912iS oil pump inlet adapter - retaining compound?

Hi Steve

I think you are referring to the inlet fittings, metric or UNF, for the oil line.  There is no outlet, that would be the filter into the engine.  

That said 648 is green and suited for this purpose.  This recommendation has been out for a while.  A look at the Henkel website, the people who make it, it is ideal for preventing loosening and leakage from shock and vibration.  It is a green, low viscosity, high-strength, anaerobic-curing retaining compound.  The other thing about it is that it will work even with passive substrates like stainless and plated surfaces.  The other big thing is that it works with minor surface contamination of oils without a primer or cleaner.  It works up to 180C (355F) temperature also.  

To be clear, the fittings it is used on have a copper compression washer between the fitting and pump.  The Loctite is applied to the thread when you mount the hose to the pump.  I know that the drawing in the heavy manual is a bit small but that is what it shows.

Cheers

Hi Wizard,

Thanks for the speedy response. I'm new to this, but I was trying to use the terminology from the installation manual (attached below). I'm moving the adapter from position 4 to position 5, and the drawing refers to that as the outlet fitting. 

Also, the Heavy Manual says to use Loctite "if necessary". Can you help clarify what that means? Is it required, optional, or recommended? I have no idea how to determine if it's "necessary". 

Best,

Steve 

Hi Steve

The oil pump has the oil inlet for the pump.  The fittings on the lower crankcase are oil return but have nothing to do with the pump.  On the injected engine crankcases you have 3 positions.  The ones near the ignition side are opposite each other.  Use one or the other if you have an installation that when flying these would be the lower position for oil recovery from the crankcase, generally all tractor installations.   If this is a pusher application, such as say a gyro aircraft, then use the one nearest the oil pump body.  

When using a 37 degree fitting, both the metric and the UNF ones used by Rotax for example, normally no thread locker is used.  In general a small lubricant is used on the 37 degree surface to allow for the fitting to seat smoothly.  For security some prefer to use of Loctite on the threads for secretly.  

I dont know the installation, type of aircraft or hose producer, so it would be best to discuss this with your OEM or other builders of the same aircraft type for suggestions. 

Cheers

Hi Wizard,

Thanks for taking the time to explain, and your explanations are clear and helpful. I think I understand now. To complete the picture, I'm building a Kitfox SS7, and the FWF kit from Kitfox included premade hoses for the oil system.

I do have one more mostly related question... Loctite 648 is a retention compound, and in reading about it, it appears to be designed to seal/bind smooth surfaces. From the Henkel website -- "A 1-part, low-viscosity, high-strength, anaerobic-curing retaining compound is designed for bonding cylindrical fitting parts."

Since this application is putting it on threads, it seems like an odd product to use in this case. Any idea why Rotax specifies a retaining compound vs a thread lock? 

Thanks,

Steve 

Hello again Steve

Rotax uses Henkel, Loctite, products almost exclusively.  They work directly with Henkel as an OEM engine builder.  648 has found many uses that are other than cylindrical bonding.  Many european auto makers also use this in assemblies other than just press fit parts.  The main reasons are the tolerance to shock loads and high temperatures.  The 648 has a very low viscosity (thinner) than 638.  When cured the gap fill is also a factor.  

As a note, never put this on the 37 degree sealing face, only the thread. I personally believe the reason this is called out is the high tolerance to light oils left on the parts from production.  Most threadlockers will not work with oils present on the threads. 

Cheers