Hello all, I recently tried unsuccessfully to install a new motor onto a HO scale brass locomotive. I attempted to install the flywheel onto the motor shaft. I tired this with the help of an arbor press. In doing so, two issues happened. One, the motor shaft moved almost completely through the motor and two the shaft after moving completely through the motor bent. I recently got a new motor and flywheel and will attempt to do this again. What is the easiest way to perform this work without bending the motor shaft? Is there an easer way to do this? Thanks.
The bottom of the motor shaft has to be supported by the base of the press. It sounds like you had the motor body on the base, instead. 'Cause if you’d done the former, either the flywheel would have slid on, or the shaft would have bent right away, not moved through the motor.
You’re trying to do an interference fit. There’s very little room for dimensional error. See:
http://en.wikipedia.org/wiki/Interference_fit
for a bit of info on the matter. Further searches will reveal more. You’re dealing with dimension tolerances in the thousandths of an inch, here.
Before trying to do this again, I recommend you ACCURATELY get the dimensions of the motor shaft and the hole in the flywheel. The latter should probably be a thousandth or maybe two greater than the shaft. Getting the diameter of the shaft is easy. The hole, not so much. It might work out to use drill bits. The accuracy won’t be great, but the cost will be minimal. And it’s far better than just trusting that the dimensions are right. You’ll at least have SOME idea of them.
If the dimensions are right, then you come to the assembly method. You should taper the shaft and/or the hole enough to get a good start. I wouldn’t try doing this kind of press fit unless I could kinda stick the flywheel on the end by hand JUST A VERY LITTLE AMOUNT. You must also make sure the shaft is vertical–parallel with the arbor shaft. It must stay in that vertical orientation the entire time of the pressing. And, as I said at the beginning, you’ve got to have the “bottom” of the shaft resting directly on the base of the press. You might have to disassembly the motor, or maybe do some fancy support blocking. But the shaft must rest on the base.
IF the dimensions of the shaft and the hole are correct, it’s now a piece of cake. Just pull the handle. If
If you ended up pushing the shaft through the motor you were supporting the pieces incorrectly. Sounds like you were supporting the motor frame at one end and pushing on the shaft from the other. You need to block the opposite end of the shaft from where you are pushing, and no force should be applied to the motor frame.
Also, you need to check the diameter of the flywheel hole against the outside diameter of the motor shaft. I think there should only be a thousandth or two (0.001 to 0.002 inch) interference fit with the flywheel diameter being smaller.
You will also need some way to keep the end of the shaft where the flywheel is to be mounted from moving sideways as the flywheel is pushed on. If there is too much free length it is likely that any unintentional sideways force will act to be the shaft.
You might also wish to try heating the flywheel to expand it to temporarily increase the hole diameter… Maybe a boiling water bath would get it hot enough. But you will need to handle the part carefully when heated, and avoid getting any residual water into the motor.
on my first attempt, I allowed the opposite shaft slip through the hole in the bottom of the press while pressing down on the shaft where the flywheel was. That is how the shaft came to travel through the motor. Then I supported the back of the opposite shaft against a block of wood and had the v plate around the shaft as well while pushing against the top of the shaft with the flywheel on it with the arbor press. This is how I bent the opposite shaft severly on the second attempt. When I purchased the flywheel and the motor, the shaft and flywheel were already champhered (beveled) to allow the flywheel to start. The shaft is 1.5mm diameter as is supposedly the flywheel. The directions recommended that I run a drill bit 1/2 way through the same diameter (1.5mm) to assure that the shaft doenst have trouble going through. Are there any recommendations I should consider about how to support everything so this wont happen again?
Theoretically, if the shaft is dead parallel with the arbor shaft, and the base is exactly 90 degrees to that, the shaft CAN’T bend. That would be theoretical. But I strongly suggest you get it as close as possible. Myself, I would consider clamping the motor to a nice square block of wood. Then my attention could be elsewhere than trying to keep everything lined up with my extra hands.
Now as to shaft and hole size and minimizing the chance of bending something:
The shaft is 1.5 mm. That is, to we Americans, .059 inches. I strongly recommend you check that dimension.
My poking around on the internet leads me to think an interference fit would be a hole of .058 inches. That is, a hole .001 smaller than the shaft. The closest thing to that is a 1.45 mm drill bit at .057 inches. I am very wary of a press fit any tighter than the .058, but I note that the 1.45 mm bit should pass nicely through the hole in the flywheel. Or there’s a problem.
Now, all that’s one approach. Another would be to drill all the way through with a 1.5 mm and see how tight the flywheel is on the shaft. It should either be a pretty good fit of very slightly loose. If the latter, Locktite of the proper color should do things up nicely.
Your mention of the half-way through 1.5 mm hole is another interesting route. Not a bad idea. But I still think it EXTREMELY WISE to check the two diameters before proceeding.
Ed
Some years ago I modified some HO locos using NWSL MDC replacement gears, Flywheels and Sagami motors. I supported motor end shaft on one end. Chamfered the other motor shaft before installing the flywheels on one end at the work for the opposite end.
I also used the NWSL Aligners. Pressed into place using a drill press.
Oh, the motor was placed in a freezer which was about zero degrees F before doing all this.
For intermediate gears, I did the same with the shaft needed for the gears. Did this with the one driver that needed a spur gear. Working with fine tolerances for this stuff. Patience.
