Introduction: Belle Maxi 140 Concrete Mixer Overhaul
After some recent work using my Belle Maxi 140 concrete mixer it developed a fault. It would work ok in one direction but when the drum was turned to face the other side, it slowed down and then stopped. The motor was struggling and eventually the overload device popped out and the motor was overheated. I decided to completely overhaul the mixer as a similar replacement to this 17 year old machine was now extremely expensive
Step 1: Strip Down
Luckily these UK made machines are still in production and most of the parts are available.
The internet was useful for finding and printing off an exploded diagram, invaluable prior to dismantling the unit.
It proved to be an extremely filthy job so I took care to minimise the muck by carefully disposing of it at each stage. I washed off all the greasy and dusty parts in kerosene as they became free.
Step 2: Clean Off
It turned out that the main problem was the drive belt contacting the housing. This was due to a stretched belt. The new belt was an old car fan belt 5mm shorter than the measured belt taken from the mixer. I could have bought a genuine Belle part but to save time I bought a car fan belt locally.
This was still fractionally too big so the motor had to be adjusted. There was not enough drift with the existing set-up so I had to make two of the mounting holes into slots.
Make sure the motor is parallel to the pulley when adjusting the tension during rebuilding.
After rebuild the belt now clears the housing and runs very well. The new belt is toothed but this seems to work ok. The large driven pulley was catching on the housing back plate so I inserted a copper washer behind it to allow for clearance. The motor can be finely adjusted fore and aft to allow for this and make sure that both pulleys are aligned and running parallel.
The new belt was notched but this doesn’t seem to matter to, or affect the mixer’s operation, in subsequent use.
Step 3: Paint, Rebuild
Adjust the gearbox so that the drum spigot is central to the arm aperture and also extends far enough into the pulley housing, and is central to the aperture and also extends far enough into the pulley housing.
The locating lugs are slotted to allow for fine adjustment, left right in or out. There is a through hole at the end of the pulley shaft to allow it to be held whilst tightening or releasing the pulley bolt. I noticed that this bolt had been retained with a thread locking paste, so I applied some to the cleaned bolt when re connecting the pulley to the gearbox shaft.
The front foot was full of earth and old concrete so I cleaned it all out and hammered in an interference fit piece of hardwood. This makes the mixer more stable and it doesn’t screech when moved on a hard surface.
I cleaned all the old drive belt dust, grease and dust off with paraffin (kerosene) and an old paint brush. The paint used to treat the ground off surfaces was red oxide primer, which replaces the excellent but toxic red lead, used for years on exposed steel.
When first dismantling the part of the mixer two old bathmats made really good absorbent work surfaces. Keep folding them up and transferring all the filth to the bin to minimise fouling up the full work area.
The motor cant be removed until the drive belt is removed from the motor pulley. This in turn cant be removed until the gearbox drive pulley is detached from the gearbox shaft.
During the rebuild I greased the bearing surfaces that the drum beam rotates in. the wheel gearbox also needs re-packing with grease. During dismantling be careful as the wheel gear case is not retained mechanically and will just fall off once the drum beam is detached.
Step 4: Enhancements
After I had rebuilt the mixer I modified it by adding a NVR safety switch to the external motor housing. This saves having to open the housing to turn it on or off. Also the new switch will default to off if the power is stopped remotely. (NVR = No Volt Release)
I also terminated the supply cable to the motor case externally and added a cable hook to stow the cable when not in use.
Another modification was to add some UPVC section to the back of the drum beam. This should stop future water and cement settling under the gearbox mechanism causing rust and corrosion