Drag-racing with a Y-6b

On the matter of a drag race between the Y6b and Big Boy, over the 1,320 ft. quarter mile my money is on the Y6b. A race down the “Mulsanne Straight” is a different matter, but again don’t be lulled into mis-thinking that the Y6 couldn’t stretch its legs.

Jimmy Lisle
Roanoke, VA

Thanks Jimmy. Read on. — Ed.

Y-6b, Big Boy, and the Factor of Adhesion

Reading through the October issue’s editorial I was once again reminded of Robert LeMassena’s comment in a long ago Trains Magazine article in which he noted that railbuffs were as sensitive to comments about their favorite steam engine as they might be about a girlfriend. There seems to be some evidence of this in the October editorial and the review of the N&W Y6b.

There is, of course, nothing wrong with having an opinion... say, that a Y6b would “...walk away with the Big Boy.” However, it seems to me that having such an opinion without supporting facts is just that... an opinion. Before offering a contrary view, let me address something that a significant majority of modeler/historians either don’t seem to understand or simply ignore. Factor of Adhesion (FA). This is the ratio of weight (force acting downward on the drivers) to tractive force (force at the rim of a driver trying to turn the driver). A two-cylinder locomotive, with its two impulses per driver revolution per cylinder, requires an FA of about 4.0 to avoid slipping the drivers on clean, sanded rail. An articulated locomotive operating in simple mode is two 2-cylinder engines powered by a single boiler. Anything less than an FA of 4.0 introduces a tendency to slip. In other words, simply adding additional tractive force to an engine without adding the necessary weight on drivers to maintain the 4.0 FA doesn’t provide any advantage.

Incidentally, early diesel locomotives before modern anti-slipping technology (in which a computer detects the beginning of a slip and reduces the force on the wheel’s rim) were always rated at 25 percent of weight on drivers... an FA of 4.0... although, a diesel with many smaller impulses per wheel revolution had a better footing. Three cylinder locomotives with 6 smaller impulses per driver revolution could operate with a lower FA than that of a 2 cylinder or 4 cylinder simple locomotive, which is why the UP 4-12-2 had an FA of only 3.66.

What does all this mean with regard to a Y6b/Big Boy shoving contest? Simply this: A Y6b in simple mode operating with maximum output (assuming 152,206 lb.s tractive effort) would produce an FA of 3.60... a very slippery operation. A Big Boy operating at maximum capability would produce (with 135,400 lb.s tractive effort) an FA of 4.0 (ideal to avoid slipping). For the Y6b to avoid spinning its drivers, the engineer would have to cut back to the tractive effort which would produce a similar FA. This would be 137,000 lb.s. The problem, of course, is that the Y6b’s engineer would have to be rather precise or he would have a slipping problem or less tractive effort than Big Boy. Once slipping starts, friction to overcome it is much higher, so the engine’s output in that case would have to be drastically reduced. The other problem is that a Y6b wasn’t designed to operate for very long in simple mode. The boiler/firebox simply wasn’t large enough (the reason for the Big Boy’s additional 161,000 lb.s). Thus, if the contest lasted for very long, the Y6b would either exhaust its steam supply or have to operate in compound mode with its (output) reduced to 126,838 lb.s tractive effort.

I would also note that the Y6b might well win in a drag race with a Big Boy (the engines running side by side)... up to a speed of about 20 mph. The Y6b would produce (in simple mode) 4 impulses per driver revolution... as would Big Boy... but those 4 impulses would be over a distance of only about 180 inches whereas a Big Boy would generate 4 smaller impulses over a distance of 213 inches. As the engines accelerated, the Y6b’s impulses would decrease in magnitude much faster than Big Boy’s such that at speeds above 25 mph Big Boy would be producing more force on the drivers than a Y6b. Hence, in a race, the Y6b would take the early lead and be passed at about 25 mph.... not unlike a race between bicycles... one with small wheels and one with larger ones.

Incidentally, there actually was such a contest between two locomotives. In this case it was a 2-6-6-2 (I think) and an electric locomotive on the Milwaukee Road (again, I think). The test was arranged such that they pushed each other rather than pulled apart. The steam engine took an early lead, pushing the electric back and then the electric engine apparently achieved its max power and shoved the steamer backwards. There’s a photo of it in a Trains Magazine. My guess in the case of the Y6b and Big Boy is that neither would move much. There might even be some blown cylinder heads.

Mike Brock
Merritt Island, FL

Great letter, Mike! That’s why I exercise my opinions because, with just a few words, I drew out a more thoughtful treatise than the research I had was willing to yield. I’m sure our readers appreciate your writing efforts as well as your math. In the end of it, the design engineers in Roanoke designed the Y-6b to accomplish a particular job on their railroad, and the evidence is that it did that job as well as any steam locomotive could. The Big Boy did a different job, and also did it well. PCM has given us one of each. Is this a great hobby or what? — Ed.

N&W Designers in Cowboy Boots?

I grew up around Schaeffer’s Crossing and the J class 4-8-4s were the smoothest I rode behind. The UP FEFs and the SP GS engines were jerky; the ATSF 2900s were more powerful but still not as smooth. The A class articulateds could probably out pull both of the UP Challengers but not outrun them on the flats. The Y class sure had the best starting effort of any 2-8-8-2 and they were compounds. Even the simple 2-8-8-2s of the NP (and I did see those in Spokane, WA) couldn’t get started that easily. If steam would have stayed around just a few years longer, the N & W designers would have been on loan to the western railroad engineering offices.

