RF30 Traverse Power feed - Part 1 - April 2006

The problem

In a couple of previous projects, I had put together a make shift power feed for the X axis of my RF30 Mill/drill. The results from using the power feed were just great and I was so impressed that I thought I had better turn this make shift prototype into a proper inclusion to my RF30.
Here,the first photo shows the temporary setup I had using a windscreen wiper motor for the power feed. This was used while milling the dovetails on the compound slide project. To couple the windscreen motor, I made a quick motor adapter which coupled the motor to the end of the Mill/drill traverse shaft. The motor adapter was clamped onto the shaft with a screw, the problem was that this screw had to be loosened to release the motor before the traverse could be used manually which was a pain. So I thought that when I make theis a proper fixture, it has to have a clutch arrangement.

This project had been brewing in the think tank for about three years and has finally come to fruition. During the many hours of thinking about what motor to use and what form of transmission I was going to use, many different combinations were thought of. In all these thoughts, I kept in mind a list of "like to haves" for the project and by the time I got around to building this project, this list of "like to haves" or features that I was trying to achieve was getting bigger.

Here is my list of "nice to haves":

Simple construction

clutch feature

able to use low and high speed or variable speed control

Not too much complex machining

Minimal modification to the mill/drill.

I had many Ideas on how to achieve a powered feed and I thought of many combinations of motros gears, belts direct drive couplings. Here is a breif table on some of the ideas I had on the situation.

Motor type	Low speed	High speed	comments
Stepper motor	Yes	with big motor	could get expensive
Battery drill motor gear box combo	Yes	Yes	would need a reduction drive to get torque
Windscreen motor	Yes	Yes	cheap, easy to get, plenty of torque but you need a clutch
Small gear box and motor	Yes	Yes	added complexity to couple gear box and motor together as well as the gearbox to the traverse

Transmission type	Cost	Ease of installation	Comments
Timing belt	moderate	Yes	bored to shaft size
Bicycle chain	Low	Sprockets need to be modified to fit shafts	need to find some old bicycles
Two gears	Yes	Yes	These can be meshed and un meshed to act as a clutch
Small V belt	Low	Yes	Easy to make but the belt may slip as high torque is required

The solution

The solution I finally came up with, was to use a windscreen wiper motor which would directly coupled to the Traverse shaft. The motor would have an adapter attached to the back face of the main windscreen wiper gear. The shaft retainer would be removed allowing the shaft to float. The floating shaft would allow the gears(worm and main gear) to mesh when the power feed is required and allow the gears to be disengaged when the powere feed is not needed. In this case the wiper motor shaft would be coupled to the table traverse shaft and the windscreen wiper motor would slide on the shaft. I used a Toyota, 12volt wiper motor and I powered it using a computer power supply. The PC power supply was good for experimenting as either the 12volt or 5volt supply can be used depending on the speed needed. I ended fitting a variable speed control and using the 12 volts part of the power supply.
This second photo, shows the windscreen wiper motor being held into the proposed driving position.Note that the normal drive end of the motor is pointing away from the mill/drill table. With the motor in the position shown in the photo, the motor is below the shaft and will be out of the way by not protruding pass the top of the mill/drill table.

The adapter

The first part to be made, was the adapter which fits between the windscreen wiper motors main gear and the dog arrangement(can be seen in previous photo) on the traverse shaft. To keep things compact, I made this adapter just long enough to cover the protruding shaft (after the handle was removed) and the boss on the windscreen wiper motor gear. In my case, I made this length 46mm.
Refering to the next photo, the smaller diameter of the adapter was made the same diameter as the hand wheel diameter so that it fitted onto the dog with similar appearance to the handle. The next step up in diameter on the adapter was made a little larger than the step in the gear which it was to mate up to. This bit was made large enough to cover the face of the gear but clearing to the teeth of the main gear. The largest diameter in the photo was just the size of the piece of material I had.

Shown in this next photo is the end of the adapter that mates up to the back of the gear. The photo shows a couple of steps on the end face of the adapter to for a raised section. This raised section fits between the center boss(the star looking parts of the gear) and the outer ring of the gear. The gear can be seen as having a little raised nib. I drilled the adapter so that the nib located into the adapter.

Next was the machining of the dog end of the adapter. This end mates up to the dog around the RF30 shaft. The dog consists of three raised sections and three lower sections. I chose to cut the dogs on the RF30 with the use of the rotary table even though it could have been done a number of different ways. Three milling cuts were all that was needed for this and the key to cutting this dog, was to align the left hand edge of the 10mm slot drill with the centre of the adapter. To do this I cut a slot at full depth from one side of the adapter to the other. Once that was done, the adapter was rotated 120 degrees to do the second slot and then the same for the last slot.

Once the dog arrangement was milled intot the adapter, It was screwed to the plastic gear with 6, 3mm screws. I kept them small so that I would be removing less material from the gear and weakening it less. These screws can be seen in the last photo on this page(item 6).

The next photo shows the adapter sitting in its proposed position with the table all the way over to one side. I figured that this will be a good position as the motor does not protrude above table height and due to the angle the motor is in, the table can move all the way to the end of its travel.

The slide arrangement

The next part of this project was to provide a means to guide the windscreen wiper motor back and forth along the shaft. This arranngement not only had to handle the torque of the motor, had to slide freely but also needed to kept simple. I opted for a couple of slides comprising of a tube and a shaft which slid into the tube.Here in this next photo are the two slide tubes mounted onto the machined bearing block(part that holds the end of the traverse screw). The left hand tube has a small peice of round metal with a point on it. I used this in both tubes to spot the center mark on the aluminium motor mounting plate. In this photo, the bearing block has been skimmed on the lathe. I did this as I found that the surface was quite uneven and would not allow the slide tubes to sit perpendicular to the face of the bearing block.

In this next photo the motor mounting plate has been spotted and drill to line up with the slide tubes. The two socket cap screws are screwed through the plate and the slides. These are small lengths of round steel which slide into the slide tubes(previous photo).

The spacer

As the whole concept of this project relies on the windscreen wiper motor sliding along the shaft allowing the main gear to disengage with the worm. When the main gear disengages, it protrudes past the gear housing and so a spacer plate has been made to fit between the main bracket(item 3 )in the parts photo below. The main motor bracket has a clearance hole for the adapater and not the gear. This was done to reduce the ammount of dirt that can get into the worm and main gear housing. This next photo shows the spacer plate sitting on the motor. The photo shows the hole in spacer clearing the main gear of the wiper motor. Note that the main gear does not protrude past the spacer.

I have put together this diagram to ilustrate the way the various parts fit. This is an elevation of the steup as viewed from the front of the machine.

Here are the various parts that make up the mechanics of the power feed( with the exception of the engage handle). I have made a list of items that match up between this photo and the diagram.

not shown in diagram = 1 & 2

motor mount = 3

Motor = 4

Motor spacer = 5

WSW shaft = 6

Open the next Power Feed page - Part 2 page.(opens a new window)