News:


  • April 26, 2024, 07:44:42 PM

Login with username, password and session length

« previous next »
Pages: [1]   Go Down

Author Topic: ST 60 -- how tight should bearings be on shaft?  (Read 1512 times)

Offline Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 12808
ST 60 -- how tight should bearings be on shaft?
« on: December 24, 2018, 03:15:27 PM »
I have an ST 60 that came to me in a Rubbermaid tub, stuck solid with castor.  I just got it loosened enough to turn, and I notice that the rear bearing is stuck, with the shaft rotating inside the race.

Clearly, this is not good and at the least I need to free up (and probably change out) the bearing.  But what should the fit be between bearing and shaft?

I'm worried that I have a spun bearing.  Or maybe I'm wondering if I should be worried about a spun bearing.  Once I get the thing apart, if there's no obvious galling on the shaft can I stop worrying?
Logged
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Dan McEntee

  • 23 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 6869
Re: ST 60 -- how tight should bearings be on shaft?
« Reply #1 on: December 24, 2018, 03:45:43 PM »



 Well, the bearing should be just a slip fit onto the shaft or a very light interference fit. I would finish taking it apart as far as you can to at least get the rod off the crank pin. Set the case with shaft pointing up on a tray and heat in the oven or with a heat gun until the bearing drops out of the case and should take the shaft with it. A light tapping on the end of the shaft with a wooden hammer or block may be needed to help things along. Then you can check out the shaft and bearing. re-assembly would be the opposite. Heat the case enough to expand the case so the bearing drops in, then the shaft should be able to be inserted as normal, if everything is OK. You'll have fun getting the liner out and such, depending o condition and how much castor sludge and gunk there is. But you'll have to do that part to get the crank and bearings out.Take your time and patience is the key here.
   Type at you later and HAPPY HOLIDAYS!
    Dan McEntee
Logged
AMA 28784
EAA  1038824
AMA 480405 (American Motorcyclist Association)

Offline Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 12808
Re: ST 60 -- how tight should bearings be on shaft?
« Reply #2 on: December 24, 2018, 05:57:43 PM »
Except that I've gotten to the point of getting the liner out, but it's not obvious how to get the piston out.  It appears that the wrist pin is installed with the con-rod on the crank -- I'm not sure how disassembly is supposed to happen.
Logged
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline pmackenzie

  • Pat MacKenzie
  • 24 supporter
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 765
Re: ST 60 -- how tight should bearings be on shaft?
« Reply #3 on: December 24, 2018, 06:11:07 PM »
Is there a hole in the back of the case, where you can remove the wrist pin?
This guy didn't quite figure it out, but if you go to the comments they mention it



(Click on the video title, it will take you to the youtube site. Then expand the "show more" to see the comments.)
Logged
MAAC 8177

Offline Dan McEntee

  • 23 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 6869
Re: ST 60 -- how tight should bearings be on shaft?
« Reply #4 on: December 24, 2018, 07:21:59 PM »
    On my first ST.46 dis-assembly, Tom Lay coached me through it by phone. He instructed to hit it with my favorite penetrating oil and let it soak. Take out the rubbing pad any way you can. While waiting, take a length of .047" or 1/16" music wire and cut it on the end with a good side cutter or lineman's pliers. Do it at an angle and it will leave a sharp point. Bend about 1/4" from the end with a slight bend in it. 10 to 15 degrees or so. this goes into the wrist pit hole through the hole in the case. Work the point into the wrist pin side and pull or twist it.  Watch for the pin to move, then work it back and forth. You can do the same with the allen wrench as mentioned in the video comments. Push it back and forth, heat some more, and add more oil. Eventually it will come loose. Some of the Tigre wrist pins are pretty tight from the factory. This was mentioned in a recent thread by some one and they can take a little polish when re-assembled. The whole procedure has been mentioned before and I think Randy Smith added some insight also. If you get bored waiting for Santa to come, maybe search the engine forums again. It's another one of those patience and time things. For penetrating oil, this would be a good one to try the ATF and acetone recipe that has circulated around. ATF has great detergent qualities and when thinned and soaking should cut the castor quickly. I just have never had cause to try it in this fashion. Let us know how it works for you.
   Type at you later,
    HAPPY HOLIDAYS<
   Dan McEntee
Logged
AMA 28784
EAA  1038824
AMA 480405 (American Motorcyclist Association)

