Bearing arrangement - comments please
Bearing arrangement - comments please
(OP)
I'm designing a small wind turbine drivetrain that is handling significant axial load in 1 direction (Fa >> Fr) and a very small radial load on both bearings.
1. Locating / non locating bearing arrangement. Is it possible to use a spherical roller bearing for the locating bearing and a radial insert ball bearing for the other, like this??
Or are we limited to the examples like in the guides from FAG & SKF?

2. Tapred bore with adapter sleeve, lock nut and locating ring + stepped shaft - can they accommodate significant axial loads? I've rlooked at the SKF, FAG and Timken design guides, but they don't mention anything on this.
2. Locating bearing housings: Is it possible to use plummer block units instead of flanged housings to house the locating bearing? If I use plummer block housings, the thrust forces will create moment on the 2 bolts fastening the plummer block housing down (4 bolt ones not available for the size I'm using). Welding the block down would risk misalignment.
I've tried googling (can't find) and tried calling Timken, Schaeffler, Koyo and SKF in my country to get help from their application engineers, but I keep on getting redirected to sales all the time.
Thank you!
1. Locating / non locating bearing arrangement. Is it possible to use a spherical roller bearing for the locating bearing and a radial insert ball bearing for the other, like this??
Or are we limited to the examples like in the guides from FAG & SKF?

2. Tapred bore with adapter sleeve, lock nut and locating ring + stepped shaft - can they accommodate significant axial loads? I've rlooked at the SKF, FAG and Timken design guides, but they don't mention anything on this.
2. Locating bearing housings: Is it possible to use plummer block units instead of flanged housings to house the locating bearing? If I use plummer block housings, the thrust forces will create moment on the 2 bolts fastening the plummer block housing down (4 bolt ones not available for the size I'm using). Welding the block down would risk misalignment.
I've tried googling (can't find) and tried calling Timken, Schaeffler, Koyo and SKF in my country to get help from their application engineers, but I keep on getting redirected to sales all the time.
Thank you!





RE: Bearing arrangement - comments please
What are the sizes that you're looking at? You mention that as a limiting factor but don't tell us what it is...
Aidan McAllister
Metallurgical Engineer
RE: Bearing arrangement - comments please
I considered using thrust bearings, but due to small shaft size (25mm metric dia) thrust bearings e.g. thrust spherical roller, thrust taper roller etc are not manufactured in this size; or require a 3-4 months of lead time for product to reach my country.
I chose spherical roller bearings because it can tolerate misalignment and has the highest Cr and Cor (intermittent rotation) compared to thrust ball bearings and double row angular contact bearings.
RE: Bearing arrangement - comments please
What is the value of the "significant" axial load ?
And operating rpm?
RE: Bearing arrangement - comments please
The significant axial load is about 14kN. Operating rpm fluctuates since its a wind turbine, but max operating rpm should be 500rpm.
RE: Bearing arrangement - comments please
Do you custom fabricate these housings?
Or do you know where to find them off the shelf? As much as possible, I'd like to avoid custom fabrication, due to the cost and time involved.
Thanks!
RE: Bearing arrangement - comments please
RE: Bearing arrangement - comments please
Your arrangement looks to me to be optimal for radial force, with some capability to manage axial force.
Look up spindle bearings. There is a series of angular contact bearings out there that are manufactured very accurately such that they pre-load when they are assembled face to face. That alone may be enough to hold your turbine. Aside from cost, there is no harm in keeping your deep groove bearing.
--
JHG
RE: Bearing arrangement - comments please
25mm is not very small. There are many thrust bearing options, like: 30205 , 31305, 51105, 51305
Just curious, where are you located?
Can you provide shaft length?
RE: Bearing arrangement - comments please
http://www.skf.com/us/products/bearings-units-hous...
RE: Bearing arrangement - comments please
@drawoh "optimised for radial force" - That's a big problem. This being a model wind turbine the axial force is way higher than the radial force. I may not even have enough radial force for preloading the non-locating bearing.
@lukin1977 - I'm in Singapore. I have multiple authorised distributors in my city, so I have the quoted prices of these bearings. The total shaft length is about 100-150mm (design not frozen yet).
The problem is finding suitable housings for locating double row tapered roller bearings. The distributors all have housings for spherical roller bearings and radial insert bearings, but none for taper roller bearings or cylindrical roller bearings. They asked me to custom fabricate, which I'd only do if I had no choice.
@BrianE22 - Yes, pretty much all reputable vendors offer calculation data for calculating the equivalent axial to radial load. In fact, I built my own equivalent load calculator so calculations are no problem for me. Getting suitable housings is the problem now.
RE: Bearing arrangement - comments please
Your example looks a little odd for a thrust-heavy application.
Why would you _not_ exploit the bearing manufacturers' accumulated experience in the form of guides?
How did you manage to get yourself locked into a 25mm straight shaft at this early stage?
Have you looked at the preassembled factory-set cartridge bearing assemblies now common on automobile front wheels?
Your example appears to show a pair of gears between the bearings, yet you state minimal radial loads. Are gears, and associated separating forces, present, or not?
Mike Halloran
Pembroke Pines, FL, USA
RE: Bearing arrangement - comments please
At that size it should not be very difficult nor time demanding to fabricate
RE: Bearing arrangement - comments please
The diagram is misleading - it's a direct drive system, no gears and whatnot.
I almost managed to find 35mm Timken tapered roller bearing housed units, but too bad, they don't stock them in Singapore. Gave up, am now custom making my own housings.
RE: Bearing arrangement - comments please
In my case, we switched from the spherical roller to a deep groove ball bearing with C3/C4 clearance (an angular contact ball will work too) since there is only one set of rolling elements and they all get a share of the load. The extra clearance shifts the load path angle to make the contact more "angular". While deep groove ball bearings are usually seen as "radial" bearings, they can perform very well with mostly axial load under appropriate circumstances.
RE: Bearing arrangement - comments please
While I roundly trust bearing manufacturers, they each have their biases. SKF for example invented the spherical roller bearing, so they will tend to push spherical roller bearings. Timken invented the taper roller bearing, so of course they push those.