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Cam install on 4-8-4 Northern

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JRP
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Cam install on 4-8-4 Northern
Posted by JRP on Sunday, April 27, 2008 2:48 PM

I have a new HO 4-8-4 Northern that came with DCC.  I have just installed a sound decoder to go along with it, but also want to get the "chuff" sound in sync with the cylinders.  I purchased a Sound Trax cam kit and it calls for the cam to be "slipped onto the axle with the insulated side of the cam facing the drive wheel".

My question is this:  Because all 8 large drive wheels on this loco each have a thin copper connector for power, how will this affect the cam that needs to be electronically connected to the axle?  Will the copper connector cause the cam to not operate?

Does my question make any sense? 

Thanks. 

JRP  "Great Southwest and Pacific RR" 

 

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Posted by richg1998 on Sunday, April 27, 2008 3:42 PM

If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.

JRP
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Posted by JRP on Monday, April 28, 2008 9:38 AM

Rich,

Thanks.  I do have most of this information, although not the new Tsunami version, so I ran some copies off.  But have you installed a cam on a Bachmann 4-8-4?  I'm just not sure how the electric pick-up clip (on each wheel) will effect the cam operation.  Also, finding a place for the cam wiper is tough. 

JRP

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Posted by river_eagle on Monday, April 28, 2008 12:53 PM

Have you considered putting the cam on one of the tender wheels?

the tender wheel is roughly half the diameter of the drivers, so a cam with two contacts instead of four will give you the four chuff per revolution, as it will rotate twice for each single turn of the driver.

The timing won't be exact, but better and smoother than any auto chuff settings, and will make the installing of the wiper easier, as there is far more room under the tender truck.

 

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Posted by locoworks on Monday, April 28, 2008 3:50 PM
 the idea of using a cam is to get accurate 'chuffs', so using an almost correct tender wheel defeats the purpose of the cam?? 
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Posted by richg1998 on Monday, April 28, 2008 6:04 PM
 JRP wrote:

Rich,

Thanks.  I do have most of this information, although not the new Tsunami version, so I ran some copies off.  But have you installed a cam on a Bachmann 4-8-4?  I'm just not sure how the electric pick-up clip (on each wheel) will effect the cam operation.  Also, finding a place for the cam wiper is tough. 

JRP

Yes, it can be tough on mounting a pickup. I have not done it yet but I am studying the project.  This is from Bruce at Litchfield. Pay attention to the proper location for the insulating disc. Some geezer for sure will mention the sync is not correct.

When the CHUFF wire sees rail voltage, a chuff sound is created. The
cam connects the wiper to rail power as many times per revolution as the
chuffs needed - usually 4. The "rivet counters" align the cam on the
quarters of the drivers so that the chuff sound is EXACTLY aligned with
the driver rotation.
https://secure.ztccontrols.co.uk/pdf%5Csound.pdf
http://caseyjones1950.piczo.com/?g=26449972&cr=1&linkvar=000044#
The one below, scroll down the page until you come to the upside down loco. You can see one 
persons idea. The white wire connects to the chuff wire. Each time the chuff wiper hits the metal wheel, 
there will be a chuff. He uses a thin piece of copper clad PC board attached to the loco base. You can 
see his insulating disc.Contacts are soldered to the PC board. Some for rail pickup and one for chuff 
sync. Your loco already has rail pickup. You only need the chuff sync. I use very small diameter
phosphor bronze wire for pickups. It is springy. You also only need #30 flexible stranded wire.
http://www.pacificcoastairlinerr.com/1879/locomotives/ihc_sound/
 Rich
 

 

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Posted by river_eagle on Monday, April 28, 2008 10:35 PM

 locoworks wrote:
 the idea of using a cam is to get accurate 'chuffs', so using an almost correct tender wheel defeats the purpose of the cam?? 

This loco uses pickups that ride along the backside of the flange, which is the same place that the cam wiper needs to be, so the cam would also disrupt track power the pick up as well.

The cam also needs track power, which it would normally get by attaching the cam hub to the axle, but since all track power is in the tire/flange, and not transfered by the axle to the chassis, the cam will also have to electricly connected to the flange, not a good situation here either.

There is almost zero clearence under the chassis or behind the driver to mount the cam wiper, so you will need some creative engineering to get it mounted.

The tender wheel option solves all these problems, plenty of clear air, for wiper mount, power pickups are not in the way, and the entire wheel is hot for cam powering.I have enven used copper foil strips on the tender wheel nylon axle as a cam, making the wiper setup exactly as if it were for power pick up on a hot axle.

