Pulling Power Test

[nkalanaga]

Randgust:  To go with your repowered FP45/SD40-2, I have four W&R brass F45 shells on Kato SD40 chassis.  No added weight, but they pull very nicely.  The originals would pull, but their odd spring-mounted trucks wouldn't stay on my track.  The Kato chassis works fine, with some masking tape for insulation.

[NtheBasement]

Another data point from when I converted a few DC engines to DCC and I sent the frames in to Aztek for milling.  Due to the loss of weight the standard up-grade mine run went from 15 hoppers to 12.

I spent a lot of effort adding weight back in and where you add weight is critical.  Via experiments with balancing coins on various places on the loco, adding weight to the nose helped most.  I imagine the front wheels slip first because the center of gravity puts more weight on the rear truck, and once the first wheel slips it instantly cascades to all wheels because they can't take up the loss of traction.  Adding weight to the rear of the rear truck was actually counter-productive.

[rickb773]

The LL plastic frame FA-2s were the real stump pullers.  The metal frame FA-1 and FA-2 were not far behind.  I notice that Original Poster does not mention them. Perhaps neither the Penn nor Reading Company ran FAs on the PRSL?

The PRSL was the unwanted stepchild of the PRR & Reading. In the 1950s both parents dumped all their dying steam engines there for their last years of service.

The dumping continued with the first generation of diesels, so they had misc. RS3, Sharks, and FAs floating around. Anything could show up.

That continued dramatically when Conrail took over. There is a story of an E-L RS3 catching fire on a run and the engineer asked the local townspeople not to call the fire department immediately so it could "cook" a while. (The E-L RS3s were in such horrible condition when they arrived that the engineers did not want to take them out on the road.)

Conrail became Conrail Shared Assets during the CSX-NS Southern merger so now we even get to see the NS heritage units occasionally.

But to answer your initial question, I could not get any of my DC FAs to run for the test.

[Maletrain]

Looking at the table, it seems a little pessimistic with respect to what a 2.2 ounce loco that I use at our club actually pulls.  It is a little Atlas S-4 with sound, and it surprised me with its pulling ability.  It easily runs up a winding grade that peaks at 4% with 9 hoppers plus caboose, and pulls a string of 18 hopper plus caboose while switching through a turnout on level, mostly straight track.

I think that pulling tests done on the basis of the number of cars can easily be misleading, because there is such a difference in the rolling resistances among various car types and manufacturers.  rickb773 posted that he used mostly Micro Trains box cars, but added some Atlas cars, too.  While MTL box cars consistently roll better than most, Atlas has more resistance and more variation in their various rolling stock.  I have replaced Atlas plastic wheels with metal wheels specifically to get less rolling resistance in long trains.  And ESM metal wheels roll with noticeably less resistance to anything else, including MTL Delrin wheels.

Plus, on uphill grades, the weights of the cars themselves is a significant parameter.  Unless they are all weighted to a standard, it is hard to translate from one person's measurements to another person's needs.

Has anybody toyed with making an actual dynamometer car in N scale?  It seems like the technology is available, and solid state strain gauges are cheap.  But, building the circuit to fit on an N scale car and deal with the coupler slinky noise in the measurements seems like a substantial development project.

[jdcolombo]

Folks, it's all about weight first, and wheel adhesion second.  Add a traction tire to a wheelset and pulling power will instantly improve, but if the model lacks weight, the wheels will still start to slip with modest consists even with traction tires. 

The old plastic LL PA-1's had these huge lead weights over the front and rear trucks, and those things would pull 40 MT 40-foot boxcars on flat track without breaking a sweat.  Older engine frames were made with a different and heavier alloy than newer frames, due to changes in environmental regulations.  My old Atlas/Kato SD9's drastically out-pull the newer (non-sound) Atlas SD-9's from China; the Kato frames are significantly heavier than the new ones.

Too bad it is so difficult and expensive to machine tungsten.  Wonder what a tungsten frame for one of the new Atlas GP7/9's would weigh, even with the cutouts for a speaker and sound decoder . . . 

John C.

[peteski]

Too bad it is so difficult and expensive to machine tungsten.  Wonder what a tungsten frame for one of the new Atlas GP7/9's would weigh, even with the cutouts for a speaker and sound decoder . . . 

John C.

There is an alternative to machining tungsten.  I have a tiny N scale  British 0-6-0 Terrier loco. It is made by Dapol.  I has tungsten metal weights but they are not machined.  Under close examination they appear to be formed in molds under extreme pressure from probably powdered tungsten.  I have seen this production method used for steel parts (like a gear for my RotoZip grinder attachment).  I don't know what this manufacturing process is called but it exists.

So it should be possible to produce complex-shaped metal chassis made of tungsten without machining, but I highly suspect that the lack of knowledge about the process' existence at the model manufacturers, or even more likely the higher cost of the process are what prevents it from being more widely utilized for model locomotives.

