Looking for a 4cm wide 3.5cm tall truncated cone

[Kallisti]

Here is a challenge - I'm looking for a truncated cone structure that is 4 cm at the base and that is about 3.5cm tall at the truncated point and 2cm diameter at the top.

 

Material is not so important although I would need to be able to glue things to it and have a hole through the middle to accept a 5mm diam LED at the apex.

 

Anyone got any ideas?

 

Note: i don't have a lathe or access to one.

[Aeronut]

That's taken me straight back 47 years to my CSE Technical Drawing class at school.

[Gorby]

Takes me back to technical drawing as well.

You could do it from flat plastic, this site may help:

 

http://craig-russell.co.uk/demos/cone_calculator/

 

Hope that helps.

[Kallisti]

Oh now that is very interesting! Nice one @Gorby

 

I had thought about building it up with discs and sanding - I've got some 3mm thick plasticard but that would still be 11 discs I'd need to cut out and I'm not sure my circular cutter will handle that amount of cutting without attacking me with its sharp edge in some nefarious revenge  

 

However this option looks rather useful...

[Gorby]

My years doing technical drawing at school reminded me that there was a way to do it, but I couldn't remember the method. I've saved the link as well – it may come in useful.

 

Where was the internet when I was doing my homework?

[tank152]

When I was an apprentice this was our Bible;

https://www.amazon.co.uk/gp/aw/d/0582009618/ref=pd_aw_sbs_14_2?ie=UTF8&psc=1&refRID=F0Q9QNQPW4WGGNJ36YC3&dpPl=1&dpID=51P9145JTAL

I'm surprised to see its still available. When we have anything like development to it we get paper templates, one of the joys of StruCad or Tekla as it is nowadays. 

I've saved that link though to go with my Trig apps etc that get used for work.

Not wanting to state the obvious but plasticard wouldn't be any use, get a pair of dividers draw it out and roll it to shape, a sheet of brass would be ideal as it would hold its shape as you roll it.

[Kallisti]

Thats a thought, I'll have to check what I've got in the stash for sheet brass  - I know I've got some it just depends how thick it is.

 

That looks like a very interesting book - pity about the price!

 

Edit: bingo, go some 5 thou brass sheet from Albion Alloys that might to the trick, now I just can't find my protractor anywhere!!!

Edited July 26, 2017 by Kallisti

[tank152]

What that link doesn't tell you though is the actual length to cut the pattern, so make sure you make it long enough for the 2 ends to meet up, you can then cut your brass with a pair of study scissors.

Here's a demo about rolling a cone which may help you get some idea of the shape and how to roll it.

 

 

[Kallisti]

The length is determined by the arc angle, in my case 98.9 degrees

[tank152]

You beat me to it,  I was talking out of my bottom there!!

Just found this.

After watching that you even be able to use very thin plasticard after all, although brass sheet would be better as it would hold its shape on its own like the one in the first link.

[Gorby]

I suppose the material depends on how strong it needs to be. If it doesn't need to particularly strong, I think that Plasticard would would do the job – you could always put a 3cm diameter bulkhead half way down to strengthen it.

[Francis Macnaughton]

If you can get hold of some,  sheet lithoplate is very good for this sort of work as it is cheap if bought as scrap from a printers and can be cut and rolled easily.  I use it for making funnels on RC warsrhips for example.

[Kallisti]

Proper job!

 

 

This is a paper test of the technique and it seems to work for what I'm trying to do! Still waiting on the new plasticard supplies - think I'll stick with the plastic as I will need to glue some details on and that will be easier with plastic rather than brass.

 

Thanks for all your suggestions and help, it did the trick!

 

[tank152]

2 hours ago, Kallisti said:

Proper job!

 

 

This is a paper test of the technique and it seems to work for what I'm trying to do! Still waiting on the new plasticard supplies - think I'll stick with the plastic as I will need to glue some details on and that will be easier with plastic rather than brass.

 

Thanks for all your suggestions and help, it did the trick!

 

Nailed it! Now you know how to make masks for spinners etc. Just use masking tape and you're away.

[Kallisti]

I've got my own methods for making spinners that doesn't need masking tape usually

 

[tank152]

No, I meant masking spinners, for example if rings need to be sprayed on. Use masking tape to mask the spinner prior to painting. Think fighter group markings on P-51s think 357, 356FG.

[Kallisti]

gotcha