Thread: Table traverse for Chinese mill.

Thats a nice setup and well thought out, makes my effort look pathetic . I plan to redesignmine and hopefully it will be as good as your work Mike

Hi Guys,

First thank you for the kind words.

Now having run this table traverse a little, taken it apart and discovered that I can't get the small gear off the end of the motor shaft without damaging the worm wheel inside. It occurs to me that the motor and its worm driving its own worm wheel should be more than capable of driving the mill table screw directly and would be more controllable with respect to its speed.

I will be paying a visit to the local scrap yard on Monday to see if I can find another wiper motor. Stand by for a MK2...

Watch this space.

Hi Guys,

I managed to get down to the scrap yard this morning and found another wiper motor. This one is a British made one by "Trico". I think the car was a "Vauxhall". It had been in a smash and the front end was badly crushed but the wiper motor is OK. This one is the opposite hand to the first one that I got and is only single speed. I hope that when its mounted the motor body doesn't stick out above the table surface. I've not had chance to test it yet but I am assuming that it will be similar in speed and power to the other one.

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On this one you can see the adjusting screw for the end float setting. On this one the gearbox cover is riveted in place as was the other one. After testing I will drill out the rivets and clean the worm and wheel, remove all the switches from inside and get rid of the big connector. The motor mounting plate on this car is welded to the bodywork so I will need to make a suitable one for it. Fortunately the hole centres are exactly the same as the other one.

Hi Guys,

Well I had chance to play around with my new wiper motor. I had thought that it was only single speed... I was wrong ! Unlike the original motor which is completely insulated, there is no electrical connections to the case, this one uses the case as the ground side of the electrical system and gives two speeds depending upon which of the two wires you pick. Actually you can get three speeds by connecting the supply voltage across both wires. However doing that, not only does the motor run really fast, it get really hot very quickly as well. So that is a no no.

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Sorry for the camera shake. I wrote the data on a label stuck to the motor body. Yellow to positive is the fast speed and white to positive is the low speed and the case is negative.

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I stripped the motor gearbox down by drilling out the five rivets and removing the two wires from the connector block. The second and third photographs are the underside of the plate removed and the worm wheel inside. The springy fingers bear and run on the shiny disc hidden under all that grease. I removed the connector block, spring fingers and cleaned all the grease from the wormwheel.

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I took photographs of the ends of the worm so that the method of end float adjustment could be seen. The gearbox has a screw at the end of the worm. Inside this screw is a small steel ball bearing. When the motor is running in the correct direction the thrust is directed onto this ball. The other end of the worm just has a washer that rubs against the phosphor bronze sleeve bearing. The adjustment screw is set so that there is minimum end float without binding.

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I drilled and threaded the holes M4 and used hex cap screws to secure the gearbox cover. Which also acts as the thrust bearing for the wormwheel and output shaft.

Hi Guys,

I got around to making some more progress with MK2.
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This is the gear that I've chosen to put onto the wiper motor shaft. Like the other one the motor has a M8 threaded spindle and a similar tapered spline section. I've drilled out the bore so that it will go over the threaded part and cut a tapered section into the bore.

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This picture shows the contrast between the gear sizes that will be used. As near as I can guess the ratio between the black gear and the white gear with the brass hub is 1.4:1 and the ratio between the other white one and the black gear is 1.2:1. I think that this will give me an overall ratio close to 2.5:1. Which is a lot better than the 7:1 that I get on the other drive.

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Its not easy to see from the photographs but the motor output shaft is quite a bit shorter than the other motor by about 20 mm.
There isn't enough room to get the motor mounted a little further back. It might be that the motor body just fouls the mill table spindle end. The gear isn't pressed fully onto the output shaft splines yet, its about 3 mm to go. By the way the white plug in the motor gearbox housing is a breather. Its there so the heat doesn't build up any pressure and force grease into the motor body.

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I needed something to mount the motor onto so a quick rummage in the scrapbox produced this piece of 3 mm hard aluminium plate. Its been anodised with a fairly coarse surface but its suitable for what I want. So I marked it out for a central hole and three 6 mm clearance holes.

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I didn't have a drill or a hole cutter of 35 mm diameter, and I was too lazy to get out and set up the boring head ! So I resorted to a trick that I've used several times before in both aluminium and mild steel. A high speed carbide router bit. Drilling a 12 mm pilot hole to get past the bit on the end that is supposed to have a ball race on it. I used a drop of neat cutting oil as lubrication, ran the bit at about 350 rpm. Feeding it as though as though it were a drill, it soon munched its way through the plate.
I used a small 90 degree router bit to make the countersinks for the M6 allen socket countersunk screws.

