Chain tension around gears

[SunChris]

Hey folks. I'd be very grateful if you can shed some light on this for me. We have a brand of commercial spiral dough mixers from Italy that we work on. We seem to get bearings failing on the spiral quite regularly. There's no tensioner on the chain. It's basically tensioned by moving the spiral forwards and tightening it in position.

Can you take a look at the attached video and tell me what could cause premature failure of the bearings? The machines appear to be nicely built. I've always been surprised how tight they set the chains though. There's often no play in the chain when it is pushed. I spent many years messing with motorbikes and such and it was always important that the chain wasn't over tightened. It needed some play in it. Could over tightening of the chain be causing premature failing of the bearings?

Lin to video of mixer -

https://share.icloud.com/photos/02l3RbeyF0b04mG7tIpi6hTPQ#York_-_Holgate

The gear at the front is the spiral. The right hand gear is connected to a shaft that goes to the bottom of the machine and runs the bowl. The left hand gear is connected to nothing. It's just to reduce the speed from the motor and also act as a flywheel.

Here is the machine in action:

https://share.icloud.com/photos/0h9QFQ3nSrl0WAKqVnlp9mrfg#York_-_Holgate

Thanks in advance!

 

[3DDave]

It's possible the bearings are simply undersized for the overhanging load from having the spiral extend so far relative to the bearing spacing - that can produce a lot of leverage.

Is it possible that cleaning is too aggressive and the lubrication in the bearings is being washed out or contaminated?

It looks and sounds like it runs smoothly, so I don't think the chain is the problem. There should be an eccentric on one of the shafts to adjust the tension. It's really difficult to assemble chains when the center distance is too much.

 

[mfgenggear]

Summix

verify the shafts for runout, I not sure but look like the sprocket with the belt had wobble. which means bad installation, or bad bearings. bearings once get damaged will self destruct.

 

[Tmoose]

"We seem to get bearings failing on the spiral quite regularly."

Some investigation into the condition of the "failed bearings" is necessary. Smoking junk, noisy but intact and full of grease, loose on the shaft, cracked inner or outer race, or ?????????

Also upper ( close to chain) or lower bearing, or both, or ???

It is unclear to me which shaft is the "spiral" .
As 3DD said, the detailed and dimensioned "arrangement" of the bearings on the "spiral" is needed to cypher the bearing loads, in case they are the only problem.

https://www.skf.com/binaries/pub12/...RTB-1-05-Bearing-calculation_tcm_12-62749.pdf

 

[TheTick]

The machines appear to be nicely built.

Then why are you here?

 

[rb1957]

is your dough denser than Italian dough ?

another day in paradise, or is paradise one day closer ?

 

[SunChris]

Ah cheers guys. Shafts are running true. I know the drive from the motor looks to wobble but that's just the washer on top of the pulley. The pulley and shaft run true.

These are built to handle dough ranging from 55% hydration and upwards, although it is possible they've been overloaded. However, I received a video of this machine the other day which is brand new:

https://share.icloud.com/photos/0ohxPzdoNrkdEKqNyBFNhv69A#Home

The above video, we checked clearance between the breaker bar and spiral and the bottom of the bowl and all is good. The spiral seems to have a little play in it. This can only mean a defective bearing from new really. I wonder if they're using some cheap unreliable bearings.

Just trying to get to the bottom of what might be causing the issue as we've had it with a good few machines and I would expect the bearings not to need replacing within as year. They're regarded as a high quality machine but I've had a number of problems which have mostly been due to sloppy to assembly so wondered if this bearing issue could be an assembly problem.

Everything seems to run nicely so I can only assume the bearings are under sized for its application. The only thing that makes me doubt this theory is that I know people who absolutely hammer these machines on a daily basis who haven't had an issue.

 

[mfgenggear]

if the bearing are failing there is a problem, with quality, size and type of bearing. as stated before there could be a sizing for over hung load. causing the bearing to fail early.

 

[EdStainless]

Chris,
If the bearing rating is barely adequate then variations in machining/assembly could explain why some machines are more problematic than others.
I have fought with similar issues (also in Italian equipment).

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P.E. Metallurgy, consulting work welcomed