# Simple project - mechanics

Hi!
Firstly, sorry for bad English, it's not my first language :)
I don't have experience in mechanical engineering so I came here to ask for help. Here is sketch of one simple construction I want to realize:

Here we have 5 cm thick plate (it would be wooden), 50cm long and 35cm wide. There will be hole drilled in plate for shaft (it will be long 40cm - 50cm) . There would be some gear on shaft and DC motor to rotate shaft. My question is, how can I "fix" gear shaft to carry load without falling down? Here is one shaft I found on google http://cdn3.volusion.com/vyfsn.knvgw/v/vspfiles/photos/am-2392-2.jpg?1420269442
I don't see way how can one use it in this situation. How can one mount gear on this shaft?

## Answers and Replies

Mounting of gear depends on if gear has a key way, right? But what to do to keep shaft from falling down? I know that easiest way would be to weld gear to shaft, but I want some solution which wouldn't involve welding :)

Can you provide more information on the method used to hold the shaft vertical? Is the gear at the top of the shaft? You'll likely need a key, but depending on the situation, collars could be used on both sides of the gear, the gear could be pinned, the gear could be pressed on, the gear could be supported by the drive mechanism [such as two plates sandwiching the drive gears] and drive via a key on the shaft. There are plenty of options, but you'll have to figure out what works for your application. HTH

etf
hey etf. to start, there are a few unstated dimensions and motions.
im presuming the shaft is approx10cm in diameter, and the shaft is connected solid to gear. and will be operated in the shaft vertical posisition
there are four main ways to connect shaft to gear, 1 weld. 2 keyway, 3 interference fit, 4 bolted through.

a thrust bearing mounted to the timber and washer mounted to the shaft would prevent the shaft from falling through the hole

etf
OldEngr63
Gold Member
It is generally not a good idea to even think of welding a gear to a shaft. This is likely to warp the shaft and/or damage the gear. Also, how would you then replace a worn gear?

Gears are usually mounted with keys, or press fits. Since the support bracket is wooden, that suggests that the loads are not too high so either should work satisfactorily.

etf
Buy the gear one with a collar. Use grub screw or a through bolt with thread tapping in the shaft, to secure the gear from falling. Other than welding, this system will have a replaceable gear.

etf