Only for mechanics

[OldBawley]

Only for Mechanics.

New oil cooler for gearbox

The oil cooler for our Paragon transmission is at its end. Electrolysis holed the brass cooler mantle on a few places. Hairpin holes in the brass leak minute quantity's of ATF oil, wont be long before the oil pressure will kill the cooler.
The bowman heat exchanger of the Perkins 4108 had electrolysis problems too, so when I discovered a small heat exchanger on a pile of metal junk next to a Greek garage I bought it for 10 €.
I discovered the pinholes a week ago, now I have time to repair. Digged the second hand cooler out of half a ton of spares, and was lucky. The new cooler is a bit bigger but has the same thread as the old one for the oil pressure hoses. Thank God. The connections for the seawater hoses are bigger, so I had to improvise.
Hose inside diameter 32 mm, cooler connection 43 mm. To big a difference for a flexible hose.
Main problem is my location. Sailing in Greece means getting material is difficult if not impossible.
Second problem is that those oil coolers are soldered together in a stepped way, maybe even with different types of solder for each weld. That means no soldering or welding on the cooler or it will leak and or fall apart.
So I decided to glue brass inserts into the cooler.
See sketch
The new old cooler had been used to cool a small engine. Where I want to cool hydraulic oil, they had been cooling anti freeze . So I cleaned the inside as good as possible with caustic soda ( Drain cleaner ) and hot water.
I have a small hobby lathe on board so theoretical I could turn brass bushings to fit into the cooler en take the water hoses. Again Greece, so no way to buy brass except for one shop in Pireaus.
To far out of my way so I bought two brass trough hull fittings in the local farmers shop. One fifth of the price a chandler wants.
Now the flange of the trough hull is made a tight fit with the bore of the cooler. That way both are centred. Then I want to use ordinary Polyurethane glue / sealant ( Sicaflex ) to glue the trough hull inside the cooler. About 3/ 64 “ clearance between cooler and trough hull, which is fine I think.
Then I want to fill the thread of the trough hull where it takes the hose with the same polyurethane to prevent water leaking trough the tread.
Last thing to do is mount the cooler with a sheet of isolating rubber so no stray electrical current can flow.
Now up to the mechanics, what did I do wrong ?

 

[RichardS]

The principle looks fine to me but the issue would be whether polyurethane sealant is suitable for a metal to metal seal at elevated temperature, although I don't know how elevated. I think I would use a permanent epoxy resin (select dependant upon temp required) and maybe try the rubber hose end without sealant (just silicone grease) or, if the rubber is not soft enough to fill the threads and if you have the clearance, take off the thread until it's smooth.

Richard

 

[OldBawley]

Thanks for the remarks.

Epoxy is fine stuff, but for boats ?
I live on, and have rebuild a wooden boat. Real solid wood. Tried epoxy for many purposes, no good. Epoxy is not flexible, it breaks.

I think that epoxy between two brass pieces would break also. Polyurethane is flexible, very flexible if applied in a thick enough layer.
I followed two workshops for yacht window sealing ( and selling ) by Sikaflex. They recommend a 3 mm thick layer of sealant between a grp hull and acrylic or Lexan windows.

I guess the max temperature of the Hydraulic gearbox and cooler is 60° C. Bit more than hand warm. Old design engine , gets 85 °C.

Taking off the thread would lower de diameter to 30mm, the reinforced Rony flex coolant hose is constructed for 32 mm.
I have liquid gasket silicone in my chemical locker, that would be fine to seal the thread. Could be better than polyurethane because if I use Sikaflex it would be almost impossible to take the hose off the cooler without cutting it open en ruining it.
Jepp! didn´t think of that.

 

[RichardS]

This is the sort of stuff I had in mind, http://www.jb-weld.co.uk/j-b-weld-epoxy-adhesive/j-b-weld-marineweld-epoxy-adhesive or similar "liquid metal" type epoxy.

It will be like welding the two metal components together. Of course, they will never come part again unless you use a blowtorch but I think that's OK. I don't know enough about Sikaflex and hot oil in a vibrating environment to know how oil tight that's going to be.

