PRR H10 Remotor

[Lemosteam]

My guess by looking at the earlier pictures is that the worm under load is driving itself into the bushings and causing the extra drag. There needs to be a brass or teflon thrust washer on either end of the worm shaft between the worm and the bushing. That may help some.

This. I was thinking the same. Teflon or Mylar would be best.

[victor miranda]

small ball bearing?

[Lemosteam]

small ball bearing?

Axial thrust on the worm graer and its shaft can only be prevented if they are opposed tapered roller bearings shouldered against the worm and trapped in the frame. LOL.  Does anyone make them that small?

Has he determined if thrust friction is actually the culprit?

[victor miranda]

the cause of the heat is power into the motor...

I have a set of indicators.
If the motor heats quickly,  the motor shaft is bound
if the loco seem bound or tight and the motor take a while to warm
it is a driver or idler gear past the  worm.
I have not been able to tell if the motor is a 6 volt type  or if the mechanism is bound up.

lemosteam,
one of the things I love about well trained engineers is that they often have the right answer.
you are correct.
now can we have a conversation about 'close enough?'

if you want you can read the specs on the various 1 and 1.5 mm ID bearings
I am pretty sure that an n-scale motor and worm are not even close to
the weight limits for axial thrust.

it is easier to install a thrust bearing into an n-scale loco than a ball bearing cassette.
... you may want to take my word for this....
don't bother with the thrust bearings.

I've built ball bearings to ride on worm and shaft.
they work.  like the bicycle bearings they resemble,
they perform better with careful adjustment.

at 50 cents a bearing the bearings are effective and easy to adjust.
and if you wear them out.... replacement is a few minutes and a dollar in parts.

I'll bet they outlast a kato FEF motor....

victor

[nscaleSPF2]

As planned, I replaced the drivers, added Kato tires, and replaced half of the valve gear.  The other half of the valve gear that I purchased had a crosshead lever that was frozen, so I did not use those parts.  The Bachmann parts diagram also called for a washer between the connecting rod and the side rod, but these were missing, too, so I fabricated and installed new washers.

In this process, I also noticed that the LH side rod was bent about 10 degrees, in the side view, so I straightened it.  This is a photo after straightening.



You can see the nick in the rod.  Something had apparently hit it with some force, and caused the side rod to bend.  Can't imagine what that was.  It also looks like someone had drilled out the holes for the side rod pins (both sides).  I would have ordered new side rods, but they are not available from the Bachmann parts store.

Put it all back together and she ran slightly faster and smoother, as expected.   Will put a few miles on her tomorrow, and take some speed and maybe volt & current measurements.

The motor only gets slightly warm at half speed (14/28), but it does get hot at 3/4 speed.  But the motor ran hot on the bench at 3/4 speed without any load (not installed in the chassis).  Victor could be right; this could be a 6 volt motor.  Even though there is a sticker on it that says it is 12 volts.

I wish you guys would make up my mind regarding the thrust bearing.  The worm does load the motor bearings, as SkipGear deduced, so I originally had a Delrin thrust washer to prevent this.  It's shown in one of the photos above.  But Victor predicted that it would make noise (it did) and I think he said that it was unnecessary.  So I removed it.  To reinstall a thrust washer at this point may not be worth it.  Since I think the top speed of the prototype was about 50mph, I'm ok with using the decoder to limit the max voltage to 6v.

[Cajonpassfan]

Jim, very interesting thread, thank you. It is a pleasure to follow.
As you indicated, these engines didn't run over 50 mph (and in most circumstances, probably not much over 30 I'd bet) so I wouldn't worry about having to limit the top speed for that reason. The real test will come under load, with say your 14 cars in tow; how will the limit affect speed and pulling ability...  I have some tall-geared, underpowered brass that performs well, but fizzles under load.
Looking forward to your updates,
Otto K.

[victor miranda]

the side rod looks right to me.
the main crank hole is bigger than the first and fourth driver crank holes.

If the sticker says it is 12 volts then we will assume it is.
getting hot at 12 volts is not out of the ordinary for small motors
that are rated at 12 volts. (If you think an Atlas diesel motor is a big motor anyway...)

the heat will tell you the current limits you want to stay under in any case

I'd pull 15 cars and see if heat is a problem.

victor

[nscaleSPF2]

A couple of you suggested in previous posts that I measure the current draw of the motor, to get a handle on the engine speed and motor heat issues.  The results were interesting, to say the least.

First I took a spare motor, identical to the one in the loco.  Powered it with DC on the bench, no load, as a baseline:

MOTOR ONLY, ON BENCH, NO LOAD      
      
V, dc      mA
1.3      20
3.7      34
6.4      37
8.4      39
10.5      40
12.6      41
15.5      42
18.0      44

The current draw is a little less than the spec.  So far so good.

Next, I powered the loco on the bench with dc, thru the decoder, with no load on the motor except for the drivetrain:

LOCO, ON BENCH      
V, dc      mA
4.5      82
5.0      90
6.0      100
7.0      105
8.5      114
17.0      150

These numbers still look ok to me, but then I don't have much experience taking these measurements.  What do the experts think?

