DCS & RS-385PH

There are many more variations too.  These motors can be custom built.  So not knowing where your motor came from, what gearing you are using, how you modified, what soundfile you are using, it would be difficult to help. 

MTH motors are closer to 12V ratings with thicker wire and less turns.  Like a -2655 G

You can get a good idea which motor would be closest to what you have by disconnecting a motor lead and measuring the armature resistance. Then go to the chart and check the stall current. eg the 12V motor has a stall current of 4 amps. Its armature resistance should read 3 ohms. The 24 volt motor has a stall current of 2.35 amps. It DC resistance should read just over 10 ohms.  While its true Mabuchi will custom wind motors I suspect to get quantity pricing the manufacturers will use one of these two. The hard part will be to find these motors with double ended shafts.

Its easy to find RS385s on the bay for a few bucks but rarely with dual shafts.

Pete

Pete, stall current must vary considerably among the models, if you look at the wire size and number of turns.  In the pictures at the various sources it is virtually impossible to ascertain if motors have dual shafts. 

GGG, I don't think soundfile would make a difference.  The guru, whose name I won't mention, compared it to the torque of a loco of his that has a motor from the same machine shop source, and found my torque was less than his.

I've e-mailed that source.

Thanks, Pete and George, for the comments.

SF matter, depending on gear ratio, especially if you have a mismatched motor.

I have found that measuring static resistance on motors is not always accurate.

Many motors will have the last 4 to 5 digits stamped on them.  At least the newer ones I have seen. 

Interesting so what was the calibrated equipment used to measure motor torque?

Don't tell me it was a tongue test

If in fact these are 24V motor that is part of your problem.  If the software is based on a 12V motor how it PWM the motor would be different then one that needs a high voltage to hit rated speed.  G

RJR, I take it your didn't buy the motor from MTH. If you have an MTH engine measure the armature resistence. Then measure the resistence of the motor that isn't working. If they are not within an ohm of each other you probably have a motor that won't work very well for this application.

Pete

No, Pete.  The loco is not MTH.  It is a 1950 Lionel Berkshire initially powered by what is now called the Pulmor motor.  Not being able to figure a reasonable way to apply a tach tape to it, I purchased, as a package, a DC motor mounted on the shaft holder assembly.   I did a similar upgrade on a 1954 Lionel Pulmor diesel switcher (the subject of a thread a few months ago), and it runs very well. 

GGG, what is especially interesting is that the RS-385PH motor is what MTH uses in its R-K diesels.  Given the variety of RS-395PHs I have come across in the Kysan catalog since the first post, that there's no way to be sure what version one has, or what voltage. 

   I, of course, have no way of telling how the catalog and data sheet authors determined what the torque was "at maximum efficiency."

    Where on the motors, did you see a stamped number?  All I have spotted was the label pasted on.

The more I dig into Mabuchi motors, the less I know.   There is also a variation in shaft sizes, which becomes an issue because of the machined coupler between motor and the work gear extension shaft (worm gear is about 2" from the motor and shaft is ball bearing supported.

The motors with paper tape usually don't have the extra data.  The newer versions have a silk screen part # and many have the full number.  RS385PH-2655 as an example.  Maybe your motor is damaged?  G

GGG, the 4-digit suffix doesn't comport with Mabuchi's numbering system as shown on its web site.  But, the Kysan catalog does show several motors with 4-digit suffixes.  It shows a RS-385SH-2655 as a 12-volt motor.  (S is a different magnet type).   Is the motor with the 2265 suffix from a loco?  Kysan says it's 12-volt.

RJR,

You're missing an important point about the Mabuchi motor specs, they are listed at a certain voltage. You need to look at a particular motor in the range(s) that you want to operate it in. Only then will the other parameters be useful.

Dave

No Dave, I haven't missed that point.  I'm very aware that motors bearing the designation RS-385PH come in a wide variety of voltages, torques, winding size, etc., all of which interplay, but, except with the more recent motors that GGG has encountered, there's apparently no way to tell what you're holding in your hand.  Going further, I haven't found any way, in any of the listings I've been able to discover, whether the shafts are double- or single-ended, nor have I been able to find any listing containing all of the parameters for every sub-model variation.  If you can find anything more, I'll be happy to see it.

I always thought it was just some generic number being used. I have seen it used in so many different applications, with different shafts and flywheels.

 I guessed that it was made per order. This post is interesting.

