Loco Frame - Split v Standard and motors

Loco Frame - Split v Standard and motors

Postby ConnRiver » Sun May 15, 2016 11:11 am

Yesterday, I read a thread from 2011 (Producing a new US style loco . . .). There was discussion about using a split frame or a standard (HO style) frame. The upshot was that either would work for TT scale.

Question:
Does one style have advantages over another? Maybe electrical pickup/connection?

I've just now disassembled an Atlas "Classic" GP30 N scale loco in an attempt to understand the split-frame style. (The tread, stanchions and handrails are one piece; the tread drops in flush with the walkway structure - clever.) Earlier, I disassembled an HO Proto 2000 GP7, so I have that for comparison.

Question:
Scaro, in the above mentioned thread, you reported that Atlas sells it motor drive train in quantities to third parties. Is this still the case, do you know?

The GP30 hood (by my micrometer measurement) is a scale 4 inches too wide (.025", 76" instead of the prototype's 72"). The hood wall at its thinnest is .017", yielding an interior width space of .441" for the motor.

A TT scale width hood is 0.6" (72"), and if walls are, say, 0.025", that yields an interior width of 0.55". Or, an interior width 0.109" greater than the N scale hood width.

Question:
Can that 0.109" difference yield a larger motor, or is the Atlas N scale motor size the best fit anyway for a TT scale hood diesel?

Question:
If one were to use the Atlas N scale drive train, a split-frame design would be best, would it not, because the motor is already wired to fit into a split frame? Or, wouldn't that matter?

Thanks much, Brian Chapman / Cedar Rapids, Iowa
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Re: Loco Frame - Split v Standard and motors

Postby ConducTTor » Sun May 15, 2016 11:29 am

Standard or split doesn't matter. Either can be good if designed properly.

Atlas' motors can be found on ebay or other places and are a perfect fit for a tt scale hood. However, I prefer the Mashima 1024.
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Re: Loco Frame - Split v Standard and motors

Postby areibel » Sun May 15, 2016 11:59 am

Hi Brian,
The walls are a little thicker on the "new" TT diesels I have, so the interior openings aren't quite .550- On the GP38 it's between .500-.509. So a 12MM wide motor will fit but you'll have to shave a bit to get a 13MM in, and I don't know about having the motor in contact with the sides, if it would be a good thing long term heat wise. The outside dimensions are the same, about .622 if you measure over the doors but I think that's mostly the design of having the doors stand proud of the sides- the actual width is less than .610 outside with primer on it, so there's probably a little variation on the inside from the resin casting.
On one of Jess_Leyva's beautiful SD45's from Shapeways is .533 inside and .605 outside (again with primer on it), so a 13MM motor would fit but again I'd hate to have it tight to the body and run it for a long period, I'd rather have some air around it.

The split frames are interesting, but I don't know if they're really an improvement or just an engineering change to make assembly easier? I haven't read anywhere that it's superior for any real reason, I just wondered if it would be easier to get everything in with additional weight and make it easier to assemble? Put Side A down, drop in the trucks, motor, dogbones, thread the wiring where it needs to go then drop on Side B? If it's getting a lighting or DCC board on top you stick that down, solder the wires and slap on the shell and fuel tank?

Compare that to using a flat frame, the basic assembly would need something to hold the trucks from dropping out (Like the worm clips on a lot of HO and even TT locos), weights have to be glued down to the chassis or inside the shell and then all the wiring added. I'd guess in the smaller scales it's much easeir to bang them out on a semi skilled assembly line with the split chassis version.

If you're using a die cast split frame that has some decent tolerances, I can see where it would be an advantage. But it might add more cost to get one done correctly? I'm not sure if they could be spin cast or poured in a hi temp silicone mold and hold tolerance, that's where someone smarter than me has to get involved!
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Re: Loco Frame - Split v Standard and motors

Postby ConnRiver » Sun May 15, 2016 12:06 pm

ConducTTor wrote:. . . I prefer the Mashima 1024.


Would you say why? In that 2011 thread, you said you were designing for the Atlas drive train (don't you hate that when someone "quotes" yourself back at ya! ;-)

I CAD drew the Mashima 1024 a few years ago for reference. But, when I went shopping, the retail prices caused me to shudder. (Edit: It was the 1224 I drew; iirc, the model number indicates it is 12mm wide, 24mm long. . . .)

Brian C. / Cedar Rapids, Iowa
Last edited by ConnRiver on Sun May 15, 2016 12:44 pm, edited 1 time in total.
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Re: Loco Frame - Split v Standard and motors

Postby ConnRiver » Sun May 15, 2016 12:41 pm

Al,

The 13mm (0.512") seems too wide. A 12mm (0.473") would work well in all hood units, right? Just measured the Atlas GP30 motor assembly width, came up with 0.404". Easy fit, but is it underpowered for TT use? (Although, if a motor is to be "entombed" in a weighty split frame, maybe it's right on the mark?)

