YAG-10 (1932)
Heavy 6x4 Truck
The YAG-10 is a relatively confidental (given the mass of GAZ and ZIS light trucks) 6x4 heavy truck designed by the Yaroslav Motor Plant, with a payload between 6 and 8 tons. Only 333 were manufactured between 1932 and 1940. It was powered by a Hercules-YXC engine, with a 4-speed Brown-Lipe-554 manual gearbox and a the rear suspension was based on British Moreland WD Trucks. It had a top speed limited to 42 km/h with a fuel consumption of 60 liters per 100 km and production was terminated in 1940. However, it was declined into the first dedicated truck-based SPAA of the Soviet Army, the 76mm 3-K Model 1931 AA gun (63 converted).
Development
A new three-axle truck with a load capacity of 8 tons was developed originally from the two-axle model Ya-5. Development started on November 7, 1931, the Yaroslavl Automobile Plant completed the construction of the first prototype of the six-wheeled YaG-10 vehicle. The vehicle, unusual at that time, almost immediately left for Moscow, where it was transferred to NATI for testing. As noted in the report, the YaG-10 was a serial Ya-5 truck on a six-wheel drive, increasing its tonnage from 5 to 8 tons, up to 5 tons off-road. The main changes were listed as follows:
1. Frame reinforced by installing an additional beam.
2. A body was raised for a better ground clearance.
3. New spring suspension Moreland adapted to the chassis.
4. Moreland cardan shafts adapted.
5. Alterations were made to transfer extra power to the middle axle and to the rear axle.
6. Braking system redesigned and strenghtened.
7. Coil cylinder installed on each wheel of the rear axle.
The Moreland rear bogie was copied fully and parts were borrowed. Confirmed by the chief designer of the Yaroslavl Automobile Plant A.S. Litvinov attached to the test report that to speed up production, parts imported from Moreland were the cardan shafts, rear bogie bracket and spring ball joints. But due to the lack of time allocated for the creation of the new three driving axle vehicle, designers took the easier path and used the entire imported design. So the YaG-10 was barely a domestic vehicle from its Hercules engine and larglely a basic Ya-5, slightly modernized. It represented still a significant step forward in 1931. At Moscow production of the antediluvian F-15 was coming to an end, and the current trucks like the AMO-6 were still assembled from American components, Ford notably at Gudok Oktyabrya plant, while the Nizhny Novgorod truck still did not entered service.
The three-axle AMO-6 and Ford-AAA were prepared, but the first serial three-axle GAZs and ZISs would only come 2.5-3 years later. In Yaroslavl, 114 serial YAG-10s already had been built but the annual output wa slow, the company was fully satisfied to call it a "serial production", as it was in the norm for the early 1930s in the USSR, not in the thousands, but in the hundreds. The suspension of the rear axles of the first "three-axle truck" in USSR, the YAG-10, as well as the later ZIS-6 and GAZ-AAA, was a WD-type design, a type adopted by the British War Ministry for military trucks, and USSR imported and tested models from Leyland, ThornyCroft, FVD and Moreland.
They had springs attached to shoes swinging on tubes running across the vehicle. The axle axle shafts were attached to the ends of the springs through movable shoes, on ball joints. The design was simple and reliable yet still allowing for significant axle distortions on uneven surfaces. The design principle for the Yaroslavl "three-axle truck" was accepted, but some unclear points in the truck creation and surviving information are scanty and sometimes contradictory.
Several experimental designs were built at YaGAZ for NATI (The test center) in 1932-1933. Notably the Ya-7 and Ya-8 had a 4x2 wheel arrangement, load capacity of 5tons basic, but up to 7tons. They were powered by an American Continental-21R engine, 6 cylinders, 6,850 cm3, 100-102 hp at 2,400 rpm mated to a four-speed gearbox. The Ya-7D had a demultiplier for a wider range of traction forces and speeds. The Ya-7 and Ya-8 had a frame stamped from 8 mm thick steel metal differby their wheelbase, 4,250 and 4,750 mm. From there was developed the Ya-9-NATI and Ya-NATI-9D with a 6x4 wheel arrangement, true forerunner of the YaG-10 for their superior load capacity (8,000 kg on paved roads and 5,000 kg off-road). The Ya-9D was manufactured. Overall dimensions different from the YaG-10 at 6,320 mm (6,990 mm), width - 2,550 mm (2,340 mm), height of the cabin - 2,560 mm (2,580 mm). Fron track 1,820 mm, and the rear - 1,945 mm (early YaG-10 - 1,750 and 1,784 mm, respectively). The Ya-9D was powered by a 6-cyl. in-line overhead valve engine "Continental-21R" rated for 7.02 liters and 102 hp with a compression ratio of 4.16.
