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Built Review
135
Holt 75 Tractor
Roden Holt 75 Artillery Tractor
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by: Russ [ KEVLAR06 ]

Introduction

When I saw Rick Taylor's In-Box Review of the Roden 8" BL Howitzer in December 2018, it finally gave me an excuse to build a Roden Holt 75 Artillery Tractor along with the Howitzer. The US 44th and 58th Artillery Regiments used the 8” inch Howitzer and Holt tractors in France during the closing months of WWI. These kits complement each other and make a nice display of an important WWI artillery piece and its prime mover. Rick and I are both retired Army Officers, we live a short distance from each other, and we are in the same modeling group. We are both interested in the history of US Field Artillery. So we decided to work together on build articles of these two complementary kits. Rick has done an excellent build review of the 8" Howitzer on its firing platform. You can find the link here
The kit

This is the first “injection molded” offering of the Holt 75 in 1/35 scale. Resicast has a very detailed resin/photo-etch Holt 75, but it’s almost five times the cost of this Roden offering. Kevin Brandt did an extensive “In-box” review of the Roden Holt 75 here

The kit is molded in Roden’s typical soft gray styrene with some overly large sprue gates in a few places. As far as I can tell, it appears accurate in outline, but some of the details are a bit heavy, and there is some flash, especially on the individual track links. Some parts are finely cast with precise detailing while others are a bit coarse. Most large “round” parts in the kit come with significant mold seams, and there are a few mold alignment related issues. There is not a lot of on-line information on these “agricultural tractors” to be found, so I can’t comment on accuracy, but outwardly it looks the part. There is an engine, but no drive train or the unique “friction drive” used in the final drives of these vehicles, however, the friction drive and its linkages were largely hidden under covers on the real thing. The kit could be a great start for "super-detailing” if desired, and there are many possibilities for adding storage boxes, canvas screens, ignition wiring or other details. Roden offerings are like short-run kits, so don’t expect to find “Tamiya fit” in this kit. Most experienced modelers won’t have too much trouble with this kit. Overall, Roden has done a good job of illustrating the build steps, but the diagrams require very careful study for proper assembly and parts placement, and some additional photographic references will help. I deviated from the kit instructions in a few places to facilitate assembly and painting. My build is primarily an “Out-Of-the-Box” build, the only additions being some chain, a scratch-built headlight, and a patch of “screen” for the radiator, none of which are necessary for an impressive model.
The roof

The first notable problem is a line of "sink marks" down the center line of the corrugated roof. So my first departure from the instructions was to start with step 25, building the roof, as a primary sub-assembly. I mixed a thin solution of Tamiya thin cement and Tamiya Gray Putty in a ratio
of 1:3, and using the glue applicator brush tip from the bottle, I carefully applied small drops of thinned putty into each “divot”. After a couple hours, a folded piece of 400 grit sandpaper was passed between each corrugation, sanding out the spots of putty. I also hit the edges the roof at each corrugation to thin them out. I could have replaced the roof, but when the "divots" are filled, it looked fine and was not difficult to do. I assembled the roof and its supports per step 25, but noticed the vertical uprights have rectangular projections in various locations. Don’t file them away, they are supposed to be there for attachment points for the angled braces 2D, 3D, and 4D, and for the attachment points to the tractor frame. Pay close attention to the attachment of these parts in the instructions as it’s easy to get them backwards.
Suspension and tracks

Returning to the sequence in the Instructions, I built the suspension and friction drive cover (the round “drum” in Step 2). The instructions can be a bit confusing- be sure to line up the parts of the friction drive cover with the correct indentations in part 17A and 16A, as these parts will need to fit the frame sides later in Step 12 (it helps to read several steps ahead for this kit). The next step is to assemble the tops of the suspension system and its springs in Step 4. You could replace the springs, but I just cleaned them up-- not much of these springs will be seen when the tractor is complete. Some photos seem to show the top of the tracks sitting a little lower under loads than Roden modeled it. You could shorten the springs and modify part 9B, but I didn't bother with this, and the completed model looks fine. In Step 6, Roden’s track links mate together, but each track pad has two injector pin marks and some flash in the track connector area that must be removed. This requires some easy (but repetitive) clean up with a sanding stick and a chisel blade, but save the track pin "nubs", or the track won't fit together correctly. It took about an hour to get all 56 track links in shape—but you only need 54 of them-- 27 on a side.
Front “steering wheel"

