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6 Axle Locos & 18" Curves

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6 Axle Locos & 18" Curves
Posted by mrnimble on Friday, June 08, 2018 10:34 AM

A new campaign to upgrade my locomotive roster with 6 axle diesels is not going well.  Last of these I purchased prior to 2013 include Life Like, Athern and Atlas have always run great from the get go.  Recent purchases (and returns) of Intermountain SD40-2 and a Walther Proto SD45 were disappointing.  Both derailed regularly on a couple of 18" radius track I have in necessary locations on the layout - a reverse loop and 90 degree change of direction needed to get into an attic attic space.  These are top of the line $300 locomotives.  Hidden areas, so no concern about looks.

Best I can tell, a lack of lateral axle side play in the trucks is a root cause. Causes flanges to climb the rail.   Removed the side frames to no avail.  In one case there was obvious interference of the truck body and the ditch light wires in the frame preventing the front truck from traveling through its full turning angle.  I say this too from close inspection and comparison with the older locos cited above that the older brands clearly have more mechanical play, or "slop" if you will, in their trucks.

I found some earlier threads on this topic recognizing the problem and recommending a variety of prototypes and manufacturers that have no problems. But I notice these, too, are several years old.  I also notice examining the specs on the boxes of the above late models as well as poking around some manufacruers web sites that the "will run on 18" curves" promotional claim has / is disappearing from many of these products, both 4 and 6 axle.

Botton line - wondering if anyone has any suggestions / recommendations for purchasing late model, contemporary 6 axle diesels?  Thanks, geoff

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Posted by richhotrain on Friday, June 08, 2018 11:37 AM

geoff, I don't have any suggestions / recommendations for operable 6 axle diesels on your layout, but I do agree with your assessment of the problem. You are battling the laws of physics when trying to operate 6 axle diesels on 18" radius curves. In my experience, it is possible to successfully operate 6 axle diesels on 22" radius curves. Is it possible to modify your layout to accommodate 22" radius curves?

Rich

Alton Junction

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Posted by SeeYou190 on Friday, June 08, 2018 11:45 AM

I also have used tight radius curves on my hidden trackage.

.

It amazes me that a Bachmann EM-1 2-8-8-4 will go around an 18" radius curve, but my Kato RSC-2 would not.

.

I have no suggestions. I can tell you these locomotives will go around 18" radius curves:

.

Life Like Proto 2000 SD-7

Athearn Blue Box PA-1

Athearn Old Blue Box Trainmaster

.

I do not plan to purchase any more six axle diesels.

.

-Kevin

.

Happily modeling the STRATTON & GILLETTE RAILROAD located in a world of plausible nonsense set in August, 1954.

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Posted by j. c. on Friday, June 08, 2018 12:00 PM

remove the flanges on the center driver on each truck.

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Posted by Heartland Division CB&Q on Friday, June 08, 2018 12:09 PM

I would not use 18” curves.  Nothing larger than a 4 axle switcher would loom right on such a tight radius. 

GARRY

HEARTLAND DIVISION, CB&Q RR

EVERYWHERE LOST; WE HUSTLE OUR CABOOSE FOR YOU

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Posted by dti406 on Friday, June 08, 2018 12:24 PM

Also, the old Atlas-Roco SD35 and SD24 would go around an 18" curve without any problems, can find them on E-Bay.

Not much else in C-C trucked engines would go around and the Athearn engines mentioned above would derail if the handrail was pushed in to far on the front or back decks and it would catch on the truck causing it to derail, don't ask me how I know this.

Rick Jesionowski

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Posted by doctorwayne on Friday, June 08, 2018 12:51 PM

mrnimble
....wondering if anyone has any suggestions / recommendations for purchasing late model, contemporary 6 axle diesels?

I, and probably most of us here, could probably give some such suggestions, but...

mrnimble
....derailed regularly on a couple of 18" radius track I have in necessary locations on the layout...

...they won't likely avoid the problems which you're encountering.

If the 18" curves on your layout are a necessary requirement, then a corollary to that requirement should be searching for locomotives (not six axle) which can handle those curves.  Recognising your self-imposed limitations will lead you to a better solution, I think.

Wayne

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Posted by bearman on Friday, June 08, 2018 12:55 PM

I think you are correct DrWayne.  I have a lot of 18 inch curves and limit myself to 4 axle diesels, which is no big deal since I like the look of those RS's, SW's and the GP7/9's.