The Ya-9D differed externally from the YAG-10 by its shorter base and flatbed, and different wheel rims, hubs and half-axle cups. The YAG-10 engine Hercules YXC 3 rated for 7.85 l and 103 hp initially installed on soon failed due to damage to the working axle box of one cylinder, and replaced by as spare Continental engine from a Y-7D. It had a dual ignition frop a magneto and battery, a distributor, dynamo and starter from Delco-Remy. All Ya-NATI models had the same multi-plate dry clutch Brown-Lipe-55 with 7 leading disks, 8 driven, very reliable and smoothly engaged.
The four-speed gearbox was the Brown-Lipe-554 with a 2-speed demultiplier. The double gear reducer of the Ya-9D was replaced by a worm gear with upper worm arrangement, compact and silent, and enabling to pass the cardan shaft to the rear drive axle using only the middle axle worm, imported from Timken. The Ya-9D axles were of the "Banjo" type in forged steel like for the YaG-10, with fully unloaded removable half-axles.
The Ya-9-D braking system was dual with a a central handbrake behind the demultiplier and foot brake acting on the internal drum shoes on all wheels, not like the duplex brakes of the standard Yaroslavl truck. The Ya-9-D used 2-shoe brakes. The servo device of Yaroslavl acted as amplifier. The wheels of the rear bogie could be fitted withremovable overall tracks in winter for extra traction, like most armoured cars of the time of the BA6/10 type used themselves. This simple set of tracks with rubber shoes used a slinked, needed to be stored still, when not in use, but they massively increased cross-country ability. The two Ya-NATI-9D was completed on June 1933, and they were transferred to the Experimental Research center at NATI.
During testing, the Ya-9D overcame snow 30 cm deep, climbed snowy slopes up to 25 degrees. But lateral sliding and loss of control were observed. It was better on sandy soils ambeit with excessive vibrations of the drive axles and oscillations with springs to the point of separating wheels from the ground. Cross-country ability was deemed "sufficient" for low-quality roads, dirt tracks and snow-covered roads. Many flaws and weaknesses in the design were revealed, notably for the one using the Continental engine model R-2, 6.71 hp/t versus 6.36 hp/t for the YaG-10's Hercules, had unreliable auxiliary mechanisms, with leaking water pump seals, leaking valves in the carburetor, imperfect filters, problems with gas and ignition control, starter kickbacking and poor location, poorly insulated wiring causing short-circuits and loose fan hub, as well as imperfect front engine mount.
The magneto drive was simply unusuable, and the demultiplier, while generally serviceable, heated up and generated way too much noise in low gear, and had a poorly located lever which often broke. Both cardan shafts were very difficult to install and adjust. The main gear and hub seals were also unreliable. The foot brake operation was faulty and imposed to install in its place a simple and reliable manual one. The height of the front axle beam was only 75-80 mm, and they were sometimes deformed.
There was aslo the rings wearing out and rollers in the tapered bearings breaking. For the steering, the transverse thrust was weak and replaced with a more solid one. Testers recommended changes to the frame as well and the cabin lacked a windshield wiper, poor accessibility of the gas tank under the driver's seat, in addition to its limited capacity, with a pootly placed filler cap causing fuel spillage in the cabin. The flatbed platform at 3,5 x 2,49 x 600 mm proved too small and spare wheels, vertically was not very convenient. The test run of 10,000 km was to be followed by further testing of the Ya-9D and this started with the installation of a Continental-21R engine and Hercules-YXC-З for comparative tests. The Ya-9D's two-stage demultiplier and worm main gear was considered convenient for a three-axle vehicle and enabled a high gear ratio. The Ya-9D chassos was similar to the Ya-7 and Ya-7D but with additional bracing for extra strength and rigidity.
