Wheel size question for the Bachmann man

[mudhen]

I have installed an Air Wire battery control system and P5 phoenix sound system into the K-27 .
It runs great and to all who responded to my questions on this board , a big , big THANKS . My hat is off to you all . But I still have one more question ( for the bachmann man ) , Besides when will you have the  chuff synchronization working .
My down fall for me in this hobby is I am a rivet counter . Which can sometimes be a bad thing to be .  My question to you ( finally ) is What is the size of the tender wheel as compared to the driver wheels . My sound system sounds great but it / or should I say I can't quarter it right . Its off just a bit and I was told if the tender wheels are half the size of the drivers , by cutting a hole to fit the phoenix reed switch into the front of the tender  and placing a magnet on the Axle of the first or second wheel of the lead tender truck , this will quarter the sound system to a " T " .  Is this so . 
Thanks in advance   Mudhen
   

[the Bach-man]

Dear Mudhen,
I don't know the exact sizes. Why don't you measure yours and let us know?
Thanks!
the Bach-man

[Jon D. Miller]

Mudhen,
You can get very close, but I doubt the chuff will ever be spot on.  It's not only the ratio of the tender wheel size to the locomotive drivers, but also the placement of the magnets on the axle and  reed switch placement.

With some experimenting on magnet placement and the reed you can get very close.

With your calibrated ears and eyes the sound sync may not satisfy you, but few if any will pick up the slightly out of sync chuff.

Good luck.

JD

[James]

This may not work for you, it works great for me but then I am not super picky.  It is so close to 4 chuffs per driver revolution You would have to run the engine very very slow to be able to tell it is not.   I put 3 magnets on a tender wheel and place the reed switch on the truck.  Using Phoenix Sound
the chuffing starts as soon as the engine moves.

James

[Charlie Mutschler]

Wheel diameters, K-27 Class: 

Pilot / Trailing trucks:  28 inches
Drivers:  40 inches
Tender truck wheels:  26 inches

Has anyone looked into a sound cam for a driving axle, like the ones used on some of another manufacturer's locomotives?  This would give the correctly synchronized four exhausts per revolution of the drivers.  Inquiring minds want to know and all that sort of stuff.

Charlie Mutschler
-30-

[Kevin Strong]

I believe TOC wrote up a procedure for mounting magnets on one of the driver axles. It exists online somewhere, though I don't recall where, exactly.

Failing that, I'd be tempted to use the trailing wheel, as it's close to 30". You could put your chuff sensors 120 degrees apart and come VERY close to matching the 4 chuffs per revolution of the drivers. I've used that "cheat" on a number of locos, and you really can't tell it's not 100% synched.

Later,

K

[StanAmes]

If you hook up the battery to the P5 as detailed in the CVP instructions for AirWire installations and you use the inversion transistor for the P5 then the K27 internal optical sensors will work as expected.

Their is one sensor in each cylinder. You can select only one cylendar for a 2 triger chuff  or use both sensors for the more prototypical 4 cylinder chuff.

My k27s optical chuff produces a slightly out of time chuff which is protoitypical for an out of square locomotive.

When a locomotive first comes out of the shop the cylinders are in square and produce a chuff that is in time.  As the locomotive is used D valve adjustment will move slightly and become out of square.  When this happens the chuff becomes slightly out of time.   Because the Bachmann locomotive is one of the few that has chuff trigers in each cylinder it is one of the few in the market which can produce this realistic chuff.  By adjusting the triggers you can adjust the square of the locomotive as you desire.

Hope that helps

Stan Ames

[mudhen]

Thanks to Charlie Mutschler for the wheel sizes , and to all for the different ways to add the chuff . All suggestions are very doable but I would like to talk to Stan Ames first about the optical chuff censors  in the K-27 . So to Stan Ames can you contact me at ([email protected] ) so I can get more imformation on hooking up to the optical censors . I like your way of doing the chuff the best
Thanks to all for your responses.
Mudhen

[Kevin Strong]

My k27s optical chuff produces a slightly out of time chuff which is protoitypical for an out of square locomotive... 

That's one way to look at it. The out of "square" ("quarter" is the correct term) chuff on the K-27 is caused by the tabs that break the optical path not being exactly in the center of the throw. I don't know if this can be easily adjusted to get the beats even. According to Phoenix, the amount of the offset varies from one model to another, and is a weakness of the design, not a "feature" as may be inferred from Bachmann's installation instructions (and Stan's post).   

When a locomotive first comes out of the shop the cylinders are in square and produce a chuff that is in time.  As the locomotive is used D valve adjustment will move slightly and become out of square.  When this happens the chuff becomes slightly out of time. 

Not exactly. The off-time chuff caused by the optical sensor in the K-27 results in a "chu-chuff, chu-chuff" sound. In the prototype world, this would be caused by the wheels themselves being out of quarter. If a shop foreman heard such an irregular cadence coming from a locomotive, it would be pulled and inspected. There's a distinct mechanical reason why drivers are placed exactly 90° to one another. Another cause for such an off-time cadence could be the valve gear slipping. Again, this would be cause for the locomotive to be pulled and the valve gear reset. Yes, locos ran with such irregularities, but they were most definitely the exception.

The above scenario is different from the far-more-common irregularity in valve timing which gives us the more familiar emphasized beat (CHUFF chuff chuff chuff) where all four beats are still evenly spaced. This could be caused by wear, but more commonly was simply inherent in the mechanics. Valve timing was (and still is) a black art.