 

As to the "almost" factor, the math is as follows, if for example the driver is 68" and the tender wheel is 33" then the distance traveled for one revolition of the driver is 213.62", and the tender wheel is 207.34" per two revs for a difference of 6.33".  That works out to being off roughly two chuffs per 33 revs of the driver.

Motion based triggering is definatly better and smoother than the auto chuff, which never seems to be right on, either starting too soon or ending too late. 

When in doubt, rule #1 applies  Central Missouri Railroad Association cmrraclub.com
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Posted by richg1998 on Tuesday, April 29, 2008 12:02 AM

My answer is based on my DCC Spectrum and Roundhosue steamers. The drivers are insulated from the frames. I believe most DCC steamer have the same situation. There is about 5mm of space. between the bottom of the engines and the rail tops with the 65 inch drivers. The 51 inch drivers there is about 2.5mm space. I have copper clad PC board 0.7mm and 1.8mm thick that will work very nicely as I described before. Please note, the copper layer is on a thin piece of fibergalss so the copper side is insulated from the frame. One of the links shows how someone did this with an old 4-4-0 steamer. The pickup will not disrupt track power. The wiper has to contact driver wheel for track power to get a chuff. All my locos will have no problem with the pickup wipers since those wipers are out of the way between the frame and driver. There are people doing this now.

I have an advantage as I have been a machine mechanic for many years. This is just a much smaller scale job. Your mileage may vary.

Rich 

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Posted by HEdward on Friday, May 2, 2008 1:42 PM
 davidmbedard wrote:

Have you considered using 4 magnets on the driver axle with a reedswitch?

David B

I'm not a steam model expert, but I don't think there's room for any reed switches that I'm familiar with.  How about metal paint across an axel.  One continuous band and four lines along the axel with copper strips for pickups? 

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Posted by gandydancer19 on Friday, May 2, 2008 6:03 PM

I wasn't going to read this thread, but I am glad I did. 

I like the idea of putting the wiper on the tender wheels.  I may have to look in to that for my new 2-4-4-2 logging Mallette (sp?).  I have the chuff rate set by the decoder and it is off more than I would like.

Elmer.

The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.

(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.

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Posted by UpNorth on Friday, May 2, 2008 11:47 PM

I was running an OHM meter on my Bachmann and IHC locos. The drivers on the loco are isolated from the axels and from each other (opposite side driver).  All drivers pickup power, contrary to the tender were most power pickup is from one side per truck. That is the case for my Bachmann and IHC locos. 

The only difference with these and the  4-8-4 Northern (as per Bachmann parts diagram) is the tender has all wheel pickup. The drivers and wheels (engine/tender) are all isolated from the axels.

So I do not see what soldering the cam to the axel  of the drivers (as per Soundtraxx ) will bring. It won't be powered and you run the risk of melting the isolation between driver/axel or worse, causing wobble.  

A disk of thin plastic/nylon with 4 perforations in it should be all that is needed for the chuff contact wire to get power from one driver. Use one of the three screws on bottom frame to hold the contact wire. This should be possible and would have little effect on the power pickup of the decoder itself.

I would not run the risk of soldering or heating the axel at all.   

The magnet/reed switch solution is more for larger scales. Soundtraxx has examples.

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Posted by WP 3020 on Sunday, May 4, 2008 9:22 AM
 river_eagle wrote:

 locoworks wrote:
 the idea of using a cam is to get accurate 'chuffs', so using an almost correct tender wheel defeats the purpose of the cam?? 

This loco uses pickups that ride along the backside of the flange, which is the same place that the cam wiper needs to be, so the cam would also disrupt track power the pick up as well.

The cam also needs track power, which it would normally get by attaching the cam hub to the axle, but since all track power is in the tire/flange, and not transfered by the axle to the chassis, the cam will also have to electricly connected to the flange, not a good situation here either.

There is almost zero clearence under the chassis or behind the driver to mount the cam wiper, so you will need some creative engineering to get it mounted.

The tender wheel option solves all these problems, plenty of clear air, for wiper mount, power pickups are not in the way, and the entire wheel is hot for cam powering.I have enven used copper foil strips on the tender wheel nylon axle as a cam, making the wiper setup exactly as if it were for power pick up on a hot axle.

 

As to the "almost" factor, the math is as follows, if for eaxmple the driver is 68" and the tender wheel is 33" then the distance traveled for one revolition of the driver is 213.62", and the tender wheel is 207.34" per two revs for a difference of 6.33".  That works out to bieng off roughly two chuffs per 33 revs of the driver.

