PS2 Tach Reader Gap?

If the gap is too wide, the sensor may start missing pulses and the engine will speed up.  At some point, it'll just run away.  Pretty much the same for too close.

One thing to be aware of, if the spacing on the stripes gets too small, the sensor will start having trouble reading them, there is a limit to how close the spacing can be and still have the sensor detect them.  This gets worse at higher motor speeds.

Why do you have to guess at the PS/2 characteristics?  The inputs to Dave's formula can be calculated from an existing locomotive.  You can do a test load of the sound file you want to use in the conversion to verify the speeds remain the same.  Most similar engines from the same product line, i.e. RailKing or Premier will have the same speed ratios.

John,

Hikels list doesn't contain every engine MTH made.  If MTH made one of their Ten-Wheelers close to scale, then the wheel diameter should be 68"-72", none of the engines on Hikels list use that diameter (1.417" = 68" wheel diameter).  Also, without the engine being on the list, I'm still guessing at what the gear ratio is.

I have emailed MTH asking for specs on one of their engines, no response.

I've downloaded 4-5 sound files and none have been THE ONE yet.  I have to disconnect my TIU and take it, a piece of test track, the power supply, a "workbench" (TV tray), cords, and the engine downstairs to my computer to do a download, then have to lack it all back upstairs and run it on the layout to see if the sound file is what I was looking for, not the easiest way to do things but it's all I've got at the moment.

The sound file I'm using now is very close as far as chuff goes, but the speed of the engine "appears" to be 1/2 to 1/3 of what it should be when the handheld is set to 30 smph.

What I'm saying is, most sound files for similar RailKing steamers for instance, should run at the same speed.  Same for the Premier line.

I've loaded three or four different sound files into a locomotive and gotten identical speeds, although the sounds were different.

So, if you have any PS/2 locomotive, you can load the sound file you want to use in the upgrade and see how fast it goes in relation to the speed setting.  A simple calculation should yield the difference between scale speed and what you're getting, if any.  Then you can use that information to properly determine the proper tape for your upgrade.  I've never seen one go 1/2 the scale speed or less in an upgrade, and I've upgraded Lionel, Williams, K-Line, and RMT stuff to PS/2.  Hard to imagine there's that much difference.

What exactly are you upgrading?

This last upgrade was using a Weaver G5 4-6-0 chassis/motor with:

Drivers - 68" (1.417")

Flywheel - .945"

Gear Ratio - 22:1

I plugged in the following for a known PS2 engine (can't recall which engine I used at this moment, but the gear ratio is a guess on my part):

Drivers - 73" (1.52")

Gear Ratio - 24:1

# stripes on tape - 48

It may be the size of the flywheel giving me problems, but it seems at one point I had good speed, but the chuffs were way off.  Now the chuffs are close but the speed is off.  I started with a tape of .074" stripes, followed by .057", then .062", then .054" as my last attempt in trying to get the speed right.  If I recall, the wider the stripe the faster the speed (wider stripes mean less stripes mean increase in speed?).

Problem is there's no extra room to increase the diameter of the flywheel, unless I start hacking details (leaf springs and/or brake rigging) off the chassis so the flywheel will clear.

I know I used sound file 20-3068-1 and presently have 20-3394-1 (a NYC 4-6-4!!!) in the engine.

I'll recheck the 4-6-0 and see how long (time) it takes to make the circuit (if the other engines are correct, it should be 1/3 of a mile).

I just timed 3 engines around the layout, measuring the route with the handheld I came up with .3 (1/3) of a mile.  I suppose this could be off a bit (would the indication still read .3 miles even though you're 1" away from it being .4 miles?).

I entered 30smph for all 3:

NW2 (original PS2) - 42 seconds to go the 1/3 loop - 28.5 smph

(I used this as the standard)

2-8-2 (PS2 upgrade) - 47 seconds - 25.5 smph

4-6-0 (PS2 upgrade) - 61 seconds - 19.6 smph

The 2-8-2 and the 4-6-0 both have the same motor and flywheel (different size drivers), but I was able to add double-sided tape to the 2-8-2 to increase the flywheel diameter to 27.5mm (1.09 inches).  The flywheel on the 4-6-0 is 24mm (.945 inches) and like I said, I can't easily add any double-sided tape to it because of interference.

