Clear the Decks. Work in Progress!

A couple of hours finishing some commercial "stuff" and that's it for a while . . . now to concentrate on my own stuff for a while!!

The company I bought the rotary burr from were not very happy but agreed to supply me with a new one at no further cost.

When you buy upwards of $1000 a month from them it would be pretty silly to quibble over $40!

Then the sprockets turned up too.


















Other things to do first however.

I'm not sure if I mentioned it earlier but another reason I decided to go the (proper) chain, sprockets and shafts route was I realised I don't need to get too fancy with all the bearing mounts etc.
Originally I traumatised over how I was going to get the bearings in place as commercial bearings are quite large and the standard mounts for them are designed to go into regular convenient machines (which this is definitely not).
It occurred to me that only the drive sprockets need to be steel, and in all probability even they could be made in acetal.
However "made" is the operative word in this case.
Steel - off the shelf tomorrow at $6 each.
Acetal - Design, Order material, Machine for 2 days, so about $50 each.
That's what happens with small batches- too much overhead.
However lots of chains in commercial practice just run over idler pulleys for guidance and I could make these in about 5 mins. like so:

















And for these all I need is a bolt through the middle as the material is very "slippery" and makes a good bearing surface all by itself.
A simple plate can be welded in and a bolt put through it on which to mount the pulley.
Cheap, easy, fast and convenient.

Now I need to get the attachment of the chain to the bed frame modified from the original pulley idea.
The end of the bracket was cut off as it was now not needed.












A bolt was cross drilled, cut off and the end rounded so a standard chain link could be fitted through.




















Then a sleeve was tapped to fit the bolt and welded onto the end of the bracket.
The link can then be fitted to the chain and we are back in business.


















It all looks rather fragile but when I did the calculations it is about 10 times stronger than it needs to be.
For example : this rather small chain has a guaranteed minimum tensile strength of 7.9kN which means you can hang about 800kg from it!!
That's often a problem in engineering where you have to design for removing flex.
Things can be adequately strong in terms of breaking but they will still allow bending.
To get rid of the bending it has to be 10 times stronger - and that's what we are used to seeing - so when it is made strong enough to resist breaking and we don't have to worry about bending it looks too weak.

Unfortunately there are four of everything so tomorrow will be similar to today, but at least it looks like it will all work out OK this time.

I think I've said that before . . .

Just before I embarrassed myself . . .