LBMiller5
01-02-2005, 04:02 PM
I have been taking my 4-day weekend off from work and spending the time building motors. I had taken apart a bunch of CD-ROM drives and scavanged a bunch of motors. I figured these would be good "Test Subjects" to learn with. Here is a shot of the collection:
http://innov8tivedesigns.com/rcgroups/Stators.jpg
I have been using the guide rails that support the laser assembly in the CD-ROM drives for motor shafts. They are exactly 3mm in diameter, and appear to be made from precision ground tool steel. The only way you can cut these shafts is with a cut-off wheel in a Dremel tool!
I chuck the shafts up in my mini-lathe, and use a 0.020" thick cut-off wheel to make a ring groove at one end to hold a C-clip. When I am done, the C-clip holds everything together.
While I was working yesterday, I was trying to come up with a good way of pressing the little 1" long shafts out of the CD-ROM rotor cans and press in the new shaft without damaging anything in the process. Well this is what I came up with. The test subject for this procedure is the double stack can at the bottom center of the photo above.
1. I put the stock can into the lathe with the top facing the chuck. I just barely tighten the 3-jaw chuck so it holds the shaft perfectly centered, but it can still slide if you push on it hard. This supports the shaft and distributes the pressure across the entire face of the can. Then I chuck up the new shaft in the drill bit holder so it bottoms out, and then I tighten it down in the chuck. Next I slide the bit holder ahead until it just touches the old shaft and lock it down. You can see this below.
http://innov8tivedesigns.com/rcgroups/ShaftPush1.jpg
Here is a close-up of where the 2 shafts meet.
http://innov8tivedesigns.com/rcgroups/ShaftCloseUp.jpg
Next I just turn the feed wheel on the bit holder and it presses the old shaft out as it presses the new shaft in. (Save the little shaft piece that gets pushed out, as this will be used later in the procedure.) Since this mini-Lathe only has about 20mm of travel on the feed wheel, I have to go the full travel, then wind the shaft back in, move the bit holder forward, lock it back down and go again. I have to repeat this process 3-4 times depending on how long the shaft is. I continue until I am about 1/2 inch from the final position I want. This photo shows the new shaft about 2/3 of the way into the can:
http://innov8tivedesigns.com/rcgroups/ShaftPush2.jpg
At this point I take the shaft out of the drill bit chuck and slide on the bearing assembly with the stator. Here I can check for interference between the back side of the rotor can or endbell and the stator windings. If there is any binding or rubbing, I can add front washers as need to get the proper clearance.
I discovered a great source for shaft spacer washers. I work in Electronics as an Enginner, so I have a bunch of old parts laying around. While I was going through one of my drawers, I came across some neat little washers. They are used on DB9 and DB25 connector shells under the screw heads. They are exactly 3mm ID and 5.5mm OD with a thickness of 0.75mm. They work great for spacing the front side of the endbell to get clearance for the windings. I also use them at the back end of the motor shaft under the C-clip. Here is a picture of the washers:
http://innov8tivedesigns.com/rcgroups/3mmWashers.jpg
Once I am happy with the clearances, I put the whole assembly back into the lathe chuck for the final push. I then take the little shaft that was pressed out, and chuck it up in the drill bit holder as shown below. This makes a nice tool to press the shaft in the rest of the way. I took the stator back out on this one before I put it back into the lathe so you could see what was going on better.
http://innov8tivedesigns.com/rcgroups/ShaftPush3.jpg
I have been using K&S aluminum tubing for my bearing tubes. They make a size that is 3/8" OD with a .049" wall thickness. The ID is just a little smaller than 7mm, so I have been using 3mm ID x 7mm OD x 3mm thick shaft bearings in my motor. The local hobby shop stocks them at a good price, and the bigger bearings last longer than the smaller ones and distribute the shaft loads better. I cut a piece of tubing a little over 1-1/2 inches long, and then clean up the ends on the lathe to make it exactly 1.500". Next I turn down one end to fit the ID of the stator. Finally I bore out each end to a 7mm ID that is 3mm deep to hold the bearings.
Here is a close-up of the final push. As you can see, I left just enough shaft sticking out to put on a spacer washer and the C-clip, and still have .005-.008" of end play on the shaft. The end play prevents the bearings from being side loaded too heavily.
http://innov8tivedesigns.com/rcgroups/ShaftCloseUp2.jpg
The back bearing takes all the thrust load in a standard tractor motor configuration. The spacer washer insures that the back bearing only makes contact on the inner race of the bearing to avoid friction and wear on the C-clip.
Now all that is left to do is add the washer and C-clip and you are done.
Well that is the process. The shaft went in perfectly straight, and the can has absolutely no wobble. I will reinforce the front end with a little 1/4" aluminum spacer and some JB-Weld.
So now all you guys out there who have a mini-lathe, or even a full size one for that matter, have a new way of pressing in your motor shafts. I am sure that this technique would also work well on the GBx series of parts. Depending on the type of chuck your lathe has, you may need to turn down a little spacer washer with a center hole to clear the bosses on the end of the GBx end bell. This would also help to keep from scratching the aluminum end bell as the shaft was pushed in.