The front “steering wheel" and frame are addressed in steps 7-10. The wheel fits together OK, with some detail on the spokes and side frames, but the fit requires a lot of sanding and scraping to get the outside of the wheel rims (parts 7D) to fit snugly into the one piece wheel (part 9F). There is a considerable mold seam which needs removal on the outside of the wheel, but don't sand out the attaching marks on the inside of the wheel, these are supposed to be there according to photos I found on line. The wheel rims, parts 7D, should mate perfectly with the wheel, but mine needed a bit of thinned putty and some sanding to fill a gap around the rims. Step 8 shows the assembly of the wheel into the supporting frame and ring. Those who want to super detail this area could replace the springs in the side frames, but I didn't bother as they will largely be hidden. The wheel axle, side-frames, and circular wheel frame in Step 8 are a bit fiddly to get together. There is some clean up required on the inside and outside of parts 10F and 11F, as there is some flash and mold misalignments. To ease assembly of the wheel to the side frames, glue parts 18D to part 11F before attaching the wheel frame. When dry, gently spread parts 18D apart and “snap" the wheel frame into place, leaving the wheel to rotate. This simplifies painting later on.
Frame, return rollers, drivers and idlers

Assembling the frame in step 9 is straightforward, except for the fit of parts 1F and 2F-- the “retaining circle” for the front wheel. On the real tractor, photos show the front of this ring completely smooth, but the kit has a large molded “overhang” at the front where the three grommet "bumpers" are. You'll need to remove this with lots of scraping and sanding to get the parts to look right. I recommend seeking out photos here—the box-top art depicts it correctly. I built the frame first, and sanded the assembled parts 1F & 2F to fit. The inside of these two parts should be "stepped" to fit the wheel retaining ring (part 11F). I followed steps 10-12 with one exception-- I assembled the winch capstan (parts 12A and 13A) --BUT DON’T GLUE IT IN NOW-- If you do, it will interfere with the fenders and roof supports later.
Engine, flywheel and water tank

The engine and water tank assemblies in steps 13-16 are straightforward, with cleanup and some putty to fill gaps around the water tank. I managed to save all the rivets along the top of the water tank with careful use of a small folded piece of 400 grit sandpaper, sanding sticks and a fine file. I didn't modify the engine much, except to carve out the solid rocker arms molded on top of the cylinder heads (parts 28E). I did this with a small drill bit, followed by a miniature square file. To simulate the valve springs, I ran a razor saw blade around each spring, just to get some definition in the remaining solid part. Lots of detail could be added to the engine, but I wanted to keep this as close as possible to an “OOB” build. I scraped and sanded the large flywheel (Part 3F) to get rid of a seam-- pay close attention to the instructions in Step 14, as the large and the small flywheel (Part 3F and 17B) go together exactly as Roden has it depicted, with the hollow side of the small wheel facing the engine. I assembled mine backwards because I thought the "plug" on part 17B (small flywheel) should go into the hole in part 3F (large flywheel). Turns out, I was wrong, and the "plug" actually represents the end of the driveshaft – but once it's all assembled, you really can't see any of this. You'll need to clean up and thin out the mold seams on the pulleys and fan belts at the front of the engine, and should also thin out the fan blades.
Fenders

In step 17, Roden chose to mold the fenders “flat”, so they need to be "bent down" on the ends. I’m guessing the reason was to preserve the integrity of the diamond tread pattern over the curve. Once the fenders were bent, I reinforced the seams on the inside with a bead of thick CA in the gap, and a piece of thin styrene glued over it. This keeps the seams from breaking while handling. The angle iron supports (31D) assemble exactly as Roden depicts. You'll be tempted to mount these supports with the angular cut-out on the outside of the fenders. But photos of the real thing show the “square” end on the outside, just like the instructions depict.
Engine support “Box" and tracks

I again deviated from the instructions in step 18 by not gluing the engine to the frame (assembly 16 in the instructions) until final assembly to simplify painting. There’s a tight fit between the engine pulley system and the front of the covered gearbox (Part 6C) on the left side of the engine “box” assembly. I proceeded through steps 19 & 20, with the following exceptions-- I glued the engine support box to the frame, along with the "friction drive cover" (assembly 12 in step 20). I then proceeded to attach the two long runs of assembled tracks to the drive and idler assemblies. This is a little fiddly, and because I left the idlers, drivers and return rollers to be moveable, it was even more difficult to get the tracks on. I recommend gluing them in place before adding the tracks. I ran thin cement around the entire track assembly to fix it in place. The tracks don't have connector pins, so I punched out 54 appropriately sized "pins" from .020 sheet styrene, and glued them in the appropriate places.
Fuel tank, Exhaust, Radiator & Final details

