Clarktor 6 Tow Tug in 1/33rd Scale

[Bomarc]

Today seems as good a day as any to pull the trigger on this one.

So for awhile now, I’ve been hinting that I wanted to do a small something to satisfy the “wheeled vehicle” theme of this year’s IPMC at the end of October. Behold:



I’ve always thought Bruce Clemen’s little freebie Clarktor 6 (AvantCard - Paper Models ) was neat, so using that as a starting point: “I’m going in......”

Spent these past few weeks collecting data and whatnot. Turns out there’s a ton of good info on the Internet about this tug. Besides Bruce’s site, there's a web page of a guy who restored one for airshow events:

DocThrock's Clarktor 6 MILL-44 1942 aircraft tug

There’s a bunch of them in museums, a couple of examples:

Military Museum Of Southern New England - Clarktor 6 Airport Tug
Factsheets : Clarktor-6 Towing Tractor

But probably the most complete, “one stop shopping” site for Clark tug info is a Yahoo Group called (strangely enough) "Clark Tugs". Here they have manuals, factory drawings, parts list, just “tons-o-stuff”. It's really meant for owner/restorers of the tugs, but it's a treasure trove of info for modelers too. I downloaded these two manufacturers spec brochures from 1942 and 1948 respectively from there:



Lots of other stuff there too. If you already have a Yahoo account group membership initiation is quick and painless (“Thank you Sir…may I have another?”).

Based on everything I found, it looks like Bruce’s tug was a just one variation of the many configurations the Clarktor 6 Tug came in. I decided that while I would use his model as a starting point, I would be deviating early and often down my own path for this project (surprise!). Since I wanted to make my mine a pre-WWII era Navy tug (I may want to display this model alongside something else I have), I re-colored the two sheets of Bruce’s model, changing the yellow to gray (don’t worry, I emailed Bruce about it. He knows of my plans…insert evils laugh here):



I also recently bought a sheet of Bruce’s diamond plate in 1/32nd scale. This, coupled with the tiny nuts I bought from him previously, should come in handy:



Looking through all the literature, I settle on the specific version of the tug I wanted to model:



The above is from the ’42 brochure and it’s the “Mill-44” model. I like the louvered side cowlings. The more common cutout style you see in the blue one at the beginning of this post and in the '48 brochure above started in 1940. But I like the early model. Here it is in action (from the “Clark Tugs” group):



What’s that thing in the background? Even here, the hood side panels have a variation in the pattern of the louvers (latches on top). The ’48 brochure included a factory drawing which I used to help whip up some drawings, adjusting for the specific model I was gunning for:






I’m adding the headlights too. Lastly, as a certain well known Colonel who frequents these halls can attest to, I never start something without first assembling all my accumulated data in a 3-ring binder:




Time to actually make something. Looking over the tug, the tires and their rims seem the most complicated parts, so that’s where I’m starting. Cut out what I needed from mat board:



The above should make it apparent why I did all that tinkering with my circle cutter. I wanted to take advantage of the center point holes made from the cutter and drill through to keep things aligned. To keep the mat board from fraying when I drilled, I applied a drop of CA glue in their centers:



Makes for cleaner holes:



I kept a few of the center discs to help with alignment when I glue these stacks together. First two down:



Next two in the fender washer “press”:



Here’s the advantage of using the centers. After taking the stack out of the press:



Center disc removed:



The outer ring is pretty much aligned to the axis of rotation. With the stacks all glued up, nuts, bolts, and washers go on and these six are ready to be turned down on the ol’ dremel like this:



I have two months to get this done……could be tight.

Mike

[Ron40]

Mike,
A real good start. I have driven and towed aircraft with this
Clark tug when I was in the Navy. They were painted yellow
which was standard for ground equipment. Brings back memories....Ron

[B-Manic]

This should be very interesting. Thanks for the tip on using the centres. It seems so obvious and yet . . .

[cotlet]

Thread subscribed ...
Learning mode ... ON ...
Awaiting updates ...

:D

[Don Boose]

An excellent choice for the next project, Mike. I thoroughly enjoy peeking over your shoulder as you conduct research, systematically lay out the project, and begin.

The wheel construction brings together several techniques that you have mentioned elsewhere and confirms the idea that I have long held (but never acted on) that thin-diameter bolts are useful as mandrels for aligning and turning wheels.

