Transferring 500 degree locomotive wheels

[EOsteam]

Hello again!
I need to press in the crank pins into my 10” diameter locomotive wheels. My plan is to heat soak the drive wheels at 500 degrees and then use an arbor press to push in the crank pins. My question is what kind of mitts to wear when transferring the wheels. Oven mitts seem a little thin and it is fair distance from the grill down some stairs and in between the two buildings, open a door and place the wheel on the arbor press. I’ll probably use a cookie sheet to transfer but I’m still going to have to handle it a bit. What are some good options for heat rssistant mitts?

Thanks,
HJ

[NP317]

Instead of heating the driver wheels, cold-shrink the pins instead.
You can do that near the press using dry ice in a cooler. Easily transfer the pins with tongs of some sort.
That's what I did.
RussN

[liveaboard]

You'll lose a lot of heat carrying the work that distance; really you just have seconds, not minutes.
I pull the piece from the oven, put it on a block of wood, and tap the fitting in with a hammer.

Even then, sometimes I had failure when the pin heated and expanded before I finished.

My experience; just use the arbor press cold, calculate the fit to need plenty of pressure and squeeze it in there.

As for the original question; you need Kevlar gloves, get them from a ceramic supply store.

[Bill Shields]

Chrome leather welding gloves have worked for me.

Agree on other suggestions...not the least of which I am not convinced the hole in question will open as much as you are expecting

Freeze pin, chanfer lead edge, lube with white lead and press in place (!not in that order)

[Inspector]

What would it take to move the press up to the grill? Then you can use the dry ice and the heat.

Pete

[gwrdriver]

I would listen to all those who have advised chilling the pins and leaving the wheels warm at best. IMHO, in non-industrial circumstances, and by that I mean where specific gear for handling such heated material isn't usually on hand, it's best to eliminate every possible chance of things not going as expected. Murphy says . . ."If anything can go wrong, it will." My observations and experience bears this out.

[Harold_V]

The one fly in the ointment where chilling the pin as opposed to heating the wheel is concerned is that one is limited to the amount of chilling. You may or may not be able to chill the pin adequately to facilitate assembly without problems. If you can't, it's not worth the risk of damaging good components. Heating the wheel permits extra clearance and buys time. If it's done properly you don't need a press of any description---just good handling. When the wheel is properly heated and the pin chilled, the pin should be able to be placed in the hole by finger and set to full depth before any shrinkage occurs. If that isn't the case, it will be a crap shoot. I'd recommend chilling the pin in any case, but heating the wheel, too, just as if the pin was not cooled. The additional clearance generated will buy time and guarantees a good end result and may spell the difference between pins that are erect or tilted. That's almost always a problem when you choose to assemble press fits.

Of little importance, but a reason to understand proper heating. Many years ago, before being self employed, I worked, briefly, at a shop where huge submersible sump pumps were manufactured. The shaft was made of 3-15/16" diameter cold rolled steel with a Hastelloy sleeve applied as a bearing. The sleeve was machined for a shrink fit on the shaft. It was then heated red hot and slid on the shaft (about five feet down) to a stop. This was done by hand, using asbestos gloves (they were legal then). Once one of them seized before seating. The only way to remove it was to machine it away. With a wall of about 5/16" thick and a length of about ten inches, you might understand that that was an extremely difficult operation to perform. If you haven't machined Hastelloy, count yourself fortunate.

H

[Bill Shields]

Harold ..was the heated houle in the centroid of impeller or off center as this crank?

Like you, I have put 100's of impellers on shafts using that method

However the degree of opening of the specific hole in question is going to be less than expected.

Someone with a finite element analysis application can actually run this and see how much the hole in quesion should open...my experience tells me it is not going to be enough.

[Harold_V]

Harold ..was the heated houle in the centroid of impeller or off center as this crank?

