Fitting a Cast Iron Liner into an aluminium Barrel

I have a couple of cast iron cylinder liners about 2 1/2" diameter that have to be fitted into an air cooled aluminium cylinder casting.

The engine is air cooled so it is essential I get the correct fit to ensure the aluminium is always in contact with the cast iron liner. I don't want to find that as I get the liner part way into the cylinder the whole lot jams up and I end up having to drive it out but at the same time I don't want the liner to have lose contact with the cylinder casting when he engine is at the high end of working temperature, say 100 degrees Celsius.

Is there a standard figure/inch of diameter that can be used that will allow this? If not does anybody know how companies like BSA and Velocette produced engines with Cast Iron liners fitted in alloy barrels?

Bob, when I was making branding machines we needed to ensure full heat transfer with no air gaps between the element and the housing, and we used "Heat sink compound" to fill in the gaps. It was a white sticky stuff and stayed sticky, and filled in the gaps.

Chris Gunn

Bob,

Metals expand with heat as we all know. Its called the coefficient of expansion.... Linearly it is expressed as :

New length=Original length x Alpha x temperature,where Alpha is the metals coefficient of expansion...and the temparature is the difference from ambient to whatever the metal is exposed to....

Have a Google for volumetric expansion....

Some engine makers cast the aluminium around the liner to avoid ' cold spots' or should that be hot?😀

Edited By John Rudd on 23/11/2016 19:38:03

The cylinder must be light press fit into the aluminium cylinder casting.

Bob,

The originals were Wellworthy Alfin, which was not [if I recall correctly] a simple mechanical fitting process.

This may be of interest: **LINK**

http://archive.commercialmotor.com/article/5th-march-1954/49/new-foundry-increases-al-fin-output

MichaelG.

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Edit: This patent is for the pistons, but the process is, I think, generic.

https://worldwide.espacenet.com/publicationDetails/originalDocument?CC=US&NR=4997024A&KC=A&FT=D&ND=&date=19910305&DB=&locale=

Edited By Michael Gilligan on 23/11/2016 19:45:04

Bob, I am not expert by any means, but my thoughts are that normally the cast iron cylinder liner is made a "push-fit" into the aluminium cylinder barrel. By "push-fit" I take that to mean that it means it slides in without jamming but requires some effort to push it in, it does not slide in on it's own under gravity or be a "sliding-fit" requiring minimum effort. This ensures that, within the limitations of machined surfaces, the cast iron is in the closest contact with the aluminium in it's cold state as possible.

Now, if memory serves me correctly, the coefficient of thermal expansion for aluminium is about twice that of cast iron, which would lead one to think that the aluminium would expand away from the cast iron. But, the cast iron, being nearest the heat, gets hotter, and quicker, than the aluminium and gets all close and personal with the aluminium.  The aluminium, having cooling fins, dissipates the heat faster than the cast iron can transfer it to the aluminium, and so the close fit is maintained.

That is my take on it, no doubt there will be someone to come along and blow it out the water, but I hope it helps you.

Chris

Edited By ChrisH on 23/11/2016 19:50:27

Looks like this is the patent for barrels: **LINK**

https://worldwide.espacenet.com/publicationDetails/originalDocument?CC=GB&NR=732944A&KC=A&FT=D&ND=3&date=19550629&DB=EPODOC&locale=en_EP

MichaelG.

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Oops ... that's the wrong one ... I will have another look

Edited By Michael Gilligan on 23/11/2016 19:55:48

https://worldwide.espacenet.com/publicationDetails/originalDocument?CC=GB&NR=599684A&KC=A&FT=D&ND=3&date=19480318&DB=EPODOC&locale=en_EP

https://worldwide.espacenet.com/publicationDetails/originalDocument?CC=GB&NR=606330A&KC=A&FT=D&ND=3&date=19480811&DB=EPODOC&locale=en_EP

Edited By Michael Gilligan on 23/11/2016 20:12:38

Doesn't anyone read the original question ????

Bob asked about fitting liners into barrels not cast muffs round a liner which is what the Alfin process is.

