Oil catch can ideas?

[geoffreywh]

Sorry Nev. I'm coming down off some serious meds. My only reason to "recirculate" vented oil (seperate from air/water) is for an engine that carries an insufficient supply of oil.... Such as Jab. My friends engine vents a lot of oil and is in danger of running out of oil on a longish flight. It's not economically viable to renew the engine ( again!) So we recirculate and the catch can contains only water. .....My apologies again...............

 

 

[Old Koreelah]

Thanks for all the replies, people. After considering all viewpoints I've decided against fitting an oil recycler; the extra weight and work would be better spent on installing a mechanism to add, on longer flights, a little oil in-flight.

 

 

[facthunter]

If you regularly do long(ish) flights, consider a means of adding oil in flight, by a hand pump with a amount per stroke known. This facility would have saved quite a few aircraft being ferried across large stretches of water like the Pacific. If you have a known established rate of oil useage you can add the right amount appropriate for the elapsed time. Naturally it would be better to have a level indication in the cockpit , but that is not practical for this application. Nev

 

 

[Oscar]

If you regularly do long(ish) flights, consider a means of adding oil in flight, by a hand pump with a amount per stroke known. This facility would have saved quite a few aircraft being ferried across large stretches of water like the Pacific. If you have a known established rate of oil useage you can add the right amount appropriate for the elapsed time. Naturally it would be better to have a level indication in the cockpit , but that is not practical for this application. Nev

I believe Charles Kingsford-Smith had such a system on the Southern Cross, did he not? It was called the 'Bill Taylor' system..

 

 

[biggles]

The problem with Jabs in particular is their small sump capacity ( 2.3 lts for 4 cyl.) and the time required for the oil to drain back . A refuelling stop generally doesn't allow sufficient time, consequently the dipstick reading may give a wrong indication . Get to know your cruise oil consumption ( eg 50 mls/hr ) , and multiply by hours flown , seems to work for me. Check the oil catch bottle frequently and empty before it gets too full to avoid the oily film on the underside of the fuselage . I do tend to run slightly higher levels than recommended which shows up in the bottle, but this gives me some 'comfort' on those longer legs . No other downsides , oil temps etc., detected ...... Bob

 

 

[facthunter]

It is a rather minimal amount in the sump and therefore a bit more critical. Some engines will run hotter when overfilled. A large sump takes a longer time to warm up..Nev

 

 

[Old Koreelah]

If you regularly do long(ish) flights, consider a means of adding oil in flight, by a hand pump with a amount per stroke known. This facility would have saved quite a few aircraft being ferried across large stretches of water like the Pacific.

At least Jab engines don't use oil like the old radials; I've seen oil consumption per hour figures in the gallons!

 

 

[facthunter]

The ones I flew had oil transfer in flight, systems. The oil amount to fuel carried was limiting at a ratio of 1:35 so your range was limited by oil available. If an engine was chewing oil on a long over water flight you would feather it and restart for landing rather than pour lot's of oil into it and maybe have it fail anyhow, after using lots of your oil up. Nev

 

 

[Oscar]

The problem with Jabs in particular is their small sump capacity ( 2.3 lts for 4 cyl.) and the time required for the oil to drain back . A refuelling stop generally doesn't allow sufficient time, consequently the dipstick reading may give a wrong indication . Get to know your cruise oil consumption ( eg 50 mls/hr ) , and multiply by hours flown , seems to work for me. Check the oil catch bottle frequently and empty before it gets too full to avoid the oily film on the underside of the fuselage . I do tend to run slightly higher levels than recommended which shows up in the bottle, but this gives me some 'comfort' on those longer legs . No other downsides , oil temps etc., detected ...... Bob

YES!

 

According to the guy who manufacturers them, Jabs will expel excess oil in the sump due to air pressure from the reciprocating componentry until they reach equilibrium of sump volume. If you're getting excessive oil in the catch-can - you're putting too much oil in. You're not BURNING the bloody stuff - by definition, if it's there in the catch-can, it ain't burnt off. A whole lot of factors will render the actual 'equilibrium' level of oil according to the dipstick marks, including any variation off level for the aircraft between measurements, different loads in the baggage area, and as Bob has said, the time for oil drain-back into the sump following recent flight.

 

His recommendation, for calibrating the CAMit dipstick to the specific engine in the specific aircraft boil down to (and I am extrapolating here from his advice to me for calibrating the dipstick for a CAMit oil inhibitor installation onto an engine which is a Frankenstein monster of a Jab./CAMit combination build and almost absolutely the OLDEST basic Jab engine ever to have CAE improvements added): Get a known flat, level area for checking the oil level. Do a few reasonably brief flights, topping up each time after a decent interval to allow oil drain-back, and note the 'equilibrium' position on the dipstick that the actual engine shows. Then set the top mark on the dipstick to that.

