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MTH HO Allegheny re-gearing

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MTH HO Allegheny re-gearing
Posted by Shades_10318 on Sunday, January 26, 2020 2:33 PM

I have been recently working on an MTH HO scale model Allegheny. It mostly works pretty well, but there is just one problem I have with it- it is limited to its prototypical top speed by gearing and motor speed. I would like to be able to get it to run faster for the purpose of being able to speed match it with the rest of the locomotives in the roster. However, when I try to do this, even using the custom speed table settings, I can only actually get it to speed match up to speed step 23. After that, any other locomotives will outpace it. 

 

Any advice on how to speed up this locomotive would be appreciated. I have considered re-gearing, re-motoring, or maybe adding a boost converter to increase the input voltage to the motor control circuitry. None of those seem like great ideas, but replacing the motor would be my first idea if I could find out how to find one that will match the size but outpace it in speed. I have also disassembled the locomotive to look at the gearing, and as I understand it the main gear reduction is in the worm gears, so maybe there would be a way to replace the worm gears with ones with a different ratio. I'm not really sure.

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Posted by ATLANTIC CENTRAL on Sunday, January 26, 2020 3:45 PM

OK, here is a thought or two........

What other locos are we speed matching to? Why is a top speed beyond 65 or 70 smph necessary for a loco like this?

I assume from thatyou are using DCC? MTH DCS decoders, that are also DCC (more or less) are known to have some limitations in DCC. Thismight be one of them.

What voltage are you running yor DCC system on? DCS decoders like higher voltages, as noted by all the complaints when people try to run MTH HO locos on DC......

First idea, sell the MTH Allegheny, buy the finer detailed Hornby/Rivarossi Allegheny, and see if you don't have better luck.

OR

Rip out the DCS decoder and install the DCC decoder of your choice in the MTH Allegheny. Then the decoder won't be needing as much voltage and the motor will likely get more..........

One last thought, while I know enough about DCC, I'm a DC modeler. And I double and tripple head steam locos of different brands and wheel arrangements all the time.........with no speed matching.

If locos have similar starting voltages, and the train weight justifies multiple locos, the gearing and speed range only needs to be "close", they will work just fine.

Sheldon

 

    

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Posted by Shades_10318 on Sunday, January 26, 2020 5:45 PM

Thank you for your reply. The locomotives are being speed matched to a BLI E7 (the "golden locomotive"). The Allegheny only has a top speed of 50 smph, if the reviews are to be believed. I don't have access to a scale speedometer, but it is definitely slow relative to the other locomotives.

That's a good point about using a different decoder brand than the MTH one. It hadn't occurred to me. I'm not sure if the issue is actually with the decoder or the motor, though.

I do own a Rivarossi Allegheny as well, unfortunately I have found it to have issues with durability as well as the number of power pickups.

Yes, this is running on DCC. I wonder if anyone has done testing to determine whether it's the motors or the decoders that make the MTH locomotives run better at higher voltages...

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Posted by ATLANTIC CENTRAL on Sunday, January 26, 2020 6:21 PM

OK, not sure why an Allegheny would be running at 70 with an E7, but it is your railroad. What is "golden" about an E7?

The real Allegheny was designed to pull 5,000 ton at 45-50 mph, likely could have achieved 70 or close to it. They did pull troop trains and mail trains from time to time and likely did see speeds in the 60's.

Here is what you need to know about MTH, their DCS system was designed for O Gauge and then adapted to HO. They even lobbied the NMRA to change the wording of the DC voltage standards to "fit" their products. They run better on a slightly higher standing track voltage than normally recommended for HO DCC.

A true DCC decoder would give that motor a fighting chance to run a little faster.......and no decoder and 14 volts DC would likely make it fly.........

MTH has a long history of thinking they know better than the rst of the industry.

You may be having issues with the Rivarossi product, but trust me, MTH is not immune from product problems, electrical ones in particular.........

I for one will never own one of their locos because they don't run well on DC, and the DC throttles I use may not even work with their tri-mode DCS decoder. And I'm not paying their crazy high prices to then have to remove the decoder and rewire the loco.

My Rivarossi Allegheny runs just fine, and a number of my friends have them as well with no issues........

