I checked my charts and realized I'd never dynamometer tested my old gals. Tonight I did. My lead unit weighs in at 115.2 grams and pulled (at full slip) a whopping 26 grams at the knuckle. That's 22.6%. That's what concentrating all that weight on four power axles (inner axles are now idlers) and it's raw brass wheels with the plating long-gone. Traction tires are now the idlers, which is the major change to the trucks. That's heavier than any other diesel I own EXCEPT a Kato (original) F7 and a 1982 Kato GP38. It places it second (behind the Kato GP38) in single-unit tractive effort. The four-unit consist of these that I use pegged my drawbar scale at 100 grams at the drawbar, so I don't know what it could do. It's way more than what I need, actually, but four units just look so good on the point. Now the only thing I have that can probably compare to the Atlas B40 mech (with the same Atlas trucks, maybe a shade heavier) would be the stock C630. Mine weighs in at 82.4 grams (32 grams lighter in a similar-sized six-axle unit) and pulls 9.5 grams for a TE% of 11.5% - back to my 'slippery wheel' issues. But that's what blew me away, I was going to need ten locomotives to do what four can do now. My dynamometer car running 'live' in the unit coal train hits 40g of rolling resistance on the drawbar, so I could 'maybe' get five replacement locomotives to do it... maybe. I've got to do a YouTube of these, because you'd never believe how powerful and slow they are with the old Kato PA1 5-pole motors in them. Every time I resolve to retire them, I'm still unable to find anything that performs as well. They rumble, and rock a hair, but the rpm's are rock steady. They aren't even working hard.
I would love to see any of the RSD's made, as the C&O had several of the "dragon ladies." How do we contact Paul Graf at Atlas? I went to atlasrr.com, but did not see any way to contact them.
Here I always thought the old PA1 motors were high speed motors because of the way the PA1s ran, super high top speed.
I'll have to do a DC comparison test, but I'd say mine are probably a bit faster than an Atlas slow-speed GP or SD24, quite a bit under a Kato SD45, and way slower than an original Atlas SD50 or China classic. The original Con-Cor (Kato-built) PA's were one of only two mechanisms out there that fed the motor shaft onto a spur, that then went into a cup-reduction gear, and that shaft on the worm fixed over the truck gears. The other one that did that was the Rapido GP7/9/30. It tended to be rather noisy, but a lot slower. This is the motor from that era - it's a fairly big motor (went side-to-side in a PA) and barely squeezes into the RSD15 when upright. I also took a bunch of these motors and replaced Atlas Roco (Austrian built) GP motors with them, and those mechanisms are still running today although the shells and trucks are pretty much POS. Remember those awful 3-poles? During that era the Con-Cor PA1's had the only five-pole motor out there that was of any quality at all, and was separately available. I also repowered Trix F-units with 5-pole Sagamis that were a press-fit, another story.
Right on, good advice, Randgust! I haven't weighed my RSD-15 mechanism, nor have I tried to see how many cars it will pull on flat level track. There is some space left for adding lead weight. I will take some clay and see how much we could add and where. I will also then take some weights and see how much additional weight I can get the mechanism up to. Will do that soon and report back here on both counts. Good ideas and discussion, all.
This morning was a little to cold for me to golf, so I decided to try out one of my new tool that I picked up this summer. A Laser Tech, I made a slip-on 1/2" round disk with the reflective tape to slip on the motor shaft. Running the motors at 9 volts for a couple minutes before reading the RPMs. Old Kato, PA1 motor = 27000+, Newer Kato motor = 27000+, Atlas Slow Speed motor = 29000+, (2) Atlas Scale Speed Motor = 13000+.
