What if Tender Drives Became Standard on Steam Locomotives?

[mlehman]

Hrvoje,

Thanks for the excellent, detailed illustrated breakdown of the mechanisms involved.

Narrowgaugers, as has been mentioned, often face this problem. Smaller motors lessened the need for tender drives in all but the smallest examples, but it can still be worthwhile to consider tender drive in many cases. One trick that is used to disguise t6he drive is to use a piece of stiff music wire for the driveshaft. It practically disappears.

[Spalato68]

Roco locomotives had from the beginning motor in tender only. In such cases, all tender axles were driven. If tender had 4 axles, 2 were fitted with traction tires – usually first and fourth. Locomotive was without drive. Tender shell was die cast.

Approximately from 1990, Roco started to install drive both in tender and locomotive. In such cases all locomotive axles are driven, and usually first and last axle in tender. In some locomotives, only last two axles in tender are driven.

 

Tender shell is made of plastic – not good for traction and noise generation.  In all these locomotives locomotive wheels do not have traction tires, but tender axles do, usually all wheels on first and last axle.

 

Here is one example of such locomotive. This is model of DR 18 201, East German steam locomotive used to test passenger cars for high speed. I re-motored it and installed lights in cab, firebox, speaker in locomotive boiler etc. Locomotive and tender shells are both made of plastic. Three loco axles are driven, and first and fourth in tender. The other two tender axles are not driven, but are sprung to achieve better power pick up.

 

Fleischmann also installed motor only in tender of its steam locomotives, never in both locomotive and tender. When tender had four axles, usually only first and last were driven, all wheels had traction tires.

 

Example of tender drive in one Fleischmann locomotive (Prussian P8, later DB BR 38) (three axles are driven, one (last) is not):

 

I think if locomotive boiler is made of die cast, drive in locomotive should in most cases be enough to pull reasonable train.

 

Trix/Marklin did not follow this way, their locomotives have motor in locomotive; tender is used for electronics and speaker. But these locomotives are mostly die cast. The same locomotive as Fleischmann P8 / DB BR 38 from Trix looks great, and has drive in locomotive (locomotive and tender are mostly die cast):

Source: Trix web

 

Hrvoje

[Overmod]

dknelson

So what about a third alternative, independent tender drive in addition to the motor and drive in the locomotive itself? 

See the immediately preceding post; much of it concerns precisely that.

I agree that we need a disambiguation for the various motor-in-tender solutions.  I'd suggest 'motorized tender' for those that drive the tender wheels, no matter how they go about it.  "Motor-in-tender" then could serve as the counterpart to "motor in locomotive" if wanted.  We stop using (the standards fancy word is 'deprecate') using 'tender drive' as a catchall for the different methods...

I did in fact at one point make a couple of the Lilliput OO Class 05 Hudson chassis into a large HO 4-8-4.  These were made as earlier described, with the locomotive a passive 'scale model' and the drive geared to the three parallel axles in the tender -- since I was modeling a large pedestal tender this could be 'adaptively reused'.

As noted in the earlier post this opens up considerable room for sound, working prototype valve gear operation (irrelevant on mine as it was a poppet-valve engine with external rotating shafts) etc.  

I think more care is involved in making and tuning a large or long 'passive' locomotive to track correctly on "typical" layout curves.  I don't have firsthand experience with that, though; the curves for the 'conversion' were very long and 'spiraled' top-down.

[dknelson]

We need a different vocabulary here because right now "tender drive" includes the Mantua General and the first releases of the AHM Indiana Harbor Belt 0-8-0: motor in the tender, but powering the locomotive drivers via a shaft, but the same term also refers to motor in tender actually powering the tender's wheels, as per some of the old Fleischmann European steamers. 

One advantage in terms of realism is that the boiler can actually be realistic and not have a big slot in the lower part.  

For whatever reason, many model steam locomotives can pull relatively few cars compared to their prototypes.  So what about a third alternative, independent tender drive in addition to the motor and drive in the locomotive itself? 

I remember an old article in Model Railroader about someone enhancing the pulling power of a die cast PRR steam locomotive, perhaps a Bowser or Penn Line 2-8-2, by putting a motor in the tender and powering the tender wheels.  I don't think it was a geared drive - I think it was a flexible band drive, sort of like Athearn's HiF, but metal not rubber bands, rather like some of the older O scale trolley models.  The fact that the locomotive itself was geared would smooth out some of the irregularities of a pulley-and-band drive.

More recently, an N scale modeler whose name I forget but might have been Rich Weyand, had special versions of a Norfolk & Western tender shell created so that he could utilize a drive train meant for a six axle diesel but with Buckeye tender truck sideframes instead of the original Alco or EMD sideframes, to give his N scale Y6b 2-8-8-2 models something more closely approximating the prototype's pulling power. 

