ScaleTrains GP30 Arrival (End of January)

[pjm20]

You guys talk about using tungsten weights. What size do you use, where can you get it, and what does it cost? looking on the 'net is confusing.

I'd start with McMaster Carr

[lock4244]

Thank you for the first hand account. 31 cars is better than I expected for a pair of them.

Rob

No problem. Train was a mix of ATH, BLMA, FVM, IM, NARC, Rapido, ST, all cars 50, to 60', all wheels are metal.

[sizemore]

I'd start with McMaster Carr

You can get cube, strip and chip Tungsten from any good Pinewood Derby place. The place I use is below:

https://www.ebay.com/str/txchemisttungsten?_trksid=p4429486.m3561.l170197

The S.

[robert3985]

WARNING - THREAD DRIFT

...While I'm not an audio engineer, to me your explanation is an oversimplification.  Not only the sound from a floating speaker appears not as loud, because as you mentioned the air movement from the front and back of the cone or diaphragm cancel each other out, but due to the speed of sound waves in the air, there is a more complex interaction action than just cancellation. Depending on the specific frequency (wavelength) some frequencies could actually be amplified, while others cancelled almost totally.

@peteski...Peter, I'm a simple man, and I too am not an "audio engineer" and have no instrumentation to measure frequencies coming out of a speaker mounted in any of my engines.

And, while I, as always, admire your critical thinking, I have a "story" about why my statement is "simple", but not "simplified".

My experience was with installing speakers in my new Kato E9's by milling a large hole in the big chunk of zinc alloy located at the rear of the chassis to allow a press-fit of a round downward firing speaker into it.  After finishing the installation, but before sliding the body back onto the chassis, I needed to test run it, and the sound was extremely low...almost too quiet to hear (admittedly, my hearing is not the best!).  I fiddled with the decoder's volume settings which didn't help, and I was very disappointed in what I thought was the decoder's sound performance.

At this point, I wanted to run my newly purchased COLA consist, so I slid the fairly tight fitting body back onto the chassis and set the engine on the rails...and was completely surprised at the LOUD volume of the sound coming out of it!

I ran it around my yard a bit to enjoy the sound, and actually turned the volume down to a tolerable level.  I decided to slip the body back off to see if THAT was the reason for the volume change, and sure enough...just the chassis, with the downward firing speaker, and with the mounting hole being milled completely through the chassis...was exponentially quieter than with the body mounted to it.

Photo (1) - Kato sound decoder/speaker installs on my Kato E9's:


I decided to turn a brass plug for the top of the hole to make it literally air-tight, and with the plug tightly in the top of the mounting hole, the volume was even louder than with just the tight-fitting body mounted over the chassis.

I am sure that the totality of both volume and frequency response were affected, but practically, the volume without the body on over the hole or without the air-tight plug inserted was so low, I couldn't compare frequency responses with my ears because I could barely hear it...so, my experience was "simple".

Yup...my statement is correspondingly simple but practical, and is not "over simplified" any more than saying something tastes delicious without analyzing the chemistry of exactly why it tastes deliciously...it just does.

Cheerio!
Bob Gilmore

[C855B]

... Doing the calcs, solid lead in that space would yield 0.334 oz., or a ~15% increase in total weight. Worth the effort alone.

For once in my life, the calculations matched reality. The bare GP30B chassis was 0.190 oz, with the lead filling the speaker space, 0.233. Made a remarkable difference in smooth operation.

Did the same mod to a ST SD40-2, increasing its weight by the same amount, but didn't have time for A->B testing. Problem previously reported was lack of traction.

Oh... here's a news flash - powdered tungsten is a waste of time and money - in the SD40-2 speaker cavity, it only added 0.11 oz.

[Chris333]

Lead is heavier than tungsten powder or tungsten putty.

[dem34]

Lead is heavier than tungsten powder or tungsten putty.

And if one feels uncomfortable with powders and castings. Birdshot with a little white glue goes a long way.

[C855B]

Lead is heavier than tungsten powder or tungsten putty.

Yep. My surprise was in just how volumetrically inefficient the tungsten products are.

Question for @sizemore - that Pinewood Derby supplier. Have you used their 1/8" tungsten cubes? If so, how much do 15 cubes weigh?

