M4 High Speed Tractor

First written: December 22nd, 2009 | Updated: July 30th, 2010

Pulling power

The first time I saw a model of this vehicle on a magazine the first thing I looked for was the manufacturer. It was a resin kit from Masters Productions and had a very respectable price tag. I forgot about it. With that kind of money I could buy 3 or 4 decent kits I wanted badly.

But a few months after I first saw the model Hobby Boss announced, not one, but two versions of this tractor!!

Of course I found it on my usual Internet shopping spot but other things got in the way and I just didn't order it. I found it for a very good price on a hobby shop that "used" to exist on a shopping mall close to home.

Of course I bought it.

The vehicle

M4 was produced from 1942 by Allis-Chalmers of Milwaukee. The vehicle was in service up to 1960 in the U.S. Army service.

Between 1943 and 1946 about 5,500 vehicles were produced. The tractor was designed to pull 90-mm anti-aircraft guns, 155-mm howitzers of type "Long Tom" and 240-mm howitzers. In the course of the Mutual Defense Assistance Program after WWII the M4 was exported to Japan, Brazil, Germany, Yugoslavia and Pakistan.

It was used by the Bundeswehr in the field artillery battalions until 1960 towing the howitzers M114 and M115 and the M59 field gun.

The M4 High Speed Tractor was also in the civilian sector, as Airport crash tender.

It was used also in the Netherlands until the 1980 as a fire fighting and rescue vehicle. For this role former Army tractors were converted after withdrawal from military service circa 1960.

Specifications

The M4 High Speed Tractor was based on the chassis of the M3 Stuart. It was powered by a six-cylinder inline petrol engine (145GZ or F817G) manufactured by Waukesha. It had a power rating of 210 hp at 2100 rpm. The engine had a whopping 13,400 cc.

The maximum towing capacity of the M4 came in at 14 tons. The tractor could cope with 30° slopes . Transported up to 11 people, the operating crew of the towed gun, in the interior space. The engine was located in the middle of the vehicle and the ammunition stored in the back. Some versions of the M4 had a crane at the rear of the vehicle for lifting the heavy artillery projectiles. The crane could lift up to 10 tons.

The kit

It looks really good on first inspection. The surface detail is crisp and as far as I could check against reference photos it seems very accurate. It includes photo etch for those details that would profit more from this material like the engine and front grills, a length of chain for the ammo rear door and crane and a piece of string for reproducing the cable on the winch.

The kit reproduces a M4 with a Class B ammunition container with the louvered side vents. It's kind of easy to do a version without the vents as this ammo container was also frequently used on M4's.

 

A pair of M4 HST ready for shipment in 1943. They have a class B ammo container (no louvered vents) and T49 Steel Cleat tracks

A M4A1 with the wider suspension and the T49 Steel Cleat tracks with duckbills. Note the wider fenders on this version. Picture from Ampersand's Publishing, A Visual history of the US Army Tracked Artillery Prime Movers book

A very decent set of decals for what appears to be a Korean War version (too bad it's not WWII) and vinyl tracks. It also includes masks for protecting the windows while painting and this is something that is not common to find and some brands even make aftermarket items for this use. A very nice addition to the kit.

The tracks included are T48's although it was common to find this tractor using T49 Steel Three Bar Cleat tracks. Another common configuration included tracks with duckbills and the M4A1 version had the suspension and sprockets farther from the hull to accommodate duckbills on the inside and outside of the tracks. This version had the fenders a little wider than the normal version, so if you want to do a M4A1 grab some plasticard and prepare to make new fenders.

The vinyl tracks were the only thing I was not very amused about, but the price for a set of T48 link tracks from AFV Club is very reasonable and some additional PE from Eduard does not break the bank either.

The worst part was when I found a detailing resin set from Masters Productions and a canvas for the ammo container. Yeah, I know I'm lazy and I could do a decent tarp for it, but when I'm on a shopping spree for After Market parts I have no limits.

After all, the final price tag if close to a what we pay for a bare bones Dragon kit these days so I try to comfort myself with that thought.

Another thing that I got was the Ampersand Publications book about the HST's that is one of the best sources to find photographic information about this vehicle.

Everything is set for the start of the build. As usual you can follow it here. Just stay tuned.

Building

I started by the lower chassis and suspension and found that some minor touches are needed here and there. The model is not completely devoid of flash but it's that type that can be removed very easily with an Xacto. Another thing is the fit between parts. The edges are not what we can call sharp, so sanding and filing is needed. But with care the result is really good.

The suspension is very easy to do but take care when placing the wheels on the bogies because one of the faces has much sharper rim lines and this helps immensely when painting the tires.

