Can brass / bronze permanently shrink?

[Tim Good]

I’m rebuilding a Lofrans anchor windlass. The new brass part in the middle of the photo is meant to slide down into the lower older part with small tolerance of around .1mm.

However the inner diameter of the old section should be 100mm but instead it’s now 9.13. That’s a huge difference. As such the new brass unit just sits on the top of a lip.

It older based hasn’t distorted in shape but simply not big enough and more. I have had to heat it all to get it apart. Do you think it could have shrunk that much in the process?

 

[Sticky Fingers]

My guess is that you measured the old bit wrong. Or made the new bit wrong. Metal not gonna change randomly in service once it’s fabricated and cooled.

 

[Tim Good]

My guess is that you measured the old bit wrong. Or made the new bit wrong. Metal not gonna change randomly in service once it’s fabricated and cooled.

Well that’s exactly what I thought. I assumed they sent me the wrong part or it was for a different model. So I dug the old part out and they’re identical…. and tried the old one where it fit previously… and it won’t go in. But I assure you that this time last week it went in there and with enough clearance to rotate.

 

[Sticky Fingers]

Weird. How accurately can you measure the bits? Eg do you have a high quality digital vernier? An error of a few thou (or metric equivalent) can screw this kind of fit,

 

[Tim Good]

Weird. How accurately can you measure the bits? Eg do you have a high quality digital vernier? An error of a few thou (or metric equivalent) can screw this kind of fit,

Well the measurement is kind of irrelevant. What once fit now doesn’t. It’s not the end of the world as I can find someone who could machine off enough from the new part to slot in there. But still it’s really odd.

I’m wondering if I whacked it too hard trying I get it apart.

 

[Sticky Fingers]

Well the measurement is kind of irrelevant. What once fit now doesn’t. It’s not the end of the world as I can find someone who could machine off enough from the new part to slot in there. But still it’s really odd.

I’m wondering if I whacked it too hard trying I get it apart.

Ah, you hit it…! Well maybe that’s a clue.

 

[ducked]

Perhaps originally thermally fitted?

 

[Boater Sam]

You have spread the end of the boss, take a file to the burr on the inside.
Brass is soft, hitting it will move it about.

 

[Tim Good]

You have spread the end of the boss, take a file to the burr on the inside.
Brass is soft, hitting it will move it about.

Could be easier to reduce the diameter of the flange of the new piece I think. 1mm is huge

 

[Tim Good]

Ah, you hit it…! Well maybe that’s a clue.

I know. Feeling like an idiot. This job started as a simple inspection. Then new seal and bearings at around £100. Then a new alloy sleeve replacement. Not the motor has been confirmed as goosed since the windings have largely burned out. It’s all getting to the stage of 70% cost of a new windlass and that’s not factoring in all my time in rebuilding and research of old parts. Bloody boating.

 

[Neeves]

Windlass are marvels off, very simple, design and engineering. Considering the abuse they endure they are quite remarkably robust.

Sadly your experience is not unusual - though the problems, still self inflicted, are usually caused by corrosion.

I get involved with windlass servicing and I always attend with an angle grinder - as when a windlass gives up its commonly irretrievable, needs cut out and replaced.

You are amongst friends. Don't feel bad, your experience might be noted by a few here - and they will not make the same mistake

Jonathan