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I'm restoring an old fan that used a horseshoe-shaped steel pipe for the base, and the ends of this pipe are closed of with two caps.

The caps are made of a transparent plastic, their shape reminding of a "mushroom", like this piece:

enter image description here

This piece is hollow and inside there's another spherical cap made of polished chrome steel.
So when it's fitted in the pipe you can see a transparent spherical cap and inside it the chrome spherical cap.

The issue is that the plastic cap is broken and damaged.

From photo analysis I determined that the plastic cap can be cut from a 27 mm diameter sphere.

Now there's the issue: I don't know where to get a transparent, plastic hollow sphere 27 mm in diameter.

A hollow sphere 25.4 mm (1 inch) in diameter would also work, I'd only have to cut a spherical cap with a slightly larger solid angle. It wouldn't be identical, but close enough.

The issue is that I can't find anything or anyone that sells this.
I've only found some hollow transparent spheres used for Christmas decorations, but none 1 inch in diameter.

I'm trying to figure out how could I make one.

Do you have any idea?

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    Welcome to Arts & Crafts! If you have a picture of the damaged cap, adding that to the question would help a lot.
    – Elmy
    Jan 13, 2022 at 6:03
  • Hi, this type of question is actually off-topic here per our Help center: "Product and service recommendations ("Where can I get [product]?" or "Where can I find someone who does [service] in [area]?")". If you can edit your question to only ask how you could create one yourself, it would be completely fine. Thank you for your understanding, and welcome to Arts & Crafts!
    – Joachim
    Jan 13, 2022 at 7:13
  • @Joachim I don't agree with you. It's asking "How / where can I get an object that looks like this and has those properties for my craft project?" not "Where can I buy an [insert product name here]?".
    – Elmy
    Jan 13, 2022 at 7:59
  • @Elmy Yes, I realized, I'll edit it myself and open it again. I noticed directly afterwards, but had something more pressing going on. The "where" is still off-topic, though, and I think closing a question simply because it requires editing is a perfectly fine reason for closing it, right? (An honest question - not a criticism :) But, to be fair, this also makes your answer off-topic.
    – Joachim
    Jan 13, 2022 at 8:20
  • @Joachim I know that many sites close questions quickly for many reasons and editing can be one of them. Worldbuilding even has a sandbox for closed Qs. But I personally am not a big fan because it send a negative signal to the OP. Especially new contributors abandon their questions before they notice the reopening or any answer. As to my answer, I wouldn't have written it if I thought it was off-topic ;). But there are different opinions about links to web shops (in my main community Pets it might have been flagged as spam without the explicit disclaimer).
    – Elmy
    Jan 13, 2022 at 8:38

1 Answer 1

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I think you only lacked the right search term. I found this by searching for "transparent internal pvc ball cap":

enter image description here

It fits inside a PVC pipe, which has an inside diameter of 1-1/4". The only manufacturer I could find is Formufit. Here's their web shop (I am in no way affiliated with this manufacturer or shop).

This seems like it could be a standardized product, designed to fit standardized PVC pipes. So maybe you could find it in different web shops or in your local home construction store.

There are also dome lenses that might fit and if you're ok with the cap being metal instead of transparent plastic, you could have a look at hand rail end caps and find a lot of different designs and sizes.

If all else fails, consider 3D printing a cap with a resin printer using the smallest available layer thickness. The resolution of these printers is enough to create a transparent object with only a slightly matte surface.

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  • The original photo shows debossed lettering of 110 mm diameter, slightly larger than 4 inches. This makes your suggestion for 3D printing useful. Post processing of transparent resin printed items can approach substantial clarity.
    – fred_dot_u
    Jan 13, 2022 at 10:02
  • There are three problems however. The first is that I don't live in the USA and I haven't found any info about shipping to other countries. The second is that my pipe isn't 1-1/4 inch. And the third is that the solid angle of the spherical cap in this is much larger. From what I see this is virtually half a sphere, or 2π steradian. The solid angle of the spherical cap in my fan is about 1.28π steradian. Of course, I could buy one and cut a cap from it, but then again I'd need it to be a sphere of about 27 mm in diameter, and this one is pretty bigger. And I could find similar in my country Jan 14, 2022 at 0:17

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