1Q22 Challenge - Knob Twiddling

paulnb57

Thanks for sharing all your progress, really interesting seeing it develop

TTony

WezV said:

TTony said:

How did you hold them steady when drilling out the centre?

I use a very simple jig with a few holes in it.

I thought the knob "blank" would just spin in the hole when you started drilling it.  Guess it's a tight enough fit that the friction stops it spinning?

WezV

These seem to be holding fine.  I'm pushing down on the jig to hold them in place and that seems to be enough.

WezV

i think the red dye i used was a bit too opaque.  the yellow and brown are translucent. 

the mixed pour has given me knobs' that are mostly red brown on top, mostly brown on bottom, not much patterning visible... and yes, more bubbles





Quite interesting as they are though.  They may lighten up and show more patterning once drilled

I'm now doing a trans yellow, brown mix.  Shouldn't matter if more yellow settles in the bottom of the mold as it will be more see through

also looking at inserts.  I have this style of push fit dome knob with a tube insert


I might try replicating that with a PVC pipe or similar. Something soft enough to go over a knurled haft, but hard enough to last

WezV

And one last experiment for the day.


I still had some silicone left and decided to make a couple of smaller molds.

On top we have 4 more gibson style knobs, this time I am casting the mold upside down so I can fill from the top, hopefully giving nice push fit knobs straight out the mold using a lot less resin.  Bubbles will definietly be an issue with this, but I think I'm getting those under control now.


I also found a solitary witch hat, so decided to take a mold of that too.

WezV

Second batch of tort went much better.   I think it will be more obvious when drilled out, especially on the gibson and fender  knobs.    These ones are a little dark, so maybe a drop less brown next time.

Dome knobs look great






I suspect I need to let it start to thicken a little more before mixing the colours  if I want a more defined blotchy pattern... but I'm quite happy with the smokey swirl for attempt two.

I have ordered a chopping board mold, which I can use to make some plate material.

Tele-scopic

This has been fascinating!  I love the documentation of the process and the tort effect.  Many, many years ago I made some chess pieces from latex moulds and this thread reminded me of them - as far as I remember it was epoxy resin with Kiwi boot polish!:

I never finished the set - and my daughter has recently kept on at me to finish them so I was inspired by your thread to investigate.  I was amazed to find that the moulds are still available.  Looks like epoxy resin is no longer a thing - but polyurethane casting resin is and it seems very easy to work with and doesn't seem to create many bubbles.  Have you tried using that?  There is a YouTube video with a bloke demonstrating how to use it and at the end he casts some mechanical knobs which are a similar size to yours.
https://www.youtube.com/watch?v=MKJaU2CDHfU
Apologies if you know all this already!

WezV

All advice is welcome.    I'm just figuring it out as I go 

LastMantra

Wow cool idea! 

WezV

here are the upside down Gibson and single witch hat molds .  i'm leaving the bit of flashing on top of the gibson mold as that will give a good guide for filling the mold and tidying up the top of the knob


I did occur to me that I could use the gibson mold to cast some push fit inserts for the other knobs, just using the middle bit of each mold

ThePrettyDamned

So cool! I can't wait to see how the witch hat looks in trans colours, or brighter colours. I really like the shape but it's only ever black or white with silver or gold.

LastMantra

WezV said:

So according to that it would be best to vibrate from inside the resin.

I can probably fashion a probe to go in the graver that will do the trick.     

I'm thinking of the kind of thing they use for concrete. 

Obviously on a slightly smaller scale 

idiotwind

In a lot of videos I've seen with epoxy they've given it a flash over with a blowtorch to clear bubbles.  Not sure if that depends on the type of epoxy or other factors like that.

WezV

idiotwind said:

In a lot of videos I've seen with epoxy they've given it a flash over with a blowtorch to clear bubbles.  Not sure if that depends on the type of epoxy or other factors like that.

yeah, it works great for surface bubbles, but not so well for deeper molds.  Should be enough when I do a flat plate

Seems to be best if you degas after mixing, before pouring, then again once in the mold 

ThePrettyDamned

Those dome ones already look really good to be honest. 

WezV

I'm calling them "cola bottle" and "lemonade", rather than Tortoiseshell or clear.  So the bubbles are obviously meant to be there

Andyjr1515

I'm loving this

The whole discovery process.  And many of these are starting to look mighty fine

Andyjr1515

Apropos probably nothing in particular, I started looking at how those folks do the dandelions in resin that all of us had as paperweights a few decades ago.

Clearly, the resin seems to be a particularly thin version because all the 'how to' videos miraculously are completely free of trapped air in the pouring!  But I started following a few rabbit holes and came across a number of references to a different - nay, opposite - approach.

It was to put the setting mould in a pressure cooker!  

The logic seemed to be that the vacuum and vibration methods work OK if the liquid is low enough viscosity for the air bubbles to expand and rise fully to the surface.  But if that isn't possible, then the opposite approach is to apply enough pressure for the trapped air to be compressed to the point it is too small to be seen.

All I can say is that tightening my belt after a vegetable curry and a few beers doesn't have the same effect, but interesting all the same...
  

WezV

Andyjr1515 said:

Apropos probably nothing in particular, I started looking at how those folks do the dandelions in resin that all of us had as paperweights a few decades ago.

Clearly, the resin seems to be a particularly thin version because all the 'how to' videos miraculously are completely free of trapped air in the pouring!  But I started following a few rabbit holes and came across a number of references to a different - nay, opposite - approach.

It was to put the setting mould in a pressure cooker!  

The logic seemed to be that the vacuum and vibration methods work OK if the liquid is low enough viscosity for the air bubbles to expand and rise fully to the surface.  But if that isn't possible, then the opposite approach is to apply enough pressure for the trapped air to be compressed to the point it is too small to be seen.

All I can say is that tightening my belt after a vegetable curry and a few beers doesn't have the same effect, but interesting all the same...
  

yeah,   apparently a vacuum work best when making the silicone molds, but pressure works best for the resin itself. 

for the molds, i've not had to do anything really.  I pour a thin coat over the item I am copying so it has a bubble free coating first, then gently fill the mold from a  corner.  There are some bubbles in the silicone, but none that affect the casting

I did look at pressure pots.  Maybe I should look into a cheap pressure cooker.

Andyjr1515 said:

I'm loving this

The whole discovery process.  And many of these are starting to look mighty fine

all my build thread could be described that way  

downbytheriver

I love those torty knobs - let me know when you reach production!