I agree that 30mm and 32mm is not going to work so the liquid gasket plus hose clip sounds good. The "Rolls Royce" option would be to see if you can find a piece of smooth metal piping which will slide over the threads but have the 32+ od that you need for the hose. You could then coat the threads with the above epoxy and slide a short piece of tube over. Once again. this will form a permanent spigot but will form a good hose fitting.

Richard

 

[OldBawley]

First I have to explain that only cold seawater is going trough the glued parts. The hot oil is circulating around the pipe stock ( Left on the sketch )

The Jbweld would probably be a better solution than the Sikaflex.
Very good chandler here in Poros, will have a look as he stocks the stuff.

The hose connection will be ok, I don't doubt that. In fact a polyurethane filled threaded spigot must be about ideal.

 

[Sarnia]

First I have to explain that only cold seawater is going trough the glued parts. The hot oil is circulating around the pipe stock ( Left on the sketch )

The Jbweld would probably be a better solution than the Sikaflex.
Very good chandler here in Poros, will have a look as he stocks the stuff.

The hose connection will be ok, I don't doubt that. In fact a polyurethane filled threaded spigot must be about ideal.

As an engineer, I consider your choice of Jbweld to be ideal for your purposes under the conditions you are faced with.
Ideally I would have liked to make from a solid bar, using a lathe, a piece, bored out, to fit at one end into the oil cooler (shrink fit) and the other to suit the flexible tube, but needs must and I feel you have arrived at a good solution.

 

[prof pat pending]

+1 from another engineer :encouragement:

To the OP I'm afraid your thoughts on epoxy are some way off the mark.
Boats, aircraft and performance cars are all pretty much bonded together these days. You do need to choose the correct resin system for the job, not all epoxy systems are the same

 

[ribrage]

Just a thought - can you not get a brass reducer ? rubber hose from cooler to reducer and then smaller hose straight onto the other end of the reducer

usually readily available in hardware shops and DIY stores etc.

 

[OldBawley]

Thanks for all the thoughts.

After long deliberation ( In bed during a gale ) I think I go for the polyurethane bond.
Let me explain.
The outer cooler gets hot. My glued in trough hull stays cool by the flow of cool seawater. There is a 3/64” clearance between both brass parts filled with the bonding material.
So the outer piece will expand, the inner piece won´t.
I know were talking about very small movements. Epoxy does not move at all. The seal will break. Maybe only after 50 start up´s. Sikaflex or any other polyurethane will move.
There is also the small problem of cleaning the thread before applying the sealant. Brass has a coat of oxide that is immediately replaced if removed. Epoxy is high tech rocket science toxic ( allergy ) stuff that needs ideal surfaces to bond with. Polyurethane sticks to anything forever. Just get Sika on your hands and you know.
Furthermore, I have to find and buy the JB weld, the polyurethane is on board and can be used for two or more jobs.
About turning from a solid bar or even buying a reducer, remember, this is a Greek island. Getting raw material ( even good wood ) is a specialists job. Anything is possible if you have time, patience, lots of money and a good translator / adviser. After all that you will eventually get something that resembles what you wanted.

 

[prof pat pending]

Actually the surface preparation for polyurethane bonding is just as critical as it is with epoxy. The fact that you will have a flexible joint rather than a rigid one increases the need to do it properly.

 

[vyv_cox]

Personally I would take a two-pack system (e.g. epoxy) over a single pack one (e.g. Sikaflex) every time. A filled epoxy joint used in the planned way will be a permanent joint, extremely strong with very little risk of it breaking up. Whole boats are built in this way nowadays. Although I am one of Sikaflex' most fervent fans I would not be using it like this.

 

[OldBawley]

Greek economy solved my dilemma.
The chandler had no JB weld, the Chinese stuff he stocked could easily be way over shelf life.
Ordering from his dealers in Pireaus would be a gamble too. I trust Spiro the chandler, not the guys over in Athens. Remember, I have been a chandler myself.

