Eccentric Control Rod Continued.

Earlier I showed the making of the eccentric strap, the eccentric sheave and the control rod for the valve control eccentric.  However I had to pack up my workshop and store my equipment etc in a container supplied by the builder who had to resurface the unsatisfactory floor following the fire I suffered in 2010.

I have made a little progress on the engine but not as much as I would like, but I have finished the valve control mechanism.  Here is a little article showing the finished piece.

Connecting rod made from 'scrap' material as described in earlier posting

This component was made from 'scrap' 2mm thick sheet steel.  I try to reuse so called scrap wherever possible, not because of cost necessarily but for a variety of reasons including convenience - I may have a suitable bit handy - or for environmental reasons - less waste.

Clevis

This was simply made by cutting and filing from a short piece of solid bar. It has to be finally finished to size and some final polishing.

Eccentric strap showing construction

complete valve control rod assembly with eccentric sheave

Rotary Table Indexer - Overview - 1

Some more pictures and description of functions.

All images are clickable to enlarge

The indexer has various functions:

1. Jog;
2. Division;
3. Degree;
4. continuous;
5. Program; and
6. Setup.

Jog:

The Jog command allows the table to be moved by a fixed angle according in either direction i.e. clockwise (CW) or counterclockwise (CCW) depending on which of 8 function buttons are pressed. 

Division:

The Division command will step the table a step at a time when the command button is set.  Awkward divisions are easy, simply type in the number of required steps and use the command button to step the table as required.  Difficult divisions such as 127 are no problem.

Degree:

This command is self explanatory, simply type in the number of degrees required and the command button will step the angle one at a time.  E.g. 60o degrees for a hexagon.

Continuous:

Again self explanatory - one commenced the rotary table will turn continuously at a predetermined speed.

This function could also be used to operate an X or Y table.

Program

Up to 10 user defined programs can be stored.

Setup:

This allows user parameters to be set up such as worm - wheel ratios, trigger settings to allow for different Stepping motor controllers, plus many others outlined in the documentation available on the forum.

The cost of building is relatively low, mine cost probably less than £20.00 to build but I did search around for inexpensive sources of components.  The most costly items were the PIC chip on which I embedded the supplied firmware, the display, and the case.  The latter was an inexpensive buy from Maplin though.  The keypad was built up from a simple circuit board and PCB buttons for about £2.00.

Cost could be reduced with a home made case.  For the practical ones amongst us, I made another case from some surplus oak planking, a bit of 3mm ply for the back and some coated steel sheet from a defunct desktop computer case for the front.

Stepper Motor and Controller.

Disassembled Device to Show Controller and Motor and home made keypad

The controller was an inexpensive Chinese one from an eBay source and has proved to be quite satisfactory so far.

The stepping motor was again a buy from an eBay source and is a 200 step, 439 oz in motor, which is more than powerful enough to run my small rotary table.

At the moment I am using a 12V power supply salvaged from an old laptop computer, I will probably upgrade this to a more powerful PSU at a later date.

Sourcing components carefully can find some good equipment at decent prices, I use eBay etc where possible and avoid the extra expense of using dedicated suppliers but it needs a knowledge of what you need for the job in hand.  It is well worth carrying out some of research before buying.

Rotary Table Indexer - Overview

Description of Indexer

I have been working on a rotary table indexer to use on my milling machine.  The indexer is one designed by 'Kwackers' aka Steve on the CNC zone forum.  Several members of the forum offered suggestions for variations and I have incorporated some of these in my own indexer.

The Assembled Indexer

Basically it is an electronic device with a pre programmed chip which operates a stepping motor which in turn is connected to the rotary table in place of the handwheel.

I have built the circuit, programmed the PIC chip with the firmware (program to drive the stepper), purchased an inexpensive Chinese stepping motor drive unit and a suitable motor.  All I need to do now is to connect the motor to the rotary table.  However the table needs a bit of simple modification to ensure accuracy but that should not be too expensive.  It will also require a mounting adapter making as well as some kind of connector between the motor shaft and drive shaft of the table (Oldham Coupling or similar to allow for slight misalignment).

Inside the Box

I have taken quite a few pictures of the process so I will write a few posts on the making of the device in sections so that anyone could follow the process.  Where possible I have used simple processes and techniques in order to make the making of the unit accessible to most.

As well as driving a rotary table it could also be used for other purposes such as controlling the table of the milling machine or operating other devices.  I have thought of using it to drive an equatorial mount for a telescope and there must be many other uses for such a device, especially if you are able to program the PIC for your own purposes and there must be suitable open source programs available.