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This is the result. It can be seen from the last three pictures, just how close the gear is going to be to the motor mounting plate. The gear isn't even tightened fully down yet. I deliberately made the hole in the plate big enough to clear the gear just in case I need to modify the mountings at a later date.

That's all for now:

Hi Dean,

Sorry I'm a couple of days late.

Happy Birthday.

Originally Posted by BaronJ

Hi Dean,

Sorry I'm a couple of days late.

Happy Birthday.

Thanks Baron. Keep up your good work. I can't wait to start mine, but there are other things that have more priority.

Dean

Hi Guys,

First an apology ! It wasn't until I looked back at the posts in this thread discussing a MK2 version of the mill table traverse drive, that I realised that I had completely missed out describing the new tumbler gear set. So I intend to rectify that omission right now.

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I started with looking for something suitable to act as a carrier for the new gears that I had chosen from the salvaged laser printer gearbox. I had an offcut of a quite hard polythene materiel 12 mm thick, so I cut it down to a nominal 60 mm X 90 mm. Cleaned up the edges with a fly cutter and got it squared up. I then found the centre and marked it up for drilling. Since the mill table spindle is 10 mm in diameter it was convenient to drill a 10 mm hole and use the original dummy spindle that I made when setting up the first drive unit.

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Since I had two of these identical gears I decided to use them. I cut the long bit of the spindle off them so that it wouldn't matter which way up they went when putting them onto the supporting shafts.

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The large white gear has had its centre machined out and a brass bush made to support it in the same fashion as the original large gear intended to fit on the mill table shaft. At this point the brass bush has not been set up for drilling and threading the fastening holes. I wanted to make sure that I could set up the thee gears in the right places.

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These pictures show how I put the table spindle gear on the dummy shaft and set the two black gears to mesh properly with each other. I used a transfer punch to mark the plastic where I wanted the support shafts for the black gears to go and drilled 6 mm right through. The support shafts are a simple press fit.

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The shafts for the two gears were 6 mm diameter silver steel parted off to length and 1 mm wide X 1.5 mm deep grooves cut for snap rings to secure the gears.

I'll continue in another post because there are a lot of pictures here and a few more to come.

The picture below is supposed to be up with the others...

Hi Guys,
Continuing from last nights post !

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This is the gear and the brass bushing that I turned from a short piece of 30 mm hex bar. The whole thing was done by mounting the mandrel, seen in earlier pictures, in the three jaw chuck mounted on the rotary table. I first drilled the holes 2.5 mm, the tapping size for M3. I used a dowel pin to locate the parts whilst drilling the other five holes after drilling the first hole. Then I split the assembly and drilled the holes in the ring to clear M3. I then threaded the holes M3 using the chuck placed on the tapping stand, locating the holes by hand.

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The M3 screws are standard computer screws used for fixing floppy drives into the case. I don't really like them because the little flange on the head extends over the edge of the securing ring. I had considered turning them down but I've found some countersink ones that I intend to replace them with.

The last picture shows the two 6 mm diameter steel shafts for the two black gears with the snap rings fitted. They are just a good push fit into the plastic and can be pressed in with hand pressure.

I've not done anything on the table drive today because I've been playing around with a design for a variable speed controller. At the moment I'm using my 30 volt, 3 amp variable voltage power supply. But I picked up a 25 volt 4 amp transformer at the scrap yard that should be suitable for powering this and a couple of other devices attached to the mill.

More to come: Thanks all.

Hi Guys,

I've made some more progress on the MK2 Mill table traverse drive.
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The pictures above show the 3 mm aluminium plate that I used to make the mounting that supports all the gears, the motor and other bits. I used 2 BA cheese head bolts and turned the underside of the heads to make them into countersunk ones. The large hole in the plate was trepanned in the mill. Its 32 mm diameter.

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The gear that fits on the mill table spindle as you can see is somewhat short ! So I'm going to have to make a short spacer to take up the space between the bush and the securing nut. I've fitted the mounting plate onto the end of the mill table so that I can get an idea of what spacers I need to make for standing off the motor.

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Because I couldn't see to measure the gear spacing for the tumbler gears I made some little bits that could be clamped once I got the spacing clearance right and drilled and threaded for M3 screws. Then I drilled the third hole, the one at the top left for the other mounting bolt. You can see how little clearance there is because of the much shorter wiper motor output shaft.

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The last pictures show the general arrangement of the unit as it will be when finished. The tumbler gears and the support have yet to be done.

More later.
Thanks Guys.

