This past Christmas, I was given a Mack 15-Ton critter kit from Wiseman Models. It’s an unpowered, all metal HO scale kit with absolutely no room for any of the currently available drive systems (except possibly a modified Stanton drive). So, I made my own![:D]
Everything just barely fits, but I managed to create a design that requires almost no modification of the metal body, and I even fit a small flywheel in there![:D] The motor, flywheel, and gearing are all from NWSL, the wheels are Intermountain 33" semi-scales, the wipers are a Kadee centering spring, and the rest is made from K&S brass stock.
The motor is very tiny at only 10x12x15mm, but it’s surprisingly powerful and runs smoothly and quietly, with very good low-speed torque, and it’s also very power efficient and slower than most other tiny motors. The gears have a total ratio of 32:1, giving my Critter a very realistic speed range. And with the white metal body, it has very good traction for its size.
Now I just have to figure out how to mount the couplers at the proper height and paint the thing. And when I do, I’ll definitely post more pictures.[:D]
Very cool! I always wondered what people did with this kit, other than make a load out of it or park it at the end of a weed-grown siding.
No decoder, though? You must be in DC, but it looks like one of the smallest could be shoe-horned in?
I built this same kit probably 20 years ago, and powered it with … Tenshodo power truck? I think that’s what it was. Wasn’t nearly as geared down, though, but it’d move maybe 3-4 cars. I managed to equip it with a pair of Kadee couplers. I’ll see if I can find it and post a pic or two. It left the cab vacant in case I want to add a decoder, or an interior.
Brad
Pretty neat, as usual!![bow]
The whole design seems to be very simple, which of course is a sign of a good design!
I have the Mack kit. Any chance you could provide a list of part numbers and hints on how you built the drive?
Dave
Oh my…beautiful work there!!
Nice work, excellent job!!
Thanks for sharing & the ideas!
Thanks everyone! I actually wasn’t expecting to get so much response so quickly![:D]
The NWSL parts I used are:
12024-6 24 tooth 72DP wormgear (all gears are Delrin 72DP)
18015-6 15T spur gear (two of them)
18020-6 20T spur gear (three of them)
10000-6 steel worm
10165-9 1 x 2.4mm shaft adapter bushing (to mount the worm to the motor)
1215D-9 motor (tiny, but powerful enough to easily drive a larger N-scale engine!)
435-6 flywheel
And as I said before, I used Intermountain semi-scale freight car wheels (33"). Any 33" freight car wheels with a 3/32" metal axle and standard width needle-point bearings will work, but I like IM’s best.
I’m not sure if I can give any great hints on how to build this chassis, except that I started with mounting the axles, constantly checked to make sure everything fit and worked smoothly in the fully assembled model, and did the center idler gear last to make mesh adjustments easier. It’s all a process of taking things one step at a time, and avoiding short cuts!
Darth Santa Fe
Thanks for the parts list.
Please let me ask a few detail questions:
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You obviously used the wheel base of the 15 tonner to determine your axle spacing. You also adjusted the height of the idler gears above the axles to make them fit between the axles. You said that you installed the center gear last, but you must have had some means of determining the offset for the intermediate idler gears. How did you determine the position of the idler gear axles? If it was guess work just admit it!
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You also managed to assemble all of the axle and idler gear bearings so they were in line with each other. Either you have a very keen eye (which I suspect) or you have a method for alignment. How did you do that?
Hope I am not being a pest.
Thanks for any insight. This is exactly the type of challenge I have been looking for.
Dave
You’re not being a pest, Dave.[:)]
To position the idler axles, I placed the gears without their axles on the side of the chassis, visually positioned them where I wanted, and used the position to make a small starting point for the drill. After the holes were drilled, I mounted the gears to check their mesh, took them back out, and elongated the holes in the direction needed to correct the mesh. Once everything was right, I powered up the mechanism to check where everything needed to go, and fixed it exactly in the position needed with either solder or glue (soldering was only done with the gears out to avoid melting the plastic). Most of the work was visual, and more of it had to do with listening and feeling, and only the axles had an actual measured point to be drilled (the spacing had to be exactly 24.5mm). Not exactly the most professional methods, but they work for me.[:D]
Great Job! I too have one of these Mack units. I was looking at it the other day wondering just how to go about powering it.Thank You so much for posting this. Now for the kicker. How much were the parts?
Ron
All of the parts (including the brass stock, but minus the actual kit) came up to about $70. Pretty expensive, but still cheaper than the pre-built drives like the Bull Ant or Stanton. It costs to get real quality, but it sure makes a better unit than cheaper parts.[:D]
Darth
One more question if I might - is the brass stock used for the chassis 3/16" x 3/8" ( .1875" x .375")? I’m hoping so because I have that size on hand.
Dave
It just so happens that I did use that size! And the tubing has a 3/32" inner diameter. So if you have both of those (as well as some sheet brass for the motor mount), you’re good to go on stock materials![:D]
After waiting some months for good painting weather (it’s been brutally hot until recently), I’ve finally gotten this project finished![:D]
I just brushed the chassis with acrylic flat black. I also made a couple minor adjustments for smoother running and better gear mesh. It’s quieter now and runs more freely.[:)]
The painted and numbered body![:D] Sprayed with Krylon Now gloss black, brushed with Scalecoat II silver, and dull coated with spray can Dullcote.
All finished! Coupler mounting was difficult, but I managed to squeeze Kadee #158 Whisker couplers in there. The all metal body makes this heavier than my other critters, so it’s the strongest puller of all my very small switchers (it can pull about 6 full sized cars). It’s also very quiet and smooth, and is my best runner next to the Grandt Line Boxcab with NWSL gearing and a big coreless motor (still in progress).[:D]
My finished line-up so far![:D] I hope you all enjoyed this little (big) project![:D]
That is a really nice model!!!
Great Work!!
Now all it needs is a couple of the BullDog Hood ornaments off an Ath Mack!!
Hmmm…
Great job as usual Darth!
Whats your next project? [dinner]
Looks great Darth!
Painting the chassis black is a great idea to help hide the visible parts inside the cab.
I just received the #158 couplers and boxes for mine so it will soon be back on the workbench to have them installed.
Dave