steam train charge/lighting system conversion to solid state. - Page 1
Forum section: electronics / projects

author: m3vuv
author_rank: Super Contributor
timestamp: May 27, 2019, 11:44:36 pm
content: hi all ive been asked to look at converting some railway carriages from a electro mechanical charge/lighting system to solid state,any ideas?,find attached info.,thanks in advance m3 vuv.

author: Cyberdragon
author_rank: Super Contributor
timestamp: May 28, 2019, 01:10:35 am
content: Why? Don't fix what ain't broke. The whole trend of "modernising" stuff is often causes more trouble for little to no benefit. The system is very simple, and if properly maintained is quite reliable. There are plenty of old steam trains running with original electrics (save for some new wiring).I suggest consulting some steam experts on how to maintain it properly.

author: dmills
author_rank: Super Contributor
timestamp: May 28, 2019, 01:13:21 am
content: I would be thinking that an off the shelf 24V lorry charge regulator would probably get it done, why reinvent the wheel?But yea, the original if cleaned and lubricated correctly (NOT WD40!) is probably quite satisfactory.Regards, Dan.

author: m3vuv
author_rank: Super Contributor
timestamp: May 28, 2019, 02:25:28 am
content: its not for me to ask why they dont fix the original regulators,they run a fleet of 1950's steam trains,and as far as i know want to modernise the electrics on the carriages,ive just been asked to do it.most charge controllers ive seen for lorrys are for alternators.

author: floobydust
author_rank: Super Contributor
timestamp: May 28, 2019, 03:14:29 am
content: The design looks like something Lucas used in the 1950'sIt's using a 70A or 125A 24V dynamo for lighting? What size batteries? I wonder how many hours the lights are designed to stay on when the train is stopped - if you could downsize things. LED lights would use much less energy.You could put in an electronic regulator, instead of the 5 relay antique technology. I haven't seen any schematics with low voltage cutout and that are reasonably efficient at charging at low speeds.If the dynamo is something you can maintain, I would say keep it. Alternators need much higher shaft speeds so the pulleys would have to get changed.

author: Cyberdragon
author_rank: Super Contributor
timestamp: May 28, 2019, 03:26:33 am
content: Quote from: m3vuv on May 28, 2019, 02:25:28 amDo they also want to convert the headlight to some ugly cold white LED and install an oil burner so they don't have to shovel coal?Unless these trains are carrying passengers on regular shifts I see it as pointless. I thought steam enthusiasts were about keeping things authentic. Steam trains are high maintenance machines, if they can't be bothered to care for a few relays it makes me wonder how often they keep everything well oiled...

author: floobydust
author_rank: Super Contributor
timestamp: May 28, 2019, 04:22:18 am
content: Quote from: Cyberdragon on May 28, 2019, 03:26:33 amThey just finished the restoration onBig Boy No. 4014. Converted from coal for obvious reasons...It uses electric lighting, incandescent. Looks like 125VDC E27. No schematic though.Let me know how you would troubleshoot/adjust the regulator's relays without a test drivehttps://www.9news.com/article/life/style/colorado-guide/big-boy-locomotive-completes-five-year-restoration/73-59f168c8-6abf-4e0b-9d12-9034fca431af

author: Cyberdragon
author_rank: Super Contributor
timestamp: May 28, 2019, 04:48:53 am
content: QuoteYou read the manual (which clearly no one does these days)...which clearly states if it's working, don't mess with it, and if it breaks what the most likely causes are. People these days don't know how to maintain stuff, they just toss their stuff out when it breaks or gets too old...Something tells me there are no transistors in the Big Boy (outside some coms radio). If there is, I'll vomit.

author: m3vuv
author_rank: Super Contributor
timestamp: May 28, 2019, 04:54:57 am
content: Im going there next week,,ive just been asked to look into it for nene valley railways,the chief tech/engineer there is a friend of mine,as far as i can tell the control box/regulators are forever playing up,not suprising when you think some of the stuff is 100yrs old,testing could be interesting as as far as i know the dynamo is belt driven from the axle,i was thinking maybe using a modern ss 24v alternator regulator to power the field windings,shall know more when i get to see in the flesh what im working with,i dont know if each carriage has its own batterys/dynamo or what yet.

