Is this a common problem?  Hope its an easy fix.  These are the times when you think steam roller wheels are best It runs pretty well, however hates curved points. It runs through most Peco code 100 or 75 points, however curved ones derail the pony almost every time. Strangely enough, scale code 83 Tillig curved points derail it at the frog every time. Other steamers run through without a bother. Gauge of points and wheel spacing to NMRA standards.
Cheers
Rod

Is this a common problem?  Hope its an easy fix.  These are the times when you think steam roller wheels are best It runs pretty well, however hates curved points. It runs through most Peco code 100 or 75 points, however curved ones derail the pony almost every time. Strangely enough, scale code 83 Tillig curved points derail it at the frog every time. Other steamers run through without a bother. Gauge of points and wheel spacing to NMRA standards.
Cheers
Rod

Rod/all,

I haven’t had derailing issues with the Eureka D50 through curved Peco points. However, the pony truck wheels do drop into flangeways, and this highlights the poor compatibility between RP25-88s and Peco Streamline.

From my experience curved turnouts are where more problems occur. I have paid some attention to mine, smoothing running surfaces and slightly chamfering the vee of the frog (only where necessary).

Several things to try.

1) Small adjustment to the wheel back-to-back. From memory there is about 0.1mm tolerance (14.3 to 14.4mm? – depends on standard used) this might be enough to help you.

2) Careful examination of the troublesome turnouts checking for any burrs, sharp edges or misaligned joints. Especially the point of the frog which may require a small chamfer ground into its tip.

3) If all else fails, you may have to investigate shimming the check rails or flangeways, to bring your Peco points to NMRA standards (or whatever standard you use). Or fit wider wheels to your pony truck.

As noted above, I have run a Eureka D50 through curved Peco points without derailment.

1) Small adjustment to the wheel back-to-back. From memory there is about 0.1mm tolerance (14.3 to 14.4mm? – depends on standard used) this might be enough to help you.

I just checked the D50 that I have been running. The pony truck wheels are set with a back-to-back of 14.5mm. Without looking up the standard, I think that is slightly wide, but in any case it runs well through my Peco pointwork. Also note the pony truck has a light spring that also centres the truck. Perhaps that has been disturbed on your D50?

PS. I don't remember, but I may have regauged the wheels on this D50 to reduce wheel drop through Peco point frogs. It is something worth trying. I don't normally check wheel gauge unless there is a problem.

I recall sometime back a review (perhaps in AMRM?) which mentioned the derailing problem. It was suggested that the spring on top of the pony truck be removed. I did remove the spring as suggested and it did improve things.

I would caution against removing the spring, or otherwise modifying the loco until you have determined the cause of the derailments. While 88 width treads will drop into Peco flangeways, this itself should not derail the loco. Generally derailments occur when the flange rides up onto or over the railhead. You must identify where and why this is occurring – it might actually be somewhere in advance of the pointwork.

Things to check on the loco: Wheelset gauge; Free horizontal movement of the pony truck without fouling cylinders; Free vertical movement of the pony truck especially in the downwards direction. If pony truck movement is restricted (for example by an overtightened pivot screw or a binding spring) the pony truck may be lifted off the track.

Things to check on the track: bumps and dips, superelevation or twisted track leading into the points, misaligned joints, nicks or burrs in rails, ballast fouling flangeways, sagging point blades, etc.

One more thing I just thought of. There is a known problem with the Eureka D50 of excess lateral play in the leading driving wheels. In the worst cases (so I am told) the crosshead may foul the leading crankpin, seizing the motor and burning it out. The fix apparently is to fit thin washers between the back of the leading driving wheels and the frame, thus reducing lateral play. Now, I don’t know whether this could be the cause of poor tracking through curved turnouts? It’s a possibility. I have examined the D50 that runs fine through my Peco pointwork, and yes, the crossheads run dangerously close to the crankpins. I will be making the washer mod to this loco, eventually!

It might be that there is not enough weight pushing down on this pony truck to keep it in place so adding some weight to the pony truck might also fix the problem. A lot of steam locomotives of all types have had this problem over the years though. Some lead or something on top of the pony truck frame might help or some solder wrapped around the axle or may be both to help hold it down on the rails and stop it derailing. If it is light weight then it can be easily lifted up enough to cause a derailment but with a bit extra weight added to it, it might fix this problem. Oh and it might be wise to try with and with out the spring for starters and then add some weight and try again with and without the spring in place till you get an improvement. In other words a bit of trial and error.