Hi Guys,

I did some more work this morning on the tumbler gear support. Mainly boring a large hole in the thick plastic piece and making a spacer out of the off cut from trepanning the hole.

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These four pictures show the trepanning of the hole in the plastic block holding the tumbler gears. Note the plug of plastic remaining in the hole with the boring bar cutting a broad groove around it. The third picture shows finishing the hole to size.
Its 32 mm in diameter. The plastic comes off in thin stringy threads, whilst the swarf from trepanning was a thin continuous tape.
I had removed it before I took the picture.

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This is the plastic block and the plug that came out of the hole when the cutter bit passed through.

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Having cut the hole I now tried it on the mill table end to see if it fit properly and I had enough clearance for the driving gear on the end of the mill table shaft. As can be seen it fits beautifully and the gears are perfectly in line.

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Remember that plug of plastic that came out of the hole ! Well the brass bush holding the table gear was a little short. 1st picture. So I had need of a suitable spacer to take up the distance between it and the retaining nut. Two minutes in the lathe and I had my spacer. I wish everything was so easy.

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I put it all loosely together to see how it fitted. One of the things that bothered me was the clearance of the tumbler gears in the neutral position. There is just a millimetre of clearance between the gears and very little movement needed to engage them in either direction. Otherwise they line up perfectly. So I now have to make the spacers so that it can all be secured and tested. I did find that the bottom left hand bolt doesn't have enough room to put a spacer over it without fouling the lower tumbler gear when the top one is engaged with the driving gear. I haven't decided yet whether to move the bolt or to make a fixed spacer mounted a short distance away. I'm tempted to use three identical spacers but to put a wide flat down the length of one of them.
It would give the clearance but would mean that the spacers would not be interchangeable with each other.

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Last but not least. I should have put these two pictures in earlier but forgot.
This is how I made the countersunk 2 BA screws used to support the motor on the mounting plate.

Thanks Guys. Your support is appreciated.
More to come. I've the speed controller design to finish yet.

Looking good Baron. Have you considered a ball detent to hold things in neutral?

Michael

Originally Posted by Michael G

Looking good Baron. Have you considered a ball detent to hold things in neutral?

Michael

Hello Michael,
Thankyou for the suggestion.

I used a spring loaded detent on the MK1 version. It worked quite well on there.

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I used a short length of M8 threaded rod and a long round head rivet with a coil spring under the rivet head. This dropped into a dimple drilled into the tumbler support hub.

Having tested the MK2, it's going to need something a little more substantial ! Because the gears are bigger there is far more torque pushing the gears out of mesh. I was considering something like a dog and peg arrangement. I've not worked it out yet. Rest assured though, that I will take photographs and publish them for all to see.

Hi Guys,

I've made a start on the detent mechanism for the tumbler gears. When I set the unit up and ran some tests, I found that the tumbler gears pushed out of mesh with far more force than occurred with the MK1. On that unit because the gears were quite small the loading was much lower and a simple ball and spring held the tumbler steady. Not only is the gear loading much higher on this version but the speed of traverse is a little over 2.5 times as fast. At 12.5 volts I get 100 mm per minute. So I think that this will provide a better range of speeds.

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The three pictures above show the tumbler in both drive positions. The control arm is a short length of 6 mm diameter free machining steel rod. Its turned down at one end for 9 mm and threaded M4. This is screwed into a piece of aluminium bar 8 mm square by 20 mm long. This bar is set into the plastic just under the two gears. I set the plastic block up in the mill and machined a slot with a 7 mm slot drill in the end being careful to get it square so that the control rod was vertical when the tumbler was in neutral. I then substituted the slot drill for the control rod with the bit of square bar screwed on the end, getting it in line with the machined slot. I then heated the aluminium bar with a hot air gun until it was hot enough to melt the plastic. When it was I used the quill feed to press it into the slot in the plastic and hold it there whilst I let it cool down. The result is a plastic to metal bond that is strong enough to support the control rod securely.

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Since there is nothing to support the plastic tumbler block I made a shouldered bolt from a bit of silver steel bar to hold it down whilst letting it move. At the control rod end I made a bridge with a slot in it to serve the dual purpose of holding the plastic block and providing something that I could use to make a dog clutch that would stop the tumbler gears getting pushed out of mesh whilst in use.

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These photographs of the mounting plate with the tumbler block and gears, it shows the bridge piece with the control rod passing through it. Its made from a short length of 8 mm x 13 mm aluminium bar with a 6 mm slot machined in it. Its held with a pair of M4 countersunk screws from behind the plate. I'll take photographs of it when I start to cut the teeth into it for the dog clutch to fit.

More Later: