Radius

[Rielag]

What is the largest Locomotive that Can be used on a 18 in radius?

[Irbricksceo]

It depends on a lot of factors. The largest I have run personally is the Bachmann 2-8-4 and it derails on occasion. I'd just get a 2-8-0 or something in that size range ans use it.

[ACY]

Stick to 4 axle diesels or steam lcomotives with a short wheel base such as an 0-4-0, 0-6-0, 2-6-0 or 2-6-2. In my personal experience a 2-8-4 requires a 22" minimum radius, on 18" radius it derails quite often. I suggest to play it safe to avoid problems down the line. Tell us what you have in mind and we can likely advise what your minimum radius should be.

[jward]

it is not so much a question of how large a locomotive can negotiate an 18r curve, it is a question of can this locomotive negotiate the curve  while pulling a train without derailing whatever is coupled to it. locomotives and cars work best on 18r if they are shorter than about 50 scale feet  (7 inches)

[Doneldon]

Rie-

The modern model railroad industry has found ways to get very large locomotives around 18" curves. However, that doesn't mean you should run right out and buy one to haul your trains. Putting oversize locomotives on tight curves looks worse than ridiculous and often leads to serious operating problems, including with the rolling stock they haul.

Nevertheless, I can tell you about a fairly long list of big steam and other locos which can negotiate 18" curves: Broadway Limited sells Hudson, Decapods, Pacifics, Mountains, Northerns and Mikes which can do it. Mike's Train House offers Northerns, Challengers, Big Boys (which are longer than 18 inches!!), Triplexes (2-8-8-8-2) in steam and GE ES44ACs, GE Dash9-44CWs, EMD SD70ACes, Pennsy GG-1s and Milwaukee Bi-Polars.

You'll notice that our hosts here, Bachmann, don't sell rail giants to run on toy train curves. I like to think that's because they realize just how preposterous this is and they don't want to set their customers up for frustration when they get their shiny Big Boy, only to find that they're lucky to get three laps around their 4x8 layout without a derailment of the loco or its consist. Or both. And, heaven help us if you try to back one of those beasts with the train leading the way (for a few inches).                                                                                                                                                                                                                                          -- D

                                                                                                   

[Irbricksceo]

Yeah, that wouldn't work well would it! I had no idea that MTH was making such huge locomotives that could do it, though as you said those cars are gonna hop the track rather quick. THe 2-8-4 I mentioned looks silly doing it and derails too often for my taste. That said, Bachmann makes or has made locomotives that look nice on the curves (or as nice as a loco can look on 18). the russian 2-10-0, the Chinese (not the new USRA which I donno) 2-8-2, the 4-4-0's, the 4-6-0, the 2-6-0, the Baldwin 2-8-0, and their geared locomotives will all do it.

[JimJim]

Way too many variables to recommend definitive motive power on 18-inch radius trackage.
-Diesel or Steam?
-If steam size of tender; switcher, short or long haul?
-Era modeling or theme?
-Are you consisting (MU)?
-Maximum, or desired, number of rolling stock pulling (tractive effort)?
-Flat or mountain pike (grade percentage)?
Once you figure out your needs then you can choose the appropriate motive power.
I completely agree that a DD40AX or a H4 2-6-6-2 might work on a 22-inch radius curve, but it will look out of place. A consist of GP-38s or 40s might serve you better. If steam consider a 2-6-0, a USRA 0-6-0 or a Climax or Shay- -if your budget permits.
For switching duties consider a 110- 70- or 44-ton diesels or a 0-6-0 or 0-4-0(T) steam.
For short overland hops how about an RS-11 or RS-3, if appropriate for your concept.
And do not rule out the venerable F-series diesels, with accompanying B-units.
Hope this helps.

[jward]

one exception to the general rule of not using 6 axle diesels on 18r curves would be the alco rsd5. this locomotive is basically an rs3 with 6 wheel trucks. I have 4 and they work well on my 18r curves.

[MarkInLA]

Even if engine does make it though OK, with a 10, 15, 45 car train it's likely to have so much drag engine will either spin wheels in one place, or at speed whole train could pull strongly toward inside and derail or have a string drop down to floor or into the scenery. Small engines. Short trains. Slow speeds OK. A 2-6-6 2 T or S4 switcher, interurban, OK. NYC Hudson forget it ! It's simple logic. track physics are no different for the model than the 1:1 scale.. Related : If you have track ascending on a curve, what measured out to be a 2.5 % grade will make train behave as if it's a 3.5 to 4 % grade also due to drag from the curve and engine, again, will slip in place (until the day when we have operating sand domes !).

[jbrock27]

I guess a couple of other exceptions to whatever the general rule is, is the 2 SD45s and 1 SD9 that we run with no problems on 18" radius curves as well as through Snap Switches, I might add.  The look of 6 axle diesels on 18" radius curves may not be for everyone though, especially those in the crowd that are railroad modelers, not model railroaders.

