Best Of The TP56/TP70 Kitbash thread N scale

[randgust]

OK, then I'll probably just do a quick mockup in styrene with no detail to check the clearance points, working from what I can scale on that one side shot of the TP70, knowing the wheelbase.    I'm mostly concerned to find out if I have any natural conflicts between actual dimensions and fitting a mechanism into one.   At this point I don't think so.   But I do want to be able to come up with enough rough-cut body to pack in some weight and see how it actually works and performs.

I think a variety of mechanism might work for this one, and designing a mechanism up front may be too much too soon.  I know I can scratchbuild the body, but after seeing your sideframes, if you want to do the body, I'm sure not going to argue.    If we come to some kind of a consensus on how to do this, more power to it, but I'm going the Kato+gearhead+offset worm tower approach.   I just hope we can be relatively faithful to actual dimensions here so that 'tweaking' the body to fit something isn't all that necessary.    Things like the steps in particular are just miserable to scratch and could probably be done easier in RP if the newer materials can print that thin.

I'd take the entire body in that sideframe stuff you used if it holds paint after cleaning.    That's a really impressive material.

However, it's super easy for me to design a mold for insert weights and pour them from Type 160.   Those would cost a mint in RP.   And I've made different weight configurations for different mechanisms before, really pretty easy.  I've got to the point where I'm pouring more and more parts in cast metal where I can for weight.

[u18b]

I had a few moments yesterday and I went through my scrap shell drawer.
Had some surplus Atlas GP shells so I did a quick and dirty walkway.
I think it is a fraction to long for a TP56, but probably perfect for a TP70.

It will be later in the week before I can post anything.

[randgust]

OK, tonight was 'mount the motor and give it a go'...



I'm tinkering it a lot.  But the concept works.

Slow speed:  A.  It creeps.
Pickup:  B+, after I split the front pickup to pickup the center axle, runs over an insulated #4
Traction:  Too soon to tell without weight testing
Noise:  C
Dimensions:  A so far

[Chris333]

Sweet! Did you keep the 3volt motor?

[randgust]

Nope.  Kato 11-105 12v.

One wheel on the Roco truck was decidedly mounted out-of-round on the steel axle.  I moved it to the idler position and the 'wobble' was solved.

I won't be convinced this really works until I can mock-up the body and it fits, but as a concept to power a six-wheel truck with a low-speed gearhead this is promising.   I'm using the 5.14:1 reduction but that is the fast one, you could go a lot slower.  One big advantage with the six-wheel truck is that you're spanning insulated frogs, unlike the 25-tonners, etc., and you've got a better pickup profile.

You can see how I shortened up the universal using the old Roco parts; horn on the worm shaft and cup on the motor shaft, appropriately drilled out.  I've done that before and it seems to work OK.  Motor is mounted on a styrene pad that is just Goo'd to the truck frame and motor.   I've found that it's just easier to cut it free with a knife and then re-glue it if something has to be taken apart down the road.

[dcutting]

OK, tonight was 'mount the motor and give it a go'...



I'm tinkering it a lot.  But the concept works.

Slow speed:  A.  It creeps.
Pickup:  B+, after I split the front pickup to pickup the center axle, runs over an insulated #4
Traction:  Too soon to tell without weight testing
Noise:  C
Dimensions:  A so far

Do my truck sideframes fit?

[narrowminded]

OK, tonight was 'mount the motor and give it a go'... I'm tinkering it a lot.  But the concept works.

Do you have a weight for that assembly as it sits?

[up1950s]

Randy , exactly just what ratio/model gearhead did you decide on ? . I would like to get a few to have on hand to also fit that 11-105 motor  . How did you mate them together ?

[randgust]

I use the 5.14:1 as my standard gearhead for non-logging locomotives.

You need a Kato 11-105 motor, and since I repower those chassis with other gearheads for logging locos, it's all good.

The Gizmoszone 3v motor comes off by removing two screws.  With an abrasive disk in a Dremel, I cut about 1/3 of the Kato motor shaft off, and then grind a "D" shape on the shaft side (with the side of the disk, not the edge) so that the Gizmoszone gearhead pinion fits on the shaft.   Then I simply put the gearhead back on the Kato motor and put in the two screws.   That easy.

