Russ Bucy presents a full build review of Roden''s Holt 75 tractor, including painting.

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If you have comments or questions please post them here.

Thanks!

Exciting and impressive model! Very useful assembly account. Thanks, Russ, you have really sold this kit! I did not notice in the howitzer review - have you photographed them together? This clunky looking equipment, for me, has an impressive visual quality that newer modern "sleeker" artillery and prime movers lack.

Thanks Fred. It really wasn't my intention to "sell" the kit, as it was to create a nice (and unusual) display of WWI Artillery with the kit. However, like any kit, it's received some bad press, and I set about to see if it could be made into something nice-- and found it can with a little modeling effort. There are some photos of the combined "train" at the bottom of the article. You're right about the visual quality of the two assembled kits. But the length also makes it hard to photograph--put together, it's nearly two feet long. Because Rick and I live about 50 miles apart, we weren't able to get photos of the Howitzer on the platform and the Howitzer "in train" together before the article went to print.
VR, Russ

Thanks again for the build review; such kits and what they represent is a wonderful change of pace from all things WW2. Almost seems agricultural and that you'd expect to see it at a thresherman's reunion or state fair somewhere amazing the kids, scaring the dogs and making the elderly pause and reminisce...

Thanks for the review, it will be very useful when I get around to building mine....
/ Robin

Robin, Frank,
Thank you for your comments. And thanks to Carlos for getting it published. I had a lot of fun building the kit (both kits really). You’ll find there are many places you can “improve” or add detail to the kit—both kits really— especially in the case of the firing platform for the gun— Rick Taylor has done a great job adding detail to it— check out the related linked article too. I had a great time just building the tractor “OOB” (with a little “elbow grease” added of course). Roden has done us all a great service by releasing this kit and the Howitzer. As Frank alluded to, it was refreshing to build something “different”. And, when coupled with the 8” Howitzer, it makes a nice display.
VR, Russ

For those of you interested, Roden has posted an image of the box art for their new combination kit combining the Holt tractor with the 8" BL Howitzer. Go to their "News" section for a view:
http://www.roden.eu/HTML/framemodels1.htm
VR, Russ

Russ - a beautiful model and an equally beautiful set of photographs - thank you.

Building my Holt as we speak. Love the highly detailed engine though I would wish for more locator pins (especially in the area of the engine governor.) I paged ahead in the instructions - went straight to the engine as the start of the build!

The very obvious sink mark right down the center of the roof was a real disappointment. With all the separate framing to be added underneath that roof it would have been an easy task to make that lengthwise center support a separate piece and thereby avoid the EXTREMELY visible sink mark on top.

Trying now to fill that sink in - wish me luck.

Question: At the rear of the engine there is a vertical rack of pipes. What purpose do these serve? I am guessing these form a crude engine oil cooler???

If so should these pipes be painted a dull brass or bronze color?

Michael, I couldn’t find any good photos of those tubes on the ‘net. But I also took them to be a type of oil cooler, so I suppose they could be painted a dull bronze or brass color. The engine is quite detailed, and if you had some good photos, you could figure out the wiring and solenoid pattern for the right side. You can’t see it in the photos, but I did add a couple of wires for the coil at the front of the engine which lead over to the generator. There are also “pins” on the right side of the cylinders which I took to be spark plugs, which would connect to a crude distributor (rectangular box with the belt at engine the right rear). But I couldn’t find any good photos of this area.

Roden gives you everything you need to build a super detailed engine with a little work. As for the roof, I was initially going to replace mine, but decided to “take up the challenge” of filling those little holes. It looks harder than it is— follow my method of thinning out some Tamiya putty, go slowly, and in no time those little divots will vanish— it might have taken me a total of an hour to get the roof in shape (not including drying time for the putty). But you’re right, with a little better kit engineering, Roden could have saved us all that step. Good luck with your build, I found it quite enjoyable, despite the warts. Along with the 8” BL Howitzer, it makes a very impressive model. In sure a talented scratch-builder like yourself will have no problem. I was surprised when my Holt and 8” Howitzer earned 1st Place in “Towed Artillery” at our recent Seattle Regional IPMS show—considering the build was mostly OOB. If you’re building the 8”, see Rick Taylor’s build article too— and ModelCellar offers a nice wheel correction set for the Howitzer.
VR, Russ

Russ, thanks for sharing the info and thanks for the tip regarding ModelCellar and those wheels. I have not purchased the canon as yet but my LHS had both items in stock and I did feel I was sort of "breaking up a matched set" there.

