I am one that does't typically believe everything I hear. Even if the roaster is making some crazy sounds and I think I might know what is going on, it never hurts to have someone else lend an ear. In this case, I came close to spending cash on a motor when in fact it only needed to be inspected closely. A high pitched squeal accompanied by a serious repetitive knocking sound was coming from the motor on the L12. My first reaction was to replace the motor and be done with it. I have replaced these Baldor motors (the only brand name motor I trust) in the past after they accumulated many miles and I thought the need to replace this motor was no different. Talking it over with Kyle, our well wrenched Warehouse Manager, he was under the impression that the motor was on it's way out after hearing my plea. Tom had other ideas of what could be going on here. He urged us to disconnect the motor, and check the squirrel cage fan that directly connects to the motor shaft. He thought that it was possible that the motor might need to be shimmed a bit to loosen the tension with continuous belt which would release some pressure off the motor. It does make sense to take the most cost effective angles before spending $400 on a new motor, right?
It's always stressful for me to take the nuts and bolts off of a roaster. I fear for the potential problems I might run into along the way. In the past I have found stripped threads or a piece that needs to be replaced that I am not prepared to fix. There is always the potential that there might be some downtime to fix an additional issue, and that haunts me. I can't stress enough how important it is to have a contingency plan in place if such an event happens. It's a great idea to set up a plan to use a nearby roaster just in case you might need to be down for a while. Not being able to roast coffee for your shop or your wholesale accounts can ruin you. Scary, but true.
This L12 has one motor. It's a .75 horse power single phase that plugs right into a 110 outlet. The motor was definitely pulling hard here. The squealing and knocking sounds it was making was one indication, and another was the plug itself. Holy smoke! The whole plug was melted from the electrical draw. Now either the wires were not tightened down all the way on the plug or the motor is drawing heavy amps because it's working extra hard for some reason. Either way, there was some crazy resistance happening here with the electricity. Replace plug... CHECK!
The motor sits on a mount that is welded to the back plate of the fan housing. The motor had to be removed first in order to take the back plate off. The point where the motor shaft slides into the squirrel cage is met with 3 locking set screw with a hex key head. There is also a lock key that runs along one side of the outer motor shaft and inner squirrel cage to keep it in place.
After all the motor mounting bolts and set screws have been removed, you can slide the motor out of the squirrel cage mount. The squirrel cage will fall off inside the housing. There are probably a few different ways of dismantling this, but this way worked okay in our case.
Now unbolt the back cover to see what kind of condition this cage is in. You can bank on it being full of all kinds of creosote and chaff build up. This is a good place for embers to smolder which can result in a nice fire if not kept under control. This piece of your machine should be cleaned out from time to time depending on how often you roast.
Now it's time to clean this thing up. I like to use firm putty knives and wire brushes to get this crud off. Be sure to get it as clean as you can and vacuum up all the mess. The squirrel cage is not really a cage for putting squirrels in, but acts as a industrial strength fan blade that draws the airflow through your roaster. I assure you, no animals were harmed in performing this operation.
After getting this cleaned up and put back together, I let it rip. There were no more squeals or knocking sounds coming from the motor. I was shocked that it wasn't a bad motor as it hummed along, smooth as ever. My guess is that it could have been several things, or a combo of these things that caused the sounds:
1. A build up of resin and creosote could have caused an imbalance with the squirrel fan which could also cause stress on the motor and the amperage it was pulling.
2. The set screws and or locking key that holds the fan on the shaft could have been loose which would also cause an imbalance with the squirrel fan.
ONCE AGAIN I learned that I need to start with cleaning parts, inspecting thoroughly and choosing the most cost effective way to fix a problem. It's always best case scenario to keep your employer and your cash flow happy.