Bear "It's all about having fun."

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Posted by cuyama on Friday, June 08, 2018 1:25 PM

Note also that the arrangement of the 18" curves matters a lot. If there are s-curves without a straight section in between at least as long as the loco, it exacerbates the situation. If using sectional track, apparently minor kinks at track joints can be extra troublesome for the 6-axle power. And any unevenness (tilt) across the railheads can also make things worse.

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Posted by Lone Wolf and Santa Fe on Friday, June 08, 2018 1:26 PM

I rebuilt my layout with 22” radius to fix the problem. There are still a couple of spurs which have 18” but they are only for shorter length freight cars and 2nd generation GP locomotives.
Most Athearn blue box locomotives will run on 18” radius but the six axel diesels will have problems with turnouts next to curves. Tunnel motors need 22” radius. Also cars over 80 feet will need 22” radius. The newer passenger cars with correct couple pocket details will need 24” radius.

As for modern locomotive recommendations: The 4 axle Dash 8-40bw made by Walthers, coming soon by Atlas.

Modeling a fictional version of California set in the 1990s Lone Wolf and Santa Fe Railroad
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Posted by Tinplate Toddler on Friday, June 08, 2018 1:37 PM

The minimum radius on my layout is 11 1/2" and my 6-axle electric has no issue  negotiating a curve this tight without derailing, because it was designed to be able to!

Apparently, a number of manufacturers have no problem to reduce their customer base by excluding those customers, who do not have the space for curves in excess of 18".

That´s stupid!

Happy times!

Ulrich (aka The Tin Man)

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Posted by 7j43k on Friday, June 08, 2018 2:44 PM

Tinplate Toddler

Apparently, a number of manufacturers have no problem to reduce their customer base by excluding those customers, who do not have the space for curves in excess of 18".

That´s stupid!

 

 

Is it stupid to reduce a customer base by compromising the accuracy of a model to get it to run on 18" curves?

 

Ed

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Posted by RR_Mel on Friday, June 08, 2018 4:03 PM

It only takes .03125” of wheel side slop in the wheels of a three axle truck to clear a 18” radius.  In randomly checking three axle trucks most have more than .0360”, some as much as .040”.  I suggest checking for problems with the truck swing/swivel on the locomotives that have a problem.
 
I have several versions of Proto 1K & 2K three axle SD, PAs and E series locomotives and all easily clear an 18” radius as well as Atlas #4 turnouts.  My entire yard/locomotive storage is made up of Atlas #4s with 18” radius approaches and several S turns and the only locomotives that have problems are Bowser 4-8-4 (SP GS4s) and a Bowser Big Boy.  The Bowser GS4s will clear everything in my yard at a creep, the Big Boy was dead meat in my yard so It’s history.
 
I also have several manufactures of large articulated steam and all easily clear an 18” radius.  My minimum radius outside my yard is 24” and minimum radius of my main line is 26” with the majority being 30” or more.
 
 
Mel
 
 
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Posted by Tinplate Toddler on Friday, June 08, 2018 4:22 PM

7j43k
Tinplate Toddler

Apparently, a number of manufacturers have no problem to reduce their customer base by excluding those customers, who do not have the space for curves in excess of 18".

That´s stupid!

 

 

 

 

Is it stupid to reduce a customer base by compromising the accuracy of a model to get it to run on 18" curves?

 

Ed

 

Indeed it is. None of our models is really a true to scale representation of the prototype. Allowing for that little extra leeway in the ability of the trucks of a 6-axle Diesel to swivel to be able to negotiate a 18" radius curve is not at all compromising an accuracy, which exists only seemingly.

After all, show me a prototype railroad with curves equating to a 24" radius in HO scale which operates even a 4-axle Diesel!

 

Happy times!

Ulrich (aka The Tin Man)

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Posted by cudaken on Friday, June 08, 2018 4:55 PM

 Geoff First thing I would check are in gauge. Then make sure the wheel flanges are inalinment and with 3 wheel sets it is hard.

 Next I would make sure the trucks are not warped. Set the engine on a pices of glass and see if the wheels all touch.

 Are you dragging freight or are they derailling with no rolling stock?

 I have a PK1000 Erire Bulit B unit with a warped truck and had to pull the center wheels and make shafts for the gears so front and rear wheels where driven. Pain in the caboose but it is running.

