6 axle diesels and tight curves

[Geared_Steam]

But if there are, I didn’t want them buried underneath simplistic responses like, say, yours, for instance.

Keith Baker

[(-D]

Good for you Keith. [tup]

[kbaker329]

Keith,

If the grades end abruptly it is most likely the lead truck is wheelying off the track. if the top of the grade also has a curve the problem will be worse. If possible run up each grade slowly and watch what the truck does as it goes over the top. If the front axel lofts (leaves the track) the only real solution will be to make a more gradual transition at the top of the grade. I had just the same troubles with my first attempt at a layout and it was one of the major reasons I finally scrapped it. If you can fix the grades it will help. Good luck. J.R.

Thanks for the advice, I’ll take a look at my grades. And thanks to all who gave advice. I do appreciate it.

Keith

[xdford]

Hi Keith,

I also have fairly sharp curves and I can run my F45 around them. I use Peco flex track so a few things here.

1. Instead of going from a straight to a curve, use even a short piece of flex track and make a transition lead into the curve. 6 Axle trucks are notorious in picking edges and the graduation from straight to curve will help.

2. Double check the gauge of the Athearn wheelsets. It is possible for an axle to be slightly out and they are easy to adjust, using an NMRA gauge. You can check if it is the individual axle by swapping the wheelsets around, with the truck undone.

3. If you are using flex track, check that the track around the curve is actually in gauge also. Use model spikes to pin the track back to the right gauge.

4. Older Athearn diesels may have an insufficient clearance in the frame for the truck to swing. It may only require deburring an edge of the cast frame or a very slight widening… you do not need much.

5. Check the metal tab on the truck that the frame sits on. Is it also in need of deburring? Use a larger drill size and twist it with your hand to remove any roughness.

Feel free to contact off list should you need to clarify any of these points xdford47@yahoo.com.au

Regards

Trevor www.xdford.digitalzones.com FYI

[HEdward]

I was looking for responses from people with ideas or who had tried something that actually worked for my situation. If there aren’t any, then fine. But if there are, I didn’t want them buried underneath simplistic responses like, say, yours, for instance.

Didn’t work, though, did it?

There was a real suggestion before he complained. Patience, please. It’s not like trying to call Berks county businesses that you need to use the services of and actually have to call say a thousand times or so before they call you back. The person, I’ve lost track, that insulted the initial question as not wanting an answer, well, he missed the question. The OP wanted OTHER solutions than the obvious. One was in fact given, lets discuss the merits of it. Another was given for gradient changes as well. So it did work, it just got a mud pie tossed into the thread for fun.

[joe27]

I had the same problem with my SD45. I found that the front truck was hitting the coupler box and causing a bind. I just got the Dremel out a put a radius on the back of the box. That took care of the problem and increased the turning angle of the truck

Joe

[shawnee]

Suggest looking at the Kato locos if you have tight curves - any of their SD 6-axle series will handle a 22" curve without any hitch. They’re designed to reun on Kato’s tightest Unitrack curvature, which is 17" - so you’d be fine with any of them.

[johncolley]

Keith, unfortunately this phenomenon is not limited to narrow radius curves. I have a Free-mo module which is a 45 degree curve of 72" radius with easements and suprelevation. Almost all locomotives go through it with no problems in either direction…except one make of SD40-2! Usually only in one direction, but occasionally in the other, enough to be annoying, especially at a meet or show! A lot of analysis with lights and mirrors finally showed the cause! The track had gotten just the tiniest bit of underguage tightness where the superelevation tapered off to “0”. Repeated use of a jeweler’s file along the inside surface of the outer rail in that area to gradually increase the guage, checking frequently, finally eliminated the problem. jc5729 John Colley, Port Townsend, WA

[R_T_POTEET]

Being in N-Scale I can’t address your particular locomotives but I do know that over the years this problem has been addressed frequently. One of the problems encountered with three axle trucks on sharp–read: 18" radius in HO-Scale; 9.8" radius in N-Scale–curves is that the swing of the truck causes it to contact the front steps on hood units causing a derailment of the leading axle on that particular unit. Three axle trucks SHOULD be operated on at least 37.5º curves–21" radius in HO-Scale; 11.5" radius in N-Scale. This renders not only better appearance but more reliable operation.

