ALCO 2-6-0 Pulling power

[rogertra]

Not a single one of my two dozen or so kettles has springs on any of their trucks and they all ran perfectly on both my hand laid code 70  track and switches and the Altas code 100 track and switches in the staging yards.

Guess it all comes down to how carefully you lay your track?

However, if you are having problems, then adding a little weight to the top of the truck is far better than using the springs as the springs DO reduce traction, which was the point of my original post. 

My original post was not about tracking but about traction.

Besides, you can't argue with physics and the physics is, for every action, there is an equal and opposite reaction.  It's the law. 

[2-8-8-4]

I'm a licensed civil engineer, so I do know a little bit about traction--and about model railroad trackwork and tracking of engines, since I've been in this hobby for 38 years (since I was 5).

Perhaps you are only running short trains with small motive power.

My experience includes large, heavy trains with large motive power on club sized private layouts and everything else in between.

In your original post you claimed the upward force of springs is enough to reduce model engine traction--and to that I must call "baloney" in most cases.

Do you actually have one of these Alco 2-6-0's?

Are you aware the spring is at the point where the screw attaches the lead truck--such that it is just enough to provide a minimal amount of downforce on the lead truck?  There is virtually no weight transfer at all to the lead truck--the loco weight is on the drivers--the truck would be entirely free-wheeling if not for the very modest force provided by the spring.  The weight of the engine is also significantly more than the force the spring could possibly provide--therefore any "upforce" of the spring is zero for all practical purposes.  Also, the third driver is placed far enough away by itself to more than counter any moment provided by the mild lead truck spring.

Also--locomotive traction is most influenced by weight on drivers--you will never convince me that a heavy brass or zamac articulated can have enough spring force from lead and trailing trucks to cause the "uplift" you are talking about--and I know from personal operating experience the springs are necessary.

Your argument does not wash.

To increase pulling capacity it would be far more useful to add weight to the (light) boiler than to remove the small spring which barely exerts any force.

Respectfully submitted--


2-8-8-4

[rogertra]

2-8-8-4.

I have two of the 2-6-0s but have nowhere to run them at present.  As I model based on Canadian practice, I have no need for articulated power and in the area I model, the 2-10-2 was the largest power seen.

However, practical experience on my steam fleet, at the time I had a working model railroad, ranged from Spectrum 4-6-0s (Two versions), 2-8-0s, 2-10-0s, 4-6-2s (Athearn), 2-8-2s (Athearn) 4-8-2s (Both light and heavy) and 2-10-2s (Re-branded IHC), showed that in all cases removing the truck springs allowed the locos to pull anywhere from two to three more freight cars.  Remember,  I am discussing pulling power, not the ability of the trucks to stay on the rails, that's a whole different kettle of fish.  I am also discussing Spectrum, Genesis and P2K and not cheaper low end models.  These models are all light weight and the springs will have an effect on traction.

My steam fleet also included P2K 0-6-0 and 0-8-0 switchers but they are outside the range of this discussion, not have trucks. 

Of course, each and every one of the above then had extra weight added to balance the centre of gravity around the centre of the driving wheel's wheel base and this also increased their pulling power.  In the case of the Athearn's, the balancing of the weight distribution made them reliable trackers as they were notorious for derailing leading trucks.  Derailment of trucks is also caused by unbalanced weight distribution, both on models and on the prototype.  The single act of balancing weight distribution around the centre of the driving wheel's wheel base will improve both tracking and pulling power on almost any steam engine.

On the prototype, if you take a 4-6-0 and a 4-6-2 of about equal weight, driver size and tractive effort, the 4-6-0 will start a train of equal weight easier than the 4-6-2 because when the engine "digs in", the weight distribution moves to the rear of the engine and makes the drivers "dig in" more than the 4-6-2.  This is because the trailing truck on the 4-6-2 limits the weight shift on the Pacific.  The trailing truck on the 4-6-2 is, of course, sprung and will limit the amount of weight transfer to the drivers. 

In fact, a 4-6-0 will start a heavier train than a slightly larger 4-6-2 with less wheel slip.  Goes for any engine without a trailing truck.  It's why an 0-8-0 switcher can pull more than a road engine, because all its weight is on the drivers.  By removing the springs over the trucks, and letting the trucks just go along for the ride, we are, in effect, converting all our locos to "switchers" and putting all the available weight, properly distributed, on the drivers.

