At the first sight of this H75 engine, i think some of you have already recognized that it's a miniature Caterpillar Holt 75 engine.The gasoline Holt 75 Caterpillar was the best-selling of the Holt "tractors" with a chassis running on crawler tracks from 1910s to 1920s for agricultural and military purposes. It earned a high reputation as a quality farming tractor among the farmers and was widely used in WWI by hauling artillery and ammunition in the United States, in England and France, and in some other countries.

also see review here: Alpha Mods Disassemble and Build a Mini Tractor Holt H74 ICE | Stirlingkit

Benjamin Holt (1849-1920, president of The Holt Manufacturing Company of Stockton, is famous for inventing the track-type tractor in 1890 , (people call it “Caterpillar.”), which plays a significant role in the American Society. At that time, it was regarded as one of the most efficient machine as it helps farmers working and more productive longer and cheaper than horses ever could. 

Back in World War I, the first large machine that began to be loved and feared by soldiers on the battlefield was not a tank, but the Holt tractor invented by Benjamin Holt. His invention of the Caterpillar track became a new land transport system, which could easily did agricultural works and had good military potential thanks to its enormous torque and traction.

Now let's get to know the amazing tractor prototype!

What's HOLT 75 Tractor?

   Origin：

As with so many early 20th-century war machines, the Holt 75 began it’s career in civilian service as an agricultural tractor.  In 1904, Benjamin Holt developed the first practical track-type tractor to enable farmers to plow through loose California soil.The Holt tractors were a range of continuous track haulers built by the Holt Manufacturing Company from California (U.S.), which was named after Benjamin Holt. The most popular of all Holt tiller-wheel tractions was the 75, and it turned out to be the most famous too.

Supported by an endless track of wood and steel, Holt called his invention a “Caterpillar” and the name stuck. To the soldiers, these vehicles were popularly known as "Cats".

but came into its’ own while being utilized during the construction of the Los Angeles aqueduct system beginning in 1909.

It's said that almost 2,000 tractors are used in British, French and American forces in World War I, because satisfied the needs to carry the heavy artillery pieces to haul around the Queens of the Battlefield under the uneven terrain.

Advantages：

1. Strong Power Farming Tool

The Holt 75 engine can produce over 70 hp, this power combined with its ability to negotiate difficult ground conditions, meant it quickly replaced the horse and ox as the primary sources of motive power.

2. War Helper

During the war in 1910s, compared to the horses, Holt 75 met the military needs to haul heavy weapons, heavy artillery on the battlefield. so it was widely used at that time.

Disadvantages：

1. Poor Cross-Country Ability

The fact that this vehicle had tracks, and therefore had a limited off-the-road capability was a lesser consideration than its availability.

2. Poor Steering Ability

Here are two examples of Holt Agriculture Caterpillar Tractors. They came in two models the 75 h.p. model, and the 120 h.p. model above. The 120 h.p. version has a steering wheel in the front to aid in turning and usually had an covering over the tractor while the 75 h.p. version just had the two tracks for steering.

Usage：

Most for military use

Holt 75 were widely used by the British, French, and American armies in World War I for hauling heavy artillery.

1. 【Artillery Delievery Vehicle 】

The Holts were sent to France where they became a major artillery vehicle for the next four years, mainly engaged in hauling medium guns.

2. 【Artillery Tractor】

One Holt 75-h.p. vehicle was purchased and tested (in Tunisia) by the French Army for possible adoption as an artillery tractor. But France later produced vehicles inspired by the Holt and did not herself use this type in quantity.

3. 【Armoured Versions Use As Tank】

The French Schneider CA1

 and Saint-Chamond 

and German A7V  tanks were based on Holt tractors.

Two armoured versions of the Holt were produced in America for possible use as tanks (though they were not adopted), and Holt components formed the basis of the only German tank to see service, the A7V and provided the inspiration for the French tanks which appeared in 1916

For Farming Use

After the war, Holt continued to build the 75 as sales remianed strong for a while. Tha 75 tractors was found to be as tough and reliable in farming as is was in long-distance heavy hauling or road construction.

What's HOLT 75 Tractor Engine?

Introductory：

Advantages：

1. The large，heavy steam boilers used to power the earlier Holt tractors has been replaced by gasoline engine.A gasoline engine considerably reduced the overall size and weight of a tractor, produced more power per pound of weight, and reduced the tractor's cost, making it more cost-effective and affordable.

2. Having a better power-to-weight ratio, a gasoline-engined tractor required fewer men to operate.

3. 75 hp tractor with drawbar horsepower in the neighborhood of 40-45 hp. With that horsepower, it’ll pull a 12-bottom plow.

Disadvantages：

1. The way the crankcase had to be machined for the main bearings.

It required some reasonably accurate filing, mounting the main bearings then line boring them. This meant that the main bearings once mounted had no real way of relocating should they need to be removed or replaced.

2. With the poor quality of some of the castings.

Why did Holt  75 fail now?

The "Holt-75" was mass-produced in 1913 with 83 hp and a top speed of 24 km/h. It was built not only in the USA but also in the UK by Ruston Hornsby and ceased production in 1924.

Because of  the "Holt-120" was built in 1915, with stronger horsepower up to 120 hp and steady weighing 8.2 tons, which replaced 75 for its poor steering ability and the poor cross-country ability that are not capable for farming use since it does't needed in war.

where to buy H75 engine mode? click

 Source:

http://ricklawler-propaganda.com/propaganda/modeling-projects/pulling-power-holt-75-tractor/

https://www.homemodelenginemachinist.com/threads/holt-tractor-engine.31265/

https://ccmodels.com/shop/holt-caterpillar-75-track-type-tractor/

https://fineart.ha.com/itm/paintings/scale-model-four-cylinder-holt-tractor-engine22-1-2-x-20-1-2-x-13-1-2-inches-572-x-521-x-343-cm-expertly-built-and-f/a/5181-87303.s
http://www.landships.info/landships/softskin_articles/Holt_15_ton.html

https://en.wikipedia.org/wiki/Richard_Hornsby_%26_Sons

https://www.farmcollector.com/farm-shows-all/bird-city-antique-tractor-and-engine-showground-zm0z21mayzbut/

https://www.wikiwand.com/en/Holt_tractor

https://www.gasenginemagazine.com/gas-engines/the-model-halt-75/

https://soundingsmag.net/2019/06/26/caterpillar-tractors-roots-in-delta-peat-soil/

https://soundingsmag.net/2019/06/26/caterpillar-tractors-roots-in-delta-peat-soil/