I hate banjo joints ...

[dgadee]

I've stripped threads from a fuel pump and had to retap, accidentally destroyed one brass banjo bolt with too much heat, never seem to be able to get the correct size of copper washer, have problems in locating correct bolt sizes, always have at least one weeping, ...

I presume I must be alone in my problems, since they seem to be making a comeback in brake systems.

Can anyone point me in the direction of a treatise on 'Everything you wanted to know about banjo joints'?

 

[Jcorstorphine]

Copper washers, bolts etc

I've stripped threads from a fuel pump and had to retap, accidentally destroyed one brass banjo bolt with too much heat, never seem to be able to get the correct size of copper washer, have problems in locating correct bolt sizes, always have at least one weeping, ...

I presume I must be alone in my problems, since they seem to be making a comeback in brake systems.

Can anyone point me in the direction of a treatise on 'Everything you wanted to know about banjo joints'?

I know the problems only too well as Banjo fitting were used inside Vacuum Furnaces I used to design. They were used to seal flexible hoses to cooling lines and they were very prone to leaking. One drop of water goes a long long way when turned to vapour at 1/1,000,000 of an atmosphere.

The answer is very much along the lines you have mentioned in terms of correct size etc but one of the worst areas is where the thread on the Banjo Bolt is sometimes undercut at the hex. This causes the copper washer or Dowty Seal to sit “off centre” Other problem was that fitters used too much grunt when tightening them up and distorted the seal.

Even with so called annealed copper washers, I used to get the guys to further anneal the washers by heating them to a red heat and plunging them into cold water so as to soften them.

 

[Dipper]

Even with so called annealed copper washers, I used to get the guys to further anneal the washers by heating them to a red heat and plunging them into cold water so as to soften them.

I don't like banjo fittings either. I'm always too scared to do them up tight and then they leak. That tip about annealing the copper washers is useful. Thanks.

 

[ianabc]

heating on electric stove burner

Heating the copper washers or packing in Yanmar speak, to dull red ( only appears dull red in a darkened room) and dropping copper washer in cold water aneals and softens the washers so that it makes as good diesel seal.

I find 20 percent of the washers had so much slag that they have to be trashed.

 

[Beyondhelp]

When I work with things with banjo bolts I'm always amazed how tight people have done them up before me... and these are into steel/alu. Personally as already said its down to keeping everything clean and using correct washers. I see some washers that are like O-O if they are like that cut them in to separate O washers. When tightening the bolt if they are not allowed to move they can stretch and leak.

 

[rotrax]

I've stripped threads from a fuel pump and had to retap, accidentally destroyed one brass banjo bolt with too much heat, never seem to be able to get the correct size of copper washer, have problems in locating correct bolt sizes, always have at least one weeping, ...

I presume I must be alone in my problems, since they seem to be making a comeback in brake systems.

Can anyone point me in the direction of a treatise on 'Everything you wanted to know about banjo joints'?

Motorcycle hydraulic brake lines use banjo fittings. Have a look in a good bike shop spares counter-they should be able to offer something suitable. If it can take hydraulic brake pressure it should be OK. I always used new washers when installing then and found the quality and reliability good.

 

[CreakyDecks]

Am I the only one who saw the title of this thread and thought it referred to a seedy club frequented by George Formby fans?

 

[nigelmercier]

Am I the only one who saw the title of this thread and thought it referred to a seedy club frequented by George Formby fans?

Showing your age, and mine

But WTF is a banjo joint?

 

[Norman_E]

Showing your age, and mine

But WTF is a banjo joint?

There are 3 of them in this picture (Poor quality, scanned from an old photo) of the engine of my old Velocette Venom. They connect the oil drain tube fom the rocker boxes to the pushrod tube.

 

[graham]

I dont allow joints on Banjo. Dont like the smell.

 

[dgadee]

As the op I came across a possible solution - anyone used Dowty washers?

http://potterassoc.com/PDF/o_rings/Bonded Seal Information and Sizing Chart.pdf

 

[Jcorstorphine]

As the op I came across a possible solution - anyone used Dowty washers?

http://potterassoc.com/PDF/o_rings/Bonded Seal Information and Sizing Chart.pdf

Sorry but in my opinion, these make a poor fitting worse. The reason is that they have to be fitted exactly central to the bolt and if the faces have been bevelled off by the machining operation, the little nitrile seal sits in fresh air and you end up trying to get a seal on the aluminium carrier.

One point is that if you use copper washers, you have to make sure they are softened. Hold them in a flame until cherry red and then drop into cold water, clean off the oxide layer and you may have a chance of making a seal.

Regards John

Spent my entire working life getting things leak tight to less than 1 x 10-10 mbar litre per second. Now I am the one who leaks.

 

[VicS]

When annealing copper washers it is not necessary to quench them in cold water.

Just heat to a dull red and allow them to cool naturally.

 

[savageseadog]

This is like the CAV filter threads I keep seeing, a decent working piece of engineering ruined by bungling amateurs.

 

[sailorman]

When annealing copper washers it is not necessary to quench them in cold water.

Just heat to a dull red and allow them to cool naturally.

I noticed the same suggestion on another thread, it seem a strange thing to do

 

[VicS]

I noticed the same suggestion on another thread, it seem a strange thing to do

I am not a metallurgist and its along time since I studied the subject at all.
However, when you quench things its to preserve a crystal structure that is stable at high temperature. Which is why you quench steel to make it hard. You are preserving the structure that is the stable one at the temperature from which the steel is quenched. In the case of steel that structure is much harder than the structure to which the steel will revert if it is cooled slowly.
(Steels of course can also be tempered to produce intermediate properties. Heat treatment of steel is a complex subject)

In the case of copper there is no change in crystal structure at different temperatures. Work hardening is caused by physical deformation of the crystal structure. The natural structure reforms when the metal is heated. It does not mater if the copper is then quenched or allowed to cool slowly.
Overheating or maintaining the high temperature for too long causes excessive grain growth so that should be avoided. Perhaps thats a reason for cooling large objects quickly.

 

[mcframe]

Am I the only one who saw the title of this thread and thought it referred to a seedy club frequented by George Formby fans?

Can you imagine what an "Accordion joint" must be like? ;->

 

[aluijten]

Volvo Penta uses soft aluminum washers instead of copper (at least on my engine). As long as you use them only once the system works excellent is my experience. Trouble starts when you are working on the engine and discover you do not have any spare washers and re-use the old ones, or even worse use one of the wrong size.

 

[Heckler]

This is like the CAV filter threads I keep seeing, a decent working piece of engineering ruined by bungling amateurs.

+++++1!
Stu

 

[Heckler]

I am not a metallurgist and its along time since I studied the subject at all.
However, when you quench things its to preserve a crystal structure that is stable at high temperature. Which is why you quench steel to make it hard. You are preserving the structure that is the stable one at the temperature from which the steel is quenched. In the case of steel that structure is much harder than the structure to which the steel will revert if it is cooled slowly.
(Steels of course can also be tempered to produce intermediate properties. Heat treatment of steel is a complex subject)

In the case of copper there is no change in crystal structure at different temperatures. Work hardening is caused by physical deformation of the crystal structure. The natural structure reforms when the metal is heated. It does not mater if the copper is then quenched or allowed to cool slowly.
Overheating or maintaining the high temperature for too long causes excessive grain growth so that should be avoided. Perhaps thats a reason for cooling large objects quickly.

Not being vexatious, as an apprentice I was taught dull red then quench. Always worked for me. Slag forms when it is oxidised, so maybe they get it too hot for too long?
Stu