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HelicopterMain Discussion › Main needle for 37SZ-H
10-09-2005 11:16 PM  12 years agoPost 1
Helibras

rrApprentice

São Paulo, Brazil

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Hi guys. I’m breaking in my lovely 37 SZ-H and setup needle valve to a point that I could let my finger in back plate for long time but with engine showing some power (good power actually). Then I made the 2 first flights with it always checking temperature and doing small adjustments.

When I got home I checked the settings and found out that was only 1 1/8 turns opened. Doesn’t seems to low to you?

Ricardo


Gravity... the force to be defeated
Raptor 50SE; Hyper
Vigor CS; OS 91C-Spec MPII

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10-09-2005 11:55 PM  12 years agoPost 2
BarracudaHockey

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Jacksonville FL

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Whatever works for your combonation of fuel/pipe/gearing/altitude etc etc etc. If its not running hot your fine.

Andy
AMA 77227
http://www.jaxrc.com

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10-10-2005 12:01 AM  12 years agoPost 3
Helibras

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São Paulo, Brazil

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Would't be better to run it a little bit richer with a less powerfull engine for some flights? What would be the best running in setup?

Now it is going up pretty fast but still sounds rich

Ricardo


Gravity... the force to be defeated
Raptor 50SE; Hyper
Vigor CS; OS 91C-Spec MPII

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10-10-2005 12:05 AM  12 years agoPost 4
BarracudaHockey

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Jacksonville FL

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Running slightly rich is fine, running cold really isnt good for the engine and a waste of fuel. Running too rich will also give your gyro fits.

Lean it till its warm and you should have decent smoke and good power.

Andy
AMA 77227
http://www.jaxrc.com

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10-10-2005 12:42 AM  12 years agoPost 5
SkateFreak

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Cambs UK

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Hey,
That could explain y my heli was near impossible to fly 2day...
Have been flying with my OS32SXH cold to the touch (dont ask why lol)
And leaned her out a little today, and by golly this engine has more power than i remember *grins*

But yeah, i usually run slightly rich myself to be safe

-Jvr

Ps, how can running over rich damage the engine??

Non-3D heli pilots are planker spys trying to bring down the heli community from the inside - Topher

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10-10-2005 04:26 AM  12 years agoPost 6
Helibras

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São Paulo, Brazil

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"Running slightly rich is fine, running cold really isn’t good for the engine and a waste of fuel. Running too rich will also give your gyro fits"

That is what the experts here told me. Good to know they are up to date with engine tech.

"Ps, how can running over rich damage the engine??"

My guess is that when the engine runs cold there is too much pressure on the ring and piston because liner dilates more.


Gravity... the force to be defeated
Raptor 50SE; Hyper
Vigor CS; OS 91C-Spec MPII

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10-10-2005 05:08 AM  12 years agoPost 7
dkshema

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Cedar Rapids, IA

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If the engine doesn't get up to a decent operating temperature, the break-in period will be very long. The 32 SX-H is an ABC engine (I think it's actually ABN), and depends on the very tight fit of the piston crown in the liner at the top of its stroke for compression.

The piston in a ringed engine is a much looser fit in the cylinder, and the ring is the guy who is responsible for the compression.

If you don't run the ABC/ABN engine up to normal operating temperatures, it may never break in properly, and you may actually lose that tight seal and compression.

The ringed motor likes to be broken in by going through numerous cycles of being leaned out briefly, then richened back up to cool down. In this case, you're lapping the ring and cylinder (which was probably honed with a cross-hatch pattern) as you run the motor. The repeated thermal cycles allows the ring to seat without seizing and breaking.

The following is from the website of the Model Engine Company of America (MECOA). It's title is "How to break in an ABC engine":
First of all you really don't want to "BREAK-IN" an ABC engine in the classic sense. An “ABC” type engine (Aluminum, Brass, Chrome) does not require prolonged break-in periods. However, we do recommend that you run the engine at a slightly rich needle valve setting for the first two runs. These runs should be made with the engine installed and running for not less than five (5) minutes periods. Typically an engine will be ready for continuous full throttle and a leaner needle valve setting after ten (10) to fifteen (15) minutes of running.

ABC engines are designed to run at operating temperatures, NOT COOLER temperatures. RUNNING THE ENGINE TOO RICH WILL RUIN THE FIT. If the operating temperature is not reached, the piston is prematurely worn from lack of clearance. You do not want to "break-in" an ABC engine at a very rich setting. Just a slightly rich setting for the first 30 to 45 minutes of running is adequate.
And this from the same website titled "How to break in a ringed engine":
A Ringed engine requires more break in than an ABC engine and in turn usually lasts longer and takes more abuse than an ABC engine.