Sheldon  

    

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Posted by Shades_10318 on Sunday, January 26, 2020 6:31 PM

If you'd like a bit of context regarding the speed matching, I probably wouldn't run it with the E7, but the rest of the locomotives are speed matched with it, and I would like it to be able to be able to run with the other locomotives in the roster that would actually make a bit more sense. The issue I run into is that it can't run fast enough to keep up with the other locomotives at top speed, and I don't want anyone who would run it to need to remember to keep it at speed step 23 or lower to not have the other locomotives suddenly start running much faster than it. I realize that it's more prototypical to have it running slower, but it's more of a safety thing.

 

You think the issue is that there's too much voltage drop between the track power and the motor when running on 14V DCC then? I could try testing it with a voltage meter sometime soon to find out about that.

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Posted by ATLANTIC CENTRAL on Sunday, January 26, 2020 6:44 PM

Shades_10318

 

You think the issue is that there's too much voltage drop between the track power and the motor when running on 14V DCC then? I could try testing it with a voltage meter sometime soon to find out about that.

 

Yes, that's exactly what I think.

Sheldon

    

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Posted by selector on Sunday, January 26, 2020 6:50 PM

As you must know, the decoder metes out voltage rectified to DC based on your throttle inputs.  I can't speak from personal testing or other experience, but I am going by tests our hosts performed on HO locomotives proffered by MTH years ago (it may have improved since the 2010 era?), and they remarked every single time that their MTH sample needed a bear's breakfast worth of voltage to get underway.  That suggests to me that the maximum a DCS decoder is going to throughput to the can motor is something near 85-90% of what a DCC system would offer it.  So, your very nice Allegheny is speed limited by voltage, and I think you should probably convince yourself that that's the way the MTH H-8 runs.  They were not designed for passenger speed, but intended to match the Class A and 2-8-8-4 variants which were intended for similar 'fast' freight speeds...near 60 mph-ish.  You're almost there.  An H-8 paired with diesels isn't out of order, what what is its role, as a helper or as the head-end power for the consist?  If you have to couple ANYTHING to an H-8, it is going to be as an assist, and that's very unlikely.  Instead, you're putting an H-8 into helper service to keep a passenger train on schedule...the H-8's schedule, which is it's speed as a designated head-end locomotive on the consist...if you follow.  Run it at max for that drive and decoder, and let the diesels be helpers, or simulate the diesels with their combined 2600 hp needing the Brute to help a heavy consist get up the grade as fast as the Allegheny can get it there.

My two cents, but you gotta be happy in the end.  I'd say regearing is going to be horribly more involved than just ditching the DCS electrics and wiring in a TCS or something.

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Posted by ATLANTIC CENTRAL on Sunday, January 26, 2020 7:15 PM

Shades,

One last thought, or a few questions?

How many locos do you have?

Why do you feel it necessary to speed match them all the same?

As explained above, I run all sorts of multi loco lashups in DC with no speed matching.....it works fine.

Safety? "what do you think is going happen?" to quote my 8 year old grandson as he drives the battery powered four wheeler around the swimming pool? Guess what?, nothing bad happened.......

I have 140 powered units on my layout. I can't even imagine trying to speed match them all the same.........

Sheldon  

    

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Posted by rrinker on Sunday, January 26, 2020 7:41 PM

 The only thing is that not only is the DCS completely different than a DCC decoder, MTH also wires the lights completely backwards. So there's a bit more involved than just taking out the electronics and putting in a standard DCC decoder, if you still want the lights to all work. DCC uses a positive common, DCS is all wired negative common.

 I don't think there is a problem hitting the top speed on DCC track. On DC though, the MTH locos don't seem to reach top speed until 18V, far in excess of the NMTA standard of 12 volts.

                             --Randy

                                                                                                                                                                                                                                                                                                                                                                                         


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Posted by Shades_10318 on Sunday, January 26, 2020 7:44 PM

They're not all my locomotives, it's a local railroad museum and I'm currently in the process of speed matching as many of the locomotives there as possible for ease of use when running trains.

The thing I'm concerned about with running the Allegheny with other locomotives is that the top speed is much slower than the other locomotives, and I don't want to worry about excessive wear on the components of any of the locomotives in the consist. I guess if it ends up being my only option I could just speed match the 2 Alleghenys, but I would like to be able to run either of them together with the other C&O motive power we have on hand.

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Posted by RR_Mel on Sunday, January 26, 2020 8:43 PM

I have no knowledge of MTH but maybe a different approach will work.  Do you know the gear ratio or the motor RPM?
 
