Tungsten flywheels anyone?

[mmagliaro]

I had the idea, so I did some calculations and got a quote for the manufacture of
some 10mm diam x 7mm long solid tungsten flywheels with 1.5mm bore.
Those are the exact dimensions and bore of your basic NWSL brass 10mm flywheel.

There's no way I could machine tungsten, let alone bore a hole in it (centered, no less!)

AT THE BOTTOM OF ALL THIS, I have a question, bear with me.   And I'll tell you right off that I
have concluded this isn't worth it.  But I though I'd share my thoughts.

In brass, that flywheel weighs 4.8g
In tungsten, it would weigh 10.58g

A little physics:
the kinetic energy stored in the rotating flywheel (a good measure of its "flywheel-i-ness")

is:
1/2*I*w*w

where I = k *M*R*R

The units can be whatever you choose.  They will just control the units of the kinetic energy.

w = rotational speed in rpm
R= radius in mm
M = mass of the flywheel in g
k = constant depending on the flywheel's construction.  For a solid flywheel (i.e. not a thing
like a "ring" where all the mass is concentrated at the outside edge), k = 1/2

1/2*I*w*w
where I = k *M*R*R
So energy = 1/2 * 1/2 * M * R^2 * w^2

At 300 rpm:
For brass: 1/4 * 4.8 * 10^2 * 300^2 = 10,800,000
For tungsten: 1/4 * 10.58 * 100 * 300^2 = 23,805,000

In other words, the energy stored in the flywheel would about double.
The bad news is that getting these machined in a small quantity (say 50 or 100) would cost about $25 a piece!

That's a lot of dough.
The question is, would this really be worth it?  I am having a hard time grasping how much improvement
"double the energy" would make.
If the flywheel were 14mm instead of 10, the energy in brass would be:

1/4 * 8.79 * 14^2 * 300^2 = 38,763,900   (vs about 23M for a tungsten 10mm flywheel)

So going to tungsten is still nowhere as powerful as increasing from 10mm to a 14mm flywheel.

[basementcalling]

I think the answer depends on which locomotive (s) you are considering. Not sure Atlas/Kato quality engines need the improvement, though it would be interesting to consider in the NW & S2 models. Switchers would be the best candidates I would think, as they might see the most improvement in coasting ability, plus a heavier flywheel  is adding almost 6 grams of extra mass to the engine itself, which would help pulling power, and possibly electrical continuity with more weight to keep wheels in firmer contact.  And larger engines have two flywheels so the calculations would need to factor that in as well, though my math limits me to not knowing if that simply doubles the number you obtained.

I don't have the first idea how you would mount one, or replace an existing flywheel and keep it on the shaft, so I am no expert. I would also be leery of adding one to existing poor quality mechanisms. If there is a lot of slop,or friction in the drive train, I doubt the extra energy completely translates to motion of the mechanism. Another consideration is increased load on the motor, both weight and electrical? Would those be factors with negative impacts?

[jdcolombo]

I'm more interested in the weight than the energy.

If each flywheel is 10g vs. 4g (roughly), then you add 12grams for two flywheels (most diesels today have two), or about 4/10 of an ounce.   That's not insignificant; put a couple of quarter-ounce weights on top of a diesel and see how much more tractive effort you get.

IMHO, N scale engines are all about weight - the more the better, up to the point at which you blow up the motor because it can't handle the effort.

$25 is a lot, but there usually just isn't any other way to get that kind of weight addition in a hood diesel.  Maybe if you stuff the cab full of tungsten putty, but that gets messy.  $50 per diesel is a bit pricey, but for those of us who'd like to use a single GP7 on a local run, it might be worth it to convert a few (not all) of the fleet.

John C.

[peteski]

Since we are crossing into esoteric elements territory, why not go right right to depleted Uranium, a-la Jim FitzGerald?     Well, actually I am semi-serious.

[Santa Fe Guy]

Would we need lead aprons?

[strummer]

Yes, but you wouldn't need to worry about LEDs and the like, as they'd probably glow in the dark...