[nickelplate759]

There is an alternative to machining tungsten.  I have a tiny N scale  British 0-6-0 Terrier loco. It is made by Dapol.  I has tungsten metal weights but they are not machined.  Under close examination they appear to be formed in molds under extreme pressure from probably powdered tungsten.  I have seen this production method used for steel parts (like a gear for my RotoZip grinder attachment).  I don't know what this manufacturing process is called but it exists.

So it should be possible to produce complex-shaped metal chassis made of tungsten without machining, but I highly suspect that the lack of knowledge about the process' existence at the model manufacturers, or even more likely the higher cost of the process are what prevents it from being more widely utilized for model locomotives.

I think that's called sintering.   

[peteski]

I think that's called sintering.

That would make sense.
Usually I see sintered brass bearings in many older models, used as motor and worm shaft bearings.  The metal is porous which males it retain lubricating oil. But most of contemporary model brass benign for the worm shafts are just machined from solid brass, so they have to be piled more frequently. Like most of things, new is not necessarily better than the old.

[randgust]

If you read the posts, I've already made an operating dynamometer from a spring scale mounted on MT trucks.   Built it in 2004, one of my first test projects posted on forums.  Crude as the devil and still pretty effective.   I don't measure in cars, I measure in grams of pull, and grams of pull/grams of weight=tractive effort % on grading wheel adhesion.    Also measures train resistance.

My FP45 weighs in a 130.2 grams (lead added) with a TE pull of 28 grams for a 21.5% adhesion
My old 1982 Kato GP38 (stock) is right behind it at 128.4 grams, TE pull of 28 grams, for 21,8% adhesion

A 'new production' Atlas GP38 weighs 73.2 grams (stock), TE pull of 7.5 grams, 10.6% adhesion.

Atlas MP15 50.6 grams; 3.5 grams of pull, 6.9% adhesion

That's the problem.   Same locomotive same size, all about weight and wheel material.    So you would need FOUR Atlas GP38's to match one Kato for pulling.

Oh, and my Kato/GHQ L1? 168.9 grams with tender, pull of 34 grams, 20.1 adhesion with traction tire.   Nothing better.

[jdcolombo]

I think that's called sintering.

Yes, it is sintering, and that process was used by many high-end studio reel-to-reel tape deck manufacturers to make the capstan shaft bearings, precisely for the reason Peteski described: they would hold oil.  Studer used sintered brass bearings on its capstan shafts in its A80, A801, A820 etc. studio decks (I think they also used them on their "pro-sumer" Revox decks like the A77 and B77, too), and I think the famed Ampex ATR's used them as well.  Probably ALL the top-of-the-line RTR's did.

Hmmm.  Sintered tungsten split frames.  Now I wonder how much they would COST, rather than the weight . . . 

John C.

[jdcolombo]

From the International Journal of Refractory Metals and Hard Materials:

Tungsten heavy alloys are fabricated using liquid phase sintering to form inertial, electrical, radiation, or structural components. The compositions, initially developed a century ago, are based on various W-Ni-(Fe/Cu/Co/Mo) alloys. Two classes, and W-Ni-Fe and W-Ni-Cu, remain the most popular. Nickel is key to sintering densification, producing the majority of sintering shrinkage prior to liquid formation.

John C.

[randgust]

The paradox here is, obviously, that there's no incentive for manufacturers to pursue this.   The solution, which has sometimes been echo-chambered here, is to simply buy more locomotives and have to MU power a lot more.  Wow, we have to sell more locomotives to pull the same train.  Too bad.

I'm a slow learner on DCC, and speed matching and consisting is not particularly easy. In DC, if you're looking a same manufacturer/same drive, it's not very difficult with a decent throttle, my square-wave transistor throttles do an excellent job, every train except locals has at least two units, and the maximum on long 30-40 car trains is four.   My unit coal train already has 4, I'd have to go 6-8 to handle the same train today.  I'll run the old ones, thanks.

But as long as the market seems to insist on DCC, and sound, this will remain an issue.  And you end up with things like the beautiful, but perhaps fatally flawed, Piko Whitcomb, as a functional and reliable locomotive rather than a 'gee whiz it has sound' attraction.
https://www.spookshow.net/loco/piko65ton.html
Wow, new production and gets a "C".

You have to wonder what it would have cost to just to a really nice, slow speed, 8x8 drive and pickup, reliable locomotive like the Bachmann 44-tonner mechanism.
https://www.spookshow.net/loco/bach44ton.html
Grade A.
And I'd agree, I retrofitted a shell with the mechanism once I tried it out.

And the Kato 11-108/9 chassis, for $16, blows me away how well it runs, and you can do your own DCC and sound if you want it bad enough.  There's room to expiriment.

[nkalanaga]

Could you remove the speaker and replace it with weight?