Pin drive bolts splitting Help Please

[David Kirkham]

Originally Posted by Blas

Interesting, but I wonder how this fit-up differs from the hundreds of millions of regular passenger cars on the road today with regular lugs nut holding their wheels on? Still, it doesn't reflect well on the quality control practices in place of these preminm wheel manufacturers does it.

I am quite sure regular passenger cars have very carefully controlled tapers that match between the lugs and wheels. Their quality control is really quite good.

As I explain more of what is going on, I think you will agree with what I think is going on.

David

[David Kirkham]

In this picture, I flipped the pin over so it would be easier to understand what is going on.

The pink and green lines represent the wheel pushing on the pin during acceleration or braking.

The red line represents the 90 degree taper of the hub adapter. (I have exaggerated the angle to make it easier to see what is going on.)

The yellow line follows the 76 degree taper of the pin.

The blue lines represent your underwear.

[Ant]

David brilliant job, I normally look indepth at components to see if they are engineered correctly, but wouldnt have thought to on the pin drive nuts.

We have machined all our hubs from 4140 front being similar to original with press in pins and retaining nuts so not a problem there, but on the rear we made adapters similar to Trigo, I tested the Trigo adapters before I sold them and they are just normal soft free machining steel from memory so I wasnt happy with them even though that type of steel is probably adequate for the job.

I am using Cap screws and the Trigo Pin drive bolts on the rear, but now have major concerns with the small seating ring area, and I have had two of these trigo pins have approx 3/32" chunks of metal break off the inner sharp taper just with assembly maybe the metal is quite hard or brittle!
I will consider machining the correct taper or making new ones, we used to make them with two flats which isnt as nice to work with as the internal 12pt or if anyone is supplying a better product I would be interested.

[Paul F]

Uggh! I didn't look at the pins. Of the other 4 I have, two have several fractures on the non-taper side. There are no fractures on the taper side.

David, looking at the picture of the hub in my previous post, do you think Trigo and Compomotive hubs come from the same vendor?

I'm thinking they both buy pins from one vendor and hubs from another vendor, but don't spec the parts. Thus the mis-match. Just a guess.

[David Kirkham]

So...

What exactly is going on?

Let's do a thought experiment.

Would you rather Jamo stepped on your foot with his shoes?

or

Would your rather have a tiny 100 pound woman step on your foot with a stiletto heel?

This, is called psi, or pounds/square inch.

Mild steel (1018) has a yield strength of around 50,000 psi. No matter how hard you jump on it, you probably won't do anything to it.

Now, take a simple nail in your hand and scratch the steel. Can you do it? Of course you can. If you push hard enough, you can probably even pull up a burr on the steel. Now, you can only pull up a burr if you YIELD the steel or surpass 50,000 psi. That means you somehow put OVER 50,000 pounds/square inch on the steel. So, you lean on the steel (maybe 100-150 pounds) and you drag a SMALL nail across the surface...WALLLA, you get a scratch.

Now lets talk about your nuts (pins).

People on this thread have been talking about pins loosening up, using Locktite, galling, and all sorts of other nasty things.

Why would, could the pin loosen up? I mean your torqued it to 80 foot pounds, right?

Well, if you have a small area of material (think the small shiny ring in the above pictures) and you put a lot of force on it (think 60-80 foot pounds of torque multiplied by the mechanical advantage you get due to the incline of the threads on your nuts) then you have put a lot of force (pounds) on a very small amount of area (square inches). (Kinda like that woman who stomped on your foot with high heels or that nail you scratched the mild steel plate with.)

Now it gets worse. The very, very small end of taper on your nuts is rather sharp. There is very little material there...or there is a small amount of square inches of material there. As the square inches go down, the pounds required to yield that particular area goes down as well. Think it is way easier to bend a paper clip than it is to bend your shift lever. Why? There is more material in your shift lever to bend EVEN THOUGH the yield strengths of the shift handle and the paper clip are roughly the same.

Well, it gets even worse.

Take the pin and load the contact area further by bending the pin with your wheel as you accelerate or brake. The pin will smash even further into the small contact area until it...yields.

