[sub6]

Okay, seriously, though. Everyone says that Cryofit works like this (essentially):

1: put the crown in the oven. This causes it to swell, making the hole bigger.

2: put the stanchions or steerer tube in the freezer. This causes it to shrink, making the tube diameter smaller.

3: put them together. As they cool/warm up, they will return to normal size and clamp the living sh!t out of each other.


Now, this makes no sense to me. If you put a donut-shaped piece of metal in the oven, it swells, which should make the hole SMALLER, not bigger. If you put it in the freezer, it should shrink, which should make the hole bigger (See Diagram).

So my question is this: is everybody's theory on how this works just a crackpot theory? Or is my diagram wrong? I've heard this theory a lot, and even heard it applied to headset installation, etc. Shouldn't you put both pieces in the deep-freeze?

 

[-BB-]

I've got a "real world" example of how it WOULD work.

One way of opening a "stuck" jar is to run the metal lid under Hot water so it will expand, thus making the seal looser.

Same would work for a crown.

I think it has to do with the diameter vs thickness.

Here is a mathmatical example:
Variable 1- Heating increases all dimentions by 10% (made up figure)

Starting Stats
Outer Diameter of hole = 100mm
thickness of walls = 10mm
Inner = 100mm minus 10mm = 90mm

Heat

Ending Stats
New outer Diameter = 110mm
Thickness of wall= 11mm
Inner Diameter = 110mm minus 11mm= 99mm

Inner Diameter increased by 9mm

 

[emmaman]

I haven't done the math/physics on that one, but I can understand your question.

I know when you change bearing on small enginge blocks it is done heating the block on a hot plate and the bearing pops rigth out and the new one goes rigth in. Cool the whole thing and the bearing is stuck where you want it.

 

[Brian HCM#1]

Putting this theory aside when people want to install a headset they can make a simple press for about $7 and not risk damage to any parts from heat.

 

[Brian HCM#1]

Originally posted by emmaman
I haven't done the math/physics on that one, but I can understand your question.

I know when you change bearing on small enginge blocks it is done heating the block on a hot plate and the bearing pops rigth out and the new one goes rigth in. Cool the whole thing and the bearing is stuck where you want it.

I have always used the proper tools to remove and install cam bearings. I feel the heat may distort them a little.

 

[-BB-]

Originally posted by Brian HCM#1
Putting this theory aside when people want to install a headset they can make a simple press for about $7 and not risk damage to any parts from heat.

Huh?

Isn't he talking about how an Arch fits to the stantions.

 

[steve]

Originally posted by -BB-
I've got a "real world" example of how it WOULD work.

One way of opening a "stuck" jar is to run the metal lid under Hot water so it will expand, thus making the seal looser.

Same would work for a crown.

I think it has to do with the diameter vs thickness.

Here is a mathmatical example:
Variable 1- Heating increases all dimentions by 10% (made up figure)

Starting Stats
Outer Diameter of hole = 100mm
thickness of walls = 10mm
Inner = 100mm minus 10mm = 90mm

Heat

Ending Stats
New outer Diameter = 110mm
Thickness of wall= 11mm
Inner Diameter = 110mm minus 11mm= 99mm

Inner Diameter increased by 9mm

I've got a real world example of somebody that should just SHUT UP!

 

[-BB-]

Originally posted by steve



I've got a real world example of somebody that should just SHUT UP!

Bring it on Biznitch!!

I gotta fist fulla PAIN and I'm saving it just for you!!
PUNK!!

(Drop me an e-mail some time... We'll do lunch.)

 

[sub6]

Oh boy, look what I went and started...

Anyway, what I'm saying is that if you have a bar (the 1st example in the pic) and you heat it up, it expands to the top, bottom, left, and right. If you wrap that bar into a circle, heat it up, what happens? It should heat up in the same way. The "bottom" of the bar is now the "inside edge" of the circle. So it should still expand inwards, tightening the hole.

Right?

 

[RideMonkey]

BB's explanation of this is correct.

 

[crashing_sux]

Your last example might make it easier for you to picture what happens. You mentioned heating a bar first, then bending it into a circle, and that the bar gets bigger in all directions, which is correct.