My standard train was 16 cars plus van and all except the 4-6-0s were expected to pull a train this long up the 2.5(sh)% grade from the hidden main staging and all could manage it.  Just, in some cases as I kitbash my engines so some have different tenders, cabs and fittings than others of the same brand but they all could do it with no wheel spin.  However, I don't see what train length has to do with truck derailment.

BTW, I've been a "modeller" for 50 plus years and had a toy train set ten years before that. 

All the above has, over the years, been discussed in the model press.  I am not the originator of idea of removing truck springs but took the idea from articles in the model press and found the results to be as "advertised".

Interesting discussion BTW.

[2-8-8-4]

By removing the springs over the trucks, and letting the trucks just go along for the ride, we are, in effect, converting all our locos to "switchers" and putting all the available weight, properly distributed, on the drivers.

I can agree with the above statement.

As an aside, coming over here from the Atlas HO forum, this is as contentious of a thread as you'll hopefully ever see me post.  Hopefully, it's more constructive than contentious, but others will have an opinion on that.

First of all, it seems Roger is or has been dealing with a lot of lighter weight--perhaps sometimes even underweight--steam locomotives.  If the engines are basically underweight, then I will concede the lead/trailing trucks could possibly be an issue.

The other observation I'll make is if your motive power is a 2-6-0 that can pull say 7 cars, and you add 3 more cars pulling capacity--that is actually quite a big improvement.

Also, I do not believe in operating my engines at their maximum limit of adhession--the point of impending wheel slip--so my ratings are always conservative in favor of long term locomotive durability.  I learned many years ago when playing with my own and my friends' brass steamers, on an attic layout with 2.5 to 3% grades and 48" radius curves that it was a bad idea to operate engines in a wheel slip or near wheel slip condition.

My perspective on pulling power of models is also a bit different:  When I can take an early 1980's Key Imports/Samhongsa-built steam engine like the Rio Grande L-105 4-6-6-4, take it out of the box, put it on the track, and pull more than 50 cars (including a dozen or so heavy brass freight cars) up the 3% grades at a walk, without any slip whatsoever, the need to gain a couple more cars of pulling capacity is...questionable at best...so it's just not something I'm looking to do.

Finally, where my comments about heavy long trains and tracking of big heavy motive power over turnouts should begin to make sense is that if one is going to seriously switch or even back a long train of up to 50 cars, or even a shorter cut, into and out of yards over complicated switch configurations such as the three way or double slip turnouts--the forces on the motive power are magnified and any out of weight balance issue will come to light very quickly in the form of derailments of lead and trailing trucks.  That is where having the factory installed truck springs on those big steamers is a good idea.  When one or one's friends are playing with expensive rolling stock...well we wanted to eliminate any chance of derailments possible.  So that is why although some would happily delete those lead/trailing truck springs, myself and the local "lodge" members would not.

Best Regards--

2-8-8-4

[rogertra]

2-8-8-4.

You made some great points and based on your last post, I agree with everything you say.

For locos that can pull a heavy train right out of the box, why remove the springs?  I agree, it doesn't make sense.

And yes, the Spectrum, Athearn and P2K engines I use are too light and are in need of added weight.  I have found that removing the springs does help with their pulling ability as does balancing the weight over the centre of the driving wheel wheel base..

I'll also add that like the prototype, I avoid complex switches like three ways and single and double slips like the plague so I don't encounter the same issues that your group may.

Hope you become a regular on this forum.

[2-8-8-4]

Rogertra--

Thanks for your comments.

Although one layout I built had the complex turnouts to save space in a yard ladder (based on either a John Allen or Armstrong's "spaghetti bowl" type track plan), my current layout went minimalist for the reasons cited above.  Instead I'm trying to emphasize the scenery and put trains in a rural America context...it's a work in progress.

I love all the complicated turnouts--I really do--but they can become a maintenance headache.

My current layout runs around the outside of my basement to save floor space for other things (kids to play, etc.) and has only a total of 5 turnouts with a loop at each end of the layout.  We just like to turn trains on and let them roll at my house...it's not for everyone.

For me the turnouts are the biggest headache--any dirt and I may have a brief power drop--enough to stop a train once in awhile, so I religiously apply the Atlas Conductalube to the rails to keep them clean (any excess evaporates).