Yield means it moves. Now there are two types of yielding-- elastic and plastic. Elastic yeilding is what happens in a typical spring. You apply the force the spring deflects and then when you remove the force the spring moves back to its original position (or shape). Plastic yielding (or more correctly stated plastic deformation) occurs when you go beyond the elastic range and go to where you are permanently bending the material. A good example of this is when you play with a slinky. In the beginning, you play nicely with the slinky it will always return back to the original position. Then you get a little naughty and pull it too far you bend the coils. You ALL KNOW what I am talking about. What has happened is you have plastically deformed your slinky. In other words you bent it. Now back to the your nuts.

If the material under the nut (or heaven forbid, your nuts themselves) yields into the plastic region the preload that you had on your nuts is now gone. In other words, your nuts are now loose.


David

[Paul F]

Thanks for the dissertation David. Most educational.

What do we do about it? I assume the best thing to do is make the tapers on the new pins you're making, match the hubs. Yes?

[David Kirkham]

Originally Posted by Ant

David brilliant job, I normally look indepth at components to see if they are engineered correctly, but wouldnt have thought to on the pin drive nuts.

We have machined all our hubs from 4140 front being similar to original with press in pins and retaining nuts so not a problem there, but on the rear we made adapters similar to Trigo, I tested the Trigo adapters before I sold them and they are just normal soft free machining steel from memory so I wasnt happy with them even though that type of steel is probably adequate for the job.

I am using Cap screws and the Trigo Pin drive bolts on the rear, but now have major concerns with the small seating ring area, and I have had two of these trigo pins have approx 3/32" chunks of metal break off the inner sharp taper just with assembly maybe the metal is quite hard or brittle!
I will consider machining the correct taper or making new ones, we used to make them with two flats which isnt as nice to work with as the internal 12pt or if anyone is supplying a better product I would be interested.

Ant,

Hard does not always equate to brittle. Think of a really high quality steel that is properly heat treated. I once saw a F1 1/2 shaft from a crash that was bent at 90 degrees! It didn't break! It didn't even have a crack. But, that junk "free machining steel," "leaded steel," and other such abominations can be quite soft and the lead inclusions will make it brittle. Perhaps that is why we have seen so many of the threads torn and broken. I would have to do a chem and hardness on the pins, but I don't know if I want to spend the 100 bucks on the test.

As for making you pins, that is no problem.

David

[David Kirkham]

Originally Posted by Paul F

Uggh! I didn't look at the pins. Of the other 4 I have, two have several fractures on the non-taper side. There are no fractures on the taper side.

David, looking at the picture of the hub in my previous post, do you think Trigo and Compomotive hubs come from the same vendor?

I'm thinking they both buy pins from one vendor and hubs from another vendor, but don't spec the parts. Thus the mis-match. Just a guess.

Not sure if the Compomotive and Trigos come from the same vendor. I would have to see them side by side.

As for the mis-match on tapers...I can think of no reason why anyone would make a 76 degree taper? It simply makes no sense to me. I think someone had a quality control issue.

David

[David Kirkham]

Originally Posted by Paul F

Thanks for the dissertation David. Most educational.

What do we do about it? I assume the best thing to do is make the tapers on the new pins you're making, match the hubs. Yes?

First thing is to make sure the tapers match.

Matching tapers don't really matter if you have crappy material. Make sure your nuts are made from good material--otherwise you may loose them.

David

[CNGreen]

Wow. Just... wow.

Boy am I glad I sent you the pin with the adapter (snout)!!

Thank you david for the thorough analysis. I'm very certain my car will end up being safer as a result.

BTW it's worth noting that all this is with 1/4 mile TOTAL on the car!!

[Dominik]

Sadly, that problem has been around for years with "wheels sticking" (due to non-concentric nuts)
I had new nuts done for my clients in Germany and South-Africa since years.
Gladly, we found someone to take on the problem in the US and solve it with the help of all here :-)
Ironically, Kirkham does not even use that setup!

Now we can start a new thread about the spinners...

Dom

[David Kirkham]

Originally Posted by CNGreen

Wow. Just... wow.

Boy am I glad I sent you the pin with the adapter (snout)!!

Thank you david for the thorough analysis. I'm very certain my car will end up being safer as a result.

BTW it's worth noting that all this is with 1/4 mile TOTAL on the car!!

Thanks for the kind words! I'll send your loot back soon!

David

[David Kirkham]

Originally Posted by Dominik

Sadly, that problem has been around for years with "wheels sticking" (due to non-concentric nuts)
I had new nuts done for my clients in Germany and South-Africa since years.
Gladly, we found someone to take on the problem in the US and solve it with the help of all here :-)
Ironically, Kirkham does not even use that setup!

