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Improved bearing on the drive side (This may not be a good recommendation, but here it is.)
Yasu
I had no idea what I was doing with my own roasting machine.
I thought of an ingenious idea in the bearing section.
Please give me your opinions, advice, etc.

I have adjusted the clearance of the drum bearing on the full plate side to about 0.1mm (I dare to say that the clearance can be set arbitrarily), and the bearing on the opposite side is received by a linear unit so that it can slide. The following are the main features of this unit.

(1) Ease of restoring the original position after maintenance such as belt replacement.
 ⇒After replacing the belt with another one, the entire surface clearance is shifted, eliminating the need for troublesome adjustments, etc. Belt replacement can be done simply by loosening the set bolt on the pillow, and after replacement, the belt returns to its original position by simply tightening the set bolt.
(2) Cancellation of the effect of thermal expansion of the drum on the clearance.
 ⇒The topic of heat-resistant grease is often mentioned as a cause of bearing damage, but I believe the real cause is often the bearing receiving the force of thermal expansion of the drum. (Wouldn't it be about 1~2mm longer?)
 With this structure, thermal stress is not applied to the bearing because it slides freely even if it expands.
(3) Aiming for "0" clearance adjustment at the front of the drum.
 Adjust the clearance on all sides during cooling, and check the clearance during use (heating).
 Adjust again during cooling. It is impossible to aim for "0".
 With this structure, the clearance can be set to "0" or arbitrarily set during cooling and fixed there, and the thermal expansion can be absorbed by the slide.

I am attaching a photo.
Photo shows a large pasta pot storing drums.
(The drum is rotated inside the pasta pot for better sealing)

Yasu attached the following image:
p_20220515_120054_vhdr_on.jpg

Edited by Yasu on 05/16/2022 2:44 PM
 
Yasu
I don't know any commercial roasting machines, but what is the concept of fixing the drum at both ends?
1) Drive side fixed: front side free -> clearance changes
2)Fixed at both ends→Thermal stress is applied to the bearing.(Or is the expansion of the drum cancelled because of the structure of the casing, which also serves as the frame and gets hot?)
3)Drive side free:front side fixed→seems best. What mechanism will achieve this? Just not fixing the shaft to the bearing inner ring?
Edited by Yasu on 05/16/2022 4:06 PM
 
espresoman
Drive side fixed: front side free.

This is the best option but the ring that you put on the mobile side, must be welded on the fixed side / front.
And the distance between the drum and the fixed part should be perfectly parallel and not more than 3mm. Underneath will fall a little chaft, you have to make a side drawer that will collect that chaft.
If it helps I can try filming at mine Toper as it is done.
espresoman attached the following image:
screenshot_20220517_215027.jpg

Toper Cafemino 1kg + TC4s Renato logger
 
allenb
"Drive side fixed: front side free". I'm curious why one would not want the front gap fixed and let the rear float? I've used this method on my drum roasters and have liked the way the gap is always known and no rubbing to ever worry about. Let us know what the benefit of having rear fixed?
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
allenb

Quote

Quote

I don't know any commercial roasting machines, but what is the concept of fixing the drum at both ends?
2)Fixed at both ends→Thermal stress is applied to the bearing.(Or is the expansion of the drum cancelled because of the structure of the casing, which also serves as the frame and gets hot?)


Not sure why some or most drum roaster manufacturers fix both ends. Even if the frame components eventually expand some once everything comes to equilibrium, those structures would never equal the shaft length growth which does cause a degree of bearing stress.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
renatoa
Steel dilatation is 0.06 to 0.07 % for each 100F degrees in temperature.
Thus about 0.32% for 500F/240C... 1mm for 30 cm / 12" long shaft.
And frame dilatation is close to the shaft, indeed... so...
 
Yasu
My roaster is constructed with an aluminum frame on the outside with a drive shaft for the drum.
This was a choice I had to make because I do not have the welding and metalworking skills that you have.
As a result, all the values calculated by Renatoa-san are applied to the bearings as thermal stresses.

Actual thermal stress F =-α×ΔT x E x A
α:coefficient of linear expansion
E: Young's modulus
A: Drum cross-sectional area
and cannot be ignored in a thick-walled or double drum.
In addition, the thermal stress between the drum and the full surface plate
This structure was adopted to avoid gaps and contact between the drum and the full plate.
The clearance between the full face plate and the drum can be easily adjusted by simply turning the set bolt.
Edited by renatoa on 05/18/2022 6:15 AM
 
Yasu
The set bolt on the clamp lock to the shaft of the drum pushes against the bearing inner ring and pulls the shaft.

While turning by hand, pull until the drum hits the play and then back the set bolt 1/4 from there. 0.1mm

The inside of the drum is non-pressurized, so very little chaff or debris falls to the bottom.
 
Yasu
Not sure why some or most drum roaster manufacturers fix both ends. Even if the frame components eventually expand some once everything comes to equilibrium, those structures would never equal the shaft length growth which does cause a degree of bearing stress.[/quote]

I am thinking the same thing.
There is not that much shock, the RPM is as low as 60RPM, and even though it takes a lot of heat, the bearings are only 20 I think it is because it is not a good design to have to replace the bearings every year, even though they do not reach 0°C.
According to the bearing shop's life calculation, with this much load, I don't think there is any need to replace the bearings even year after year.
I thought that thermal stresses were damaging the bearings.
Maybe roaster manufacturers like to replace bearings.Grin
 
Yasu
I did the math once.

Actual thermal stress F =-α×ΔT x E x A
α:coefficient of linear expansion  11.8×10-6/℃
E: Young's modulus        205000MPa
A: Drum cross-sectional area φ400×1.6mm=2017mm^2

F=975824.6 N

6008ZZ Basic Rating:axial load 11500N

It seems to be a stress response that relies on bearing rattling
The calculation was such that if the bearing rattles were installed on the opposite side in the setting, it would be subjected to a force that would cause it to break in one shot.
axial (I think the internal axial gap is about 0.3 mm.)

Am I wrong in my calculation?
Edited by Yasu on 05/17/2022 8:03 PM
 
Yasu
Here is an excerpt from one manufacturer's manuual.
I found this today.

It seems that this manufacturer's approach is the same as mine, which is to adjust the front gap to fix it.

I did not understand the structure of the drive side.
Yasu attached the following image:
screenshot_2022-05-20-05-37-56-360.jpeg

Edited by Yasu on 05/19/2022 3:55 PM
 
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