Crank Case Vent Tube Length
10-19-2005, 09:19 AM
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RE: Crank Case Vent Tube Length
The function of the tube is just to allow excess oil to drain from the engine. Tube length is not as far as I heard a problem unless it is an unreasonable lenght like 8 inches or something longer. As long as the oil gets out it really doesnot matter.
10-19-2005, 11:11 AM
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RE: Crank Case Vent Tube Length
This is pure speculation. Maybe if the tube is too long the residue will not drain to atmosphere but lay in the tube or not get out quick enough and the piston going up will suck it all back in again.
I know, I know it is a bit of a stretch!
Ed s
I know, I know it is a bit of a stretch!
Ed s
10-19-2005, 11:25 AM
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RE: Crank Case Vent Tube Length
To me, the main purpose of having a hose on the case vent is to prevent the reverse flow (as the piston goes up) from pulling trash from the air back into the bottom end of the engine. Directing the waste oil away from the plane is an added benefit.
Length? I think a three inch maximum is hogwash. Personally, I go for a four inch MINIMUM length. This gives me a little margin. On really dusty days I've seen dirt pulled inside the vent hose as much as 1/2 inch, the rest of the length is a safety margin.
Side note - I also have Bru-Line air filters on most of my engines, and all the four stroke engines.
Bill.
Length? I think a three inch maximum is hogwash. Personally, I go for a four inch MINIMUM length. This gives me a little margin. On really dusty days I've seen dirt pulled inside the vent hose as much as 1/2 inch, the rest of the length is a safety margin.
Side note - I also have Bru-Line air filters on most of my engines, and all the four stroke engines.
Bill.
10-19-2005, 01:06 PM
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RE: Crank Case Vent Tube Length
Hi Bill, do you run coarse or fine bru line filters? My hobby shop seems to only be able to get fine, but I did get a coarse from Tower. I see no reason for the fine unless flying in really dusty conditions.
Ernie
Ernie
10-19-2005, 01:18 PM
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RE: Crank Case Vent Tube Length
Ernie:
To me the Bru-Line coarse element isn't much more than a gravel catcher, or something to keep small children from falling into the intake.
I agree with your LHS, the coarse elements are not worth the bother. I use only the fine elements, not enough flow restriction even on the 180 engines to notice. Unless they get too dirty of course, then if you've not brought a spare you can pull it out and flush the trash with a squirt of fuel.
Bill.
To me the Bru-Line coarse element isn't much more than a gravel catcher, or something to keep small children from falling into the intake.
I agree with your LHS, the coarse elements are not worth the bother. I use only the fine elements, not enough flow restriction even on the 180 engines to notice. Unless they get too dirty of course, then if you've not brought a spare you can pull it out and flush the trash with a squirt of fuel.
Bill.
10-20-2005, 03:08 PM
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RE: Crank Case Vent Tube Length
Bill, can you get to the element to change it okay on the Saitos with the carb in the rear? Have you ever had an element come loose in it's mount and attempt to be sucked into the intake? Maybe a good idea to change out the filter completely once in a while?
Thanks again,
Ernie
Thanks again,
Ernie
10-20-2005, 04:26 PM
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RE: Crank Case Vent Tube Length
Ernie:
Except in an open engine mounting changing the filter element will be a pain with the rear mounted carb. Thankfully my area isn't really bad and I can go four to six weeks without cleaning it.
As strange as it seems, the filter on my Diablo doesn't seem to get dirty at all. It has a K&B ringed 61 engine, front intake. My supposition is the prop tends to act as a centrifugal filter, slinging the dust away from the intake. On the other hand, the Saitos, with the filters in back, turn black pretty quickly.
The only element failure I've had was on a Saito, but it wasn't the filter's fault. The engine started backwards and literally melted the foam out of its mounting ring. Didn't hurt the filter body, and it was easy to pop a new element in.
Bill.
Except in an open engine mounting changing the filter element will be a pain with the rear mounted carb. Thankfully my area isn't really bad and I can go four to six weeks without cleaning it.
As strange as it seems, the filter on my Diablo doesn't seem to get dirty at all. It has a K&B ringed 61 engine, front intake. My supposition is the prop tends to act as a centrifugal filter, slinging the dust away from the intake. On the other hand, the Saitos, with the filters in back, turn black pretty quickly.
The only element failure I've had was on a Saito, but it wasn't the filter's fault. The engine started backwards and literally melted the foam out of its mounting ring. Didn't hurt the filter body, and it was easy to pop a new element in.
Bill.
10-20-2005, 08:16 PM
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RE: Crank Case Vent Tube Length
Saito 56 in Rascal 40. I ran crankcase vent full lenght of the fuselage. Clear plastic rigid tubing that was a container for some item I bought in hobby store. Silicon tubing from crankcase just fits in clear tubing. Must work, because the oil can be seen dischargiing out the rear near the tail wheel. I run fuel with extra castrol and it slimes the fuselage to much. This solution works for me. But I can listen if someone tells me this will harm the motor.[X(][X(]
10-21-2005, 03:20 AM
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RE: Crank Case Vent Tube Length
I used about three feet of small inner nyrod tube on the case vent. Durring the summer everything was fine but when it got cold I noticed a lot of oil drooling from the front bearing. The castor was getting cold and too thick to flow through the small tube. I solved the problem by using the outer nyrod tube and had no more troubles. The clogged tube did not change the way the engine ran, it just vented out the front.
10-21-2005, 11:54 PM
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RE: Crank Case Vent Tube Length
Firewalkerd1:
I have the same problem with a straight sided intake - there's nothing to hold the rubber in place.
The Saito inlet stacks all are flared, the K&B and Perry carbs are funnel shaped on the outside, the Bru-Line filters stay on them with no problem. On the other hand, the stack I put on my Magnum 25 is a straight pipe, I haven't even tried to put a filter on it. On larger engines with the straight sided intake I've found that a light smear of 3M "Amber Weatherstrip Cement" along with a small plastic tie wrap holds them with no problem. Until time to change or clean the element, then I usually have to apply some fresh glue. But they stay on in service.
HTH.
Bill.
I have the same problem with a straight sided intake - there's nothing to hold the rubber in place.
The Saito inlet stacks all are flared, the K&B and Perry carbs are funnel shaped on the outside, the Bru-Line filters stay on them with no problem. On the other hand, the stack I put on my Magnum 25 is a straight pipe, I haven't even tried to put a filter on it. On larger engines with the straight sided intake I've found that a light smear of 3M "Amber Weatherstrip Cement" along with a small plastic tie wrap holds them with no problem. Until time to change or clean the element, then I usually have to apply some fresh glue. But they stay on in service.
HTH.
Bill.