The ring, which is usually made of an iron alloy must be mated to the hardened steel cylinder liner. The mating surfaces of the ring and cylinder must be perfect to create the proper seal. Many other factors are important too, like the piston fit and the quality of the ring and groove as well as the finish in the cylinder bore. If anything is not made correctly no amount of break in will correct the problem... ... The initial bench break-in period is approximately 90 minutes (40 to 45 minutes bench and 45 minutes airborne). During this time, use the recommended break-in propeller and run the engine at a rich setting. It is best to run the engine for about 10 minutes, then allow it to cool. The heating and cooling aid break-in on a ringed type engine.
The full text is found here:

http://www.mecoa.com/faq/breakin/breakin_abc.htm
http://www.mecoa.com/faq/breakin/breakin_ringed.htm

Dave

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10-10-2005 10:31 AM  12 years agoPost 8
SkateFreak

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Cambs UK

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Hey dkshema,
Thanks for the awsome post
Learn something new every day

-Jvr

Non-3D heli pilots are planker spys trying to bring down the heli community from the inside - Topher

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10-10-2005 01:50 PM  12 years agoPost 9
BarracudaHockey

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Jacksonville FL

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What he said.

Andy
AMA 77227
http://www.jaxrc.com

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10-10-2005 02:28 PM  12 years agoPost 10
airdodger

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Johnston USA

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If you run the engine too rich the liner does not expand properly and causes the ring and piston to (wear in ) improperly. I disagree with the statement that a ringed engine will last longer and takes longer to break in. I have had ABC engines go over a hundred gallons, never even came close to that with a ringed engine. If you overheat a ring, just once, it loses tension and then the seal goes, and causes power losses. The liner is definitely honed with a crosshatch, that is what holds the oil. The thermal cycles have to do with the block taking a set. We used to change the rings after about 75 minutes running time in the racing two cycles, and they were losing seal then. Rings break in quickly. Chris

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10-10-2005 02:39 PM  12 years agoPost 11
Burgunder

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pittsburgh

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I am breaking the exact same engine. I have about 1 gallon through it. I am running mavrikk 550s and a head speed of about 1750 with cy30%. Yesterday, I had 3 flights. I can keep my finger on the back plate forever. I measured the base of the head with a temp. meter that is on my voltometer. It has a wire that plugs into the meter itself. It read 170 after numerous climb outs. The rate of climb is great. My needle is right around the 1 1/8 mark. I have read that some people have gotten it down under 1 turn under sertain conditions when completely broken in. Just keep it warm, not cold and certainly not hot. But, the 1 1/8 is right were I am. I will continue to lean it as it breaks in. Also, I have to say that I am very impressed with this engine. It replaced a non ring 32, and already has tons more power. I have found it very easy to break-in and tune even though I only have 1 gal through it. Great engine.

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10-10-2005 10:32 PM  12 years agoPost 12
SkateFreak

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Cambs UK

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Okay,
So ABC engines last longer right?
But then are there any 50/70 size ABC's out there?
Surly OS's are ringed?
Is it just me or would it seemt to be more benificial to have an ABC 50?
Or do ringed engines give more power?

Its amazing, the more you read into this the more complicated it gets

Loving it,
-Jvr

Non-3D heli pilots are planker spys trying to bring down the heli community from the inside - Topher

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10-10-2005 11:11 PM  12 years agoPost 13
Al Austria

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Gainesville, FL

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When I finished breaking in my OS 37, my main needle was 1 turn and 1 click out. Ran warm and strong. I'd say around 1 turn is normal for the 37.

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10-10-2005 11:22 PM  12 years agoPost 14
dkshema

rrMaster

Cedar Rapids, IA

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ABC's don't necessarily last longer, or vice versa. Longevity has a lot to do with how you treat the motor.

ABCs are not very forgiving of a lean run. It's extremely easy to score the piston and cylinder rendering them useless with a lean run. Ringed engines are a bit more forgiving in this regard.

If you look at the specs of the OS 32 SX-H ringed and non-ringed versions, they HP produced and all other performance specs are the same.

Dave

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10-11-2005 01:05 AM  12 years agoPost 15
Helibras

rrApprentice

São Paulo, Brazil

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But, the 1 1/8 is right were I am. I will continue to lean it as it breaks in
When I finished breaking in my OS 37, my main needle was 1 turn and 1 click out.
Great to hear that from you guys. Thanks for feedback!!

Ricardo


Gravity... the force to be defeated
Raptor 50SE; Hyper
Vigor CS; OS 91C-Spec MPII

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