Author Topic: Making split bearings and eccentrics  (Read 4652 times)

Offline mikemill

  • Full Member
  • ****
  • Posts: 359
Making split bearings and eccentrics
« on: July 09, 2015, 10:20:20 AM »
I have noticed in several posts that makers split their bearings or eccentrics after shaping them. Two problems with this method, holding an odd shape part also being delicate very light cuts required with the slitting saw.

 Earlier practice was to face the two mating surfaces then solder together, bore the shaft hole, then drill clamping holes, separate the parts and mount on a slightly oversize mandrill then finish shape. This allows the mandrill to be held in a lathe chuck for tuning or fixed to a rotary table to be shaped.
Given that there are more than one way to skin a cat, you have a choice

Mike

Offline Jim Nic

  • Full Member
  • ****
  • Posts: 227
  • Buckingham, UK
Re: Making split bearings and eccentrics
« Reply #1 on: July 09, 2015, 02:40:48 PM »
Depends what you are modelling.  For instance the Easton and Anderson Grasshopper I recently completed has bearings where there is a gap between the top and bottom of the pedestals which sandwich the actual bearing bushes.  This was made by making the pedestal, drilling the hole and then splitting using a wide saw to produce the correct gap.  Other engines have bearings made as per your description.
As you say "Horses for courses" or for our colonial cousins "Different strokes fer different folks".  :D
Jim
The person who never made a mistake never made anything.

Offline gbritnell

  • Full Member
  • ****
  • Posts: 2460
Re: Making split bearings and eccentrics
« Reply #2 on: July 09, 2015, 03:17:06 PM »
Hi Mike,
When you say eccentrics I'm assuming you're meaning eccentric straps?
When I make connecting rods I first mill the stock to it's overall size plus an extra amount on the length for splitting and cleanup. I then drill, counterdrill and tap for the big end. This is done to keep everything in line. The cap is then sawn off and it and the rod are cleaned up to dimension.
For shell bearings I have made them two different ways. The first is to take two pieces of stock and soft solder them together. This material is then centered in a 4 jaw chuck, drilled, reamed or bored to size. If you ream don't turn the outside diameter first otherwise the material could pop apart. After the O.D. is turned the pieces can be cut off to length and unsoldered. This leaves a minute gap equal to the thickness of the solder.
I have also made the bearing inserts in one piece and then holding them in a small fixture I split them with a .010 slitting saw. In either case you end up with a small gap which won't hurt anything. The only way to make them perfectly equal is to turn them and then split them above the center line by the amount of the slitting saw. This means that one half is sacrificial so if you need eight bearings you have to make sixteen.
A friend of mine who makes excellent I.C. engines uses another procedure. He makes his rods or main bearings and bores them large enough to accept sheet silver material. The sheet silver is soft enough to conform to the radius therefore making perfect bearing inserts.
gbritnell
Talent unshared is talent wasted.

Offline kvom

  • Full Member
  • *****
  • Posts: 2649
Re: Making split bearings and eccentrics
« Reply #3 on: July 09, 2015, 05:56:27 PM »
I made the split bearing for the Joy engine by supergluing the two halves before drilling/reaming.  That went OK, but the halves did slip on one bearing when machining the bosses;  luckily this was not a show stopper.  Solder is certainly better.

Offline mikemill

  • Full Member
  • ****
  • Posts: 359
Re: Making split bearings and eccentrics
« Reply #4 on: July 10, 2015, 09:40:14 AM »
Gbritnell
Regarding bearing shells, I have the building the Offy book by Ron Colonna, he shows silver plate as ideal material for shells. This engine is on the to do list!!!! Well someday

Mike

Offline sshire

  • Full Member
  • *****
  • Posts: 3044
    • LS Editions
Re: Making split bearings and eccentrics
« Reply #5 on: July 10, 2015, 12:26:00 PM »
"Real" bearing shells for some military helicopters are silver plated to a thickness of .010-.015.
This corresponds to approx. 25 to 30 gauge silver sheet.
Another bit of semi-useful information that I learned in the Air Force Reserve.
Best,
Stan

Offline steamer

  • Global Moderator
  • Full Member
  • *****
  • Posts: 12697
  • Central Massachusetts, USA
Re: Making split bearings and eccentrics
« Reply #6 on: July 10, 2015, 12:36:07 PM »
I suspect that friend of George's is actually....Ron.

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

 

SimplePortal 2.3.5 © 2008-2012, SimplePortal