Now we can start a new thread about the spinners...

Dom

Dom,

Another problem I did not address is the potential under such extremes for galled material to push itself under one side of the nut and "tip" it to one side or another. Thus making wheels very hard, if not impossible, to take off and put back on as the bolt hole circle will not be in the proper orientation.

Bending the pin straight is a very BAD idea. You will load an even smaller area of the pin on the side you bent it towards and have the pin fail even faster. If the pins don't line up then you need to step back, find the problem, and correct it.

I will address concentricity shortly. I suspect it is not too good.

David

[Paul F]

Originally Posted by Dominik

Sadly, that problem has been around for years with "wheels sticking" (due to non-concentric nuts)
I had new nuts done for my clients in Germany and South-Africa since years.
Gladly, we found someone to take on the problem in the US and solve it with the help of all here :-)
Ironically, Kirkham does not even use that setup!

Now we can start a new thread about the spinners...

Dom

But...but we haven't finished this one. David suggest we make the tapers match and make them out of good material.

David, you made a bunch of pins. Can we use them?

[Dominik]

I will address concentricity shortly. I suspect it is not too good.

David
[/quote]

No, it was never good. It has been addressed in the SCOF (Superformance Forum) some years ago as well.

Except with Vintage it mattered less because they have 7/10mm play between pin and hole... (hole diameter in wheel: 19.7mm)
And apparently they also have a slightly better pin to start with! Or even a smaller diameter pin.

The spinner not coming loose is being discussed while we speak.
Can't get spinners off

I have some red wine now.

Dom

[David Kirkham]

We just measured TIR at 0.004"

Not horribly bad, but all those tolerances add up.

0.004 on the hub holes
0.004 on the pin
0.004 on the wheel
0.004 on the hub adapter to the hub

and you are now out 0.016 and you wonder why your wheels won't go on. Now, I am not saying the hub and wheel are out. I am just illustrating the nasty concept of "Tolerance Stacking."

David

[David Kirkham]

Originally Posted by Paul F

But...but we haven't finished this one. David suggest we make the tapers match and make them out of good material.

David, you made a bunch of pins. Can we use them?

Hard to answer. Depends on your adapter.

Our pins are 90 degrees so they will fit a 90 degree taper. The Vintage hub adapters are a 60 degree adapter. We can make those too, without much grief.

The only adapter I have measured is a Trigo. It is 90 degrees. I assume the Vintage hub adapter is 60 degrees, but I don't know. I'd need one to measure.

Also, I don't know about the Compomotive; I'd need to measure one.

David

[David Kirkham]

Originally Posted by Dominik

The spinner not coming loose is being discussed while we speak.
Can't get spinners off

I have some red wine now.

Dom

That is because our tapers DO match.

David

[Larry N Johnson]

Originally Posted by David Kirkham

The Vintage hub adapters are a 60 degree adapter. We can make those too, without much grief.

The only adapter I have measured is a Trigo. It is 90 degrees. I assume the Vintage hub adapter is 60 degrees, but I don't know. I'd need one to measure.

David

David,

I will attenpt to steal a Vintage Adapter from Terry Stapley and deliver it Monday. That way, you will have the Vintage Wheel, Vintage Pin, and Vintage Spinner. Now if we only had a 94-95 Mustang hub...

Originally Posted by Dominik

Except with Vintage it mattered less because they have 7/10mm play between pin and hole... (hole diameter in wheel: 19.7mm)
And apparently they also have a slightly better pin to start with! Or even a smaller diameter pin.

Dom

Dom,

David Kirkham and David Cindrich both measured the Trigo holes and the Vintage Holes. Exactly the same diameter!

The Vintage pin is slightly larger diameter than the Trigo pin. So, with the Vintage pin, it fits tighter than a Trigo. The Vintage pin is shorter as well.

Still, Kirkham's external-hex pin will be a far better answer because then the stud won't have to be trimmed to get a wrench on the pin! Very big deal. Eliminates the top of the pin from splitting. Of course the Trigo taper error is the biggest discovery so far.
Regards,

LNJ

[Paul F]

David,

I don't think I want to ship an adaptor to you, but using a square piece of sheet metal, it looks like 90 degrees.