Upgrading the N scale Intermountain SD45-2 with a Kato chassis

[kiwi_bnsf]

i am curious as to what would need to be milled on the Inter mountain frame to achieve similar results?? couid it be done?

The Intermountain chassis is fuel tank is 2mm wider than the Kato Mid Production fuel tank at its narrowest point, so you would need to mill off 1mm from each side for a portion of it. There may also be some interference with the pickup strips, but it looks possible. If your goal is to upgrade the looks of the existing Intermountain chassis + shell, I would go with the Keystone Details dress up kit that @Ed Kapuscinski linked to above, which would avoid any milling.

Even with the frame gaps dressed up, the Intermountain chassis has too many issues for me:
 - inferior IMRC/Atlas HT-C trucks (no traction motor detail, require upgrading to Kato wheels to stop wobbling, less depth of detail).
 - inferior motor and drive train (not as smooth running as a Kato, even after a couple of hours of tuning)
 - decoder sits lower, and motor drive train sits higher, leaving less room for a speaker enclosure and keep alive

The Kato swap addressed all of these (albeit at the cost of a Kato SD40-2, and a hour and a half of milling).

[CRR Chase]

The Intermountain chassis is fuel tank is 2mm wider than the Kato Mid Production fuel tank at its narrowest point, so you would need to mill off 1mm from each side for a portion of it. There may also be some interference with the pickup strips, but it looks possible. If your goal is to upgrade the looks of the existing Intermountain chassis + shell, I would go with the Keystone Details dress up kit that @Ed Kapuscinski linked to above, which would avoid any milling.

Even with the frame gaps dressed up, the Intermountain chassis has too many issues for me:
 - inferior IMRC/Atlas HT-C trucks (no traction motor detail, require upgrading to Kato wheels to stop wobbling, less depth of detail).
 - inferior motor and drive train (not as smooth running as a Kato, even after a couple of hours of tuning)
 - decoder sits lower, and motor drive train sits higher, leaving less room for a speaker enclosure and keep alive

The Kato swap addressed all of these (albeit at the cost of a Kato SD40-2, and a hour and a half of milling).

I agree / and see what your saying. The kato runs better than most any other brand. as far as milling goes.. I would be milling my first frame.. I was just looking at the engine last night and was wondering what needed to be done to current frame. thanks for the insight.

[craigolio1]

I don’t know if it’s worth anything, because I’m in agreement that using a mill is the BEST way to accomplish this…. However for the non mill owning crowd this conversion can be done with a Dremel and files. I did pretty much the same modification to fit my SD38-2 shell on to a Kato SD40-2 chassis. My shell was made using an Atlas GP long hood and so the mech needed to be narrowed. I started with the Dremel 5/16” high speed cutter and finished it with a file. Took some time but it worked. All I’m saying is don’t kill the idea of trying this is you don’t have a mill.

Craig.

[CRR Chase]

I agree / and see what your saying. The kato runs better than most any other brand. as far as milling goes.. I would be milling my first frame.. I was just looking at the engine last night and was wondering what needed to be done to current frame. thanks for the insight.

got to thinking on this topic again.. I wanted to ask, since I dont own any SD40-2 from Kato.. would the trucks from the SD40-2 work in the IM frame? was this attempted?

[randgust]

I did this a while back so my SD45-2 would MU flawlessly with my other Kato SD45/C30 mech units on DC, and I didn't have to mill anything except the shell interior with a Dremel....a little off the frame edge above the tanks with a Dremel as well.   Different mech?   And the other big payoff was significantly better tractive effort.



Link:  www.randgust.com/5649_Flagstaff_2.jpg

Shots of the mech and interior if anybody cares.

And yes, I did wire for handrails and repainted it.

As far as for performance, I also added weight in the long hood, it comes through with a weight of 104.8 grams and 24 grams of tractive effort.   Compared to what?  Try a 'stock' Atlas C630 with 82.4 grams of weight and only 9.5 grams of tractive effort.

Used the same Kato mech under my rebuilt Lima FP45's, and with all that space got 130 grams of body weight and 28 grams of TE for my best-pulling diesel.  That replaced an Atlas SD50 mechanism that never quite worked right and developed a nasty case of gear clicking.

[CRR Chase]

cool... Thanks for sharing this! randgust

[randgust]

When I re-examined the chassis and shell I was reminded of the big empty space left in the long hood end that I filled with lead.  On the DCC side, that's an opportunity to do something there that isn't mentioned here.   I'm still new enough on the DCC side that I can't offer much on that issue and milling the frame 'may' be the only way for enough space, but that big open hood end is still there if you do this.

There's still no substitute for weight.  You see everybody fighting it, but remember that the lighter anything is the more subject it is to electrical glitches in pickup, so milling out part of a frame for a keep-alive seems rather counterintuitive to me when the stock Kato is probably one of the most stable pickup platforms every designed in N.   Mind you I'm playing with those myself so I get it, but it's a last resort in my opinion.

