Mixing bushings and bearings?

[Pseudotectonic]

4 hours ago, Sewdhull said:

 

Only the bevel end of the Bevel gear bearings experience axial force, the bearings at the bevel end get an upwards radial force (1N) the other end a downwards radial force (3N). The axial force would be 2N on the bevel end.

 

How did you calculate the 3N on the other side? And the 2N axial force?

[Sewdhull]

For a bevel gear the axial force is around double the radial force, which I took as 1N so axial force is 2.

The calculations are done on the linked gear page.

The 3N is derived from the interaction of the Middle gear and Bevel gear 3 to 1 ratio multiplying the tangential forces and proportionately increasing the radial force.

 

It should be noted that gear tooth geometry affects the forces, the pressure angle in particular, but a little research indicates that the numbers on the linked page are typical.

Edited December 27, 2023 by Sewdhull
Changed axial to radial

[Pseudotectonic]

It seems your forces are going "one way" from the motor, what about the spring load coming back, does it apply any load on the bevel gear and does it modify the radial load directions?

 

For sake of my understanding do you mind drawing some arrows on this diagram?

 

[Sewdhull]

what forces do you want on there, parts are missing...is it the forces on each bearing you are after?

[Pseudotectonic]

Yes exactly, radial and axial forces please (some vector arrows will do)

 

Although I imagine in reality it is in all directions because of vibrations and airsoft physics and whatnot

[Sewdhull]

The forces get resolved for each gear and they originate at the motor.

 

Forces balance, the tangential forces that spin the gears only do so because there's more motor force than needed to compress the spring. The axial and radial forces balance at each bearing.

 

The forces originate at the motor pinion and build depending on the load the gears eventually connect to. The gear teeth meet at an angle which produces the radial and axial forces dependant on the gear types and gear shape.

 

 

[Sewdhull]

I think that's right altho i am just starting my 5th night shift. Remember these are not forces of the gears pushing against each other, they dont as they at times not in contact with each other. The forces are created when the gear teeth mesh at an angle and push at an angle creating forces in 2 or 3 directions.

The down arrow for the Middle gear i wrong, it should be up.

Edited December 27, 2023 by Sewdhull

[Rogerborg]

If you want to feel that you've maximised reliability in your overpriced fragile toy that will fail in 9 other ways anyway if you actually play with it, use bushings.

 

If you want to feel that you've achieved that last 0.1% of performance in your overpriced fragile toy that you'll never objectively measure, use bearings.

 

 

 

[Sewdhull]

I suppose it's worth saying that bushings would end up wearing the same place making lubrication tricky and that bearings would see a load biased to one place but because the balls spread the load over an area it outer race would wear in a similar place to a bushing but the lubrication would still spread.

[Leo Greer]

I should mention, never trust Evike! That place is a well of horrible information. They still recommend putting silicone oil in your green gas/propane.