bulthisl

[quote author=wannadiesel link=board=7;threadid=16839;start=0#157880 date=1057711672]<br>OK, I guess I'll have to tell my customers who use liquid nitrogen to shrink 2 foot diameter gears to get them on shafts to stop it, they're violating Gary's laws of physics and wasting a heckuva lot of liquid nitrogen. Believe me, it blew my mind the first time I saw it. The wagon tire analogy doesn't apply here, because of the relative thickness of the metal in the two different planes. Say the thickness of the tire is about 1/4 inch, the &quot;length&quot; of the tire is probably around 150 inches. When the metal expands 1% in all directions with heat, obviously the 1% of 150 inches will have more of an effect on the size of the hole in the middle than the 1% of 1/4 inch. Now when we're talking about a 2 foot diameter gear with an 8 inch diameter bore, the metal still expands in all directions. This makes the 8 inch hole smaller, by 2% if we're going by the expansion given in the wagon tire example. This is also why engines have tighter clearances when warmed up, the bearing bores get smaller and the shafts get bigger. It's hard to wrap your brain around it, but it's the way the world works. As to why the heated bearing or small gear works, see the wagon wheel example. Same thing happening on a smaller scale.<br>[/quote]<br><br>Maybe they are freezeing the shaft.<br><br>I heat gears and freeze shafts all the time to get them to work.<br><br>A starter ring on a flywheel will get bigger and fall off when heated.<br><br><br> : Eddie : 8)

Mexstan

Generally I agree that the physics of a flat plate and a cylinder when heated do not change when heated. However, perhaps I should have stated something differently in my original post when I foolishly entered this fray. When a flat plate is heated it is free to expand or contract on a flat plane. When this same plate is formed into a tube of ball then the expansion/contraction forces tend to fight one another SLIGHTLy. I used the word physics to discribe this change. That was the wrong word. Sorry. The PHYSICS do stay the same, just the forces acting within the material change a LITTLE. Does this help? Am I vindicated now?

tmiller24

I'm betting that the probe will expand initially,due to being directly in the hot gasses, this will seal the leak! Then shortly after the manifold will expand,as it soaks heat and the clearance will return in the assembly. this will happen, probably for several weeks, until the hot gasses that do escape the joint, erode the cast iron and cause the probe to become too loose, to stay in place. How about a fresh can of Worms!! : :P

redramnc

How does he know if the probe is properly located (vertically) in the manifold? If I remember my pyro fitting keeps the probe up about a half inch due to the shoulder of the probe seat.<br><br>Sure this guy isn't a converted Chebbie guy? Sounds like some of the wrenching that one of them would do

KATOOM

<br><br>Now thats a guy with some vision.

WHIFF

Now that this has been thoroughly cleared up , how about the original question???<br><br>[quote author=barracuda link=board=7;threadid=16839;start=0#157829 date=1057703517]<br>i stopped at my local auto parts store today and bumped into a fellow CTD owner...had an 01' w/ a 4&quot; exhaust and a k&amp;n filter...no other mods EXCEPT...he installed a pyro gauge, he drilled into the manifold at the correct spot but he drilled a hole the size of the probe and dropped it in...it seemed to be tight but could anything happen because of that?? the guy was pretty cool and i told him about our site, i told him i would post and give him a call to let him know....What do ya think??<br>[/quote]

Mexstan

Gary, now you done did it. After everybody reads your post they are going to be messed up for ever!!! Hope you are proud of all the mayhem you have caused.

Shovelhead

[quote author=Gary - KJ6Q link=board=7;threadid=16839;start=45#160282 date=1058312059]<br>[quote author=Mexstan link=board=7;threadid=16839;start=#160281 date=1058311828]<br>Gary, now you done did it. After everybody reads your post they are going to be messed up for ever!!! Hope you are proud of all the mayhem you have caused. <br>[/quote]<br><br>Hey, I'm always eager and willing to step in and help clear things up... <br>[/quote]<br><br>You could always get a job with the CIA giving info to presidential speech writers. ;D

KATOOM

<br>Gary, I cant believe it took this long to get through to you! I knew you would crack sooner or later. ;D<br><br> <br>We all agree that a gear will go over a shaft easier when heated. Especialy if the shaft is subject to cooling. It's just that not everyone agree's on the expansion tendencies of a exhaust manifold.

Edward

Can I try another approach here?<br> When you heat metal it expands over all of its surface area. A plate of steel will get thicker, longer and wider because it expands over all of it's surfaces. A hole has a surface area also it is called circumference. As metal is heated the circumference of a cylinder will get larger as that surface also expands.<br><br>Edward

KATOOM

<br><br>Good point but this fact also depends on if the plate is restrained or free to move in any direction.

Edward

<br><br>Katoom<br>The result of restraining metal and attempting to stop expansion and contraction during temperature changes is metal fatigue. Fatigue causes cracking much like the stock cast iron exhaust manifolds have a tendency to do. Which shows metal will move during heat cool cycles even if that means cracking to allow that movement. The success of the three-section exhaust manifold sold by ATS is a great illustration. The two expansion joints in this manifold eliminate the metal fatigue that causes cracking. <br><br>Edward<br>