Have a product (Jel flux ) used to clean metal before hard soldering, will use that stuff seconds before applying the polyurethane.

 

[prof pat pending]

That's really not a good idea. One of the main ingredients of that type of flux accelerates the cross linking of polyurethanes. Many polyurethanes are sensitive to this.
I really don't know if this is one thing of them, but unless you are absolutely positive that there won't be an adverse reaction you're best not use it.

 

[OldBawley]

That's really not a good idea. One of the main ingredients of that type of flux accelerates the cross linking of polyurethanes. Many polyurethanes are sensitive to this.
I really don't know if this is one thing of them, but unless you are absolutely positive that there won't be an adverse reaction you're best not use it.

Thanks for the warning. I was already doubting using the stuff. It is a jell that starts cleaning if the metal and flux is heated in order to solder. Would have been a complete disaster.
Will clean the metal with a steel brush and sanding paper.
Btw, I have great confidence in Polyurethane of the Sika type as a glue.
Some years ago we ware mainly sailing Turkey. Some of our tan sails ware 30 years old, the sewing thread of the seams started parting. No sail maker out there did tan sails or UV resistant sewing thread so I cut two inch wide strips out of an old tan sail and glued them with brown Sika onto the seams. Both sides. The seams ware stronger than when new, still flexible and above all, it looked very high tech.

 

[prof pat pending]

After you've wire brushed it, nail varnish remover will clean it properly if that is easier to get hold of than acetone.

perfect solution on the sails I've done a lot of over mouldings with similar materials over the years to make 1 off parts for cars. Still not convinced about this use though...sorry

 

[vyv_cox]

After you've wire brushed it, nail varnish remover will clean it properly if that is easier to get hold of than acetone.(

OldBawley is in Greece. No ridiculous restrictions there, acetone is available in almost every supermarket, as are hydrochloric acid, solvent naphtha and other liquids that UK buyers are deemed too stupid to be able to use

 

[Heckler]

OldBawley is in Greece. No ridiculous restrictions there, acetone is available in almost every supermarket, as are hydrochloric acid, solvent naphtha and other liquids that UK buyers are deemed too stupid to be able to use

I love it here in Portugal, all sorts of potions available in the supermarkets as you say and cheap! I paid £14 for 500 mls of acetone in Milford, here its 3 or 4 euros!
S

 

[heart of oak]

http://www.autosiliconehoses.com/si...straight-reducer-45mm-to-32mm-15-colours.html

I wouldn't run the risk of a bodged repair to any system that has the ability to sink my boat........Reduction hoses are available in most sizes at a reasonable cost...

SK

 

[OldBawley]

Those reductions are a nice new development. Silicon..

As I have mentioned before, the problem is not the cost, it is the availability of parts, material and logistics.
Greece is having big problems. I am out of medicine, pharmacist says there is a shortage of some medicine. Our neighbour had medicine for his dog sent from abroad with a well known carriage company. He could follow his package up to the Greek border. Then it went missing
.
Anyway, my repair is not bodged. The inserts have been made to fit on my lathe, have given the polyurethane a week to cure. Tested up to 2 bar. Mechanical strength tested with my hands, no way that is going to part. The seawater flowing trough the cooler has no pressure.
Waited for a calm period to start removing the old cooler. Remember, one screw removed and the engine is useless. Managed to take everything apart without breaking stuff. Not that obvious with a 37 year old engine and prop installation.
Now cleaning and painting a bit , make a new support for the new bigger cooler and tomorrow put the whole thing together again.

This repair is sort of typical for our sort of cruising – life.
I am proud to have restored our old boat, made a comfortable live aboard out of it without changing the traditional look and had no one else work on my boat in all of those 28 years.

Most other sailors I see passing would hire a mechanic to do the repair. I have no idea what a new oil cooler and installation would cost nowadays. Maybe one of you knows.

 

[Mr Cassandra]

We have a policy in the yard Absulutly no sicoflex ......Simpson's only.