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Skywalker bearing changeout
Mike_Mathis
Top  #1 Print Post
Posted on 05/17/2024 5:11 PM
Situation: I was in the middle of a 350g roast and the drum motor started making a straining noise and the rpm’s slowed to a crawl. Maybe 10 rpms and intermittent stops and restarts. The motor that turns the drum operates on the fringe of its torque limits. The bearings need to be in good condition or a roast failure as mentioned above can occur.

Tools required to do the bearing swap are a small hammer (I used a small ball peen) a paint can opener or similar device, a small block of wood, and a flathead screwdriver. Retainer ring spreader pliers would be a definite advantage.

It is important to note that the two bearings are entirely held in place by a retaining ring. No tight pressure fit (however, the tolerances are very exact). The bearings were installed with what appears to be a few drops of superglue between the outer races and the housing. This is not a point of major contention.

Remove the back of the roaster to access and remove the drum motor.

Remove the roaster front parts to access and remove the drum. Philips screwdriver and T15 torx for front and a T25 torx to remove drum (I purchased a nine inch long T25 and it works very well for drum removal). This gives access to the four screws that hold the bearing housing in place.

After you remove the housing containing the bearings, remove the retaining ring and set the housing on top of a spread vise so you can tap the coupling to separate the two housing parts. Use something to hit it square. It will not require much force at all. After separation, you will see there are two bearings (part #6807Z). They are mounted on either side with a ridge between them. I show this ridge in a few pics. I used the 90° bend in the paint can opener to twist between the two bearings where they meet at the ridge between them. One of them will pop loose. At this point just work your way around the circumference of the bearing, twisting ever so slightly along the way. A little patience is required. It will only move a tiny bit at a time. After the first one was loose to a certain point, it just fell out. To remove the other bearing, I laid the housing on top of a vise that was spread so the bearing would have room to fall through when TAPPED OUT. That is all that’s required, just a little light tapping. This should be done with something that covers the outside edges of the bearing for evenness. We’re not really worried about the bearing but we want to protect the housing so try to hit squarely.

Once the bearings were removed, I cleaned the seats up carefully to remove the super glue residue while trying not to scratch or mar anything. The new bearings just snap into place. Make sure they are completely seated against the seats. If not, find something that will sit on the outer race and gently tap it in. I had a 30mm socket that worked perfectly for me. Remember to protect the bearings by using very gentle taps. You will know they are properly seated when the groove for the snap ring will seat properly. The bearings without the snap ring in place would fall out, but the fit was with no slop at all.

REVISION: The last statement turned out to not be completely true or accurate

I tried to attach a few pics and a video to show the improved ease of rotation after installing the new bearings, but I kept getting something about fakepath even though the sizes were 800X800, less than 10MB and no special characters. I’ll post the link where I purchased the bearings even though you can get them at other places.

https://www.amazo...ct_details
Edited by Mike_Mathis on 05/19/2024 1:37 PM
 
renatoa
Top  #2 Print Post
Posted on 05/18/2024 1:08 AM
Thank you for detailed explanation of the process, and bearings part number, would help when my turn... soon...

Thinking to get a different model, same size, but with a built-in snap ring groove, i.e. having added the NR suffix, like this: https://www.2rs.b...ro-ro.html
Will remove the need for a snap ring, what do you think ?
 
Mike_Mathis
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Posted on 05/19/2024 1:07 PM
I need to post a follow up to my post. After testing with 400g green beans rotating for 10 minutes with no heat, it seemed everything was ok. Well, after I started roasting later, I ran into an issue with the bearing clearance in the housing. The drum started dragging on the front plate. It was as if I had not tightened the T25 screws that hold the drum to the bearing plate, but that was not the case. There was too much play between the bearing outer race and the housing. This is where the no need to press the bearing in with some force came into play. The fact that the weight of the drum AND the bean charge was too much for the ever so slight fit. I shimmed the bearing to the outer race and outer housing with .001 inch shim stock in 4 places. Also 0.30mm in metric. This gave it a fit that did not create a drag for two roasts. Time will tell but the shims are more solid than the glue the manufacturer used. There may be a better solution. I will inform if I have any future issues. renatoa, I will investigate the bearings you refer to and of course post any findings. If they are as cheap as the other ones I will buy them and see how they do.
*Kaffelogic Nano 7
*Skywalker V1
*2023 BC-2
 
Mike_Mathis
Top  #4 Print Post
Posted on 05/19/2024 1:17 PM
https://www.walma...5426899803

Ouch! These are rather pricey compared to the others. No wonder the OEM used glue.
Edited by renatoa on 05/19/2024 1:47 PM
 
Mike_Mathis
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Posted on 05/19/2024 1:45 PM

Quote

renatoa wrote:


Will remove the need for a snap ring, what do you think ?


