PRR H10 Remotor

[nscaleSPF2]

I think that some of you have seen, or made, something similar to the following:





It's a resin casting from Jason Smith over a Bachmann 2-8-0 chassis.  Now, I can tolerate a certain amount of non-prototypical detail, but the motor and frame stick out about 5mm from the back of the cab, which puts it the unacceptable range for me.  The mission is to fix this.

The boiler shell itself appears to be pretty close to scale, so the desire is to replace the motor with a shorter one.

Full disclosure on the boiler shell:
1. There were a few voids in the casting that were mostly easy to repair with Bondo (I know, this isn't supposed to work).
2. The shell does sit within a scale inch of the proper ride height.  A future photo will show what it took to get to that point.
3. There is a lot of nice detail on the casting.  Things like handrails and air lines will need to be added.  And the flash needs to go.
4. The casting was warped in both the plan and side views.  The "hunchback" effect in the above photos is not an optical illusion.  Fortunately, a little heat from a hair dryer together with gentle encouragement by hand corrected the warp.

[nscaleSPF2]

Full disclosure on the Bachmann mechanism:



1. Some material had to be removed from the top of the frame to get the boiler to the proper ride height.
2. Some of you probably noticed that the upper fastener that holds the frame together is missing.  It came that way from the factory.  The fastener just below the one that is missing was also stripped.  Don't try to order the plastic nuts that hold the screws from Bachmann.  They don't have them.  I had to make these myself, out of Delrin.
3. The body of the motor is 20mm long.
4. There is lots of room above the frame for a decoder and extra weight.

[nscaleSPF2]

So this is what the inside of the frame originally looked like:



And here is what I am going to try to replace it with:



In the photo above, left to right, are a Mashima 10x15mm can motor, a NWSL coupling, a Delrin thrust washer, the stock Bachmann worm gear, and a Delrin bearing/thrust washer.  Directly below the motor is a homemade steel cradle, to which the motor will get epoxied.  The cradle will be fastened to the frame with a vertical screw.

Never done anything like this before, so we'll see together how it turns out.  Stay tuned for further updates.

[Lemosteam]

Where are you going to move the drawbar pin?  Looks like it hangs out quite a bit too...

[nscaleSPF2]

Where are you going to move the drawbar pin?  Looks like it hangs out quite a bit too...

John,
According to my calculations, the rear of the drawbar pin should be even with the rear of the cab.  So I am not currently planning to move the pin.  Any part of the frame aft of the pin is going to be removed, though.

[victor miranda]

that should work.

you may want to use one of the dogbones in the u-joint package
to allow the motor to sit without having to align it with the wormshaft

roll!

victor

[superturbine]

Looking good!  If you need any replacement parts such as the headlight let me know.

Jason


P.S. be sure and adjust the eccentric crank.

[Cajonpassfan]

Love the project, but confused here....
What are you planning to do for the worm/shaft bearings (with or without the dog bone connection)? The original design relies on a continuos shaft integral to the motor with no other bearings, or am I missing something?
Like I said, love the project; best, Otto K.

(Modified) Okay, I reread your explanation and should have read closer the first time. So you intend to use one delrin thrust washer? Wouldn't it require two?
I'll be following with interest.
Otto

[victor miranda]

Hi Cajonpassfan,

I wondered about the second thrust bearing with the big hole in it.

the thrust can be transferred to the motor...
and the bearing between the worm and motor could be omitted.

.... I had not realized that was how he planned to set it up.

ok skip the dogbone and beardonize the inner bearing.

Roll!
 

[mmagliaro]

You mean that one end of the worm shaft will have the little "horn" on it with the two ears, and will be supported
only by sitting in the NWSL cup that is on the motor shaft, and the other end of the worm shaft will ride in
a thrust washer?

I don't see how that will work.  That horn ball will only hold the shaft straight in one plane,
so it will pivot in the cup all over the place, I think.

[victor miranda]

snip...
I don't see how that will work.  That horn ball will only hold the shaft straight in one plane,
so it will pivot in the cup all over the place, I think.

this is how the Atlas loco work when you remove the inner bearings to quiet them.
 I would call an engineering type solution

everything stays within the correct dimensions to work....
after all, that ball and matching cup are likely to be close to concentric.

I would do two bearing washers and a dogbone (with the two matching cups)
I like thrust on bearing blocks, not motors.
the dogbone solution takes up some more space and costs more to build.
so there are some tradeoffs.

While both solutions do work, I think it is good to know the strengths of each.

victor

[nscaleSPF2]

everything stays within the correct dimensions to work....
after all, that ball and matching cup are likely to be close to concentric.

victor

What Victor said.  At least that is how I am hoping this will work.  Although there is not enough room in there for a dogbone without a lot of fancy machining.

There will be 2 thrust washers, one on either end of the worm.  This will take the axial thrust off of the motor bearings.  The thrust washer closest to the motor has a large i.d., which allows for some misalignment between the motor and worm shafts.

Am currently having some difficulty pressing the cup onto the motor shaft, so you may not hear from me for awhile.  Apparently NWSL thinks that a Delrin part with a 0.047" i.d. is a press fit over a shaft with a 0.059" o.d.  That did not work for me, and I was not able to drill out the hole in the cup while maintaining concentricity between the cup and the shaft...

[carlso]

Jim,

would it not be better to use a good grade silicon rather than epoxy between motor and cradle. that way you could separate the two if needed, epoxy I don't know.

Carl

[peteski]

I was not able to drill out the hole in the cup while maintaining concentricity between the cup and the shaft...

Doing this with a drill bit is very difficult (if not impossible).  For something like that you would need a set of reamers.  It would have been easier to grind down the diameter of the shaft instead.

Are you sure you got the right part?  0.047" is 1.20mm (Minitrix motors use that size shafts) while 0.059" is 1.50mm (more standard size shaft).   Sounds like the part you bought is designed for the 1.20mm shaft.

[mmagliaro]

But the Atlas fix / "Bearden" fix  uses a shaft with a hex end on it, in a hex-shaped recess in the flywheel.
That means that at any point in the rotation, there are always 6 sides symmetrically pushing
on the shaft to keep it centered at that end.  With the two little ears, at any point in the rotation, the
shaft is held centered through one plane, but can  rotate on the axis of the ears in the other.   The other thing the Bearden fix
has is a real bearing on the other end of the worm shaft, not just a washer.  That bearing provides more length
for the shaft to go through, which helps keep the shaft from pivoting at that bearing.

The 2nd thrust washer with the bigger hole in it isn't going to really touch the shaft, if I understand this correctly.  It's
there to take up axial load, not keep the shaft aligned.

I suppose as long as the ball is firmly in the cup, it might work.
I fear the shaft is going to wing around like a jumprope being swung between two children.