Tungsten flywheels anyone?

[u18b]

As I began reading through this thread, my first thought at the interesting proposal was the same as Max.

Steel is harder than brass.

So when a brass flywheel is pressed onto a steel shaft, the brass "gives" a little.  We are only talking microns at best, but it is still there.   If a brass flywheel is pressed and removed enough times, you may find the hole has widened enough that a shaft will not hold it tight any longer.

So what if we pressed a Tungsten flywheel?

The Tungsten would be harder than the steel.  It would not give, and instead the steel shaft would have to "give" to the flywheel.

In fact, if the flywheel were ever so slightly TOO tight, the danger would be a bent motor shaft.

I'm not saying it would not work, but I am thinking the tolerances would have to be perfect.

[nkalanaga]

As with the others, I'd be more interested in the extra mass.

Depleted uranium has the same density as regular uranium.  It's just had the U235, the fissionable stuff, removed.  Uranium isn't dangerously radioactive, and would probably be quite safe inside a locomotive, but one wouldn't want to have it against the skin for too long.  It's sometimes used for radiation shielding, where the density can stop high-energy radiation, and the low-energy. low level natural radiation isn't a problem.
https://en.wikipedia.org/wiki/Depleted_uranium

The big problem with uranium is that it's easily ignited.  Even ordinary machining can get it hot enough to catch fire.  Not the easiest stuff to work with, but I doubt that it would ever get that hot in a locomotive, even if the motor stalled. 

[peteski]

Tungsten is actually slightly more dense than Uranium, although I don't know about depleted uranium.

That was a tongue-in-cheek comment (hence the smiley).  But to be honest I didn't know that uranium was less dense than tungsten.  I didn't check.  I just recall Jim FitzGerald's monster N scale locos filled with depleted uranium pulling very long trains on the Ntrak layouts.  I also recall reading somewhere that depleted uranium was used as counterweights for flight-control surfaces on Boeing 747 Jumbo Jets.

[nscaler711]

Instead of pressing the flywheels on the shaft, why not set screws?
RC guys use them all the time and they work great, I have yet to see any of my pinion gears just fly off...

[peteski]

Instead of pressing the flywheels on the shaft, why not set screws?
RC guys use them all the time and they work great, I have yet to see any of my pinion gears just fly off...

The hole for that set screw will unbalance the flywheel. Might be enough to create undesirable vibrations at higher rpms. Plus, the screw would have to be pretty small for a 1.5mm shaft.

[nscaler711]

It may, but it may not too. None of my pinion gears are unbalanced due to the set screw. Its all about design. If you design a divot exactly 180° from the set screw you could effectively eliminate any "balancing" issues.
And I have seen some tiny, tiny set screws before lol.
But it is a better option than forcing your flywheel onto a already tiny shaft.

[mmagliaro]

That was a tongue-in-cheek comment (hence the smiley).  But to be honest I didn't know that uranium was less dense than tungsten.  I didn't check.  I just recall Jim FitzGerald's monster N scale locos filled with depleted uranium pulling very long trains on the Ntrak layouts.  I also recall reading somewhere that depleted uranium was used as counterweights for flight-control surfaces on Boeing 747 Jumbo Jets.

No worries.  I knew it was a joke.  But I also knew that in fact Jim Fitzgerald actually used it.   I do wonder why.
Tungsten is heavier, and it doesn't have all the "scary" associated with the uranium.
  I supposed he was able to get his hands on the uranium easier!

[peteski]

It may, but it may not too. None of my pinion gears are unbalanced due to the set screw. Its all about design. If you design a divot exactly 180° from the set screw you could effectively eliminate any "balancing" issues.
And I have seen some tiny, tiny set screws before lol.
But it is a better option than forcing your flywheel onto a already tiny shaft.

First of all, nobody is talking about forcing the flywheel onto the shaft - Max wanted to make the hole slightly oversize and Loctite the shaft to the flywheel.

Pinion gears are not flywheels - they are much lighter overall so even if they are slightly out of balance, it is not a big deal.  The set screw is usually in a small-diameter collar of the pinion gear (it doesn't affect the overall balance of the gear all that much).

Tungsten is also very expensive to machine (as it was mentioned earlier). Even if a set screw fastening method was feasible, drilling a set screw hole through it and then tapping a thread in that hole would raise the price by quite a bit.