As to those dimples in the roof casting - I chose to take the following route and the results so far are looking quite good:

First; a small drop of model glue in the low point of each roof depression. (The dimples are only in the valleys of each roof corrugation. No dimples on the peaks.)

Allow glue to dry and harden for two days.

Using a small round tapered needle file, sand cross-wise, in each depression of the corrugated roof. As a final touch use a moderately fine grit sandpaper, working a single sheet of the sandpaper under you fingers and again working cross-wise to remove any remaining glue that might be left clinging to the peaks of the corrugations.

Finally, several liberal coats of Tamiya gray primer to smooth everything out all the more.

(Photo to follow)

One more thing - and this is in regards, Russ, to your comment about the lack of any texture to the back side of the radiator:

First of all I agree completely!*!*!*!*!

Royal Models makes a brass etched sheet with what is said to be a radiator texture etched into it. I had the same complaint regarding the radiator on the Mirror Models D7 Caterpillar Tractor and here is how that one turned out.



I plan to give the same treatment to the radiator on the Holt!

Michael,
You may have found an even easier way to fix those “roof divots”! You won’t be able to see much (if any) of the backside of the radiator because of the shape of the rear housing, so I’d save your radiator material to use in the front. In fact, study some close ups of the radiator if you can, and you’ll see the “crinkled” radiator tubing behind the mesh screen on the front of the real thing— that’s where I’d use the material you have— covered with appropriate sized K&S screen (like I used), and it would look fantastic! Roden only provides a molding of the screen, which is good, but it doesn’t have any “depth” to show the radiator coils beneath. By the way, there is an on line reference for the 44th and 58th US Coast Artillery Regiments that used the Holt 75 in WWI (I think it’s linked to the Wiki page on the tractor or the Howitzer— I forget which now). These tractors were only in US Coast Artillery service for a few months before the war ended, so I think I’ve overdone the weathering on mine a bit. I’m looking forward to your take on this kit. Keep it coming!
VR, Russ

Here is my take on fixing the roof dimples as described above.
it is not totally perfect but I am very happy with the results.



Paint Schedule:
- 4-6 coats of Tamiya gray primer. Lite sanding in between each coat. - Rattle Can
- 1 coat Model Master early OD (#1911) - Rattle Can.
- 1 coat - Citadel transparent shader. Color: Agrax Earthshade - Applied with wide brush.
- 4 lite coats of Tamiya Matte Clear (#TS-80) applied at a distance so paint is very dry (and extremely flat) when it hits the model - Rattle Can.
- Pastel chalk - irrigular yellow/tan for dust shading all over - Black pastel around exhaust stack opening - Applied with wide brush.

Russ can you please give us a spec on the K&S screening you used for the radiator front?

You have me thinking to at least put that over the existing radiator molding to add additional visual depth in that very easy to see area.

I know this would have made the model much more complex, (and expensive) but . . . .

I wish Roden had chosen to model the earlier Holt with the open exposed differential at the rear.


O gauge 1/48th scale model shown above..

It occurs to me that if one were to purchase a second copy of this kit the front spoked wheel and some of the track gears would work nicely to build a respectable version of the differential. The only thing that fails me is how to manufacture the large beveled gear teeth needed for the two largest gears and the smaller drive gear???

Michael,
The K&S Photo Etch Brass mesh I used is 1/32 square-fine, Stock number 02701. However, I believe K&S has discontinued their excellent line of Photo Etch products. You can still occasionally find them around. KA makes a similar nickel-brass etch product, which would probably work too. Not sure if Eduard carries anything similar.