In step 20, I glued the flywheel cover and fenders together (Assembly 17, part 17C and 15B), but did not attach them to the rest of the frame, preferring to keep them as a sub-assembly for painting. I followed the instruction sequence in steps 21-26. I deviated from the instructions in steps 27 & 28 by leaving off the fuel tank, and gluing the controls, seat and shifters to Assembly 17 (fenders and flywheel cover). The fuel tank needed sanding and a small amount of putty along the seams. Roden engineered the seams away from the rivet patterns, but the rivets have elongated “ridges” which must be sanded smooth. If you do this carefully, you can save the rivets. A faster method would be to replace the rivets with Archer rivet decals. Be careful with the exhaust pipe mounted air filter (part 19E and 21E), as the notch in the top rear faces to the right, while the carburetor air pipe opening on the bottom faces left. I removed about 3mm of plastic on the left side of the rim around the fan opening on the back of the radiator assembly, (part 14B)—as it wouldn’t fit over the fan blades. I added some K&S brass screen material to the radiator front for more “depth”, but this is not really necessary as the kit radiator is nicely defined, including the peaked "HOLT" logo at the front. In step 28, I replaced the steering column with a brass rod, but decided not to attach it until after painting.
Painting and weathering

I don’t use primers much, and this model was no different. Instead, I prefer to mix a little lacquer thinner into my base coat colors. I airbrushed the Engine with a coat of dark grey, obtained by mixing Floquil “Weathered Black” and Testor's Model Master “Dark Sea Gray”. The front wheel was also airbrushed with this mixture. The exhaust stack and carburetor intake is Alclad “Jet Exhaust” over Tamiya Gloss Black. The rest of the tractor was “post shaded” by airbrushing a base coat of Tamiya “Khaki Drab”, followed by a coat of Tamiya “Khaki” on the upper surfaces. This combination produces an olive/khaki color typical of American vehicles in WWI. The tracks were painted Testor's Model Master "Track Brown”, then dry-brushed using silver enamel over the high points, the outer surface and rims of the front wheel, and wherever wear might expose bare metal.

I then gave the entire model a heavy wash of Windsor and Newton “Burnt Umber” oil paint, mixed with Turpenoid Light thinner in a 10:2 ratio. When dry, this mixture leaves a slightly "dusty" sheen to the model. This was followed with a second wash of Abteilung "Dark Brown Wash" on the underside, mixed in a 10:3 ratio with Turpenoid Light. I used the same mixture in a pin wash to pick out details on the upper surfaces of the tractor. After 24 hours, I gave the entire model an overcoat of Testor's Dullcoat, decanted into my airbrush and sprayed at 15 PSI into all the cracks and crevices. This mixture quickly dries any residual oils left from the wash process. I followed this up with copious "chipping" using a fine tipped brush and Vallejo Panzer Aces “Dark Brown”. A few rusty spots (no more than a dot or two) were applied in a few locations, as these tractors were not in Artillery service long enough in 1918 to have built up a lot of rust.

The centerline of the roof was given a coat of Floquil “Old Silver”, followed up with a random coat of Tamiya “Khaki Drab” and Tamiya “Khaki” along the sides of the roof, letting the old silver “undercoat” show through along the centerline to represent “weathered” galvanized steel. Once dry, I applied Vallejo Light Orange and Dark Rust in thin washes over the areas closest to the exhaust stack opening, as heat would have caused it to rust faster.

The engine was given a "Burnt Umber" wash, using Windsor & Newton Oils and Turpenoid Light thinner, followed liberally with a Testor's “Black Oil & Gas Stains” wash. I also used this Testor’s product around the suspension, radiator, towing pintle, and other parts that would have been exposed to quantities of oils and grease during operation.
Final assembly

After the sub-assemblies were painted, I slipped the flywheel cover/fender assembly down over the chassis. It was a tight fit, and there are two control linkages that need to be carefully worked into their corresponding holes in the “friction drive” cover. Passing a sanding stick and the edge of a scalpel blade over the inside edges of this assembly greatly assisted this task. This is also why I didn't add the winch capstan during Step 12, as it interferes with getting the fenders and roof supports on. Once the flywheel cover/fender assembly was glued on, I fitted the engine into the engine frame assembly. The engine “bearers” on the bottom of the engine need some smoothing out to get them to sit without “rocking”. The left side of the fan belt system is a tight fit over the gearbox cover on the left side of the engine support box. Just push the pulley and water pump supply pipe forward a little until they slip down over the box.

