[dataway]

I'm still going to re-assemble my spare column, put it all back together with the bearing greased and the springs all in place to check it before I commit to making anything.

I have a feeling all the kind of "delicate" construction down there is purposeful and has something to do with the way the column is kind of supposed to self destruct on impact ... a big strong ball bearing down there wouldn't be conducive to that

[JSchmitz]

Originally Posted by dataway

I'm still going to re-assemble my spare column, put it all back together with the bearing greased and the springs all in place to check it before I commit to making anything.

I have a feeling all the kind of "delicate" construction down there is purposeful and has something to do with the way the column is kind of supposed to self destruct on impact ... a big strong ball bearing down there wouldn't be conducive to that

That's a good point that I hadn't considered. Good thinking! Thanks for pointing that out.

[dataway]

Have the basic components laid out for a bushing type bearing.

More measurements need to be taken. Gives me a lot of exercise going up and down the stairs to the shop

[dataway]

Wouldn't it be nice if it was this easy.

But .. it's not

[JSchmitz]

Originally Posted by dataway

Have the basic components laid out for a bushing type bearing.

More measurements need to be taken. Gives me a lot of exercise going up and down the stairs to the shop

Nice work there! I wish I had those skills.

Make two and let me know what I owe ya.

[dataway]

Replicating the OEM plastic bearing carrier ... then I'll decide just how much I can simplify it to reproduce it in metal, suitable for holding a bushing.

[dataway]

I absolutely love doing this kind of work, would have been nice if I made a lucrative career from it rather than dicking around in my little shop for pennies. No one ever accused me of being a good businessman, or of running away from meaningless work that I created out of thin air

Of course Ames just posted that they will have the 68 lower bearing conversion kits back in stock at the end of the week ... dohhh

[JSchmitz]

Originally Posted by dataway

I absolutely love doing this kind of work, would have been nice if I made a lucrative career from it rather than dicking around in my little shop for pennies. No one ever accused me of being a good businessman, or of running away from meaningless work that I created out of thin air

Of course Ames just posted that they will have the 68 lower bearing conversion kits back in stock at the end of the week ... dohhh

You can't put a price on happiness they say. I can make the parts. Just never learned the CAD skills.

[dataway]

I came at it from the other direction, could do the CAD before I ever had a single machine tool. Not the best direction to go ... you need to know what CAN be made before you design something. So now I have to spend a lot of time simplifying designs so they can be made with my simple machines, or more accurately .. my simple tooling.

In the design above you can probably tell the grooves are way too deep to be easily machined ... I guess I could spend a lot of time with a small diameter mill and turning the rotary table. Too deep and narrow to do on a lathe. So next step is to see how much I can shorten it and still hold everything were it needs to go. I think the plastic pieces had that extra depth because the material isn't very strong.

Last step is to throw the ruined part across the shop after four hours of work and order the part from Ames

[dataway]

Duhhh..... was brushing my teeth before nap time and it came to me ... jeez, if I'm going to use a bushing ... all I have to do is turn up a bushing that fits and stick it in. No carrier, no modifications ... just a simple bronze or Delrin bushing the same dimensions as the OEM bearing.

Part of me is disappointed it's that simple

[dataway]

It's a done deal now. Took an hour or so with the test fitting. Fit is excellent, gave it about 0.002" clearance to the shaft. Made it a snug fit in the carrier but easily inserted by hand.

Tested it all out on the spare column, can't for the life of me see why this isn't a better solution than the OEM bearing, and it preserves the collapsible nature of the column. Saved myself $75 too.

I need to try to find out what material I used. I ran a few quick tests on this and what I think was UHMW polyethylene and this gray product seemed considerably tougher, not harder, not really slipperier .. but definitely tougher.

I'll have to check my records and see if I can find out what it is, just in case it's real sensitive to moisture or heat.

[JSchmitz]

That looks like Nylatron. Great stuff! It is a little challenging to turn. Damn plastics wrapping around the chuck!!!

