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Old Oct 28, 2012, 01:37 PM
I HATE GLOW PLUGS!
SrTelemaster's Avatar
United States, NY, St Lawrence
Joined Feb 2012
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Keep in mind that a pushrod housed in an external tube like an OS 4-stroke or Harley Davidson "V" twin will not get as hot as the cylinder/head that is containing hot combustion gases. (or pushrods housed internally)

Even when running aluminum pushrods (W/a higher expansion factor) W/cast iron cylinders in the old pre-Evolution Harley Davidson engines, valve lash, when using solid lifters, was esentially set to .000" when cold. This was accomplished by setting the lash adjustment so that the pushrods would spin W/slight drag between the fingers.

As long as there was .000" or more lash when cold, the differing expansion of the hotter cylinder/head compared tom the pushrods, would increase lash over the cold settings. Minimal lash settings are to asssure complete closing of the valves until opertaing temperture is normalized.

Modern hydraulic lifters keep lash @ .000" throughout the temperture envelope.
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Old Oct 28, 2012, 01:38 PM
Complete RC Idiot Savant
The Netherlands
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I never measured it, I just do know from experience that there is usually a little bit "spare" in the valve clearance, before they really do not close anymore. That "spare" is a few tenths of a mm, and typically the cold clearance for valves that size is 0.9 to 1 mm.
Those engines are made of steel, not aluminium, so mechanical valve clearance does not change as much due different expansion from aluminium and steel

The 3 mm over 0.5 metre @ 400 degrees sounds pretty normal, but exhaust valves usually do not expand that much, or you would not get away with a valve clearance of 1 mm on a valve of approximately that length and an operating temperature of between 300 and 400 degrees.

Engines built of all steel do not open up their valve clearance when they heat up, like aluminium engines with steel pushrods do.

Brgds, Bert
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Old Oct 28, 2012, 01:52 PM
Complete RC Idiot Savant
The Netherlands
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Quote:
Originally Posted by SrTelemaster View Post
Keep in mind that a pushrod housed in an external tube like an OS 4-stroke or Harley Davidson "V" twin will not get as hot as the cylinder/head that is containing hot combustion gases. (or pushrods housed internally)

Even when running aluminum pushrods (W/a higher expansion factor) W/cast iron cylinders in the old pre-Evolution Harley Davidson engines, valve lash, when using solid lifters, was esentially set to .000" when cold. This was accomplished by setting the lash adjustment so that the pushrods would spin W/slight drag between the fingers.

As long as there was .000" or more lash when cold, the differing expansion of the hotter cylinder/head compared tom the pushrods, would increase lash over the cold settings. Minimal lash settings are to asssure complete closing of the valves until opertaing temperture is normalized.

Modern hydraulic lifters keep lash @ .000" throughout the temperture envelope.
I am not a harley mechanic, nor a harley enthousiast (In my humble opinion, those engines are very strange and illogic contraptions) but that would be the first time that I hear from an engine that needs to have 0 lash when cold. Could have something to do with the abnormal pushrod length though.

Anyway, virtually all other engines need a positive valve clearance.

But that is not the point, what harleys need or not need.

My valve clearance is OK, of that I am sure.
My valves are not leaking, but my OS is running slightly hot....
It keeps running OK, did another 30 miutes this afternoon before the cold drove me back home.
I am getting the impression that the 15% oil is slightly too much, but I am not sure if I want to change it.... it is kinda convenient to have the same fuel for all engines (gassers excepted), but I think I will at least go to 0 Nitro, as the two-strokes don't need it, and it will facilitate leaning out a bit more, reducing the oil sloshing around in the fourstroke a little bit.

Now for to improve cooling.

Anyone knows a decent way to get some extra cooling fins on a fourstroke? Not easy to get a heatsink on them like on a 2 stroker.

Brgds, Bert
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Old Oct 28, 2012, 03:44 PM
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We are not saying your problem is valve clearance. You made some statements about valve clearance and how it might change with temperature and the discussion continued in that direction. You said you observed 0.3-0.4mm change in a 500mm exhaust valve except that wasn't the case, you observed that much change in clearance. Some Saito users set their engine to virtually no clearance to get the most power. They claim it's noticeable and that there are no negative consequences.