It's more than merely interesting when you've worked on an uipgrade, or fabricate replacement DC motors.  Attached is an extract from the Kysan catalog, showing some of the variations

RJR, I knew that you were aware of those points when I saw your listing of the model dash numbers. That isn't what I was referring to and realize that I may have been unclear.

Here are two of the motors, adjusted for operation at other than the specified voltage.

At 12V, and the load giving an ~ 1000 rpm, the:

-16140 shows .92 amps and 221 g-cm torque

-17120 shows 1.23 amps and 298 g-cm torque

Quite different than the 24v specs.

Also note that Mabuchi's stated operating range of the 16140 is 12-30 volts, the 17120 is 8-35 volts.

Dave

Thanks for the Kysan listing.

Dave

At slow speeds, the DCS system feeds 6 VDC or less to the motors.  If I apply 4.5VDC directly to a motor, the loco moves out at more than a crawl.

Judging from some google leads, Lionel may use the  -2655 12-volt for locos.

Are you saying that the problem motor runs better on the 4.5VDC than DCS?

Dave

No. I was just using this to illustrate that DCS runs the motors at surprisingly low voltages.  the 4.5VDC actually makes the loco run faster than it would at a 4 smph speed setting.

Your still miss apply the data.  PWM can be a high voltage for short duration so the effective voltage looks low.  The effect would be much different apply a low voltage for a slightly longer period.

Google identifying Mabuchi motors.  OR use there web page tech info.  They tell you about size, magnets, poles, winding size and turns.  All told via a designated letter or # in the part number.

As far as shafts size and such that is specified in the customer order.  You are not going to find a retail selection of every motor they make.  Most are single shaft end.  Harder to find the double end for a flywheel.

These a made for wholesale.  Not retail.

Getting lucky on Ebay or a salvage store is the only way you will get something close.

Just buy one from MTH.   G

GGG, when I apply 4.5 volts, it's from a battery pack, so it's pure DC.

I have seen the model identifier table on the Mabuchi web site, but it isn't complete as there are also sub-suffixes.  Your comments on Mabuchi motors are correct; I agree.

It galls me to pay MTH $25, plus the enormous s&h, for motors that sell on the open market for $3.  

RJR I give you a TON of credit for trying.  I've thought about this a million times myself.  But I don't believe your project will be successful.  It's a combination of the gear ratio, and the motor SHAPE.

Let me start by saying I'm not a fan of Mabuchi motors.  As you've discovered, it's hard to get specs on them.  They are cheap-- cheap for the manufacturers to buy in bulk, and just "good enough."  They have no place in a top-of-the-line loco.  I'm still angry with Lionel for using one in their new USRA heavy Mikado.  Better name brands are available with more poles, more torque, and better starting characteristics.

Regardless of which brand you use, a "can" motor is symmetrical relative to its shaft.  Conversely, the original Pullmor motor has a large protruding field coil on one side, while the armature poles extend less than 1" from the shaft on the other side.  (In the Berkshire, the armature side is facing downward.)  So any concentric "can" motor you might use will have a smaller rotor diameter than the Pullmor motor it replaces.  Unless rare earth magnets are used it will probably have less starting torque.

One way to get around the dimensional problem AND increase torque would be to use a motor with an offset gearhead.  Planetary gears enclosed in one end of the motor multiply torque.  Because the output shaft is usually offset, this also solves the shaft alignment problem, allowing you to fit a bigger motor.  Unfortunately surplus gearhead motors are harder to come by in the aftermarket.  2:1 would be ideal, but the lowest common ratio is 7:1, which is too slow.

Therefore, the best solution really would be to change the gear ratio of the locomotive.  How are you connecting the motor to the worm wheel on the 4th driving axle??  In a Railking or LionChief steam loco with RS-385, gear ratios range from 20:1 down to 17:1 (which I think is STILL too fast--at wide open throttle these locos can exceed 100 scale mph!)  By comparison, your 736 has a 25-tooth worm wheel and a triple-start worm for a gear ratio of 8.3:1  Now you see why the Mabuchi motor won't give "typical" performance in the remotored Berk-- it's turning less than HALF the speed it would be in a MTH RailKing loco with PS2.

Unfortunately changing the gear ratio is very difficult due to the way the 736 and just about every other Lionel steam loco is made.  You would pretty much have to mill out the whole chassis and install a Northwest Short Line (NWSL) gearbox.  Hopefully there is enough clearance that the bottom of the gearbox wouldn't drag on the center rail.  You would probably have to relocate the pickup rollers to the tender and use a wiring harness between the loco & tender.  2-rail O scalers don't have to deal with these problems!