I higher RPM motor could work.  That might solve your problem.  The norm is between 5400RPM and 7000RPM with the exception of Athearn which are over 10000RPM, all at 12vdc.
 
I’ve been using the Mabuchi SF-266SA motors that are 7000RPM no load and operate well at 6000RPM under load.  I have a couple of Mabuchi FK-280SA 14200 motors that are listed at 12000RPM.  The specs on the FK-280 look pretty good, twice as much torque as the Athearn at lower current.  The FK-280 is slightly smaller than the Athearn motor.
 
 
Mel
 
 
 
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Posted by Shades_10318 on Sunday, January 26, 2020 9:16 PM

Thank you for the suggestion, Mel. I would be interested in trying out a different motor. I'm not sure about the motor RPMs/volt or the gearing ratio, although there are 2 gears in the gear tower and they are 22 and 26 teeth, I think, and the worm gear has a much higher number of teeth than the usual design. I'll have to measure the dimensions of the motor to see if it's the same as (or close enough to) the Mabuchi 280 motor you mentioned. It will have to be a motor with mounting holes on one end, as it has a tachometer board attached to it. A higher number of RPMs/volt than the usual ones used would probably be a good idea for a higher top speed ceiling.

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Posted by doctorwayne on Sunday, January 26, 2020 9:43 PM

I don't know if it would be appropriate for your museum's display, but I'd instead re-programme the other locos to match the speed of the Allegheny.

I've seen otherwise nicely-done layouts where the operator runs at inappropriately high speeds, to the detriment of the viewing to layout, as it makes it seem toy-like.

Like Sheldon, my layout is DC, and because of the many curves and grades, most of my trains (all steam) are doubleheaded, and often with pushers, too.  There's no need for speed matching, and no need for high speeds, either.  The highest posted speed limit is 45mph, but with most of the layout at less than that. 

It does, of course, suit the layout's features, which may be quite different than your situation.

Wayne

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Posted by RR_Mel on Sunday, January 26, 2020 10:19 PM

Shades_10318

 it has a tachometer board attached to it.

 

If you could figure out the gear ratio that would help a lot.   
 
You say it has a Tachometer, can you determine the motor RPM?
 
One or the other would be a great help.  Maybe contact MTH.
 
The info on the MTH site says the motor can safely run on 24vdc for increased speed.
 
Is there a number on the motor?
 
 
Mel
 
 
 
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Posted by rrinker on Monday, January 27, 2020 7:03 AM

 I'm not sure just swapping the motor would do much - the MTH electronics use that tacho input to set the speed to an actual speed - with a DCS controller you tell the loco to move at 10mph, not speed step 10. It's also used to sync the chuffs and the puffing smoke.

 The MTH locos use higher voltage motors and are geared as they are because there's no difference between the O scale DCS and HO DCS< track voltage is the same, so they took the simple expedient of using a higher voltage motor in the HO models so it works without having to have a scale selector on the DCS equipment.

                              --Randy


Modeling the Reading Railroad in the 1950's

 

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Posted by RR_Mel on Monday, January 27, 2020 8:20 AM

rrinker

 I'm not sure just swapping the motor would do much - the MTH electronics use that tacho input to set the speed to an actual speed - with a DCS controller you tell the loco to move at 10mph, not speed step 10. It's also used to sync the chuffs and the puffing smoke.

 The MTH locos use higher voltage motors and are geared as they are because there's no difference between the O scale DCS and HO DCS< track voltage is the same, so they took the simple expedient of using a higher voltage motor in the HO models so it works without having to have a scale selector on the DCS equipment.

                              --Randy

 

Ouch!!
 
So much for making that locomotive run faster.
 
 
 
Mel
 
 
 
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Posted by Shades_10318 on Monday, January 27, 2020 12:26 PM

So based on what everyone has said so far, it's looking like I may have to replace the motor and the decoder to get it to run faster? 

I've already reprogrammed the locomotive to run using the custom speed tables. I'm not sure how the decoder actually regulates the motor speed, although I would think that programming CV 5=255 would still allow the maximum motor speed regardless of what that translates to in smph, at least as long as it's running in the non-smph mode. I'm not sure if that fixes the issue with the decoder not allowing the locomotive to run faster with a faster motor. 

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Posted by RR_Mel on Monday, January 27, 2020 1:04 PM

From the info on the MPH site sorta saying the motor is 24 volt just replacing the decoder wouldn’t help, even with a different decoder the 24 volt motor would still be operating on half voltage.
 
