Getting rid of Flywheels

[7j43k]

selector

My BLI steamers all have brass flywheels.  They all come to abrupt and sudden stops if there is a short and power is cut to the rails, or if they encounter dirty or dead track. 

 

In the case of a short, locomotives will stop MUCH quicker than in other cases.  This is because the motor turns into a generator and the short acts like a dynamic brake  grid.  

But if power is cut to the rails, or there's dirty or dead track, this quick stopping won't happen.  There's still a generator, but it isn't connected to a load.

 

I've got panic switches sprinkled around the layout.  If you throw those switches down, the track rails are shorted.  All trains will stop NOW.  Happily, I've never had the need to use them.

 

 

Ed

[selector]

Ed, what you state for simply dead portions of track does not happen in my case.  When my brass hybrid Q2, a heavy locomotive, is descending my 2.3% helix with a hefty load behind it, running about 40 scale mph, and it hits oxidized track or a turnout that has poor wiper contact for power-routing, it comes to a dead stop very smartly with no discernible momentum, certainly none I could remotely attribute to the flywheel.

If I had the skills to disassemble locomotives safely and to test them somehow, I would do it just to satisfy myself.  It could be a project to tackle, and then to submit an article to MR. 

-Crandell

[7j43k]

Crandell,

I'm not saying that a locomotive won't stop very quickly when power is cut.  I'm saying it will stop MUCH MORE quickly if it's feeding into a short.

I'll suggest that it's possible your loco is experiencing a short, rather than an open. Suggesting only.  Something like a lead truck touching something.  Maybe.  BIG maybe.  And maybe not.

Congrats, by the way, on the loco.  I was sore tempted to get one back when they came out.

 

Ed

[hon30critter]

This is an interesting discussion for me.

I am in the process of doing a comparison between two Hollywood Foundry BullAnt drives. One will have the recommended flywheel and the other will have a Power Pack keep alive from Loksound. These will both be installed in Grandt Line switchers, one is a 25 tonner and the other is a box cab. They will both be the same weight hopefully so the difference in body styles won't matter. They will be DCC with sound.

These are obviously very small engines so it will be debateable as to whether or not there will be any relevance to larger locomotives.

I want to try the keep alive because I know it will solve one of the perennial problems with small, lightweight locomotives which is consistant power pick up. Getting tiny switchers to run smoothly on less than perfectly clean track or over switches is a challenge. As we all know, the theory is that a flywheel will push the motor enough to allow it to get past these power interruptions but, as the examples in the above posts demonstrate, this doesn't often work. My theory is that the keep alive will offer a couple of seconds of reserve power whereas the flywheel offers only micro seconds of "reserve power". In other words, the keep alive will turn the motor over many more times than the flywheel will thereby allowing the locomotive to move much further along the track before it stops. Hopefully by then it will have found fresh power so it can 'motor on'. (sorry, couldn't resist).

What will be interesting to see, assuming the keep alive solves the power pick up problems, is how smooth the tiny locomotives accelerate and decelerate and whether or not they can crawl equally as well.

This project is not going to be finished next week, or the week after, or likely for sometime after that so please don't hold your breath. I'm working on it a bit at a time along with several other things. I don't want the project to turn into a chore.

I'll start a new thread when I have the results.

As always, any comments are appreciated.

Dave

[Kyle]

I have a Proto 2000 E7 (Lifelike, pre walthers) that has a lot of momentum.  It has almost every space under the shel filled with weight.  In addition it has flywheels. I am not sure how large the flywheels (since they are covered by the weight), but I suspect they are really large.  The locomotive has a lot of momentum, taking a foot or two to stop from a reasonable speed, and the speed stays constant over track that isn't perfectly clean.  It is DC so no momentum control.

I think flywheels work well in long locomotives, as well as locomotives with ful width bodies.  These have the most space inside the shell and accomidate large flywheels.  In freight locomotives like the GPs and SDs, the width of the hood reduces the amount of space inside the shell, forcing flywheels to be smaller.  In short locomotives, the flywheels can't be as long, and are smaller.  Flywheels work well in large locomotives when they can be large, but smaller locomotives don't have the space for large enough flywheels.

[7j43k]

hon30critter

As always, any comments are appreciated.

Dave

 

 

Dave,

 

I think you're onto something.  Thinkin' ain't knowin', though.  So I'm looking forward to your results.

 

 

Ed

[Texas Zepher]

hon30critter

As always, any comments are appreciated

Another factor is the gearing.  A flywheel on a greately geared down loco will be spinning faster (more kenetic energy) and might produce more dramatic, or at least more delta measureable results.

A power stuttering DCC decoder can stutter the forward/reverse signals to the motor that obscures the dis/advantage of a flywheel, so I'm thinking the choice to use a keep alive type decoder is good.

[hon30critter]

Texas Zepher

You raise an interesting point. The gear ratio on both drives is 60:1 so the flywheel spins fairly fast relative to the axle rotation. However, the effect of the flywheel is reduced at the lower speeds where switchers tend to operate whereas the keep alive more or less works the same regardless of the speed.