For some reason when you are thinking of it though you are not picturing it as growing in all directions, only width. If only the width increased then yes, the inner diameter would actually be smaller, but if the length also increased then you would have a longer bar. Take two pieces of metal, one 10% longer than the other and bend them into a circle and you'll see pretty quickly that the longer bar makes a bigger circle.

That's what the previous poster was saying, that while the width of the circle was getting thicker, as long as the diameter is growing faster than the width of the circle is then the inner diameter is going to still end up larger than it was previously.

It's one of those "two steps forward, one step back things". Seems like you're only seeing the one step back, but take another look at it and eventually it should make sense that you can take a step back and still make forward progress, as long as you take those two steps forward.

 

[sub6]

Originally posted by crashing_sux
If only the width increased then yes, the inner diameter would actually be smaller, but if the length also increased then you would have a longer bar. Take two pieces of metal, one 10% longer than the other and bend them into a circle and you'll see pretty quickly that the longer bar makes a bigger circle.

AHA!! And that, my friends, is why I'm not an engineer.:

Thanks for the explanation there folks, (esp. crashing_sux) - it actually makes sense now...

 

[-BB-]

Originally posted by crashing_sux


It's one of those "two steps forward, one step back things". Seems like you're only seeing the one step back, but take another look at it and eventually it should make sense that you can take a step back and still make forward progress, as long as you take those two steps forward.

You do the Hokey-Pokey and you turn yourself around... THAT'S WHAT IT'S ALL ABOUT!!

Just kidding...
Very good explanation.

 

[ohio]

Originally posted by crashing_sux
Your last example might make it easier for you to picture what happens. You mentioned heating a bar first, then bending it into a circle, and that the bar gets bigger in all directions, which is correct.

Bingo, it makes it easier if you picture a tube as being a flat sheet that's been rolled up. Then you can visualize how much greater the increase in length/diameter is over the width.

FYI: in the olden days of railway steam engines, the wheels were press fit onto the axles using a cryofit. There was NO key or spline. The press fit alone could handle all the torque a steam engine could output. But to get them off you had to have two guys pound on them with 20lb sledge hammers for a couple of hours.

 

[Dirt rider]

who cares about theory? it works thats all you need to know. my dad and granddad are both mechanics and they do this stuff all the time. when you have two different metals they expand and contract at different rates. you dont need much heat only 150degrees or so. it sure beats trying to carefully hammer parts together

 

[binary visions]

heh, well, I always want to know about the theories. It's great to know that something works, but if you know WHY it works, you can fix it if it goes wrong.. or improve it.. or figure out a better way!

 

[WTGPhoben]

when the atoms in the metal get heated they vibrate more, so that the space between atoms is greater. If you think of the string of atoms around the hole:

cold ( ).( ).( ).( )

hot: ( )...( )...( )...( )

now when you bend the string into a circle, which one is bigger?

the previous post about the reason the volume gets bigger is explained by this as well.

 

[Dog Welder]

Now this may just be the way they handle warranty's but when I took my JrT to mazocchi to get the mag crown repaired, they took it back into their warehouse and 20 min later they came out with a Bam arch in the place of the mag one. The mechanic told me not to ride it for one day as the sealant (aka loctite) they applied wouldn't cure for 24 hrs. Meaning that they didn't Cryofit s#it, they pressed on a new crown and that was it. This ain't a slam against Marzocchi but I'm just wondering if Cryofit is a marketing tool or are they actually cryofit and the press on stuff just for warranties.

 

[sub6]

Originally posted by Dog Welder
Now this may just be the way they handle warranty's but when I took my JrT to mazocchi to get the mag crown repaired, they took it back into their warehouse and 20 min later they came out with a Bam arch in the place of the mag one. The mechanic told me not to ride it for one day as the sealant (aka loctite) they applied wouldn't cure for 24 hrs. Meaning that they didn't Cryofit s#it, they pressed on a new crown and that was it. This ain't a slam against Marzocchi but I'm just wondering if Cryofit is a marketing tool or are they actually cryofit and the press on stuff just for warranties.

You're getting your crowns and arches confused. Crowns hold the stanchions; arches hold the lower legs.

Arches (i.e. BAM and Mag) are not cryofit to the lowers; they're definitely removable. Cryofit is used to attach the steerer to the crown, and the stanchions to the crown on singlecrown forks. And apparently on '03 Supers/Junior too.