author: Cyberdragon
author_rank: Super Contributor
timestamp: May 28, 2019, 04:58:46 am
content: Have you tried scraping the contacts with sandpaper and cleaning spray?

author: m3vuv
author_rank: Super Contributor
timestamp: May 28, 2019, 09:21:57 am
content: ive not been asked to fix it!,they want to find a cost effective way to convert the controll system to solid state to make what they have more reliable.

author: dmills
author_rank: Super Contributor
timestamp: May 28, 2019, 07:32:53 pm
content: Measure the field current with the thing running (Wire in an ammeter before starting), as that value for normal field current will be quite important.I would guess that a CAV style 24V automotive regulator might get it done as far as the regulation side goes, with maybe some butch mosfets to do the switching and deal with shutting down when shaft speed is too low.The trick is to build it all into the original housing.BR used to run quite a lot of this kit (you would see it on the underside of things like mail cars) up until at least the 90s, so spares should be fairly available.Regards, Dan.

author: floobydust
author_rank: Super Contributor
timestamp: May 28, 2019, 07:59:20 pm
content: Quote from: Cyberdragon on May 28, 2019, 04:48:53 amYou just set it up and leave it alone for years I think is naive. I did read the tech doc on the system- there's no capacitors to lessen contact arcing, the dynamo has four brushes, a "regulator piston" - it's a mechanical beast prone to wear and would need constant service. I wonder if you can get parts.I think one huge problem is troubleshooting is very difficult, as the manual says retreat back to the locomotive service center and just swap out the dynamo or regulator.It would be cool to see pics of this system.OP don't let your client/customer tell you how to fix things without first doing your homework.Given the time the steam locomotive is parked, the batteries simply might not have enough energy to keep lighting going, compared to the brief charging time when it's being driven. It could be chronically starved and modernizing to LED's and such will not miraculously cure those ails.

author: soldar
author_rank: Super Contributor
timestamp: May 28, 2019, 11:33:41 pm
content: Replace with LED lights, new batteries and solar panels. Totally independent of old system.

author: m3vuv
author_rank: Super Contributor
timestamp: June 07, 2019, 04:26:21 am
content: well ive found this,looks like it should work ok,theres a pic of one ive built,got to go and fit it next week.

author: m3vuv
author_rank: Super Contributor
timestamp: June 07, 2019, 04:27:50 am
content: heres the schematic.

author: floobydust
author_rank: Super Contributor
timestamp: June 09, 2019, 03:29:08 am
content: I think it will get quite hot. Make sure the 2N3055 is sitting flush on the heatsink, it looks caught on a lip. What is your field winding resistance?The circuit design seems for a 9R field and I could not get more than 2A happening. Transistor power dissipation is 14W at 24V and 21W at 28V so it will heat up. If that is a stud mount diode, it will make a lot of additional heat.I found pics of dynamo and regulator test stands. It might be worthwhile to run it there.Dynamo test rigshttp://www.gw-svr-a.org.uk/frankenstein.htmlhttp://www.gw-svr-a.org.uk/kidderminster_works.html

author: m3vuv
author_rank: Super Contributor
timestamp: June 10, 2019, 01:00:20 am
content: luckily they have a test rig,heat is a concern,i may use a bigger heatsink with fan cooling,im there on wed so will find out.

author: David Hess
author_rank: Super Contributor
timestamp: June 10, 2019, 03:17:34 am
content: So they want to keep the existing shunt wound generator and convert the regulator to solid state? Oddly enough, I did that once with a Pinto because the electro-mechanical regulators you could buy became so unreliable. The look on my neighbor's face when he saw me with an oscilloscope and impedance bridge hooked to my car was worth it.It basically comes down to modulating the field current to regulate the output. Lots of switching regulator controllers can do it (I used a 78S40 the first time) and now probably some integrated switching regulators but it will require detailed design to replicate all of the functions of the original circuit.You might be able to find a simplified circuit intended for cars from the 1960s and 1970s. Something basic could be done with a zener diode and some bipolar transistors if you wanted to do a fully discrete design.