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 13741
Re: ST 60 -- how tight should bearings be on shaft?
« Reply #5 on: December 25, 2018, 09:23:15 AM »
Quote from: Tim Wescott on December 24, 2018, 03:15:27 PM
I'm worried that I have a spun bearing.  Or maybe I'm wondering if I should be worried about a spun bearing.  Once I get the thing apart, if there's no obvious galling on the shaft can I stop worrying?

    Yes. The crankshaft slips into the inner bearing race with light pressure. It is an interference fit with the case, meaning, heat the case up to get it out.

     Brett
Logged

Offline Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 12808
Re: ST 60 -- how tight should bearings be on shaft?
« Reply #6 on: December 25, 2018, 11:56:34 AM »
Thank you all.  Knowing that the thing should come out with penetrating oil and work is a big help.

I'd seen the discussions recently on how to do this, but couldn't find them.  That was frustrating!
Logged
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Dan McEntee

  • 23 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 6869
Re: ST 60 -- how tight should bearings be on shaft?
« Reply #7 on: December 25, 2018, 01:31:28 PM »
  I hope the comment I made about the bent piece of music wire makes sense. It actually works well. I seem to recall some one saying they tapped the bore of the wrist pin to take a screw, and then used pliers to work it. That would mean that the pin is surface hardened, and I don't know if that's true enough to allow you to tap the inside bore?  stout screw extractor or easy out would let you turn it one way to help break the pin loose.  Engines are always harder to get apart than they are to put back together. Even if you get this one cleaned up nice, re-assembled and bench run a few times, and found the need to tear it back down again, it would still take a tap on the end of the crank shaft to get the crank out of the bearings and some heat to get the bearings out of their seats. After you do a few you develop the touch, feel and tools that it takes to do it and not ruin anything. You MAY ruin something in the learning process, but that mostly comes from rushing and forcing things. Have fun with it!
  MERRY CHRISTMAS and HAPPY NEW YEAR!
    Dan McEntee
Logged
AMA 28784
EAA  1038824
AMA 480405 (American Motorcyclist Association)

Offline Jim Kraft

  • 2015
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 3412
  • AMA78415
Re: ST 60 -- how tight should bearings be on shaft?
« Reply #8 on: December 26, 2018, 07:46:27 AM »
I had one Super Tigre 46 that I worked for days to get the wrist pin out, but it would not budge. I resorted to drilling a small hole in the front of the case and driving the pin out. I then tapped the hole in the front for a short screw to seal it back up.
Logged
Jim Kraft

Offline Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 12808
Re: ST 60 -- how tight should bearings be on shaft?
« Reply #9 on: December 26, 2018, 12:08:57 PM »
Quote from: Jim Kraft on December 26, 2018, 07:46:27 AM
I had one Super Tigre 46 that I worked for days to get the wrist pin out, but it would not budge. I resorted to drilling a small hole in the front of the case and driving the pin out. I then tapped the hole in the front for a short screw to seal it back up.

I think if I get that desperate I'll ship the thing to Randy!  Even in spite of the fact that the ST 60 would seal up just by putting the liner back in.
Logged
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Online EddyR

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 2561
Re: ST 60 -- how tight should bearings be on shaft?
« Reply #10 on: December 26, 2018, 04:53:13 PM »
What Jim said is so easy and the entire job takes 5 minutes. You do not need to fill the hole as it will not leak.
I did a lot of them that way.
Ed
Logged
Locust NC 40 miles from the Huntersville field

Advertise Here
Pages: [1]   Go Up
« previous next »
Tags:
 


Advertise Here