I hear ya about making it simple. Curious why you didn't just eliminate the factory carrier since you were making a bushing anyway. Closer to stock appearance? Good solution regardless.

[dataway]

Jeez, I was going to mention what a pain it was to turn ... but I thought it would make me look amateur Tried HSS bits first ... ehhh, then bored it with insert tooling and did pretty good at about 1800 rpm .. but man, plastic going all over the place, looked like a cotton candy machine. Does look like the product you described .. I probably purchased it to make bushings for vintage motorcycles, or for sacrificial "sliders" on the frames/body.

Two reasons ... didn't have that stuff in large enough diameter ... and man, that carrier, all those grooves are different widths, different heights, and different depths. Would definitely been a challenge to machine.

BTW .. that's my "junk" carrier ... the column I'll be using is way nicer, but still sloppy.

[JSchmitz]

Originally Posted by dataway

Jeez, I was going to mention what a pain it was to turn ... but I thought it would make me look amateur Tried HSS bits first ... ehhh, then bored it with insert tooling and did pretty good at about 1800 rpm .. but man, plastic going all over the place, looked like a cotton candy machine. Does look like the product you described .. I probably purchased it to make bushings for vintage motorcycles, or for sacrificial "sliders" on the frames/body.

Two reasons ... didn't have that stuff in large enough diameter ... and man, that carrier, all those grooves are different widths, different heights, and different depths. Would definitely been a challenge to machine.

BTW .. that's my "junk" carrier ... the column I'll be using is way nicer, but still sloppy.

No shame there. Those materials are a challenge.

That'll work perfectly. Good luck!

[dataway]

I just found the product you described ... ordered some of that. I noticed that the material I used has a temp limit of 180 degrees ... seems a tad low for engine compartment use. The material you mentioned has a temp limit of 230 degrees, seems more suitable, and is called out specifically for use in bushings. I'll just remake the bushing in that.

Will be a week or so before I put in the column so plenty of time. Thanks for the recommendation.

[Shiny]

Very cool! Always fun yo see your ideas and work.

Good catch on the temp ratings.

Suggest you also check material for chemical compatibility too. Oils, greases, solvents, etc. may get in there.

Nylon absorbs moisture, but shouldn't matter in this application. I don't know about hydrocarbons but would look it up. I don't know Nylatron.

Delrin/acetal/POM family may be an option and easy to find.

Polysulfones are more expensive but may also be a good option.

Hard to know why a ball bearing was used there but probably about low clearance/ability to preload and wear resistance. Engineering plastics then were nowhere near what they are today. Dirt/dust is mostly silica. Will grind soft material. May have been a concern for a car used daily in bad places for 10 years but you don't need that. Plus you provide your own warranty!

[JSchmitz]

Originally Posted by Shiny

Very cool! Always fun yo see your ideas and work.

Good catch on the temp ratings.

Suggest you also check material for chemical compatibility too. Oils, greases, solvents, etc. may get in there.

Nylon absorbs moisture, but shouldn't matter in this application. I don't know about hydrocarbons but would look it up. I don't know Nylatron.

Delrin/acetal/POM family may be an option and easy to find.

Polysulfones are more expensive but may also be a good option.

Hard to know why a ball bearing was used there but probably about low clearance/ability to preload and wear resistance. Engineering plastics then were nowhere near what they are today. Dirt/dust is mostly silica. Will grind soft material. May have been a concern for a car used daily in bad places for 10 years but you don't need that. Plus you provide your own warranty!

You raise a good point about contamination. That could be bad for a bushing in the engine compartment.

[dataway]

Looks like the nylon is good for petroleum products, but I'd probably give it another couple thou clearance for moisture swelling. The Delrin is down around 180 degrees like the Polyethylene I used, but is really tough ... didn't realize Turcite is basically the same thing ... that stuff is now used on the wear surfaces of machine tools.

I can see there is a lot to know when it comes to plastic material selection. Wonder if anyone makes an app to plug in requirements and show material options. Not for this project really, but would come in handy.

