS 50SX-H
Hawk Sport - OS 37SZ-H
Raptor 30 - OS 37SZ-H
JR 10X/R950S
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07-28-2006 04:05 AM  14 years ago
starstructure02

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Trinity, Florida USA

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Perfessor,
What can I say I own a sign shop and had nothing to do one day so I scaned a set of futaba decals and made some up. I have to sat that I got the 37 running really good. I was out today with a few guys that have Hirobo 50's and we were doing some pull outs from a hover and the 37 did ok. I got my Throttle and pitch curves just right and what a differance. I'm loving it. This Centruy pro Hawk has it's problems but I'm happy with it as my first Nitro copter. I just brough a 50 EVO off of e-bay like new with all the bling.
Mike
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07-28-2006 04:28 AM  14 years ago
perfesser zero

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Dublin, VA., USA

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starstructure02...
Evo sounds sweet. I may end up with one someday, but I more than likely will go with a Raven or Falcon next, but only if I destroy something. Which I hope doesn't happen. I hate repairing these things. It's much more fun to fly them and then just hang them back up in the trailer and take them home in one piece.
What head speed are you running on your Hawk. I've got CF's on the mains and the TB upgrade on the head so I'm not afraid of high head speeds, but I don't want to go 'ridiculous' on the head speed either. I've been running my Toki around 1750 or so (I think...sounds like it) in idle up 1 and I'm moving on to a V curve type of setup soon on all my helis. I'm taking the plunge and go with the flow even if I can't do any actual 3D yet. I can do some mild stuff on the Sim...but!

Later...

Scott!
Tiger 50 - OS 50SX-H
Hawk Sport - OS 37SZ-H
Raptor 30 - OS 37SZ-H
JR 10X/R950S
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