Do You Prefer Six or Four Axle Locomotives?

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Greg@mnrr

Section Hand
I have a mix of six and four axle diesel locomotives on my roster and the six axle locomotives seem exhibit a bad habit of derailing when operating. While I consider my track work was being well constructed, even a six axle might derailment in three hours of operation is one derailment too many. Normally, the layout operates basically trouble free.

I have one section of flex track that for some unseen reason is the area of trouble for the six axle locos. The track is in gauge and has been exmained many times for imperfections.

I am considering switching to all for axle locomotive on the C&MN railroad.

What are your opinions and experiences.

Greg

BNSF Engines.jpg
Photo by Forum member AeroJet taken near Du Plainville, Wisconsin.
 
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bob

Administrator
Staff member
I like 8 axle locos. 2-8-2 for the branch lines, 4-8-4 on the mainline and a nice 2-8-4 Berkshire for fast freights.
Back to your question... your track should be able to handle 6 axle locos no problem, unless you have some really tight curves. Sounds like you’ve got one bad spot? You probably won’t like it, but my answer is simple. Rip that piece out and put in a new one. Make sure it’s smooth and level and even etc. If it’s fine everywhere else, and that’s not some sharp curve, the there’s some flaw there. So replace it. Yes, I know, the new ballast might not match. That’s prototypical. When we upgrade a track, the new ballast doesn’t match the old, even if it’s from the same quarry. The new stuff is lighter colored when it’s freshly crushed. It darkens with age.
 

kjd

Go make something!
Of the locomotives I could go run right now, 22.8% are 4 axle. I don't have derailment problems with one or the other. Actually, I'm surprised I don't have issues since my 'layout' is mostly temporary. As it has been for at least 5 years now. Some of the track is not attached, just laid on the surface.

One junction is 4 Atlas Code 100 switches with two routes in and 4 routes out but it is propped up on random shims and some routes have a grade change going through the junction. I have one locomotive that I machined the wheels to code 88 width so I could narrow the trucks to a more prototypical width. That one occasionally had trouble on malfunction junction but a little more shimming the track and all is well.

All of my 6 axle locomotives are Athearn, Kato or Scale Trains. Some curves are Atlas code 83 24" radius and the others are code 100 flex track about 26" radius.

Greg, is a particular locomotive or brand of locomotive that derails? Is it always the same spot? You mentioned one section of flex track, is it straight, curved, you said in gauge but is it level side to side? How tight are your curves? You've checked that that wheels are in gauge? How do the cars do, do they derail also?

I know I've mentioned it before but my most frustrating derailment issue was with a blue box Athearn SD40-2. One truck would derail if you looked at wrong. I couldn't find anything wrong until I looked at the truck that didn't derail and the little tab that supported the frame was not level. Once that was fixed it was all good.
 

TLOC

Well-Known Member
My preference for my layout is now 4 axles due to a operational change in January, not because I had issues with the 6 axles. Greg, I feel your pain for that section of track but I agree with Bob, rip it out. I had the same problem, the track work was fine, the wheels fine, no bumps but I would have a derail on a 40” radius curve. Finally ripped it out and no issues there since.
TomO
 

cv_acr

Active Member
Six axle units will be more sensitive to track issues than four axle with the longer three-axle truck wheelbase.

We had one specific spot on the club layout that was only derailing some of our Kato SD40-2s. Close inspection determined there was a slight kink or hump (this was a few years ago...) in a curve and the front wheel of the truck would ride up as a result and derail the truck. Then the derailed front wheel would hit a turnout about a foot farther down and really put it on the ground. None of our other units saw any issues here (and it was on a branch line that doesn't usually see the bigger three axle units), only the long-wheelbase SD40-2 truck was sensitive to it but it DID reveal a flaw in the track work, which was repaired and now everything goes through it fine.
 

Selector

Well-Known Member
I have two Athearn Genesis SD-75M models in warbonnet livery that were issued probably around 2006-ish...not sure because I got both of them from that auction site second-hand. I'm strictly a Transition Era guy, so RS-3, and SW-8, and a Train Master H24-66 were all I had to that point in the way of diesels. The SD-75Ms are very finnicky on my tracks if the super isn't close to perfect...which I only most often manage to achieve. So, I have to soften my ballast here and there and shim up the outer rail a bit to get them to stay railed. My other diesels don't seem to have that problem...only the Athearn models. But the sounds are amazingly good, one a Revolution from QSI, the other an original Tsunami.
 

kjd

Go make something!
Some of the early SD70/75s had issues with slightly warped trucks. It is evident if the Loco is placed on a flat surface like a piece of glass. If a piece of paper slips under some of the wheels that's not good. I don't remember what the fix was.
 