 Far as the Athearn, try pulling the center wheels, much easier than the Proto engines. Just remove and give it a spin.

 Far as 22" turns, god I wish I did it that way and I knew better when I did it! Bang Head But with a little effort you can over come! I run SD 7's and 9's, Ge Ac 6000's, E-6's and E 8's and larger steam with 18" turns.

 Good Luck, Cuda Ken

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Posted by 7j43k on Friday, June 08, 2018 4:57 PM

Tinplate Toddler

 

 
7j43k
Is it stupid to reduce a customer base by compromising the accuracy of a model to get it to run on 18" curves?

 

Ed

 

Indeed it is.

 

I see you agree with my position.  Perhaps?

None of our models is really a true to scale representation of the prototype. Allowing for that little extra leeway in the ability of the trucks of a 6-axle Diesel to swivel to be able to negotiate a 18" radius curve is not at all compromising an accuracy, which exists only seemingly.

 

Yes, model railroading is full of compromises.  But, I think, the fewer the better.  When I started, one compromise was cast-on ladders and grabs.  There are now enough manufacturers that offer models with these details free-standing that I can exclude ALL "cast-on" rolling stock.

And then couplers.  Sergent couplers have arrived.  And I have been using them for awhile.

But.  I don't mind a "little extra leeway", as you call it.  I mind giant leeways in multiple areas.  Like articulated steam engines that aren't.  Articulated.

 

After all, show me a prototype railroad with curves equating to a 24" radius in HO scale which operates even a 4-axle Diesel!

 

OK (though these curves are a bit smaller--more like 11", I think):

 

 

I'll mention also that a UP SW10 had a minimum radius of 14.5 inches, in HO.  A BNSF GP15 has 16.5".  But their big C truck guys do indeed demand a whopping 29".  Or so.

 

Ed

 

 

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Posted by mrnimble on Friday, June 08, 2018 8:23 PM

Thanks everyone for your thoughtful comments.  Good points all.  Disappointed for sure that for the design, engineering and quality of modern HO diesel locomotives that they generally won't accomodate 18" radius track.  Final words on the phone by the Walthers rep to myself and LHS manager "we strive to have all of our (HO) products run on 18" track".  Well, so much for that.  Meanwhile, I'll use several of the tips voiced above to deal with the limitations of my layout.

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Posted by xdford on Friday, June 08, 2018 11:07 PM

Sorry that you have had the issue. I have had to do a little modification to the swing of trucks inside the frames of the locos by filing clearance etc.

In the relatively recent past however I have had to rebuild parts of my layout replacing my flextrack with Peco set track curves in a compound mode and following some other advice on this forum, I super elevated the outside of the curves by about .020" using styrene... I would have gone higher but my main area is a 4x8 and I did not want the curves to have a slot car appearance with the banking.

I found that this improved the running considerably and certainly the appearance and the bigger locos seemed to handle the curves better although I only have a few 18" radius sections.

The other thing to check is that the joins do not have slight burrs that will "trip" the loco. I am still in the testing phase of redoing the layout after a fairly distant move and the Atlas FP7 units I had notoriously found the faults in the trackwork including the tiniest of small burrs at the joiner end of the curves. That situation has now been eliminated by relieving those burrs. If you are not sure, PM me and I will make you a small drawing of what I have done.

You can see what I have done on http://yourmodelrailway.net/view_topic.php?id=15547&forum_id=21 and I feel that I could have saved myself a bit of modification of the frames of the locos I did over the years with superelevation and deburring done earlier.

Hope this helps,

Regards from Australia

Trevor

 

 

 

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Posted by YoHo1975 on Friday, June 08, 2018 11:25 PM
I've been in this hobby for the better part of 33 years. And for 33 years it's been an axiom that 18" radius and 6 axle locos don't mix. Even 22" is getting at the hairy edge in some cases. It sounds like some in this thread have had success with certain models and careful track arrangement. I would note what works, what doesn't and approach any purchase with a mindset that 18"+6axle is never recommended.
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Posted by kasskaboose on Saturday, June 09, 2018 1:26 PM

Bravo to those who can get a six-axle loco to operate on a 18" radius.  While this distance is workable for 4-axle, I don't see positive news for a onger loco.  The debate about what radius work for different loco types creates confusion.  To alleviate, I suggest that people try on a test track before committing the resources to building a larger one with a narrow radius. 

