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I'm finishing up an upgrade on a 3rd Rail Big Boy, and on it's final test run, a problem surfaced.  I know I've seen this discussed before, but a search didn't turn up anything definitive on the exact details of a solution.

The blind wheels on the tender short on about half of my Ross switches, and it's easy to see why.  They're considerably wider than the flanged wheels, and they also don't have the flanges to keep them from moving toward the center of the track on turns or even going straight.

The "cure" appears to be to taper the surface of the wheels from the inside edge to maybe 1/3 of the way in so they will not contact the center rail extension that bends toward the outside rail.

3rd Rail BB Tender Blind Wheel Mods

Here's a typical switch that causes the short, most of the switches have a similar shaped rail to reach out and contact these wheels.

3rd Rail BB Tender Blind Wheel Mods N2

The question is, how far back should I taper the wheels, and what angle should I use.  I want to have the taper not be so extreme that the wheel will catch the rail and cause issues, so it needs to be a fairly gentle taper, but enough to keep the wheel from contacting that center real extension.  I'm thinking about 1/3 the width of the wheel, but I figured it was worth asking here to see if anyone has a better plan.

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  • 3rd Rail BB Tender Blind Wheel Mods N2
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@RJT posted:

John I would try shimming the wheel set first to stop them from shifting and then see what has to be done to cure the issue. Shimming them may reduce the amount you have to taper the wheels and it may to consider replaceing the wheels with thinner units also. Just my two cents.

Pretty sure just shimming them isn't going to do the trick, there isn't enough play to solve the problem with those fat wheels.

Replacing them isn't in the cards as they are not standard wheelsets, and I have no idea where I'd find something that would fit the tender.  The axles are a non-standard size for sure.

@Bruk posted:

Id taper the blinds sets to be the same width as the wheels with flanges. By width I mean the surface that be in contact with the rail.

That's my initial thoughts, but I was also wondering if I shouldn't start the taper a little sooner as I want it to be a gradual taper to allow the wheel to slide onto the rail in curves if it's off to the outside.  I've seen this mentioned in the past, but I sure can't find it now.

My sense was maybe to start the taper about where the flange starts on the flanged wheel sets, which would make the taper cover about 40-45% of the wheel surface.  I'm thinking around 20 degrees of taper, but the reason I'm asking is I don't want to screw up the only set of wheels I have!

Pretty sure just shimming them isn't going to do the trick, there isn't enough play to solve the problem with those fat wheels.

Replacing them isn't in the cards as they are not standard wheelsets, and I have no idea where I'd find something that would fit the tender.  The axles are a non-standard size for sure.

That's my initial thoughts, but I was also wondering if I shouldn't start the taper a little sooner as I want it to be a gradual taper to allow the wheel to slide onto the rail in curves if it's off to the outside.  I've seen this mentioned in the past, but I sure can't find it now.

My sense was maybe to start the taper about where the flange starts on the flanged wheel sets, which would make the taper cover about 40-45% of the wheel surface.  I'm thinking around 20 degrees of taper, but the reason I'm asking is I don't want to screw up the only set of wheels I have!

You & Bruk are right on the money,...I’ve been through this before in that exact same application,....20-25 degrees off the backside to the same width as the flanged wheel sets did the trick,....just enough taper to clear the switch, but not so much to cause a slide off,....when you factor the contact patch of the flanged wheels, and the flange itself, you’ll see you’re not putting a whole lot of taper in terms of overall width .....you just need to clean up the fat wheels so they’ll clear, but still sit on the rail in a curve,.....go too wide, and they’ll slide off the rail in a curve,......I snuck up on the one I did,..

Par

I had the same type of problem with a UP 4-8-4' s  tender with the 14 wheel arraingment  John.

I like Ray's plastic wheel advice .  I think they would have to be smaller in diameter though .

My issue came on backing up the tender through some O31 switches.   I tried everything to get the issue resolved . I even made a deep radius on the inside and the outside of the non flanged wheels.      Somewhat succesful , but still had an occasional issue.       I finally gave in and replaced the 14 wheel arraingment with 2 six wheel trucks ............  No problem since, but to the person who wants to keep everything prototypical its a big nada.