On a 2 1/2" diameter liner I's go for 1 1/2 thou undersize on the bore, get the barrel sticking hot and just drop the liner into place.

.

John,

Bob ALSO asked this ^^^

MichaelG.

In which case I need to read the OP

Thanks for the responses. I forgot about Velocette casting the barrel around the liner so lets rule out that method.

John suggests a set size undersize on the barrel bore which is probably the way I will go but I will measure both the liner and barrels at normal temperatures and at working temperatures so that I have about 1 thou interference at about 80 degrees selsius.

The fit is important so the liner does not come loose when hot, not enough interference and the aluminium will expand more than the cast iron and come loose when hot. The liner is worth chilling as well as heating the barrel to maximise the expansion difference, As John says the liner should drop in if the dimensions are correct. You need to work quickly and with a press available as if it sticks you will be stuffed without one. The Trident liners were fitted to have the top of the liner just proud of the barrel so the gasket was tightest round the cylinder. I believe the liners were machined out if replacement was required. If a freezer is the only chilling available it is not going to shrink much as you will only be about 35 deg C below ambient which is probably a fraction of a thou but might help. A bucket of dry ice might have a bigger effect if you have some handy.

Mike

LA Sleeve seems to recommend more like .004" interference fit and heat the barrel to 450F (230C) before fitting, for aluminium.

Their instructions are here: **LINK**

More of their info here **LINK**

If you are doing a Velo, you should be able to find out from one of the specialist shops in the UK what fit they use.

Be sure to use liners with a step on the top for positive location. Saw a BMW come into my mate's shop recently that had liners installed with no locating step. Don't half make a loud clattering noise when they come loose and get pulled down by the piston only to be clattered by the crankshaft next time round.

Hi Hopper, thanks for the information. Seems like .004 interference would be about right for the size of engine I am machining. One set of barrels I have has already had liners pushed in but they appear to have caught in the barrel casting as they were pushed in because one liner is slightly oval by a couple of thou and there was also a tell tale curl of alloy in the recess at the top of the spigot in the liner /barrel as though it had acted like a cutting tool when pressed in. The other set I have looks to be only part machined and the liners appear to fit from the top of the barrel and have a lip on the top which should aid location.

The engine by the way is a BSA fury engine.

Don't think you need to go to the extreme that we used on aero engine cylinder heads shrunk and screwed on their barrels, the barrel is placed in liquid nitrogen, and the alloy head in boiling water, the two are bought together and quickly screwed together.

I would give it at least .001 per inch, possibly up to the .004 that Hopper says, heat the barrel in boiling water, and cool the liner in the freezer. If you don't have a press to help you, have a long bolt with a plate at each end, clamp the head of the bolt in the vice, and have either a ring spanner, or socket so you can wind it down quickly.

Ian S C

Doh, Bob I should have recognized your name from your previous posts and twigged Fury.

I think that jamming problems like your existing barrels have is why LA Sleeve talks about 230C for temp to heat the barrel to. And freezing the liner i s a good idea too as Ian SC says. A wet sponge jammed down the hole in the sleeve helps keep it cool on the way in too. And speed is of the essence so movement is completed before the liner can heat up and barrel cool down.

And of course a good chamfer on the leading edge of the sleeve so it does not catch as your existing one has.

You might want to communicate with LA Sleeve and tell them the size of bores and distances apart you have and see what interference they would recommend.

And make sure that you start square and arange some way of keeping things square as they are pressed together.

Ian S C

Bob,

You will presumably be aware of this article: **LINK**

http://www.motorcycleclassics.com/classic-british-motorcycles/bsa-fury-triumph-bandit-zm0z13ndzbea?pageid=1#PageContent1

But I just thought it worth briefly referencing Philip Vincent [from p4]

Similarly, he liked the cast-in iron cylinder liners that sealed to the cylinder head with waisted steel rings, eliminating a head gasket.

.

You have a great project there ...

MichaelG.

Once again thanks for the responses to my question. I know I am the custodian of a very rare engine and have to be sure to get things right.

I hadn't read the article and was surprised by Phil Vincents remarks about using cast in liners. There is certainly no sign of them on both sets of barrels I have.