[DeTomaso] Steering Rack Bearings - 1622 ZZ are not the right ones!!

robert stewart rspink2012 at yahoo.com
Tue Aug 31 09:08:58 EDT 2010


Well the rack is back on the car but the car is still on car stands as the 
restoration continues. New Air conditioning  system mounted in the front - some 
relays to deal with the bigger fans etc. Put the engine back in.  etc etc - 
probably a few months still.

 For interest sake I will give Lars a call but 15 years sounds pretty good to 
me. 


Thanks

Rob




________________________________
From: Gray Gregory <rgg at gregorycook.com>
To: Richard Barkley <rlbpantera at earthlink.net>; John Taphorn 
<jtaphorn at kingwoodcable.com>
Cc: Detomaso List <DeTomaso at realbig.com>
Sent: Tue, August 31, 2010 7:45:41 AM
Subject: Re: [DeTomaso] Steering Rack Bearings - 1622 ZZ are not the right 
ones!!

John, Robert,

I can't remember if you said the rack was back in the car or not? If not why 
don't you just call Lars and ask to get some angular bearings in the same size? 
If he doesn't have them on the shelf he will be able to get them in a day or 
two. He should also be able to shed some expert light on this discussion!

If it is already back in the car I'd drive it and be happy knowing that you 
might only get 15yrs of life out of them instead of 30. :>)

Gray

-----Original Message-----
From: Richard Barkley [mailto:rlbpantera at earthlink.net] 
Sent: Tuesday, August 31, 2010 1:52 AM
To: John Taphorn
Cc: Gray Gregory; Detomaso List
Subject: Re: [DeTomaso] Steering Rack Bearings - 1622 ZZ are not the right 
ones!!

  John,
Good to hear from you.

First the good news: Turns out that the 1622 ZZ bearings are of the 
"deep-groove radial" type as listed here:
http://www.intechbearing.com/1600Series-DeepGrooveBallBearings2Shields.html
The (maybe) bad news follows.

>From wikipedia we get http://en.wikipedia.org/wiki/Ball_bearing
> For single-row deep-groove ball bearings, SKF's documentation says 
> that maximum axial load is circa 50 % of maximum radial load, but it 
> also says that "light" and/or "small" bearings can take axial loads 
> that are 25 % of maximum radial load.[3]
http://tinyurl.com/284clmh list a 1622 ZZ that has a static radial load 
of 747 lbs. so the axial load rating would be about 375 lbs. But not all 
bearings are created equal. Here is one that is rated at only 354 static 
radial.
http://www.dynaroll.com/1600seriesZZ.asp
  Anyway, all of the axial load would go to just one of the two 
bearings, depending on which way the steering wheel is turning.

So the question is, what are the likely loads? The load will be 
proportional to the torque (force) turning the steering wheel. For 
normal driving the max would be at low speed, say parking the car and 
turning the wheel while not moving. If the pinion has a 45 deg pitch on 
its "threads" then, ignoring friction, the axial force will be equal to 
the force on the rack. If you have a 1 ft dia steering wheel and turn 
with, say, 12 lbs with each hand you generate 24 ftlb of torque. If the 
contact point on the pinion with the rack is at a 1/2" radius, there 
will be a factor of 24 multiplying effect. So the net axial force on the 
bearing will be 24 x 24 = 576 lbs. Yikes!

When you exceed the static load rating of a bearing, the elastic limit 
of the balls (and maybe the race) is exceeded and one or more of them 
will be deformed. Over time I guess you would end up with a bunch of 
lumpy balls that wouldn't roll too smoothly. But I don't think there is 
much chance of the bearings blowing apart, but maybe not. If the cage 
that locates the bearings around the race gets eaten up or rusts away, 
the balls fall out and... no more bearing.

The thing the worries me is Rob wrote: " When we took the rack apart we 
found that top bearings that sit in an open race where in many pieces." 
What kind of bearing was in there? Were they the original "Angular 
Contact" type or had they been replaced with radial BBs? Had all the 
balls fallen out or were the races broken? The thing that worries me is 
that if both bearings let loose (one first the second later) like the 
top one did it seems possible that the pinion could no longer contact 
the rack and you would LOOSE STEERING! If this happened at high speed, 
it could be catastrophic...... It may be that the rack has a fail safe 
design, so even it both bearings fail you can still steer, but I 
wouldn't count on it.