Thank  you all
Will spend some time going through the list. Observing the derailment closely, I think it seems the pony wheel climbs over the frog. Nothing else does this, so I wonder if widening the wheel spacing might be the fix. Will report back. I have removed the Tillig point and replaced it with Peco, which did not fix the problem.  Running a straight edge over the points does show everything is flat, and NMRA gauge shows the code 75 track to be extremely close with little room to adjust. Suggests it is indeed the loco?
Cheers
Rod

Thank  you all
Will spend some time going through the list. Observing the derailment closely, I think it seems the pony wheel climbs over the frog. Nothing else does this, so I wonder if widening the wheel spacing might be the fix. Will report back. I have removed the Tillig point and replaced it with Peco, which did not fix the problem.  Running a straight edge over the points does show everything is flat, and NMRA gauge shows the code 75 track to be extremely close with little room to adjust. Suggests it is indeed the loco?
Cheers
Rod

Track gauge is unlikely to be the problem, it is the flangeway width on Peco points that is not NMRA finescale compliant. Adjustment to the wheel back-to-back may help, you might even try narrowing it. Back-to-back should be somewhere in the range 14.3 to 14.5mm (I think, without checking the standards).
Have a look here http://amra.asn.au/standards/
Check the loco first, but if that's the only set of points where it derails, you should look at those points carefully. A small chamfer ground into the tip of the frog might help, but go gently at it!

Hi All,
Thank you for the great help. Today I went through the offerings and found the Peco code75 track to be faultless. At one stage I thought the wire operating the throw was a problem. Finally I propelled 20 Austrains 4 wheel wagons (S trucks) back into the two problem points quite quickly with no derailments. I then pushed them through as fast as the loco would run, and again they ran smoothly.
So its not the track, obviously.
I checked the loco and all wheels are within the NMRA standards fitting loosely in the gauge.
I spent some time watching the pony truck, and it seemed to me to be jamming and not rotating enough to track through the curve. I removed the pony truck, and it is obvious to me why it is derailing. A spring slightly larger and stronger than a coupler knuckle spring is sitting in a hole and the other end bares onto the pony truck. (or have I got that back to front?) Anyway the movement of the pony is limited to a few mm's unless the spring bends, which it does, lifting the boiler up and taking the weight off the front drivers.
The pony truck is metal, heavy and so I removed the spring. The rotation increased to about 6mm either side, and the loco goes right around the layout without derailing anywhere, including crossovers and medium double slips.
I don't like leaving the spring out, however I hate derailments more so.  I think it actually pulls better as well. Perhaps lifting the drivers was another problem, not yet noticed
Thank you all for your help.
Rod

I spent some time watching the pony truck, and it seemed to me to be jamming and not rotating enough to track through the curve. I removed the pony truck, and it is obvious to me why it is derailing. A spring slightly larger and stronger than a coupler knuckle spring is sitting in a hole and the other end bares onto the pony truck. (or have I got that back to front?) Anyway the movement of the pony is limited to a few mm's unless the spring bends, which it does, lifting the boiler up and taking the weight off the front drivers.
The pony truck is metal, heavy and so I removed the spring. The rotation increased to about 6mm either side, and the loco goes right around the layout without derailing anywhere, including crossovers and medium double slips.
I don't like leaving the spring out, however I hate derailments more so.  I think it actually pulls better as well. Perhaps lifting the drivers was another problem, not yet noticed
Thank you all for your help.
Rod

Interesting Rod, and I'm glad you had a win. The D50 I have been running does not seem to have a problem with the spring restricting pony truck movement. It is a fairly recent purchase, so I wonder whether Eureka made a change to the truck or spring to address derailing issues??? If it works without the spring, then all's well.
I looked at the pony truck on Southern Rail SMR 10 class, and they have no spring at all, instead using a weight mounted on top of the pony.

Pleased you got the bottom of this. Although I don't model SG in HO, I was following with interest. My money was on the code 88 wheel being to narrow and dropping into the frog - I'm glad I didn't place a bet!