 

The oil performs two functions. The first, is lubrication - and that requires a quite small amount - microns x each sliding surface area, plus enough to fill the pump, galleries and delivery tubes plus a bit to allow for friction losses throughout the system. The second, is cooling and that requires a heat transfer arrangement to a device to exchange heat - an oil cooler / heat transfer surfaces. Once again, (provided there is sufficient oil to effectively utilise all of the available heat transfer volume), there is no reason to carry more oil in the system (apart from enough to actually compensate for genuine losses through use) than is required to meet all of the second case requirements plus the first case requirements. So we're talking, the volume of the oil cooler plus the volume of the oil lines to and from, in addition to the normal engine lubrication requirement plus a 'comfort' margin. Any more than this, is simply carrying excess weight and a heat bank.

 

If you are going from very full to seriously low oil in just a few hours of flight: there is something WRONG with your engine and it needs attention. It is not a well engine - don't ascribe the facts to a basic flaw in oil volume!

 

Holding too much oil has potentially more damaging effects than holding slightly less than the maximum optimal. For a start - no pun intended - UNLESS you have a TOCA installed, bringing the oil up to operating temperature can cook the heads (or some of them, depending on your run-up attitude relative to wind direction). The standard Jab. oil temp probe sits in/close to the area of laminar flow across the sump, so the minimal cooling effect of the sump material in the under-cowl airflow will exacerbate this factor; excess oil in the sump will add to that incorrect reading.

 

We all tend to get very concerned if we find the oil reading low on the dipstick - but what is the incidence of Jab. engines seizing in flight from insufficient oil?

 

 

[Old Koreelah]

Part of the problem is the dipstick (the one in the engine!) The ideal oil level is the last few mm on the stick. Reading the oil level is not as simple as with, say a Diesel engine. Bubbles of hard-to-see oil sometime remain in the filler tube after topping up, coating the whole dipstick. A few dips are often required to get a believable reading. Add the parked angle of a taildragger and checking the oil level can become a lengthy operation. (I'd love to recalibrate mine to the parked attitude, but the stick would have to be longer...)

 

 

[jetjr]

Fill as requird, logging how much, at service measure whats in catch can and subtract from total added

 

Divide by hours and that's your burn rate

 

I generally add this volume at the end of a flight, means reading next start is more accurate.

 

 

[geoffreywh]

The amount of oil between the recommended level and the minimum level is just too little, It's about 150ml more or less. If your engine blows out (Not Burn) ( thru' reasons we don't go into here) 50mls per hour you have a MAXIMUM flight duration of x hours. IF EVERYTHING STAYS THE SAME!.......But Wait ! There's more...........Jabiru rings are well known to stick, I can show you some. Oil consumption could likely rise over 3 hours. Maybe dramatically. HOW WOULD YOU KNOW? If the oil reserve was 1 litre I would feel so much happier. We have to have petrol reserves, Why? when you have NO oil reserves? That's Stupid! My oil tank carries 6 qts. There is hardly a condition imaginable whereby I would run out of oil before petrol. Good Luck Jab.....( the capitals are deliberate. ) A catch / return system will go a long way to making me feel better....People have written about injecting oil into the sump as you fly along Great idea , but I have a better idea, put your extra oil that you carry INTO A LARGER SUMP IN THE FIRST PLACE.

 

The oil performs two functions. The first, is lubrication - and that requires a quite small amount - microns x each sliding surface area, plus enough to fill the pump, galleries and delivery tubes plus a bit to allow for friction losses throughout the system. The second, is cooling and that requires a heat transfer arrangement to a device to exchange heat - an oil cooler / heat transfer surfaces. Once again, (provided there is sufficient oil to effectively utilise all of the available heat transfer volume), there is no reason to carry more oil in the system (apart from enough to actually compensate for genuine losses through use) than is required to meet all of the second case requirements plus the first case requirements. So we're talking, the volume of the oil cooler plus the volume of the oil lines to and from, in addition to the normal engine lubrication requirement plus a 'comfort' margin. Any more than this, is simply carrying excess weight and a heat bank.

.

This is quite right. EXCEPT , the amount of rubbish (lead, ect ) collected in the oil (it is not filtered out, look inside your crankshaft) is then concentrated over a very,very small amount. To reduce that concentration you must carry more oil. I've seen oil come out looking like grey paint. I'd rather it looked more like oil.

