(Resolved, seemingly) Upgrading Two SD70MAC's for Double Heading

Man, this is me!

Just change the tape!

tach tape that is...

Which way would I change it? 

Cheryl,

Have you tried running them as a lashup, even disconnected?

If the two tach tapes have the same number of stripes, the two engines have same size drivers and the two engines have the same gear ratio, I would expect them to run at close to the game speed.

However, if the gear ratios or driver sizes are different, all bets are off.

If you want to slow the faster one down, you'd add stripes to that flywheel, and vice versa.

 When you did the upgrade, did you use the two different tapes for each flywheel size? or did you use the same tape on both?

 This may sound lame, I don't know the formulas that the pros use to match these. I'd get one engine running the correct speed that matches my fleet. It takes me a little extra because I just start with a guess and then add or subtract stripes using my computer and printer.

 I'd then fine tune the other one to match. It takes me a little longer and I waste some tape stripes. I fiddle with them until they're perfect. Sometimes I just color in a white stripe with a sharpie, to make a quick minor adjustment. You only notice that at super slow speed (1MPH). I can then, print out what I need, once I've determined the correct number of stripes.

 Once it's dialed in, it will stay for good.

Sure. You need to try stuff like that to correct the speed. It won't hurt. What I would do though, is get them to match known well working engines. That way you can make them in a consist with anything.

 So try each and determine if each one needs to go slower or faster.

Okey doakey   Will be tomorrow's project, watching my bb team win right now!! 

"One other thought I had was putting the 30mm tape on the 27mm fly wheel.  Any thoughts?"

I believe that will speed that engine up?? (It has to spin faster to read same number of stripes.)

 I like to pace the engine with a known correct one, and get an idea of how far off it is. When it's close in speed, it's easy to add (or subtract) a stripe or two.

 Make sure the reader has the correct spacing off the flywheel or it will skip some stripes and you'll be chasing your tail trying to fix this!

Ooops! Sorry. I like to chat!

Back w/ you tomorrow.

No worries, I can chat and watch the game, it's just that I can't test out the locs while watching the game and typing, lol.  Game is over and my team won!  Yeah!

Charly, Flywheel size doesnot matter as long as correct tach tape used. The number of stripes will be the same regardless.

I put a mark on top of the flywheel and also a wheel.  Rotate flywheel and count how many turns to get one revolution.  Do same for other engine.  Are they the same?

If not that is the issue.  IF they are, make sure tach reader gap is good, especially on the faster engine.   Make sure you used correct size tape on the flywheels.

G

3mm Diameter is 9.42 mm circumference. A few extra strips but the space between strips should be the same.

(1.) Flip the motors faster to slower/ slower to faster. You would determine if the worm gear ratios of the trucks are the same, if they fit and work properly.

(2.) You could change flywheels.  (Frank Timko)

I could be wrong and often.  Mike CT 

Mike,  Not for MTH, it expects a set number of stripes to indicate one revolution.  So a larger flywheel get larger spacing, but the same # of stripes as a smaller flywheel.

Need to find compare ratios first, then find out why one is faster, or slower.  G

Hey Charly

Why not see if you can just swap 2 of the motors , so you get a large flywheel and a small flywheel in each loco, then put the reader tape on the same size flywheel .

Problem solved , chances are the gear into the trucks are the same , just compare them carefully. The collar that is on the bottom of the can motor can be moved if ness. also .

This would seem easier than matching tapes . 

Also if you can swap the motors , with all electronics disconnected , once you move the motors use a DC transformer and temporarily wire the can motors to pick up power from the track , then run the locos and see if they run the same speed , one other cause may be one of the locos is broke in more , because it is older. If that is the case , then if both locos have the same side frames , swap out the truck and motor and see if you can get them to run at the same speed .

Already have established reader spacing on both engines, well within the MTH parameters, thanks! 

Proper tapes were used, measured fly wheel with a micrometer to be sure.  Have not checked rpm on fly wheels, will give that a go.  Thanks!!

Interesting thought, thanks for the reply!!

The connection speed at home sucks!!!  I am presently at the local Mickey D's to get updates and do some downloading etc..  It will be this evening before I can report back on any success/failure of all your great ideas.  Thanks again

It tells me that not only is the flywheel diameter different, but the gearing is too. They should take the same amount of turns.

 I would still pace them with known good engines to determine which one is correct (if any). Then, you could focus on the other one to correct it with a new tape.

