Cylinder head crankcase breather inlet

[mbell]

Although I haven't heard of any cases of crankcase explosions without the mesh Lotus obviously thought it a wise precaution to have it.

I had backfire when starting my car, that managed to blow the oil cap of the car. Hard to know how far the flame penetrated through the engine but it certainly raised my heart rate and justified buying a new engine to airbox pipe with the flame trap. (New setup I am working on also has a flame trap.)

To the OP - don't forget to check the condition of your engine for piston ring sealing. If that's not right then everything else is moot!!

Planning on doing a compression test once its back together. Don't have the equipment for a leak down test, so will see how the compression test goes before deciding next steps.

[Donels]

I found my vent pipe blocked and rodded it through only to find I had removed the copper mesh. Should have read this topic first.
Any way cleaned it up and was going to just pack some wire wool in there until I read about the flame trap and exploding sump so checked for a new one. These are expensive for what they are!

Overnight I had a brain wave. I recently had the home oil fired boiler serviced and the guy left me with the removed nozzle, which appeared to be in excellent condition, but they always replace them. It has a Retimet filter (metal foam) to protect the nozzle from dirt and it's nearly the right size to fit the vent pipe.

So cut the nozzle bit off, dressed the end and just had to dress the threads slightly to get a snug fit then secure with some sealant.

You can blow through it and it’s lightly restrictive, it’s brass so should stop any flame. I can’t see any reason why it won’t work. I’ll let you know.

Dave

[mbell]

I can’t see any reason why it won’t work.

With reduce diameter I would be concerned about it limiting air flow, especially with oil build up on it.Leading to increased crank case pressure and oils leaks.

Since fitting a new vent pipe with mesh, I've been experiencing worse oil leaks from the sump gasket. It was freshly re-sealed when fitted the tube and have since re done it. Both times on first gentle short test run everything seems good and no signs of oils leaks. But then after longer more aggressive drive there are oil leaks.

My guess is that a mix of more aggressive driving creating more blow by and the mesh picking oil up on longer runs and becoming more restrictive. Leading to more crank case pressure and the oil being forced out. Of course it could just be me failing to fit the sump gaskets correctly but both times I was very careful in my selection of sealants and applications etc.

Likely going to see about an alternative breather arrangement and see how that effects the rate of oil leaking.

[smo17003]

Having read this thread last year and learning about the possibility of a flashback I checked my airbox to head pipe to find that there was no mesh fitted. Hunting around for a suitable mesh I found some smokers pipe meshes on Ebay. For a few quid I thought they're worth a try. I've only just started my rebuilt engine in the last few days, and I've yet to fit the airbox, so I don't know if it's been worthwhile or not.
These are similar to the ones I bought. https://www.ebay.co.uk/itm/174604202398 ... R87OmPH3YQ
I stuffed one into the rubber connecting hose rather than the tube. I'd be interested to know what others think, good or bad.

Cheers

Mike

[2cams70]

Having read this thread last year and learning about the possibility of a flashback I checked my airbox to head pipe to find that there was no mesh fitted. Hunting around for a suitable mesh I found some smokers pipe meshes on Ebay. For a few quid I thought they're worth a try. I've only just started my rebuilt engine in the last few days, and I've yet to fit the airbox, so I don't know if it's been worthwhile or not.
These are similar to the ones I bought. https://www.ebay.co.uk/itm/174604202398 ... R87OmPH3YQ
I stuffed one into the rubber connecting hose rather than the tube. I'd be interested to know what others think, good or bad.

The mesh should be copper like original. Steel or stainless steel does not have the thermal properties required to adequately quench a flame. You could possibly buy some copper mesh having similar fineness to the original and then cutting, shaping and soldering it using an original mesh as a sample.

Search for "copper mesh" on Alliexpress. Seems to be quite a bit to choose from on there.

[smo17003]

Thank you 2cams70 - back to the drawing board then.

[rgh0]

There are many variables in designing a flame proofing mesh. I dont believe it is critical its copper

here is an example in mild steel

https://wiremesh.co.uk/woven-wire-mesh- ... -proofing/

cheers
Rohan

[2cams70]

There are many variables in designing a flame proofing mesh. I dont believe it is critical its copper

here is an example in mild steel

https://wiremesh.co.uk/woven-wire-mesh- ... -proofing/

I had a previous life in the gas welding industry. Yes there's quite a bit of thought that goes into flashback arrestors. I think though that if Lotus came up with a design that they thought worked in the absence of any better information I know where I personally would be hedging my bets!!