Interesting Rod, and I'm glad you had a win. The D50 I have been running does not seem to have a problem with the spring restricting pony truck movement. It is a fairly recent purchase, so I wonder whether Eureka made a change to the truck or spring to address derailing issues??? If it works without the spring, then all's well.
I looked at the pony truck on Southern Rail SMR 10 class, and they have no spring at all, instead using a weight mounted on top of the pony.

Yes maybe. It could also be that the factory sourced different springs during the build. So many folk buy locos to sit in storage or on display as well.
I think also that, where I buy something to run out of the box, most dedicated modellers just 'bite the bullet' and modify them till they work.
I have some horrible track on sections of the layout 20 years old, but the new sections are all sitting down well and pretty much expertly laid. Combination of learning through experience and having helpers with good eyes and steady hands

Generally stuff does run well, but perhaps some things just need tinkering with
Cheers
Rod

Most models of steam locomotives for example are made to run on perfect track under near perfect conditions, but who can really put their hand up and say their layout is flawlessly laid. I doubt any one railway modeller could not find something on their layout that could have been done a lot better. But as these locomotives are set to near perfection so to speak little things like this might need to be adjusted or removed to get over a layout. You would not be the first modeller that has had to remove a spring etc to get a model to run properly. Sometimes the spring is way to strong and sometimes it is very weak and does nothing really.

Even things like gear box covers on models done up to tight can make a locomotive do funny things loosen it of just a tad and it runs perfectly though, old brass models had this problem and even some more modern locos also have this problem, no two people seem to get the same sort of problem from identical models though, each has their own malady and you the modeller have to work out how to fix it to get it to run as it should.

But glad you worked it out finally what the heck was wrong and you now have a model that runs as it should.

Have a video here if interested


C50 link
Cheers
Rod

Have a video here if interested

C50 link
Cheers
Rod

Rod, looking at those photos, I think your 50 class is damaged. The right hand crosshead appears to have had a collision with the leading driver crankpin - the fault I mentioned above – spreading the slide bars. Also note you have a busted cylinder drain, though I guess that could have been the result of derailments? Looks like its been through the wars. Are you sure the pony truck spring was correctly located in the first place?

I’ve examined the D50 I have here, on a Peco Code 75 curved point, (inside 30 inch radius) and there is plenty more free movement for the pony truck. The spring certainly isn’t restricting the pony truck travel. And it goes around 16 inch radius curves (which, by the way, I don’t expect any RTR model to manage). Also, your Tillig points look a hell of a lot sharper than 30 inch radius to me, but in any case the 50 should do better than that.

Think you should investigate your loco further!

Interesting Rod, and I'm glad you had a win. The D50 I have been running does not seem to have a problem with the spring restricting pony truck movement. It is a fairly recent purchase, so I wonder whether Eureka made a change to the truck or spring to address derailing issues??? If it works without the spring, then all's well.
I looked at the pony truck on Southern Rail SMR 10 class, and they have no spring at all, instead using a weight mounted on top of the pony.

Yes maybe. It could also be that the factory sourced different springs during the build. So many folk buy locos to sit in storage or on display as well.
I think also that, where I buy something to run out of the box, most dedicated modellers just 'bite the bullet' and modify them till they work.
I have some horrible track on sections of the layout 20 years old, but the new sections are all sitting down well and pretty much expertly laid. Combination of learning through experience and having helpers with good eyes and steady hands

Generally stuff does run well, but perhaps some things just need tinkering with
Cheers
Rod

Rod

Looking at the pics on your blog, with that pony trucks size if its all metal then there is no way a spring is really needed, unless its a very short one. Almost every one of my steam models have had to either have the spring shortened or in most cases removed entirely, in the full removal I have used some lead flashing on top of the pony truck/bogie.  Often the reason also is that the spring will push the truck down onto the rail and lift the lead driving wheel off the track meaning you lose a driving wheel at times.

Rod, looking at those photos, I think your 50 class is damaged. The right hand crosshead appears to have had a collision with the leading driver crankpin - the fault I mentioned above – spreading the slide bars. Also note you have a busted cylinder drain, though I guess that could have been the result of derailments?