The snap ring appeared to be plenty tight to hold the bearing in place. Between the outer race and the housing is where the specs are not tight enough to prevent the weight of the drum and beans from allowing excessive play. I used a piece of shim from a cheap shim gauge set to cut the 4 pieces to insert and used thread locker as a glue to hold them in place while I inserted the bearing. I did need to tap with a little force to get what I believe to be a tighter fit.
*Kaffelogic Nano 7
*Skywalker V1
*2023 BC-2
 
Mike_Mathis
Top  #6 Print Post
Posted on 06/07/2024 8:25 AM
An update on changing out the bearings in the Skywalker. After putting the shims between the housing and outer races, the drum is solidly in place. If I remove the front to expose the front of the drum and press up on the front end of the drum, there is no play at all. It makes the back wall where the drum is attached flex. Also when the drum is turning, the space between the front edge and the metal face is consistent.
*Kaffelogic Nano 7
*Skywalker V1
*2023 BC-2
 
renatoa
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Posted on 06/07/2024 11:21 AM
A picture from the back, with the snap ring, possible, please? smile
 
Mike_Mathis
Top  #8 Print Post
Posted on 06/10/2024 2:31 PM
.
Mike_Mathis attached the following image:
bearing3_1.jpg
*Kaffelogic Nano 7
*Skywalker V1
*2023 BC-2
 
renatoa
Top  #9 Print Post
Posted on 06/10/2024 3:11 PM
Same as mine... so I am puzzled about the role of the retaining clip.

You wrote in the introductory post that...
"The bearings without the snap ring in place would fall out"

Mine are very well seated into the flange, and the role of the clip is to not let drum go forward, and start rubbing the front panel.
If this happens, I knock the drum gently to push it back into the bearings, and is good again for another 3-4-5 roasts.
I wasn't unable to place back the clip in the groove properly, and my feeling is this could be the real reason of my locks... looks like I broke my machine myself ... placing the clip in a bad position... if doing this it starts to rub the back bearing very bad, and finally brakes completely during preheat, about 180C.

Very confused...
 
renatoa
Top  #10 Print Post
Posted on 06/10/2024 3:17 PM
Another finding, during my quest for a replacement bearing, I found that standard bearings are good up to 120C.
So any replacement bearing someone will supply should be rated at least 200C, imo
This means C4 class, in bearings language.

Quote

Those numbers indicate the clearance between the balls or rollers and the races.
The C3 bearing is the bearing that is used for normal applications.
The C4 bearing is looser or has more clearance and is used in hotter environments.
When running at temperature, the C4 bearing will expand and close the gap
 
HarryDog
Top  #11 Print Post
Posted on 06/12/2024 1:22 PM
The NTN bearings that I ordered off Ali express if real on the web site claim to be 200c+
Products are arriving much slower lately from china, so I don't have these yet.

I'm looking at some cheap bearings (I have not tried to replace any yet) If the bearing is fully seated then the clip should not touch the bearing or outside race as the inside race is slightly wider on the cheap ones I have.

If the clip is touching the outside metal seal (Don't know the exact term) or race beveling the outside edge of the clip might keep it from touching if the bearings are of high enough tolerance (Any play)? If the clip is not completely seated this will also be an issue.
 
renatoa
Top  #12 Print Post
Posted on 06/12/2024 1:48 PM
The bearing could be fully seated, probably you means into the flange... but the clip is touching at least the inner ring of the back bearing, because the drum weight force the forward movement of the drum, until one of two events happens: either the drum touch the front panel, either the clip will stop the movement.

I don't see how you can avoid this horizontal advancement force along the drum axis, without having other support points in the front panel, as two small bearings.

If your drum has no such tendency to advance... this means that your drum flange shaft has better fit inside the bearings, and mine is loose and only the clip is the stop... with the cost of wearing/damaging the back bearing.
Edited by renatoa on 06/12/2024 2:00 PM
 
HarryDog
Top  #13 Print Post
Posted on 06/12/2024 2:34 PM
Yes to fully seated in the flange. I think the design is to have the clip stop the drum from moving forward and run on the inside race but not touch the rest of the bearing.

My bearings are still working as intended but I want to be ready to replace them if needed. So far very little rubbing on the front plate.

I have been looking at rollers on the front bottom of the drum but I think this is so light the drum won't last. Maybe a SS running plate if it can be tacked to the outside of the drum? Then run two support rollers on that.
 
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