Too Much Weight In The Engine?

Bob,

you may have reached the top of the motor's horsepower curve at 90% voltage, or as you suggest reached max output of the battery, which seems more likely.

Chris,

That's what I'm thinking, I don't think I altered the max speed when I made adjustments on the receiver board (only adjusted the low end).  Add to that the weight of the lead inside the front of the boiler, plus the low gear ratio (43:1 I think it was) this 14lb beast is only going to move so fast.  The motor in it is a Pittman 8514.

Right now the max speed is only about 45mph, I may remove the 2lbs of lead and see what happens, but I don't want to lighten it so much that it won't pull a 5-car train.

I use the 11.1 LiPo battery packs in 4 other steamers and they all have good top end speed, but they don't have the same gear ratio as the J does.

I think I can remove the lead easily by removing the "nose cone" front end on the J and there may be 2 screws holding the lead in place.  Getting it back in and the holes lined up was an issue but doable.

FWIW, While reading the original post, I was thinking the same thing.

Wow, 14 lbs sounds like a bit much for that 8514 motor.

that sounds like too much weight to me.   Ihave a Max Grey 2-10-4 that only weighs about 7-8 lbs.   That is engine only, not including tender.

I would run it without the weight if it were me.    I would be afraid of tearing up the gearbox if you hit a dead spot at speed with that much weight.   I have seen it happen to locos.

I think the 14.2 lbs was engine and tender, the lead weight was in it when I got it off Ebay.  If I can easily remove it without having to take the boiler off I'll do it tonight.

more later.

3 screws to take off the boiler and 2 screws holding the weight in, about 10 minutes to take apart and put back together.

No change in overall speed.  I thought for sure removing 2lbs would have some effect, other than it's easier to carry around .

Actually, the speed did increase at 80% throttle, by only 0.5mph, but stayed the same at 90 and 100% throttle.

I put (3) 20-21" Weaver aluminum passenger cars behind it and saw no change in speed at 70% throttle, which turns out to be approx 32mph.

Again, top speed at 100% throttle is only 45mph, with a 11.1v LiPo battery pack.

I could go to a 12v NiMh battery pack to give it more power and it would be about the same size as the LiPo pack, but for now I think I'll keep things like they are.

45mph isn't close to what the real J can do, but it's within the speeds they presently run and plenty for my smallish layout.  Good thing is it still creeps at slow speed.

That much weight will be hard on the axle bearings also.

While I think that a 14 lb. locomotive is too heavy, I would also check the voltage to the track. With 12V batteries, I would bet that the actual track voltage with a fully charged battery is about 10.5 volts. With a lighted passenger train, it may well be even lower.

If you have a DC pack, try running the engine with that, but again check the actual track voltage to be sure the engine is seeing 12VDC.

What about gear ratio? The original can motor would have been a hi rpm by nature. Just thinking!            cTr...(Choose the Right)

Hudson, no power to the track, 100% battery powered.

Stephen, the original gearbox in the Williams brass J is still there, 43:1 ratio.  That's why the low end speed is so good, I guess that causes the top end speed to be lower than "normal".

I never could figure out what the RPM of the original motor was, but it's the same motor as in my other Williams brass engines, both 2-8-2s, and they're a bit faster than the J because of their gear ratio being 23:1 or something like that.  The original motor had a bent shaft so I had to replace it.

I can't recall if I tried swapping gearboxes out of one of the Mikes into the J, but that may be a cure for the slow speed.  Both Mikes have a 9.6v NiMh battery pack in them, compared to the 11.1 LiPo pack in the J, so the low speed isn't all caused by the voltage.

I have 2 Railking 2-8-0s that behave differently too.  One has excellent slow speed while the other has to be coaxed to get it to move.  It probably has some binding somewhere, just haven't figured it out yet.  My RK Imperial 0-6-0 is the best slow-speed engine I have, great gear ratio MTH

Don't know if this will help any but when I Google Pittman 8514 the search returns with a O Guage RR topic that recommends swapping that motor with a 8524 as it seems to be a better performer perhaps??

https://ogrforum.ogaugerr.com/t.../pittman-motor--8514

Sounds like you don't have enough mah in your battery. What mah is your lipo? Lipos are more burst capacity and when you put them under a full drain load they tend to drop in voltage pretty quickly.

The 11.1v LiPo is 2200Mah and lasts well past 2 hours run time.  The 43:1 gearing combined with the 11.1 volts is what's holding the top speed down.  I use the same type battery pack in 4 other engines but their gearing is more like 23:1 and run faster with the same voltage.

When I still had PS2 installed in this engine it screamed around the track, way too fast for me.  I'm not sure what voltage PS2 puts to the motor (what voltage does the TIU and PS2 circuit convert the 18vac on the track to?), but I expect it's more than the 11.1 volts coming from the battery into the RCS receiver in the tender.

I don't mind the 45mph top speed, but wouldn't mind if it was 60mph.