The sleeve was a simple cylinder, which was rough machined on the exterior, and finish machined on the bore. It was machined to size after it was installed, as it would have been difficult to control the diameter otherwise. At red heat, it was a rattle fit on the shaft. So long as there was a stop set to locate the sleeve where desired, it installed effortlessly. If, however, there was no stop, the short amount of adjustment time for proper location resulted in the sleeve seizing where it wasn't wanted.

I can still remember what it was like removing the sleeve. I have often jokingly commented that about as much came off of the carbide being used as came off the sleeve. It's miserable stuff to machine.

To avoid touching the shaft, the final removal pass I took left a sleeve about ten thou thick. It was then lightly scored with a sharp chisel. When it released it was with gusto! The sleeve ended up in a nearly perfectly flat condition, much like some thin sheet metal. The shrink provided was quite high. Ten thou sticks in my mind.

What was really interesting was the amount of contraction in a linear direction. The stop had to be located quite a large distance from the actual location due to the amount of shrinkage from the high temperature involved. I do not recall the amount.

However the degree of opening of the specific hole in question is going to be less than expected.

Someone with a finite element analysis application can actually run this and see how much the hole in quesion should open...my experience tells me it is not going to be enough.

Coefficient of expansion for cast iron is accepted to be .00000655". Heating to 500°F should provide about .003" expansion. Another 100° for insurance shouldn't be troublesome, assuming it was needed. By cooling the pin, I suspect that an acceptable fit would be easily achieved. Am I missing something?

H

[Bill Shields]

Expansion in which direction?

If you are heating a disc, then the entire disc will expand outward that amount.

It is safe to assume that a hike in the center of the disc will grow symmetrically by that amount, as long as you are patient. I have seen large pump impellers with their bore actually shrink if you heat incorrectly and get more heat on near the center than around the periphery

Is it safe to assume that a hole that is not centered will grow symmetrically about the center of the hole?

Not so sure about that.

It may be a moot point, and enough asymmetric hole opening may well occur to get there

Point I am making is just do not assume that what happens at the center or periphery is the same as elsewhere.

[Harold_V]

Got it! And I agree. However, if a wheel is heated on a barbeque grill (or even better, a heat treat oven), pretty good chance it will heat somewhat uniformly, so expansion should be reasonably uniform as well. I can see the potential for a problem, but I can also see that done properly, this method would be superior to others. Any time you can insert a piece into another without expending any pressure you've gained huge territory, as it's bound to be self aligning. If one can eliminate the need for pressing, it's a big step towards a better end result.

If, however, the home shop type had the capability to hone the hole and grind the pin, including a lead so it would self start, none of this would be necessary, assuming one had the means to properly align the pin (vertically) and press uniformly without introducing and side pressure, which, in turn, results in a tipped pin. How many readers does that describe? Precious few.

A comment on precision turning. I've done more than my share of that, and I spent years in precision grinding. Unless one owns a high speed lathe with exceptional bearings, don't think for even one moment that you can turn a piece that rivals a ground piece. It simply can't be done. That's not to say that a functional piece can't be made, for it can. It just has its own problems, including an inconsistent diameter and out of round conditions that lend themselves to less than desirable end results. You can see what I'm talking about by grinding a part that is considered finished that has been created on a lathe. Grinding doesn't lie to you---it exposes the smallest of errors.

As much as I'm not a fan of LocTite for such procedures, it makes more sense than trying to press a poorly prepared pin and hole. It, like a proper shrink fit, should eliminate the perpendicularity problem.

Just sayin'

H

[Bill Shields]

Every loco I own and have built is held together with Loctite. This includes drivers without keys.knowbit goes against the grain for us old timers, but hey....we do not use carbon steel cutting tools either

Pressing a pin straight is not a big deal. I use a recessed sleeve that holds the pin and slips up over the end of the press.

Ever see how they pressed crank pins in on full size locos?

Now, I have to admit that shrinking tires on drivers is not something that I do with Loctite.

Sure...the Loctite will hold, but when you chuck the wheel into the lathe to finish the tread and flange..... sometimes things get a little hot.