I have old documents from NWSL when it use to be in Seattle, WA
Chamfering is very important and as a former machine mechanic, this is important. I have pressed large gears onto shafts that where chamfered.
Rich
If you have the proper drill bits, you can make your own aligner for 1.5 mm. A digital caliper and micrometer are very useful tools. You can find them online for very reasonable prices if you know how to shop.
Rich
What is the manufacturer and P/Ns of the parts you are trying to use?
The parts are NWSL 1630D-9 motor and a NWSL 425-6 1.5mm 12 x 11 flywheel. I think I need some sort of tool to support the shaft and or Im not using the arbor press correctly. I have a v plate and I have all the bits NWSL and Micro Mark stated that I needed to perform this proceedure. Im not sure I used the correct bit or perhaps the wrong end of the arm on the press or both. I was using the v press to support the side of the opposite shaft on the second attempt after the shaft passed almost all the way through the motor. May be I put too much pressure on it because that is why the shaft bent on the second attempt. I was told that there is a tool that I do not have that supports the shaft. On the first attempt, I allowed the opposite shaft to pass through the base of the arbor press. I took out the screw that screws in the base. I had no support for the bottom end of the shaft and that is why I think that the shaft passed through the motor. On my second attempt, I put the screw back in the base to support the bottom of the opposite shaft put the v plate around the side of the opposite shaft and supported the end of the shaft with the flywheel on it against the arm of the arbor press. This is how it bent. I just feel im not using the press correctly.
Loco
I don’t know what your press looks like and I have never installed a flywheel but maybe a fresh look at the problem would help. I’m thinking in terms of a drill press configuration.
#1 the motor and shaft have to be in alignment with the press shaft.
Would drilling a hole in a block of hardwood or hard plastic, even aluminum (on a drill press), just deep enough to support the shaft with the motor case resting against the block help with the alignment problem?
Then would a square head on the press shaft could keep the flywheel square with the shaft??
I defer to the machinist but maybe we don’t all have the tools he would have?
Good luck.
Lee
I have used my bench vise to press flywheels and gears onto shafts without bending or breaking anything. I also used my drill press to press flywheels on that have the motor shaft stick out past the flywheel. If the shaft is longer than the flywheel and sticks out past it then you will need to support the flywheel on something that allows the shaft to pass into. You can place the flywheel on a socket the same as the outside diameter and press the motor shaft into it. Just make absolutely sure you are pressing on the motor shaft and not the motor housing.
You may also try a heat expansion fit. Put the flywheel in the oven at 300 degrees for an hour at least. It may just slip right on and shrink when cool to a nice tight fit.
I have also used Loktight retaining compound (Threadlock) to repair locomotive drivers that have loosened on the axles of some steamers. So if you ream out the flywheel to the same size as the shaft the retaining compound will keep it there.
Pete
It sounds like you made a mistake the first time when the armature was damaged. The shaft was not supported correctly. The v plate is used to slip behind a gear, worm or a flywheel for removal. It is not used for installation.
The second time could be a flywheel problem. NWSL states they use a “light interference” fit. Unless you severely cocked the armature during the second attempt, the flywheel should have gone on easily. The shaft is hardened steel and strong enough to allow a properly sized flywheel to be installed.
The P/Ns you supplied are correct. Before attempting this again, check the size of the flywheel hole. If you have a numbered drill index, a size 54 is 0.0550. This drill should easily pass inside a 1.5mm hole which is 0.0591. The next size is a 53, which is 0.0595 which will not pass through a 1.5mm hole.
I have installed NWSL flywheels by standing the opposite shaft on the anvil part of my vise. A tiny tack hammer and a few taps on the flywheel centered on the top shaft were all it took. I have also used this method to install back to back flywheels for more mass.
Using the damaged shaft, can you begin to tap it into the flywheel? It should be easy to do so. To remove, use a pin punch from the other side and tap it back out. If the size is not right, a call to NWSL is in order.
You could place the motor overnight in the freezer, and heat the flywheel in the oven. The brass is a softer material so it will expand more than the hardened shaft will shrink. Between the two you may gain a thousand or two of extra clearance. Be sure to grease the shaft also.
Thanks everyone! Another thing I found out that I did not have the ram arm in the Sensipress correct. I used the end that the bits go in instead of using the brunt flat end. Silly me I guess. These are all great ideas that I will try on the next try. It sounds like Im making it more difficult then it is. Ive never done this before and it is a learning experience for me. I have at least 3 locomotives now that need either repowering or regearing or both. I have this PFM 2-8-0 with the open frame motor that Im working on now. My OMI (Rok-Am) RF&P 4-8-4 that I need to regear and repower in the same manner and a couple of my Rivarossis that need repowering. (they have the old motor in the back of the cab) So any ideas is greatly appreciated. Thanks again.
Why repower? I have been swapping the iron magnet from the open frame motor with super magnets from K&J magnets. An example.
The magnets will tune the open frame motor cheaply and easily. When I tested this motor it drew over 2 amps stalled at 12 volts DC. After the magnet swap it draws .85 stalled at 12 volts DC. Beside this PRR K5s I also did an MB Austin 2-6-0 and installed a Loksound Select decoder. With the BEMF and a little momentum there is no need for a flywheel.
I ordered a dozen 1/4x1/2x1/8 thick item #B842 and six 1/16 inch thick magnets #B841.
Pete