Question re 6-wheeled trucks/bogies

[RobertInOntario]

I have several Athearn CNR coaches and their trucks (or bogies) each have 6 wheels (i.e. 3 axels).

A few of these coaches often derail. Sometimes, some of the wheels have been out of gauge and I've replaced those. Also, my layout has some tight curves, around 16.5"R to 18"R. My coaches that have 4-wheel trucks can handle these curves OK but it's hit and miss with these CNR ones.

As a possible solution, I'm wondering if I should remove the middle set of wheels from each truck. From a distance, while operating the layout, I don't think you'd notice that they were missing. My theory is that the 6-wheel trucks have trouble coping with the curves of my layout so it might be solved by turning them into 4-wheel trucks. Does this sound like a reasonable solution and has anyone else had to do this?

Ironically, these coaches currently run better on my layout's tighter, inner loop (that has 16.5 to 17"R curves) than the larger one (that has 18"R to 22"R curves).

I'm also having trouble with the knuckle couplers on a few of these as well. I suspect that the problematic ones are couplers that came with the Athern coaches and are not actual Kadees.

Thanks in advance for any feedback. I've posted some pics of part of one of these coaches as well as a close-up of its 6-wheel truck.

Rob
   
   

[iis612]

Here is my thoughts. If these are a scale 70'+ coaches, then the 6 wheels will not handle the VERY tight radius you are running. The couplers, you need to replace them with the (I don't know which number KD uses for them) the long shank ones. If you are ok with removing an axle, I would remove one from the end of the truck, not the middle. In doing that, your best bet would seem to be get rid of the end axle, closest the couplers. Also, if these coaches have bellows on them, they can cause coupler seperation too. You might want to take them off, and cut a few of the sections out from the inside end.
I am sure that some of the more talented people will speak up and offer more sound advice.
I would also consider widening your radius.

Matt

[nachoman]

Take the center wheel out and see if they run better. If the do, problem solved. You can either leave them that way or find some way to replace them with 4-wheeled trucks. If the problem remains, put the wheelset back in, and look elsewhere for your problem.

[RobertInOntario]

Here is my thoughts. If these are a scale 70'+ coaches, then the 6 wheels will not handle the VERY tight radius you are running. The couplers, you need to replace them with the (I don't know which number KD uses for them) the long shank ones. If you are ok with removing an axle, I would remove one from the end of the truck, not the middle. In doing that, your best bet would seem to be get rid of the end axle, closest the couplers. Also, if these coaches have bellows on them, they can cause coupler seperation too. You might want to take them off, and cut a few of the sections out from the inside end.
I am sure that some of the more talented people will speak up and offer more sound advice.
I would also consider widening your radius.

Matt

Thanks, Matt. I appreciate the coupler and axle info -- I'll try experimenting with this. Yes, it does sound as if I would need different and longer Kadee couplers. Rob

[jim currie]

some of the inherent problems with truck mounted couplers is that derail a lot easier, the photo is my answer to the problem , mine are extra close coupled but you would have to figure out what you would need for the coupler pad mine are .060 the strip in the car is .040. this set up will negotiate a 18 inch rad out of a #4 turnout through a double slip. the cars are between 1/8 and 3/16 of a inch apart .
Jim

[tomustang]

You are probably better off switching the trucks out for 2 axles, the wheel base is still just as long if the middle axle is removed

[RobertInOntario]

Thanks, Jim and Tom, for this feedback. These are all good options to consider.

I'm wondering what is most accurate, though. I suspect that these Athearn coaches are correctly designed (i.e. they originally had 6 wheels per truck on the real thing). If I were to remove one of the wheel-sets, I could at least "fake it" since they would still have the appearance of being 6-wheel trucks. However, maybe there were/are variations in real life. I might do some googling to check!

Thanks, Rob

[Russ Bellinis]

Before you start modifying the trucks, make sure you don't have dips or bumps in the track. If you have uneven track, the axles will tend to lift and lever off the tracks on long 3 axle trucks. The shorter 2 axle trucks may be more forgiving, but if the track is uneven you have not fixed the problem by removing axles from the trucks.

[RobertInOntario]

Before you start modifying the trucks, make sure you don't have dips or bumps in the track. If you have uneven track, the axles will tend to lift and lever off the tracks on long 3 axle trucks. The shorter 2 axle trucks may be more forgiving, but if the track is uneven you have not fixed the problem by removing axles from the trucks.