There are four sets of indented holes-- two at the front of the engine support box, and two on either side of the friction drive cover at the rear of the tractor. These are locating holes for the roof supports. Once you have the roof glued into position, you can attach the radiator and its support brackets. I added a scratch-built headlight off the left side of the bottom radiator support, a length of chain to retain the towing pin, and a larger tow chain draped over the rear. The 8” BL Howitzer “in trail” was also built in conjunction with this build, and can be found in Rick Taylor’s excellent article on the 8” Howitzer.
Conclusion

The kit is nice in some details and fit, while others are rough. With patience, a sharp scalpel, a few grades of sandpaper and some “elbow grease” it can be built into a nice model. Combined with the Roden BL 8” Howitzer, It makes a very impressive display. And it can be used as an excellent base for super-detailing a “show-stopper”. Modelers with experience in resin or short run kits won't have many problems. I wouldn't recommend it for a beginning modeler. My tractor took about 35 hours to finish. I’m pleased with the way it turned out, and it pairs nicely with the 8” Howitzer kit in representing a WWI “artillery train”. I will “super-detail” the next one though—this one is eventually destined for inclusion in a diorama.
SUMMARY
Highs: Fills a need for a significant WWI prime mover. Individual track links provided. Nice detailing in some areas. Can be completed OOB without aftermarket items. Instruction steps require study but are easy to follow.
Lows: Some flash and mold misalignment issues require correction. Fit is poor in some areas. Roof centerline sink marks. A few parts need extensive sanding, carving or filling. No track pins included.
Verdict: Experienced modelers should be able to complete this kit without issue. The kit lends itself to super-detailing options. Can be paired with Roden's 8" Howitzer to make an impressive model.
Percentage Rating
80%
  Scale: 1:35
  Mfg. ID: 812
  PUBLISHED: May 15, 2019
  NATIONALITY: United States
NETWORK-WIDE AVERAGE RATINGS
  THIS REVIEWER: 80.00%
  MAKER/PUBLISHER: 86.97%

About Russ (Kevlar06)
FROM: WASHINGTON, UNITED STATES

I'm a retired U.S. Army Officer, serving for 30 years on active duty. I've been model building in various genres off and on since 1959, when my Brother-in-Law and Sister gave me a Monogram Jeep and 37mm gun for my birthday that year (which I still have in the original box!). I appreciate and have e...

Copyright ©2019 text by Russ [ KEVLAR06 ]. All rights reserved.



Comments

I too went with reversing the clutch plate on the kit build even before I found the research - just simply because the parts fit better that way and did not when facing the other way. I agree with you Russ it might also be correct to have an open drum behind the flywheel instead of the cone clutch. Personally I think the open drum wheel in the photo below is NOT part of any kind of clutch. I think the engine shown here was used as a stationary industrial engine rather than a vehicle mount. I suspect it was used to drive an overhead belt arrangement rather than a fixed shaft. p.s. Note that in the O scale model photo I posted earlier it shows the cone clutch without the sheet metal protective cover. Photo credit unknown - used here for discussion purposes ONLY
JUN 09, 2019 - 05:04 AM
Interesting video of running Holt 4-cyl. engine. Note open flywheel and brass/bronze oil lubricator. LINK In this case the belt driven accessory is a circulation water pump to cool the engine.
JUN 09, 2019 - 05:41 AM
Michael-- great research photos! Thanks for posting these, they will greatly help anyone building the kit. VR, Russ
JUN 09, 2019 - 06:24 AM
I opened up the clutch inspection plate just to add a little bit more detail. Still have not begun work on the cone clutch itself - looking now for a properly sized tapered cone for that construction. (I am thinking a wheel off a properly sized model railroad freight car might do nicely for the clutch cone - now I only have to decide which scale.)
JUN 11, 2019 - 04:14 AM
Russ, (Kevlar06) any chance you have the manual on the Holt tractor as well ?*?*?*?*?*?*?*? Anybody ????????
JUL 01, 2019 - 11:11 PM
Michael, The closest I've come to a manual for this tractor is the link I gave in a previous post at CCModels.com, which is a maintenance brochure: LINK I've looked all over the 'net for a manual but haven't been able to find one. There's even an antique tractor "museum" of sorts in a town about 40 miles from where I live, but all they had going back that far was a 1930 Fordson manual. The guy that owns the museum told me he'd keep an eye out for one, but so far nothing. In the tractor world, these old "steering wheel Holts" are really considered dinosaurs I guess, and very few still exist due to their complicated operation and maintenance. Let me know if you find one. VR, Russ
JUL 02, 2019 - 04:33 AM
Scanned by Google
JUL 02, 2019 - 11:08 PM
A few progress shots on my Holt: I thought I would add some reinforcement triangles to that very delicate front wheel assembly. If carefully assembled the front wheel can be made to roll as well as to steer. .
JUL 06, 2019 - 11:00 AM
Whats the general opinion on my using a diamond pattern screening over the radiator front? It will look really good if painted green in contrast to the black radiator! I happen to have the diamond screening and it would certainly show up more but I admit from the outset - it is not correct.
JUL 06, 2019 - 12:40 PM
   

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