Synchronized Side Rods

Yep, I've changed all mine also.

There was an OGR article a month ago or so on how to do this for those that are interested.

For a while, Sunset was delivering them that way too.  It is no less likely that they would be synchronized than at any other angle, but they look more like the real thing if staggered about 90 degrees or so.

One of my articulateds has a slightly different gear ratio on the rear engine, so they go in and out of synchronization.  It did not affect the pulling power at all, and even I cannot detect the periodicity of motion.  Looks random, and I know it isn't.

I was told that prototype articulateds had slightly different driver diameters on the front and rear engines.    This was to insure that they did not get synchronized and stay that way.    The difference was maybe 1/2 to 1 inch on the driver diamter.  

The RRs did not them synchronized so they did not beat up the road bed as much and also even more for going over bridges.   They did not want both engines in synch pounding on the bridge structures.

So you are very correct in thinking it does not look right for them to be in synch!

Not to mention what happens when one engine slips and the other does not...they fall in and/or out of sync.

Having them synchronized would bother me too and I would modify my model if it was that way. I would expect the manufacturers to build them not synchronized.

Easy Hot Water.  That response was a bit harsh.

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Dennis

The assembly worker just puts them together as the driver position falls.  There is most likely no specific instruction in the routing to specify the drive sets as "synchronized."

Plus, you never know, there may be folks out there who like then synchronized.

Of course, the ideal method would be to have one motor for each driver set (like the Flyer Y3.)  Then they go in and out of sync as the locomotive runs.

Rusty

Rusty, I agree. I think that would be a much nicer Vision Line feature than the disappearing coal load.

For those of you that don't like syncro-rods...don't watch. For those of you who do...go to about the 45 sec. mark.

Personally, I like to see the rods looking like a merry-mixer rather than potato mashers.

quote:

because they will NEVER actually stay synchronized, do to the harmonic vibrations of the power pulses.

Odd, I have hours of recordings of Class A locos where the exhausts do indeed stay synchronized over a long period of time and the only explanation I can come up with is because of the harmonic vibrations of the power pulses seeking a comfort zone.

Locomotive wheels are not balanced to take the vertical pounding out.  They are balanced to take the ossolation in the yaw direction, the horizontal plane, out to avoid tearing up the engines frame.  The drive train is out of balance due to both rotary and reciprocating motions.  One end of the drive rod is going around in circles and the other end is going back and forth in a straight line.  It is not possible to balance them both out. A successful locomotive is one where at top speed the wheels do not leave the rail, however a zero downward force is acceptable.  This out of balance is known as dynamic augment and is an issue on bridges.  A good book on the subject is Mastering Momentum by Lewis Silcox,  publisher is MIT Press, about 1947. 

I don't mind synched rods once in a while.  Having them always synched is simply unprototypical.  If they are off a bit on a model, it looks more realistic.

Nice video.  You can hear it going in and out of synch on the start- up, although in- synch there could be at any of the four "quartered" positions.

I think the very precise and talented assemblers put these models together in synch on purpose, and won't stop until somebody says to.

Oh - opinion!

ROTFLMAO!!  

But Jack...it was on the internet, so it HAS to be true.

Can you imagine the results if the front engine had 63" drivers and the rear engine was at 63 1/2"? Or vice versa? How many miles do you think it would take before they were all the same diameter again?

The Lionel cab forwards from 2005 had the front & rear rods aligned the same way also.

I like them synchronized.  It seems more interesting to watch.  

David Johnston is right.

When a wheel is operated by a rod or the rod operates a wheel (as in any single cylinder engine...think motorcycle singles) the balance is only in one plane and nonexistent in the plane 90 degrees to it across the wheel. Motorcycles minimize the problem with counter balance shafts operating at half speed and more of them are necessary to get even closer to perfect balance which is never achieved.

I have no idea if the track is excessively pounded by this imbalance or if bridges can suffer from it, either.

I got my Legacy CF yesterday, and now that it's tested, I will UN- sync them like I did my Sunset AC9. Looks cool when 1 set is at the top while the other set is at the bottom, just like the article in OGR a month or two back.

What model is this?

2 rail or 3 rail?

Okay Hot Water and Rich I fully understand that the all the drivers must be the same diameter.  But answer me this:  How about if the drivers on the engineer's side were all 63" and on the fireman's were 62.5".  That way you could run in a big circle all day long. Somebody much smarter than I can calculate the exact radius.   

Face it guys, if they teach you the "route-step" for crossing bridges in basic training, it is easy to imagine what a syncronized locomotive could do crossing a bridge.  

And what exactly are we imagining?

If you are trying to say that a "synchronized" locomotive would put more stress on a bridge, you're not correct. What do you think those huge counterweights are for? To BALANCE the drive wheels!

Only if there were synchronized swimmers under the bridge!

Seriously, there's no difference if it were a UP 4-6-6-4 in sync or a UP 4-12-2, you still got the same amount of drivers moving in unison.

Rusty

Rich Melvin asked:

And what exactly are we imagining?

If you are trying to say that a "synchronized" locomotive would put more stress on a bridge, you're not correct. What do you think those huge counterweights are for? To BALANCE the drive wheels!

Thank you for clearing that up and being civil with your response.

Learn something every day.

It depends whether you are writing about a Mallet or a simple articulated.  A Mallet is a compound locomotive with the high pressure steam coming from the boiler to the rear engine then being reused at lower pressure by the front engine. The engines are synchronized. A spotting feature is the front engine cylinders are larger than the rear engine.

A simple articulated is a more modern locomotive with high pressure steam feeding directly to both engines. They are not synchronized.

I do understand the aesthetics of synchronized drive rods and valve gear on our models.

The drivers go out of sync even on a Mallet.