Yes, I'm afraid that is probably a large part of the problem. I've a couple other threads on my "layout woes" (see: <!-- l --><a class="postlink-local" href="http://www.the-gauge.net/forum/viewtopic.php?f=46&t=380">viewtopic.php?f=46&t=380</a><!-- l -->). Basically, my main layout has been my "learning curve" project and it has a few bumps and uneven sections (because I've moved and relaid track so often). I've tried to correct these but there are still some remaining.

If I can't adequately fix these problems by June, I might set this layout aside and consider expanding my smaller one which actually works very well.

Rob

[BR60103]

I had the original series of these cars (from about 1962). The truck frames were riveted metal and didn't come apart and go back together. I did some awful thinks to the middle axle.
There may be a problem with the coupler mount hitting the steps.
Are the wheels in line? In the picture one axle looks offset.
Can you take the trucks off and run them by themselves?
I had problems with a British 6-wheel bogie -- didn't like Peco double slips.. When a new manufacturer took over the line they seem to have fixed it.

[iis612]

Rob,

I didn't look closely enough at the pic you had posted, and I overlooked the fact that you have truck mounted couplers. I would look closely at what Jim Currie did. Relocate the couplers so they are body mounted, but I would still go with the longer shank ones. Some company, and google is your best bet here, as I have to get my kids up and off to daycare I don't have enough time to search, makes 6 wheel trucks that have a blind wheelset.
If you have uneven spots in the track, like Russ said, you will need to address that. You can also loosen the screw that holds the truck in place, which will allow it to handle small bumps better, but not if the couplers remain truck mounted.

Matt

[Lester Perry]

I had a Roco Flat car with 3 axle trucks a few years ago. It had the same problem. I think it originaly had truck mount couplers Which I changed to body mount. I checked wheel gauge and Alignment. Same problem. Took it to LHS he called me and said its fixed. I picked it up and it still wouldn't stay on the track. I have several other cars with 3 axle trucks with no problem. Did you notice the wording in the first line of this reply

[Puddlejumper]

I don't know about CNR coaches specifically but the Athearn coach is a generic model and has 6 wheel trucks no matter what RR name is on it. Most of the coaches I have ever seen had 4 wheel trucks, while the heavier diners, pullmans, etc. had 6 wheel trucks. I probably would change to 4 wheel trucks, but if you want to keep these trucks there is certainly nothing wrong with experimenting with removing one of the axles. I would not remove the axle closest to the coupler due to the bolster location on the truck, I think you would be inviting more derailments. I would remove either the center axle or the one furthest from the coupler. I really don't think body mounting the couplers will be of any help on these sharp curves. The truck mounted couplers will stay lined up on the centerline of the track whereas the body mounted couplers will swing way outside the railhead and could complicate your current derailment situation, unless you go with complicated swinging draft gear.
I don't know your level of experience, if you feel confident making those type of modifications that's great. For a beginning modeler I would recommend swapping to 4 wheel trucks and leaving the couplers on the trucks.

Dave

[MasonJar]

Hi Rob,

I have a couple of those, and used to run them on 18" R Atlas snap track and snap switches. Always had derailments - when I checked, every single wheelset was gauged too narrow. Swapped out with some replacements (Proto 2000 36" I think), and no more troubles.

You might want to remove one truck and run it around the track to see if the wheelbase is really the problem. There is a bit of side to side play in the truck for the wheelsets, so I'd be surprised if that is the problem. If it is, you could find "blind" wheelsets (i.e. no flanges) for the centres. I'd try Northwest Shortline first - <!-- m --><a class="postlink" href="http://www.nwsl.com">http://www.nwsl.com</a><!-- m --> - although I am not 100% sure they have them.

Second, take a look at the coupler as you move the truck around the track. If it moves significantly to the left or right of the centre line when rounding the curve, that may be the problem. In that case, you can make the modification(s) suggested above - either creating a swinging coupler box, or go to body mounted.

Hope that helps,

Andrew

[Russ Bellinis]

I really don't think body mounting the couplers will be of any help on these sharp curves. The truck mounted couplers will stay lined up on the centerline of the track whereas the body mounted couplers will swing way outside the railhead and could complicate your current derailment situation, unless you go with complicated swinging draft gear.

Dave

Dave if you take a close look at the pic Jim Curry posted, he came up with an ingenious method of "body mounting" the couplers. By mounting the couplers to a long piece of styrene that was mounted to the body on a "pivot screw". he gained the advantage of body mounting (no sideways stress on trucks) with the advantages of truck mounting (the coupler is free to swing to follow curves.)