MHinLA

Well-Known Member
The OP title is wrong..t's a preference question. But the crux of the post is a: What should I do about a certain problem I am having ?
No biggie. But I, and I'm sure many expected the thread to be about : What type engine should I employ in order to accomplish a certain road job ?
 
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bnsf971

Gomez Addams
Staff member
Some of the early SD70/75s had issues with slightly warped trucks. It is evident if the Loco is placed on a flat surface like a piece of glass. If a piece of paper slips under some of the wheels that's not good. I don't remember what the fix was.
The fix is to remove the truck, sit it on the glass, and gently press, or twist if it is really bad, the truck back into true.
 

D&J RailRoad

Professor of HO
Every once in a while I'll find a place were I get an occasional derailment. A close inspection might show one rail is a bit higher than the other. Doesn't take much, especially if a reverse of that one high rail is close by. Just a little bit of resetting the track usually fixes it.
 

Greg@mnrr

Section Hand
Six axle units will be more sensitive to track issues than four axle with the longer three-axle truck wheelbase.

We had one specific spot on the club layout that was only derailing some of our Kato SD40-2s. Close inspection determined there was a slight kink or hump (this was a few years ago...) in a curve and the front wheel of the truck would ride up as a result and derail the truck. Then the derailed front wheel would hit a turnout about a foot farther down and really put it on the ground. None of our other units saw any issues here (and it was on a branch line that doesn't usually see the bigger three axle units), only the long-wheelbase SD40-2 truck was sensitive to it but it DID reveal a flaw in the track work, which was repaired and now everything goes through it fine.
This is exactly what two of my Athearn locomotives are doing the others are fine which includes Broadway, KATO, Walthers and Atlas. The ratio is approximately 10 six axles to 90 four axle locomotives on the roster. The most troublesome locomotive was repaired after taking Willie's advise and I moved the front leading wheel-set slightly inward and that helped a lot.

The OP title is wrong..t's a preference question. But the crux of the post is a: ' What should I do about a certain problem ? ', question..
No biggie. But I, and I'm sure many expected the thread to be about : What type engine should I employ in order to accomplish a certain road job ?
Like as Chris stated, discussions can found on many Forums regarding how fussy six axle diesels can be over four axle diesels. I can't and will not run a locomotive that has tendency to derail even after three uneventful hours of operation....until either one of two things happen. The locomotive is repaired, regaining my trust or the cause of the derailing is pin pointed and cured.

There have been many cures for six axle derailments that pertain to the locomotive(s) themselves and not the track-work.

Faculty track was my first though and this section has been checked and rechecked. Replacing a section of the flex track is possible, but only after removing track, scenery and rewiring. A lot of work, but it is on a future summer to do list. (Maybe summer 2030.)

I do have some track-work leading into the Pine River Yard that's tight and restricted to four axle diesels only. The layout has radius that varies in radii, but none drops below the recommendations for six axles locomotives other than known sections that are restricted in type of diesel that are permitted to use that section. - following prototypical practice.

MHinLA: My question should asked "Do you have derailment problems with six axle diesels and who was the manufacture"? Short and sweet.

Note: I'm still having trouble with my spell check and it either changes words or overlooks mis-spelled words. 🥃

Greg
 

trailrider

Well-Known Member
For the mostpart, I use 4-axle diesels. The exceptions are P2K E-units, which seem to have enough sideplay in the center axles to handle 18" radius curves and Atlas Snap Track turnouts. Some years ago, before the P2K units came out, there were only some LifeLike E7A's, which ran like a ruptured duck! I took an Athearn Blue Box Alco units, threw out the bodies and stretched the frames and drive shafts. I decorated them in Burlington passenger livery. I did NOT change the truck sideframes, but painted the drop equalizers flat black. From a distance you can't really tell they aren't Bloomberg A-1-A's. Because I did have some problems with 18"R curves, I removed the wheels from the center axles on each truck, leaving the gears on the axles. (The trucks have outside bearings in the sideframes so you don't need the wheels to keep the axles in place. You couldn't do that with the later Blue Box three-axle trucks because they are inside bearing and the wheels keep the gears in proper place.