In 1932-1938, NATI experts continued to wortk on new versions of the three-axle Yaroslavl trucks, notably the Ya-5-NATI with a demultiplier, rear wheel suspension, worm-type final drive and Hercules-YXC-S engine (5 tons load) plus a final drive ratio of 8.75. The Ya-10-NATI and Ya-11-NATI had a Continental-21R engine with a lifting capacity of 8ton, final drive ratio of 9.33. They all differed significantly from the YaG-10, notably externally with new hubs and wheel disks, stamped frames (riveted from standard rolled channels) and worm final drives. The were more advanced than the YAG-10, But the plant lacked the appropriate equipment for manufacturing a worm gear or stamped frames. The YaG-10, meanwhile, less refined, was acceptable for serial production, created and tested.
The YaG-10 tests took place from November 16 to November 27, 1931 in an abbreviated form to save time. On November 16, after inspection and refueling, the prototype started a test run along the Leningradskoye Highway to identify faults (102 km loaded with 4.2 tons). A water leak in the pump seal was fixed, but nothing more and the run resumed on an average speed of 20.2-25.4 kph with a fuel consumption of 42.2-45.9 liters for 100 km. The transmission, especially the rear axles, was noisy when moving due to an inaccurate adjustment of gear engagement. On November 18, a detailed inspection was carried out it was found a "slapping" of the rear left spring and "nicks" on the universal joint crosses working at an angle exceeding the maximum. From November 19, the YAG-10 made a 195-kilometer run on the Yaroslavl track for comparisons with a YaG-10 loaded with 8 tons, another with a three-axle FWD loaded with 5 tons and a three-axle Ford prototype (predecessor of the GAZ-AAA).
The YAG-10 was found to have broken bolts, for fastening the propeller shaft housing to the rear axle, breaking pins of the rear axle hinge as well as loose bevel gear shafts causing much noise, plus poor grease retention in the spring ball joints. After repair, the YAG-10 made a run around Moscow with a 8-ton load. On November 23, same, on dirt roads of the Moscow Oblast. The test was soon joined by a serial Ya-5 loaded with 3.7 tons. Close to Nikolskoye, they had to deal with knee-deep clay mud, and the YAG-10 got stuck three times but got out in 1-4 minutes without outside help, just using branches under the wheels. The FWD 6x6 did not get stuck, the Ford got stuck twice, and needed help. The YaG-10 showed the same average speeds of 10.5-11 kph there, with fuel consumption of 92.5-99.7 liters for 100 km, like the FWD. The YAG-10 tried to overcome also a 26° dirt climb but reoounced due to a broken clutch. On November 25-27, fixes to the rear bogie were determined, tests for stability, speed and throttle response were started.
NATI specialists conclided that the YAG-10 has a significantly higher ground pressure than foreign models, but equal ground clearance. Its maximum tilt was good, at 25°. ut its had an inferior traction compared to the Ya-5, lower speed and generally inferior dynamics properties. But consumption with a full load turns out to be more economical than other tested vehicles with a good cross-country ability albeit lacking on soft surfaces. Maneuverability was judged satisfactory with a turning radius of 9.5-9.7 m but it was higher, meaning poorer stability. Ease of control and suspension softness were comparable to the Ya-5. Reliability overall was not assesses and needed longer tests. The design flaws noted no demultiplier, no bogie axle tilt limiters, unprotected ball joints, incorrect middle axle brakes location, and overall, the Yag-10 double gear main transmission was found unreliable with worm failures, but a better chassis confirming the choices made for the factory version.
It was in the end recommended to:
a) rearrange the reaction rods;
b) install a second support bearing of the bevel drive gear of the rear axle;
c) install axle tilt limiters;
d) install Mechanic-type cardans from the Henschel car instead of Cleveland shafts from Moreland;
d) extend the additional channels at the rear of the car to the end of the platform;
e) replace single-row ball bearings in the bulkheads with double-row swinging ones.
