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PAW .15 rpm - 12/17/2012 3:33 AM   
Max_Power



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Status: offline 		I have a PAW .15 single ball bearing engine that I bought and have put about a dozen short runs and heat cycles on so far with a wood 9-4 at a pretty under compressed setting where it only really cleared out and stopped missing after being full throttle for a few seconds. I see the cl combat guys that run these run a 8-6 MA propeller. What rpm will this engine normally turn this prop at?

The diesel I have most of my experience on was a RJL converted tower .40 that eventually broke the crank pin off at about 25 flights(although admittedly was turning a probably too large 14-4 zinger). So , I'm trying to take it easy on this guy until I'm sure my tuning "ear" isn,t too harsh .

Also, are there any basic diesel tuning guides or strategies you guys can share...(I am always wishing there was a YouTube video with sound to help folks with this). I've always been confused as many instructions use the term "laboured sounding" and honestly am not sure how this sound is identified? I'm sure my paw will last much better than a conversion anyway...but I'd really like to know that I'm listening for the right sounds and signs. Using Davis plane fuel. Thanks in advance, Todd

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RE: PAW .15 rpm - 12/17/2012 5:59 AM   
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RE: PAW .15 rpm - 12/17/2012 6:11 AM   
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Status: offline 		Hi Todd, I'll chime in in the absence of someone genuinely knowledgeable.* I'm assuming from your mention of 'full throttle' that you've got the RC version. I've only run PAWs with the basic venturi, so I don't know what effect the carb has on performance, if any. For that engine in CL form, I'd expect to see somewhere around 11-12000 rpm with an 8x6.

As far as basic tuning strategies, the big one is not to be overcompressed. You need to make sure the engine is properly warmed up - if you set the comp so there's no misfiring when you first start the engine, then once it's got some heat into it, it's likely to be overcompressed. Where you describe the engine 'clearing out' and stopping missing after a few seconds at full throttle is a good example of what I'm talking about - for full throttle running, what you had doesn't sound like it was really undercompressed much at all. From cold, I usually try to start an engine on its last running compression setting with the needle open a turn or so; it will initially run raggedly, but will smooth out as it warms up and the mixture is gradually leaned out. If it's still misfiring once it's properly warmed up then you might need a bit more comp, or you may be a bit lean. Try to mess with the comp screw as little as possible - once you've found a good setting there should be little need to move it much. It's often possible to start an engine at its 'running' compression, particularly if you can prime the side of the piston. With some engines you can't, particularly if there's a muffler, and you might need an extra half turn or so from cold. As far as the mixture goes, I usually back it off a half turn or so from peak prior to launch, but that might be different with the RC carb.

It's a bit hard to describe 'laboured sounding'! If it speeds up when you reduce the compression, then it was sounding laboured. Once you're used to what the engine sounds like normally, I'm sure you'll have a good sense of when it's sounding laboured or harsh.

I'm sure plenty of others will have something worthwhile to add, particularly those with experience of the RC version.

Steve

*Sorry Chris, that wasn't aimed at you! Your reply (much better than mine I might add) must have appeared while I was composing mine.

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RE: PAW .15 rpm - 12/17/2012 9:29 PM   
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quote:

ORIGINAL: steve111
*Sorry Chris, that wasn't aimed at you! Your reply (much better than mine I might add) must have appeared while I was composing mine.


Hmm, not quite sure how to take all of that?!

Anyway, take Steve's advice as he is far more experienced than I but the labouring sound .......... I have never thought about how to describe it to some one before but to me it is as different as a groan is from a sigh of pleasure.
It simply sounds mechanically wrong and if I was pushed to place a sound on it, it would be 'flat.'

An engine on song sounds indeed sounds like it trills along singing happily, but one that is forced to labour overcompressed grumbles and stumbles without any sharp or clear overtones.
Thus to me it sounds musically flat.

Much like a car that is pushing too high a gear going up hill, it simply feels and sounds wrong, and even if you have no prior training to diagnose such things you will sympathetically know in your heart that it ain't right.

Tough subject.



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RE: PAW .15 rpm - 12/17/2012 10:52 PM   
Max_Power



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Status: offline 		Thanks guys. I think I'm close but I think I'm figuring out that maybe with the RC it taking a few seconds to get heat in it after some low rpm time is normal. The oil has always been nice and light colored as compared to my conversion that was a bit darker. I think I'm gonna put it back on the test stand and fool with it a bit more in the next day or so. I'm in Minnesota, how can I expect this thing to handle in the cold weather not flying but basically just test running? I'm thinking I may need to burn the heater in the garage a few minutes before starting. Although I don't think heater and ether sound like a safe combo, but have never run anything but glow in the cold so.....Todd

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RE: PAW .15 rpm - 12/17/2012 11:53 PM   
1QwkSport2.5r



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Status: online 		Todd - if it were me, I'd run the heater in the garage until you get it at least to 60°F and kill the heat then run the engine. This way its warm and you dont blow yourself up.


I've been contemplating running a glow engine or two in the garage or shed, but I was hoping for a warmer day so I dont get frostbite adjusting the needle valve. LOL.

Now that I'm off work for the rest of the year, I might have to come watch you run that little PAW again. I haven't had my kerosene fix lately....



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RE: PAW .15 rpm - 12/18/2012 1:41 AM   
Max_Power



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Status: offline 		Lol....if I run the heat trying to get the garage to 60 right now I think that little PAW will rust solid waiting! I might be able to pull off 50. , at least I have my "poly-cave" where the lathe is that is a bit more heat-able. ....and not even January yet

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RE: PAW .15 rpm - 12/18/2012 1:47 AM   
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Status: online 		You need a bigger heater.