Lastly, I put the loco on the track and powered the decoder with dc.  Immediately, I noticed a couple of things.  The top speed increased, and the motor ran much cooler.  It's as if running the motor on dc reduced some of the friction in the drivetrain.  I measured the loco by itself, and with it pulling 20 cars on level track.

LOCO ON TRACK, WITH DECODER                        
                        
      LOCO ONLY           LOCO + 20 CARS   
Volt      mA      mph      mA      mph
5      86                      94      
6      104                    106      
7      113                    120      
8      119                    132      
9      124                    139      
10      130                    142      
11      132                    145      
12      137                    151      
13      140      46.8      151      36.4

The motor got warm after pulling the 20 cars for about 15 minutes, but it was still ok to the touch.

At this point, I also tried to put to rest the thrust washer versus no thrust washer issue.  This is for the washer on the rear of the worm gear, also discussed in previous posts.  I ran the engine forward and reverse, at several speeds.  The current draw, speed, and noise level were almost identical for the forward and reverse directions.  So, no need for the extra thrust washer.

I welcome all of your comments.  Sorry if the columns of numbers are not straight.  I know that this will bother the engineers out there.  It bothers me.

[victor miranda]

what a magnificent post.

in what may seem like I am ignoring a lot of the data you collected

here is my guesses on your result.

I found a datasheet that says the max current
at 70 ma at 12 volts
to me that means you want to stay under (70ma*12v-->840mW)

from what I see in your data the voltage and current is pretty linear
I suspect the decoder is involved. I am thinking the decoder is using about 100mw here...

My recommendation is that you stay under 1200mW
the 20 cars 8 volts and under140mw is likely to be your real limit.

victor

[mmagliaro]

The Mashima 1015 70mA limit is for no-load on a bench.

Several years ago (5?  more?   cannot remember), it was actually possible to email
Mashima and speak to the company president about the motor specs.   Their website used to have the email address and they
used to answer it.   They do not any more. 

I was wondering what the real load limit was for the 1015 (coincidentally), so I asked them.
I got back a reply from Mr. Katsumi Mashima (he is THE GUY).    It was a hoot.   He had worked out current and torque curves
on the motor, drawn it all out hand-written on paper, and someone there (maybe him) scanned it and emailed  it to me.

I am going to dig around to see if I can find it.

All I can remember is that the actual operational load limit for that motor was much higher than 70 mA.  I want to say it was about
200 mA, but I cannot really remember, so I will try to find those notes.   I really hope I didn't lose them.

[victor miranda]

Hi Max,
no load bench 70ma is max....

not what the spec I read said...
....oddly enough

http://www.gizmoszone.com/shopping/html/pages/mgh1015datasheet.pdf

some one's datasheet...

happy reading.

it says 3400 rpm and 70ma and then lists off to one side no load....
I think there may be a gearbox involved...

another...
http://www.hollywoodfoundry.com/mashima%201015.jpg

it lists 350mW as the max power output....

so there is some inconsistencies in the ratings.  70 by 12 volts is 840mW
I tend to go by how fast it gets hot...

and to drag in a couple of important items to note
overall size is a leading factor in how much heat can be dissipated.

the Kato Chibi motor is similar size and gets hot at over 7 volts and over 150 ma
which is the main reason I stated the limits I thought reasonable...

the 150ma is ok at 5 volts BTW
   

[victor miranda]

Max,

I want very much for you to share the Mr. Mashima's datasheet
because I would believe it.

the other datasheets are ... inconsistant.

my conclusions are not standing on data that is good enough.
they are based on facts I do not trust.

victor

[Doug G.]

May I write a little aside here? OK, I will.

Back in the late seventies when I worked for Telex and we made 8-track raw decks for Ford, we used Katsumi self-governing motors for the quadraphonic units. These were made by the same company and I imagine they just used different parts of Mr. Mashima's name for different product lines.

He (I am assuming it's the same Katsumi Mashima) and others from the company used to come to Rochester when there were any issues with their motors and it was a blast.

I also want to add that 200mA is pretty common for any normal sized N scale motor as a nominal in-use current draw. Smaller ones, of course, may be expected to tolerate less.

Doug

[mmagliaro]

Doug,
WONDERFUL story about meeting Mr. Mashima!

Victor,
So far I have been unsuccessful at finding that hand-written sheet.   I am going to keep digging around.  It was so much more
than a data sheet.  I showed not only various power, current, and torque ratings, but it showed how he calculated them,
complete with little hand-drawn graphs.  It was like a brief lecture series in how Mashima designs and rates their motors.
Boy oh boy... I hope I can find it.  I hadn't thought about it in years, until this came up.

[Doug G.]

That's really neat, Max. I can tell by your description that the sheet reveals the typical intensity of the Japanese in their endeavors and we at Telex experienced the same thing. Those guys got right down to it and didn't let up until a problem was solved.

Then we would go out and have fun at night.

Doug