Wouldn't it be easier to improve flow volume? Do you know if you lost volume while trying to reduce losses in the fan? Maybe an improved engine cowling?

Greg
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Old Oct 28, 2012, 05:14 PM
I HATE GLOW PLUGS!
SrTelemaster's Avatar
United States, NY, St Lawrence
Joined Feb 2012
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The point of using a Harley Davidson engine as an example is that it, like the OS & Saito 4-strokes, has pushrods that are externally situated.

The pushrods do not get as hot as the cylinder & therefore, they do not expand as much. Therefore, valve lash will increase as the engine reaches operating temperature.


Regardless of the material that the cylinder is made of, it will get hotter than a pushrod that is segregated from the cylinder heat. The cylinder will therefore expand more than the external pushrod.
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Old Oct 28, 2012, 05:25 PM
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Quote:
Originally Posted by gkamysz View Post
We are not saying your problem is valve clearance. You made some statements about valve clearance and how it might change with temperature and the discussion continued in that direction. You said you observed 0.3-0.4mm change in a 500mm exhaust valve except that wasn't the case, you observed that much change in clearance. Some Saito users set their engine to virtually no clearance to get the most power. They claim it's noticeable and that there are no negative consequences.

Wouldn't it be easier to improve flow volume? Do you know if you lost volume while trying to reduce losses in the fan? Maybe an improved engine cowling?

Greg
No.... When a Ships propulsion diesel is stopped, it is continuously heated to approximately operating temperature, It is not cooled down, we're not allowed to. We adjust valves while everything except the valves is within 30 degrees of its operating temperature. That is common practice in the industry, and it is according most manufacturers instructions. The few manufacturers that cover cold valve adjustment in their manual, usually state the same clearances for hot and cold condition.

The valve is on those engines actually the only part in the valve train that really changes temperature between running and standstill, so it's more or less the only part that can be responsible for the change in clearance. That and the oil film that is not present when the engine is stopped but there when it is running.

As to the cooling, I am not sure what you are referring to.
Flow volume is determined by the axial cooling fan, can't do much about that
Allready installed some guide vanes that claim to improve efficiency of the fan, it should increase the flow. No idea how effective that is.
I never did anythiing to the fan itself, so I don't think I have lost any flow from that.
No room for improvement in the ducting around the engine unfortunately.
The only thing I can think of at the moment, is increasing cooling fin surface.
Just no idea how to arrange that a little bit elegant as the OS has no nice round features where you can clamp a heat sink or similar.
I have aluminium welding stuff (AL75) but I am slightly unhappy for heating up the engine casting, as I have seen castings warp from this sort of treatment.

Brgds, Bert
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Old Oct 28, 2012, 08:12 PM
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Think of the Harley V-twin air cooled engines being more in common with a radial engine design than other engine types. It behaves more like a radial engine too. You have to warm them up good and get them nice and hot before you try doing anything hard with them. Otherwise they'll blow a head gasket. During warm up from cold to hot the different parts expand at different rates. The engines actually grow in height a considerable amount too. That uneven expansion and contraction tends to wear out the seals on the intake manifold and the gaskets on the valve covers fairly often. Fortunately for quite a long time now HD uses hydraulic lifters, so you don't have to adjust the valves on them.
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Old Oct 28, 2012, 08:17 PM
I HATE GLOW PLUGS!
SrTelemaster's Avatar
United States, NY, St Lawrence
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Quote:
Originally Posted by earlwb View Post
Think of the Harley V-twin air cooled engines being more in common with a radial engine design than other engine types. It behaves more like a radial engine too. You have to warm them up good and get them nice and hot before you try doing anything hard with them. Otherwise they'll blow a head gasket. During warm up from cold to hot the different parts expand at different rates. The engines actually grow in height a considerable amount too. That uneven expansion and contraction tends to wear out the seals on the intake manifold and the gaskets on the valve covers fairly often. Fortunately for quite a long time now HD uses hydraulic lifters, so you don't have to adjust the valves on them.
They also have a lot in common W/our air cooled R/C engines.