Did a little more close examination and it would appear the motor is the wrong one for the engine, the front motor matches the two in the other engine.  Hmmmmmmmmm.  It would seem someone has been in the engine tinkering before!    I was given this engine used.  That would also explain some other problems this engine has had!!!

Square one!!

False alarm, both motors take 10+ turns to turn the truck wheels one rotation.  Sheeesh. 

I would Mark the flywheel and wheel on that front motor and see how many turns the motor turns to turn the wheel one turn. You would want the front and rear to be the same gear ratio. The Engine that spins 9+ compared to the one that is 10+ is going to be faster even if it had a 27mm flywheel with the same tach tape as the other engine.

Yup, yup, yup

Echo

People, other than Charly please read my post.  As with many things Fly wheel size does not matter, if the correct tach tape was used.  A 30mm flywheel motor with a 30mm tape will read the same to the PS-2 board as a 27mm flywheel with a 27mm tape.  They both will have 48 stripes.  When the reader counts 24 changes it know the motor turned one revolution.

Since Charly used the right size tape the flywheel is not the issue.

If the gear ratio is the same and the wheel dia are the same, then something else is up.  Either wrong sound file, bad sound file load, defective tach reader, dirty tape, mechanical binding on one engine.  Many other things, BUT NOT THE FLYWHEEL SIZE!

Joe advice about running with known engines that maintain SMPH is good.  Find the one that is not right and go from there.

So gear ratios are the same?  G

I'm out! 

put the tach on the other motor and see if it drags first the truck.

I was in the process of trying to figure out who would run with who when my DCS got HISSY!!!!  Need to recharge some batteries for the handheld and then I can proceed.  I did manage to determine the faster engine is faster than one of my others before things went south, but just one comparison doesn't fill me with a lot of confidence.  I wish the "out of RF range" message would time out in about 2 seconds so you could move on.  Oh well, se la gere.  Will post more results when I can

 I'm trying to hold my tongue on DCS issues because it just turns into a big rant. I am sick and tired of it. I'm trying the computer to see why my system has so many different hang-ups.

 The one great thing, is the computer system doesn't add engines. It reads the track and runs anything on it.

  For some reason, my outside remote won't add anymore. I have to get a new remote out there. It lost my custom made MP15AC in G scale. I can't live with that! I can't delete it. I can't re-add it. It works in the house with another DCS system. That has a brand new remote. I took that outside and tried to add another new engine and it locked up. The old remote added it smoothly? Must be some conflict thing. I just wish the remote would say something besides out of range when I'm right in front of the TIU. If I wire it up, it just stalls. UUUUUUUUUURRRRRRRRRRRRGGGGGGGGGGGGGG!

 Time to purge the system!

Which is why I am upstairs, playing solitaire, waiting for batteries to recharge.    I sympathize with your aggravation.  I think I'll go have some dinner now.  BBL

By 2:00am, after much gnashing of teeth and factory resets , it was decided to replace the tach tape on the faster engine.  The slower seemed to be in time with several other engines of similar ilk, so it was left as is. 

The tach tape that was replaced did have some wear and scuffing so was suspect.  With the new tape the engines are now running within inches of one another and maintaining a reasonably constant gap.

This, however does not resolve my confusion on the internal differences between the two engines.  Go figure.

For now, case closed

  Miss counting stripes due to a larger than normal gap, or a dirty/damaged tape is probably the top reasons for an engine too fast.

I did not mention tape condition because you were upgrading and I assumed you used new tapes.

The reason for a different flywheel was probably a substitute if the original motor was out of stock.  As long as motor size and gear specs are the same, a different flywheel won't matter much as long as it fits.  Older engines with 9mm thick flywheels usually wind up with 5mm thick flywheels now, etc....   G

 Cheryl, If you drink, have one on (for) me! Glad you got it.

I don't even bother with the shells anymore until it's running correctly.

I just counted around ten engines destined for my bench. I'm actually jealous that you did the SD70MACs that I want.

For some reason, I skipped a bunch to do my newest SD80MAC. Now I have to learn fully PS3 wiring and such for the others.

 I should just buy RTR 2 rail releases from now on. What fun would that be??? I believe deep down, I like the challenge! What's your excuse??

It is two fold...  One, the engines were given to me, so they were FREE!!  Two, I like to think that I know what I'm doing and am up to the challenge!  lol.