Bearing Type

[bsia5466]

Hi,

I'm new to bearing use and I'm trying to decide on a type of bearing for my application. I have an actuator shaft that will be moving down axially and slightly rotating (plus/minus 5-10 degrees). I want to measure the linear displacement of the shaft and therefore am trying to make use of a bearing system to isolate the linear motion from the rotary. I have been thinking about using a rotary ball bearing fixed to the shaft on the inner race such that it rotates and translates with the actuator shaft. The outer race will therefore only move linearly, and from this I will measure the linear motion using an encoder. Furthermore, I'm looking for something as small and light as possible to reduce weight impact on the actuator.

I understand this design may be a bit crude and so i was wondering if any suggestions on bearing design/choice to capture the linear motion from a translating and rotating shaft?

Any help would be much appreciated.

 

[Compositepro]

Dial indicators are often used for this type of measurement without the need for any bearing except the ball tip of the probe. Use an lvdt if you want an electronic signal output.

 

[bsia5466]

The problem with using a dial gauge in that fashion is it would have to be aligned directly in line with the linear axis of motion, which is undesirable as that is where my test material will be. I'm not 100% if I've understood you completely so if I am mistaken please could you explain further?

 

[Compositepro]

The key to success is using your imagination in how to make things work rather than in why things won't work. Experience does help a lot in that respect. But only you know what you are trying to do. Any surface on the shaft that is perpendicular to the axis can be used for measurement. Many dial indicators measure "wiggle" of the tip rather than "plunger" motion.

https://www.google.com/search?q=dia...i6ksYCFcSAkgodjc4FUA&biw=1429&bih=747&dpr=0.9

 

[TurbMaintEng]

Try using an RVDT (tap the end of the shaft, mount the RVDT to the end. It measures rotational motion. very accurate.

 

[Tmoose]

Got a sketch?
How are you moving the shaft axially?