capacitors for engines!

It would have to be a VERY LARGE capacitor!   Remember the LED lighting that they're powering is running maybe 50 or so milliamps and they're trying to keep it up for perhaps 100 milliseconds.  However, the locomotive can easily be drawing several amps, so keeping that running for the time necessary would take a very large capacitor.

They do add a capacitor in a sense.  It's called a flywheel. 

Right Stan, and it's clearly not enough for most cases.

Where are the battery powered advocates when you need them.

Didn't Lee Willis use a large capacitor for a flywheel on easy streets vehicles?

Oops. I thought this would be about flux capacitors in engines.

RoyBoy posted:

Didn't Lee Willis use a large capacitor for a flywheel on easy streets vehicles?

Scale that up to a O-gauge locomotive and the flywheel will be too big to fit.

It may not be here yet, but it may not be too far off.

The ham radio guys have units like this, and their stuff typically draws 10 - 25 amps at 13.8 VDC. 4 farads is a good start!

http://www.dxengineering.com/parts/mfj-4403

If you're smarter than (or think you're smarter than) a 5th grader you can do the math and calculate the (rotational) energy in a spinning flywheel disc = 1/2 x rotational inertia x angular speed-squared.  Use say 2000 RPM, 1" diameter brass disk, 1/2" thick, do the scale conversion.  Then calculate the ginormous capacitance to store an equivalent amount of (electrical) energy = 1/2 x Capacitance x Voltage-squared.

The problem is compounded since the capacitor is holding the energy is electrical form and must be converted to mechanical energy by the motor.  A can DC motor as used in O-gauge engines might be running at, say, 33% conversion efficiency so now whatever capacitor size you calculated must be multiplied by 3.

Of course if you don't have the ability to attach or augment the size of the existing flywheel then you're stuck.  But I think a chunk of brass will be cheaper than a capacitor storing an equivalent amount of energy.

Well, just for giggles let's do it this way, with some real(istic) numbers.

Let's suppose your motor is drawing 1 amp at 12 VDC, or 12 watts. I want to ride through a 1 second power loss. So, I need to supply 12 watt-seconds or 12 joules. I want the voltage to drop no more than 1 volt during the power loss. So, I need to deliver 12 joules while discharging a capacitor from 12 VDC to 11 VDC.

12 joules = (energy stored at 12v) - (energy stored at 11 volts)

12 = (1/2C x 144) - (1/2C x 121)

12 = 72C - 60C

12 = 12C

C = 1 farad

This is not precisely correct, but is plenty close enough for estimating purposes.

http://www.mouser.com/ProductD...vMk%252bXk82PQ%3d%3d

I'm not saying anything, just sayin'.

gunrunnerjohn posted:

Right Stan, and it's clearly not enough for most cases.

Where are the battery powered advocates when you need them.

In the prototype traction field, they do have such a thing with batteries

There are LRT cars which have batteries, so it can cross sections of trackage without an overhead wire.

PLCProf posted:

...

http://www.mouser.com/ProductD...vMk%252bXk82PQ%3d%3d

I'm not saying anything, just sayin'.

Well, that capacitor is 3" diameter by 8-5/8" tall...which is the size of a can of tennis balls.  And it costs over $90 each.    I'm not saying anything, just sayin'. 

And a can of Penn Extra-Duty Felt tennis balls is about $2 each at Costco.

This is a fun thread...

I have some of those tennis ball can sized caps laying about somewhere.  Great for high power car audio systems.  probably not much good for trains under the 12 inch to the foot scale.  

What I think would be a much more feasible option is to take what the battery power guys are doing and combined it with us live track guys.  Drop a tiny Li-Ion battery in the tender that can run the engine with all the smoke, lights and sounds for maybe 10-20 minutes, and charge it off track power.  Never have a dead spot again... But I'm sure that adding a battery would leave folks flipping their lids at one more part that needs to be replaced every 5-8 years.  

JGL

I don't see anything wrong with having a lithium ion battery, that can be charged by the track voltage.....as long as when/if the battery dies it does not damage the electronics as was done on MTH PS 1 when someone tried to run it with a dead battery.  Here is a thought:   have a "port" like on the old Lionel engines where the lithium ion battery can be taken out from underneath easily without having to take the body apart.  Perhaps a small enough capacitor that fits, with a lithium ion battery? 

Many years ago, Tesla (the man, not the car) was working on transmitting electricity by radio waves.......there is even a theory out there that says the pyramids did this? 

AMF posted:

I don't see anything wrong with having a lithium ion battery, that can be charged by the track voltage.....as long as when/if the battery dies it does not damage the electronics as was done on MTH PS 1 when someone tried to run it with a dead battery.  Here is a thought:   have a "port" like on the old Lionel engines where the lithium ion battery can be taken out from underneath easily without having to take the body apart.  Perhaps a small enough capacitor that fits, with a lithium ion battery? 

Many years ago, Tesla (the man, not the car) was working on transmitting electricity by radio waves.......there is even a theory out there that says the pyramids did this? 

Radio waves and electricity are parts of the electro-magnetic spectrum!

Having just learned what a capacitor does, I thought maybe I found the solution for a 263e that doesn't like to go through switches. For a split-second it loses power, activating the e-unit. I've cleaned the wheels, rollers, track etc. but nothing seems to help. If anyone has suggestions I'd really appreciate it. Thanks.

John

You could run the E-Unit on DC and add a large hold-up cap.  Another solution is to use a one-wire tether to the tender and add a pickup there.

many of the new DCC decoders out now in HO and O scale use have them in it and are advertised as keep alive. I have one in one of my On30 locos and it will run about a foot into a dead track before the capacitor runs out. if the loco is sitting when i shut the layout off the sound and lights last about a min. I think the BCR units to replace batteries in lionel and MTH are made up of these supper capacitors as well.

