Atlas N scale B23-7, B30-7, b36-7 wheelbase ?

[scaro]

HOSAM and a few other sources give a few different figures for wheelbase on the prototype units ranging from 36'2" to 37'10" and I'm wondering what the Atlas chassis is?

Regards

Ben

[davefoxx]

In addition to the Atlas locomotives, don't forget the ALTAS units.   



Seriously, I don't know off of the top of my head, so I will try to measure tonight, if someone doesn't post that information by then.  I don't own a B36-7 yet, but, if I recall correctly, the B23-7 and B30-7 (as well as the U23B) are the same chassis.

DFF

[PGE_Modeller]

HOSAM and a few other sources give a few different figures for wheelbase on the prototype units ranging from 36'2" to 37'10" and I'm wondering what the Atlas chassis is?

Regards

Ben

Ben,

Without dis-assembling the unit, my measurement of an Atlas B36-7 gives the following with an estimated +/- 0.005" tolerance on all measurements:

Total wheelbase:  3.460"  (46'-2" in N scale)
Truck wheelbase:  0.685"  (9'-2" in N scale)
Truck centres:       2.775"  (37'-0" in N scale)

My recollection is that you are probably looking to use it for something in TT scale so the actual (rather than N scale) measurements are more likely to be what you are after!

Cheers,

[scaro]

Thanks Greg

Yes, that's right, I'm trying to see if there is something I can transplant Atlas C628/ C630 trucks into, to give the right wheelbase for an FA1. 37' is what I'm after.  Don't know if the transplant is possible but I've been told it's worth trying.

Cheers, Ben

[atsf_arizona]

Hi, Greg,

It's may possible, with metal-removal surgery, to transplant Atlas C628/C630 trucks into the Atlas B23-7, B30-7, and B36-7 mechanism.

I've never tried that combination, but I was successfully able to transplant Atlas C628/C630 trucks into the Atlas B40-8 mechanism.



See more detailed pictures of how I did that, here:  http://www.pbase.com/atsf_arizona/n_scale_rsd15

Hope that helps!

[daniel_leavitt2000]

That B40-8 chassis is probably one of the most kit bash friendly in N scale. Truck centers are good for some strange engines (mine is under an F40PH-2C), and they take almost any truck you can toss under it.

[scaro]

Oh wow, thank you gentlemen, especially for the tutorial on how to do it. 

[scaro]

If I can be permitted a follow up question, is the mech still bash-friendly if you reverse the trucks? 

Cheers, Ben

[scaro]

Hi, Greg,

It's may possible, with metal-removal surgery, to transplant Atlas C628/C630 trucks into the Atlas B23-7, B30-7, and B36-7 mechanism.

I've never tried that combination, but I was successfully able to transplant Atlas C628/C630 trucks into the Atlas B40-8 mechanism.



See more detailed pictures of how I did that, here:  http://www.pbase.com/atsf_arizona/n_scale_rsd15

Hope that helps!

One additional thing I was wondering, what is the wheelbase of that B40-8 chassis between the 'bolsters' or where they would be, ie the between the wipers on the trucks?

( I realise the centre point on the C628 truck is different since they pivot from a point toward the outer end by about 1.5mm per  truck)

Cheers, Ben

[atsf_arizona]

Hi, Scaro,

Bottom line is the GE Dash 8-40 truck center-center distance is 39' 0".

---------

Here is a dissertation that I did on the wheelbase of the Atlas N scale B40-8 mechanism, comparing it to the
RSD-15, as well as other locos:  http://trainboard.com/highball/index.php?threads/please-somebody-scratch-build-an-alco-rsd-15.78885/page-2

---------

The text is as follows:

---------

Bottom line:

** The Atlas B40-8 mechanism with Atlas C628 trucks gives a very nearly accurate RSD-15 wheelbase
** Accurate within 10 scale inches (only off by 2%)



http://www.pbase.com/atsf_arizona/image/148672757

Thx to many, including Alwyn out of Australia, for helping with this research. Our rivet counting conscience can now go and
build massive numbers of RSD-15's in peace, using this combination of mechanism and trucks.

Would be happy to hear comments/suggestions on other mechanism combo(s) that might be used under a 3D printed RSD-15 shell.

----------------------------------

For those who care, below I've included the calculation, combining data from the following sources:

* Data in the HOSAM websites for the Alco Roadswitcher dimensions: http://www.hosam.com/alco/rsdim.html
* Same website, GE B40-8 truck center to center wheelbase dimensions: http://www.hosam.com/ge/gewhb.html
* RSD-15 plans from Feb 1988 Mainline Modeler, article by Robert Hundman and John Nelsen

--------------------------------

Here's the computation. By looking at the RSD-15 plans:

* The Alco RSD-15 plans show center to center of Alco trimount trucks TRUCK BOLSTERS is 43'-06" (confirming Note 2 in the HOSAM table).

