SP NG Diesel #1 (GE 50T) - Triennial or Bust

[senorgilamonster]

I was expecting a motor to arrive yesterday. When it didn't I discovered that I had made a mistake in the shipping address. Looks like I will have to wait another week.

In the mean time I made up a test jig for figuring out the trucks using old parts laying around and the new 7" wheels. Obviously the wheels haven't been gauged yet. New #40 roller chain is on the way for between the axles, but I won't order sprockets and chain for the actual motor drive until the motor arrives.

Harlock - thanks for the pix. That slide out, ride in cab really got me thinking (I measured my butt to make sure it would work at my scale). I can't decide if it is scope creep and how much I would mind the seam when it is closed...but I'm giving it serious thought. It does look like it might be a bit back heavy thought with my weight behind the back truck.

I was also aware of the RMI SP1...but they are waaaay to proud of it. And $35,000 is a suggested price, they reserve the right to charge your card for more than they invoiced you for, so not an option.

[0351]

About 5 years ago there was a Yahoo group Southern Pacific Narrow Gauge and they had Adobe drawings of sp1 on there, I haven't been able to find the group anymore so we'll see if I find it I'll post a drawings or a link!

The SPNG yahoo group is still up and they have some little giant info in the file section.
Has a drawing and some good pictures

https://groups.yahoo.com/neo/groups/-sp ... nt%20Info/

[Harlock]

Harlock - thanks for the pix. That slide out, ride in cab really got me thinking (I measured my butt to make sure it would work at my scale). I can't decide if it is scope creep and how much I would mind the seam when it is closed...but I'm giving it serious thought. It does look like it might be a bit back heavy thought with my weight behind the back truck.

Two thoughts for that - The Mesa SP1 is extremely heavy, which is why we can get away with it. You'd probably have to add weight somewhere.

Secondly, make sure you can get in and out of it. It's a bit of a monkey climb to get in the Mesa engine. A cab mockup would be useful at that point.

A cab side that swings out may be useful if it can be done fairly seamlessly from the outside.

I was also aware of the RMI SP1...but they are waaaay to proud of it. And $35,000 is a suggested price, they reserve the right to charge your card for more than they invoiced you for, so not an option.

I put it there for detail reference only. It's nicely finished.

Best,

-Mike

[senorgilamonster]

Traction Question:

I had assumed that I would mount the motor in such a way that I could run an additional chain between the two axles. By doing so I assume that I would get less slippage on starting under load and better braking. But, I also like the clean look of having the motors mounted between the wheels. The issue is that if I do that then there won't be enough clearance for the second chain linking the axles.

Does that second chain linking the axles really provide a benefit?

I think I could mount the motor above and to the inside of the drive axle and still manage to hide the motor under the cab floor since the cab floor is actually raised a scale foot (2.5" - more than half the motor diameter) thus still hiding the motor and have the second chain between the axles.

Feedback welcomed...

[Pontiacguy1]

You definitely want all of your wheels and axles powered, or you will be very disappointed with the locomotive's performance. You can put one motor on the truck and then use two chains, one to each axle, from the motor shaft. Somehow, someway, you have to get all of your axles powered, especially if you ever intend to pull more than just one car with you and maybe one passenger.

Rebuilt a diesel for someone several years ago, and it was only powered on the rear truck. That wasn't too bad, since at that time they sat on the cab of the locomotive to operate it, and the weight of the engineer was about 90% on that truck. Well, the owner didn't want to ride on the cab any more, preferring a small operator's car behind the locomotive with a comfortable seat. I told them that if they wanted to pull more than 2 passengers and 2 cars around with that locomotive, that the trucks would need to be rebuilt so that all the axles and both trucks were powered. I ended up doing that, and the locomotive is a very good, strong performer that will handle a decent train up a 2 1/2% grade. Would never have done that if it was only powered on the rear truck.

In this hobby, traction is almost always the limit to what your locomotive can pull. The more grip you get, the better it will pull. #1 thing is to have all axles powered. Then you can add weight later if you think your locomotive has enough power to do so, and you want to pull more.

[Soot n' Cinders]

In this hobby, traction is almost always the limit to what your locomotive can pull. The more grip you get, the better it will pull. #1 thing is to have all axles powered. Then you can add weight later if you think your locomotive has enough power to do so, and you want to pull more.