Aluminum crankcase, tall cylinder casting W/external pushrod tubes.
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Old Oct 29, 2012, 08:33 AM
The Prez....... again
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United States, IA, Rockwell
Joined Jul 2011
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Bert, what helicopter are you flying? From my past heli experience I know some guys have found improved cooling by purchasing after market fans. Even taking another OEM fan from a different heli and using it.

Zip on over to HeliFreak.com and see what the guys over there have to say. http://www.helifreak.com/

Ken
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Old Oct 29, 2012, 11:00 AM
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Conversions ?

i have made some 27 glow-ignition conversions, classic 30'ies style. The goal was, besides personal challenge to create my own ignition not only running well but good looking as well. There is a small collector market for it. With no profit. But I do not see myself convert good running glow engines to ignition.
I have no problems with these glow engines. They run fine. Why do you guys do it ? You've lost me. I am lost with oil pro's and con's as well.
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Old Oct 29, 2012, 12:08 PM
I HATE GLOW PLUGS!
SrTelemaster's Avatar
United States, NY, St Lawrence
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Quote:
Originally Posted by Reginald View Post
i have made some 27 glow-ignition conversions, classic 30'ies style. The goal was, besides personal challenge to create my own ignition not only running well but good looking as well. There is a small collector market for it. With no profit. But I do not see myself convert good running glow engines to ignition.
I have no problems with these glow engines. They run fine. Why do you guys do it ? You've lost me. I am lost with oil pro's and con's as well.
Easier starting, 23% better fuel economy, more stable idle, more consistant prformance, slightly more power.

NO MORE GLOW DRIVERS TO FOOL WITH. Turn on the switch & start the engine. I use the same type of batteries as my RX so no additional chargers needed.
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Old Oct 30, 2012, 02:17 AM
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Quote:
Originally Posted by SrTelemaster View Post
Easier starting, 23% better fuel economy, more stable idle, more consistant prformance, slightly more power.

NO MORE GLOW DRIVERS TO FOOL WITH. Turn on the switch & start the engine. I use the same type of batteries as my RX so no additional chargers needed.
Never had any trouble with my onboard glowdrivers and the idle of my OS 4cyl 240 is magnificent WITHOUT an onboard. As for fuel economy that's an issue I have never understood and the very least of my modelling expenses, but I suppose you guys do fly day and night ? Fourteen litres in my 911 when driving moderately, now tht's fuel consumption. But please do not let me stop you guys fiddling. But when I want to fly ignition I go for Zenoah or DA or Seidelwhatever purpose made engine.
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Old Oct 30, 2012, 02:50 AM
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Quote:
Originally Posted by kenh3497 View Post
Bert, what helicopter are you flying? From my past heli experience I know some guys have found improved cooling by purchasing after market fans. Even taking another OEM fan from a different heli and using it.

Zip on over to HeliFreak.com and see what the guys over there have to say. http://www.helifreak.com/

Ken
It is a Vario Skyfox based Bell 47G. it has an axial fan, and I think Vario is one of the few, if not the only one using such design. A different fan most likely will not do much, as it is drawing air out of the cooling duct, rather than blowing into it. It works OK, but I have the feeling, that changing the fan does not help much as the engine is "blocking/restricting the airflow"....
I am trying to channel the air a little bit better around the engine, but have not yet flown with that (bad weather over here)

Quote:
Originally Posted by SrTelemaster View Post
Easier starting, 23% better fuel economy, more stable idle, more consistant prformance, slightly more power.

NO MORE GLOW DRIVERS TO FOOL WITH. Turn on the switch & start the engine. I use the same type of batteries as my RX so no additional chargers needed.
Yes.... that is a great thing.... I am flying gassers as well and there it came naturally, but with this helicopter, after close to 2 weeks of flying, I still unvoluntary look for the glow cable to disconnect after starting.... it is not there
The charging is not the point (it is in fact a bit of extra hassle, even with two NiMH, just because you have to charge the same helicopter twice)

But the consistent running and reliable idle (we have sometimes a long walk from pits to helipad) are a real relief.

