I seem to remember reading somewhere that engineers didn't like the C636 because it had a tendancy to sway side to side and front to rear at certain road speeds. Almost like a dutch roll in an aircraft. The article may have been from an IC engineer and they were refering to this behavior being especially disconcerting on narrow bridges. Has anyone heard of this and know why it was happening? Does anyone know of the article or book this was mentioned in and where to find it?
Thanks
A reference to this appeared in an article in Trains a few years back, I believe it was an Alco themed issue but not totally sure. The author said when he was new he was on a train with these engines and at a certain speed was told to hold on because they rocked violently.
I have ridden for hundreds of miles in C636s and M636s fitted with Alco High Ad trucks and they always rode very smoothly with not the slightest suggestion of sway or rough ride of any kind.
The problem with the IC units in particular was the poor quality of the track and the fact that the truck suspension could resonate from the regular inputs from dipped rail joints at certain speeds.
I had no problems because the track was welded from new and 136lb/yd and maintained well.
M636C
There are significant differences between the Alco High-Ad truck and the Dofasco High-Ad truck that was used under the MLW production. The latter had a shorter wheelbase, which I understand resulted in less weight transfer and better adhesion. Apparently ride quality did suffer at higher speeds, especially when the crews were comparing it with an SD40-2..
John
cx500 There are significant differences between the Alco High-Ad truck and the Dofasco High-Ad truck that was used under the MLW production. The latter had a shorter wheelbase, which I understand resulted in less weight transfer and better adhesion. Apparently ride quality did suffer at higher speeds, especially when the crews were comparing it with an SD40-2.. John
I'm well aware of the differences between the Alco Hi Ad and the MLW design trucks.
I should have said that I was talking about Australian built locomotives. Mt Newman Mining, later part of BHP Iron Ore and later still BHP Billiton had seventeen C636 locomotives twenty seven M636 locomotives built by A.E. Goodwin in Sydney NSW. Since Mt Newman engineers were sceptical about the advantages of the MLW truck design the M 636 locomotives were built with Alco High Ad trucks which worked well on Mt Newman's good track and generally broad curves. Hamersley Iron, who had sharper curves had all their M636 units built with MLW design trucks.
BHP iron Ore had 33 of their C636 and M636 locomotives rebuilt as GE Dash 8 locomotives, retaining the Alco High Ad trucks and these are still running in main line service today (although more than 70 SD70ACe units are in service - China keeps buying more Iron Ore).
I know that no Alco High Ad trucks were used on Canadian built locomotives. But many M636 locomotives were built in Australia and many of those had Alco design trucks. The truck castings themselves were made in Australia, even for the MLW design. Only one pair of trucks used in Australia carried "Dofasco" casting marks but one of these is in a museum now...
My screen name is our local name for the M636 with Alco trucks, M636C standing for "M636 with Century trucks". Since MLW called its C630s with MLW trucks "C630M", our description is the reverse...
But the Alco High Ad trucks are still running daily in heavy iron ore service, up to 50 MPH with empty trains, now under GE prime movers without any indication of sway or pitch. Some of this is due to good track but the truck was a good design. Many years ago I leaned well out of the cab window to look down at the truck as it negotiated the sharpest main line curve and watched the curving action.
The big external bolster springs are "flexicoils", a term often identified with EMD, and these flex to allow the truck to take the curve.
The M636C units were Mt Newman numbers 5469 to 5495, built from 1969 until 1975.
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