| 11-05-2014 07:14 PM |
| jsparky |
Re: Can someone explain glo vs. gas engine designations? How do they compare for pow
Quote:
Originally Posted by cosmith
On another note, something I wanted to mention to the OP. As far as tank pressure goes with glow engines, you have to be careful with aftermarket exhausts. If an exhaust flows better the pressure inside will be lower. I encountered this with a pitts style muffler on a OS .46AX. I could get it to run reasonably well, but I could never get it rich enough to 4 stroke, even with the high speed needle wound all the way out. After a bit of research I plugged up one of the outlets on the exhaust which increased my tank pressure and solved all my problems.
|
My Co-member and fellow pilot has a very valid point.. one which I was just dealing with last week and have to finish.. and somehow forget to mention.. But Cory is absolutely right about the mufflers.. strapping on a different muffler just because it looks or sounds cool.. can cause no end of headaches.. and here is a little test you can do if you suspect that you may not be getting muffler pressure..
start up your engine as you would normally... and let it warm up.. you want the exhaust gases to be hot so that they expand in the muffler to create back pressure,, you may have to touch your idle up a bit to keep the engine running .. but with the engine running pull the line off at the muffler... then put on a second spare line to the muffler.. have a glass of water handy and put the other end of the line in the water slowly.. and see how deep it goes in the water and blow bubbles.. If the line is only about 1/4 inch below the water surface you should see a few bubbles popping out.. if not .. you have a problem.. you should see a few bubbles coming from the line up to about an inch below the water surface.. at inch and half.. if you still see bubbles.. you may have a different problem.. too much restriction
And Corey !! "OP" had better not stand for " old people "
I will soon be setting the fuel aside for a short bit for a new project coming along..
I have gotten bitten by the jet bug.. my first serious electric
a 57 inch Viper with 90mm 12 blade EDF
This should bring some serious crap to the shop.. have not played with electrics much..
jeff
|
| 11-05-2014 06:15 PM |
| Flypaper |
Re: Can someone explain glo vs. gas engine designations? How do they compare for pow
After many miles I never had the filter in the line between the muffler and the tank plug up. There is just too much surface area in the filter to plug up. You would see black flex on the screen but that's it, and what it was supposed to do.. As you, I also used a filter in the bottom of the fuel jug.
|
| 11-05-2014 06:00 PM |
| cosmith |
Re: Can someone explain glo vs. gas engine designations? How do they compare for pow
Quote:
Originally Posted by jsparky
I once had the same thought.. of putting a filter in the exhaust line.. But as fate would have it.. and that guy Murphy .. It is not such a good idea.. the screens in those filters are so small that your pressure line can prematurely plug up particularly if you have a habit of running your engine on the rich side.. If you are concerned about carbon in you tank.. the best choice would be to put a cintered fuel clunk in your tank..
If you want to see something really interesting and an idea I though was good.. get a small 1 once fuel tank with only two lines.. and install it between your muffler and fuel tank.. run a tank or two of fuel through your engine.. then look inside that little tank.. you will find little specs of carbon a bit of oil... and surprisingly.. water..
My method is none of the above.. but I have a cintered clunk in my fuel jug for a pickup and one of those super fine inline filters in the fill line of my jug.. I prefer to cure the problem at the source.. filter all my fuel going into the tank.. and then when I am done flying I pump the tank dry ,, then put the fill line into the jug and turn on the pump and back flush the filter..
I have yet to have a problem with contaminates in my tank.. And you should pull your tank every couple of years just to check it ,, clean and replace fuel lines..
Now since we are on the subject of fuel and contaminates.. All to many times I see people at the field when they are done for the day.. take their plane , wipe it down and clean it all up to take home and hang until the next day of flying.. I don't think I have ever seen anyone even put in after run oil.. but just cleaning the plane and taking it home.. that has to be one of the worst things you could do to your engine..
The fuel is methol alcohol or if you prefer " gas line anti freeze "... it attracts moisture.. and moisture will rust the bearings and any other metal parts in the engine.. And it doesn't take long for that to start happening..
The best thing you could do for your engine.. after your done for the day is to remove all of the fuel from the tank.. then start the engine.. this will remove pretty much all of the methol alcohol and nitro from the engine and reduce the risk of rust forming.. which a small particle of rust getting loose in your engine can do far more damage than a piece of carbon in your fuel tank..
If you want to see this for yourself... if you have a plane where you can get at the fuel line to the carb.. just one day start it up and let it run for a minute... then pull the fuel line of the carb... you would be surprised to see how long some engines can run for.. just on the fuel in the crankcase.. and as surprising as it may be.. even a 4 stroke will run after you have pulled the fuel line..
Using the above methods.. I have yet to need after run oil.. the oil will not remove the alcohol.. it would still be there attracting moisture..
This is another advantage that gas engines have vs nitro.. because they are a petroleum based fuel.. they are not prone to internal rusting
|
The sintered clunks are awesome...they seem to pick up foamed fuel nicely as well. I used them in all my glow powered cars.
