I just had a thought about what if tender drives on steam locomotives became common place.
Think about it, it would make producing and designing an engine much easier since steam locomotives comes in all sorts of shapes and sizes, but tenders stay more or less the same, so a similar mechanism can be used for all engines, sorta like diesels these days.
Tenders are also usually just a big rectangle (besides vanderbilts and slope backs) which can just be a huge hunk of metal, and able to fit a massive motor, making them able to pull quite a bit too.
Tenders also have small wheels, so slower speeds can be more achievable with the same gears and motors.
Lastly, you can now put the decoder inside the engine, which means sound can finally come from inside the engine instead of from the tender. You could also fit much more inside the engine like smoke units, internal detail, etc. Im personally not a fan of smoke units, but atleast now they wont hinder the pulling performance. (Im sure those who run DC are gonna complain how this point is worthless)
Obviously you wont be able to have slipping drivers, but the infamous binding and mechanical nightmare that comes with using steam locos could basically disappear. No more need for sprung suspension, now all the wheels have to do is be free rolling.
Now Im not saying this SHOULD be the norm, but I am proposing an alternate world, and how its not as bad as one may think.
Tender drive was at least at one time common on British OO models. Most UK tenders used three single axles that didn’t pivot, making it easy to connect up a motor to the axles to power them - essentially the entire tender was like one big powered diesel truck. A lot harder to do on a tender with two pivoting 2- or 3-axle trucks. The British had trouble finding motors small enough to fit into their engines - that’s why they use 4mm OO scale instead of 3.5 HO scale. In recent years, I believe most all UK OO engines have the motor in the engine, and they run much better than the old tender drives from what I’ve heard.
A tender doesn’t weigh much, and tractive effort depends significantly on weight. If you add weight to the tender, it would take up the space you propose using for the motor, and you would end up with a heavy tender pushing a lighter locomotive shell, a more likely derailment situation.
HO diesels have pivoting trucks. Its not as hard as it seems.
Yes, some tenders are much smaller than some diesels. On the other hand, PRR coast to coast tenders, or ATSF’s massive 16 wheel tenders, etc could be prime candidates.
The engine isnt going to be completely weightless, obviously you add enough weight and design a proper drawbar and leading truck to which the engine wont act like a plastic box on wheels that derails all over the place.
What’s your point? Im saying creating a pivoting system is not hard.
Most diesel locos built today have multiple gears in each truck that brings the power from one wheel to the other. Simply remove a few gears to bring the wheels a bit closer, and shrink the overall design. If they can make these trucks for tiny N scale engines, they can certainally make one for HO standard tender truck sizes.
DarthSantaFe’s tender driven 2-8-0 was my inspiration for this post, and is proof it can be done. His engine runs really well. If it can be hand made, I have no doubt a manufacturer with access to all the factory capabilities can easily replicate it and make it even better.
How about putting decoders into the locomotive instead. I’d rather have a locomotive that ran without a tender than a tender that ran like a B unit.
Drawbar pull for a tender drive would be pathetic.
If you passed the drive through to the locomotive and loaded up the empty space in the locomotive otherwuse used for the motor with lead or even steel that might be worth a look. But the drive shaft passing through the cab would look awful, it does on those Bachmann 4-4-0 that did exactly that.
The first thing I think of when I heard this were the poor attempts in the past at this. The Pemco’s and Tycos come to mind. I had one of the Pemco 2-6-0’s back in the 80’s ran awful with a tender drive. The IHC (based on the same boiler tooling etc) was far superior with a powered loco and conventional tender. Model Power made a 2-8-0 back in the early 2000’s that was tender drive and it was not much better. The wheelbase of most tenders is shorter than that of the trpical diesel so there is not as much room for a motor if a more “conventional” diesel layout is used in the tender.On the other hand the ones with the motor in the tender driving the wheels in the engine have a tendency to torque especially when starting.
I like the way the prototype did it with the weight of the boiler over the drivers. The drivers would also rotate at a slower RPM because they are a much larger OD than the tiny wheelsets on a tender. The motor in a tender would need to rotate a whole lot faster in order to achieve higher speeds and therefore would likely be more prone to breakage and increased maintenance. Kinda like putting little tiny tires on a motocycle or bike.
Just because something can be done doesn’t make it a good idea. If there is room restrictions inside the boiler of the locomotive then it might make sense put a motor in the tender. However, I think it would only be practical for switchers that operate at lower speeds; NOT for a passenger locomotives operating at higher speeds.
My point is that a two-axle tender truck is about half as large as a two-axle diesel locomotive truck. There’s very little room to hide the gearing and such necessary to make the trucks powered with enough power to pull a train.
I write the following having had a reasonable amount of experience of running OO tender drive locomotives at train shows on a layout with 22” radius curves, designed so that children could use the throttle.
Considering the “hard use” they got the locomotives ran well, yes, the connecting rods and associated mechanism on the locomotive did get lubrication after each show, but the actual problem was with the lousy pancake motors and mechanisms that the Brits persisted with long after there were far better alternatives.
With the improvements in motors and mechanisms, none of the relevant objections of tender drives, raised by pervious posters, should be insurmountable, but why bother?
To answer my own question, the only reason tender drives are relevant, is for those who are fascinated with, and wish to model small narrow-gauge locomotives in the smaller scales, ie. HO, OO, or (and my eyesight and clumsy fingers would preclude me from) Nn.
At least 50 years ago I think it was Mantua that had tender drive model of the General. But it had a universal drive shaft that drove the engine drivers. My experience makes me want to scream NO!!
Most of us have bad memories of tender drive engines thanks to Tyco and some others. AHM/Rivarossi made their IHB 0-8-0 in a tender motor version that drove the drivers and it was very smooth and powerful.
ROCO came out with a USATC S-160 2-8-0 a few years ago with a complete drive and sound system in the tender. Very smooth and reliable engine. It is proof it can be done well. With today’s motors and advancements in technology you need to forget the abominations produced many years ago.
I have two of those, they don’t run bad for a tiny little loco like that.
But I think it would be hard to build a good looking geared tender truck. The gearcase that would need to be behind the sideframes would be bigger than the sideframes and obvious. That alone makes it a non starter for me.
That depends on the gear ratio. HO scale steam engines are usually geared somewhere between 20:1 and 30:1 to get the correct speed, while diesels with smaller wheels may have a ratio between 10:1 and 14:1. As an example, BLI uses the same 8,000-ish RPM motor in most of their steam and diesel models, and gets them all to run at close to the same speed by changing the gear ratio where needed.
(Thanks to those of you who brought up the Chattanooga [:)])
Allan Mueller, in rebuilding the Mantua General, made a tender drive with a stiff wire in colletlike chucks (the article can be bought at smallmr.com). This made the driveshaft virtually disappear. I suspect painting it a neutral color might do even more (view of the shaft is usually from an overhead angle with the locomotive running, and that is less obvious than side-on in photos). Might be interesting to see if a clear driveshaft, or heavy monofilament, could be made to work…
A tender drive might easily be made on a larger locomotive to power both the tender wheels and the drivers. If the prototype has a stoker, much of the shaft detail might be made appropriately ‘scale’ in visible parts and location. Might be interesting to see if one of the clear plastics or heavy monofilament could be made to serve…
I recently repowered an early Pocher (not the later AHM) Rivarossi “Reno” 4-4-0 with a smooth motor and flywheel in the tender, driving the front driver via the familiar drive shaft. It runs extremely smoothly and quietly. I think the worst thing about every Rivarossi locomotive I ever owned was that noisy cogging 3 pole motor. Dan