Soggy Plugs

40 posts in this topic

Posted

They were on 

Manu, 

It occurred to me that your airframe may not have the pully and rope guide mounts welded on.  Here is a picture of mine.  They are welded on to the V-strut.

 

20181015_163926.jpg

They were on my B model, and also on both MK IVs.  I think it's a standard feature.  JImChuk

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Posted

Are you using paper element fuel filters with pre-mixed gas or is that part of your new system?

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Posted

yes i got it pre welded and mounted, that's good news turbo you can start engine "easy" inside plane, was wondering how much strength i need to fire it up;

for the trim, i updated my topic where u can have look :BC:

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Posted (edited)

Vance,

That big paper filter will filter oil for the OI pump.  Left upstream end of tubing open for a few days, and sure enough, a bug crawled in!  First big chunk to be filtered out, I guess!

Oh, and on the fuel system, I also have a paper filter, the smaller kind.  Tested its pressure drop at max static RPM and found it negligibly small!  Flow speeds inside 1/4" fuel line at max power are less than 10 "/sec!

Edited by Turbo

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Posted (edited)

RE: Starter rope location. How many of us can bend at the waist and touch our feet? Not being critical or snide. I don't have a belly but I am 53 and flexibility is certainly an issue for me. Never having sat in your plane, Vance, is it easier than it looks in the picture.

 

On Edit: Oooops, my question should have been directed to Turbo instead of Vance.

Edited by Ramos
add

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Posted

It's been a know fact never to use a paper fuel filter when oil is present. Oil can clog the paper filter. This was the cause of a lot of Ultralight engine outs back in the day.  

The oil injection uses an in-line filter that has a metal screen and is much smaller than the filter you show there. Using a paper filter can cause your system to lean if the paper filter should become clogged. 

For fuel I use a Pro-line filter. They have a plastic mesh element. Do not buy the know-off brands of these. They are junk. 

Pictures of both attached.

15-05826.jpg

oil filter.PNG

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Posted

Trouble with knock off brands verses name brands.  I bought a KnN fuel filter like yours and if was junk.  I don't know if KnN has gotten that bad or if it was a complete knock off with brand name and all.  It looked like complete Chinese junk and low grade junk at that.  buyer beware!   JImChuk

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Posted (edited)

Manu,

My starter allows about 20 cm of line to pay out before engaging the engine.  You may have to experiment with how much line you put on the starter reel, or where you tie the knot on the starter handle.  This improves the biomechanics of starting.  

Vance,

I have an unused fine mesh SS screen filter for the fuel, which I will test for pressure drop and leave in place if it passes muster.  I will also start looking for a similar screen filter in 5/16" for the oil line.  Thanks for the heads-up.  I gotta say, though, I was not too impressed with the plastic-element Pro-Line filter.  The possibility of clogging is why I chose such a large paper filter for the oil, plus pressure drop concerns since the oil is so viscous relative to gasoline.  The oil flowrates are very low, (2% of fuel flow) however, so I can't see there being much drop thru even a paper filter.  Maybe I'll do a simple test to validate its viability.  So what is the concern?  Water in the oil tank via thermal respiration, like in an airplane's fuel tank?

Edited by Turbo

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Posted

The main issue with paper filters is water.. if water gets in the system it will plug off that filter right now.  Been there, done that, damn near had the tee shirt.  The electric boost pump saved my butt and kept me out of the trees.  

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Posted (edited)

I'll wager that the vapor pressure of any pure 2-stroke oil is way lower than that of gasoline, which means that the positive displacement oil pump can be expected to suck oil through that paper oil filter, even if it is partially wet.  However, once that paper element is soaked in oil, water's high surface tension will preclude it displacing the oil and wetting the paper.  The filter will in effect, become a water trap.  Visual inspection will tell if any water has thermally pumped its way into the oil tank, as it will show up as a harmless glob of water at the bottom of the filter, upstream of the paper.

Before commiting to the paper oil fiter, however, I plan on conducting a flow test to validate acceptable oil flow without the oil pump, just gravity, and at a low ambient temperature.  I'm looking for an order-of-magnitude 1 floz/min flowrate. Piddly!

Edited by Turbo

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Posted

you can do all the testing you want.. however, you could also take the word of many many guys that have bent birds, ended up in the hospital or worse.  Its a known issue and for the extra few bucks not worth the headache to get the correct filter and have some peace of mind.. But to each their own.

:BC: 

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Posted

Just swapped out the paper filter in my fuel line for a screen.  I intend to test the new screen for pressure drop.  Burning pre-mix, that old filter had some water in it, yet was still flowing pre-mix with negligible pressure drop.  Maybe the oil in the pre-mix wetted the paper, trapping the water.  Maybe fuel alone would do the same.  I could see a scenario where that paper filter could be inundated with so much water that it could stop flowing, though. The very small pore size makes surface tension a much more powerful effect.  Without being able to wet the paper with water, I can see how the pressure drop required to push the water thru that filter could be large.

Where I am contemplating using a paper filter is only in the oil line to the oil injection pump.  Went online looking for a screen filter in 5/16" line size, and couldn't find one.  I am going to locate that filter where it is easily inspected.  The much smaller OI tank should not suck in anywhere near the amount of water that a wing tank would.  I intend to keep the oil tank full when stored.  

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Posted (edited)

Did you see this page in the LEAF online catalog?  Incase the link doesn't work, look at page 19 item # 4145365.  Says it's for a 3/8" line, but you can stretch the 5/16" line enough I'm guessing.   Also, I think any snowmobile uses an oil filter on the line as well so check some one like Dennis Kirk catalog.  I would stay with a screen instead of paper for the oil filter myself.  JImChuk       onlinecatalog.leadingedgeairfoils.com/19/#zoom=z

https://www.denniskirk.com/kimpex/oil-injection-filter-07-246-05.p180108.prd/180108.sku
 

 

Edited by 1avidflyer

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Posted

Silly me!  I keep going to auto parts stores instead of places that sell & service snowmachines!  Thanks for the tip, JimChuk!

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Posted

It just occurred to me that the place to put a fuel filter is downstream of the header tank, which really is a huge gascolator, i.e. a water trap!  Note that the outlet of the header tank is above the bottom, which is where the drain is.  That's a lot of volume for trapped water.  In my plane, there was a paper inline filter just below the fuel tank, behind the seatback.  When I took it off, I found it had a small amount of trapped water.  I am moving the fuel filter to the engine compartment, just ahead of the fuel pump.  I expect it to not accumulate water there.  

 

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