Just measured the width of the N scale split frame at 0.430"; the interior shell width of the N scale GP30 is about 0.440", so Atlas appears to think a bit of air is a good thing. With only .005" clearance on each side, maybe heat isn't an issue.

I've made several scans of the GP30 split frame halves, so maybe I'll learn somethin'.

-Brian C.
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Re: Loco Frame - Split v Standard and motors

Postby ctxmf74 » Sun May 15, 2016 2:07 pm

"The split frames are interesting, but I don't know if they're really an improvement or just an engineering change to make assembly easier?"

I think the advantage is to make it easier to fit a motor, wiring, and weight into a production loco but the downside is one can't pop a generic replacement motor into them if the original fails. for limited production TT stuff I'd prefer a can motor that could be replaced if needed with a similar motor or a better coreless motor. The tight engineering of a typical new N loco seems too expensive for a more limited run of TT locos. If I was trying to make a drive for TT locos I'd probably see if NWSL has suitable gear boxes then mate them to a high quality double shaft motor with flywheels. Not the most hi-tech design but proven , reliable,and easy to repair.......DaveB
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Re: Loco Frame - Split v Standard and motors

Postby areibel » Sun May 15, 2016 2:19 pm

Hi Brian,
When we looked at a chassis for the GP Mark from Mark4 said the wall thickness on the RP master would be a little over one millimeter thick, so we started at .500 for an inside width (minimum). Mark designed the original brass etched chassis that folds up, it's about .490 wide but it had special cast resin blocks to hold the shell on and allow a little front to back adjustment, so the body would align with the trucks correctly- you can see them here-
gp38-2-etched-chassis-assembly-t2137.html For a hood unit you're right, 12 MM is going to be the limit. The Mashimas are great motors and come in the 12-24 and 12-20 plus some 10 mm wide versions. I had considered trying to do a GP 38 with two 1024's and some extra weight to try and make a puller but never got that far!

I think this motor in Elmer's instructions was from Branch Lines in the UK, from one of Elmer's PVM kits. It's a little over 11 MM wide. I couldn't find a current website with a quick search, I know I had a PDF of their catalog but that was on a now dead computer- Maybe one of our UK members could shed a little light?

And another place that might be of interest- http://www.micro-loco-motion.com
or here- http://stores.ebay.com/microlocomotion?_rdc=1
They list a lot of different motors on Ebay, some of them look good but I haven't bought from them yet. He must get small odd lots, he had some listed on Ebay that aren't on his catalog so you might have to contact them to see what they have in stock. And I don't know how the "economy" motors would perform, but for the price of some of them they might be worth a shot.
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Re: Loco Frame - Split v Standard and motors

Postby Bernd » Sun May 15, 2016 7:50 pm

I'd go with a standard frame such as in HO models. For the drive I'd use something like this that Hollywood Foundry sells.

http://www.hollywoodfoundry.com/Gurzeler.htm?id=93

Scroll down to the examples. Example 1 I like the best with example 2 as an alternative. I like the "tank drives". Eliminates the gear towers in the shell.

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Re: Loco Frame - Split v Standard and motors

Postby TiTan downunder » Sun May 15, 2016 10:21 pm

The motor in Elmers instructions for the GP38 is from Mashima. It is a M-24F motor. It is my understanding that Branchlines in the UK are just Mashima stockists.

http://www.zephyr.dti.ne.jp/~katumi60/index.html

With a split frame chassis it is advisable to still include pick-up wipers. The first Atlas N scale loco's, in the early 80's, from Kato - RS-3, RSD 4/5, RS-11 etc did NOT have pick up wipers and instead relied solely on the axles resting on the cast pieces in the truck frame for pickup. They worked beautifully when new. Put them in storage for a year or two, as the oil dried out it created a perfect insulator in the metal casting. Strip the chassis down and polish the castings to get contact again. Later production runs all came with pick wipers.
If you can get the Atlas / Kato motor they are very reliable - as good as Mashima - in my opinion. I did not have a lot of luck with the early Atlas / China motors but, I have not bought any Atlas N for some time now.

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Re: Loco Frame - Split v Standard and motors

Postby Richard-B » Mon May 16, 2016 12:59 am

areibel wrote:<snip> For a hood unit you're right, 12 MM is going to be the limit.
The Mashimas are great motors and come in the 12-24 and 12-20...
...and the NOS (New Old-Stock) round (i.e. 'can") NWSL Sagami motors, which are readily available on eBay, come in a number of 10mm, 12mm, and 14mm sizes.

The 1225 and 1425 double shaft versions are particularly useful for diesels...
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