In order to not keep everyone waiting I have decided to expedite my work on the switcher with the keep alive. I hope to have it running within a week or two. There is some detail work, painting and decaling which will take a bit of time. The switcher with the flywheel was finished a few weeks ago. You can see it here:

https://www.youtube.com/watch?v=xwZqS7C_g20

Dave

[gmcrail]

Well, fellows, as far as coasting goes, I have a Hobbytown RS3, with a big flywheel in the cab and low-speed gearing, that will coast at least 2.5" if the power is cut at 50 smph.  OK, not far, but certainly enough to spare some drawbars in the consist...  Which could also include the paneling on the wall!

Adn I can throttle it down to <1 smph and start it even slower.  So, I vote for flywheels...

 

[gmpullman]

Here's a neat photo that I came across of a shear used in the Erie's Hornell, NY, shops. Many examples of heavy power equipment utilized flywheels weather powered by water, line shaft, steam or in this case, an electric motor. This was especially important when the load would vary greatly such as a piston pump or, in this case, a shear that would be driven by a reciprocating cam or arm.

I remember my first flywheel equipped Proto 2000 E-7s and 8s. Running a good 60 or 70 SMPH they would easily coast two feet or more when the power was cut. It kept the engineer on his toes to prevent overshooting a stop!

Regards, Ed

 

[mlehman]

Ed,

Interesting pic and I think your comment about using a flywheel to overcome a widely varying load is an important one.

A couple of posts back, Dave commented:

"However, the effect of the flywheel is reduced at the lower speeds where switchers tend to operate whereas the keep alive more or less works the same regardless of the speed."

I wondered about that when Dave mentioned it. I'm not a physicist, so won't bother with any theoretical insights I'm liable to miscast anyway on the laws of motion, etc. And I don't think Dave is completly wrong here, just that such comparisons have to keep in mind it is sort of an apple vs orange thing at best.

However, it may be that a flywheel's greatest net effect or influence is at lower speeds, assuming it's already spinning. I would argue that's where it would have the greatest observable effect anyway, even if it's not the greatest net effect as it would be at higher speeds. However, that would be with an optimally sized flywheel, which likely isn't possible in HO and the smaller scales. Dave may still discover the keep alive works better...

At which point I may be looking at stuffing a keep alive in my Grandt 23-tonner.

[Lake]

Of those that posted, are there any who run N-Scale? It seems as if only one person does so.

 

I do N-Scale and had non flywheel late 1970 early 1980,s engines all three pole non-flywheel engines when I started my newest layout in 2007. I was going to go DCC and bought some Atlas GP38-2's with flywheels to put decoders in. But, first ran them on DC for a while as I put the layout together. Then compared them to the older engines with out fly wheels.

IMHO, The difference was noticeable. As the newer ones had better motors it may have helped, but they ran better with clean track and clean wheels and contacts.
Then I went DCC and added decoders to the new engines and to three of the older better running engines (I have know idea what make they were) And one of the later ones bought in late 1980"s had a 5 pole motor.
The ones with fly wheels still seemed to run better.
Also the extra weight of the fly wheels in N-Scale is very well received.

[Darth Santa Fe]

On the topic of flywheels keeping trains from stopping in time, my power pack actually has electronic emergency braking for this! If it detects that a motor is coasting, it'll apply a small reverse voltage to stop it almost immediately. Even my P2K E7 with its dual 1" flywheels will stop in a few inches from full speed! Of course, the power pack is 30 years old, so it's not exactly available anymore, but my uncle originally designed and made them, so I'm kind of hoping we can update it and get it back on the market...

Sometimes I actually wish I could turn the braking off so my big flywheel trains can coast naturally, but oh well.

[hon30critter]

Here is the link to the thread I started to explore the difference in performance between a flywheel and a keep alive circuit. If you scroll down a bit you can see two videos of similar size/weight locomotives, one with a flywheel and the other with a Loksound Power Pack keep alive:

http://cs.trains.com/mrr/f/744/t/247568.aspx

(To get the link to work, highlight it, then right click on it, then select 'Open Link' or words to that effect from the drop down menu).

The bottom line is that the keep alive equipped locomotive performed infinately better than the flywheel equipped one did. Keep in mind that these are very small locomotives. As you will see in the other thread, the Loksound Power Pack may not be the best keep alive option for all situations.

Also, apologies to the OP who was asking about DC operation.

Dave

[gmpullman]

http://cs.trains.com/mrr/f/744/t/247568.aspx

Dave, I took the liberty of making your link clickable.

Ed

[hon30critter]

Thanks Ed

I'm going to start a thread asking that exact question - how to make the links clickable, rather than have it buried here.

Dave

[BRAKIE]

Lake

The difference was noticeable. As the newer ones had better motors it may have helped, but they ran better with clean track and clean wheels and contacts.

Atlas  N Scale locomotives  uses their Scale Speed Motor(aka Slo-Mo) and that IMHO improved the performance and with the flywheel slow speed switching with kiss coupling (coupling without moving the standing car)  became possible and preferred by those of us that loves switching.

 

I really miss my  N Scale.