Rocker Pivot Bearings

[Mark Bacchetti]

The wheel bearing topic has inspired me to start a parallel post http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

Anyone care to comment on rocker pivot bearings?

-Mark
Cal Poly Pomona

[Denny Trimble]

We've used a pair of R6 sealed deep groove cartridge bearings, with a double-shear chassis mount, for the last several years with good results. Zero maintenance issues, very simple to install.

[fsae racer]

we spoke with a few c,d sports racers car manufacturers who have recommended standard tapered roller/wheel bearings over nadella bearings (which can be found in the pegasus racing catalogue) for frictional reasons if your rocker is in single shear. we have gone with exatly that with no problems. We tried using a pair of roller bearings, but found that certainly become notchy with extended use. I would personally stay away from any type ball bearings for rocker aplications.

[jack]

I would personally stay away from any type ball bearings for rocker aplications.

yeah, thats what i have heard too. ball bearings will wear out really quick because of the slight amounts of movement.

[Denny Trimble]

Well, our cars get more hours on them than most FSAE cars. No problems yet, 150+ hours on the 2003 car, and probably 100 on the 2004 car.

And, they're $5 each to replace. Not an issue in my opinion.

[Mark Bacchetti]

I was recently at a open house for Swift Engineering, manufacturer of the Toyota Atlantic .014a. They had installation handbooks for the car out on a table. From the drawings, it looks like they were using two ball bearings for the rocker pivot. Has anyone worked on the 014a and can vouch for this? I figure they would be using some type of needle roller bearing like Nadella's in Pegasus.

We also use deep groove ball bearings for the rockers without any problem. I checked out Pegasus and found some wheel bearings. They seem a bit large though (ID >1.5"). Are there smaller ones in the catalog?

-Mark
Cal Poly Pomona

[D J Yates]

This is a conviniently timed thread. I just happend to be designing the bellcranks today.

What kind of radial loads are you designing for. 6kN max sound about right? The only time the bearing would see a static radial load is at full suspension travel - something i don't want to happen, but if it does, i'd like for it not to destroy the bearings - which is when the radial loads would be greatest.

For those of you using ball bearings, 2x single row or 1x double? I was thinking of something similar to the following. http://medias.uk.ina.com/medias/en!hp.ec.br.pr/42*4201;a3Z5TZsfZe26
I've no idea how much these will cost, but i know they'll be more than the plain bearing solution we used on our first car.

[Mark Bacchetti]

Cornell has an SAE paper that discusses implementation of a strain gauge on their pullrod. I remember reading that their maximum loads were around 1000 lbf (~4.4kN). (I can't find the paper at work but I remember it being around that number).

One of our older cars had ball bearings rated for 173lbf (~0.77kN). After 3 months we checked the bearings and they were goners.

This is what we used last year for design. I'm working on ADAMS/Car and some hand calcs to get a better idea on the loading conditions for the next design.

-Mark
Cal Poly Pomona

[D J Yates]

4.4kN is very close to what i calculated for the pushrod, and combined with the force from the spring damper giving the radial load of 6kN. I'm confident in my method of calculating forces throughout the suspension, but the problem is knowing what forces occur at the wheel during bumps etc. I suppose the only way is to use strain guages to measure the forces, but apparently that's easier said than done.

Back to bearings.

For inboard bellcranks that are covered by bodywork, do the bearings need to be sealed?

Now i'm looking at needle roller angular bearings. Funny how my designs always seem to end up getting more complicated.

[fade]

http://fsae.com/groupee_common/emoticons/icon_smile.gifwhats the old saying "add weight and complicate". im also uning a deeep grove for our rocker pivots. For those who have used this setup with the spindle mount single shear who have experienced failures under normal conditions did you use a preload spacer between the bearings?