There are however some points that need to be addressed with some care

1. Suspension rear wheels

The big rear wheel needs two outside rings to be glued to reproduce the step that the original has. Grab some putty because you're gonna need it. After gluing the rings I had to apply a liberal amount of putty to hide the rings seam. But then I had another little problem – removing the excess putty. Faithful Dremel to the rescue. The hole on the wheels is exactly 1/8" diameter so I inserted a drill and hold the wheel in it with two rubber grommets. I had an improvised lathe. Armed with this tool, removing the excess putty was a breeze.

2. Sprockets

After these little tribulations I decided to make a track run. I bought the T48 AFV Club tracks and found that they didn't go very well with the sprockets. On the spares box I had two M4 Tasca sprockets but they were not exactly like they should. The ring was OK but the center hub lacks a few bolts (4 in between the bigger 8 bolts) and the shape is not exactly correct when compared with the reference pictures.

I don't want to risk being dragged on the mud by the "specialists" so I decided to rework the kit sprockets in order to make the tracks fit. Again with the help of a Dremel I made the characteristic teeth shape a little more pronounced. When I compared the Tasca sprocket with the Hobby Boss one the major difference was precisely on the teeth. The fit was perfect on the Tasca but not on the HB one. It were the teeth – after the rework the track fits perfectly.

3. Ejector marks

The lower tub has some ejector marks that can be visible on the finished model. The wall that separates crew from driver has a few marks also. Removing them is no big deal as they appear on flat surfaces that can be sanded very easily.

Removing them is just a matter of using some putty and sand flat.

Other than that the cabin is a very straight forward build. In the picture you can see the Masters Productions parts. The cabin roof MG ring and the seats that, like the original, have four individual places in the back and 3 in the front with seat belts and all. Much better than the plain plastic ones included on the kit.

Normally I wouldn't care about this but on a open kit these details need attention.

4. Front Fender

One point of note is the front fender. If mounted as it is it'll prevent the cabin to sit right. There will be a visible gap when the cabin is in place.
There are two places to sand to avoid this: One is the lower belly piece that "supports" the fender and the other is the fender itself. You have to sand the fender a little bit on the top face to make it a little narrower. That and a bit of sanding on the lower belly piece where the fender sits will be enough for the cabin to sit flush with the lower hull and fender leaving no gap when glued.

The tracks

Geez, these M4 tracks are a pain to build. If the links don't fit tight they will just fall while you assemble it. I don't know how many times I was on my knees looking for lost links on the floor. I decided that enough was enough and started to apply a little Tamiya thin glue in each link. Before drying I moved the track in order to keep it able to move instead of having a stiff and long track that would be of no use.

These tracks look a lot like Modelkasten due to their brown color. The main difference is the price and in favor of AFV Club since they are considerably cheaper.

I prefer to stay away from MK tracks, especially German vehicle tracks due to their assembly method that relies on tiny pins that break easily and are not very tolerant to turpentine or even white spirit, two things that we may need to use during the weathering phases. I was pissed big time with my Hetzer experience and for me that was a big factor for not buying MK tracks anymore as long as an alternative exists.

Building progresses

 

After a long period I decided that I had to finish this kit. I started and finished the engine and pretty much the engine bay area.

There are a few omissions on the instructions but nothing dramatic. I found this by looking closely at the pictures and found a couple of pieces that were not in the building steps. The engine is a very nice piece but the mold precision is not the best in the world. A lot of sanding was needed to get rid of seams when I realized that very little of the engine would be visible. I gave up and decided it was good enough for the sort of model display I'm planning.

The Eduard PE that you see on the pictures covers only the engine area, especially the radiator grills and a few other details. Eduard makes a couple of sets for this model but I just got the engine set and it proved to be a wise choice.

Accessories

Maker	Item	PN	Used
Masters Production	UPDATE M4 HIGH SPEED	MAS35050	Y
Masters Production	CANVAS FOR M4 HST	MAS35057	Y
AFV Club	T48 track	AFV35038	Y
Eduard	M-4 Tractor engine and mesh	36070	Y

The tarp on the ammo compartment is from Masters Productions and it did have quite a few repairs with Miliput. It had many flaws that would compromise the final look. At some point I almost decided to throw it away (it didn't sit right), but in the end perseverance took over and I decided at least to try.

Also from them are a few items you can already see on the pictures. The seats, a much better rendition of the real one, with safety belts (oh yes they had belts then), the MG ring with the correct welding marks and a somewhat revised shape and a set of pioneer tools.

Masters made the only MA HST I knew about and many times I has the mouse hovering the buy button. The price however deterred me from that. It was really high. Some of the parts were turned into update sets and as far as I know are the only ones for this model. However, Masters does not have a site and I bought them through Blast Models my faithful hobby supplier.

Pictures

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