So like you said changing both would be your best shot.  As Randy said it sounds like the tach is the problem. 
 
 
Mel
 
 
 
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Posted by Shades_10318 on Monday, January 27, 2020 2:09 PM

I just found out I have another locomotive that uses a Mabuchi FK-280SA-10350 as the drive motor. I guess I could just try and see if it will fit or not, then go from there.

 

I can also discuss with the other staff at the museum whether or not they would like to try slowing all the other locomotives down to a top speed of 50smph. We do have some faster passenger locomotives and some dual service ones though, so I'm not sure if that would work.

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Posted by rrinker on Monday, January 27, 2020 3:47 PM

 There's a reason I never bought another MTH HO loco after my FA set.....

I'm still not sure if I want to play the game and rip out the electronics and fix it all up with a standard DCC decoder, or just sell the things off (I did get them for a pretty good discount, so I might get close to my money back) and just find another P2K set which are just as nicely detailed. 

Way I see it, you have two choices. Just never MU the Allegheny with anything but another MTH loco, or use the slowest one as the new gold standard and adjust the rest all down.  Or take it back/resell it, and get something like a Rivarossi one and put a standard decoder in it.

 Just regearing might work - since the tach would read the same motor RPM but the loco would be going faster for a given motor RPM. Thus the electronics would think it's going 50, when it really is going 70 because of the different gearing. Forget trying to calculate that exactly, you just need something that gives a greater than 70mph top speed (you can always slow it down) while retaining enough power to pull a decent train - as you put faster gears in it, you are going to lose pulling power.

                                       --Randy


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Posted by RR_Mel on Monday, January 27, 2020 4:54 PM

If it was my engine I would rewire it for DC operation and run at 12vdc it to compare it to the Mabuchi motor and report back to let every one know what is going on.
 
There is a large unknown about Mabuchi motors, the FK-280 is found advertised with many different speeds from 4000RPM to 27000RPM.  The FK-280SA 14200 is listed at 12300RPM dual shaft.  The FK-280SA 20150 is listed at 12300RPM single shaft.  Locked rotator ranges from 1.4 amps to 4 amps on FK-280 motor.
 
I’ve spent hours on their web pages and the listed info is hard to find and varies all over the spectrum when I do find some.
 
When I receive the two FK-280SA 14200 motors I’ll do a full test on voltage, current and RPM and post the results.
 
 
 
Mel
 
 
 
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Posted by csxns on Monday, January 27, 2020 5:39 PM

rrinker
er, MTH also wires the lights completely backwards

You right their my five GE's when running foward the ditch lights on the of the back of the units lights up.

Russell

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Posted by rrinker on Monday, January 27, 2020 6:34 PM

 That's not what I meant. On a DCC decoder, the blue common wire is +, each of the function wires is the - side.

On MTH locos, the common connection is -, and each of the individual function wires is the + side. Since they often use small PCBs to mount multiple LEDs on, with independent control (say a high mount headlight with flanking number boards, where the headlight and the number boards are individually controllable), then on the PCB all the LEDs will have their - wired together and then there will be two + wires coming off the board. You can;t just hook that up to a DCC decoder - LEDs require the correct polarity. So you have to do things like cut traces to rewire the PCB to work with a DCC decoder if swapping out the MTH electronics. It makes the job much more difficult than it needs to be.

                                       --Randy

 


Modeling the Reading Railroad in the 1950's

 

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Posted by Shades_10318 on Monday, January 27, 2020 7:44 PM

OK, I've done some testing and I have more information now.

Originally, the locomotive was limited to 50smph and did not have enough torque to spin the drivers if held in place.

I connected the motor directly to the power pickups, ran it on up to 14 volts DC, and found that the motor now runs much faster, I think (I don't have a scale speedometer), and also has way more torque than before (enough to spin the drivers with the traction tires installed). 

So that's useful information, it would seem the issue is actually with the decoder limiting the voltage going to the motor and not actually the motor being too slow. Unfortunately that probably means I'll have to replace the decoder... I think a Loksound Select is the only one I've heard of that has support for the smoke unit.

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Posted by ATLANTIC CENTRAL on Monday, January 27, 2020 8:12 PM

Shades_10318

OK, I've done some testing and I have more information now.

Originally, the locomotive was limited to 50smph and did not have enough torque to spin the drivers if held in place.

