Bearing selection confirmation

[Kenneth]

Hey guys,

Noob question coming right up! I just want to confirm my bearing selection.

I will be going with 2 Tapered Roller's per upright. After some amateur calculations (LLT, I've followed Miliken Race vehicle dynamics) I am getting a number around the 4700N range. Out back we are going with an integrated tripod housing & hub design. As a result, the bore of the bearing is around 65 mm. I'm looking at the charts and it looks like the tapered rollers with a bore of 65 will be able to handle that and more. The fatigue limit is 16.3 kN and it definitely seems like we will not get anywhere close to that.

So I guess my question is, is overkill okay for the sake of packaging(especially for the rears)? The fronts can be sized correctly. And since we're on the topic for sizing bearings, what I need to know (From what I've read) is what type of load it will be seeing and the expected run life of the bearing. Am I correct there? I've looked around and it seems like 100 hours is plenty.

Any help would be awesome! Thanks!!

[Kenneth]

Hey guys,

Noob question coming right up! I just want to confirm my bearing selection.

I will be going with 2 Tapered Roller's per upright. After some amateur calculations (LLT, I've followed Miliken Race vehicle dynamics) I am getting a number around the 4700N range. Out back we are going with an integrated tripod housing & hub design. As a result, the bore of the bearing is around 65 mm. I'm looking at the charts and it looks like the tapered rollers with a bore of 65 will be able to handle that and more. The fatigue limit is 16.3 kN and it definitely seems like we will not get anywhere close to that.

So I guess my question is, is overkill okay for the sake of packaging(especially for the rears)? The fronts can be sized correctly. And since we're on the topic for sizing bearings, what I need to know (From what I've read) is what type of load it will be seeing and the expected run life of the bearing. Am I correct there? I've looked around and it seems like 100 hours is plenty.

Any help would be awesome! Thanks!!

[Tim.Wright]

Could be overkill, Ive had tapered rollers smaller than that on a road car.

But if your restricted to a minimum 65mm ID, then maybe you could move to a thin section angular contact ball bearing. I know of SKF and Kaydon who do them but Im sure there are others.

Tim

[swong46]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Timo:
Could be overkill, Ive had tapered rollers smaller than that on a road car.

But if your restricted to a minimum 65mm ID, then maybe you could move to a thin section angular contact ball bearing. I know of SKF and Kaydon who do them but Im sure there are others.

Tim </div></BLOCKQUOTE>

Those thin angular ball bearings are really ideal, they cost a lot though =[

[Kenneth]

Ah thanks for the information guys! Being a first year team, we don't really have the big guys sponsoring us. We're lucky enough to find a local mom and pops type tool supply store that would take the tab on the bearings (and quite possibly the rod ends :O) so I don't want to scare em off for next year and go all out with these thin section angulars. Oh well! Something to write about in the design report, and knowledge for next year!

[Mike Cook]

Kenneth,

Thanks for the intelligent post first off. Second, I have seen the same problem you are running into, and it seems like for the weight, you can get away with a deep groove ball bearing setup. In general I think tapered rollers are much better, but when you have a very large ID to work around, the tapered rollers get too heavy.

With that said, for a team just starting out a tapered bearing will work fine, even if a little heavy. It will give the guys next year something to work on!

Goodluck.

[Kenneth]

Thank you sir!

The wheel assembly out back is done, and everything minus the tyre and air is included. We're looking at a weight of 13.5 pounds (6.1kg). Assuming the mass entries are correct, thats not too bad! I'm guessing with the tyre and air, I'll get close to my 20 pound target per corner (not sure if thats reasonable or not).

[Luniz]

We've been designing an Upright resulting in a similar situation for the last two years. For cost reasons we went with thin deep groove ball bearings instead of angular ones, and we never had any trouble with them. On the older car of the two, they now slowly begin to show some wear, but the car has been driven for at least 2500km by now.

[Mike Cook]

LOL, I don't think the word cheap should ever be included with 'thin deep groove ball bearing'. Most the time they are well over 200$ a bearing. Completely inappropriate for a FSAE car. But that's just my opinion.

[Luniz]

Well, ours were about 50€ each, we didn't get any discount on them and they were SKF. Since you need 8 of them it sums up to be quite some money, but still far away from those 200US$