Norm Silver
Vacaville, CA

Thanks for that one, Norm. It’s nice to know that I’m not the only guy around here with an opinion. Yours will surely provoke a reply or two, and that’s just fine. I trust you find the weather in Vacaville to be better than Schaeffer’s Crossing. — Ed.

Correction on NCE System Consisting

Comment in the article on October’s MRN, page 62:

“The Rear Loco idea is a feature of NCE that neither replicates any action in prototype diesel consists nor serves any great purpose in model railroad operation, but it is a difference worth noting.”

I’m sure by now others have pointed out the error in this statement – under decoder-based consisting, you can run a consist with the NCE system from either the lead OR the rear unit number (as well as the consist number). This is why the NCE consist build asks for lead loco first, rear loco second, and other locos afterwards.

This is a really useful feature. Let’s build a two-unit consist of GP40 #100 facing forward and GP40 #101 facing rear. After coupling to the front of the train, with #100 in the lead, I select loco #100. The direction of the train now matches the direction of loco #100, and the headlight button controls #100 only (assuming I haven’t programmed anything to the contrary). Down the line somewhere, I need to run the power around my train and couple the consist to the other end of the train. With #101 now in the lead, I select loco #101 on the controller. The train direction now matches the direction of #101 and the headlight button operates the lights on #101 only. Very realistic — this is one of the major reasons I use NCE, as run-arounds are common on my layout when delivering a train to a single-ended yard to drop off cars.

Steve Troy
Levittown, PA

Well, you’ve shown me the light, Steve. I hadn’t seen the notion of taking the lead at the rear of the consist using the “Rear Loco” function. That certainly does have an important use, especially in “turn” operations. Just for whatever it’s worth, locomotive engineers tell me they can run the consist in any direction from any working locomotive in the consist. Only Lenz offers that feature, but you should be aware that FRA and GCOR limitations may prohibit any sort of lengthy run from any loco other than the front one in the direction of movement. — Ed.

DCC Decoder Issues

I read with interest the comments regarding “negatives” with sound-equipped DCC locomotives in particular and DCC in general (October issue, RPO, Ernie Carlson, Zigzag, OR).

I have a number of DCC sound equipped units operating on a moderately large HO layout and have had the following experiences:

1. Four (two P2K GP 9, two BLI E8) QSI equipped DCC w/sound locos have all exhibited shorting of track power when changing directions (albeit randomly, but often enough to be a nuisance. Power restores itself each time after a momentary wait). I sent a BLI unit for factory warranty repair, and it was returned with a note that the problem was related to wheels being out of gauge. The problem persisted so I contacted QSI directly. In short order I was sent, at no charge, two replacement chips along with an extraction tool. Problem solved. I also contacted Walthers P2K customer service and was told I could return the GP9s for replacement chips… they were aware of the issue and prepared to put it right. However, I had already ordered two replacement chips from Tony’s Train Exchange (TTX) and installed those instead of returning them and waiting while I sent my locos to Walthers. Again, problem solved (and at no expense if I had decided to send the locos to Walthers).

2. I have a “fleet” of Athearn Genesis F-units with DCC and sound. Only one loco has exhibited any problems, and that was some kind of internal short that turned the circuit board into a pretty effective smoke generator (maybe intended for an Alco?). I contacted both Athearn and MRC and am getting things resolved as I write this (the first replacement board has some issues, but I expect it will be resolved in short order).

3. I purchased four Powershield units from TTX several years ago and, with the addition of a lot of sound equipped locos, I began to experience slow recovery from shorts on the layout and occasional reluctance to start at all when powering up the layout. Turns out I “missed the memo” from TTX, and a phone call to them solved the problem by being told to add a simple wire jumper on each Powershield circuit board. Problem solved.

4. I was one of the “first kids on the block” to have an NCE wireless system on my layout. Both the antennas and internal circuitry of the cabs eventually needed some improvements, but NCE resolved all issues at no cost to me as improvements became available.

I think the point here is that all of these manufacturers have exemplary customer care, making it possible to resolve any problems in a reasonable timeframe and enjoy incredibly realistic operation and sound effects. Whatever frustrations I may have experienced have faded quickly. I cannot imagine going back to a DC system with manual blocks, fixed or tethered cabs, and no sound effects. DCC is still an emerging technology, but I think it’s here to stay for the serious model railroader, and only getting better every year. Problems are relatively few and the manufacturers are committed to customer satisfaction.

Bob Johnson
Belleair Bluffs, FL

Thanks Bob. I think some of this has to do with you. With a cheery demeanor, you got better results than by yelling and being hostile, a point most people in customer service would like to make. They will give you what they are allowed to give you; negativity won’t get anything more. I’m glad you’re enjoying your toys!. — Ed.

Prefers Wire Handrails

Model trains have been my main vice since about 1951 when I received a Lionel Scout set. HO is the scale of choice now. The new models on the market these days have many more details and better drive systems than the older models. The one complaint with the new models is the rubber handrails. These things are not paintable and are not very durable. I’ve taken to making new wire handrails using the rubber ones for a pattern and then tossing the rubber ones in the trash.

Rail Detail once made wire handrail sets for Rail Power Products now owned by Athearn. Sure would be great to have someone make wire replacement handrails for the rubber ones. Alco, EMD, GE, etceteras.

Cliff W. West
Rainier, OR

Actually, Cliff, they aren’t rubber. They are an engineering grade plastic on the order of Delrin or Celcon, but there are other brand names, too. One of the unfortunate side effects of this category of polymer is that ordinary paints won’t hold well. Usually, they are molded in color, but even that fails when handrails on the prototype are done in more than one color. You can purchase the Athearn Blue Box handrails separately through their parts channel, but the stanchions leave something to be desired. — Ed.