Motion based triggering is definatly better and smoother than the auto chuff, which never seems to be right on, either starting too soon or ending too late. 

The real factor is, what's on paper does not always equal what's in the real world. In the real world, the "almost" factor is almost + almost = nowhere near, or inaccurate X inaccurate = inaccurate. Are the tender truck wheels in fact 33"? They are more likely to be 36" (most 4-8-4 tender truck wheels are 36"). On "paper" the driving wheels may travel the same distance down the rail as the tender truck wheels. The most direct connection between the drivers and the tender truck wheels is the rail. In the real world the friction between the drivers, tender wheels and rails is not a constant because of curvature, grades, adhesion etc. When driver wheels rotate they may push and pull other wheels indirectly connected to them. I say "may" because drivers often will slip or spin when the other wheels don't. The point of having sound is so our locomotive models might be more realistic and therefore more enjoyable. IMO I think it would be much more realistic if a I saw a model locomotive's drivers slip a revolution or three that I would also hear a rapid "CHUFF Chuff chuffchuff chuff chuff". Such a sound is often heard with such an occurrence and is usually synchronized with the rotation of the drivers unless the cam was installed on wheels not rotating like the drivers. If someone noticed that the drivers were spinning and the chuff remained silent would they be a "nitpicker" or "rivet counter"?

  I do not know locoworks, but I think he is wanting to get a more accurate synchronized chuff than what the automatic chuff option on the decoder. A more direct link with the drivers, if you will. I don't think he wants to go through all the waste and bother stringing wires for a cam on a tender truck axle just to get more or less the same effect than he already has. He may as well put the cam on freight or passenger car axle. why not just install one on a trailing or leading truck axle? I'm pretty sure they are a lot closer. But if he were to do that he would still have the same nonsynchronized faults as with the tender application.

 I too would like to know how a cam could be installed relatively easily in one of these or other locos. It would be nice if the mfg/s would engineer a cam or a space for one. On of the problems I can foresee with an electrical wiper/cam is the it collecting dirt and loosing contact. It might be easier to install some magnet/read switch or hall effect detector gizmo in the cylinder area connected with the piston rods.

Railroads are "a device of Satan to lead immortal souls to hell." - an Ohio school board, 1831 - quoted in CTC Board 8/05 "If you ever wonder how you have freedom... Think, a veteran!!!" - My thought 1/08 Hey man, I don't have to try to remember the 60's... I lived too close to Eugene, Oregon.
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Posted by river_eagle on Sunday, May 4, 2008 11:54 AM

The real factor is, what's on paper does not always equal what's in the real world. In the real world, the "almost" factor is almost + almost = nowhere near, or inaccurate X inaccurate = inaccurate. Are the tender truck wheels in fact 33"? They are more likely to be 36" (most 4-8-4 tender truck wheels are 36").

they may be 36" and the drivers may be 72" i have not put a ruler up to them, the sizes used were for example only, if we use yours, for a 68" driver, and 36" tender wheel, it's even closer, only one chuff per 20 revs, and the 36/72 is a direct 2:1

 On "paper" the driving wheels may travel the same distance down the rail as the tender truck wheels. The most direct connection between the drivers and the tender truck wheels is the rail. In the real world the friction between the drivers, tender wheels and rails is not a constant because of curvature, grades, adhesion etc. When driver wheels rotate they may push and pull other wheels indirectly connected to them. I say "may" because drivers often will slip or spin when the other wheels don't. The point of having sound is so our locomotive models might be more realistic and therefore more enjoyable. IMO I think it would be much more realistic if a I saw a model locomotive's drivers slip a revolution or three that I would also hear a rapid "CHUFF Chuff chuffchuff chuff chuff". Such a sound is often heard with such an occurrence and is usually synchronized with the rotation of the drivers unless the cam was installed on wheels not rotating like the drivers. If someone noticed that the drivers were spinning and the chuff remained silent would they be a "nitpicker" or "rivet counter"?

 if your drivers are "often" slipping and spinning, there are more pressing issues than out of sync chuff

  I do not know locoworks, but I think he is wanting to get a more accurate synchronized chuff than what the automatic chuff option on the decoder. A more direct link with the drivers, if you will. I don't think he wants to go through all the waste and bother stringing wires for a cam on a tender truck axle just to get more or less the same effect than he already has.

decoder is allready in the tender, you are actually "stringing extra wires" to install on driver.

  He may as well put the cam on freight or passenger car axle. why not just install one on a trailing or leading truck axle? I'm pretty sure they are a lot closer. But if he were to do that he would still have the same nonsynchronized faults as with the tender application.

that could be an option if needed.

