Idler Gear bearing selection

[mrpi]

Hello,

Im designing a motor/gearbox that mounts to a (customer-supplied) linear actuator via a gear train.

Design Background:
Basically my gearbox has a pinion gear mounted to the output shaft, and in order to interface with the linear actuator, we include an idler gear (they call it a "cross-over" gear) that sticks part-way out of the housing. You bolt the housing onto the side of the linear actuator, and the protruding idler gear meshes to a driven gear on the linear actuator.
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Question:
To support this idler gear, I currently have a fixed shaft in the housing. The idler gear is bored to accept a double row ball bearing that we have been heat-shrink fitting into the gear.

Backlash in the gear train is not critical. In fact, we have worked with the gear manufacturer and our customer to provide gears with additional clearance (to allow for tolerance stack-up, thermal expansion, etc).

This is where I am uncertain.

Is this an appropriate type of mounting for the idler gear??? (double row bearing turning about a fixed shaft)

I chose it because of size constraints in that area of the design (because the idler gear sticks out the side of the unit, there isnt enough radial room to fit bearings into the housing).

I see there are multiple styles of double-row ball bearings; angular contact, self aligning, etc.

We have built several prototypes using this gear mounting method, and they have functioned properly during initial testing. I have the opportunity to re-design the system and this was an area I was questioning myself on in regards to long-term reliability.

Suggestions or comments are appreciated.

Thanks.



Beat to fit, paint to match.

 

[tbuelna]

mrpi,

Your idler gear bearing configuration is used commonly with idler gears. If you have spur gears, and the driving and driven gears are diametrically opposed about the idler, then the idler bearing loads may be quite small.

Based on your description, it sounds like your driving and driven gears might have some axial offset. If so, there may be some moment acting on the idler's ball bearing set, and this moment load should be considered in your bearing life analysis.

Hope that helps.
Terry

 

[mrpi]

Thanks for the quick reply Terry,

Sorry I wasn't clear, yes they're straight spur gears.

The entire gear train is "in a row" so there is no offset between the gears.

Sounds like I'll continue with the design.

Thanks again.

=stan

Beat to fit, paint to match.