I connected the motor directly to the power pickups, ran it on up to 14 volts DC, and found that the motor now runs much faster, I think (I don't have a scale speedometer), and also has way more torque than before (enough to spin the drivers with the traction tires installed). 

So that's useful information, it would seem the issue is actually with the decoder limiting the voltage going to the motor and not actually the motor being too slow. Unfortunately that probably means I'll have to replace the decoder... I think a Loksound Select is the only one I've heard of that has support for the smoke unit.

 

I thought so.........

Sheldon

    

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Posted by rrinker on Monday, January 27, 2020 9:04 PM

 You might want to hook the motor up to a decent motor only decoder, one that has BEMF, before you go all in. Why? Because with a BEMF decoder, you usually don;t get the full voltage at top speed. Why is that? Because if the decoder produced a full on pulse to drive the motor, and the load increased - more cars, or climbing a grade, there would be nothing left in reserve to maintain the speed and the loco would slow. By saving some of the top end, the decoder can speed up the motor by applying more power even at full throttle. You are likely to see this with any BEMF decoder.

 If this is a museum display - I wouldn;t even connect the smoke. If the loco runs the smoke unit dry, it will eventually overheat and burn out. SO unless the loco is always under supervised control and the operator rememberts to refill the smoke unit when it stops smoking, it should stay off. That's ignoring any other issues people have with smoke, like a residue settling over the layout.

 Even a non-BEMF decoder is going to not run as fast as applying 14V right to the motor - you don;t get 14V at the motor output of the decoder. 14 is about a common HO scale DCC setting, but the motor is controlled by an H bridge driver in the decoder, which puts 2x diode drops in the motor circuit, so the peak is about 1.4V less than the track voltage - less for the BEMF decoders because of the reserve.

                                         --Randy

 


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Posted by Shades_10318 on Tuesday, January 28, 2020 7:21 AM

At this point I'm actually thinking about just disconnecting the motor from the original decoder and connecting it to a separate decoder for only motor control. Since the MTH model uses a tachometer to read the motor speed, it should still be able to synchronize the chuffing and the smoke fan. Don't worry about the smoke unit, there's a dial in the tender that I use to turn it off completely when it's not being used. 

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Posted by RR_Mel on Tuesday, January 28, 2020 8:04 AM

I think you need to put a load on the motor leads on the MTH decoder so it thinks the motor is still there.  Measure the resistance of the motor and use bit higher resistance, if the motor measures 20Ω go with 47Ω or so.
 
 
 
Mel
 
 
 
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Posted by Redvdub1 on Tuesday, January 28, 2020 9:41 AM

With all due respect to the recommendations your respondents made...I would recommend you do nothing until you find out how many car loads slow down the E7 speed to match that of the unloaded Allegheny.  If it's a relatively "small" number like 4 and you will be running more than 4 cars when consisted you will be fine no matter what the car loading provided the faster locomotive (the E7) is on the point.  The consist will run just fine at <4 car loading but the slower locomotive will be acting as a "partial" load on the faster locomotive.  One key proviso...you must apply enough voltage (DC) or speed step setting (DCC) to get the drive wheels in both locomotives moving (rotating). 

I have done the above dozens of times without incident.  So have most "older" (aka experienced) DC only operators.  The faster locomotive first is a good rule but not absolutely critical...it just avoids the possibility of coupler "buckling" issues at relatively light loadings due to inter-loco compressive coupler forces. 

 

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Posted by Shades_10318 on Tuesday, January 28, 2020 10:24 AM

Thank you for the suggestions.

Mel, the resistor idea may be necessary, I'll have to find out if it will work without it or not. Regarding the value of the resistor, a motor is an inductive load, so the current will be equal to a resistor with the same value when first starting up (inrush current), but once the motor gets moving it drops dramatically, so the required current to actually trick the decoder into thinking the motor is attached is much lower. I would have to measure the free running current of the motor and go from there. I could use the load suggested, but that would draw more current than necessary and also generate more heat.

 

Red,

I appreciate the thought, but unfortunately the E7 is just the "golden locomotive" and not the one that would likely be run with the Allegheny. I could try and see what load it takes to slow down the other locomotives that I would like to run with it, but I would really prefer to be able to run it with any locomotive and any load, if that's going to work out. Personally, I think it's worth the effort to at least try swapping out the decoder if there's a good chance that it would work better that way. 

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