 I too would like to know how a cam could be installed relatively easily in one of these or other locos. It would be nice if the mfg/s would engineer a cam or a space for one. On of the problems I can foresee with an electrical wiper/cam is the it collecting dirt and loosing contact. It might be easier to install some magnet/read switch or hall effect detector gizmo in the cylinder area connected with the piston rods.

You seemed to have missed the entire point, so let me recap.

1. There is no arguement that the best place for the cam is the driver, but that isn't always possible to locate it there.

2. the design of the drivers and pickups of "this" loco, makes the driver installed cam at least a "7"  for difficulty, while the tender wheels are live and the room is there for easier install.

3. the tender wheel option is just that, an option for when a driver can't be used, you want your chuffs to be motion based, and not an electronic guess.

using a tender cam, by the way, it's not even mine, large scale locos have been using it for years.

 

 

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Posted by locoworks on Sunday, May 4, 2008 1:49 PM
without quoting from here and there, i was thinking that the original poster wanted an accurate 'chuff' rate for wheel rotation, not a nearly accurate chuff. even if the tender wheel is almost correct, the actual chuff will get further out of sync ( before or after ) the correct moment it should be 'chuffing'. it will at some point be 'chuffing' in the middle of when the driver/piston rod possition says it should be chuffing. it will of course get closer again until the drivers become in sync with the tender wheels so the chuff is where it should be.  in reality it will be out of sync far more than in sync with the drivers!!. as said else where if the drivers slip this too will not be chuffed along in time to!!  the only accurate way to get chuffs in sync is to take the chuff signal from the drivers.  now without going down the route of discs behind wheels with wipers etc the magnet and reed switch option is ideal, you can get reed switches almost grain of wheat bulb size so space should not be an issue. without any knowledge of the loco in question or pictures ( post some please someone?? ) it is hard to say what could fit where. i'm thinking that 4 little magnets could be glued to the side of the wormwheel on the drive axle, or even a balsa disc glued around an empty loco axle. another option could be to use an optical sensor which might require nothing more than 4 spots of paint on the back of a driver and an appropriate electronic circuit to trigger the decoder. there are bound to be other options.  aslong as you are happy with the results thats all that matters, but in my oppinion the tender wheel option is probably the most inaccurate system available. even if the wheels were exactly half the driver diameter they would not stay in sync with the driver/piston rod possition despite giving the correct timing for the distance travelled and wheel slip on the loco would not give the relevant chuffs like driver mounted sensors would.
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Posted by WP 3020 on Monday, May 5, 2008 7:17 AM

Well put locoworks.

 river_eagle, you are correct that if my locomotive constantly slipping and spinning excesivly, there are much greater problems than sound synchronization. However, it is a fact that a, prototype or model, (more often a model) Locomotive's drivers will slip a little from time to time when applying tractive effort. Evidence to this fact is why prototype locomotives have sanding equipment. A model locomotive's drivers are more apt to slip than any other free rolling wheels in its train during movement. All the wheels of a train do not neccasarily fallow the same exact path down the track. With all of those factors combined in normal operation is the reason why a cam installed on any axles besides the driving axles of the loco's is sooner or later going to get out of sync. Even if the tender trucks have the same size of wheel as the drivers they wouldn't stay in sync with each other. Just like two automobiles of the same make with their turn indicators (turn signals) flashing. They may be close for a while but soon you'll see that one light will be on while the other isn't. Didn't somebody say, "A stopped clock is right twice a day. But a clock that runs either fast or slow is never right."? I'm just imagining what a royal P.I.A. it would be to constantly have to spin the wheel on a tender to get it back in sync with the drivers. I'd rather have the chuff rate done by the decoder than go through all the extra bother of installing a cam on something that may never be in sync with the drivers and then constantly have to fiddle with it again and again and again....  I live in a relatively wet climate and don't see many folks bothering to build mud houses to live in around here. Why turn around and walk most of the way around a city block when you could walk ahead a much shorter distance and arrive at the same destination? Call me lazy, but I'd rather skip the site seeing long trip. Build it right the first time and not only will they come.... They will also be impressed and you will be appreciated!

Railroads are "a device of Satan to lead immortal souls to hell." - an Ohio school board, 1831 - quoted in CTC Board 8/05 "If you ever wonder how you have freedom... Think, a veteran!!!" - My thought 1/08 Hey man, I don't have to try to remember the 60's... I lived too close to Eugene, Oregon.

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