On November 8, 1931, the first YaG-10 was sent back to the plant for modifications and create the first modified batch. On February 2, 1932, the first roled of the line, the first of which were given to the XVII All-Union Party Conference. A column of five went to Moscow and paraded on February 8 on the Red Square, inspected by delegates. The next day they were inspected by the People's Commissar of Military and Naval Affairs, K.E. Voroshilov. He was said "very pleased with them".
"On February 9, I was able to personally inspect the first column of three-axle trucks manufactured by you. Although they did not pass all the tests, but, according to military workers, in terms of their technical data and, finally, in terms of appearance and results of running in difficult winter conditions, they fully meet the requirements placed on them. The importance of a three-axle heavy-duty vehicle is great not only for the national economy, but also for the country's defense. I congratulate you on your undoubted and very important technical achievement. It is important that it move from the prototype stage to mass production as soon as possible."
That same year, the five trucks made a test run along the Yaroslavl-Minsk-Yaroslavl route. The YaG-10 was tested all that year on various road and climatic conditions at the UMM RKKA test site. The remaining design flaws were identified and fixes. The final YaG-10 were given a demultiplier to reduce speed, and increase traction by 1.4 times on any gear. Load capacity at 8000 kg with a curb weight of 5430-6800 kg were consireded excellent, and they were able to overcome a climb at 25°. At the highest speed of 42-45 kph the operating fuel consumption was 45-55 liters for 100 km based on a 177 liters tank.
Production of the YaG-10
In simple terms: At the new reconstructed YaAZ plant, it was initially planned to produce up to 100 such vehicles annually, but the model became a small-scale affair with only 333 units produced in 9 years of production. Here is more on this:
From the very start of production, the main issue with this truck was its engine, or rather, the lack thereof. YaGAZ at the time lacked its own engine production unlike GAZ or ZIL. In 1929-1931 the Ya-5 and Ya-6 were equipped with imported 93.5-horsepower Hercules-YXC engines, but by 1932, not because new US government cracked down on communism, but by the Soveiet government itself, deliveries ceased. This decision of the central commitee was guided by good intentions, to better stimulate the development of their own domestic production and spare the loss of foreign currency.
After the reconstruction of the Yaroslavl plant, it was planned to produce at least 100 YaG-10 per year but this required completing its modernization and building a workshop for the production of engines as well. Alas, the Soviet auto industry in general and for YaGAZ in particular, any engine more powerful than 73 hp could not be produced yet. The technical knowhow was not there yet. Still, the army and industry were in dire need of heavy truck, and meanwhile, all engineers skilled for that types of engines were budy with tanks and aircraft engines.
It was suggested to copy the same Hercules or Continental engine and/or Dodge-D5 (GAZ-11) but none was powerful enough for the Soviet truck needs. The own company's 2-axle YaG-4 and YaG-6 worked on smaller AMO-3 and ZIS-5 engines, but the size and heavy chassis of the YaG-10 required a power unit tat least twice as powerful. The production was henceforth limited to how many Hercules-YXC engine were in stock. The military department already reserved all remaining Hercules for the YaG-10, but the supply ran out already in 1934-1935.
When it happened, new engines were purchased again, but just enough for a small-scale production to slowly continue until 1940. Purchases were not centralized, but made according to "whoever can" principles, so "Azneft" imported American engines on its own needs and for Yaroslavl.
Design of the YAG-10
General layout
This 6x4 truck had a 8t max capacity on road, 5t off-road. It had a ladder chassis with a 3900mm wheelbase up to the rear axle assembly and 1080mm to the rear axle. There were three seats, one unitary and a bench in the cabin and 30 seats possible in the flatbed at the rear. That made it useful to carry three average sections, so almost a full platoon.
At no load the YAG-10 weighted alone 6,8 tons, with a maximal loaded weight up to 14,8 tons. It could carry on paved roads up to 8t but only 5t off-road. It was recoignized already this was a weak load and that a better engine was needed fro the start. The truck was massive compared to the usual GAZ and ZIL light trucks, 6.97 meters long for 2.47 meters wide and 2.55 meters tall. Its ground clearance was of 42 cm.