2-8-8-4

[Patrick Durand]

The original post was about the new Bachmann ALCO 2-6-0 pulling power.  6 of these units have now passed over my bench for Kit bashing.   All ran perfectly out of the box.  From some other posts it may be that a few of these models may have had some minor assembly problems and the spring on the pony truck may have been improperly positioned resulting in reduced tractive effort.   I would not expect a prototype 2-6-0 to climb a 4 percent grade with more than three empty cars, why expect more of the model?

Comparing relative pulling power of the rigid frame inexpensive light weight locomotives with fully sprung and weighted locomotives is going to prove one thing.  Articulated side rods and sprung drivers keep the tires on the rail providing adhesion.    A three axle rigid frame loco will have four of six drivers actually working and a four axle rigid frame loco will still have four drivers doing the work.    Put the locomotive on a surface plate and see which drivers are touching, and then realize even if they are lll touching the rail geometry is always changing that little bit.    The only compensation is adding all the balanced distributed weight you can.   I have never been able to stall a locomotive in this process but you can sure improve the DDE effects of a sound system.

In my opinion the metallurgy of the tire also plays a major part in the tractive effort obtained by our models.    I have used several Athern Genesis Mikes and Pacifics as foundations for Alaska Railroad Kit bashes.   Out of the box they would barely move a properly weighted 6 car train on a 2 percent grade.   After removing the springs on the pilot and trailing trucks and building in an additional 4.5 oz of lead there was hardly a measurable improvement.    Only after adding all wheel pickup to the tender and carefully adding Bullfrog snot to the rear drivers would they work on a grade, increasing tractive effort by 100 percent over the unweighted loco with out the frog snot.

At the NLMRR Club we have created a dynometer car to measure drawbar pull.   A small digital scale from that tool company is mounted on a flat car.   The scale is then connected to the tender drawbar and you can measure the actual pull in oz in a stall on level track or on any gradient you set up.  Very instructive tool.

Pat Durand

[Doneldon]

roger and yellow-

I'm glad the two of you found some common ground and acknowledge that you each have a point. The physics don't change, of course, whether we're talking about a full-size 2-10-2 in Canada or an HO Challenger from Colorado. What might change is the significance of the effect.

Pushing up on any part of the bottom of a locomotive will unquestionably change the weight bearing on other supporting wheels. BUT, will a little spring make enough of a difference to really matter? Probably not. It strains credulity to assert that the minuscule weight change from pilot or trailing truck springs could materially affect how many cars a locomotive can pull, although one could certainly identify different weight on the drivers. It's easy to see. Just weigh the weight on drivers using a postal scale with extra wheels supported off of the scale both with and without the springs. There will be a difference but it will be moot.

                                                                                                                                                     -- D

[jward]

2-8-8-4 and roger.

with regards to the effect of the force with which unpowered wheels press down on the rails reducing tractive effort: that is a well documented fact. sorry, 2-8-8-4 but it's true, increasing downward pressure on unpowered axles decreases tractive effort, lessening that pressure increases tractive effort.

perhaps, being steam modellers, many of you are not aware of one of general electric's newest diesel locomotive types, the es44c4. this locomotive has an a1a-a1a wheel arrangement, with the two outboard axles on each truck powered, and a center idler axle. this center axle is able to be hudraulically lifted slightly when starting a train to place most of the weight on the powered axles. once the train is moving and the need for tractive force decreases, this axle is lowered back into its normal position. by doing this, general electric was able to produce an ac drive locomotive that does with 4 motors what took the equivalent dc drive locomotive 6 motors to accomplish.

prototype practice almost always has similar applications on model railroads.

[2-8-8-4]

sorry, 2-8-8-4 but it's true, increasing downward pressure on unpowered axles decreases tractive effort, lessening that pressure increases tractive effort.

My argument is that the decrease in tractive effort due to having a sprung lead/trailing truck, in the model railroad operating conditions and environment that I usually have (ie not running 2-6-0's and short trains but running big engines that are already properly weighted with long heavy trains) is negligible for practical real-world purposes.

Also, it is worth noting that the real railroads were far more interested in weight on drivers than weight on lead/trailing trucks (as long as the axle loadings were beneath the maximum).  The real railroads realized that weight on lead and trailing trucks had only minimal effect on tractive effort.

We wouldn't even be having this discussion, or rather it would not have taken this turn, if it weren't for the fact that some folks desire their model locomotives to outperform the pulling capacity of real locomotives! Again, my personal preference is for operational reliability and good tracking over maximum (model) pulling capacity, but not everyone will have the same approach as me, and that's ok.  It's your railroad--if you don't want the springs, then remove them--it won't bother me one bit at all.