Or maybe that loco has been dropped ???

Unfortunately photographs pick up stuff I can no longer see. The loco box had been opened when Ron sold it to me at Canberra last year.   Both the box and the model looked brand new with no show of use on wheels. It has never been dropped by me. I suspect cylinder cock came adrift either in derailments, or  through constant handling checking out the derailment. Anyway I don't see what you do with the valve gear.
Important thing is that it looks fantastic and operates through all my track now
Cheers
Rod

The slide bars are definitely too far apart it appears the bottom one might be the culprit  as it has a decided downward look to it, while the top one appears to be correct and parallel, the cross head will eventually jump out of the side bars and cause you more problem's. I would take a look at your video on a large computer screen or some thing as it can be clearly seen. Or take a screenshot of a still from the video and enlarge it to clearly see it. But trust us it is there.

Also looking at it it comes off at the point blade not at the frog of the point like I thought. It could be two things there the wheelset is not set with the correct back to back gauge, it could be too wide or even too narrow. If the wheelset is correct then the point itself could be wide of gauge in that area. If that is not the problem then it just might be the point blades are not seating properly and leave a slight gap that the flange rides up in and then derails the wheel. All things to look for but still hard to tell from a video.

One other thing could also cause it is if the screw that holds the pony truck is too tightly done up it can impair the ability to go around the corner. So there are a couple of things to keep an eye on.

But fix that slide bar problem pronto or you could do some worse damage to the rods etc.

The slide bars are definitely too far apart it appears the bottom one might be the culprit  as it has a decided downward look to it, while the top one appears to be correct and parallel, the cross head will eventually jump out of the side bars and cause you more problem's. I would take a look at your video on a large computer screen or some thing as it can be clearly seen. Or take a screenshot of a still from the video and enlarge it to clearly see it. But trust us it is there.

Also looking at it it comes off at the point blade not at the frog of the point like I thought. It could be two things there the wheelset is not set with the correct back to back gauge, it could be too wide or even too narrow. If the wheelset is correct then the point itself could be wide of gauge in that area. If that is not the problem then it just might be the point blades are not seating properly and leave a slight gap that the flange rides up in and then derails the wheel. All things to look for but still hard to tell from a video.

One other thing could also cause it is if the screw that holds the pony truck is too tightly done up it can impair the ability to go around the corner. So there are a couple of things to keep an eye on.

But fix that slide bar problem pronto or you could do some worse damage to the rods etc.

David that's a good pick up with the slide bar problem the fact that there is a big gap between the piston arm and top slide bar does not bode well.  Thing is that there does not appear to be any actual bend in either bar, yet the top one also appears to be not directly parallel with the footplate either.

Rod, I would be having a very close look at the slide bars on both sides of the model and see if there is any crack or similar at the back of the cylinders where the slide bars connect, also check if the slide bar is meant to be sitting on the deflector plate and has come away from there.

Was doing a search for other stuff and came upon this post from Rod dating back to 2019. Hope I'm not put in the naughty corner for resurrecting an older post, and hope my contribution is positive, considering it's my first.

Just in the process of building a layout mainly using Peco code 83 track, but the geometry in one particular place required the use of a right hand Tillig curved point PZ85373. And yes, I was experiencing the same problem as Rod, the pony bogie of my Eureka 50 class kept derailing as it passed the frog when travelling in the direction of the point blades. Was quite frustrating as the loco negotiated all Peco code 83 curved points perfectly.

First action was to remove the pony bogie spring which did slightly improve operation over the point momentarily, but the issue soon returned. I suspect the action of removing the spring did improve traction, so I left it out.

The actual problem was caused by the inside pony bogie wheel fouling on the inside front of the cylinder, and in turn being pushed over the check rail, causing the outside wheel to strike the frog. I gently filed about .020" (.5mm) away from the contact area, which didn't detract and all was good.

Funnily enough the leading bogie on the 60 class then started derailing at the same Tillig point, boy, Tillig were about to be the first points into space. Then I noticed the inside detonator amplifier pipe was out of its socket and fouling the bogie wheel. Phew!!

The inside radius of that particular Tillig point is a tad over 500mm.