It should be noted that the Onion Specific designed their 4-8-8-4 steam locomotives to negotiated 20º curves; that’s a 39.5" radius curve in HO-Scale; 21.5" radius in N-Scale.

[R_T_POTEET]

Keith, unfortunately this phenomenon is not limited to narrow radius curves. I have a Free-mo module which is a 45 degree curve of 72" radius with easements and suprelevation. Almost all locomotives go through it with no problems in either direction…except one make of SD40-2! Usually only in one direction, but occasionally in the other, enough to be annoying, especially at a meet or show! A lot of analysis with lights and mirrors finally showed the cause! The track had gotten just the tiniest bit of underguage tightness where the superelevation tapered off to “0”. Repeated use of a jeweler’s file along the inside surface of the outer rail in that area to gradually increase the guage, checking frequently, finally eliminated the problem. jc5729 John Colley, Port Townsend, WA

John, I had the same problem with one of the 1980’s-era Atlas N-Scale RS3s; I would frequently come to griefs at one particular switch on a club layout; no matter which way this locomotive was pointing or where it was located in a consist one truck derailed. I regauged that sonofagun I don’t know how many times; I used an NMRA gauge to check that particular switch I don’t know how many times; I never could isolate any problem although I was told later that I may have had some axle slop on this particular truck–I never did check for that. Anyway, that particular switch had to be changed out and the problem went away.

Don’t ever tell me that gremlins do not reside on model railroad layouts!

[Autobus_Prime]

Always interesting when someone says, "I need help, but I don’t want to hear the real solution.

MR:
Your suggestion of broader curves is a good suggestion; however, it really didn’t address the problem as presented, and so it isn’t a solution. Don’t misunderstand me…it’s a GOOD idea. However, the problem as presented was: using X layout, how can I run Y equipment? So when you said “Don’t use X layout”, it really was more of a sidestep of the problem parameters, than a solution that fit.

(In a way, taking out the center axle sidesteps the parameters too. It’s not a 6 axle diesel after that. :D)

Really, that’s the biggest misconception I see in many areas about solutions…there are no “real solutions”…there are solutions that fit certain problems and solutions that don’t. There are some problems that can’t be solved as stated: “How do I run an engine without fuel?” At least in this hobby, there’s no harm in giving it a try.

Blinding the drivers is an interesting idea. The comment about striking steps is even more interesting. It would suggest that, where this was the limiting factor, blinding the center driver wouldn’t work. Filing the steps or moving them a bit outboard might do it.

I wonder how much variation there is in the pivot point location on 6-wheel model diesel trucks. Pivoting the truck further outboard would reduce the swing in the step area. Maybe that’s one big reason some 6-axle model diesels work on sharp curves, while others of the same size don’t.

[kbaker329]

Thanks again to all for the advice and information. It looks like I have some work to do as far as checking trackwork and my engines. If I can make it work, I’ll definitely post the results. I just can’t give up on seeing high nosed N&W SD45’s running long nose forward pulling a coal train!

Thanks again, Keith Baker

[trainfan1221]

Keith, In case it wasn’t mentioned already, try to have one of those NMRA track and wheel gauge things. They are good to make sure everything is the right spacing and it could help with the tighter curves. Just a suggestion, but I have managed to operate some larger equipment on some pretty small curves in the past. Yeah it didn’t always look the best but it worked. Good luck.

[SMassey]

I ran into a problem once apon a time ago with a couple of Athearn Locos I had. I tried checking the guage and it was fine, I still derailed. What I found was the side frames on the trucks were not allowing enough side play on the wheels. After moving the truck sideframes out a little the problem went away and my Sd40-2s and an SD60 could negotiate an 18"R curve with no problems. I did find a problem with the Genisis SD70MAC, the loco itself would make the 18s just fine but the couplers would not deflect enough and it would throw the first car behind it off the tracks. I didnt fix this issue but I figured if I shaved some of the plastic out of the sides of the coupler box (part outside the loco’s body, if you own one you will know where I am talking). I sold the Genisis in favor of the same loco made by Kato.