Quote:
Originally Posted by Reginald View Post
Never had any trouble with my onboard glowdrivers and the idle of my OS 4cyl 240 is magnificent WITHOUT an onboard. As for fuel economy that's an issue I have never understood and the very least of my modelling expenses, but I suppose you guys do fly day and night ? Fourteen litres in my 911 when driving moderately, now tht's fuel consumption. But please do not let me stop you guys fiddling. But when I want to fly ignition I go for Zenoah or DA or Seidelwhatever purpose made engine.
No, not flying day and night, this helicopter uses only about 20 Litres per year.
Several reasons, one being the educational part, another was trying to get rid of the high Nitro content (10% Nitro increases fuel price by over 25%, I guess I cannot deny my Dutch heritage (Ik blijf 'nen 'ollander, he?)). But there are 5 more Methanol powered heli's, they use more, and will probably also get a conversion.
Then it starts to make a noticeable difference in the fuel bill. Maybe than I can afford a 911 too

Your fourstroke idles great because there is a real big prop, keeping it swinging. Mine has to keep idling with only a small flywheel that has about the same inertia as the crankshaft itself, but still has to idle low enough to disengage the clutch. On Glow, that was only a sweet dream, but never reality. With ignition, it is at least on the brink of fully disengaging.

Other consideration was: I have 3 semi commercial trainers in operation.
For those, the ignition units will easily earn themselves back in about 6 months: 8% reduction in fuel price, 20 % reduction in fuel consumption, 2 glow plugs per year, no lessons skipped due starting problems, no delays due dying engines while waiting at the grid, so this was a good learning opportunity.
These helicopters do have a considerable yearly fuel bill, and in nowadays situation, if you can prevent price changes by reducing fuel costs, the students really appreciate it....

The oil thing, well, that has not much to do with it, other than my 4 stroke fuel containing 10% and my 2 stroke 15%. Vario at the time was fairly stressing you should not run a 4 stroke in a helicopter on more than 10 %, with an extended break in to make this possible, so I was kind of worried about that. It seems not to harm the engine, but it does not give any advantage too, so I'll probably go back to 10 or 12 % oil (which is a shame, it would be nice to have only one kind of fuel on the field on the other hand, at 15% oil and 0% Nitro, the oil is 2/3 of the fuel price: I am still Dutch, remember?)

Brgds, Bert

PS: it used to be different, but since my marital status has changed, my fuel expenses ARE my hobby expenses, more or less.... so any reduction is welcome
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Old Oct 30, 2012, 06:31 AM
Glow is Great !
Gary Cee's Avatar
United States, MI, Marysville
Joined Apr 2010
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Quote:
Originally Posted by Reginald View Post
i have made some 27 glow-ignition conversions, classic 30'ies style. The goal was, besides personal challenge to create my own ignition not only running well but good looking as well. There is a small collector market for it. With no profit. But I do not see myself convert good running glow engines to ignition.
I have no problems with these glow engines. They run fine. Why do you guys do it ? You've lost me. I am lost with oil pro's and con's as well.
Yes ...Plus 1
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Old Oct 30, 2012, 07:02 AM
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Just did another 30 minutes.
Last night, I looked over the cooling duct, and removed some ridges that might be disrupting airflow, especially in the vincinity of the finned area of the cylinder.

The first thing I noticed, was that the amount of oil expelled from the crakcase breather increased significantly, from appr 15 cc per 10 minutes to 18 or over.

At midrange throttle the engine seemed to hold RPM better and felt a bit more powerful (I could reduce pitch/throttle noticeably more at cruising speed).

When the engine is "cold" (meaning, it has been idling on the ground for a minute) the power has increased noticeably, but after say, 2 minutes of cruising, it is back to its old self.

All in all I think, cooling has improved, but the finned area of the engine is just not big enough to give sufficient cooling over longer periods.
As long as I am cruising, all is OK, but if I need full power, it is only there the first one or two minutes, and probably less if I hold WOT for longer period of time.

So next step is focus on improving cooling and reducing oil content.

Brgds, Bert
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