Need to rest on this, not sure what to try next.

Bob,  I am not sure how the motor drive code is written wrt sound files.  Certainly they are built to specifics of the engine as far as driver size and gear ratio.  Knowing those 2 values one turn of the flywheel can be calculated to a specific scale distance.

One turn of the flywheel for MTH engines is 24 discrete counts.

Flywheel size only matters in calculations for custom strips.  I can replace a 27mm Fly wheel MTH motor with a 30mm fly wheel motor and the engine would have the same speed characteristics because the tach tape on both fly wheels have 24 black stripes, and one revolution is one revolution.

I would run your engines together on the layout set to the same speed.  You need to just add a stripe or 2 to the fast engine so that there are 25 or 26 black stripes until you can match speeds.   This tricks the processor into thinking the motor made a full revolution when it only made a 7/8 revolution for a given speed.  Effectively slowing down your engine.   I would just trial an error this.  G

I don't know how the remote handles the increments of the miles, it's not something I've spent any time tinkering with.  I just put the two engines on the track and use the ALL to set them to the same speed, that quickly tells me if the speeds are off.

How many strips do you have on the flywheel when you get the speed fairly close.  Given the different gear ratios, I'm guessing you may never be able to get both the speed and the chuff exact on an upgrade of a non-MTH locomotive.

What I don't understand is you changing the number of stripes significantly and it not having a corresponding change in speed.  I would expect, for instance, going from 40 stripes to 50 stripes would have a 20% speed reduction.  If you don't get those results, I'm at a loss as to what's happening.

George,

Thanks for sharing your knowledge of the tack reader tape. It's excellent notebook material for me.

I THINK I have the answer.

After I made all the calculations and put the tach tape on, I received the traction tires from George.  The tires INCREASED the wheel diameter by about a 1/16" (.060"), thereby increasing the circumference by more than 3/16".  Sounds small but it might have been enough to make the engine go slower.

What I'm going to do is (1) remove the tires, (2) use 2-faced tape to make the flywheel larger (I was able to remove the interfering detail), and (3) recalculate the tape.

The sound file I'm using came from 20-3394-1 (a NYC 4-6-2 and not a 4-6-4 as posted above), it has all the lights I wanted and a great sounding whistle.  I'll use the following parameters, not knowing how accurate they are for that engine:

wheel size - 79" (USRA heavy Pacific)

gear ratio - 24:1

tach tape - 48 stripes

I'll let you know how it turns out!

Increasing the diameter of the wheels would make the engine go faster, all other things being equal.

Your welcome Bobby.

Bob, you don't need to change the flywheel diameter just size the tape to increase or decrease the stripes as necessary.  G

George,

After fooling around with that "formula" I finally discarded it and started doing just what you say...try a tape until I find one that did the trick.

I did increase the flywheel diameter using 2-faced tape, but the formula still wasn't giving me a correct stripe width.  It's probably because I was still guessing at the PS2 data from a good KNOWN engine.

I started with stripes of .068" and increased it until I got to .109" at which point I could get the engine to match the speed of the NW2 at 30mph.  At this point all my PS2 engines (except the 2-8-2 which I'll work on shortly) will circle the 1/3 mile loop in 40 seconds (30mph).  I used .068, .075, .082, .090, .100, and finally .109.  I could see the speed starting to go in the right direction at .082, never thought I'd have to go all the way up to .109" wide stripes

Thanks to all who helped

(I bet I can change a tach tape in record time now )

Oh, I left the traction tires on the engine.

The weaver I did also needed to be sped up so I used the 31.8mm tape on the small flywheel and had to cut off a few of the stripes and that sped it right up, otherwise the big steamer was moving like a switcher.  I think the ratio was about 40 or 42 to 1.  G

I had a sheet of tapes that I printed out a few weeks ago when my printer was low on black ink, it made the black ink by using the color cartridges and came out gray/light black.  I tried using one of those tapes and the engine sped off like a race horse.  I remembered someone saying something about light/faded tapes so I reprinted a sheet which solved that issue.

The 2-8-2 is a bit slow but now I know how to fix it.