[Dan B]

I like the Nadella (http://www.pegasusautoracing.com/ProductSelection.asp?Product=3080) bearings but they arn't cheep.
http://www.pegasusautoracing.com/Images/L/3080.JPG

I bet if you played your cards right you could piece together the right needle (or roller) bearing and thrust bearing for less.

My thought is that a combination of a needle bearing and a ball bearing would be a good way to go.

[D J Yates]

I was advised away from needle bearings by a tutor because apperently, they don't like resisting moments. I eventually setteld on a double row deep grove ball bearing. It has an advantage over single row bearings because you only need one of them and therefore require no spacers, and is also more than twice the strength of an equivelent size single row.

[SD]

We've been using INA # NKIB 5901 for a couple years now - no problems!

They are a combination needle roller and angular ball bearing.

[IsheeM]

I am currently exploring the option of running an oil impregnated bronze bushing. Do you guys have any experience with bushings or does most everyone run bearings?

Thanks,

[Timmay!]

We used the oil impregnated bronze bushings in our 04 car.... still have yet to have any trouble with them, and they are 1/4" ID's

we've ran our car at nearly all the local auto-x's too.... so, theres plenty of time on them

[D J Yates]

We used bronze bushings on our first car (last year). At the front, we had pullrods, dampers and bell cranks all in the same plane with dampers under the drivers legs - only possible because our car was huge. The bronze bushings were a little stiff but worked fine because they only saw radial loads. The car hasn't had many miles on it but the bushings are still quite worn. They'll easilly last through a competition weekend but as for a full year with testing etc, they might need replacing.

However, at the back, the pullrods were dampers and pullrods were severly out of plane (my fault for rushing the design - litterally a week before competition) putting the bellcrank into bending and putting all sorts of loads through the bushings causing them to sieze up regularly. This year i've gone for bearings because i don't want to risk any siezing even though the axial loads will be far less. I'm just not taking any chances.

If your confident in your overall design and will have the time to test them thoroughly, then i couldn't see a problem with the bushings. Just make sure you have another solution to fall back on in case they don't work.


We've been using INA # NKIB 5901 for a couple years now - no problems!

They were the bearings i was looking at until my tutor pointed out that to resit the moment produced by the pushrod, it would be the edges of the rollers which would be taking the loads. Which way do you orientate the bearings (ball at top or bottom)? How much do they cost? They look quite specialised so i expect they're quite expensive.

[Omer]

hi
maybe it's too obvious to see but i can't understand how this particular rocker mechanisem works.
using soildworks building the assembly of the mechanism shows that if the rocker pivot and the pivot of the chassis/shock are not parallel nothing will move,but here it seems they are not parralel,can someone pls tell me what i'm missing.

http://engsoc.queensu.ca/formulacar/gallery/album21/IMG_0061

[Omer]

Reply

Reply
for some reason it didn't loaded the picture fo here it is.
http://engsoc.queensu.ca/formulacar/gallery/album21/IMG_0061

[TG]

Originally posted by Omer:
hi
maybe it's too obvious to see but i can't understand how this particular rocker mechanisem works.
using soildworks building the assembly of the mechanism shows that if the rocker pivot and the pivot of the chassis/shock are not parallel nothing will move,but here it seems they are not parralel,can someone pls tell me what i'm missing.

http://engsoc.queensu.ca/formulacar/gallery/album21/IMG_0061

The damper has a spherical bearing in it so it has 5 degrees of freedom to it.

[Omer]

thanks
thats expalins it,we have fox shocks without those bearings.

from the pictures you cant see the bearing.

[Kurt Bilinski]

I used spherical bearings on a stainless shaft, cheap and easy to source. This is on a mid-engine Mini, not an FSAE car, hence the... massiveness of it all.

http://www.kimini.com/Diaries/2004Winter/front%20right%20suspension%20in.JPG

[Omer]

hi
we got vanilla R shocks by fox(without the gas container) and without spherical bearing at the end,where it attached to the frame.
can we buy this specific spherical bearing and assembel it inside the shock?