Use of 1/2" hose barb fittings on Metric 12mm Rotax oil hose

Guday Byron,

In Au it seems that metric barb type press on hose fittings are almost all imperial OD.

Having said that I don't recall having a problem fitting hoses, with a nominal 12 mm ID - they all have enough elasticity to accomodate the small difference between 1/2 & 12mm.

I have used a lot fittings from AeroFlow - they have a huge catalogue - https://aeroflowperformance.com/catalogue

Note: I strongly advise against traditional garden hose style multi barb fittings. Where available the latest automotive single barb/swelling type is a far superior product. (see example below)

I encourage you to brows, however Pages (from) 50 & 155 may be of particular interest.

I only use Rotax supplied hoses, when I can not find an automotive equivalent that meets or exceeds Rotax hose. 

Repco supply Gates radiator/coolant  & fuel hose :

COOLANT

There is a moulded 90 degree  bend, in diffrent "Arm"  length options

• PN 03-0010 ID 25.4mm, Arm 1 125mm, Arm 2 125mm  
• PN 03-0011 ID 25.4mm, Arm 1 300mm,  Arm 2 300mm 

Multi Fit Coolant Hose with two bends, a 135 & 90 degree

• PN01-007 ID 25mm Length 550 

Then there is 25 mm connectors

• Straight PN28606 
• Elbow PN28626 
• Tee PN28638 

FUEL HOSE

Barricade Fuel injection & Carburettor hose

OIL HOSE

Gates 8GTH oil hose (1/2 ID) comes from hydraulic service/supply shops eg Hydraulink

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Thanks Sean,

Yes aeroflow  make some really nice fittings, there barb style connectors are obviously the automotive type with just one “barb” some pushing the 12mm hose onto a 1/2” fitting is easier then you only have the binding on the smooth part of the fitting (not the multiple barbs on plumbing/air style fittings)

If only that single barb was just a bit smaller in diameter fitting the hoses would be a much easier job. The length of the fitting stem is half the issue some of them appear to be a lot longer than they need to be.

turning the single barb down on an aeropro style barb fitting to match the barb diameter of a Rotax fitting on a lathe sounds like the safest option.

Cheers,

Byron.

As stated , I have never had a problem fitting the correct ID hose to my various push on fittings. To help I usually use

silicon lubricants. A smear on the "barb" usually allows an easy fit;

The best aerosol is CRC Automotive - not cheap at about $26 AU - use sparingly

Silicon grease -  Molykote 111 - also not cheap at about $35. A tube lasts me several years.

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Byron

Rotax sell the oil fittings for the engine, oil tank and oil radiator in both metric and UNF.  In the case of the oil tank you have to buy the whole cover with the correct fittings welded on. The metric fittings are set up to accept 12MM hose and the UNF fittings that are made to adapt to AN-8 (1/2”) barbed hose fittings. 1/2” hose is 12.5mm ID and will fit loose on a 12mm fitting, while a 12mm hose will stretch to go on a 1/2” fitting but in my opinion neither should be done.  Use 12mm hose for 12mm fittings and 1/2” hose for 1/2” fittings. You might not want to change all the hoses now, but at least get it right at the next 5-year rubber change.

What drives me crazy is how many SLSA manufactures mix and match, something that would never happen in a certified aircraft. Typically this is a 12mm fitting used with a 1/2” hose, and it is loose and eventually leaks.  I’ve also seen what you are talking about, 1/2” fittings with 12mm hose, which over stretches the hose a bit and can also lead to failure. Equally as frustrating is that a lot of places that sell hose claim there is no difference in 1/2” and 12mm hose, but there definitely is.  

Hi Jeff,

Cant comment on what is available in the USA ,however here in Australia most hoses seem to be in imperial.

I use exclusively Gates hoses. The hoses have always been a pleasing firm/tight fit,  that delivers no leaks, even without a clamp. To date  (15+ years I have never had a leak, never actually checked my Rotax fittings for metric/imperial - assume metric.

Oil, 8GTH oil hose comes in 1/2" /12mm

Fuel, Barricade 5/16" /8mm  &  3/8" / 9.5mm

COOLANT

There is a moulded 90 degree  bend, in diffrent "Arm"  length options

• PN 03-0010 ID 25.4mm, Arm 1 125mm, Arm 2 125mm  
• PN 03-0011 ID 25.4mm, Arm 1 300mm,  Arm 2 300mm 

Multi Fit Coolant Hose with two bends, a 135 & 90 degree

• PN01-007 ID 25mm Length 550 

Then there is 25 mm connectors

• Straight PN28606 
• Elbow PN28626 
• Tee PN28638 

NOTE: No matter the hose or the "barb"/spigot, the fit should ALWAYS be firm. If in doubt, go the next hose ID down, to achieve a firm fit. Hose clamps are for security, not leak prevention.

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