…That is wild…! I just can hardly imagine where they found the room to clear that first axle…bend or not…But I stand corrected. Looking at the crank in the photo in a former post and seeing the size of it all, I had a difficult time positioning that at the 2nd axle and have enough clearance for the mechanicals passing over the first axle to do the job…I’m trying to imagine if some of those mechanicals got loose inside there what a mess and problems that must have caused…I’d say it would have been an imediate derail if that piston rod or rod connecting the crank on the 2nd axle got loose the show was all over…
The UP 9000 center cylinder drove the 2nd driver and despite the already long wheelbase there was extra space between the 1st and 2nd drivers. The outside cylinders drove the 3rd driver. I’ve never seen a really good picture, but I believe the 1st driver must have had an additional offset for clearance. Could the inside rod itself have an offset or be curved???
The 9000’s with double Walschaerts gear had the air pumps moved from the front to the opposite side for better balance, so they were easy to spot. According to one book I have, before they were rebuilt with cast cylinders and frames, a common problem was the inside rod breaking and punching a hole in the bottom of the boiler.
I understand 3 cylinder locos were smooth running engines, but how were they counterbalanced? I assume the crank would have an automotive style counterbalance, but wouldn’t some of the drivers need extra weight?
This was honestly a worthwhile and informative thread. Great question. Great answers.
Pretty much the same thing if the side rods came off, too.
…Yes, the side rods would have the possiblilty to cause trouble too but the 3rd rod being capitive inside the track guage…has pretty much no where to go and a great possililty of getting under one or more wheels for the derailment…
I have trouble believing that the main rod could punch a hole in the bottom of a boiler, but I do see how it could put a crack in the boiler causing a boiler explosion. Just a thought.
Balanced-compound 4-4-2s came in all arrangements: I think all the SFe engines drove the lead axle with all four cylinders, but several RRs drove the lead axle with the inside cyl and the second axle with the outside, and UP got a couple with all four cyl driving the second axle.
I can’t imagine the inside rod being curved on a UP 4-12-2, because of the huge stresses involved. Possibly an offset on the inside rod.
Think pole vaulting. [xx(]
…Not a good thought…I often wondered if a side rod was lost what all kinds of trouble that really would cause…Can one imagine the imbalance {even if it stayed on the rails}, until it was stopped…And if it came unfastened at both ends…where would it end up flying…?? All kinds of possibilities.
One of the other things I read about, on the subject of failed siderods, especially on a camelback, is that they were a hazard to the engineer; it could shear off the entire side of the center cab. And if it happened to be the engineer’s side… [:O]
I read recently that “Green Arrow” (the only survivor of a once numerous class of General Purpose , or “Mixed Traffic” as we say over here, 2-6-2’s designed by Gresley) recently broker its inside connecting rod while on a main line outing between Scarborough and York (the loco’s base). Amazingly, after a quick inspection it was allowed to limp back to York with its train on 2 cylinders and was only 15 minutes late on arrival their.
Back in the 1950’s a Bulleid “Merchant Navy” pacific suffered a crank axle fracture whilst hauling “The Atlantic Coast Express” from Exeter to London Waterloo at speed and derailed. As a result the whole class (and the 110 strong West Country class) were grounded and modfiications made to the crank axles. During this time locos were loaned to the Southern Region of BR by other regions; these included some of the “Green Arrow” class referred to above!
In Germany we have at least three active three-cylinder steamers: 01 1100 , 01 1066(both oil-fired) and 03 1010 still going strong and allowed to top speed, capable of running up to 85 mph. There´s still another, 01 1102 oil-fired, with shrouding, capable of at least 90 mph, on trials 100 mph.
Other engines are stored but can surely get a revival during next years, among them four cylinder-compund ex-bavarian S3/6 18 478 or three cylinder, oil-fired heavy decapod 44 1093.
If you want to see pictures, please e-mail me, I will send you some images, taken at high speeds, panning shots, some on heavy trains. Sorry, threading pictures directly doesn´t work(yet)
Tom at T011066@aol.com
As noted earlier, on UP 4-12-2’s and SP 4-10-2’s the first axle was likely provided with an offset in the middle (sort of a small crank) for the extra clearance required. Can’t find the diagrams at the moment. The inside rod was not bent!
…Those camelback designs…I doubt if they could get very far passed OSHA inspection in today’s world…With the engineer perched out there on the side of the boiler it seems he would have been in grave danger if anything happened…And how did he and the fireman communicate while on the go…The whole concept just seems so nutty…In fact the position of the engineer and fireman on any steam engine except the cab-forwards seems like they were hidden out of sight as much as possible making it quite “blind” as to what was coming up in front of them, etc…I don’t understand how they really knew “where” they were on a snowy or foggy night that would make it hard to find “landmarks” ,etc…How fast to be running, etc…