Engine and performances
The YAG-10 was powered by the Herkules YXC 93.5 hp 6-cylinder, shared also by the YaG-6M (1938-1940). Its power/weight was 8.77 hp/ton. It was able to climb a slope of 20° wade 0.65 m (2.13 ft) of water, with a top speed on road of 42 kph and off road down to 20-30 kph depending on conditions. It had a 177 Liter fuel tank with a high fuel consumption of 46 liters per 100 km and up to 64-80 liters off road making a cruising range, loaded, respectively of 275 km and 220 km but 400 km unladen on good roads.
The Hercules-YXC-B 6 cylinder had a 100mm bore, 120.6mm stroke, a compression ratio 4.6, a cubic capacity 7022 cm3, and max power of 93.5 hp was achieved at 2,200rpm 38 Kg/m torque. It was coupled with a 4-step gearbox and double reduction gearbox, and final drive of 9.47. The tires were 40 inches x 8. The 4-speed Brown-Lipe-554 manual gearbox was also provided from the US. The suspensio came from the British Moreland Truck Company. The rear twin axle comprised a cetral hub wth essentually each axle suspended on an arm. That way, the entire twin axle could pivot aronund this hub to a high degree, ensuring all eight wheels were always on contact with the ground, whatever the reflief. While capable of carrying 8 tons on paved surfaces, that was down to 5 tons off-road as said above.
Main Variant: 29K SPAA
29K, platform up, and down, ready to fire (bottom)
The 29-K was a Anti-aircraft truck was essentually a 76 mm M1931 AA gun mounted on a modified YaG-10 truck. In 1934, the Design Bureau at the Plant No. 8 Mikhail Kalinin, received an order to install the 76 mm air defense gun M1931 on the chassis of the three-axle YaG-10 truck to test the feasability of a self-propelled AA defense. Production was completed by the Yaroslavl Automobile Plant, due to their experience with creating the SU-8. By August–September 1936, tests were carried out at the NIAP test site with the first final vehicles entering service at the Moscow Military District and taking part in the Red Square Moscow parade. A full line of vehicle was later showcased at the same place on 1 May 1934, the first batch of the sixty-one YaG-10 trucks converted into 29-K models. Modifications included a reinforced undercarriage with four stabilizing legs with jacks underside, a rotating pedestal and semi-circular armor plates that that could be reclined to create additional space for the crew to operate.
The final 29K weighted 10.55 t (10.4 long tons; 11.6 short tons) for an overall lenght ported to 7.630 m (25 ft 0.4 in) a Width of 2.470 m (8 ft 1.2 in), a crew of 5 and the ability fo fire shells, fixed QF 76.2 × 558mm R 6.6 kg (14 lb 9 oz) 76.2 mm (3.00 in) at up to 82° for a traverse of 360°. The gun had a rate of fire of 10–20 rpm depending on the crew, with the shells reaching a muzzle velocity of 815 m/s (2,670 ft/s) for a maximum firing range of 14,600 m (16,000 yd). It used a simple telescopic sight. 48 rounds were stored. The 29K was an operational range of 270 km (170 miles) and top speed 45 km/h (28 mph).
More Variants
Main Variants, with an utility cab and fuel tank.
-The Yag 10M manufactured in 1938-40 (10 built) was identical, apart its new Hercules-YXC-3 7.85 Liters CC engine rated for 103 hp at 2000 rpm for extra torque at 41.5 Kg/m. Top speed was 42 kph byt at a 55L fuel consumption to 100km. It was not mass produced.
-In 1935, several vehicles were equipped with fuel tanks from the Leningrad Promet plant, each 8,000 liters.
-Diesel: In 1934, a YaG-10 with an imported diesel engine was prepared for a diesel run. In addition, in 1938-40, 10 vehicles with a Hercules engine with a capacity of 103 hp were manufactured (code name YaG-10M).