Essentially the idea of that form of tender drive would be to make a steam locomotive sort of a "stealth" double header. 

The original idea may have come from modelers of the very earliest railroads who could not possibly cram any motor into the tiny locomotives but could power the coaches in the train.

Dave Nelson 

[mbinsewi]

Here's an interesting thread from 2009, asking the same question.

Check out the links of the Southern RR by Mark Pierce. 

Lots of other links as well.

http://cs.trains.com/mrr/f/88/t/145956.aspx?page=1

Mike.

[ndbprr]

PFM had a powered truck fully contained called a spud. They sold it to use on brass passenger cars as many engines were incapable of pulling a full train of the cars. I put one under a Metroliner. While a smooth runner it is now capable of at least 700mph.

[emdmike]

One of the "fixes" for the old Tyco tender driven 2-8-0(Chatanooga and Royal Blue) is the Bachmann 44 tonner drive(newest version with the single can motor), this also adds DCC to the model if its one of the versions with this included.  That 2-8-0 was not a bad looking model for the era, but the slot car based "Powr-torq" drive just plain sucks.  Marklin can pull of pancake drives that are robust and run forever using metal spur gears and a robut armature(both flat and drum type at that).  But sadly Tyco blew it with that drive.  With a 44 ton diesel drive, the 44 tonner trucks resemble some tender trucks and the drive is silky smooth as well.  With the whole chassis being diecast metal, it has enough weight for the small 2-8-0 to pull a reasonable train as well.     Mike

[doctorwayne]

Lastspikemike

...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.

Many years ago, I was re-motoring a number of brass locomotives, both steam and diesel, for a friend, and two of them were fairly small 10-Wheelers, which had insufficient room for the new can motors which had been provided.
While I could have replaced those new motors with smaller ones, I instead disassembled the original open frame motors, removing pretty well everything except outer portion which had contained the armature, brushes, and magnets.  

What was left of the motor was then re-installed in its former position.

I then mounted the new motors in the tenders, but put an extension on the motor-shafts which included u-joints, allowing the lengthened driveshaft to be routed through former motor and then coupled directly to the loco's gearbox. 
Even with the skeleton of the motor still in place, there was lots of room for additional weight,  and the owner was extremely pleased with the new-found pulling characteristics.
Many of those locos in need of new motors had original motors which were literally worn-out...not just the brushes, but the motor bearings, too.  This was likely due to the owner's layout (DC-powered) which filled his basement with multiple routes which could be run all at the same time, unattended, if he wish to just watch them run.  Most trains were heavy (20 car brass passenger trains, with cars weighing at least a pound each), and double or triple-headed locomotives on long freight drags. On all my visits there, the trains ran flawlessly, and I never once witnessed a derailment of any type.  There were usually at least 3 or 4 trains running at all times, but I recall that 7 or 8 at-a-time were possible.

Oh, and by the way, the driveshafts passing through the cab weren't normally visible.

Wayne

[Southgate 2]

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

 

 

[Overmod]

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...

[Darth Santa Fe]

tstage

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.

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 )

[ATLANTIC CENTRAL]

ndbprr

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!!

 

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.

Sheldon

[oldline1]

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.

https://www.youtube.com/watch?v=Qh9GsLO-dVw

oldline1

 

 

 

[Southgate 2]

Check out this video by Darth Santa Fe:

(386) Tuning up the custom Tyco Chattanooga - YouTube

[ndbprr]

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!!

["JaBear"]

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.

 

Cheers, the Bear. 

[wjstix]

Trainman440

What's your point? Im saying creating a pivoting system is not hard. 

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. 

[tstage]

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.

Tom

[drgwcs]

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.

[Trainman440]

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.

http://cs.trains.com/mrr/f/88/t/153238.aspx

Charles

[wjstix]

Trainman440

HO diesels have pivoting trucks. Its not as hard as it seems.

Take a look at a GP-7 or F-unit truck sideframe. It's not very similar to say a USRA two-axle tender truck.

[Trainman440]

wjstix

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.

https://www.newrailwaymodellers.co.uk/Forums/viewtopic.php?t=51143

 

 

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. 

[PM Railfan]

I can only imagine what the tender trucks would look like.

 

PMR

[MisterBeasley]

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.

[SeeYou190]

Tender drive is an option. There was a guy converting HO brass steamers to tender drive using the components from Kato N scale locomotives.

These were small steamers IIRC that had small boilers and limited room. I think the effect he was going for was more "open-air" under the boiler.

I think on larger HO steam locomotives tender drive would lose any advantages.

-Kevin

[wjstix]

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.

https://www.newrailwaymodellers.co.uk/Forums/viewtopic.php?t=51143

 

[Trainman440]

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. 

Anyways, just food for thought.

Charles