Upright Bearings

[Ajinkya]

Hi all,
I want to use 2 ACBB in rear wheel assembly. I am thinking of using 2 Angular contact bearings of ID 60 mm and OD 85 mm in Tandem arrangement since I am having radial load on each bearing 1500 N and Wheel will have 2500 N axial load (Assuming Lateral Force will act in both directions during different Steering conditions). I want to Preload these both bearings by introducing Spacer ring (Which will be part of Aluminium upright itself). How should I decide the width and Inner diameter of this Spacer ring?
Should I just apply Preload force on spacer ring surface to check shear stresses or is there any other method to find the width ?
Thanks in advance

[Francis Gagné]

Where do you source your bearings? The dimension you gave shows a very low profile bearing ACBB. Those bearing are usually precision bearing for machinery and often very expensive (500$+ more per bearing!). Sometime they are referred as to spindle bearings.

61912, which is standard size have the same dimensions (not knowing your width) and can take up some axial load. It may, or may not fit your design, it is up to you to validate but they are much more economic.

The Schaeffler website has a pretty good design guide for everything bearing related. You will find info about axial load rating, housing dimensions and tolerances, life estimation, etc. The info there should be compatible with any other major bearing manufacturer.

http://medias.ina.de/medias//hp?lang=en

[Ajinkya]

Hi Francis ,
Thanks for your reply
I am using SKF's 71912 bearings (http://tinyurl.com/cr6tzrg) in rear wheels .
The reason why I choose them is they are light weight and will work fine in my car. As I am getting Static bearing load 5.5 kN and Dynamic bearing load 11.7 kN . The another reason of choosing them is I have very less space inside the wheel So I think this is best bearing with less cross section and Good load rating values What do you think ?
Which Bearings you are using and why ?

[Francis Gagné]

I've looked into those bearings and they indeed are very-high precicision bearings for spindles.

They are very good and would probably fit the application and are indeed light, but they are also much much more than what you need. The price I found where in the area of 275€ PER BEARING. If there is one thing one your car that you should be able to keep spares is wheel bearings and rod-ends (For suspension that is...) Anything can happen and they tend to develop play with time.

Limiting speeds are are an order of magnitude higher of what you need. They also need very machining of the housing and shaft to work properly. Manufacturers are not very keen on giving these away unless you have an application that absolutely require them, which is not the case.

The rear bearings we used were double row ball bearings that comes from an ATV, easy to find and cheap enough we don't mind replacing them when they get worn out. When properly preloaded they have no play and an ok stiffness. In the front we run two standard taper roller bearings per wheel. We make sure that the wheel center is as close as possible of the bearing center to reduce the moment arm from vertical forces. With a dual bearing setup you can try to maximize the spacing to reduce the apparent load on the bearing.

[Z]

Originally posted by Ajinkya:
I am using SKF's 71912 bearings (http://tinyurl.com/cr6tzrg)
... What do you think ?
Ajinkya,

Your choice of bearings is bad (too many rupees for a start).

Also, in FSAE Static load equals worst Dynamic load (locked wheel hits pothole -> bearing starts whining). And heaviest loading is inwards-lateral at the wheelprint, so spacing them equally either side of wheel centreplane is not the best solution (better if they are wide apart, but somewhat inboard).

Finally, I have seen very few well designed FSAE wheel bearing assemblies (ie. student design that barely lasts one season). I suggest you talk to a "Technical Representative" from one of the bearing suppliers. This might mean you have to phone overseas, which should not be a problem given that your countrymen phone me at least once a day trying to sell me something!

Z

[EPMPaul]

Another possible worst load case might also be when you (over)preload your bearings so you might want to be careful about that. We run 61913 (http://www.vxb.com/page/bearings/PROD/Kit8739_1) bearings and doing the calcs, it came out to a life of around 1700 km based on some lapsim estimates of how much time you spend on each loadcase. I could have run a size smaller but just wanted a bit of free play on static loading to account for the tiny bit of preload we're going to apply an any weid bump I would hit (over 3G). Never got around to really checking stiffness(will probably be my downfall in design). They're most probably overkill a little bit but we haven't gotten around to designing a wheel package in a couple years so we took it easy a lil bit. Also, keep in mind how you're gonna assemble these things. Representatives sometimes assume that you have access to an induction heater and the whole setup so keep in mind that you have to assemble these and most teams don't have access to the facilities in house to do so. This might be a problem in a pinch.

[Ajinkya]

Thanks a lot Guys .
I missed that point "Cost" in my decision.(My bad http://fsae.com/groupee_common/emoticons/icon_frown.gif ) I will search more for a Bearing which will be in the Budget . http://fsae.com/groupee_common/emoticons/icon_wink.gif

[idontcare]

hello everyone,
Last year i used double row angular contact ball bearing,
(BAH-0013D link: http://www.noc.ua/en/online-catalog-bearings/232-itemdescription-BAH-0013+D.html?bearing=07336d64436f5f7c4365&title=BAH-0013D )
and we faced problems with the preload which led to play in the bearing.
i want to go for single row deep groove ball bearings this time. So, am i likely to face the same problem again if correct pre axial load is not given?

[MCoach]

If you want to use angular contact ball bearings (ACBB) then you must, must, must pay attention to proper preload and tolerances. Yes, the assembly can be stiffer than deep groove ball bearings (DGBB) but if you get sloppy with your work, then they will, for all intents and purposes, explode. Preload to the hub/upright must follow the manufacture's specs. Light grease or heavy oil is recommended. If you don't use an accurate, ground bearing spacer, then you may as well not use one at all, it's going to explode eventually anyways. Proper axial preload is also important for them to not eat themselves. I think I've blown up a single wheel bearing so far due an assembly tolerance that was a bit out of spec.

When using these bearings for wheel bearings I chose to use a preload nut, and once preload was reached on each wheel, then I would drill a small hole in each to secure the nut in place. This in contrast to having the hub and nut drilled with several holes and just lining up to the nearest one. They are finicky little bearings...

Just my 2 1/2 cents.

[Kevin Hayward]

Ajinkya,


Hi all,
I want to use 2 ACBB in rear wheel assembly. I am thinking of using 2 Angular contact bearings of ID 60 mm and OD 85 mm in Tandem arrangement since I am having radial load on each bearing 1500 N and Wheel will have 2500 N axial load (Assuming Lateral Force will act in both directions during different Steering conditions).


I assume you have made a mistake in your radial load calculation. Remember that the axial load is applied at the base of the tyre not at the centre-line of the bearing assembly.

Kev