Britannia 70047 "Derek Stokes"

[JonL]

Thanks everyone,this forum and its members are a real solid gold resource. I would be tearing what's left of my hair out otherwise!

[Jim]

I fitted bronze sleeves to both the bronze cylinders for the Britannia. I did that to sort out the inlet ports which as part of the casting were very ragged and uneven.

Before

and after

I also sleeved the piston valve cylinders to ensure nice accurate ports.

Jim

[Roger]

It seems to me that the quality of castings we're being offered is pretty dire. I wonder how much it would cost to get them CNC machined from solid compared to buying these? You would be guaranteed that there would be no nasty surprises when you machine them and they would be a lot more accurate.

[JonL]

I've decided to go ahead with the liner idea, I think I'll try making it an interference fit in the bore and warm the casting/chill the liner on installation. I'm assuming I'll still need to move the PCD of the end plate studs out to suit, which does mean it will be quite close to the edges of the casting. My plan is to make a dummy end plate from steel with the correct mounting holes marked (I don't think they are evenly spaced, I've heard rumours that one of the studs can interfere with a steam gallery if evenly spaced) and mark up the cylinders from that. Problem if I only have 0.18 of an inch cast cylinder wall to fit the studs into....  If I tapped closer to the original PCD would I cause damage to the liner? I just don't know, I'll call it when I see it installed.

Thanks for all the advice people, feeling happier now.

[ettingtonliam]

Jan 21, 2019 10:08:31 GMT JonL said:

I've decided to go ahead with the liner idea, I think I'll try making it an interference fit in the bore and warm the casting/chill the liner on installation. I'm assuming I'll still need to move the PCD of the end plate studs out to suit, which does mean it will be quite close to the edges of the casting. My plan is to make a dummy end plate from steel with the correct mounting holes marked (I don't think they are evenly spaced, I've heard rumours that one of the studs can interfere with a steam gallery if evenly spaced) and mark up the cylinders from that. Problem if I only have 0.18 of an inch cast cylinder wall to fit the studs into....  If I tapped closer to the original PCD would I cause damage to the liner? I just don't know, I'll call it when I see it installed.

Thanks for all the advice people, feeling happier now.

You might be better off using a high temperature Locset to fix the liner. It isn't likley to move, after all, its fixed at the ends by the covers.
I know that in larger sizes, chilling the liner with liquid nitrogen enables it to be slipped in, but thats with larger masses of metal which change temperature more slowly. I think its asking a bit much of a thin wall PB liner, which doesn't have a lot of mechanical strength, to 'keep its cool' while you get it into place. A sliding fit plus Locset at least gives you time to manoeuvre it into place. IMHO.

[Roger]

Jan 21, 2019 14:07:55 GMT ettingtonliam said:

Jan 21, 2019 10:08:31 GMT JonL said:

I've decided to go ahead with the liner idea, I think I'll try making it an interference fit in the bore and warm the casting/chill the liner on installation. I'm assuming I'll still need to move the PCD of the end plate studs out to suit, which does mean it will be quite close to the edges of the casting. My plan is to make a dummy end plate from steel with the correct mounting holes marked (I don't think they are evenly spaced, I've heard rumours that one of the studs can interfere with a steam gallery if evenly spaced) and mark up the cylinders from that. Problem if I only have 0.18 of an inch cast cylinder wall to fit the studs into....  If I tapped closer to the original PCD would I cause damage to the liner? I just don't know, I'll call it when I see it installed.

Thanks for all the advice people, feeling happier now.

You might be better off using a high temperature Locset to fix the liner. It isn't likley to move, after all, its fixed at the ends by the covers.
I know that in larger sizes, chilling the liner with liquid nitrogen enables it to be slipped in, but thats with larger masses of metal which change temperature more slowly. I think its asking a bit much of a thin wall PB liner, which doesn't have a lot of mechanical strength, to 'keep its cool' while you get it into place. A sliding fit plus Locset at least gives you time to manoeuvre it into place. IMHO.

Just be aware that the time you get to move the sleeve is very much dependant on the thickness of the film. I originally tried using this method on one-piece piston liners and although I was quick, it got stuck in the wrong place before I could to anything about it and it had to be machined out and scrapped. If you have a sleeve that's long enough to slip straight through leaving a bit at each end, you will probably be ok, but forewarned is forearmed. 