Cheers, Ray

Was doing a search for other stuff and came upon this post from Rod dating back to 2019. Hope I'm not put in the naughty corner for resurrecting an older post, and hope my contribution is positive, considering it's my first.

Just in the process of building a layout mainly using Peco code 83 track, but the geometry in one particular place required the use of a right hand Tillig curved point PZ85373. And yes, I was experiencing the same problem as Rod, the pony bogie of my Eureka 50 class kept derailing as it passed the frog when travelling in the direction of the point blades. Was quite frustrating as the loco negotiated all Peco code 83 curved points perfectly.

First action was to remove the pony bogie spring which did slightly improve operation over the point momentarily, but the issue soon returned. I suspect the action of removing the spring did improve traction, so I left it out.

The actual problem was caused by the inside pony bogie wheel fouling on the inside front of the cylinder, and in turn being pushed over the check rail, causing the outside wheel to strike the frog. I gently filed about .020" (.5mm) away from the contact area, which didn't detract and all was good.

Funnily enough the leading bogie on the 60 class then started derailing at the same Tillig point, boy, Tillig were about to be the first points into space. Then I noticed the inside detonator amplifier pipe was out of its socket and fouling the bogie wheel. Phew!!

The inside radius of that particular Tillig point is a tad over 500mm.

Cheers, Ray

Hello Ray (autocoupler),

Your experience with that Tillig point is understandable.  The 85373 has nominal radii of 543mm and 934mm for inner/outer portions respectively.  Curved points can and usually are very problematic on the inner curved portion and become worse as the radius reduces.  I even avoid using the Peco SL-(E)86/87 and 186/187 even with a nominal inner radius of 762mm.  

Many modern locomotives, such as the D50 and AD60 (both from Eureka) are built to fine tolerances and have trouble with less than perfect or most ordinary trackwork.  Recommended radii for these locos as I understand it is 605mm or 24".  The Tillig has a radius smaller than 605mm and hence the problems that have arisen, not even taking into account the issues of double curved pointwork.

I have experimented with the AD60 (as an example) and found it will negotiate Peco 3rd Radius (505mm) curves, but not Peco 2nd Radius (438mm) curves.  It must be driven very slowly and on close observation binding of the leading bogie wheelset against the rear of the cylinders is apparent and as a consequence the outer wheel can be observed trying to climb over the outside rail.

You have made some modifications to your D50 to overcome similar problems and can replicate this solution on the AD60.  This addresses the symptoms but not the cause.  The cause is trying to make models designed for larger curves negotiate tighter curves than their design allows.

Happy tracking,

John P

Hello Ray (autocoupler),

Your experience with that Tillig point is understandable.  The 85373 has nominal radii of 543mm and 934mm for inner/outer portions respectively.  Curved points can and usually are very problematic on the inner curved portion and become worse as the radius reduces.  I even avoid using the Peco SL-(E)86/87 and 186/187 even with a nominal inner radius of 762mm.  

Many modern locomotives, such as the D50 and AD60 (both from Eureka) are built to fine tolerances and have trouble with less than perfect or most ordinary trackwork.  Recommended radii for these locos as I understand it is 605mm or 24".  The Tillig has a radius smaller than 605mm and hence the problems that have arisen, not even taking into account the issues of double curved pointwork.

I have experimented with the AD60 (as an example) and found it will negotiate Peco 3rd Radius (505mm) curves, but not Peco 2nd Radius (438mm) curves.  It must be driven very slowly and on close observation binding of the leading bogie wheelset against the rear of the cylinders is apparent and as a consequence the outer wheel can be observed trying to climb over the outside rail.

You have made some modifications to your D50 to overcome similar problems and can replicate this solution on the AD60.  This addresses the symptoms but not the cause.  The cause is trying to make models designed for larger curves negotiate tighter curves than their design allows.

Happy tracking,

John P

Hi John P

Yes, the Tillig curved point mentioned is tighter, but was happy to use it rather than alter the track plan. It's located at a yard exit / entry to a loco depot with all traffic at slow speed anyway.

The 60 class negotiates the point without any alterations, the detonator amplifier pipework which was fouling the pony bogie wheel just required replacing in it's retainer bracket.

I wasn't being critical of the Tillig product, a fine piece of engineering actually, but they do need to be handled with care.

Cheers, Ray