Lay up in humid conditions

by Hann Redwin in General Tech Discussion 7 years ago

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Re: Lay up in humid conditions

by Hann Redwin » 7 years ago

Hann Redwin

2 5 0

Dear Mr Hertzel,

Thank you for your full reply and apologies for the delay in not getting back sooner.

I have ordered an Eheim 200 3702 fish tank Air Pump which has a dual adjustable pressure output and scores well in the reliability stakes. Further, as suggested, I've looked at the Fumoto oil change valve on http://www.quickvalve.co.uk but am unsure which to purchase. I would welcome a telephone conversation with your good self as I have further questions relating to the possibility of refining a prototype.

Do you think we can do this ? My details should be on the database, otherwise do send me some contact details.

Sincerely.

Hann

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Re: Lay up in humid conditions

by Bill Hertzel » 7 years ago

Bill Hertzel

13 1.95k 7.96k

Hi Hann,

The parts manual shows that the Oil Return Threads on the bottom of the crankcase are M16-1.5
I recommend that you actually measure yours before ordering.

Before pulling the plug. "Burp" the Oil Tank and be prepared for a small cup of oil to drain out with the plug removed.

If it is in fact M16-1.5 you will want the F-108N Valve with the Hose Nipple.

Bill.

Bill Hertzel
Rotax 912is
North Ridgeville, OH, USA
Clicking the "Thank You" is Always Appreciated by Everyone.

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Re: Lay up in humid conditions

by Hann Redwin » 7 years ago

Hann Redwin

2 5 0

Once again thank you Bill.

I have contacted www.quickvalve.co.uk and ordered the F-108N with the integral hose nipple. Richard Griffiths the Technical Director of the company suggested that as an additional safeguard, a safety clip to the turret of the valve mechanism should be used too. So far so good.

The objective in this idea would be to have a closed loop system. Rather than have the outflow of the desiccated air spill out of the exhaust pipe, I would like to reintroduce this air back into the silica gel, through the fish tank pump and then back into the Oil Return Plug ....... thus maximizing the desiccate time/time usage by frustrating the introduction of ambient air.

The challenge for me is to see if this idea is flawed, or/and what would happen to this arrangement should the air pump fail. Having experienced the oil purging technique for the Rotax engine first hand, you will understand why I'd rather not have to do this again. I want to make sure that the input oil line does not get accidently "bubbled" in my endeavour to dry the air within the engine chamber.

In paragraphs :-
1. "It would be possible to vent the crankcase, as Rob suggested, by blowing air in one of the unused Oil Return Plugs in the bottom of the crankcase. This would require an air pump that could produce at lease 1-2 PSI and a few Liters or so of air per minute."

I assume that this 1-2 psi would be sufficient to push through the oil in the return line and into the external oil tank, which in turn would allow the desiccated air to vent into the external oil tank. Would you recommend that the filler cap be unscrewed ??

2. " ........... and the flow rate will need to overcome any leakage through any piston ring that has an open valve above it."

If as I propose, the system is a closed loop, then would the pressure differential on the piston rings under the open valve be any cause for concern ? Are we looking at just a leak down of residual oil on the ring grooves or is there something more fundamental that I need to understand ? It is here that I sense a cause for concern. Could a prolonged "drying", especially of the open cylinder, cause undue wear during start up due to lack of oil in the oil ring grooves ? If so, could the answer be to have less air pressure within the system ?

The Rotax engine is a wonderful and expensive piece of kit. It falls on me to do the best I can to inhibit the progress of rust on this my asset, especially during lay ups. Water condensation permeates everything and is the bane of everything shiny; if I can do something to frustrate and mitigate it's progress, it would see me a happier man. A collaboration of ideas is something I do appreciate.

In anticipation, I thank you again.

Hann

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Re: Lay up in humid conditions

by Bill Hertzel » 7 years ago

Bill Hertzel

13 1.95k 7.96k

ADMINISTRATOR,
The Rules talk about Private Messaging, PM-ing, but I can find no PM section on the Forum. Help!
*****************************************************

Hann,
The Air in the top of the oil tank goes out the open vent hose directly under the cap.
I see no reason to open the cap and risk getting dirt/dust in the Oil.

The Specs on the pump you choose show it can pump into to 2 meters of water.
Unless your Oil tank is over 6 feet above the engine, it should not be a problem.

The Only flow I envision going out the cylinders and exhaust is going to be the minuscule amount that blows through the end gap of the piston rings. A pin hole. It will not be much, but at least it is in the correct direction.
I do not see the pressure back flowing the Oil in the engine because the pressure is also on the intake side of the oil pump, so the oil is in equilibrium with the crankcase pressure. The usual concerns about the oil draining due to gravity is the overriding factor. Unless the layup extends into years, it is not a problem. Hand rotating the engine twice a year until oil pressure is produced is the best option.

Consider that after shut down, the only gasses in the crankcase are the exhaust byproducts.
These gasses are mostly carbon dioxide and water vapor.
As they cool they will condense into what is essentially soda water, Carbonic Acid, a weak acid.
The drying system pushes these gasses/vapors primarily out the oil vent line.
There is nothing in these gasses that you should consider valuable in recycling for another pass.
The CO2 is to be avoided and the water level will be much higher (100%???) than the atmospheric air you will be introducing.

If I did the numbers correctly, A pound of SilicaGel will last over a year drying 90% humidity air 24 hours a day with your air pump.

I do not understand your concern with an Air pump failure.
The common pump failure mode is a torn diaghram resulting in low but not zero pressure.

A power failure results in zero pressure and is much more likely.
If the pump is installed low The residual oil in the crankcase, (A few Ounces) will flow into the pump making a mess. This will not affect the engine other than the loss of a few ounces of oil.
This is a common concern in the aquarium hobby during a power failure.
The solution is to install the one-way valve in the air line that is recommended in the instruction that came with the pump, or place the pump above the oil level in the oil tank, or at least loop the air line above the oil tank on the way to the pump. Oil will not flow uphill.

Bill Hertzel
Rotax 912is
North Ridgeville, OH, USA
Clicking the "Thank You" is Always Appreciated by Everyone.

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Re: Lay up in humid conditions

by RotaxOwner Admin » 7 years ago

RotaxOwner Admin

59 1.58k 13.9k

ADMINISTRATOR,
The Rules talk about Private Messaging, PM-ing, but I can find no PM section on the Forum. Help!
*****************************************************

Say Bill, thanks very much for bringing that to my attention. That help file is something years before my time, and I haven't actually even read it before (It's tucked away pretty good...)

Our site does not, never has, and never will have a PM function. I suppose that Rules page was a cut&paste job by the Previous Administration.. I am cleaning it up right now!

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Lay up in humid conditions

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