What surprises me about the OEM solution is not so much the use of a bearing, but the use of such a low quality bearing in what you would think is a critical component, in a very hostile environment. I've never looked at a 69 bearing, but they did make a change in 69 that continued right into the 80's. From the pictures I've seen the 69 and later style is all sealed up much better than the 68 bearing, but evidently not the same dimensions.

It's obvious the spring is there to preload the bearing, but the necessity for pre-load seems to only be a function of the type of bearing they used, not something necessary for the overall design ... doesn't look like the 69 and later bearing requires it.

Always interesting trying to reverse engineer the OEM designs, in this case it baffles me why they didn't just use a standard sealed ball bearing (other than they are almost impossible to find with a 1" bore and less than 2" OD), or a needle bearing with an inner race sleeve on the shaft, and a seal. I CAN see that their solution was affordable, a bearing and spring that cost pennies. But jeez, no seal to speak of? They did use some kind of rubberized goo that appears to have degraded in short order to cover the outside of the bearing.

And, from what I've seen of these old columns ... I'd bet in 90% of them the steering shaft is just spinning inside the inner race on both upper and lower bearings ... making it effectively a bushing. It was doing that on both upper and lower bearings on both my columns ... and they felt just fine from the steering wheel.

I enjoy this stuff ... I realize that vast majority of people don't care, but I'd sit in a bar and discuss something like this for an hour

[Shiny]

I agree it's interesting to guess at material and design decisions made decades ago. Sadly, I was helping make those kinds of decisions starting in 1976 so maybe I can sprinkle some distorted memories onto my guesses. I never worked in automotive nor any other "outdoor" equipment so assume my guesses came from that barstool.

I have never seen an automated polymer selector, but I expect some of the major suppliers will come close on their web sites. Here's a 2-second Bing search blurby overview link that might point to sources of real info:

http://www.tpacomponents.com/uploads/pdf/en/0205_EN.pdf

You can probably find many more like this.

Material selection in most commercial products is about cost, then cost, and finally cost. For any part, the "engineering requirements" are set first and then it's easy to compare prices for design, material, fabrication, shipping, and assembly options. Design engineers can quantify required stress and strain. Lowest cost to meet requirements wins until there is uncertainty. Reliability requirements are usually more uncertain than any so the focus turns to consequences of failure. How would you life-test a steering column without really knowing the contaminants? The consequences of failure under warranty and/or safety implications would probably over-rule total cheap and justify spending a little more to avoid failures. A 20-year history of field success with ball bearings in this application would probably sway decisions in 1968.

This application is not demanding as you have commented. There is really nothing for the bearing to do but allow the shaft to spin. The loads are small, the tolerances are crude, and even the friction requirements are not demanding. The rpm is near zero so there is no real care about "typical" bearing design criteria like friction, runout, fatique, lubricant loss, noise, etc. You might argue squeaking or grinding could be bad.

I'll stick with a cheap ball bearing being chosen because it was perceived low risk for failure, was easy to source and assemble, and would tolerate a lot of unknown and unpredictable abuse. It might not continue to roll smooth over its "design life" but it was unlikely to bind up, would not dissolve, would not get brittle or fall apart. Even if the bearing dried up, got looser, or locked up from corrosion, the column would probably still function and nobody gets hurt.



Note: if the bushing swells from absorbing water or oil, the ID will expand so you don't need more clearance to tolerate this. This used to be a common "interview question" for new hires. It's not intuitively obvious so takes some thinking!

[dataway]

You know, no matter how many times I heat something up to increase the ID I still instinctively think a donut hole will get smaller if the donut gets bigger

And many years ago we covered that in class quite thoroughly, unfold the donut, calculate the linear expansion of length and cross section ... put it back together ... the hole is larger.

Thanks for the insights into product design ... in my world everything would have been every expensive but worked very well

BTW ... how close do you think I could come to identifying a type of plastic based on density? I know some might have fillers etc. but this would be more of a go, no-go test for UHMW polyethylene, PTFE, Delrin, Nylon etc.