F3 drive identification

[Caribou Doug]

Does anyone recognize this drive system? It is a 12 horsepower gas engine that drives 3 automotive alternators which power 2 motors on each truck... Has anyone ever seen anything like this?

[Steggy]

That unit appears to be an F7, not an F3.

[ccvstmr]

Doug...I'll ditto BDD's comment about the loco ID...it's and F7. Don't think that's the question you wanted to ask.

The frame and body look like an old Backyard Rails loco. Can't be sure without seeing the trucks. The side frames are cast, rigid polyurethane and are simply "window dressing". The truck frame and axles are totally independent of the side frame decorations. However, don't believe the power plant is Backyard Rails. I would guess it's a home grown "gas-electric" set up...with the gas engine spinning alternators to charge the battery from which axle mounted DC motors are powered for propulsion. There are perhaps several locos using similar technology. There's a CB&Q Zephyr in the Chicago area running with that type of set up.

Hope that helps. Otherwise, you need to be little more specific about what you're trying to find out. Carl B.

[Harold_V]

I would guess it's a home grown "gas-electric" set up...with the gas engine spinning alternators to charge the battery from which axle mounted DC motors are powered for propulsion. There are perhaps several locos using similar technology.

Hmmm. Makes me wonder if, maybe, the engine isn't battery powered, but that the alternators drive the motors directly, using a rheostat to excite the alternators. If not, has anyone built anything like that? Seems like it would work well enough.

Harold

[Erskine Tramway]

I would guess it's a home grown "gas-electric" set up...with the gas engine spinning alternators to charge the battery from which axle mounted DC motors are powered for propulsion. There are perhaps several locos using similar technology.

Hmmm. Makes me wonder if, maybe, the engine isn't battery powered, but that the alternators drive the motors directly, using a rheostat to excite the alternators. If not, has anyone built anything like that? Seems like it would work well enough.

Harold

Hi Harold.......

As I understand it, the gas-electric drive using alternators was developed in Australia. In the UK, Colin Edmondson uses that system on several of his 7-1/4" gauge designs. The motors are regular DC motors.

Mike

[Harold_V]

Interesting, but the real question is, are batteries involved, or do the alternators drive the motors directly, speed being controlled by exciting the alternators? I expect that's the case, but is it? If one small battery (for starting the gas engine) is involved, that would nicely answer the question.

Harold

[Erskine Tramway]

Interesting, but the real question is, are batteries involved, or do the alternators drive the motors directly, speed being controlled by exciting the alternators? I expect that's the case, but is it? If one small battery (for starting the gas engine) is involved, that would nicely answer the question.

Harold

I'll have to hunt around for the exact details, but I know the only battery involved is a starting battery. One of the alternators in the photo is for charging that battery, and the other has its wiring modified internally as the traction power. As I recall, the voltage regulator is 'cut out' to allow the alternator to generate more than the 'standard' 13-14 volts used for battery charging. Colin designed a mechanical control that combines the engine speed and excitation onto one handle.

Mike

[Caribou Doug]

Guys, my mistake on the F3 /F7. For some reason I had F3 stuck in my head and likely not thinking clear after some extensive work hours this week.
thanks for all the replies and clarification. UPDATE; After some cleaning of the kohler engine fuel system, fuel tank, fuel pump and carb, and replacing the 2 12 volt motorcycle batteries, I hit the start button and the gas engine fired off to a smooth idle without issue. I let the cobwebs clear out and ran for about a minute checking to make sure there was no glowing from what seems like about a mile of wiring. After shutting the gas engine off and re-inspecting oil level, fuel lines and belts, I fired her off again. I increased the kohler rpms and brought it back to idle several times without any issues. I then used the pendant and selected a forward position and increased the rpms again with no response from the four electric motors on the trucks. I then noticed a switch on the locomotive that had two positions Start/Operate. Once I switched to the operate mode all four motors started driving the axles when the gas engine speed increased. I had the trucks jacked up and resting on wooden blocks so the locomotive would not move. When I decreased the gas engine to an idle, the axles all stopped. Both forward and reverse seemed to operate normal and behaved the same way. I had been told that the locomotive had been sitting for four plus years so I was surprised everything seemed to operate. I am unsure about how increasing the gas engine speed actually changes the speed of the drive motors (I am not an electrical engineer, just a train engineer) but I am sure at some point the mystery will be solved. I am not sure that the axle motors are driven from the batteries on board as they are small motorcycle batteries and seem quite small. I would have expected larger deep cycle batteries if that were the case. I will be working on getting the locomotive on some track soon and will provide an update as soon as available.