They do it all the time in HO, it's called Keep Alive. It could be done in O as well.

As described, Bluecomet400's "problem" is NOT how to Keep Alive the E-unit through the switch.  The E-unit is staying alive since it is advancing to the next E-unit position (presumably going into neutral).  His problem is the E-unit is interpreting the "split-second" power interruption as a conventional command to go into neutral.  So adding a capacitor to the E-unit to keep it running for longer during a power outage solves nothing.  He needs a method to extend the E-unit detector timing so it ignores the "split-second" power interruption.  Different animal.  The solution may indeed involve a capacitor but would take some study of the E-unit circuit which could get bogged down in detail, schematics, etc..

I like GRJ's suggestion of additional power pickups so the E-unit does not see power interruptions in the first place.

Well you could clean the track or fix the hot spots!

Another option is to lock the engine in forward. 

None of these are as much fun as trying to add a capacitor.

Charlie

stan2004 posted:

As described, Bluecomet400's "problem" is NOT how to Keep Alive the E-unit through the switch.  The E-unit is staying alive since it is advancing to the next E-unit position (presumably going into neutral).  His problem is the E-unit is interpreting the "split-second" power interruption as a conventional command to go into neutral.  So adding a capacitor to the E-unit to keep it running for longer during a power outage solves nothing.  He needs a method to extend the E-unit detector timing so it ignores the "split-second" power interruption.  Different animal.  The solution may indeed involve a capacitor but would take some study of the E-unit circuit which could get bogged down in detail, schematics, etc..

I like GRJ's suggestion of additional power pickups so the E-unit does not see power interruptions in the first place.

Stan I think it depends on if the engine is pre war or modern. A cap along with a rectifier will work on a mechanical e unit.

Bluecomet has to clarify.

Pete

Thanks for the help guys. This is a prewar 263e, never modified in any way. I'd prefer not to run a tether wire from the tender but it sounds like that's probably the easiest way. As a collector / operator, I like to keep my equipment all original, but also recognize that may not always be practical when it comes to running. Other locos run right through the switch, so the issue has to be with the 263e, correct? 

Thanks again

John 

The difference here is that O-gauge takes a LOT more power, so those super-caps would be pretty large to get the job done.  Also, the circuitry expects to see AC, there is a large warning in the Legacy manuals NOT to try to run on DC.  Many TMCC locomotives use triacs that also depend on AC.

DCS, OTOH, would probably be a bit easier to get running with a large supercap as it already handles DC on the tracks.

It's certainly "possible" to design such a circuit, the fact that it hasn't been done is probably suggestive of how large a cap it would take to be effective.

BlueComet400 posted:

Thanks for the help guys. This is a prewar 263e, never modified in any way. I'd prefer not to run a tether wire from the tender but it sounds like that's probably the easiest way. As a collector / operator, I like to keep my equipment all original, but also recognize that may not always be practical when it comes to running. Other locos run right through the switch, so the issue has to be with the 263e, correct? 

 

Many two-pickup locomotives exhibit similar issues over certain switches.  I routinely do a tether between the locomotive and tender to share the pickups.  Nature of the beast.  If you have the whistling tender with pickups, any single wire tether could easily be removed to return to stock.

Blue, how are the springs on the pickup rollers? When they get weak the pickup rollers will bounce around more.

Pete

in the DCC world they have capacitors for engines/ decoders now. Such as the KeepAlive from TCS. You can take the train off the tracks and place it on table and it will keep moving with lights and sounds for about 10-15 seconds before dying .

MU two or more powered engines to get across dead spots. 

stan2004 posted:

PLCProf posted:

...

http://www.mouser.com/ProductD...vMk%252bXk82PQ%3d%3d

I'm not saying anything, just sayin'.

Well, that capacitor is 3" diameter by 8-5/8" tall...which is the size of a can of tennis balls.  And it costs over $90 each.    I'm not saying anything, just sayin'. 

And a can of Penn Extra-Duty Felt tennis balls is about $2 each at Costco.

This is great.  I can use tennis balls to power my engines.  I don't have to worry about the battery power of the future or that Star Trek transporter system I keep reading about. 

But I am having trouble wiring them up.

CBS072 posted:

MU two or more powered engines to get across dead spots. 

They don't even have to be powered.  For diesels, put a one-wire tether to a boxcar or passenger car with a pickup roller to carry you over the dead spots.  For steamers, add a roller to the tender if you don't have one.  Lots of ways to skin this cat.

Here's a couple of tender installations of extra rollers I've done to cure this issue.  This is a commonly asked for upgrade once people realize the benefits.

Thanks John--great pics!! The search begins for some junk prewar trucks to modify for this project. 

Did you fab a custom 1/16" thick PCB?  Seems this might save other guys some time if you've done all the dimensioning to fit a specific truck/roller part numbers.

Actually Stan, I cut that out of 1/16" fiberglass, but it's a one-off.  Never even occurred to me to fab one.  I believe that's a Weaver brass tender that it's on, so it's something that does come along at times.

I am planning to add a pickup roller to the tender of my MTH Imperial Pacific Steam Engine (30-1682-1) and I want to make sure that I connect it correctly. Can I just connect it to the red wires underneath the gray wire nut (bottom left of picture below)?

Yes, but with one addition IMO.  Pick up a 2A TRIP PTC and put it in series with the added pickup.  That way if either the tender or locomotive derails and a roller lands on an outside rail, the current through the tether won't cook the tether wires.

Thanks for the quick reply. I will definitely add the PTC.