And if one feels uncomfortable with powders and castings. Birdshot with a little white glue goes a long way.

It might, but there's still the air space issue. I used lead sheet cut to fit. @GM50 4164 did the same.

[GaryHinshaw]

Tungsten has a density of ~19 g/cc, so a 1/8" cube has a mass of 0.6 g, and 15 cubes is 9.1 g = 0.32 oz.  Sadly, you only get one layer deep with 1/8" cubes, giving you a filling fraction of 57%.  You'd have ~0.05" of height leftover to squeeze a thin sheet of lead, if such exists.

[C855B]

Tungsten has a density of ~19 g/cc, so a 1/8" cube has a mass of 0.6 g, and 15 cubes is 9.1 g = 0.32 oz.  Sadly, you only get one layer deep with 1/8" cubes, giving you a filling fraction of 57%.  You'd have ~0.05" of height leftover to squeeze a thin sheet of lead, if such exists.

Problem with the straight-across density calc here is the cubes being offered are an alloy, not pure W. That's why I had to ask about the sourced cubes. From previous research, I'd guessimate about 10% something else, like nickel or copper. Tungsten is next to impossible to tool and especially cast, so my presumption is alloys are used for commercial purposes.

But you're right, cubes plus a strip of 1/32 Pb sheet would just fit ST's speaker enclosure and tip the scales a few grams in favor over just lead. Lead has the hazardous factor (gloves, wash hands, don't eat), but in thin sheet form is sooooo easy to cut with heavy scissors.

If I were the enterprising type, I'd 3D print molds to cast lead weights that are drop-in for the ST speaker housing, similar to what serious fishermen do with casting line weights. A precision fit would gain a gram or two or three. But I've been down the kitchen-table sales operation before, and what it takes to support that is too far removed from hobby enjoyment aspects.

Amusing related anecdote - many years back, I was in a sports car club, and we collectively determined that a weighted gear shift knob was the solution to some of our complaints about vague shifter action in amateur competitive racing. One of the guys was a machining hobbyist, and started playing with billets of various metals. He gave up almost immediately on tungsten, but since his real job was in the nuclear field, he had access to depleted uranium. His main concern, realized once on his lathe, was that DU shavings would catch on fire if machined too aggressively. He eventually took his metal knob production semi-commercial, but the DU version didn't go beyond his prototype.

(Also, there's "Cotton Brute", a hacked N scale loco used to set a pulling record. It also used DU.)

[Chris333]

Tungsten cubes are an alloy. 100% Tungsten is 19.25g/cm3. 100% Tungsten is very hard to cut.

[GaryHinshaw]

Right, so probably 8 g instead of 9 g.  But how is the loco doing now with the lead?  Good enough?  [Better is (can be) the enemy of good enough.]

[C855B]

Right, so probably 8 g instead of 9 g.  But how is the loco doing now with the lead?  Good enough?  [Better is (can be) the enemy of good enough.]

Oh, much better. It's definitely a plan for the other nine. Need to determine how much room there is above the electronics for maybe a little more, but what's in the fuel tank definitely qualifies as "good enough" in that it solved the main concern.

As far as the SD40-2 test, we didn't leave the house today just not wanting to get out in the cold (4°C) drizzle. Maybe tomorrow.

[sizemore]

Question for sizemore - that Pinewood Derby supplier. Have you used their 1/8" tungsten cubes? If so, how much do 15 cubes weigh?

They're on a backer and saving them for some Kato RDC work, so I haven't used them yet. Sixty 1/8" cubes comes out to 1.044oz or 29.74g. A single 1/4" cube come out to 0.166oz, 4.70g. They mathematically don't work out exactly, eight 1/8" cubes come out to ~4g vice 4.70g for the 1/4" cube, so smaller cubes are either a different alloy or dimensionally untrue (or both). However, the size to weight convenience is pretty nice, using the 1/4" cubes to bring up car weight to NMRA standard.

HTH,
The S.

[Chris333]

Not sure exactly what those cubes are, but the way they are slightly rounds seems like an alloy. 

When I had tungsten weights made for my 44Tonner it wasn't pure tungsten, it was 90% so they could machine it easier. 90% is 17.12g/cm3, 7% nickel, and 3% iron.

I would *guess* the cubes are better than lead and they pack tight.