[CRR Chase]

I understand that logic.. Keep alives are ideal for sound. simply to keep the sound program file from restarting due to current interruption.. I will be adding keep alives to all sound that I can..

[C855B]

What are you guys doing with the old IM chassis? If they're rattling around in a junk drawer or box, I’d like to make a deal. I need a parts mule for a 45-2 on my bench and would like to get it off the bench and onto the RR. Not too concerned with the mods at this point; two other IM 45-2s and a T-2 on the RR run OK.

Actually don’t need the whole chassis at the moment - just the trucks. Can anybody assist?

[kiwi_bnsf]

got to thinking on this topic again.. I wanted to ask, since I dont own any SD40-2 from Kato.. would the trucks from the SD40-2 work in the IM frame? was this attempted?

Kato trucks are not interchangeable. Intermountain use the Atlas HT-C Truck which has a different bolster post/spur gear design.

I have seen some people graft sections of Kato trucks onto the Atlas/IMRC HT-C to improve looks (especially where the traction motors should be hanging).


@randgust Thanks for posting your SD45-2 Kato conversion. It looks very nice — especially the lovely replacement handrails

I see you managed to achieve this using a Kato SD40-2 Early chassis. That's where I started, but I found that the frame sat quite high on the chassis supports where the pickup strips are retained. In reality in your photo it looks very good.

The Kato Mid Production is still a better option for my purposes as it includes a nice subframe and it has more room for a speaker.

The ride height works out pretty well (next to a Rapido Centerbeam with correct 36" wheels):

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In terms of weight, the Kato Mid frames are denser that the IMRC, and so my converted SD45-2s end up within 1 gram of the original IMRC loco even after milling and installing capacitors and speakers:

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The stock Kato SD40-2 is slightly more than 10% heavier, but I've not encountered any issues with pulling power.


I've ended up making use of the void at the end of the long hood that is created by converting to the shorter SD40-2 chassis. This has yielded a 9x16mm speaker chamber with more than 1.8 cubic centimetres, and it has a nice clean low end when run at low volume:

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A capacitor really is a must if you are running sound like I am, and I'm happy to sacrifice a couple of grams for the big improvement in reliability — in this case I've used an ISE Power Keeper:

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ESU has recently re-mastered their EMD 20-645 sound file and included a low idle, so I'm a happy camper:

https://projects.esu.eu/projectoverviews/search?cat=18&type=all&q=20-645



The only thing remaining now is to try one of the new CUI 9x25mm speakers to see how this compares:

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Then I'm onto "mass production" of the dozen or so units that myself and my Clinchfield friend @Doug W require.

Cheers

[kiwi_bnsf]

What are you guys doing with the old IM chassis? If they're rattling around in a junk drawer or box, I’d like to make a deal. I need a parts mule for a 45-2 on my bench and would like to get it off the bench and onto the RR. Not too concerned with the mods at this point; two other IM 45-2s and a T-2 on the RR run OK.

Actually don’t need the whole chassis at the moment - just the trucks. Can anybody assist?

The trucks are Atlas part number 490300, but they do not appear to be in stock currently.

I have an increasing number of spare chassis, but shipping from my home in New Zealand probably doesn't make this attractive to anyone in the mainland USA.

Cheers

[CRR Chase]

Kiwi,

i had quoted u but i didn't do something right on the post...

Anyways I hope to get these things modified one day.. just not RIGHT NOW.. I hope also that when I am ready to do work, you are ready to sell those speaker enclosures...

Thanks for the reply about the trucks.

-Chase

[randgust]

Really nice documentation and explanation on your project.    I think the reason I got away with the first mech was grinding down the inside of the shell to drop the shell down further.   Studying my shell vs. yours I think I got the shell height the same, judging from the position of the steps against the trucks.   That speaker attachment is just excellent.

I'm beginning to 'get it' on the capacitor just for sound issues, as I'd test driven an early BLI PA on my layout and every time it hiccupped (which was constantly) it went through the entire sound startup routine again.   Bad enough to have the basic decoder hiccup, but the sound annoyance was far worse.

[C855B]

The trucks are Atlas part number 490300, but they do not appear to be in stock currently.

I have an increasing number of spare chassis, but shipping from my home in New Zealand probably doesn't make this attractive to anyone in the mainland USA.

Oh. Okay. Yeah, the part I really need is the internal gear tower. It’s supposedly in-stock, but they sent the wrong part last time I ordered, didn’t respond to the e-mail about the error (I was nice! I swear!) and ignored the subsequent re-order. I need to try other avenues, though maybe a phone call might shake things loose.

[peteski]

I'm beginning to 'get it' on the capacitor just for sound issues, as I'd test driven an early BLI PA on my layout and every time it hiccupped (which was constantly) it went through the entire sound startup routine again.   Bad enough to have the basic decoder hiccup, but the sound annoyance was far worse.

The old BLI Paragon decoders were really bad for doing that.

Most current sound decoders don't do that (fully reinitialize) anymore, but will still hiccup on short power drops, so yes, some sort of stay-alive or keep-alive circuit is very helpful.