I've been testing it with a weight on it.  It's smooth enough I just put it teetering on top of the gear tower.   Tonight I regauged the wheels, reset the contacts, and tested it again.   Sweet.   I'm satisfied.   I thought about changing out the idler to a Kato wheelset, but it's working well enough I'm not going to bother.    I think I'm going to use Atlas GP35 steps and sills and make up a frame at least so I can have couplers and check the component height, but I think it's good.

[up1950s]

Thanks Randy .

[Lemosteam]

I use the 5.14:1 as my standard gearhead for non-logging locomotives.

You need a Kato 11-105 motor, and since I repower those chassis with other gearheads for logging locos, it's all good.

The Gizmoszone 3v motor comes off by removing two screws.  With an abrasive disk in a Dremel, I cut about 1/3 of the Kato motor shaft off, and then grind a "D" shape on the shaft side (with the side of the disk, not the edge) so that the Gizmoszone gearhead pinion fits on the shaft.   Then I simply put the gearhead back on the Kato motor and put in the two screws.   That easy.

I've been testing it with a weight on it.  It's smooth enough I just put it teetering on top of the gear tower.   Tonight I regauged the wheels, reset the contacts, and tested it again.   Sweet.   I'm satisfied.   I thought about changing out the idler to a Kato wheelset, but it's working well enough I'm not going to bother.    I think I'm going to use Atlas GP35 steps and sills and make up a frame at least so I can have couplers and check the component height, but I think it's good.

Randy, you really dont need to mock up a body at all.  As David will attest, just measure the chassis you created, with as many detailed dimensions as you can and provide that to him.  He can model that in CAD and design a body that will fit around it every time., likely with no need of a separate set of steps.  That will aslo provide him with key resting points to level the body on the chassis at the correct ride height.

[randgust]

Ah, but the point is....not can it be done, but is it worth it.    And in order to test that theory, I have to determine how much weight space is there over the gear tower, given the cab dimensions, put in or cast the weight, and then see how the mechanism performs.    No sense at all putting in this much work into a body shell if the end result isn't fairly stellar.   And it's the INSIDE, not the OUTSIDE dimensions, that govern that.  No sense designing a shell that is perfect in all ways except nothing fits in it.   I worked with the designer of the 25-ton GE shell because the way it was designed it was fairly unusable, with some significant modification a stock chassis would fit, well, a squeeze fit.  And I made a few.

The other thing I did last night was to hack up a piece of .040 brass for a frame deck.   Need all the weight I can get,  Side sill is about 15" from what I can see.   

I've had to accept that some critter ideas can work, but possibly never really well. I really love GE 25-tonners, but even after designing and testing about 5 different mechanisms, it's still got a ways to go.   Amazingly tiny, scale size, works, runs, good but not great, little rockets.
I expect 'great' now or it's just not worth doing another critter design.    I'd rate my 'greats' as the Trackmobile, the GE-70 tonner on the Kato drive; any geared steam with a gearhead on the Kato 11-105 frame (including my Climax B), and the Whitcomb 65-tonners with the Gizmoszone gearheads using Tomix parts.  Even the Burro crane is incredibly reliable after sitting around for weeks, and just 'works'. 

I spent an incredible amount of time on both the GE 25-ton and the EMC 40, and while they look great, they are performance divas requiring cleaning, tuning, and testing before you can actually run with them in an operating session.  The EMC 40 has turned out to be more of a highly-detailed flatcar load.  The vertical motor mount on the 25-tonner introduced all kinds of strange issues, worst of which is 'lifting' against the axle, which manages to lift the axle in the pickup cups, leading to stalling.  If everything is PERFECT, it runs 'OK'.  My original 44-tonner with the Faulhaber motor is amazingly quiet and smooth, but has no guts and is difficult to control - it's slated for repowering with a gearhead.

I even got one of the L. G. Thek chassis and tested that, no miracle cure there either, but that was mostly wheel problems.

This design really is the first one I've seen that at least has the potential of just enough length to jam in a horizontal gearhead.   If I can get enough weight in there to get reliable pickup and traction, it may be a winner.  We'll see.