* However, the plans also CLARIFY that distance, by identifying the truck bolster location is 1' 10" OUTBOARD of the center axle
(the plans/pictures worth 1000 words, the plans clarify what the HOSAM table was trying to say)

* In other words, the Alco trimount truck's CENTER AXLE is therefore 1'-10" INBOARD of the TRUCK BOLSTER

* Remembering that the gear tower of the N scale Atlas C628 trucks is directly over the center axle.....

* We therefore need to calculate the prototype RSD-15's center-axle to center-axle distance

* To do that, we calculate: (RSD-15 TRUCK BOLSTER distance) - (1' 10" front truck) - (1' 10" rear truck)
* Plugging in the numbers: (43' 6") - (1' 10") - (1' 10") =
* And that equals 39' 10" is the exactly correct RSD-15 distance center-axle to center-axle

* I used my N scale-ruler to measure my B40-8 chassis with C628 trucks

* From an eyeball / caliper / scale ruler standpoint, my eyeballs sure looks like it measures almost exactly 39' 10" spot on that distance
* The fact that the Atlas B40-8 mech + Atlas C628 trucks gives a distance of 39', i.e. 10 scale inches short...... I can hardly see it

* Certainly, for most people including me, I can't see an N scale 10" difference - especially given our modeling compromises
and manufacturing tolerances for a 1:160 model

* For reference, N scale 10" equals .0625 real inches, which is approximately the diameter of a #52 drill
* (a #52 drill is slightly larger than the #56 clearance drill in the MicroTrains tap/drill set. )
* (i.e. the error in RSD-15 truck spacing we're talking about is same as diameter of mounting hole in MicroTrains 1015 coupler box)

So, next I investigated further, why the wheelbase of the Atlas B40-8 mechanism along with the Atlas C628 trucks, gives an almost dead-on accurate wheelbase.

---------------------------------

To do that, I researched the GE B40-8 center-of-truck to center-of-truck distance, to compare this to the Alco 39' 10" distance

* We see from: http://www.hosam.com/ge/gewhb.html
* That the GE Dash 8-40 truck center-center distance is 39' 0"

* i.e. only 10" off from the Alco RSD-15 center-axle-center-axle spacing of 39' 10"

----------------------------------

* We can see from following photos, the B40-8 truck gear is centered on the 39' mark per B40-8 dimensions
* We can see the C628's gear tower is over the center axle, therefore when I swap the Atlas C628 trucks into the B40-8 mechanism... the C628 truck center axles are thus spaced....... 39' feet apart (pretty close the the 39' 10" that would be exactly accurate)



http://www.pbase.com/atsf_arizona/image/148672764

-----------------------------------

What this means is the Atlas B40-8 mechanism locates the C628 gear towers and center axles, a scale 39' apart

Which is within 10" of what a perfect scale gear tower location of the Atlas C628/C630 trucks should be for an RSD-15
(i.e. 39' scale distance on the model vs. the correct 39' 10" on the prototype.... the error is 2%)

---------------------------------

This happy circumstance happens because the Atlas N scale C628 truck gear tower is centered over the middle axle,
NOT over the actual middle of the truck.

All this is why the Atlas N scale B40-8 mechanism using the Atlas C628/C630 trucks, turns out to be
almost perfect spot on, within 2% match, for correct RSD-15 truck spacing.

Credit is due to Jim Bence, president of the San Diego Society of N Scale club at Balboa Park in San Diego,
for first posting way back about 2004, that he'd discovered this combo of B40-8 mech and Atlas C628 trucks, would work,
and he used that combo under his N scale Southern Pacific RSD-15 he'd built (using Model Power RSD-15 shell).

Hope this may be of use for future reference.

[atsf_arizona]

If I can be permitted a follow up question, is the mech still bash-friendly if you reverse the trucks? 

Cheers, Ben

Hi, Ben,

While I've not tried it, from what I did with the RSD-15 mechanism bash that I described above, I would think you'd be fine with putting the Atlas C628/C630 trucks in reversed orientation into the B40-8 mechanism.   

You'd still have to grind out and 'vertically deepen' the B40-8 mechanism's truck gear tower retaining tab slot, as shown here:



http://www.pbase.com/atsf_arizona/image/148672763

Which you have to do because the gear tower tab retainer height difference between the stock B40-8 truck (higher) and the Atlas C628/C630 truck (shorter) shown here:



http://www.pbase.com/atsf_arizona/image/148672765

Thus requiring me to vertically deepen the gear tower slot depth so that the C628/C630 shorter gear tower tab retainer will fit:



http://www.pbase.com/atsf_arizona/image/148672762

Here's another comparison view of the two trucks, that better illustrates what this 'gear tower retaining tab' is:



http://www.pbase.com/atsf_arizona/image/148672766

I hope that helps.

[scaro]

Thank you sir. 

Yes, very helpful.  These trucks in the Century mech and the B40-8 (sometimes reversed) allow for 30', 31' and 32' and even 33' wheelbases in TT. Which is great if you like RS1s, RS3s and GP30 and GP35s.  Won't bore anyone by getting into how they can be regauged etc.  Better go buy a B40-8.

Regards, Ben