There is a reason that railroads obsessively avoided 4% grades (excepting Saluda).  Even today, there is a sustained 2% to 3% grade in PA over Keating Summit that requires one 3000 horsepower six-axle diesel for every 8 loaded hopper cars (according to a dvd)--and most steam engines did not produce anywhere near 3000 horsepower.  As a design engineer, I'd never think of designing a prototype alignment that steep, because it borders on economic lunacy.  That's also why the PRR built Horseshoe Curve--to avoid what would have been a 3% grade.

2-8-8-4

[jward]

maybe the dynamics are different for steamers, but general electric spent alot of money developing this locomotive. the concept has proven so successful that bnsf has over 300 of them in service, and production of dc drive locomotives has almost ceased at ge.

with regards to the real railroads, almost anything is heavy enough to track well. about the only weight related derailments i came across when i worked in the industry were related to empty intermodal cars being pushed on

[2-8-8-4]

Clarification:  My comments are generally pertaining to the model world.

I also think adding even one rubber tired driver or the bullfrog snot probably has a much greater impact than removing a lead or trailing truck spring from those engines that have them.

As for me--I despise the rubber tires and am glad Bachmann left them off the 2-6-0--and I'd never expect a 2-6-0 to pull a long train (unless it was one of the larger 2-6-0's that ran on the SP in flat portions of California where they were known as "valley malleys" and actually did pull 50 car trains.)

Why am I so against rubber tires?  It has come to light that some of the companies who apply them put them on a non-geared driver, which over time results in excessive wear of the valve gear (holes wear egg-shaped).  Also, if the main rod is one solid piece crossing multiple axles, that by  itself can lead to excessive wear over time.  The "better" model steam engines (at least in the larger sized steamers) have multiple piece main rods just like the prototype.  If the steamer is going to have rubber tires, the multiple section main rods are a good idea for durability due to the forces on the pins during starts and stops--which are exacerbated by the rubber tired axle(s).

Apparently Athearn learned from the problems experienced on a number of Genesis Series steam engines (as reported by at least one reviewer online), and did the SP MT-4 4-8-2 with 3-piece main rods, similar to the prototype.

John

[ALCO1000]

A little weight could help, had it apart and there is room for some if you take out what looks like a bracket that would hold a smoke machine under the stack ,ALMOST LOOKS smoke unit ready if for no electrical contacts at the frame area.
Jack

[ALCO1000]

surprised no one has mentioned it yet but "Bullfrog Snot" the engine and it'll pull alot better, the only downside is whatever driving wheel you apply the snot to won't pickup electrical

Weight IS NOT THE PROBLEM,check the slop in the drive axle journals,they are loose and uneven causing uneven pressure on the 6

drivers,if you put some paint on the drivers,hold the engine to the rail with pressure you will see the wear marks on the wheels ,mine does

not show ay on the center axle compared to the front and rear  ,showing that the contact is uneven with the rail,tested this on a few of
them same thing ,it probably would pull better if all the drive axles were even ,and the drive wheels did not wobble in the loose bearing journals.Bad way to cut cost,needs bearing inserts to even things up and remove the excessive play in the axle journals,check it out ,if they are all like that they need to all go back ,What then? 

[Jerrys HO]

surprised no one has mentioned it yet but "Bullfrog Snot" the engine and it'll pull alot better, the only downside is whatever driving wheel you apply the snot to won't pickup electrical

Weight IS NOT THE PROBLEM,check the slop in the drive axle journals,they are loose and uneven causing uneven pressure on the 6

drivers,if you put some paint on the drivers,hold the engine to the rail with pressure you will see the wear marks on the wheels ,mine does

not show ay on the center axle compared to the front and rear  ,showing that the contact is uneven with the rail,tested this on a few of
them same thing ,it probably would pull better if all the drive axles were even ,and the drive wheels did not wobble in the loose bearing journals.Bad way to cut cost,needs bearing inserts to even things up and remove the excessive play in the axle journals,check it out ,if they are all like that they need to all go back ,What then? 

Jack

Talking about the problems and running it more and more just won't fix the problem.
Try sending it back to Bachmann and get it replaced or fixed as it definitely sounds like yours slipped through the hands of the quality control dept. .

Jerry