Hi everyone , browsed again through my files and found a spec sheet of what would be the biggest scraper . A heaped volume of 74 cu yd is mentioned and not less than 1400 hp .
Found also pics of these tractors coupled to Wooldridge scrapers . Well , that is quite a volume of dirt .
In the sixties I found smaller MRS tractors in our country , coming from military surplus . I was always surprised about these heavy , mass fenders over the drive wheels .
The Netherlands , johan7 .
Interesting details Johan and others.
This appears to be a different model than the 250-T. Spec sheet Johan put up, shows pair of VT12-700's at 635 fhp.The 250-T pic shows 430hp in the pan - I'm guessing is a 12V-71T with those RG Let style venturi exhausts or an 8V-92T. Cant see it clear enough to confirm. Also the pan is 74.cyd heaped compared with the 250-T at 90cyd. Did it get confirmed the 250-T is a coal bowl, maybe the hungrys take it to 90cyd on the same animal?. It does'nt say what brand of transmission, shows 6-speed with lock-up, maybe an Allison?. 15' cutting edge is a big pan, look at the rear tires specs at 44.5/45.
I understood MRS acquired Wooldridge in C.A and used their open bowls and used Hancock for the Elevating scrapers?. Edit: Correction. Was Curtis-Wright.
There was no prime mover that could pull these things at the time hence the MRS 4-wheel tractor. The only one around that was close at the time was the Michigan 410 overhung with a 16V71-T at 635hp or V1710-C and 44cyd heaped open bowl which was a prototype and only 20 made before scrapped. They tried the 410 wheel tractor with the 44cyd Hancock 444 elevator but did not go further with that because the 444 had 2 x 250hp electric motors on the elevator and the 410 did not have the generator so hydraulic motors were tried on the elevator and the tractor hyd pumps could not drive the elevator under load and the thing was flagged off. Hancock called in the LW-800 4-wheel Speedpull as the tractor unit. Cat had the tried and true 666 and 660 going out in big numbers anyway so why bother.
I had all the books on the MRS including these years ago but got rid of it all when I moved.
More MRS history would be good. Big scraper history is interesting.
Cheers
Addendum:
We may have the answer to the above:
Source: construction equipment.com
Some very large capacity scrapers were developed by M-R-S in the 1950s and 1960s. The 500-horsepower M-R-S 250 tractor, when coupled to the 41-yard heaped capacity Wooldridge OS-300B scraper, was billed as the world's largest rubber tired earthmover when launched in 1955. On a good haul road, the outfit could attain 34 mph in top gear. An even larger scraper, the 250-series, with capacities up to 65 cubic yards heaped, was available for the M-R-S 250 tractor in 1961. And some high-volume versions were offered for coal handling, including one of the largest volume single scraper bowls ever made, the model 250T, which could carry a heaped load of 90 cubic yards! This monster incorporated a 430-horsepower engine on the rear, and was drawn by a 430-horsepower M-R-S tractor.
This one shows an orange I-250 Industrial Tractor with 4 wheel drive & 675 rbhp pulling a CS-250 High Capacity Coal Scraper 65 yd heaped capacity.
Picture credit and information: Rocko from Redpowermagazine.com.
And here is another 250. Interestingly, it has an 11' cutting edge?