I'm glad you brought up the after run oil thing. With glow engines, land or air, I've always done my best to run all the fuel out of the engine before storing. Any time I've torn down an engine it is slimy all over with castor just like the outside of the plane after flying. Therefore, I've never really understood the point of after run oil.
Now, I could see if you leave the crank case full of unburnt fuel, you could potentially get corrosion where the alcohol has displaced the oil and allowed moisture at the metal. Since water is a by product of combustion there will always be some water vapor in there as well, I just never thought it would get at the metal with all the castor coating everything.
Another tip I've heard is to store the plane nose down, that way any residual castor will run into the bearing and keep it from corroding.
On another note, something I wanted to mention to the OP. As far as tank pressure goes with glow engines, you have to be careful with aftermarket exhausts. If an exhaust flows better the pressure inside will be lower. I encountered this with a pitts style muffler on a OS .46AX. I could get it to run reasonably well, but I could never get it rich enough to 4 stroke, even with the high speed needle wound all the way out. After a bit of research I plugged up one of the outlets on the exhaust which increased my tank pressure and solved all my problems.
|
| 11-05-2014 05:19 PM |
| jsparky |
Re: Can someone explain glo vs. gas engine designations? How do they compare for pow
Quote:
Originally Posted by Flypaper
I'd recommend putting a small fuel filter in the pressure line from the muffler to the tank, for this reason. I took the tank out of a retired plane with many miles on it. There were little flecks of carbon it the tank that had broken from the muffler, went through the line and into the tank. Never notived this before I took this tank out.
At least put a filter in the line from the tank to the carb.
|
I once had the same thought.. of putting a filter in the exhaust line.. But as fate would have it.. and that guy Murphy .. It is not such a good idea.. the screens in those filters are so small that your pressure line can prematurely plug up particularly if you have a habit of running your engine on the rich side.. If you are concerned about carbon in you tank.. the best choice would be to put a cintered fuel clunk in your tank..
If you want to see something really interesting and an idea I though was good.. get a small 1 once fuel tank with only two lines.. and install it between your muffler and fuel tank.. run a tank or two of fuel through your engine.. then look inside that little tank.. you will find little specs of carbon a bit of oil... and surprisingly.. water..
My method is none of the above.. but I have a cintered clunk in my fuel jug for a pickup and one of those super fine inline filters in the fill line of my jug.. I prefer to cure the problem at the source.. filter all my fuel going into the tank.. and then when I am done flying I pump the tank dry ,, then put the fill line into the jug and turn on the pump and back flush the filter..
I have yet to have a problem with contaminates in my tank.. And you should pull your tank every couple of years just to check it ,, clean and replace fuel lines..
Now since we are on the subject of fuel and contaminates.. All to many times I see people at the field when they are done for the day.. take their plane , wipe it down and clean it all up to take home and hang until the next day of flying.. I don't think I have ever seen anyone even put in after run oil.. but just cleaning the plane and taking it home.. that has to be one of the worst things you could do to your engine..
The fuel is methol alcohol or if you prefer " gas line anti freeze "... it attracts moisture.. and moisture will rust the bearings and any other metal parts in the engine.. And it doesn't take long for that to start happening..
The best thing you could do for your engine.. after your done for the day is to remove all of the fuel from the tank.. then start the engine.. this will remove pretty much all of the methol alcohol and nitro from the engine and reduce the risk of rust forming.. which a small particle of rust getting loose in your engine can do far more damage than a piece of carbon in your fuel tank..
If you want to see this for yourself... if you have a plane where you can get at the fuel line to the carb.. just one day start it up and let it run for a minute... then pull the fuel line of the carb... you would be surprised to see how long some engines can run for.. just on the fuel in the crankcase.. and as surprising as it may be.. even a 4 stroke will run after you have pulled the fuel line..
Using the above methods.. I have yet to need after run oil.. the oil will not remove the alcohol.. it would still be there attracting moisture..
This is another advantage that gas engines have vs nitro.. because they are a petroleum based fuel.. they are not prone to internal rusting
|
| 11-05-2014 08:26 AM |
| Flypaper |
Re: Can someone explain glo vs. gas engine designations? How do they compare for pow
I'd recommend putting a small fuel filter in the pressure line from the muffler to the tank, for this reason. I took the tank out of a retired plane with many miles on it. There were little flecks of carbon it the tank that had broken from the muffler, went through the line and into the tank. Never notived this before I took this tank out.
At least put a filter in the line from the tank to the carb.
|
| 11-04-2014 08:14 PM |
| jsparky |
Re: Can someone explain glo vs. gas engine designations? How do they compare for pow
Quote:
Originally Posted by cosmith
Just trying to keep it simple...I call it vacuum pump because it sucks fuel from the tank rather than pushing it! Knew that wasn't the technical name. It is the vacuum created by the pressure pulses that gets the fuel from the tank to the carb, correct?
|
In a round about way you could say it vacuum's the fuel from the tank .. interesting way of thinking about it.. the piston on the down stroke creates the pressure to push the fuel internally to the combustion chamber and at the same time pulse the carb to draw or vacuum the fuel from the tank.. on the up stroke it creates the internal vacuum to draw in the next charge of fuel and air to the crankcase..
repeat above cycle.. and you have a running engine.. the basics.. there are more things in the carb doing funny little things.. Way beyond the scope of this thread ...
