Mixer

[Marvo]

Has anyone ever stripped a planetary type mixer before. I bought a cheap 2nd hand one on gumtree this afternoon that's has a 3-speed gearbox and 1 of the speeds isn't working. I've never touched one of these things before and just wondered if anyone might work on this type of equipment and have any wisdom they could share before I dive in.

It's an old Hobart and looks like this

 

[Richard Burns]

It probably has a mechanical rather than electrical gear box so take lots of photos as you disassemble, other than that I have no ideas!

 

[telectrix]

missionary mince for christmas? :17:

 

[snowhead]

I used to repair these a while ago.
Never had any problems with the gears so haven't stripped one down.

Most likely a selector problem.

Will look like one of these inside, may not be exact model;
https://my.hobartcorp.com/resourcecenter/ProductDocumentation/F16968 (9-88).pdf

 

[Marvo]

Well I got around to stripping it earlier this evening, it was pretty straight forward and it's an all mechanical gearbox with a manual selector for the 3 speeds. It took longer to mop up the large amount of grease from the internals than it did to actually dismantle it.

One of the shafts is snapped clean in half but it's not a plain shaft, it has a 13 tooth machined cog on one end of it which is part of the shaft. The rest of the gearbox is in pretty good condition for its age and it's well manufactured. The shaft in question is hardened to at least 60 or 70 Rockwell so it's going to be a pain to remake it. I'd can machine a new shaft at 10 thousandths oversize and then I'd have send it for hardening and final grinding because I don't have the machinery to do this in my workshop. Also cutting the cog on my milling machine is a bit hit and miss, I have a dividing head but not the gear face cutters for the mill so I'm probably going to have to but a new part from an agent and import by courier.

I'll look at it again tomorrow when I've got more time, I might run one off in mild steel for a temporary fix and just mix small batches and hope for the best.

 

[Richard Burns]

I would be attempting to weld it back together, grind smooth and case harden it, but I do not have access to machine tools; my lathe is buried under tons of other stuff!

 

[Marvo]

I'm not sure if welding would be possible although the thought also struck my mind. It might be worth running it past a specialist welder for an opinion on whether it's an option, we don't have the capability to do welding to the kind of standard required. It's a small gearbox but I can imagine the forces involved internally would be enormous with the gear ratios that are employed.

 

[telectrix]

I'm not sure if welding would be possible although the thought also struck my mind. It might be worth running it past a specialist welder for an opinion on whether it's an option, we don't have the capability to do welding to the kind of standard required. It's a small gearbox but I can imagine the forces involved internally would be enormous with the gear ratios that are employed.

sounds like a plan.

 

[Marvo]

Well the mixer is up and running as of about 10 minutes ago so pizzas for dinner tonight

I tracked down a parts supplier that was about an hours drive away. They had the shaft on the shelf and sent my a photo by email to confirm it was the correct part. It was covered in surface rust and the guy told me it had been on the shelf for 18 years. He quoted me ZAR800 (about 35 quid) which is extremely cheap. I was budgeting on around ZAR3000 for fabrication, hardening and grinding of a new one so I can only assume he was quoting a price that was also 18 years old.

20 minutes on the lathe and the shaft looked like brand new, 2 hours of reassembly, an enormous quantity of grease and a few attempts at getting the selector fork realigned as the shafts were refitted and job's done, I now have a 3 speed dough mixer, total cost under 50 quid.

 

[UNG]

Well the mixer is up and running as of about 10 minutes ago so pizzas for dinner tonight

I tracked down a parts supplier that was about an hours drive away. They had the shaft on the shelf and sent my a photo by email to confirm it was the correct part. It was covered in surface rust and the guy told me it had been on the shelf for 18 years. He quoted me ZAR800 (about 35 quid) which is extremely cheap. I was budgeting on around ZAR3000 for fabrication, hardening and grinding of a new one so I can only assume he was quoting a price that was also 18 years old.

20 minutes on the lathe and the shaft looked like brand new, 2 hours of reassembly, an enormous quantity of grease and a few attempts at getting the selector fork realigned as the shafts were refitted and job's done, I now have a 3 speed dough mixer, total cost under 50 quid.

Hope you used food safe grease

 

[Marvo]

Errrrm nah. The only grease I had in decent quantities was 100 litres of high speed high temp bearing grease I procured from my company workshop, probably not the best for a low speed high torque gearbox but the gearbox is sealed so it shouldn't get anywhere near the food....hopefully.