I also like the collaboration with Bruce Clemens, himself another outstanding paper model builder and major contributor to the craft.

I give you joy of your new project. Please to continue.

Don

[Tapcho]

Best tip for so far - print your data in dinder to keep it handy while you build. I've ben running back and forth between my computing space and my building corner. Thanks!
Sometimes good resolutions seem embarressingly obvious when you see them - like hardening the disk centers with CA before drilling the holes bigger. Why didn't I think that before? Thanks again. ;-)

Tappi

[Bomarc]

Originally Posted by Don Boose

The wheel construction brings together several techniques that you have mentioned elsewhere and confirms the idea that I have long held (but never acted on) that thin-diameter bolts are useful as mandrels for aligning and turning wheels.

Yep. Those in the picture are 1 inch long 4-40 bolts, that come in packs of eight with their respective nuts. I had to buy a pack from Home Despot specially for this task as I had nothing smaller that was long enough to double as a shaft. They should fit a 1/8" Dremel tool collet just fine.

Originally Posted by Tapcho

Sometimes good resolutions seem embarressingly obvious when you see them ......

Ain't it the truth!

Mike

[Bomarc]

....go have a beer?

Turned down the rear wheels tonight, and played around with some tread detail (with mixed results). First the dust factory:



These were basic shapes, so no template was needed. I just used calipers to gage the right diameter. For treads, I want to try to duplicate the knobby tread pattern of the ‘40’s Mill-44. Pretty interesting pattern:



In my work-up last week, I figured out the crazy geometry of the treads and drew up a set of patterns printed out in 1/33rd scale:



I worked out in my head a couple of routes that I could try and take on this, and given the depth of the treads I’m trying to replicate, both methods involve applying the tread to the surface rather than cutting them in (too many dead end intersections in the pattern) . So I cut a pattern out and glued it to some mat board:



Then began the tedium, cutting away the white areas:



Surprisingly, it when fairly fast, about 45 minutes:



That was glued that to the circumference of one of the freshly sanded wheels. The extra material in the foreground was what I didn’t need to cut out and could have shorten the time of the step above (DOH!):



Then added little strips of card around the edge and nipped the excess off:




Coated everything with CA glue to harden and keep everything in place:



Once the CA glue hardened, I chucked it up again in the dremel and smooth it all down. Seemed promising:



It was clear that I flooded the CA too much and had to go back and clean out excess in some of the treads. A coat of paint tells the tale:



Not quite what I was shooting for. The details are soft. Well, the nice thing about applying treads like this is that I can sand it all off for a do-over. That’s why I didn’t feel the need to make any extra wheels.

On to Plan B over the weekend…..

Mike

[Don Boose]

Fascinating stuff!

I await the outcome of Plan B.

Don

[Bomarc]

Ok Let’s try it again.

One of the many issues that came up in last night’s attempt to apply tread was that the cut out tread was thicker than scale. I needed to cut right to the black of the pattern, and I left a lot of white on there. So that didn’t help things. But there were other issues as well so I’m trying something different.

I laminated some 0.05mm white comic book backer to 65lb cover stock to get it to the scale thickness of the treads as I drew them in 1/33rd scale (about .032”). Then I found a punch the size I needed to match the radius of the wheel:



Fits fairly well:



The next step was to cut that piece down to be one half of the interlocking tread chevron (red lines):



Once I had pattern piece, it was time to duplicate it, so you know what that means! I made a tool:





I hardened the edges of the “tool” with CA so it will hold up to cutting against it. I could now punch a series of holes in my laminated stock and make two “treads” for each hole using the tool as a cutting guide:




This I “laced” on my printed pattern:



As I progressed and saw how the pieces would interact, I adjusted the parts to allow some movement in compression, and only glued the parts to the printed paper and not to each other, allowing for further movement. The completed “mat of treads”:



Cut it out and wrapped it around a wheel:



See where I’m going with this? I theorize at this point, I can CA glue it all down and make it rigid, then spin it on the dremel to sand off the paper backing, then fill in the intermediate treads (cut the same as above), and do a final shaping.

This first attempt was just a first “proof of concept” run, so I won’t be attaching it. I just wanted to see if all the geometries would work. I’ve modified my tool so that the treads are cut to the correct depth (they’re a little tall for this go-around), which, again in theory, will give me the right number of treads as well. I need 12, and right now I have 13.5. We’ll see….

Mike