Rusty

Yes - only the exhaust sound is synchronized.  The only connection between the two engines is the exhaust from the high pressure cylinders, and that has no effect on synchronization.

Wow. (Really, regardless of their appearance, upscale model O articulateds' drivers are

"synchronized" all the time, as they're connected, but, anyway.)

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Just to state the (you would think) obvious, as I do not see it above: an actual articulated's engines (a Challenger, for example, has two engines; an Erie Triplex, three)

are not...directly...mechanically...connected. There's no big motor in the cab driving a big shaft and worm gears. So-o-o-o...synchronization occurs only sometimes through the magic of statistics. At speed you can't see it, anyway.

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The RK and Lionmaster articulateds are very prototypical in that they have 2 mechanically independent motors driving their un-connected and un-synched engines (trucks, actually, like most O model diesels), so are actually better models than the 'spensive ones in that regard. Still can't see it at speed.  

Yes, you can see the rods at speed.

Just go to the 1:55 min. mark of Gromet's Cab Forward video.

No kidding !

I do remember reading that some prototype locomotives had slightly different size drivers for the separate 'engines' because there was a "surging" tendency if the piston thrusts were in synch for any extended time. It may have been on some of the Pennsy Duplex drive locos. Someone will dig up more on this, I'm sure.

I have an MTH Big Boy and the engines gradually go in and out of synch because they have separate motors. The electronic sound also mimics this effect.  Are there some model articulated locos with just one motor geared to all the drivers? I think it looks better if the drivers of articulated locos have a varying pattern, as with the real thing.

In theory the engines of real mallets would stay in synch, but in actuality one engine might slip sometimes.

Please identify the OGR run number for this article.

Ron

No, they are not synchronized. There is no mechanical connection between the front and rear engines. A compound articulated will drift in and out of sync just like a simple articulated.

My problem with separate motors on an articulated is that unless you do something tricky, the motor and shaft driving the articulating engine requires extensive cutting of cylinders and boiler.

So I designed a "twin spool" setup - both motors are in the firebox, and the forward engine driveshaft goes straight through the hollow worm shaft of the rear engine.  It worked, but the dropdown was by Delrin chain, and I didn't care for the noise.  Also the only locomotive with a big enough firebox was the NP Challenger.

My next attempt was the varying gear ratios on my SP MM-2, and we did a twelve part magazine article on that.  It uses an NWSL Mod O.5 on the front and an O.6 on the back.  The periodicity is - in synch once each 25 driver revolutions.  Even if I tell you that, you cannot actually see the periodicity - it just looks like all the Challenger videos - rod angles seem arbitrary.

But just setting them at different angles and leaving them there does the same thing. Easier.

RUN 272 Aug/Sept 2014

starts on page 92

I did it to my Sunset AC9, and will do the same on the new AC12

Oh you can see rods at speed....

The thing to remember is that unless a driver set slips, the rods going in and out of sync is subtle.  It's like watching the minute hand of a clock move.

Rusty

I don't care for sychronized swimming, too much make-up.   

I appreciate the info.  Will have to stop by local toy train shop this week to check out a copy.

Ron

I tracked down some information about different size drivers on duplex-drive locomotives, in the Kalmbach book "Guide to North American Steam Locomotives", page 324:

"In the mid 1920's [regarding larger locomotives] ... Alco pushed three-cylinder locomotives, and Lima developed the Super-Power concept ... Baldwin ... began advocating duplex, or divided, drive."

"The duplex drive represented an engineering compromise. Main and side rods could be lighter ... easier to counterbalance ... the worst problem was the independence of the two sets of running gear. When they were in phase (running in unison), they created a surging, fore-and-aft motion in the train. Minor variations in adhesion, caused by something as trivial as the locomotive entering a curve, caused one unit to slip, throwing the load on the other, then regain adhesion - among the results were rough handling of the train and radical changes in draft that lifted the fire off the grates ..."

"Baltimore & Ohio built its own [4-4-4-4] duplex-drive locomotive, #5600, in 1937. Both sets of cylinders were the same size, 18" x 26", and the rear cylinders were mounted backwards, under the outer edge of the firebox and ahead of the trailing truck. During testing B&O found that the two sets of drivers gradually got in step with each other - ideally they should be 45° out of phase - so the road turned the tires of one set down from 76" to 75", which, assuming no slipping, made the two sets of drivers go in and out of phase with each other three or four five times a mile ... It was taken out of service in 1943 and scrapped in 1950."

I'm wondering if this "surging" phenomena was noticed on articulated locos if the drivers happened to all get in synch. Perhaps it was more of an issue on the duplex-drive units because of taller drivers, faster speeds, higher steam pressures, shorter cutoffs, different valve gear, adhesion problems, multiple factors?

Why they didn't add inside cranks and rods to connect the two sets of drivers on a rigid-frame duplex to maintain eight evenly spaced power strokes per drive wheel revolution, and gain significantly improved traction? The inside rods could have been offset from the outside rods to minimize the need for counterbalancing. But that would have increased the mechanical complexity, and the maintenance of inside motion tended to be neglected.

My O-gauge Big Boy drivers go in and out of synch periodically Something has to slip, going around the curves. . Makes it more interesting, I think.

I think the best answers to the problem of the Duplex drive were achieved by the NYC S-1's, the N&W J's, and the UP FEF's.   All were conventional 4-8-4's which used modern light-weight alloy rods, and modern counter balancing idea to achieve reliable operations over 100 MPH without the problems of dynamic augment (like older designs of conventional steam locomotives), and the problems of surging and slipperiness
(like the Duplex drives).

Stuart

You can still feel the "surging" as the 844, 4449, 3751, 765, or 261 start and accelerate, when riding behind either of them.