I have two heaters, 65k BTU combined, and can get my garage to 80* in about 15 minutes at 32* outside temp if I run both at full power.




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RE: PAW .15 rpm - 12/18/2012 2:45 AM   
Max_Power



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Status: offline 		I think I need some insulation....the heater puts out 85k lol. Admittedly I don't really usually leave it run all that long , usually riding the fine line between freezing grapes and a propane fume headache. I usually shut it down when I hear all the metal fuel cans popping from expansion. I wish those propane torpedoes had a automatic light where it could be on a thermostat and not have to hold down the gas feed button while the thermocouple warms up!

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RE: PAW .15 rpm - 12/18/2012 3:46 AM   
1QwkSport2.5r



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quote:

ORIGINAL: Max_Power

I think I need some insulation....the heater puts out 85k lol. Admittedly I don't really usually leave it run all that long , usually riding the fine line between freezing grapes and a propane fume headache. I usually shut it down when I hear all the metal fuel cans popping from expansion. I wish those propane torpedoes had a automatic light where it could be on a thermostat and not have to hold down the gas feed button while the thermocouple warms up!

I didn't think about insulation. I insulated the whole garage with 1.5" styro. That makes all the difference.

Some torpedoes have t-stats, although mine doesn't.

For some reason propane heater fumes don't bother me; kerosene torpedoes do though. Diesel smells better than kero.


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RE: PAW .15 rpm - 12/18/2012 3:33 PM   
aspeed


 

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Status: offline 		I normally use a kerosene torpedo heater to get it up to temp, and then a kero "candle" type with a wick to keep the temp up after that because the torpedo one is way too loud. I know a guy that used the candle type to heat his whole house for a couple of years till he put on the addition.  I haven't even used the heaters for a couple of years now at the new place since I have the models in the house now.(that took a lot of convincing)  My lathe and mills are still in the cold shop but I seldom am there more than a half hour at a time.

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RE: PAW .15 rpm - 12/18/2012 6:26 PM   
1QwkSport2.5r



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ORIGINAL: aspeed

I normally use a kerosene torpedo heater to get it up to temp, and then a kero ''candle'' type with a wick to keep the temp up after that because the torpedo one is way too loud. I know a guy that used the candle type to heat his whole house for a couple of years till he put on the addition.  I haven't even used the heaters for a couple of years now at the new place since I have the models in the house now.(that took a lot of convincing)  My lathe and mills are still in the cold shop but I seldom am there more than a half hour at a time.

Does your other half let you run engines in the house?

Mine doesnt. I do keep my models and fuel in the house though, only because my last two cars and toolbox was stolen from my garage several years ago. If it weren't for that, they'd be in the garage.

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RE: PAW .15 rpm - 12/18/2012 8:01 PM   
ffkiwi


 

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Status: offline 		Gents-can you start a home heating thread somewhere else? .....this one is getting tedious-AND its supposed to be about PAW 15s!!

ChrisM
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RE: PAW .15 rpm - 12/18/2012 8:22 PM   
1QwkSport2.5r



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ORIGINAL: ffkiwi

Gents-can you start a home heating thread somewhere else? .....this one is getting tedious-AND its supposed to be about PAW 15s!!

ChrisM
'ffkiwi'

I only brought up the subject of heating the shop up to give the engine a better chance of running "nicely" versus cold and crappy.. Then again, it probably is a bear to get started since its only 30°F outside if not colder.

Sorry Todd, for hijacking your PAW thread with the idea of heating the shop up. I'll refrain from this behavior from now on.

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RE: PAW .15 rpm - 12/18/2012 8:24 PM   
Max_Power



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Status: offline 		Sorry Kiwi, I really did'nt think a few posts would bother anyone...but, as the two subjects merged from me wandering if I was wasting my time trying to run the engine in a cold garage or even fly it in freezing weather. I guess I will just have to try it out. I know at a certain temp I've had glow engines that were difficult to start or only wanted to stay running at full throttle. I guess I should have included the temperature question in my original post. Anyone have any experience with running PAW .15s in cold weather?

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RE: PAW .15 rpm - 12/18/2012 9:09 PM   
ffkiwi


 

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From: Upper HuttWellington, NEW ZEALAND
Status: offline 		NZ does not get as cold as Canada-but down south (where I hail from), and in inland areas, winter temps of -5 to -10C are not uncommon. Generally our best flying weather is then-calm frosty days.The diesels don't seem to mind-though to be fair, they do get a bit snappy on starting. A whacked finger from time to time is almost a rite of passage.................but that can be circumvented by either a rubber finger stall, a leather glove, or a chicken stick.

Personally, from observations made at the Omarama FF World cup events (and I've run them since 1994), high compression glow engines on straight fuel (ie F1C engines) are far more of a problem in cold weather when it comes to starting........

....of course this relative ease of starting depends on your perspective-and certainly you'd want good fresh fuel, and a decent sized prop.....I wouldn't want to be flicking a 7x6 on a PAW15 on a cold morning.....

ChrisM
'ffkiwi'

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RE: PAW .15 rpm - 12/19/2012 12:54 AM   
j.hiner@comcast.net


 

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Status: offline 		I have run PAW .15 and .40 diesels in January and Feburary in North Illinois. Temps in the 30's F. no problem with PAW diesels. Jack

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