[Marty_Knox]

The March-April issue of Australian Model Engineering has an article on using automotive alternators for traction power. I just happened to pick up this issue to read while I was in the 'library'.

[Caribou Doug]

UPDATE:

I had the opportunity to take the locomotive to the track today for a quick trial. After unloading the loco and riding car, I fired up the single cylinder Kohler engine and let her warm up for a couple of minutes. I switched the mode control from start to operated and switched into the forward position on the pendant control. I slowly increased engine speed and she sluggishly moved forward about 100 feet. I switched the direction to reverse and returned about the same 100 feet. After some visual inspections, I kept going forward and reverse increasing the distance each time without any issues. After about 15 minutes of motion I shut the engine off to check belts and noticed a small leak in the air brakes. After tightening several clamps and resolving the air brake issue I decided to give her a go again. Upon starting up it seemed to be responding to throttle speed more without the sluggish start. I have a RR Supply SD-35 Gas/Hydraulic that responds instantly when pushing the forward reverse lever so getting used to an electric drive took some time. Overall it seemed to have acceptable response and good power. When approaching any type of grade there was a different feel as it seemed you had to rev the engine prior to getting to the grade to keep the speed in the same range. We added several riding cars after about 30 minutes of running and she had no issues pulling even up the grades. When we added some passengers, you could certainly hear the whine of the alternators a little more. Once we reached the first grade, I needed to apply a little more throttle and the was a slight delay (2-3 seconds) before she increased speed. On the longest grade, the alternators whined even louder but there was NO issues with power, she really got up and went. It reminded me of driving my GMC turbo diesel truck. I never opened the throttle all the way as the speeds achieved at lower throttle were plenty fast enough! Overall I was pleased with the performance of this locomotive and I hope to get her back to the track soon. There are several minor things to be repaired (Forward/Reverse switch, brake adjustment, lighting etc.) but nothing major. Her are several pics of her with the cover on...and one with dad..

Doug

[ccvstmr]

Doug...it sounds like whoever designed the loco controls was trying to achieve operation as close to prototype as possible. You already noticed that your mechanically driven gas-hydraulic (hydrostatic) SD-35 responds instantly to speed/direction control lever changes. Not so with electrical transmission locomotives.

If you've been following the F-7 build series posted by Big Dumb Dinosaur...he tried to simulate prototype loco operation using a gas-hydraulic drive...with a fluid coupling between the engine and hydraulic pumps. But the response is nearly the same. After releasing the brakes, you can "wipe" the throttle to notch 8...the engine revs up...and the loco starts to speed up slowly. Once the train is up to speed, you notch the throttle back. The engine speed drops...but the loco continues to coast. It's an interesting piece of machinery for sure, but very much like real locomotive operation.

Congrats on your first true test run! Despite the few little improvements you have planned, it sounds like you got yourself a nice working piece of equipment there. This is the type of operation most railroading hobbyists are not used to. Let me ask...what kind of brake controls do you have? Sounds like "straight air"...but do you operate a pressure regulating brake valve to control the brakes? ...or electrically operated "brake on/brake release" pushbuttons. Just curious.

Lastly, are you going to keep the current body paint scheme or repaint? Don't see too many B&O painted models around! Congrats on this addition to your motive power roster! Carl B.

[Erskine Tramway]

Doug....

I'm glad to hear the loco is working well. As noted above, that's just how the big ones work. You 'give her a notch', the engine revs up, the power comes up, and you start moving. That was always what I didn't like about hydrostatic drive, it doesn't 'feel' like the big ones, and it won't 'drift'.

Mike