I'm glad you had the photo of the wheels because it reminded me of part of the problem.........that front four wheels that rotate against the wishes of the rigid ten wheel arraingment had a tendency to put sideways pressure on  the tender and make it jump the track or drag on part of the switches.       

    I even thought of switching the front two rigid flanged  wheels with the second set of rigid non flanged wheels but never tried it.

Good luck

Last edited by Rich Melvin

May I suggest basing your tapering on the taper found on some production locos with similar tenders? I checked my Lionel Challenger, but they are all flanged - however, I do believe that my MTH Niagara's PT tender (it's not handy right now) has some tapered wheels on some of the center axles.

Some blind drivers on diesels and steamers are tapered in the inside edge, of course - maybe emulate them so far as taper angle and depth of taper are concerned?

Shortening the rail is a non-starter.  First off, this is a customer's locomotive, so fixing it on my layout won't do him any good.  FWIW, I'm planning on tweaking all of the rails on this layout in any case as I have a couple of problem engines that hit the on the side.  However, as wide as these wheels are, I don't think just shortening the rails will do it unless I really went crazy.  However, since it doesn't really have to run on my layout, I'd have to fly out there and shorten all of his rails to actually fix the issue.

I have no idea where I'd find compatible plastic wheels, especially the color of these.  Also, I'm not really willing to go on a snipe hunt in hopes of finding something that would work and look right.

Given the nature of these wheels as well as the size, I think my only option is to modify this set of wheels.   In my mind, the tapering is really the best choice, but I only get one shot at it.  If I screw it up, I have a bigger issue in that I have to find the proper wheels to fix my screwup.  So, my mission is not to screw up!

@D500 posted:

May I suggest basing your tapering on the taper found on some production locos with similar tenders? I checked my Lionel Challenger, but they are all flanged - however, I do believe that my MTH Niagara's PT tender (it's not handy right now) has some tapered wheels on some of the center axles.

Some blind drivers on diesels and steamers are tapered in the inside edge, of course - maybe emulate them so far as taper angle and depth of taper are concerned?

My MTH Niagara was handy but it's tender has all flanged wheels just with a significant amount of lateral play in them.

Shortening the rail is a non-starter.  First off, this is a customer's locomotive, so fixing it on my layout won't do him any good.  FWIW, I'm planning on tweaking all of the rails on this layout in any case as I have a couple of problem engines that hit the on the side.  However, as wide as these wheels are, I don't think just shortening the rails will do it unless I really went crazy.  However, since it doesn't really have to run on my layout, I'd have to fly out there and shorten all of his rails to actually fix the issue.

I have no idea where I'd find compatible plastic wheels, especially the color of these.  Also, I'm not really willing to go on a snipe hunt in hopes of finding something that would work and look right.

Given the nature of these wheels as well as the size, I think my only option is to modify this set of wheels.   In my mind, the tapering is really the best choice, but I only get one shot at it.  If I screw it up, I have a bigger issue in that I have to find the proper wheels to fix my screwup.  So, my mission is not to screw up!

The lathe down in the basement of Hennings is calling your name,....pop the wheels off the axles, true them up in the chuck, and skin em on down,....you’ve got nothing to fear but fear itself,....😉

Pat

After some measurements with O72 curves and the limits of the wheel slop, I've decided to remove 1.25mm from the inside of the wheels an put a very slight chamfer on the inner edge of the wheel.  That still allows margin to prevent the wheels from falling off the rail in a turn in either direction and looks like it allows sufficient clearance for the switch rail.

I'm still going to fix my switches to eliminate this issue, but I have to fix this locomotive anyway.

After some measurements with O72 curves and the limits of the wheel slop, I've decided to remove 1.25mm from the inside of the wheels an put a very slight chamfer on the inner edge of the wheel.  That still allows margin to prevent the wheels from falling off the rail in a turn in either direction and looks like it allows sufficient clearance for the switch rail.

I'm still going to fix my switches to eliminate this issue, but I have to fix this locomotive anyway.