Copper has better thermal properties than steel for this type of application. That's why you have copper soldering irons and why copper cooking pots are better than stainless steel ones

[rgh0]

I had a previous life in ethylene processing and furnace burner design. Like I say multiple facors such as:

Gas type e.g. A high hydrogen fuel flame is harder to stop through a mesh than higher molecular weight fuels due to high flame veloctiy and wide flamability limits and lower ignition energy
Gas flow velocity is important e.g. higher velocity prevents flame flow back through a mesh
Mesh size - small mesh better
Mesh depth - multiple mesh layers better
Mesh Material - a higher conductivity and specific heat mesh such as copper helps this is probably the least important factor and cant be used with many gases due to corrossion.

Whats done in oxy torch design is not the only way

cheers
Rohan

[2cams70]

T

I had a previous life in ethylene processing and furnace burner design. Like I say multiple facors such as:

Gas type e.g. A high hydrogen fuel flame is harder to stop through a mesh than higher molecular weight fuels due to high flame veloctiy and wide flamability limits and lower ignition energy
Gas flow velocity is important e.g. higher velocity prevents flame flow back through a mesh
Mesh size - small mesh better
Mesh depth - multiple mesh layers better
Mesh Material - a higher conductivity and specific heat mesh such as copper helps this is probably the least important factor and cant be used with many gases due to corrossion.

Whats done in oxy torch design is not the only way

With all due respect I think you are over complicating things for this particular application. If people think it's worth developing something they may think will work better than the original design then they are welcome to go right ahead. Personally I prefer to spend my time thinking about other things. A wire mesh in a breather tube doesn't excite me all that much. From observation and deduction I can see why Lotus designed this part the way that they did and I can see no worthwhile reason to change it when it's known to work.

[RichardHawkins]

Rohan and 2 Cams,

I don’t have your in industrial knowledge of flame traps, but I do remember an early school boy demonstration using a bunson burner in the physics lab. A metal stand was put around the bunson and I wire mesh put on the stand, the gas was turned on and ignited beneath the mesh, the flame did not propagate until the mesh was glowing. The experiment was repeated but this time the gas was ignited above the mesh, and again the flame did not propagate until the mesh was glowing.

What this tells us about our old cars I don’t know, but this discussion triggered my memory.

Richard Hawkins

[Craven]

Humphry Davy sussed this way back, December 1815,
Davy made various prototype lamps. The final design was very simple: a basic lamp with a wire gauze chimney enclosing the flame. The holes let light pass through, but the metal of the gauze absorbs the heat. The lamp is safe to use because the flame can't heat enough flammable gas to cause an explosion, although the flame itself will change colour.

[rgh0]

T

I had a previous life in ethylene processing and furnace burner design. Like I say multiple facors such as:

Gas type e.g. A high hydrogen fuel flame is harder to stop through a mesh than higher molecular weight fuels due to high flame veloctiy and wide flamability limits and lower ignition energy
Gas flow velocity is important e.g. higher velocity prevents flame flow back through a mesh
Mesh size - small mesh better
Mesh depth - multiple mesh layers better
Mesh Material - a higher conductivity and specific heat mesh such as copper helps this is probably the least important factor and cant be used with many gases due to corrossion.

Whats done in oxy torch design is not the only way

With all due respect I think you are over complicating things for this particular application. If people think it's worth developing something they may think will work better than the original design then they are welcome to go right ahead. Personally I prefer to spend my time thinking about other things. A wire mesh in a breather tube doesn't excite me all that much. From observation and deduction I can see why Lotus designed this part the way that they did and I can see no worthwhile reason to change it when it's known to work.

I agree I am over complicating it. But i was just trying to point out that it does not have to be a copper mesh. There are many statements made with absolute certainty on the internet that fail to address the actual complexity of many engineering situations.

Personally i have never worried about the mesh effectiveness as the chances of having an explosive mixture in the sump of an Elan at the same time as an ignition source is present in carb air box is close enough to zero for my purposes, just my opinion. People should stick with the orginal compoents and parts where ever possible.

[999timd]

i know this thread is old but has anyone done the 45deg angled tube into the exhaust that creates a vacuum and plumbed the breather straight into it. I understand it will blow some oil into the exhaust but the benefit or creating some negative pressure inside the engine would assist with oil leaks due to positive pressure? I know the early hot rodders use to do this to help with piston sealing "Crankcase evacuation kit" thanks

[rgh0]

If worried about venting the crankcase breather to the carb intake box just vent it to a catch tank. If worried about the size of the breather just install a bigger one on the cam cover. The "venturi effect" of plumbing into the exhaust would need a lot more than just a 45 degree angle input tube to be of any use and is not needed in my personal opinion or experience

Just my opinion, happy to further discuss the fluid flow details around crank case venting if needed.

cheers
Rohan