Bob,

Just curious what RC system are you using, if any? A 2200 is pretty limited. You could get something a little more powerful allowing more RPM.

Ron

Here is the way you weight a model locomotive.  Grab the tender and hold it stationary.  Apply power.  The drivers should slip.  If they do not, remove weight until they do.  The end.

The 8524 has rare earth magnets.  Some will argue with me, but I maintain you will get almost twice the pulling power, or almost half the current draw at the same load.

It is that third digit.  It must be a 2 or 3. 

Murtherfore, if that is a Williams J, the Chinese motor it came with is more than adequate.  The Pittman runs too slow for passenger work.

Ron,

The system I'm using came from RCS Australia:

http://www.rcs-rc.com/

I'm using a Tx7k Transmitter and a ALPHA-3v2 Receiver.  The battery pack is an 11.1v 2200 LiPo pack from All-Battery:

http://www.all-battery.com/index.aspx

Bob, I've take out all the lead weight and the results were the same, but I'll keep your idea of figuring wheel slippage in mind for the future.

I may reinstall the original motor to see what happens.  I think you're right in that the Pittman motor had lower RPMs.  I said the original motor had a bent shaft but it may have been the mounting wasn't as good as it should have been.

A battery with a larger Mah rating is more expensive and larger in size, but the Js tender has a lot of room

IT'S THE MOTOR!!!

I put the old motor back in and at 75% throttle the speed was 55.4mph.

I didn't take a measurement at a higher throttle setting because of the ungodly noise the thing is generating (that's why I replaced the motor to start with), but it's definitely faster when I increase the throttle past 75%.

I could swap out motors from one of my Mikes into the J (and put the slower Pittman in the Mike), but for now I think I'll put the Pittman back in the J and be happy with the 45mph top speed (and the quiet).

Bob

I agree with Bob2's advice about the value of rare earth magnets in Pittman can motors - higher torque is a key factor for smooth starts under load. There are very large differences in 12V RPM between the various models of Pittman can motors.  In particular the 8xxx (1.1" dia) motors have higher RPM than 9xxx (1.58" dia) motors.  The 8xxx and 9xxx series motors came in different lengths, type of magnets/bearings/windings and shaft arrangement. I have some old  Pittman data sheets that lists peak torque and  load RPM for several models.  That info may help you make a  decision about which Pittman motor you currently have would best match the  service you intend the locomotive to be used.  If you would like the data email me the model numbers and I'll send you the data on them.  One nice thing - swapping Pittman can motors is often quite easy as the motor mount holes are usually compatible.

Ed Rappe

Re: noise.

Did you remove the flywheel before re-installing the original motor?

If you wish to use Pittman, consider a 7 1/2 volt motor.  Then run it at 12 volts.  I am quite sure you will find the Chinese motor satisfactory without the out-of-balance flywheel that came with these things.

Ed/Bob,

I've looked for the 8524 motor but all I see is OUT OF STOCK.

As far as the flywheel goes...I actually put it BACK ON when I reinstalled the old motor.  I'll take it off and see what gives

Ed, if taking the flywheel off doesn't improve the sound I'll email you, thanks!

Sorry...I should have typed "check the voltage at the motor terminals", instead of "check the voltage to the track"!

There is a very simple and easy way to check the weight of a model locomotive against the rating of the motor.

1. Look up the maximum sustained current draw that the motor is rated for.
2. Put the locomotive on the track with an ammeter in the circuit to measure how much current the locomotive is drawing. (Yes, I know this will also be reading the current drawn by the sound system, but that just provides a little fudge factor to be sure you don't over rate the motor.)
3. Slowly apply power and watch the current rise. You don't care about the voltage, only the current draw.
4. Note the peak current at the moment the wheels start to slip. Once the wheels are slipping the current will drop a little. You want to know the PEAK current drawn just before the wheels start to slip.
5. If that peak current is less than what the motor is rated for, you can add weight and try again.
6. If that peak current is HIGHER than the motor is rated for, you need to lighten the locomotive a little and try again.
7. Weighting a locomotive so that the motor cannot exceed the current it is rated for insures that you will never burn up a motor. The wheels will slip before the motor draws more current that it is rated for.

Bob,

thanks for the info.

Ron H

Rich,

I understand what you're saying, but I have a question...what impact if any will rubber traction tires (RTT) have on this?  Couldn't the RTT cause the wheels not to slip when they normally would without RTT?

But then again, slippage is slippage and whenever they start to slip (with or without RTT) is when peak current is met.

You're welcome Ron!!!

I tried the old, original motor without the flywheel and it was even noisier (must be the ball joint & shaft between the motor and gearbox) so I took it back out and reinstalled the Pittman.

Quiet once again, but back down to 45mph top speed.  I need to figure out what the rpm is of the original motor.  I have a similar motor but it's max rpm at 12vdc is much less.

Yes...you've got it.