If you're really determined to have a postwar Berk with PS2, the 1946-issue 726 is a more promising starting point.  It's a shame, these '46 Berks are kind of rare and expensive to tear up for a project like this.  The gear ratio is a bit lower on the '46 version, but I would still use an NWSL gearbox, and a lot of rework would still be needed.  Like I said, I've put a lot of thought into this myself.

A while back someone else on the Forum consulted with Frank Timko about remotoring a 736.  Frank has been putting can motors in Lionel locos longer than most.  I can't remember if Frank actually accepted the job, or said it wouldn't work.  Either way I recall the outcome as being less than satisfactory, appearance and performance-wise.

As I said on another recent thread, I believe there is definitely a market for a smooth-running "traditional" loco.  There are plenty of 736, 2046, 2018 shells out there.  Someone just needs to step up and engineer a bolt-in replacement chassis that will give smooth 2-60 mph operation without a bunch of gimmicks.  It can be done, but so far, no one has.  If I hit the lottery I promise I'll take this to the mechanical engineering lab at MIT!!  -Ted

Creep, coast, and pull: It's not that hard...!

Constant 4.5V is a lot.  PWM Shots is less total power applied. 

Still don't understand the point your trying to make?

These motor can run on much lower voltage unloaded.

You bought a motor from a vendor, the motor doesn't work right.  Either the vendor sold you a bad motor, or you damaged it some how.

Go back to vendor and get a replacement.

I have looked hard, like I said you won't find many double shafted motors out there.  If you do, you still have to gear and flywheel it.

Go make a purchase for a 1000 from China.  I am sure you will be able to sell them at a profit.  G

Ted, I have converted a #624 Pulmor and it's a very good runner.  Smooth all the way down to 2 smph.  Below 6 smph, the 736 would hesitate each revolution when the drivers reached a certain point.  Inspection by me and a true Lionel expert both concluded loco is mechanically correct.  He compared the motor to a similar conversion he has, and determined my motor had less torque than his.  That led me to dig into Mabuchi and make the original post.

By the way, I do have a 1946 726.

GGG, my only point was to glean info on these Mabuchis.  Looking at various retailers' catalogs, they are available singly in a myriad of versions, but how to pick the version?  Three weeks ago I, and probably many others, thought an RS-385-PH was a single motor model.  I have found otherwise, and now am trying to learn if motor is bad or just a different model.  That's the current effort.

In retirement, I like to tackle oddball projects, many of which have been mentioned on the forum.  Most all eventually function as intended.

RJR, Every time some one has post they need a RS-XXX motor I have provided information to spell out that is only the basic size and type of motor.  I understand some times that info doesn't stick to you actually have to use it.  Now you living it first hand.

The last 4 # I gave above is the winding size and count for MTH 12VDC motors.

With that information you can go and compare the ratings of what you find.  The problem is finding a double shaft motor.  Most commercial applications do not need that.  Or if they do, they also have a decoder on it and the cost is much higher.

Mabuchi technical page gives you all you need, coupled with what I have told you MTH uses for there engines.  

The hard part is finding one close at the inexpensive price you want.

Why not e-mail the retailer and say you want a double shaft RS-385PH-2655 and see what they say?  G

RJR the 624 will always run better, because the driving wheel diameter is an integral part of the gear ratio.  The switcher travels about 0.31" for every revolution of its motor (which is very close to the expected value for an MTH diesel.)  Meanwhile the 736 is traveling a whopping 0.47"  A RailKing Berk with PS2 travels about 0.28" per motor revolution.

Factor in more flange friction on curves due to the long rigid wheelbase, and uneven thrust loads associated with power being transmitted through the rods.  Frankly I'm surprised that the 736 is able to run at 6 mph.

Another disadvantage of the 736 relative to, say, a RailKing Berkshire, is that the 736 is driven from the 4th (last) axle.  The RailKing is more properly driven from the 3rd axle.  A lot of slop can build up in the rods between the first and last axles; quartering is more critical.

When the project is finished, it would be great if you could post some close-ups and a video.  Thanks for sharing!

I agree with everything you say, Ted.  With the variety of these Mibachis available, and given that I do not run at high speeds, I'm exploring the possibility of finding a higher torque lower voltage motor may do the job of overcoming the unbalanced load that results from having the aide rods drive 3 sets of drivers.  The 624, being gear driven, is a more constant load.

There is on the DCS forum pictures and video of the 624 conversion.

GGG, the info you provided, that MTH uses a RS-385PH-2655, is invaluable.  That makes it a 12-volt motor, according to the Kysan catalog.