The "friction drive" transfer (so called because it uses a special camel-hide covered brake to slow one or the other side of this split drive gear--I believe that's what's depicted just inside the rim of the right gear, behind the driver's seat in the model). The gear itself would be a very interesting addition, and could be done with some creative scratch-building-- but I think using the wheels from the limber or firing platform of the BL Howitzer might be a better solution than the front roller. I think you're just the guy to do it after seeing your Mack NO. However most of the in-service photos I've seen of these artillery tractors have the covers in place-- probably for safety reasons. But it would be great to see one in a maintenance scene. Something else I've noted in photos is the addition of additional storage boxes to either side of the friction drive housing. Those would also be great additions, as well as side weather curtains hanging from the roof supports. The BL Howitzer comes with the Limber, but it also comes with the two wheel carriage for the firing platform (since the firing platform wasn't always towed, you could scavenge this wheels for such a conversion), or even better, build the Howitzer on the platform, with the tractor behind, undergoing "maintenance"-- just an idea😁 This kit would lend itself to all kinds of possibilities... looking forward to seeing what you can do with it. I suspect you'll soon be looking for the Howitzer though-- the "train" is really impressive-- will make a nice contrast with your Mack NO and the WWII 8" Howitzer. Two Wars, two different approaches to towed artillery, separated by 25 years. Add an M54 with a PIg and you've got 50 years of Artillery pulling power!
VR, Russ

Russ

Thanks for the specs, and yes it was a sad day when K&S decided to drop their line of fine mesh etched screens. It is just possible they got out of the game just before the market chose to ramp up on the art of scratch building.

Also thanks for the "mentions" as to my past works - much appreciated.

p.s. I think I would like to do a dio with the gun in firing position on the firing table with the tractor and limber strewn piecemeal around the gun.

Here is something everyone might be interested in: An image from my Grandfather's "Automotive Engineering" six volume encyclopedia dated 1920.

Sorry Russ that I was not onboard to provide this sooner.


Post WWI engine layout shown here is just slightly different from our WWII military tractor but still very close. The coil is mounted here at the rear of the engine rather than at front, the lubricator and associated lines are clearly visible and the magneto appears to be made up of four separate coils rather than one big covered mass as on the model. (Unfortunately no similar photo was available for the opposite side of the motor.)

Michael,
Thanks! Yes, that photo would have been very useful. Although my original intent was to build the tractor for a review as close to OOB as possible, so this photo will be very useful on the next one. I'm still searching for a photo of the wiring as it comes out of the distributor and goes to the tube carrying the plug wires, but haven't found one yet. If you run across one it would be interesting to see. It's an interesting relationship between the fan belt pulleys, magneto, distributor, and flywheel and the associated pulleys-- complicated yet primitive at the same time. Almost "steam-punk" in appearance! By the way, an acquaintance of mine who scratchbuilds Coast Artillery models for the Coast Artillery museum here in Port Townsend Washington has a photo of a Holt towing a 155mm Howitzer in France. That tractor has a "flapper valve" atop the stack, which makes sense too-- I imagine these tractors had that as standard equipment-- he's also built this kit (along with a scratch built 155mm) and added the valve.
VR, Russ

Michael-- sent you a PM. In the meantime, here's a brochure on the care of the Holt 75, with some interesting information--beware, this pdf is 104 pages long-- take your time, or you may lock up your computer waiting to load!
https://ccmodels.com/wp-content/uploads/2014/06/CCM_Brochure_for_Holt75_Howitzer.pdf
VR, Russ

This set of 1920's books I have attempts to be a general primer so they are carful to show no favoritism in their selection of photos to any one vehicle manufacture. Consequently there is no overall photo of the Holt and no focused coverage of a particular brand. If they talk of engines they may use a Holt photo, of governors an Allis-Chalmers, etc., etc.

However in the clutch section this photo was displayed:



p.s. Russ, I will definitely be adding the flapper valve to the exhaust stack! Thanks

A second image of the steering clutch/differential assembly provided by Russ:

Michael, I sent you the Howitzer manual as promised. It's missing a few pages from th original, but you can get the idea pretty well.
VR, Russ