As a coworker of mine says about gas engines.. "" PFM ""
|
| 11-04-2014 05:59 PM |
| cosmith |
Re: Can someone explain glo vs. gas engine designations? How do they compare for pow
Quote:
Originally Posted by jsparky
One little correction Corey... It is a pressure pulse from the crank case that makes the pump work.. some have an extrenal pulse line while others have a port drilled into the carb that goes through the reed block to the internal crank case.. the reason for the reed block.. to prevent that pressure from escaping out the carb.. the vacuum that is next created draws the fuel and air into the engine past the reed block. then on the next stroke the pressure is used to push the fuel up the internal ports past the piston into the combustion chamber and pulse the carb again..
It is a vicious cycle.. several hundred to several thousand times a minute.. but seems to work well..
jeff
|
Just trying to keep it simple...I call it vacuum pump because it sucks fuel from the tank rather than pushing it! Knew that wasn't the technical name. It is the vacuum created by the pressure pulses that gets the fuel from the tank to the carb, correct?
|
| 11-04-2014 05:40 PM |
| aeajr |
Re: Can someone explain glo vs. gas engine designations? How do they compare for pow
Very interesting guys.
|
| 11-04-2014 05:34 PM |
| jsparky |
Re: Can someone explain glo vs. gas engine designations? How do they compare for pow
Quote:
Originally Posted by cosmith
Most larger gas engines use a carb with a vacuum type pump,
|
One little correction Corey... It is a pressure pulse from the crank case that makes the pump work.. some have an extrenal pulse line while others have a port drilled into the carb that goes through the reed block to the internal crank case.. the reason for the reed block.. to prevent that pressure from escaping out the carb.. the vacuum that is next created draws the fuel and air into the engine past the reed block. then on the next stroke the pressure is used to push the fuel up the internal ports past the piston into the combustion chamber and pulse the carb again..
It is a vicious cycle.. several hundred to several thousand times a minute.. but seems to work well..
jeff
|
| 11-04-2014 01:13 PM |
| cosmith |
Re: Can someone explain glo vs. gas engine designations? How do they compare for pow
Quote:
Originally Posted by aeajr
Are all fuel tanks, glow and gas, pressurized? Is there a bladder in there or something like that? I am sure you don't just blow exhaust gas into the fuel tank.
|
Most glow tanks are pressurized. You simply run a piece of gas line from a nipple on the muffler to the tank...yes in essence you are blowing exhaust gas into the tank. No bladder is required, it is just a sealed tank. Keep in mind glow exhaust is relatively cool and you aren't blowing a volume of gas into the tank, it is just maintaining positive pressure.
There is naturally some vacuum once the engine is running but it's too weak to work alone. I have had a plane keep flying for a long time after my pressure line came disconnected, but it leaned out a ton on any up line. Of course, once you realize this has happened you need to land asap to avoid damaging your engine.
Most larger gas engines use a carb with a vacuum type pump, same as you would see in a chainsaw, weed whacker, etc. In fact, most of the carbs we use are the same ones, or copies of the ones Walbro makes for lawn type equipment.
Some of the smaller gassers use exhaust pressure just like the glow engines.
There are some other types of carbs and pumps that you probably shouldn't worry about for now, such as the perry pump. It just allows you to use a fuel pump rather than exhaust pressure. I would stick to the K.I.S.S. method when you are just starting out though.
Quote:
Originally Posted by aeajr
I presume if you have a forward fuel tank then you start off a little nose heavy and finish a bit tail heavy. Is there a way to compensate for that in the plane or is it just a matter of pilot awareness?
|
You are absolutely correct. The only solution is to keep the tank as close to the CG as possible. Positioning the tank in a glow plane is a compromise between CG, proximity to engine and height relative to the carb. I suppose it depends on the size of the plane and volume of the tank, but in my planes I haven't noticed a huge difference from empty to full, not even enough to warrant a click of elevator trim. In a plane with any sort of a pump, tank position is much less critical, and you will position it as close to CG as possible. I wouldn't worry too much about this for now.
Quote:
Originally Posted by aeajr
How do you keep the fuel flowing when you go inverted or straight up, say flying pattern? I have heard of something called a clink but that was in the context of control line. How does that work with RC gas and glow?
|
The fuel line inside your tank has a weighted pick up that we call a clunk. It follows the fuel around by gravity as you fly. Typically the only setup considerations are the length of the fuel line going to the clunk and how stiff it is. There are different types of fuel line for gas and glow, typically you use the most flexible type available for your clunk line. You want to make sure the clunk moves freely inside the tank. I always use a clunk with a filter built in.
Hope that clears some things up!
|
Topic Review (Newest First)
Your Privacy Choices