How do you remove a wound tachometer from a motor shaft?

[DubbleTrubble]

I've been working through a Haas HRT9 that I picked up at auction a few months back. It is tripping a "Hi Curr" error on the controller. I've covered much of the process in another thread here on PM - https://www.practicalmachinist.com/forum/threads/should-it-spin-by-hand-hrt-servo.403540/ Because this isn't a Haas specific issue and I haven't gotten a response in the other thread to this specific issue, I'm hoping the bigger audience might be able to help me.

I found a nice replacement servo on eBay with the same 3528 motor and F windings. It was the only one I could find after looking around for a week. The replacement motor has a tach, which I need to remove and I only have one chance to get it right. When I say tach, I mean the type with its own commutator and windings riding on the motor shaft.

As you'll see in the pictures below, the tach rides on a 5/8 OD hollow shaft that surrounds the 1/2" motor shaft. I can't quite get visual access to the end of the 5/8'' portion because it is hidden by the brush holder, which cannot be removed without removing the tach (I think).

My first thought is to use a gear puller to pull the tachometer and 5/8" shaft off the motor shaft. Before just going for it, could someone confirm whether this would be the best way to go at it or should I try something else? Should I use any heat? Should I try to remove any of the blue epoxy towards the bottom of the 5/8" section?

I appreciate any help offered.

 

[atex57]

Do you need to remove it for clearance? Are you trying to save it? The epoxy or other adhesive would have to be warmed up to make it release. Heat up a piece of round stock and press it to the end of the shaft, maybe a couple to keep it hot. Otherwise brute force and dynamite.

Ed.

 

[DubbleTrubble]

Do you need to remove it for clearance? Are you trying to save it? The epoxy or other adhesive would have to be warmed up to make it release. Heat up a piece of round stock and press it to the end of the shaft, maybe a couple to keep it hot. Otherwise brute force and dynamite.

Ed.

Thanks for the help. Yes, I need to install an encoder in the location where the tach sits. I am limited by space and can't have both.

 

[atex57]

Caveat: I don' know s**t about Haas.. but the "physics" of it are the reverse of what Atex suggested.

The heat is to decompose the adhesive, not to affect the fit. When the adhesive releases pull it off while warm. BTDT.

Ed.

 

[DubbleTrubble]

Thanks guys. I appreciate the help. I'll give it a go, per the suggestion, with the intent to save the tach.

 

[DubbleTrubble]

Even a "stranger" might guess that adhesives are PROBABLY used on Haas goods, yes. Very 'young' company.

Are you familiar Röhm and Haas? I believe that was founded in 1909. It's a chemical company, acquired by Dow at some point. Interesting that both Röhm and Haas ventured into machinery.

 

[gbent]

Looks very similar to the motor I had to replace on my Hurco control, made by Cleveland Machine Controls. CarbideBob posted some information that was instrumental in my finding an adaptable motor. Let me look at my stuff tomorrow as I can't remember how it was all put together.

 

[DubbleTrubble]

Looks very similar to the motor I had to replace on my Hurco control, made by Cleveland Machine Controls. CarbideBob posted some information that was instrumental in my finding an adaptable motor. Let me look at my stuff tomorrow as I can't remember how it was all put together.

Thank you sir. I'll be interested to see it. This sounds familiar and I may have seen it before during my research, but I would really appreciate seeing it now. This stuff isn't too bad, once you get it figured out, but when coming in cold, it feels a bit daunting.

 

[DubbleTrubble]

If today's shouty-greens only knew how shiddy things USED TO BE, they'd dissolve directly into the toxic slag heaps we had long paved walking paths, carparks and driveways with.

Haha, so true.

 

[gbent]

I used a bearing splitter on the outside of the laminations and tapped the shaft with a dead blow hammer. You can see the knurled portion of the shaft the shaft that was used to grip the tachometer rotor.

I will have to see if I can post a picture. I'm getting file size to large error.

You only need to move the rotor about a quarter inch to free it from the knurled area.

I'm guessing the hole in the end of your shaft is to allow you to use a punch to make it easier to tap on the end of the shaft without riveting the end of the shaft. Mine was easier, as there was a "where are you" sensor on an extended shaft behind the "how fast are you going" sensor.

 

[DubbleTrubble]

I used a bearing splitter on the outside of the laminations and tapped the shaft with a dead blow hammer. You can see the knurled portion of the shaft the shaft that was used to grip the tachometer rotor.

Interesting. That does indeed look very much like mine. I hadn't contemplated a knurled portion of the main shaft. Hopefully I can work around it when setting up the encoder on the shaft. Thanks for the pic and intel.

 

[DubbleTrubble]

Well, guys, I tasted the sweetness of anticlimactic success, after the research, assistance from you guys and the prep work. I planned to heat things up, but first I set up with a bearing splitter to grab the bottom of the tach and the associated puller. Out of curiosity, I put a tad bit of pressure on the wrench and the tach moved with minimal effort, so I kept going, and it easily came off without any issues.

The knurling is a bit interesting. I though the shaft had been knurled, however the 1/2 shaft is turned down a bit and there is a sleeve over it with the knurling. That won't be an issue since I plan to turn down the shaft and use a 1/4" bore encoder. There are plenty of encoders out there for $25-$40 so long as the encoder bore is 0.25" or less. A 1/2" bore encoder would run me $250+. The encoder on this unit is really basic (A, B, Z, V+, Common) so I don't need anything fancy.

I reconfigured the new rotor/stator with the end caps from the original motor and everything went together well. I'll need to mill a slot in the shaft at one end for the pulley's 1/8" keystock, and turn down the other end for the encoder.

Thanks for the help on this. This was so simple and I thought it was going to be more of an issue.

Pulling rig

Success

Close-up of the knurling

The replacement motor is above the original. The difference in shaft lengths will not matter in my case and I will turn them down to the correct length and diameter as needed. Everything buttons up quite well.