WOW!!! Main bearings in a revolving tray oven? That would INDEED present a challenge.
I don't remember what brand of similar oven that I once assisted in to replace all the six tray's bearings…along with repairing some burner issues. THAT project took two of us…FOUR DAYS. I DO remember that we had to practically fabricate our own tools for pressing out/off the old bearings and pressing in/on the new ones.
I can't say whether yours will require that much time and effort. I'd have to be there to eyeball it. I'd have another tech there to eyeball too. After all, you're GONNA need help!
We'd look at it, discuss it, then come up with a plan…which would probably change many times as we go.
SO…unless someone who's actually done this comes along to offer some greater insite, there's my “how-to” instructions for you.
Yeah, as a younger tech, we did quite a few of these, of various brands, some made of bricks!. One guy on the outside, 2 inside on the bigger units. My boss had 2 specially made tools that would hang on the mainshaft, and stuck out the opening, such that you'd unbolt the shelves and slide them out through the door, down onto a table.
The spider “bearings” are usually carbon, to take the elevated temperature. Costly, and if you tried putting it in a little cockeyed, you'd be screwed.
The bigger ovens had doors on the control side to climb into the chamber. Otherwise, in you go through the front.
Make sure you check the spiders for wear and the bearings on the spider roller wheels if it uses them.
If it's a gas unit, clean the burner, pilot and electrode while you're in there, too.
To change the main bearing we have a special jack, that the factory made to go between the shelves and has a large V piece of metal that goes below the main shaft and raises the shaft slightly to allow the main bearing to be slid off and replaced. We used to rotate the bearing about 45 degrees as it has two holes in steel to allow you to rotate it, but today we just replace the bearing. We have a company that provides the bearings at far below hobarts pricing send e mail if you need parts to firstname.lastname@example.org. I can send you a picture of this jack if you provide e mail, thanks Ken