The closest I've come so far to a stock tiny critter is combining the TU7T drive with the Shapeways 25-tonner shell, I've made a handful of these.  Darn hard to make and tune and put in the Kato 12V motor replacing the tiny stock pager, but it can be done.

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[u18b]

Well, yesterday, I got home from a three week business trip.

(been watching this thread from my phone    )

No sign of my two Katp 11-105 chassis.  Maybe in another week.

But I was bustin' to try SOMETHING.

So here is something that won't work- but informs.

I had an old broken SD40-2 Kato truck.   One locking pin at the top of the gear tower was broken.  But the gear was still retained.

So I placed a small Bachmann motor on it with a Kato worm.
The motor is one from a C40-8 Spectrum from 90s.
I like these motors.  Compact 5 pole skew wound.

There is not much room to mount the motor, but I did it.
Unfortunately, the motor is too long in this configuration.
I could trim the truck housing, and fudge the motor closer about 1 mm or so, but I think it would still be too long.

(BTW, it must be on this end because this is the cab end.  I did it on the other end but it is too tall for the hood.)

It runs great.   If track is perfectly clean, it hardly stalls at all even creeping.

This set-up shows how superior the MID Kato truck is.
On that truck,
--the worm is lower,
--the worm is moved to a position FORWARD of axle 2 instead of BEHIND axle 2.   This helps make room for the motor.
--and the worm is attached to the truck.

I'm holding off making any mods to my MID truck until the new chassis come in from Japan.

[randgust]

OK, here's my progress:

.040 brass frame cut and fit - mostly for weight.

Sideframes sanded and attached - David Cuttings Shapeways (again, outstanding).   I managed to sand the original sideframes too thin and snapped it placing it back on the gearbox.  Hour of cursing and pinning and ACC'ing and got it back together.   Got a little too aggressive on the sanding at the corners.

I found an old Con-Cor SW1500 cab weight in the junk drawer, and that will do just fine for initial testing.   I have noticed that if I put the cab weight where I think it should be... it rocks it back on the rear axle.  So weight on the front hood and nose (yet undetermined) will be critical here.  And I'm trying to determine if I laminate up the frame out of styrene or go the 'hard way' and do it in more brass for weight.



I've got end sills/steps cut off the Atlas GP35 but not attached to the frame yet.  Should work OK.

Run tests are encouraging, but oh my, does it take a lot of tweaking and bending on those pickup wipers to get the wheels 'just right' and equalized so it will creep through turnouts.  Got it, but I won't say it was easy.   I still have a little too much pressure on the nose and its riding 'nose high' not sure if getting more weight will cure that or if I have to redo the wiper tension.....again.....

Looks like I'm going to take this one to the bitter end but I don't think my approach is particularly repeatable.   It's going to run well but the degree of difficulty for parts and assembly is getting up there pretty good.    The trick here is finding another three-axle truck, readily available, that has an offset gear tower sufficient to allow mounting the gearhead in the nose and leaving enough space left over.   The Roco apparently will do it, but I just got lucky even finding one of those.  I'm not sure about the body yet.   Pretty easy to scratchbuild but I don't see a whole lot of purpose in making it into any kind of kit master, particularly when I think I'm going to use that thick sill assembly in brass for weight.

[u18b]

Package arrived from Japan today.
Jumped to work.

Kato SD40-2 Mid truck.  Pull the u-joint out.




Kato 11-105 chassis.  New version with 12 v motor.




With the cover off.  Motor easily lifts out.




We just need the motor and the drive shaft.




Drive shaft must be shortened.  So I trimmed it and cut a small piece of small dia K&S brass tubing.




Superglue together.



Styrene support for the motor.



Assembled.  Motor glued down.  Jumper wires soldered.

Ran well.  But after a while (15 min?) of running under DC with my old Tech II Railpower 1400 throttle, motor was hot.
Not good.   
Tiny motor did not like the pulses of that throttle.




So I installed a Digitrax DZ126 decoder.
Purrs like a kitten.
Running at 85 smph for 20 minutes, motor  barely even warm.

Will creep without stalling at 9 smph.