Large Scale Central

Two diverse questions

Prototypes
#1

Q #1 - For logging fans - I’ve noticed on just about every Shay that I’ve ever seen that the drive-lines seem to be 45 degrees out of sync from each other. A look at the square-drive section of the joints would seem to confirm that on any Shay. Is this to prevent a possible drive-line lock-up?

Q #2 - For CP mavens - when did CP stop putting place names and so on on the coach-sides of the maroon passenger car stock? The new ‘fake’ CP cars from AccuCraft will have neither numbers nor names [if indeed they are applicable], and I’d like to put my own Canadian place names and peoples’ names on them when they finally arrive. Stan Cedarleaf doesn’t know it yet, but he’s going to make the lettering for me.

If this idea/plan causes offence to some of you PC types reading this - tough.

tac
Ottawa Valley GRS

#2

tac Foley said:

If this idea/plan causes offence to some of you PC types reading this - tough.

tac
Ottawa Valley GRS

PC as in Penn Central? I don’t know how asking about other lines could offend them :]

I don’t know about prototype practice on the Shays (I’ll have to review some pictures) but I’ve been told when assembling the slip joints on my models that the universal on either side of the slip joint should be oriented the same way, not 90 degrees out to reduce binding.

But then I imagine you are speaking about the drive line on either side of the cylinders? I’ve never actually taken notice of that.

#3

Yes, I’m talking about the actual drive-line from the cylinders out to the trucks - on every Shay I’ve seen [fullsize, that is] they are 45 degrees out of sync - clearly visible.

PC - politically correct, not Penn Central. There ARE a few piccy persons around who like to rip a furriner a new one every now and then, just to show their supposed intellectual superiority. I’m asking because I don’t know, not because I’m a wise-ass.

Best

tac

PS - are you still coming over? Let us know when, as we might cross in mid-Atlantic as we head over to CN or OR.

#4

Yes, they are 45 degrees out on the geometry of the universals to help them go around curves. I think it is because on a curve when the drive line is angled the rotation goes slow-fast-slow-fast. If they are set 45 degrees out it must help to keep things running smoother. Not exactly sure though.

They seem to be about 45 degrees out in this shay and same on my AC 3 truck shay model also.

(http://upload.wikimedia.org/wikipedia/commons/thumb/7/7b/ShayLocomotiveEngine3320.JPG/639px-ShayLocomotiveEngine3320.JPG)

Here is a link to a published illustration specifying 45 degrees.

http://www.freerails.com/view_topic.php?id=1762&forum_id=20&page=2

Andrew

#5

I did know what you meant; just having a little fun with you!

Not coming this week - maybe next!

#6

Thanks for posting the links, Andrew, although your image doesn’t show what I meant as it does not extend far enough left and right. The Hooke joints that make up the actual articulation of the drive-line are pivoted by a simple pin joint, as a look at even a Bachmann Shay would show. As such, there is a possibility of them locking under turning and rotational forces, causing a whale of problems. With the full-size loco, or the live-steamer, where the torque is developed by the steam motor and passes out equally at each end, this is necessary. But in an electric model, like the Bachmann Shays, the torque is developed by each motor block separately, feeding into the dummy steam engine.

Just wish I could get the hang of posting images here - the Shay up by Oregon Zoo in PDX is THE definitive example for me.

tac
Ottawa Valley GRS

#7

Yes…the slip joints are 45 degrees out of sync for that purpose…it does make a diffenence…on the Bmann Shay only the front motor block causes the drivetrain incliding the cylinders and crankshaft to turn, the gears on trucks 2, 3, or 4 are just freewheeling…

#8

Yup, I already figured that out, thanks, I have two two-truck and one three-truck - all lettered and heralded for the Port Orford Coast RR and the Old Mill Lumber Co.

Now, having sorted THAT question out, howsabout the CPR lettering?

tac, ig, ken the GFT & The Port Orford Dock-lift Boys

#9

Tac, I was disappointed the image was not a little wider too but you can just see the orientation of the pins and shafts within the rings that contain the pivot points at the edge of the image. The square shafts looking 45 degrees out is a result of the rings/pivots being 45 degrees out.

When the driveline is angled on a corner those rings warble around. The energy that makes them warble is the result of the transmission loss in the varying rotation due to the geometry of the universal joint. The output from the universals when angled will accelerate and decelerate twice per revolution. I figure if they were both the same, the varying transmitted rotation would be in sync resulting in vibration/shuddering around corners. Being out 45 degrees helps dampen things out. You would think they should be 90 degrees out for the effect to be out of phase to each other but maybe that would be too oppositional creating similar vibration so a softer 45 degrees is chosen. I suspect the acceleration/deceleration is reversed on the second joint so that should not effect the rotation in the truck and wheels. I don’t understand why they would lock as you say, perhaps I figured it incorrect. I am all ears.