Mark in Oregon

[victor miranda]

the worth is a hard call. the extra weight would be welcome.

I can tell you you will notice the effect.

remember  I built a 3 flywheel gp20 chassis with a small motor.

it spools up slower for the smaller motor I suppose.
however that does not explain the far improved slow speed performance.

it was more reliable in all aspects of operations.

I set up the throttle to do a 10 speed roll and used a button to run the loco.
it worked well ... til I tried to haul a 15 car string.... I had to add more throttle.

so I would state there will be improvement for slow speed and the extra weight
will get much more control.

if they are out of balance, the shake will be an issue...

hmmmm,  I'd think your best bet may be to have them made
so they can be set in place of the Atlas flywheels.
and then the guys can use NWSL joints or dog bones.

that would be a fairly universal fit and application.

give what I have seen, I think you will sell ten pairs that way.

and I will buy a pair.  so that leaves 9. 

btw,  I think carbide drills will cut into machineable tungsten.

victor

[Skeebo]

As Tungsten Powder is available at a reasonable price from Golfsmith, could you save money with a hollow brass flywheel filled with Tungsten Powder?

[Chris333]

As Tungsten Powder is available at a reasonable price from Golfsmith, could you save money with a hollow brass flywheel filled with Tungsten Powder?

If you did that it would be lighter than filling it with lead...

[mmagliaro]

Yes, let's get all the other possibilities out of the way immediately.
Tungsten putty and powder are lousy options because by the time you account for the filler, they are less dense than plain
old lead.

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

As for mounting... That's why I would bore them for 1.5mm shafts because that is the shaft size of practically every
N Scale motor out there.    I wouldn't worry about mounting them.  Assuming you can press the flywheel off
a motor and press one on, it would be easy.  If you can't do that, you probably aren't interested in this.
They would hopefully be bored so they are a slip fit.  Pressing a steel shaft that won't "give" into a tungsten
hole that won't "give" might be darn near impossible.  I would be inclined to have them bored .001 or .002" over
1.5mm, and then slip them on with a drop of LocTite.

Although... Victor raises a good point about possibly machining out the hex holes so that they
could drop-in to Atlas or Kato diesels that use that design.  But I'm sure that would raise the cost a lot. 

I had not even though about the weight gain for traction, but yes, that is a nice bonus.

$25 each, though.   I just don't think it's viable.  It would cost $1000 to have 50 made and that's a lot of scratch.

[carlso]

Interesting Max.

I have a question and that is are the motors typically used by the major N scale manufacturers strong enough to spin such a flywheel for any long lengths of time as in a show. Would the motors longevity be in jeopardy ? ?

Just curious cause I'm not smart enough to figure that out.

Carl

[peteski]

The only load on the motor is when it changes the speed (overcoming the inertia or angular momentum or something similar).  I'm not up on my physics definitions, but once the flywheel is spinning it needs almost no motor's power to keep it running.

[jdcolombo]

that would be a fairly universal fit and application.

give what I have seen, I think you will sell ten pairs that way.

and I will buy a pair.  so that leaves 9. 

btw,  I think carbide drills will cut into machineable tungsten.

victor

I'd buy 3 pairs.  Would send money up front (to Max; not to just anyone!).  I can imagine using these to replace the brass flywheels on 3 of my Atlas GP7's to use in local service; the extra weight is the difference between prototypical (a single engine) vs. what I currently need to pull the train (two).   $50 per engine as an upgrade would be worth it, I think.  Heck, I've spent $100 per engine adding sound . . .

John C.

[victor miranda]

I did not have a hex shaped hole in mind.
I thought round like the gp-15 has.
I also recommend that the fit be slip fit and that red or blue loc-tite will hold it. 
I have not had to use anything except blue for flywheels yet

I wanted to try this a while ago and could not find 10 mm rod or disks.
... or 12.

I think it would be  a question of can it be drilled...

victor

 

[peteski]

I would be cautious if drilling the shaft hole yourself. If it is not perfectly centered the flywheel will be out of balance and will have some serious vibrations (your model will become a personal massager).