That’s all it takes John,...I fixed my son’s 3rd rail with the exact same issue,...you’ll see it’s not a lot that’s needed,.....and I did exactly what you mentioned, ....I set it up with an O72 piece of track to keep the contact patch on the rail,.....obviously a lathe yields the cleanest results, but I’d surmise with patience, you could obtain the same results chucking up the axle in a drill press and holding light pressure with either a jeweler’s file, or even emery cloth,.....ain’t like you’re cleaning up carbide or case hardened steel,...😉

Pat

@romiller49 posted:

GRJ, you’ve done your job with the ERR upgrade. Perhaps you are trying to fix a problem that the customer doesn’t have on his layout.

He has Ross switches, so unless he's modified them, I suspect he has the problem.  It hit about 60% or more of mine going around my 140 foot main loop, so it's a real problem with Ross switches and the wide wheels.

I'm cheating, I'll send the wheels off to Frank Timko and let him cut them on a lathe, much cleaner than what I would end up with.

Last edited by gunrunnerjohn

I have an MTH Premier Alco DL-109 6-axle diesel that has flangeless tapered wheels on the inner axles. The distance between the outer faces of the wheels is 1-19/32 inches. The distance between the inner faces of the wheels is 1-3/32 inches. The wheel tread (outer face to inner face) is 1/4 inch. The inner tapered portion is 1/32 inch wide and the outer "cylindrical" portion is 3/32 inch wide. The diameter of the "cylindrical" outer part of the wheel is 7/8 inch (42 inches full scale). The width of the metal frame in which the axle is mounted is 31/32 inch. The taper angle appears to be 45 degrees.

MELGAR

MELGAR_2021_0307_01_MTH_WHEEL_TAPERED_PROFILE_ROTATEDMELGAR_2021_03007_02_MTH_WHEEL_TAPERED_PROFILE_ROTATED

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  • MELGAR_2021_0307_01_MTH_WHEEL_TAPERED_PROFILE_ROTATED
  • MELGAR_2021_03007_02_MTH_WHEEL_TAPERED_PROFILE_ROTATED

IMO. The switch is just as at fault as the tender wheel. I don't see how the pickup roller even touches the center rail at that point where the tender is shorting out.

Put a straight edge from center rail to center rail.

It looks like 1/2" or more could be cut back on that rail. ( at least to that first tie) In the short term maybe a piece of electrical tape as an experiment to see if it helps.

3rd Rail BB Tender Blind Wheel Mods N2

Last edited by RickO

John,  the other item you may want to measure and possibly address when you re-install your tapered wheel sets, is the amount of side play between the wheel truck frames.  I am not implying you have excessive play, but I recently had this issue with my Lionel Tenders CB&Q  0-8-0 Yard Goat.  There was so much play that the tender visibly skewed when I pushed cars in reverse.   Ended up adding some #4 black oxide flat washers on the axle shafts when I re-assembled the truck frames.  In my case I was trying to solve a different problem, but excessive end shaft play in these blind wheel sets would allow them to walk toward the hot rail that you're trying to eliminate contact with.  At first I thought the distance between my wheel flanges was the problem, but after measuring them and some other equipment, turned out that wasn't the issue the entire axle was able to move back and forth over 0.090".

I did check the side play when I was deciding how to deal with this.  There actually isn't that much, this is an early 3rd Rail and all those wheels are sprung in the sideframes.

@RickO posted:

IMO. The switch is just as at fault as the tender wheel. I don't see how the pickup roller even touches the center rail at that point where the tender is shorting out.

Put a straight edge from center rail to center rail.

It looks like 1/2" or more could be cut back on that rail. ( at least to that first tie) In the short term maybe a piece of electrical tape as an experiment to see if it helps.

3rd Rail BB Tender Blind Wheel Mods N2

I don't disagree Rick, but I'm also trying to solve the problem with the stock Ross switches, this is what they all have.  However, for my layout, I am planning on trimming that rail as it's not really clear what it brings to the party.  I think they continued it a bit too far in an effort to minimize the dead spot, and it's actually creating more issues than it's solving.

Last edited by gunrunnerjohn
@naresar posted:

My MTH Niagara was handy but it's tender has all flanged wheels just with a significant amount of lateral play in them.

Interesting - so does mine, now that I had a chance to look at it. Then I figured that I must be thinking of Lionel's...uh, no - I looked at mine. Not on the Williams brass Niagara, either, as I recall.

So - just exactly what was I remembering?   (Don't get old.)

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