Hi, Randgust, all, ------- The weight of my RSD-15 shell + modified Atlas B40-8 mechanism with Atlas C628/C630 trucks..... is 80 grams. In comparison, I weighed my C630/C628, that model is also .... 80 grams. I haven't tried yet what number of cars this Atlas B40-8-based RSD-15 mechanism could pull on flat level track, however, I'd guess it's probably similar to the stock Atlas C630/C628 (unfortunately). By comparison to confirm my scale's calibration, my LifeLike FA1 A-unit (a gold standard N scale stump puller) weighs 115 grams. ------- From a space-to-add weight standpoint, in the area directly over the motor, I measure approximately 3/32" (.25 cm) space between top of the B40-8 mechanism and the underside of the Model Power shell. I measure a approx 9/32" (.5 cm) over the rear of the mechanism to the rear of the LED (although weight in this space would obviously block the light from the rear LED). Under the front low hood, there's only about 1/32" of clearance (clearly the B40-8 mechanism is a fortunate good fit for RSD-15 low hood). Here's a (rather poorly lit) side view of the mechanism to help visualize where this space is: Here's another view. ===>Note that in the picture above, you can see the surface on the B40-8 mechanism that determines the under-shell clearances, as the shell rests on the area indicated. <==== Corresponding views of the shell from underneath, including the area where the shell rests on the mechanism: Underside view of front of the shell, showing the low hood end, cab area, and middle of the high hood end: And one more view of the rear underside of the shell (Trainboard post only lets me put in 4 photos per post): http://www.pbase.com/atsf_arizona/image/148672783 ------ Sidenote: you can see why I was very specific on the asymmetric amount of the shaving I did on the front vs. rear of the B40-8 mechanism - the Model Power shell is just a gravity fit over the mechanism, resting on the mechanism pads indicated..... when in motion, the shell is held in place by simple fit of the interior of the shell with the front/rear of the mechanism. ------- Bottom line: there is some space over the motor for a long, flat weight, assuming you can devise some way to keep said weight insulated from the split frame. Clearly weight could be added at the very rear of the mechanism, especially if you're willing to give up the rear light. Fundamentally, there's no space for weight over the low hood end (unless you're doing the RSD-7 high hood version). In the end, I'm not sure how much additional weight we'll be able to put into this particular mechanism. Thoughts? ------ Which mechanism method is better? (Given possibility of future 3D printed RSD-15 shell?) I'm sure this info above gives even more evidence to why Randgust's build-a-N-scale-RSD15 approach by using 20 year old Model Power mechanisms with Kato PA-1 motor - is a viable way to go from a stump pulling power standpoint (and in retrospect, probably less work in terms of getting to the end result of having a decent running mechanism). I tried Randgust's route initially, but I didn't have a ready source of old PA-1 motors, nor could I get the stock Model Power trucks to roll smoothly enough (i.e., without rocking) on the old Model Power mechanisms I got off that auction site. I started down this path of using the B40-8 mechanism route, mainly because I wanted my RSD-15s to MU nicely on DC with Atlas Santa Fe SD24s - the Atlas B40-8 mechanism/motor/C628 trucks combo provided that. I also thought that future possible DCC drop-in board compatibility might be nice. And the Atlas C628/C630 trucks do look a bit better, for what that's worth (not much) at 3 foot viewing distances. ----------- In retrospect, knowing what I know now about the cost involved vs. amount of work involved vs. pulling power equation..... would I have chosen Randgust's version vs. the path I'm on? I could go either way (Randgust's route definitely less expensive and take less time, I think, that's for sure). The B40-8 mechanism combo clearly has the best running qualities, but it gives up a whole bunch of pulling power vs. the Model Power / old PA-motor combo. This creates a new question: are there any other good generally available motors would be good swap into the old RSD-15 Model Power mechanism? Or you all think the old Concor Kato PA-1 motor the best choice? If so, where to buy them? Or just get them by buying old Con-Cor Kato PAs? I myself don't happen to need the pulling power as much as Randgust, on my layout I have no grades nor a heavy Kaiser coal train. The pulling power difference is a definite consideration, in my case it didn't happen to be a determining factor. I'm OK with the (still continuing) path I'm on - it's the journey, not the destination that's important. I have all the pieces/parts/shells now to do three RSD-15 mechanisms and goal to swap onto those mechanisms, 3 sets of 3 shells (i.e. a RSD-15 Santa Fe blue/yellow bookend set, a RSD-15 Santa Fe Zebra set, and a RSD-7 Santa Fe high-hood set), so I'm committed to this B40-8 mechanism approach. Yes, a happily lengthy project set is ahead of me. ------- This discussion / mechanism decision is a very worthwhile one, for those of us considering viability of a future 3D printed RSD-15 shell. Randgust's re-powering method under a reworked Model Power RSD-15 shell, is a worthy alternative, as we all already knew. In the end, I think it's different methods to fit one's particular mix of priorities. Could see it both ways. What's everyone else think about this? I'm sure James Norris (3D designer) would love to know. Comments, thoughts welcome.