[JonL]

For the valve sleeve LBSC suggests tinning the sleeve with solder before fitting if you have accidentally made it too small, that has potential. I wouldn't want to warp the sleeve with heat, although it is going into a concentric cylinder bore.

[ettingtonliam]

Thats interesting, Roger. which sets quicker, thin film or thick film? How much clearance did you give the liner/bore? About 2 microns, knowing you!

[Roger]

Jan 21, 2019 16:58:59 GMT JonL said:

For the valve sleeve LBSC suggests tinning the sleeve with solder before fitting if you have accidentally made it too small, that has potential. I wouldn't want to warp the sleeve with heat, although it is going into a concentric cylinder bore.

That's a very sound idea, so long as you're not going to use a high degree of superheating. Even so, you could probably just get away with higher temperature soft solder. I doubt very much if you'd distort the sleeve by heating it up to the melting point of solder.

[Roger]

Jan 21, 2019 17:00:16 GMT ettingtonliam said:

Thats interesting, Roger. which sets quicker, thin film or thick film? How much clearance did you give the liner/bore? About 2 microns, knowing you!

The thinner the film, the quicker it goes off. It was a very close fit, possibly 2-4microns. I should have realised and made a mechanical stop and push it through in one swift motion straight to the stop. You live and learn!

[mbrown]

Jan 21, 2019 16:58:59 GMT JonL said:

For the valve sleeve LBSC suggests tinning the sleeve with solder before fitting if you have accidentally made it too small, that has potential. I wouldn't want to warp the sleeve with heat, although it is going into a concentric cylinder bore.

I thought your cylinders were cast iron... will tanning "take" sufficiently?

Malcolm

[JonL]

Jan 21, 2019 18:34:10 GMT mbrown said:

Jan 21, 2019 16:58:59 GMT JonL said:

For the valve sleeve LBSC suggests tinning the sleeve with solder before fitting if you have accidentally made it too small, that has potential. I wouldn't want to warp the sleeve with heat, although it is going into a concentric cylinder bore.

I thought your cylinders were cast iron... will tanning "take" sufficiently?

Malcolm

I don't know, I suspect it wouldn't need to be a complete tinning to make it rigid enough; all I want is for it to not spin, it will be restrained by the end caps.

[ettingtonliam]

You can tin cast iron, but I'd still recommend the Locset approach.

[JonL]

Fair enough, thanks. At least it doesn't need to be aligned or anything. I think I'l make it over length and then just shave it down when installed, then I won't have to do any aligning at all.

Could you advise me which specific product you mean when you say Locset? I've used various loctites before but there are a bewildering array...

[terrier060]

I love your profile picture Nobby - I bought my wife a mincer for Christmas and we had a go at making sausages. There is quite a knack to it especially when the sausage skins are real pigs intestine - very hard to find the open end and very slippery! Sausages tasted good though. Sorry about the trouble with your cylinders. I would favour gluing to soldering, but what Roger says is so true. Better to have then a good sliding fit rather than too tight and you can twist them as you push then through to get good contact with the adhesive. Like Roger suggests I would make the liner plenty long enough and face off after the glue has dried. The Tech guy at Permabond is worth ringing. He is really helpful and has suggested a couple of adhesives to use on my Terrier cab.
Ed

[JonL]

I'll give him a ring in the morning, I can even pretend its work related!

I've changed a bit since that profile picture was taken, my beard is much more restrained. I still like sausages.

[mr swarf]

I'd also go with an adhesive rather than tinning on cast iron. It can be done but its not easy, I think lbsc was referring to bronze cylinders.
Retaining Compound is the type of adhesive you are looking for.
As Roger says, the smaller the gap the quicker it sets. Which ever brand you go for you should be able to get a data sheet giving graphs of cure time v gap & temperature etc.
Paul

[JonL]

I've just remembered I've got some Loctite 603 on the shelf, that should be ideal I would imagine. I'll check the spec.

[Roger]

Jan 22, 2019 8:19:48 GMT JonL said:

I've just remembered I've got some Loctite 603 on the shelf, that should be ideal I would imagine. I'll check the spec.

Do check the temperature range of that, there are specific Loctite products intended for high temperatures.

[JonL]

150 degrees C. Could be a bit borderline?