I'll agree with this. Traction is almost always the issue with pulling trains in this scale is traction. Having done some numbers for several steam locomotives, the factor of adhesion is almost always too low. The Little Engines Atlantics and Pacifics have the same drivers and cylinder block, but the Pacifics are the better pullers because they have extra weight the Atlantics dont have which gives them a higher factor of adhesion.

[Harlock]

Yep, don't go for anything less than all-wheel-drive. You'll regret it quickly. You may be able to find a motor that would leave enough room for the chain. I have a very powerful pancake motor in my speeder that is very short. 950W 24V. Zoom zoom.

[Harlock]

Here's the super powerful pankcake motor I have in the speeder: http://www.monsterscooterparts.com/trsc ... ocket.html If you put two of those in and the weight to support it, you'll be able to pull anything. Put four deep cycle marine batteries in it.

If the motor body diameter will work for you, the length will leave plenty of room for a chain inside the wheels.

The main issue is how to gear down enough for a typical electric motor, all within the confines of a truck. On the speeder it's chassis-mounted and two rigid axles so plenty of room, but trying to do the gear reduction inside of one truck is a bit tricky. I had to do a double reduction using a jack shaft to go from 2600 RPM max on the motor to a ratio that would give me a top speed of around 7 MPH on the level. Or were you looking at a motor with a built in gearbox?

If as you say the truck can be tall with part of it hiding above the floor, there is room to work.

[senorgilamonster]

first - thanks for all who have responded. I think that this is where my lack of high school physics is finally going to catch up with me. In my brain hp/wattage = how much I can pull. Volts = how fast & Amps = how much load, gearing how much torque. Somewhere I knew traction would come into play...

My only reference point is my first (and only other) loco which had a 1/2 hp motor and two 12V deep discharge 50A (ea) batteries in series. I never did find out how long it would last because I never ran it remotely long enough to drain the batteries. It did pull itself, my steel gondola, my caboose + 3 adults with ease. No idea how much more it would have pulled before slipping.

Thanks Harlock. I didn't know that pancake motors came that high a wattage.

Back to truck design. Before butchering up some metal I decided that I should make a mock up of the design full size. I cut a piece of plywood for the side frame the the other piece on card stock. I have already purchase 8' of 1/2" x 6" steel plate for the side frames and don't plan to rip 1/2" off of it. So in looking at the plywood mock up I think that I will move all of the cut outs up towards the top 1/2". I think it will look a bit better and closer to the visual appearance of the prototype.

[Pontiacguy1]

What diameter are your wheels? If you have a 5" diameter wheel and want to have a max speed of 7 MPH, you'll need to be turning 470 RPM at the wheels. If it were me, I'd shoot for 500 wheel RPM maximum, which is about 7.4 MPH. If you have a 2600 RPM motor, you'll need a 5.2:1 gear reduction. I'd probably just shoot for about 5:1 or somewhere close to that, which would make your top speed somewhere just north of 7.5 MPH. If you use a 900KW motor on each truck, you'll have plenty of power with that gearing, even if your locomotive ended up weighing 500 or 600 pounds.

Good luck with it. With those big side frames, you should be able to fit a pretty large motor in there.

[Harold_V]

If you use a 900KW motor on each truck, you'll have plenty of power with that gearing, even if your locomotive ended up weighing 500 or 600 pounds.

900KW?
Likely a typo. I expect it should read 900 watts.

H

[Harlock]

If you use a 900KW motor on each truck, you'll have plenty of power with that gearing, even if your locomotive ended up weighing 500 or 600 pounds.

900KW?
Likely a typo. I expect it should read 900 watts.

H

You could go back to 1955 and visit your parents with 900KW!

But seriously, the motors are 900W @ 24V which is 37.5 amps. If you go that route with a pair of them, you'll want a 100A controller, or two 50A controllers ganged together. I use a bare SyRen 50 for my one motor. Roy at Ride Trains sells them with a daughterboard that adds sound and some safety features, like power-on throttle lockout. http://ridetrains.net/sound-light-motor-control-2.htm

There's not much to it. One tiny board with some small caps to dissipate whatever leftover energy it can't pipe into the motor or back into the brakes with the regen braking. Unlike controllers of yore, it does not simply vent off the extra power as heat. Very efficient.