Have fun building motors!
Lucien
http://innov8tivedesigns.com/rcgroups/Stators.jpg
I have been using the guide rails that support the laser assembly in the CD-ROM drives for motor shafts. They are exactly 3mm in diameter, and appear to be made from precision ground tool steel. The only way you can cut these shafts is with a cut-off wheel in a Dremel tool!
I chuck the shafts up in my mini-lathe, and use a 0.020" thick cut-off wheel to make a ring groove at one end to hold a C-clip. When I am done, the C-clip holds everything together.
While I was working yesterday, I was trying to come up with a good way of pressing the little 1" long shafts out of the CD-ROM rotor cans and press in the new shaft without damaging anything in the process. Well this is what I came up with. The test subject for this procedure is the double stack can at the bottom center of the photo above.
1. I put the stock can into the lathe with the top facing the chuck. I just barely tighten the 3-jaw chuck so it holds the shaft perfectly centered, but it can still slide if you push on it hard. This supports the shaft and distributes the pressure across the entire face of the can. Then I chuck up the new shaft in the drill bit holder so it bottoms out, and then I tighten it down in the chuck. Next I slide the bit holder ahead until it just touches the old shaft and lock it down. You can see this below.
http://innov8tivedesigns.com/rcgroups/ShaftPush1.jpg
Here is a close-up of where the 2 shafts meet.
http://innov8tivedesigns.com/rcgroups/ShaftCloseUp.jpg
Next I just turn the feed wheel on the bit holder and it presses the old shaft out as it presses the new shaft in. (Save the little shaft piece that gets pushed out, as this will be used later in the procedure.) Since this mini-Lathe only has about 20mm of travel on the feed wheel, I have to go the full travel, then wind the shaft back in, move the bit holder forward, lock it back down and go again. I have to repeat this process 3-4 times depending on how long the shaft is. I continue until I am about 1/2 inch from the final position I want. This photo shows the new shaft about 2/3 of the way into the can:
http://innov8tivedesigns.com/rcgroups/ShaftPush2.jpg
At this point I take the shaft out of the drill bit chuck and slide on the bearing assembly with the stator. Here I can check for interference between the back side of the rotor can or endbell and the stator windings. If there is any binding or rubbing, I can add front washers as need to get the proper clearance.
I discovered a great source for shaft spacer washers. I work in Electronics as an Enginner, so I have a bunch of old parts laying around. While I was going through one of my drawers, I came across some neat little washers. They are used on DB9 and DB25 connector shells under the screw heads. They are exactly 3mm ID and 5.5mm OD with a thickness of 0.75mm. They work great for spacing the front side of the endbell to get clearance for the windings. I also use them at the back end of the motor shaft under the C-clip. Here is a picture of the washers:
http://innov8tivedesigns.com/rcgroups/3mmWashers.jpg
Once I am happy with the clearances, I put the whole assembly back into the lathe chuck for the final push. I then take the little shaft that was pressed out, and chuck it up in the drill bit holder as shown below. This makes a nice tool to press the shaft in the rest of the way. I took the stator back out on this one before I put it back into the lathe so you could see what was going on better.
http://innov8tivedesigns.com/rcgroups/ShaftPush3.jpg
I have been using K&S aluminum tubing for my bearing tubes. They make a size that is 3/8" OD with a .049" wall thickness. The ID is just a little smaller than 7mm, so I have been using 3mm ID x 7mm OD x 3mm thick shaft bearings in my motor. The local hobby shop stocks them at a good price, and the bigger bearings last longer than the smaller ones and distribute the shaft loads better. I cut a piece of tubing a little over 1-1/2 inches long, and then clean up the ends on the lathe to make it exactly 1.500". Next I turn down one end to fit the ID of the stator. Finally I bore out each end to a 7mm ID that is 3mm deep to hold the bearings.
Here is a close-up of the final push. As you can see, I left just enough shaft sticking out to put on a spacer washer and the C-clip, and still have .005-.008" of end play on the shaft. The end play prevents the bearings from being side loaded too heavily.
http://innov8tivedesigns.com/rcgroups/ShaftCloseUp2.jpg
The back bearing takes all the thrust load in a standard tractor motor configuration. The spacer washer insures that the back bearing only makes contact on the inner race of the bearing to avoid friction and wear on the C-clip.
Now all that is left to do is add the washer and C-clip and you are done.
Well that is the process. The shaft went in perfectly straight, and the can has absolutely no wobble. I will reinforce the front end with a little 1/4" aluminum spacer and some JB-Weld.
So now all you guys out there who have a mini-lathe, or even a full size one for that matter, have a new way of pressing in your motor shafts. I am sure that this technique would also work well on the GBx series of parts. Depending on the type of chuck your lathe has, you may need to turn down a little spacer washer with a center hole to clear the bosses on the end of the GBx end bell. This would also help to keep from scratching the aluminum end bell as the shaft was pushed in.
Have fun building motors!
Lucien