I have 4 RSD15s that are retired, I never tried remotoring them because I felt the mechanism wasn't worth it. I see Randy made them work, I just used the Minitrix U28C chassis.
I'd looked at the Trix route as well. At the time it seemed too difficult to grind the mechanisms down that far. I'd probably do that today and not be afraid of it. Anyway, here's the YouTube video of my four units working the YK through Flagstaff - this is a fresh video with all the changes in the Flagstaff model that have evolved over the years. http://youtu.be/USvBYAM9kZY
Very nice Randy. I was so engrossed in the scene that I expected the combi van to drive through the crossing once the barrier arm went up. Cheers Steve
I had one of the original RSD-15's and it was one of the contributing factors I changed from N scale to HO scale. I an talking about the late 70's and early 80's. So many of the locomotives of that time period were miserable running locomotives, The only decent running ones I found at the time were Trix locomotives, and I use the word decent sparingly.
What's really weird about all of this discussion of the RSD15/17 etc... is that ATLAS... of all the model railroading companies has the where-with-all to create these models with the least of effort. They virtually have the chassis from the B40-8 which can be modified at their own factory. They must have all of the necessary drive-line components with all of the hood units they've created over the years. They have the right type of trucks from the C628/630 models. So... why haven't they put this together themselves. What is the difficulty in creating the shells to put over what arguably is their OWN mechanism?
It would still require a lot of work/money to manufacture these model, verses the amount of models they could sell. Not very many roads had these units, (87), and they were split between high nose and low noise. I'd also like to see a GE U33/36 model, there were 499 units made, but again not to many roads had them.
However, the road that matters was the railroad that purchased the majority of them. Santa Fe owned 62 RSD-7's and RSD-15's.
However a company wants to manufacture a N-scale model that was used by several railroads, not just one. I model mostly the EL, I sure don't want a Santa Fe model on my railroad, just like a person modeling the Santa Fe doesn't want a EL model on there's.
At the same time, SP and PRR had them,so,not out of the ordinary for them to have been in Western Pa where you live,and have shown up in EL facilities..I have BN stuff,because GN frequently ran on EL runthrough freights in Scranton.I just finished an F45 in green & black.The SP ran a lot of pool power here in Eastern Pa,especially around Binghamton,Ny.They frequently ran into Pittston on the LV.I'm actually working on a set of low nose RSD15's right now in SP..To me,pool & lease power on my railroad is what really adds interest..Why WOULDN'T you want the excuse of running ATSF on your RR,if there's any chance it ran where you model?
Didn't almost anything western end up on the EL in Binghamton into the 70's? Maybe not the Alco's but I remember lots of western stuff in photos. Cheers Steve
They sure did..It was mostly EMD stuff,but everything ran into Binghamton and the Wyoming Valley both before and after CR.Even now,I see all kinds of stuff,there have been BNSF,CN,and UP locomotives running right past my front door in just the past week..Just yesterday,I saw an SP GE patch job roll by..
You missed the point I was making which was I was invoking the old "anything ATSF was guaranteed to sell" rule.