[peteski]

No worries.  I knew it was a joke.  But I also knew that in fact Jim Fitzgerald actually used it.   I do wonder why.
Tungsten is heavier, and it doesn't have all the "scary" associated with the uranium.
  I supposed he was able to get his hands on the uranium easier!

I suspect that was exactly the reason.

[rrjim1]

Tungsten really isn't that hard to machine, you just need C-2 grade carbide tooling, and the right Tungsten Alloy.
If you want to increase flywheel weight just a little and a lot cheaper one could also use a little heavier Bronze Alloy.
I have pulled and installed a lot of N-scale flywheels and always use 620 retaining compound, it's half strength unless you heat harden it. Holds great and a lot easier to remove.   

[Chris333]

Tungsten alloy means tungsten plus something else that isn't tungsten.

I had parts machined that were 90% tungsten, 7% nickel and 3% iron. It was 17.12g/cm3 dense. Pure tungsten would have been 19.25g/cm3.

  And since we are talkin'. Tungsten poweder would be 4.5g/cm3:
http://www.tungstenheavypowder.com/Tungsten_Heavy_Powder/Tungsten_Powder_Applications/tungsten_powder_applications.html


I say make a flywheel out of a material that reduces the gear ratio by 4 

[nscaler711]

First of all, nobody is talking about forcing the flywheel onto the shaft - Max wanted to make the hole slightly oversize and Loctite the shaft to the flywheel.

Pinion gears are not flywheels - they are much lighter overall so even if they are slightly out of balance, it is not a big deal.  The set screw is usually in a small-diameter collar of the pinion gear (it doesn't affect the overall balance of the gear all that much).

Tungsten is also very expensive to machine (as it was mentioned earlier). Even if a set screw fastening method was feasible, drilling a set screw hole through it and then tapping a thread in that hole would raise the price by quite a bit.

Have you used a flywheel puller? i suspect that you havent, cause it takes a bit of force to pull the flywheel off the shaft of a motor, therefore you would still have to use force to put one back on.

oh and secondly a unbalanced pinion gear can affect alot of things... like oh i dont know wear and tear of gears... and hmmm the bearings in a motor...
go ahead ask me how i know....

sure tungsten is expensive to machine but its not hard, but as Jim said

Tungsten really isn't that hard to machine, you just need C-2 grade carbide tooling, and the right Tungsten Alloy.

and I've done that too....

(also its easy to add two different quotes in one reply...)

[mmagliaro]

I am not proposing that these flywheels would need to be pressed on.
Brass flywheels usually have to be pulled off motors with a puller because they are tightly press-fit on there.
But they don't have to be.  Once the existing flywheel is pressed off, the tungsten one can be
slip-fit on there.   A slip-fit flywheel works perfectly fine.  It just can't be loose.  It's all a matter of
making it so it presses on with only finger pressure. 

[victor miranda]

No worries.  I knew it was a joke.  But I also knew that in fact Jim Fitzgerald actually used it.   I do wonder why.
Tungsten is heavier, and it doesn't have all the "scary" associated with the uranium.
  I supposed he was able to get his hands on the uranium easier!

no matter what anyone says,
I find the uranium story hard to believe.
uranium is a lot of fuss to machine.

It is quite possible it is true. 


I keep thinking that if the loco frame were made of cast gold....
it would weigh the same and would have been much easier to build.

and frankly I would not want to tell any one I had that much gold in an n-scale loco.
so I would make up a story.

even uranium is not an inexpensive metal.


given the price of brass locos they are getting into gold weight value.

victor

[C855B]

All the joking aside, DU (what depleted uranium is called in the trade) is insanely difficult to machine. The shavings have a tendency to catch on fire, spectacularly. I was slightly involved in a project about 20 years ago machining - of all things - a DU shifter knob for a specialty sportscar, where the extra mass smoothed the shift action. There was one prototype made because we had access to the DU, as the progenitor of the project happened to be a nuclear engineer. They went into production with something else (I forget what, but not tungsten) which was very nice, but the project certainly was an experience of dealing with DU. Not fun, and despite the humor/cred/eyebrow-raising aspect of DU, tungsten has better density, anyway.