 

 

[jetjr]

Not sure why you're saying afyer 150ml use you have to stop and refill oil to top

 

Plenty run well below lower mark all the time

 

If you are filling to top mark theres likely to be 100ml blown out in first 5 minutes, then drop to 30ml/hr or so.

 

Test bed engines have run with under 1.5 l for hours, and low level is seen as slightly increased temps

 

None i know are limited by oil capacity, mostly by bladder size of the pilot.

 

 

[Old Koreelah]

Thanks for all the replies, people. After considering all viewpoints I've decided against fitting an oil recycler; the extra weight and work would be better spent on installing a mechanism to add, on longer flights, a little oil in-flight.

Just happened on this old post. What was I thinking? On the longest recent flights my engine has burned/expelled only a few ml of oil. Not an issue.

[fly_tornado]

on a recent episode of engine masters they showed how too much oil not only robs engine of horsepower it drops oil pressure at mid range speeds.

 

 

[turboplanner]

Container of new oil, chainsaw bar lubricator pump, press the button every time you update your flight chart - improves the average oil quality, rather than deceases it.........simple.

 

 

[facthunter]

It would only do that if the rotating parts were dipping in the oil. The actual quantity of oil needed is small, but there are other considerations.. Small amounts need a better way to keep them cooled and not aerated. No air bubbles.. Very large amounts need a long time to reach equilibrium temps. Longer warm up.. Small amounts don't have as much margin if the motor starts using oil. The sump (if that's where the oil is) must be designed to use the lot otherwise the useable oil is less.. Nev

 

 

[Old Koreelah]

I maintain my oil at recommended levels. Pressure is always at the upper end of safe range.

 

The oil gets changed every six months or so, usually with less than ten hours operation.

 

 

[Old Koreelah]

Container of new oil, chainsaw bar lubricator pump, press the button every time you update your flight chart - improves the average oil quality, rather than deceases it.........simple.

I do have a bodgied-up version of the CAMit cylinder lube system. Before shutdown, run at high revs and give a shot of marine grade 2T oil from a squeeze bottle just downstream of the carby.

[facthunter]

. TCW3 marine TS oils are not recommended for aircooled motors. Your injection idea is a is a good one to protect the engine when not in use short term. I would wonder if you might risk some exhaust guide jamming potentially though.. They are NOT a high temp product. Various Two stroke oils are targeted at Piston ring land temps. The Rotax 582 doesn't recommend the oils used in outboards either and you might think they would but obviously the pistons must run hotter. in the Rotax. Nev

 

 

[jetjr]

CAE just uses std engine oil injected few ml into intake valve just as the engine stops

 

Appears to work well when you remember to do it.

 

 

[Russ]

 

 

 

[skippydiesel]

Been thinking of making up a catch can for my 912. I get the occasional oily sprinkle down my ships belly.

 

My "flask" of choice, at this moment in my imagination, is a "Red Bull" aluminium drink bottle with suitably located spigots. The fowl muck that is contained within can be consumed (if you have  a strong stomach) & replaced with a quantity of steel wool (as a condensing medium).

 

Got the empty flask, now need to find suitable spigots and work out some ingenious way of attaching them.

 

The 912 breather is a simple oil hose from the top of the oil reservoir emptying to atmosphere, at the bottom of the engine bay - shouldn't be too hard to install an in line flask to catch oil mist/droplets befor it exists the pipe.

 

 

[facthunter]

In turbulence, the Rotax oil tank will expel oil. It's not set up for any negative "G". If you flew inverted for any time you would lose most of the oil .  What do you want to do with the grunge you catch?  Nev

 

 

[skippydiesel]

In turbulence, the Rotax oil tank will expel oil. It's not set up for any negative "G". If you flew inverted for any time you would lose most of the oil .  What do you want to do with the grunge you catch?  Nev

I am not into aerobatic maneuvers but have experienced some nasty turbulence (Katoomba area in particular) - never associated the occasional oil spatter with those events but now you come to mention it you might be "right on the money"

 

The "cought oil" will be disposed of by adding it to the "44 Gal" drum I collect my  used automotive oil in. When full my local servo arranges for a waste oil pick up & I get an empty drum back.

 

In truth my only aim is cosmetic  - that is to keep my belly clean. An aluminium Red Bull bottle is not very big (size  & weight being the main attraction - the disadvantage was screwing up my courage to taste the contents ugh!). I do not anticipate"catching" much wast oil.