I suspect that most locos with traction tires will severely overload the motor before they slip the wheels. Load an engine like that to its traction limits, run it for a while and you'll be seeing smoke soon.

Well, not really.  A locomotive that is light will slip at lots less than peak current.  I do agree with Rich that optimally you would want the setup so that peak current would never occur.

I forgot about those traction tires - driver slip is a little like a circuit breaker, keeping you from burning up motors.

Here is something I don't know - is this peak current you are looking for a continuous rating on a stalled motor?  I will look it up and report back.

Bob

I had several Williams/Samhongsa locomotives that were annoyingly noisy. One source of noise was out of balance fly wheels.  In regard to flywheel balancing check my recent OGR post under Weaver - my first attempt.  I did replace the motors with Pittman's (back then we did a group buy for dozens of motors to reduce our cost).  I'd also suggest looking at the gearbox swap.  My Williams PRR B6sb 0-6-0 had 25:1 gearing while my Williams L1s 2-8-2 had 43:1.  I swapped gears improving the performance of both locomotives.  I don't recall exactly what steps I went through but do remember it was a "piece of cake" as the boxes were virtually interchangeable. Perhaps an exchange of gears between your J and one of your other Williams locomotives would work for you. 

If you want to try a 9V Pittman motor you can have the one I removed from a PSC K4s.  The cost to you would be a drive over to Williamsburg. Why PSC  put 9V motors in their O scale K4s remains a mystery.  At the time it caused quite a flap with customers.

Ed Rappe

From what I'm reading here all we've talked about is amps being drawn by the motor and driver slippage....all find and dandy but, for me, there's more to it than that.

The more weight the more wear on your drive train.  This includes gears, bearings, motor, etc but especially side rods on a steam engine.  The older Max Gray and USH rods were pretty substantial but most of the newer models are not.  I've seen nickle plated brass crank pins that look great but don't last and adding weight would promote even earlier failure.   A motor running at 50% maximum load will last far longer than a motor running at 100%.

For battery power I would say, the less current you draw the longer your battery will last so why add weight if you don't need it.  As a side note, with battery power you want the most efficient motor you can get.  As you already know, amps eat up battery life.

I suppose one might ask themselves, how much do I really want to pull?  Weigh the loco to perform for your specific desires.  Any more is a waste.

Years ago (sometime in the '50s) Robert Lindsay, of Lindsay Motor fame, wrote an article (Model Railroader I believe) in which he talks about adding weight to a loco can become self defeating.  I wish I could find it because I found it to be most informative.  It went into his belief that after adding too much weight your model is using most of its power just to move the weight.  Obviously, I've oversimplified what he wrote.

Just my ramblings at six in the morning,

Jay

I think my original query on removing weight has been answered, although not very scientifically.

Removing the 2lbs of lead did nothing as far as slipping/not slipping, only reduced the amount of weight I have to carry when picking it up

Changing motors didn't seem to have any impact on slippage either.

I just ran one more "test" by seeing how many 21" passenger cars the J will pull without the 2lb weight.

I added cars until I ran out of them.  I have 16 passenger cars, 4 still have the claw couplers attached and neither of the observation cars have a rear coupler yet, so I was only able to add 11 cars total.

I ran it with 8 cars and the top speed went down to 39.1mph, adding the last 3 cars dropped it down to 38.7mph and stretched more than 1/2 way around my layout!!!

I observed no slippage (I did start off at a nice, slow speed until I reached 100% throttle).  I was surprised that the engine (now 12lbs) was able to pull 11 cars (another 22lbs, I think each car weighs approx 2lbs).  That's 34lbs polishing the rails at approx 40mph.

I really have no way of measuring voltage, current draw, etc on a battery-powered engine, only know the engine wasn't hot after the tests (less than 10 minutes total).  I expect it would get hot if let to run for a longer period and pulling that kind of load.

I don't plan on ever running more than a 5-6 car train on my present layout.

If GGD gets the "ALL CLEAR" and proceeds with the Silver Meteor then I may have to make arrangements, but for now I'm good.

That will be the next test, will the GGD E7 pull a 6-car Meteor or will I have to add my Williams E7 as a helper

Awk!  Brass crank pins?

They ought to be illegal - we spent time replacing brass crank pins on early Max Gray Northerns with steel.  A brass crankpin fails almost as rapidly as a brass gear.

...Removing the 2lbs of lead did nothing as far as slipping/not slipping, only reduced the amount of weight I have to carry when picking it up ...

Williams started adding the boiler weights shortly after the first few brass models were released.  the lighter (than diecast) brass locomotive performance was showing up in a decreased drawbar pull.  i never had a J, but i did have the GS-4 and i know it had a problem with the full compliment of coaches Williams came out with at that time.  more modern scale trucks might have better rolling characteristics, too.

whatever works for you.  i don't think the extra weight would hurt performance more than fractionally and might come in handy if you ever ran into a grade someday.

cheers...gary