The Caterpillar DW15 Revisited
Back in the May 2005 issue of Contractor we had a look at Caterpillar’s DW10 successor, the DW15. Page space was a bit limited then and in the intervening years I have uncovered quite a bit more material so here is an expanded and updated look at the last of Caterpillar’s small 3-axle motor scrapers.
Interestingly, the DW15 started out as a modified back end for the existing model DW10 until it was discovered that the current model DW10 tractor unit was a little underpowered for the task and had difficulty hauling the expanded capacity scraper.
So Caterpillar engineers set to and redesigned the DW10 tractor, lengthening the frame and inserting an all new engine, the 150 horsepower D326, into the modified machine.
They called the new machine the DW15 and it went into full production in 1954 as the DW15 series C and carried the serial number prefix 45C.
It was matched with the No 15 scraper and rated at 10 cubic yards struck and 13 cubic yards heaped.
The new tractor scraper combination was well liked by contractors who bought 400 of them during the first two years they were available.
Flywheel horsepower was increased to 186 at the end of 1955 and direct electric starting was also offered as an option.
Up until this point, almost all Cat diesel engines featured a small 2-cylinder gasoline starting engine to crank the main engine over so this was a radical departure from the norm.
While the machine was still called the DW15 series C, the serial number designation for the 186 horsepower machine changed to 59C for the direct electric start model and 70C for the traditional gasoline starting engine equipped variant.
The scraper remained the same, the No 15.
You can tell the difference between early DW15s and later models by their exhaust pipe position. On really old machines the exhaust pipe is on the left. When Caterpillar went to the higher horsepower engine, the exhaust pipe position was shifted to the right.
Caterpillar made two more variants of the DW15, the DW15E and DW15F.
DW15 series Es were in production from 1957 through to 1959 and carried the serial number prefixes 75D (direct electric start) and 76D (gasoline starting engine).
They featured a boost from 186 to 200 flywheel horsepower and Caterpillar’s new No 428 “Lowbowl” scraper which was rated at 13 cubic yards stuck and 18 cubic yards heaped.
The final version of the DW15 was the DW15 series F which was only in production for a year before being discontinued and very few were manufactured.
Caterpillar did not assign new serial numbers to distinguish between the E and F series machines but a little research has uncovered the change took place around s/n 76D816.
The DW15 was a very successful motor scraper for Caterpillar, and the machine’s reliability and good reputation helped to reinforce Cat’s place in the scraper marketplace.
The DW15 was replaced by the first of the new “600” series machines, the 619B, which was introduced in mid-1959.
The Caterpillar DW15 described.
The Caterpillar DW15 was a 3-axle machine powered with a 6-cylinder, naturally aspirated Caterpillar D326 diesel engine rated at 150 flywheel horsepower.
This was connected to the transmission by a double plate 16″ clutch with an air booster to ease the operator’s load somewhat.
A 5-speed, constant mesh manual transmission with an auxiliary box was fitted, giving an effective 10 forward and two reverse speeds.
Top speed was 24mph on the flat and much faster downhill!
Stopping power was provided by full air braking on the tractor drive axle and scraper axle with the scraper brakes synchronised to brake first, hopefully preventing jackknifing.
The tractor drive wheels could also be braked individually to help minimise wheelspin in slippery underfoot conditions.
A worm & ball steering system was employed with a hydraulic booster manufactured by Vickers USA.
The steering axle was pinned in the centre and could fall and rise with undulating ground. A large leaf spring pack provided a measure of shock absorption for the operator.
On the left side of the machine was the operator’s compartment.
This was narrow and very basic with the only creature comforts being a sprung suspension seat and a windshield.
Directly in front of the operator, bisected by the non-adjustable steering column, was the instrument panel which was quite comprehensive for the time and contained a tachometer to help with determining gear shifts.
Clutch, brake and throttle pedals were on the floor with the gearshift levers to the operator’s right.
Bowl controls consisted of two levers which activated the No 27 cable control fitted to the tractor unit’s rear main case.
Visibility from the operator’s seat was very good, especially to the all-important cutting edge.
Unlike its larger sibling, the DW20, the DW15 was always supplied with fenders on the front and rear of the tractor unit to protect the operator from debris thrown up by the wheels.
The No 15 scraper was an adaptation of Caterpillar’s No 70 towed scraper and was attached to the DW15 by a conventional king pin yoke allowing unrestricted movement.
Operation was by two part cable, one which lifted and lowered the bowl and the other which lifted and lowered the apron and was sequenced to bring the ejector forward when the apron was at full lift.
The ejector was returned to loading position by four very large springs.
For the operator there was a cab with a heater.
Other options were limited to tyres, but the really exciting extras were those offered by one of Caterpillar’s cadre of attachment manufacturers.
Athey Products Corp offered a rear dumper, bottom dumper and side dumper in place of the No 15 or No 428 scraper.
The New Zealand connection
A very popular motor scraper in New Zealand, there were over 30 examples imported by NZ Caterpillar dealer Gough, Gough & Hamer covering the entire production series.
Biggest fleet user was the NZ Ministry of Works which had nine and other owners included W Stevenson & Son, McBreen-Jenkins, Highways Construction and Feast & McJorrow to mention just a few.
There is at least one DW15 in preservation plus the odd examples which are still at work, as the DW15, minus scraper and with the addition of compaction wheels, makes an excellent self-propelled compactor!
The DW15’s scraper of course can be turned into a towed scoop and many of these, with modification and the conversion to hydraulic control, are still in use, almost 60 years after they came off the production line.
For the Diecast Model Collector
None is the word. There have been no models issued in any scale of the Caterpillar DW15 which is very unfortunate.
For the brave there is a 1:25th scale Cat DW10 model issued by Reuhl in the 1950s which is astronomically expensive.
This, with a lot of work, could be crafted into a first production DW15 but you would need time, lots of patience and very deep pockets.
Brief Specifications – Caterpillar DW15 series C
Tractor – 45C series
Engine: Caterpillar D326, 6-cylinder inline diesel rated at 150 flywheel
horsepower at 2000rpm
Clutch: 16″ double plate with air booster
Transmission: Caterpillar 5-speed constant mesh manual with auxiliary box
Top Speed: 24 mph
Tyres: Steering Axle – 12.00×20, 14 ply
Drive Axle – 21.00×25, 20 ply
Brakes: Full air operated shoe type, sequenced to brake scraper first
Steering: Recirculating worm & ball with hydraulic booster
Turn Circle: 36′
Scraper – No 15, 4W series
Capacity: 10 cubic yards struck, 13 cubic yards heaped
Control: All cable through Cat No 27 rear mounted PCU
Tyres: 21.00×25, 20 ply
Cutting Edge: 3-section, 8′ 6″ wide
Op.Weight 22.1 tons empty, 38.5 tons loaded