On my larger steam locomotives (2-10-2, 2-10-4, 4-8-4 and 4-8-2), I use blind drivers on all but the end pair. I also shim the blind drivers so they are .010" above the tops of the rails! Unless you get right down at track level with a light behind, you can't tell!
 

tootnkumin

Well-Known Member
Staff member
For the mostpart, I use 4-axle diesels. The exceptions are P2K E-units, which seem to have enough sideplay in the center axles to handle 18" radius curves and Atlas Snap Track turnouts. Some years ago, before the P2K units came out, there were only some LifeLike E7A's, which ran like a ruptured duck! I took an Athearn Blue Box Alco units, threw out the bodies and stretched the frames and drive shafts. I decorated them in Burlington passenger livery. I did NOT change the truck sideframes, but painted the drop equalizers flat black. From a distance you can't really tell they aren't Bloomberg A-1-A's. Because I did have some problems with 18"R curves, I removed the wheels from the center axles on each truck, leaving the gears on the axles. (The trucks have outside bearings in the sideframes so you don't need the wheels to keep the axles in place. You couldn't do that with the later Blue Box three-axle trucks because they are inside bearing and the wheels keep the gears in proper place.

On my larger steam locomotives (2-10-2, 2-10-4, 4-8-4 and 4-8-2), I use blind drivers on all but the end pair. I also shim the blind drivers so they are .010" above the tops of the rails! Unless you get right down at track level with a light behind, you can't tell!
Yes, avoid heavy behinds if you can. Eat less potatoes.
 

Espeefan

Well-Known Member
It's a question of minimum radius, really. I'm a big fan of "pike sized trains" and their appropriate power. My club supports prototypical length consists, but I get just as much enjoyment out of short peddler freights, mixed trains, and local passenger trains. GP-7/9's; SW's, MP-15's, Alco four axle units, 2-6-0's, 4-6-0's, 2-8-0's, 4-8-0's and maybe a 2-8-2 for the average home layout. Just my humble opinion.
 

cv_acr

Active Member
This is exactly what two of my Athearn locomotives are doing the others are fine which includes Broadway, KATO, Walthers and Atlas. The ratio is approximately 10 six axles to 90 four axle locomotives on the roster. The most troublesome locomotive was repaired after taking Willie's advise and I moved the front leading wheel-set slightly inward and that helped a lot.

Like as Chris stated, discussions can found on many Forums regarding how fussy six axle diesels can be over four axle diesels. I can't and will not run a locomotive that has tendency to derail even after three uneventful hours of operation....until either one of two things happen. The locomotive is repaired, regaining my trust or the cause of the derailing is pin pointed and cured.
To be clear, in our case we repaired the track.

It was only the Kato SD40-2 that derailed there, but it only derailed in that spot. The track was indeed flawed with a kink or twist, it was just the combination of the track flaw and the long three axle trucks that didn't tolerate it. (The engine didn't derail anywhere else on the layout, and it consistently derailed in that exact spot.)

Six axle locos can and should run smoothly and reliably if the track is well laid. But four axle units can be more tolerant to dips and bumps because they don't have the middle axle on each truck.

If you have a lot of derailments, be sure to identify the common piece of information. If the same unit randomly derails all over, carefully inspect it. If different equipment consistently derails at the exact same spot, fix the track. If the same unit always derails at the same spot, observe carefully to see what the trucks and wheels do at that spot - it will likely be a track issue (even if it's only one unit if that's the only spot it derails) that the unit is sensitive to, but also inspect the unit because it could be a combination.
 

santafewillie

Well-Known Member
Answering the title of the thread directly, I like six axle engines more than four, but I like them both. It's just something about the look and heft of SD40-2's and Dash9-44CW's that I like. All of mine whether four or six run equally as well on my layout. I have only one problem combination with a ScaleTrains SD40-2 on an industrial spur. All three of my other identical models have no problems there, and I am currently ignoring it because I don't use SD40-2's for industrial switching anyway.
There's obviously something else amiss here, whether it be the engine itself or the trackwork itself. Many others have already offered some good suggestions, I can't really diagnose the issue from afar. Good luck with your diagnosis.
 




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