While only on my 2nd layout, I try to follow the motto of going for the broadest radius as possible.  If that's not possible, just have a series of straight tracks working with some turnouts.  Nothing wrong with that!

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Posted by ricktrains4824 on Monday, June 11, 2018 10:55 AM

If you like ultra modern units, get the new run of Bachmann GEVO's with sound, they run just fine so long as you swap the rear couplers to long shank. My Athearn Genesis SD70Ace also runs on 18" radii curves no issues.

My Intermountain GEVO took some additional tweaking, but now also runs well. 

Atlas 8-40C (&CW) units (at least the old run) also work well with 18" curves.

Older runs of Bachmann Spectrum SD45's, 8-40C (&CW) series, and the Athearn BB SD40-2's, and GE Dash 9 and AC44 series units also work well on 18" curves, and can readily be found on the bay, and at train shows. (As do certain runs of the Athearn RTR AC44 series units, but I would test these first, as some seem to snag on details, and others didn't. Maybe it's a certain run had something different?)

And, yes, I have a few 18" radii curves on my layout.

While I would love a bigger layout, that is currently not a option. So, I learn to make do with available space. This includes swapping to long shank couplers, and not running extremely long overhang cars. (80' or longer.) 

Yes, I have successfully made all of these units operate on 18" smoothly, but my 18" is smooth, no kinks or humps. 

I also have a bashed Athearn drive SD70 (with a rail power shell) that will negotiate the 18" curves, but dislikes the #4 turnouts on my yard lead. (Occasionally will pick it, other times does just fine.) I was also given a set of Proto E8 units by a friend, and they will run on 18" curves, but will not take anything under a #6 turnout for anything! 

So, you can run 6 axle diesel units on 18" radii. You just might need to swap out couplers, or tweak in other ways to make them work. 

Ricky W.

HO scale Proto-freelancer.

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1: It's my railroad, my rules.

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Posted by kbaker329 on Monday, June 18, 2018 12:04 AM

I started a post on this years ago. I received some good information and some helpful ideas. I also heard a lot of opinions on 6 axles not belonging on 18” curves. 

In my experience, there is no quick fix. I found that there was adequate lateral movement in Athearn, Proto2000 and Atlas units. It came down to track work.  Track that worked fine with 4 axle units needed tweaks.  I had elevation changes combined with curves that caused two axles to lift the third right over the top of the rail. I had flex track joints that looked square and perfect but needed file work and more. It took a lot of tweaking and caused a lot of frustration.  I just looked for repeat areas and started working on them.  There are still units that I can’t use and I’m debating on whether I want to keep my current layout or rebuild with larger curves  

Perfect track, square joints and zero elevation changes are the only way. It’s not impossible but it will take a lot of trial and error. You will have to decide whether the effort is worth it or not!

HO scale modeling N&W and Union Pacific, somewhere in Missouri between 1940 & 1990!
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Posted by riogrande5761 on Monday, June 18, 2018 6:53 AM

 

Posted by YoHo1975 on Friday, June 08, 2018 11:25 PM

I've been in this hobby for the better part of 33 years. And for 33 years it's been an axiom that 18" radius and 6 axle locos don't mix. Even 22" is getting at the hairy edge in some cases. It sounds like some in this thread have had success with certain models and careful track arrangement. I would note what works, what doesn't and approach any purchase with a mindset that 18"+6axle is never recommended

Pretty much this as a rule. ^

mrnimble
Disappointed for sure that for the design, engineering and quality of modern HO diesel locomotives that they generally won't accomodate 18" radius track.  Final words on the phone by the Walthers rep to myself and LHS manager "we strive to have all of our (HO) products run on 18" track".  Well, so much for that. 

Here is the thing, some engines would require too many compromises in fidelity to "trick" them to operate on very sharp curves, such as 18" radius.  The prototypes they are copying would never operate in real live on much larger curve equvelents.  There are some engines which simply do not lend themselves to sharp curves so don't throw the manufacturers under the bus because, despite their best intentions, it ain't very easy to do.

My suggestion you have a choice; either rebuild the layout with larger curves, even sliightly larger - 22 inch curves will still fit on a 4x8 - or just forget large six-axle engines for the most part.

A mans got to know his limitations.

 

Rio Grande.  The Action Road

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