King pins

I have no dog in this fight, but I wondered about what has been said about the rollers only partly rotating when the spindle turns. I did a little basic math and came up with a calculation that seems to indicate that if the spindles turn 30 degrees in operation, that would equal 1 full rotation of the needle, given no slippage. Could some one who has the specs on one of these sets do some measurements of the exact diameters (needles and king pins) of the actual parts involved? The formula I used is :

(pi X KP)/12 divided by pi X NB

(KP=King Pin Diameter, NB=Needle Bearing Diameter)

For my purposes, I believe the material involved is of secondary importance (given the way most of us drive these cars).
 
tubman said:
I have no dog in this fight, but I wondered about what has been said about the rollers only partly rotating when the spindle turns. I did a little basic math and came up with a calculation that seems to indicate that if the spindles turn 30 degrees in operation, that would equal 1 full rotation of the needle, given no slippage. Could some one who has the specs on one of these sets do some measurements of the exact diameters (needles and king pins) of the actual parts involved? The formula I used is :

(pi X KP)/12 divided by pi X NB

(KP=King Pin Diameter, NB=Needle Bearing Diameter)

For my purposes, I believe the material involved is of secondary importance (given the way most of us drive these cars).
Click to expand...

As I recall the needles in mine that I installed on my Merc. looked to be appox. 1/6" dia. riding on a .812 pin dia.
That figures to be a little more than one full rotation in 30° of steering movement.
And in appox. 10° of steering movement the needles will be crossing over each others path.
 
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51 Merc-CT,

Just to clarify, you meant a needle bearing diameter of 1/16", don't you?

I would think that normal use and a couple of "lock-to-locks" parking would cycle the needle bearings enough.

Tubman
 
The only experience I have with the needle bearing type was in a car that had shimmy. But I never drove that car before these were fitted. But the owner had them fitted in his words "because it had shimmy, and these fixed it!" well not when I drove it round the block, hit a small dropped drain cover at about 10mph, and the front end went into shimmy, shaking my hands something crazy.
I have eliminated shimmy on a hot dog by fitting new kingpins and bushes, that I ream with a slightly worn reamer (a very small tickle undersize) this produced a tight fitting pin, and couldn't get it to shimmy afterward, no matter how hard I tried. I concluded from this, the needle roller type were not for me.
I will say this though. There is loads of different grades/hardness types of stainless steel, not just one. So I don't think they should be "pooh poohed" due to "stainless is just stainless, and it's soft" but common grades of stainless work harden very easily. Maybe this is an advantage in this respect? Try drilling a 1/2" hole in stainless with the drill running to fast. You'll see what I'm saying.
Martin.
 
tubman said:
51 Merc-CT,

Just to clarify, you meant a needle bearing diameter of 1/16", don't you?

I would think that normal use and a couple of "lock-to-locks" parking would cycle the needle bearings enough.

Tubman
Click to expand...

!/16" needle dia, but may have been as much as 3/32" (from memory)
 
Iteresting topic. I replaced king pins on a VW bug many years aGO and did not ream quite enough out of the bushings, I had to grease weekly to steer properly it took many miles to wear them in! I have been considering SS for my 50 Ford, now not sure.Thanks Gary
 
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It's not unusual to use needle bearings in applications where they may not move much - consider the typical spicer u-joint.

Mr Spadaro's concern about hardness is reasonable, but unfounded IMHO. I'm not sure about the HRC scale, but heat-treated type-431 stainless has a Brinell hardness of about 400. This compares very well to plain carbon or other alloy steels. Type-304 stainless has a Brinell hardness of about 160 ... still very good compared to carbon or other alloy steels. Hardness is not the stainless steel Achilles heel - rather it is yield strength... its ability to withstand torque.

I'm a mechanical engineer by background... my numbers are coming from my CRC Handbook of Tables for Applied Engineering Science.

My '43 Willys jeep specs tapered roller bearings for the kingpins, and the pins do indeed suffer from galling from the bearing rollers -- particularly if the bearing pre-load is wrong or if lube is poor.
 
More mental ramblings... I think a better design would be to use two tapered roller bearings over needle bearings because then the "friction" or preload could be precisely set. I would still prefer a well-lubed needle bearing over a bronze bushing. The stainless pin is mostly just eye candy though, as Mr Spadaro suggests.
 
I'm not sure the Brinell scale is the correct scale to use. My Brinell scale doesn't go high enough to give a hardness reading for a bearing, that's why I used the Rockwell C scale. A Brinell hardness of 400Br = 43 RC. On a shaft which must accept a roller bearing with a hardness of around 68-70RC this difference is too much. A shaft must be close to the hardness of the bearing otherwise the softer material will wear too quickly.

My Hardness Converter has the highest Brinell measurement at 739 which equals 65 RC, and that would be within the hardness range for a shaft using Roller bearings. If I extrapolate the Brinell scale to a theoretical 790 that would equal 68RC which is on the lower side of roller bearing hardness. IMO type 431 S/S @ 400Br or 43RC is not hard enough to adequately perform in this application.
 
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Huh... thanks FE26! Learn something every day...

Here's a conversion for those of you interested: http://www.engineersedge.com/hardness_conversion.htm

Here's another page that suggests that the most common bearing steel is SAE 52100, at a Rockwell C hardness of 60-64 which is in line with the lower end of FE26's numbers. http://www.astbearings.com/bearing-materials.html

It looks like a"typical stainless material" kingpin would indeed be too soft for a "typical needle bearing" steel. However, the astbearings page suggests that martensitic stainless steels do exist that would be hard enough.

Whether stainless steels for this application are an improvement or not, is another matter.
 
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