I have never had an issue with my Atlas 6 axle locos on tight curves. I cant help you with those, I know that good trackwork will prevail over any modification you do to your locos. If you find that ALL of your 6 axle locos derail in the same exact spot then that is more likely a track issue over a loco issue.

Hope this helps you.

[mlehman]

Keith,

I think GMTracing has a point here. The transition between level track and the grade that he’s talking about is called the vertical curve. Especially when a sharp transition to the grade is combined with sharp horizontal curves, you can run into the intermittent derailment issues you seem to have.

It’s as much about long wheelbase on both the chassis and the the three-axle trucks as anything. This will be much harder to cure than going around small radius horizontal curves. If you can get some more front to back rocking in the the connection at the king pin on each truck, that may help.That will help some with long wheelbase trucks. It’s awful hard to change the wheelbase between truck king pins on a model, though.

[RRTrainman]

All of my 6 wheeler’s run fine on 18"r turns. Sometime your curve is to sharp for it tostart into the curve. I run a transitional curve first before I run the actual curve. Start with a 22"r curve and transit to a 18"r curve. This help set up the trucks on the curve so it prevents derail on the main part of the curve. Even my articulated steam locos run fine. If you are going straight onto a cuvre like 18"r the trucks sometime run off because they don’t have time to react to the cuvre in time. I hope this helps.

[SteamFreak]

Keith,

You’re getting (mostly [:-^]) good suggestions here.

While gauging and checking for interference, another thing to check is that the trucks are level. You can set the loco on a pane of glass and inspect the wheels to make sure that all 12 are in contact with the glass at the same time. It is possible for a truck to be slightly warped, or a burr or other manufacturing defect to cause a wheel or wheelset to ride higher or lower than the rest so that the truck will rock a bit. It sounds like the front wheels on the front truck are derailing, if I read you correctly. If the middle axle is lower than it should be, or the front axle higher, then the front wheels will tend to derail on curves.

Good luck, and let us know what you find.

[Don_Gibson]

I was looking for responses from people with ideas or who had tried something that actually worked for my situation. If there aren’t any, then fine. But if there are, I didn’t want them buried underneath simplistic responses like, say, yours, for instance. - Keith Baker

ADVICE: I don’t think getting ‘snippy’ with ‘Midnight Railroader’ or anyone else, is helpful;

YOU have the problem. YOU chose your equipment. YOU choose to NOT change your radius, - not he. YOU asked for options.

(YOU got them). Now, go do the right thing.

[Autobus_Prime]

I was looking for responses from people with ideas or who had tried something that actually worked for my situation. If there aren’t any, then fine. But if there are, I didn’t want them buried underneath simplistic responses like, say, yours, for instance. - Keith Baker

ADVICE: I don’t think getting ‘snippy’ with ‘Midnight Railroader’ or anyone else, is helpful;

YOU have the problem. YOU chose your equipment. YOU choose to NOT change your radius, (too much work?) - not he.

Now, go do the right thing.

DG:

I don’t want to be rude or start a fight, but I think something should be pointed out, because of the way threads work. This was the original post (boldface mine):

I have a question concerning 6 axle diesels and curves under 22" radius. Most of my Atlas engines and a few of my Athearns handle 18" with no problems. However, a few others like my new Athearn N&W SD45 and my Southern SD40-2, don’t. Has anybody modified a 6 axle diesel to work better on tight curves, i.e. modifying the trucks to allow more slop, allowing the truck to swing more, etc. I’m looking for ideas to try. And please, before the bandwagon starts rolling, I know 6 axle diesels look and run better on curves greater than 22-26 inches of radius, but my layout isn’t going to be changed anytime soon, so that’s what I’ve got. I can live with the overhang but not with the derailments! Thanks for any info.

The OP made it clear he looking for ideas, not ideals.