-Fire trucks
-Bus YaA-2, extended chassis
⚙ YaG-10 specifications |
| Curb Weight | 6,8 tons |
| Weight, empty | 5,43 tons |
| Dimensions | 6.97 x 2.47 x 2.55 m |
| Weelbase+Ft/Rear Track | 3600+1200, 1750/1784 |
| Suspension | Leaf springs |
| Propulsion | 95.5 hp Hercules 6-cyl. 100/120.6mm YXC-B |
| Transmission | 4-speed Brown-Lipe-554, manual |
| Speed | 42 kph |
| Range | 100 km (60 liters) |
| Armament | |
| Payload | 5t payload off road, 5.5-6t road |
| Crew | 1 driver (16 troops) |
The YaG-10 in service
YaG-10 was produced for 9 years. And if initially it was a three-axle modification of Ya-5, then over time it gradually became a three-axle modification of YaG-3, YaG-4 and YaG-6 vehicles, but also with imported engines. Even externally, the last YaG-10s were strikingly different from the vehicles of the first years of production: different fenders, wheel rims, different cargo platforms, their location and fastenings, and finally, three different types of emblems on the radiators of the vehicles. Due to this, the late YaG-10s were sometimes designated as YaG-10A. In fact, the YaG-10 was produced from 1932 to 1940. The production was distributed by year as follows: 1932 - 35 units; 1933 - 78; 1934 - 50; 1935 - 15; 1936 - 75; 1937 - 18; 1938 - 27; 1939 - 20; 1940 - 4 units. In addition, in 1938-1940, 10 YaG-10 vehicles with Hercules engines of greater power - 103 hp were produced. Sometimes this vehicle was conventionally called YaG-10M. In total, 333 YaG-10 units were manufactured.
By the way, in addition to Moscow, Leningrad and some other large cities of the USSR, some YaG-10 units were also used in fairly remote regions; there is information about the use of these trucks in Mongolia.
In the summer of 1934, for the famous August "diesel" competitive motor rally along the route Moscow - Kharkov - Rostov-on-Don - Stavropol - Nalchik - Tbilisi - Moscow, at the request of the competition committee, a YaG-10 with an imported Beardmore diesel engine was manufactured. On the way, the car showed itself well, although it had a broken bracket of the rocket rod, but, as the commission noted, this was a consequence of the low quality of casting at the Kostroma plant, and not the design of the car. The further fate of this interesting car, which had, in addition to a diesel engine, and a slightly different cabin, is unknown.
The overwhelming majority of serial YaG-10s were sent to units of the Red Army. Mainly on their chassis artillery mounts with 70 mm anti-aircraft guns of the 1931 model were mounted. These vehicles, both those produced in the early and late 1930s, can be seen in the footage of the military parades of those years on Red Square. They were also used on the fronts of the Great Patriotic War, in particular, they were used in the defense of Moscow in 1941, and some were even captured by the enemy. In addition, the army had vans based on the YaG-10 with a radio and other special equipment.
In 1935, several vehicles of this brand were equipped with elliptical tanks from the Leningrad Promet plant with a capacity of 8,000 liters. In addition, NATI created samples of fire-fighting equipment on the YaG-10 chassis with an open cabin: a tank with a capacity of 4,500 liters and a powerful fire truck pump. In 1932, the same NATI developed a project for a bus designed for 80 passengers on a three-axle Yaroslavl chassis. In some ways, this was also a modification of the YaG-10. On September 26, 1932, the Yaroslavl plant completed testing this chassis for an extended 6x4 bus. It was transferred to the Lenkomtrans trust in Leningrad, and soon the ATUL auto repair plant manufactured the largest bus in the USSR, the YaA-2 Gigant. In 1934, the second (and last) 100-seat version of this bus was manufactured entirely at YaGAZ under the same index.
More than other YaG-10s, army anti-aircraft mounts remained in service, but after the war they were removed from service and gradually sank into oblivion. One of the fire YaG-10s was also preserved after the war, but it also eventually ended its service and disappeared. The model that most likely existed the longest was the one that was in NATI (NAMI), which was also destroyed in the 1950s. So, unfortunately, nothing remains of the first domestic "three-piece". They are now resurrected only by documents and memories.