Richard

On 8/29/10 5:25 PM, John Taphorn wrote:
> Hi Richard
>
> Good info.  The rack is in place and ready for testing when the car 
> gets under power in a couple months.
>
> Since the pinion's shaft clearance, in and out, is contained by 
> spacers in the rack's housing, I would think the axial loading 
> minimal.  Although, perhaps I misunderstand the application of "axial" 
> in this application.
>
> Regardless, we will report back any problems.  Initially, there is no 
> binding when turning the pinion shaft in either direction.  It appears 
> to be a very happy camper.
>
> I suppose if the exercise requires another $8 in bearings after 10 
> years, that will not be so bad.  I'll add that if I faced the same 
> issue today, I would go with those bearings happily with naive 
> confidence.
>
> JT
> ----- Original Message ----- From: "Richard Barkley" 
> <rlbpantera at earthlink.net>
> To: <rgg at gregorycook.com>; "Detomaso List" <DeTomaso at realbig.com>
> Sent: Sunday, August 29, 2010 6:59 PM
> Subject: [DeTomaso] Steering Rack Bearings - 1622 ZZ are not the right 
> ones!!
>
>
>>  Rob,
>>
>> I'm afraid to say but you don't have the right kind of bearing for this
>> application. I went through this about 10 years ago. The problem is that
>> the rack and pinion gears are cut at about a 45 deg angle which means
>> there will be an axial load on the bearings about equal to the load on
>> the rack. Regular ball bearings are meant for primarily radial loads and
>> can fail quickly with axial loads although, due to the low rotation
>> rates that may not be the case here. The original bearings have the
>> balls contacted at a 45 deg angle. Here's a link to pictures and
>> diagrams on my website.
>>
>> http://home.earthlink.net/~rlbpantera/rack/index.html
>>
>> Here's the discussion that went on in 2000:
>> http://realbig.com/detomaso/2000-03/814.html
>> hit the < or > arrows to move through the discussion. Fortunately nobody
>> at that time suggested that I use a regular BB as a replacement.
>>
>> At the time Larry Stock had some of the bearings and I bought a pair
>> from him. The bearings you have now may work for a while (maybe quite a
>> while?) but should eventually fail. A better alternative, if the correct
>> ones can't be found, would be a deep grove bearing (the 1622 ZZ don't
>> appear to be that) which are better at handling axial loads.
>>
>> Richard
>>
>> robert stewart Wrote:
>> A few weeks back John Taphorn and I removed the steering rack from my
>> car hoping
>> for a relatively quick exercise of cleaning to up, painting adding the
>> zerk and
>> lube. When we took the rack apart we found that top bearings that sit in
>> an open
>> race where in many pieces.
>>
>> After a quick consultation with Mike Drew there didn't appear to be a
>> well know
>> replacement for the bearing.
>>
>> John suggested I visit a good friend of Gray Gregory - Lars Nielsen at
>> Motion
>> Industries in Houston. To say Lars was helpful would have been a huge
>> understatement. He took the rack measured the bits and pieces of the
>> bearing and
>> race and identified a replacement suggesting a fully enclosed bearing
>> instead of
>> the open one. In addition he took the rack into the backroom and worked
>> with one
>> of his shop guys to remove the other bearing and race.  It was quite a
>> pain to
>> get out. Heck he even used a parts washer to clean up the rack. Can 
>> you say
>> "above and beyond".
>>
>> The two bearings which are part number 1622 ZZ cost me about $4 each and
>> are
>> fantastic. The rack turns very easily  and even though the bearings are
>> sealed
>> the lubricate that we put in through the zerk is still able to move
>> throughout
>> the rack as intended.
>>
>> Thanks to Gray, Lars and John.
>>
>> Rob
>>
>> -- 
>> -----
>> Sincerely, Richard Barkley
>>
>> To Ski or not to Ski, that is the question!
>>
>> Richard Barkley (310) 373-6695 (home)
>> E-mail:  rlbpantera<atsign>  earthlink.net
>> ZONKEY'S home page: http://home.earthlink.net/~rlbpantera
>> Mammoth Lakes Vacation Condo: 2BR+loft/3Bath - Horizons 4 #186 (760) 
>> 934-6758
>> Condo web address: http://home.earthlink.net/~rbarkley
>>
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-- 
-----
Sincerely, Richard Barkley

To Ski or not to Ski, that is the question!

Richard Barkley (310) 373-6695 (home)
E-mail:  rlbpantera<atsign>  earthlink.net
ZONKEY'S home page: http://home.earthlink.net/~rlbpantera
Mammoth Lakes Vacation Condo: 2BR+loft/3Bath - Horizons 4 #186 (760) 934-6758
Condo web address: http://home.earthlink.net/~rbarkley

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