Bellcrank bearing type to use?

[V12]

I am designing and ultimately building an inboard shock/spring type suspension and am having trouble deciding on what type of bearing to use for the bellcrank pivot. Does anyone out there have experience with these and know what works and doesn't. I have looked at needle, sleeve, ball, tapered. I am leaning towards the teflon coated ball type used on shock ends because it allows for misalignment and can handle high loads.
Advice please.
Thanks

Pushrod suspension:
This is the type used in open wheel race cars where a connecting rod is attached to the lower control arm. This rod is connected to a bellcrank which is connected to the shock/spring assembly.

 

[RaceEngJr]

We've run mainly deep groove ball bearings and recently we have tried needle rollers for an inboard bellcrank assembly in a small racecar, both work. We used these types because they only allow rotation in one plane.

Not exacly sure how this bellcrank will work with the spherical bearings you are leaning towards, as bellcranks usually only rotate around a single (stationary) axis, unless you will be using 2 of these spherical bearings.

If you line up your loadings from the pushrod / pull rod in the plane of the bellcrank you can eliminate any axial loading of the bearing, although watch this at extremes (full compression).

Why you leaning to the spherical ball type ones?

Jake

 

[V12]

I was thinking spherical because it doesn't have to resist out of plane loads. The bearing compensates by aligning with the loads.
What size of bearing do you use.
Thanks

 

[mloew]

V12,

I agree with RaceEngJr. Although I am a fan of minimum constraint design, I think you will be leaving an extra DOF (or two) "on the table" with a spherical joint for the bell-crank bearing. Unless the off-axis angularity is very small thought he whole range of travel, I can envision some potential problems. Good luck in your design.

Best regards,

Matthew Ian Loew
"Luck is the residue of design."
Branch Rickey

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[RaceEngJr]

I would recommend the standard type bearing which resists out of plane loads personally, by having the spherical bearing you introduce unwanted movement which can effect the geometry or alignment of the components and therefore load. Im also thinking it could effect your insallation ratio of the springs, so you'll get a variable spring rate at the wheel which you have no control over!

The size really depends on what your pushrod load will be and the angle between your pushrod and spring/damper unit. If you dont know what bearing size, look up the skf bearing catalogue on the net, gives full details of bearings.
As an example we had a standard bearing of about 32x12x10 with a max pushrod force of about 6kN with an angle of 90Deg between pushrod and spring/damper unit.

Jake

 

[Tmoose]

"I was thinking spherical because it doesn't have to resist out of plane loads."
I can imagine a single spherical pivot could be arranged to handle only compressive loads (example = ball pivot Checy rocker arms, although they require anti-rotation sideways guidance at valve and pushrod). It might get floppy when presented with tensile loads.
A pair of the sphericals on a common axis could then provide guidance and reduce the necessity of align boring the bell-crank.

 

[Tmoose]

Mixing engine types - Semi-Vintage Chevy rockers do not grip valve stem for guidance. They just guide the pushrod at 2 places