Models with motors in the trucks only being connected to one end of the engine block is an entirely different issue. If both were joined, the blocks differing speed and effects via the universal joints would bind and create unnecessary forces on the parts we like to see spinning around which are only there for aesthetic purposes. On a model with motors in the trucks, the driveline has no functional aspect. The acceleration/deceleration of the shafts would have little inertia/vibration effect so not so necessary to be 45 degrees out.

I did have a little problem at first posting the image. It posted into the editor but not display on the final post. I eventually pasted the URL address of the image in the post as a hyperlink and the server converted it into the appropriate HTML for display. I was pleasantly surprised that it did as I originally intended.

Andrew

http://en.wikipedia.org/wiki/Universal_joint

(http://upload.wikimedia.org/wikipedia/commons/b/b5/Universal_joint.gif)

(http://upload.wikimedia.org/wikipedia/commons/thumb/f/fd/UJoint1.png/640px-UJoint1.png)

#10

Thanks for the great post, and yes I understand the principal of the Hooke joint, as it is called, as I noted I my post prior to yours. However, yours has a movie in it!! Howja do that?

Anyhow, 90 degrees difference makes absolutely NO difference at all, but 45 degrees allows an angular variation. As for the model drive train, the ‘clutch’ drive is a feature of ALL of Bachmann’s geared locos, after their initial disastrous introduction - all three designs, Shay Climax and lastly the Heisler, suffered initial inflexible couplings that led to ‘wind-ups’ and busted joints in the first versions, that were remedied by simple relaceent of the afflicted components. Thankishly, ALL of my Bachmann geared locos are second runs, and do not suffer from transmission wind-up. But then, I’m not trying to run them on R1 curves either - my tightest bend is 13.5 foot radius.

Best

tac
Ottawa Valley GRS

#11

Tac, the Hooke Joint, Universal Joint, Universal Coupling, U Joint and Cardan Joint are essentially the same thing just different names. Hooke however was the first to realize that this type of joint accelerated/decelerated when there was an angle involved and how that related to shadows casting across sundials. The design with the outer ring is geometrically no different to what we find on a car tailshaft. I suspect the rings act centrifugally to take side load of the bearings.
90 degree difference on each side of the engine block does make a difference as the joint pivot pins would be 90 degrees different on each side which would then make each side shaft near out of phase during the accelerate/decelerate cycle. (Equivalent to overlaying the above chart by 1/4) That would produce opposing vibration effect rather than a compounded one. That’s why I figure they chose 45 degrees to dampen things out. It has nothing to do with the square shaft but everything to do with the joints and the way the pins are oriented. The square shaft rotation appearance is just a product of where the pivot pins are on the joint.

Have you noticed that at each end of a regular drive shaft the pins are the same way so when there is a similar angle at each end the shaft will accelerate/decelerate twice per revolution after the first joint but the opposite will happen through the second joint therefore the result/wheels will not accelerate/decelerate. If the pins were 90 degrees out on each end of the shaft the accelerate/decelerate effect would double at the result/wheels rather than canceling the accelerate/decelerate effect out.

Therefore, there is a correct way we should slide the square shafts together on our model shays although it is not critical if we have slip clutches etc, the engine crank will just accelerate/decelerate around corners when not correct. That may be another reason why some people got excessive wind up and busted things on earlier models.

I think I got all that right. It has been an education pondering this. Thanks for posing the question. I will attempt to confirm all when I next chat to a loco engineer than knows his shays. They drive through the bottom of my yard regularly.

The movie is just an animated ‘gif’ courtesy of wikipedia commons. It’s good to visualize these things although it will do your head in eventually…

Andrew

(http://upload.wikimedia.org/wikipedia/en/thumb/b/bc/SonoraUJoints.jpg/640px-SonoraUJoints.jpg)

#12

Ah well, it seems that 50% of my car names problem has been solved. Only observation, sleeper and diners ever got names in the Grove car era…which these non-descript cars would almost emulate, but not quite.

Thanks, Fred, for the phonecall and chat - it’s always good to hear from you over there in Reality World.

There are, it seems, only three Hudsons here in UK that anybody runs, or not. The one guy who has a sixteen-car consist has never had them out of the crate, as far as is known. Pure waste.

tac