And I will further add, that in working on an old Athearn SDP40, which has 6 axles, for a friend of mine last weekend, I had it running around some EZ track I have on 18" radius curves, no problems.  A further aside, not related to the OP's question was how to get the brass wheel sets on it cleaned as this thing is more than 30 years old.  For anyone interested, instead of spraying WD40 on a paper towel which is what I have always read about, and running the wheels on the paper towel, I used PB Blaster instead and it made the wheels shine and clean like new.

[ACY]

We must remember there is a great amount of variability in these scale models. Even though some of us have experienced success running a particular model on 18 inch radius curves, it is many times the case that some will not be able to operate reliably on 18" radius curves.
For instance jbrock27, I have 3 Bachmann SD45s and only 1 of them runs on 18" radius reliably without frequent issues. Further all of my Athearn SD45s have issues on 18" radius but are fine on 22" radius track.
Irbrickseco, I have 3 Russian decapods, 1 Chineese 2-8-2, and several consolidations and out of the whole lot of them only 1 2-10-0 & 1 2-8-0 run reliably on 18" radius the rest run perfectly fine with no issues on 22" radius.

Doneldon, I just personally checked the operators manuals for the following BLI locomotives:
NYC Dreyfuss Hudson, 2-10-0, 4-6-2 (heavy), 4-8-4 J & Northern
And not one manual lists a minimum radius of 18", they all state 22" minimum radius and in my experience that is pretty accurate.
I also have MTH ES44ACs, SD70ACEs, a GG-1, a Northern, a bigboy and a friend has the Erie Triplex and the paperwork included states 22" suggested minimum radius. I recently attempted to run the NS heritage units on 18" radius to no avail.
Although it is very possible you were able to run the locomotives you listed sucessfully on 18" radius, I think it is a poor idea to make a blanket statement like you made just because of the variability on the models. It is better to list off just what will run on 18" radius safely 100% even with the variability instead of hoping you get lucly and get one that will make 18" radius without derailing or excessive binding.
Of course I am sure most of you were aware of the variability in the manufacturing process but I thought it was important to point this out before someone goes out and purchases a large wheelbase locomotive and is disapointed when it derails on.18" radius even though someone here said it would be fine.

[jbrock27]

True enough ACY.  The common denominator for me is I have checked the gauges on all the wheels for our locos.  In the event you may have overlooked this, have you checked yours?  Also, free play of the trucks is important.
I would also agree/like to point out that the longer the wheel base of the loco, the more logical it will be that it does not run well on 18" R curves.  If you ask me, the overall length and wheelbase of the loco is more important a factor than simply the number of axles.

[ACY]

True enough ACY.  The common denominator for me is I have checked the gauges on all the wheels for our locos.  In the event you may have overlooked this, have you checked yours?  Also, free play of the trucks is important.
I would also agree/like to point out that the longer the wheel base of the loco, the more logical it will be that it does not run well on 18" R curves.  If you ask me, the overall length and wheelbase of the loco is more important a factor than simply the number of axles.

One of the first things I do when I buy a new locomotive or piece of rolling stock is check to make sure everything is in line with the NMRA standards. None of my locomotives had wheels out of guage. Also another factor is if there are any blind drivers or not.

[electrical whiz kid]

A while back, I started building the supply of Tichy ore cars I had been hoarding over the years; since they were Goulds...  About twenty four cars later, I figured it was time to give 'em a shot on the rails.  What to use for locomotives...!  Well, I have five BACHMANN (See Dave?  All is not lost here...) 2-6-0 Moguls.  I set everything up on track and tried them out.  Not only did the cars do well (the Kadee trucks helped lotsly, I am sure), but the locomotives looked REAL good, and operated very well on rather tight radii (I have policy of 24" minimum on my layout).  All of this being said, I heartily recommend using smaller rigid-base (steam).  They will look like a million dollars running on point or in tandem; on head of a local pedlar, or, as I have, on a mine or some industrial short line.  The guys on this board have a lot of good info for you guys new to the hobby.  Good luck!
Rich C.

[WoundedBear]

Rich........

I like those Tichy ore cars too. I have one set of 12 completed and looking to do another string of 12 soon. I opted to use the Tichy trucks, and along with the added weight of the ore load, they seem to track pretty well. I usually assign a Shay or Climax to pull them. All is fine on the 18 inch sections.

On my layout, I knew 18 was going to have to be the ruling radius, so my motive power is limited as well. Common road engine for my layout is the Spectrum 4-6-0 with small drivers.

If you haven't got room for large radius curves, then accept the fact you can't run monstrous locomotives. You'll be much less frustrated in the long run.

Sid