Technical note - the K-27 has piston valves, not D valves. Piston valves proved superior to D valves on locomotives which used a high volume of steam. They were also reportedly less prone to problems stemming from wear.

Later,

K

[Charlie Mutschler]

A follow up to Kevin's post.  He made the main point - the Bachmann model is of a PISTON valve equipped K-27.  Only four (450, 451, 457, 460) were never rebuilt with piston valves, and carried their simple slide valve cylinders to the end of their service lives.  Of these, it appears that only No. 460 saw regular service after 1929.  All of the photos I have seen of 450, 451, and 457 after 1929 are stored out of service, often with some parts missing.  The four slide ("D") valve K-27s were all scrapped in 1939. 

The K-28, K-36, and K-37 classes were built with piston valves and superheat.  No slide valves there. 

Charlie Mutschler
-30-

[JerryB]

I thought I remembered reading that the optical chuff actuators don't start producing a trigger signal until the locomotive power input voltage was high enough to power the optical source and detectors. If that's still the case, it would mean the locomotive is in motion before the first chuff is heard.

I don't (yet) have a K-27, so can't test this. My Centennial 2-6-0 with mechanical cam switches and a battery powered sound card makes a chuff on first motion. Is the K-27 the same or is the sound startup delayed due to using optical sensors?

An inquiring mind wants to know.

Happy RRing,

Jerry

[Tony Walsham]

snip
I don't (yet) have a K-27, so can't test this. My Centennial 2-6-0 with mechanical cam switches and a battery powered sound card makes a chuff on first motion. Is the K-27 the same or is the sound startup delayed due to using optical sensors?

An inquiring mind wants to know.

Happy RRing,

Jerry

Hi Jerry.
The RCS PnP-3 R/C inverts the optical timer signal and it starts immediately.  Exactly when it is supposed to.

[Kevin Strong]

I thought I remembered reading that the optical chuff actuators don't start producing a trigger signal until the locomotive power input voltage was high enough to power the optical source and detectors.

That is the case when running on regular track power. The optical sensors don't start functioning until around 5 volts, and the locomotive begins to move around 1.5 volts. Bachmann has published instructions on adding a small diode circuit to remedy this problem:
http://www.bachmanntrains.com/home-usa/k-27/installdocuments/Dallee_Sound.pdf

When running on DCC or R/C, this isn't an issue, as there is full voltage available to all accessories as soon as power is applied to the board from either the rails or batteries.

Later,

K

[Kevin Strong]

I should clarify an earlier post...

An "out of square" locomotive is one where the valve timing has changed (for whatever reason) to where the locomotive is not running at peak efficiency. This is typically manifested in an uneven volume for each exhaust beat (CHUFF chuff chuff chuff). Note that such irregularities in the volume of the exhaust beat may also vary based on the position of the Johnson bar (i.e., "cut-off"). Ideally, all four beats should be equal, but the real world was often not ideal. Most steam locomotives have some level of this variation in volume of individual exhaust beats. Locomotive timing was (and still is) a black art. A skilled valve setter was a valued employee. (A skilled irish setter will fetch you a Guiness.)

Under these scenarios, the frequency of the chuffs (i.e, how far apart they are) would still be virtually even. Some of the newer sound systems replicate this by emphasizing every 4th beat of the exhaust, and the effect is quite nice.

When the "out of square" of the valve gear gets to an extreme level due to excessive wear or slippage, the exhaust beats become slightly irregular in timing as well as volume. This happens because the valves open earlier or later than ideal, changing when the steam is allowed through the cylinders relative to the position of the rods. This would sound something akin to "chu-CHUFF chuff chuff," (or some variation thereof) where two valve events would be closer together in time than the others. When this happens, the locomotive is termed "lame." Engineers were trained to listen to the exhaust beats of their locomotives, and if they noticed any such irregularities, to report it to the roundhouse foreman for inspection and realignment if necessary. A "lame" locomotive was said to run anywhere from 10% to 18% less efficiently than a properly timed locomotive. Locomotives did run lame, but such conditions would have been cause for concern. In modern equivalent, it would be akin to your car engine missing. It will get you to where you need to go, but plan on taking it to a garage soon.

The optical sensors on the K-27 have a varying degree of slop in them, to where the tabs are most likely slightly off-center right out of the box. If hooked up to a sound system without adjustment, this would replicate the chuff of a "lame" locomotive.

There are differing opinions as to how common a lame locomotive would have been out on the mainline. The sound would indeed be prototypical, but whether every locomotive ran with such irregularities, or just the occasional loco every now and then is subject to debate. Much would depend on the railroad. A backwoods railroad without much maintenance might not be as on top of things as would a larger railroad, but presumably the locomotives would be less used, and easier on the moving parts. At the same time, the larger railroad would work the locomotives harder, subjecting the valve gear to a bit more stress, potentially wearing the bushings more quickly than their shoestring counterparts, but be in a far better position to maintain them to proper standards.

In terms of the model, it's likely going to be uneven straight out of the box, so your locomotive will be running lame. (Reports indicate each locomotive is slightly different.) If you want the chuffs to represent a well-timed (or slightly out of square) locomotive, then you need to adjust the tabs on the optical sensors to where the chuffs are more even. In an ideal world, perhaps the situation would be reversed, but like real locomotive valve timing, the difference between ideal and real world is stark.

Later,

K

Source: Basic Steam Locomotive Maintenance D.C. Buell; Rail Heritage Publications (Simmons-Boardman 1980) pp. 267 - 273. Originally written sometime in the 30s, this was a textbook used to train engineers, firemen, and other railroad employees about steam locomotives.