12" working railroad

[tomc]

it has an Onan 22hp twin coupled to a Eaton model 7 pump chain coupled down to the truck drive shafts. If we did another, a pump and motors would be our way to go also.

Tom C.

[rkcarguy]

Thanks for the link to the proper valve Tom, after initially viewing those, I was confused as to the function of the open center valve compared to the regular one, and also, how immediate, or slushy, the stop might be when put into neutral being I'm going to be geared for just over 5mph top speed. I do wonder if I could modify the open center valve with a restrictor such that it would offer a slow "wind down" instead of just free-wheeling or locking the wheels up?
Like a "restricted" center valve:)

[rkcarguy]

Ok, looks like after some research I can't modify the valve, but I could put a flow control valve inline with the motors and have "hydraulic dynamic braking". It appears I could just find the maximum flow restriction I'm happy with and add a stop to the lever only allowing a certain amount of braking.
The only hole I can shoot in this, is that in one direction the flow control would be on the pressure side, and the other it would be on the vacuum side....potential cavitation?

[Steggy]

Thanks for the link to the proper valve Tom, after initially viewing those, I was confused as to the function of the open center valve compared to the regular one, and also, how immediate, or slushy, the stop might be when put into neutral being I'm going to be geared for just over 5mph top speed. I do wonder if I could modify the open center valve with a restrictor such that it would offer a slow "wind down" instead of just free-wheeling or locking the wheels up?
Like a "restricted" center valve:)

You need to bone up some on hydrostatic propulsion before you make any design decisions.

Quickly summed up, a hydrostatic propulsion system consisting of reservoir, pump, reverser valve and motor(s) is the fluid analog of gears and shafts. When the valve is set to one of the two propulsion positions, the motor speed is in direct proportion to pump speed (minus some small losses due to internal blowby). As the pump is mechanically driven by the prime mover, your locomotive will tend to slow down when the prime mover is slowed down, producing a form of engine breaking. This feature is usually sufficient to control speed on a downgrade.

That said, it is bad practice to rely solely on the propulsion system for braking. A blown hose, pump failure, broken roller chain or engine failure while on a grade may result in a loss of control. Your engine should be fitted with adequate brakes that are independent of the propulsion system.

BTW, who was the "Tom" mentioned in your post?

[rkcarguy]

Maybe I'm not understanding this right. So if I am running along in forward and bring the gas engine down to idle, I'll still be "engaged" and the train can't run away. Once I switch to neutral though, the fluid is free to circulate through the motors and valve, and the train would coast downhill on it's own, with some speed losses due to fluid movement? If this is the case, I just think the control valve would be neat to add as a "dynamics function" and they are only about $50 for a lever type one.
Yes I totally understand the safety aspect and plan on having multiple braking systems. I have no wish to hear a loud thump in the night to find my train went down the hill and piled up in ruin at the bottom, or worse yet, while I'm on it. To start with I'm going to be running a couple rear disk brake calipers and disc's, one on each of the locomotives trucks, and be able to use a parking brake setup on them as well as the hydraulic side. Then as I start adding rolling stock I'm going to incorporate a Viair 12 volt compressor and add air brakes to everything.
I was looking at the design of the real thing, and I think I can drill extra holes in the truck sides and actually fabricate some brake shoes and linkage that will clamp on the wheels if I can find some brake pad material I can rivet on.
I actually had some progress today. The 1" axle shaft material and 80' of flat bar "rail" showed up today, and the shop also cut my truck sides from the 6" channel and they turned out really well. We have a beam line at work and this thing is amazing, it drilled the 4 holes for each flange bearing, the axle clearance holes, milled the slots for the springs, and the two 3/4" holes that will bolt in the "bridge" between the sides(I'm doing this a little different than a regular truck design) in about 5 minutes a piece!
I cut the axles to length, de-burred the ends and test fitted them into the bearings, they slide in nicely I'm very happy with the fit. FYI the bearings I'm using are a UCF-205-16.
I also cut 4 lengths of "rail" to 10' long, and will start making a 10' section of track this weekend to build my locomotive on.
A question for you guys, is there anything bad about building the track in sections with the rail joiners at the same place, much like sections of train set track? I designed my joiners to be double bolted on each side and from the same material, so there shouldn't be any weakness at the joiners.
I was just brainstorming a bit on grooving the 2x4's, and instead of using the table saw I think I'm going to make a fixture that I can insert 4 ties into, and run my skill saw through them in a row, up against pieces of metal stock lag bolted to the top of the fixture as guides. Saw back and forth a few times on each side and bam I've got 4 ties.

It's getting to be time to start looking into wheels, and I have a couple options. Full scale 40" wheels come out to 6.67" at 1/6th scale, 6" extra strong pipe has an o.d. of 6-5/8", and a wall thickness of almost 1/2". Work has a chunk in the scrap bin at the moment. I can get some 3/8 plate circles laser cut for the flanges, weld on slices of pipe, weld those to the axle, and then turn the whole thing on our lathe. OR, I can get some 1-1/4 solid plates burned out and machine them as one piece. I think this is more expensive and the hardened burned edges are going to be hard on the lathe and tooling and take a lot of time to turn. I had been thinking about keying the wheels to the axle and have the gage adjustable, but if I was to run on a 7-3/4 gage track I think my flange profile would be too large anyway, so I'd probably just make another set of wheels/axles in that case.
FYI I have an OLD version of autocad LT, so I can draw parts, send the files to a local laser cutter, and for stuff that I'm not in a hurry on they will patch in my part wherever they have space when running the same plate thickness for other jobs, and the prices are very reasonable this way.

[Steggy]

So if I am running along in forward and bring the gas engine down to idle, I'll still be "engaged" and the train can't run away. Once I switch to neutral though, the fluid is free to circulate through the motors and valve, and the train would coast downhill on it's own, with some speed losses due to fluid movement?

That's correct.

If this is the case, I just think the control valve would be neat to add as a "dynamics function" and they are only about $50 for a lever type one.

You could do such a thing, but it's not something I would do, nor do I think it's even necessary. For one thing, you will probably find it difficult to properly control. Also, inserting another valve into the piping will increase losses, meaning more power will be expended just in pushing oil around. Furthermore, while in motion you should not disengage propulsion except in an emergency, which means there would be no good reason for having such an "anti-drift" valve—it would be redundant.

Yes I totally understand the safety aspect and plan on having multiple braking systems...I'm going to be running a couple rear disk brake calipers and disc's, one on each of the locomotives trucks, and be able to use a parking brake setup on them as well as the hydraulic side. Then as I start adding rolling stock I'm going to incorporate a Viair 12 volt compressor and add air brakes to everything.

Your braking system should be the primary means of controlling the train's speed on a downgrade. Propulsion system drag should be secondary. Having adequate compressed air to operate the brakes is your best bet.

I have pneumatic disc brakes on my F7 and its control car. The air compressor is driven from the accessory end of the locomotive's prime mover and hence runs whenever the prime mover is running. That design assures there is plenty of air available at all times. For safety's sake, the control car has an auxiliary reservoir that is charged from the main reservoir via a check valve. If compressor failure occurs or a hose blows on the locomotive the auxiliary reservoir will stay charged with enough air for several brake applications.

[Glenn Brooks]

Making wheels out of pipe and welding flanges might work. Certainly mining car wheels, and trench Railway (60"cm/24" ga) rolling stock in WW1 used such a design - although the wheels were cast as one piece. Eccentricity will be a big issue with fabing wheels. Particularly with welding stresses. Cutting 1" plate, or 1 1/2" plate with waterjet process will give you wheel blanks that doesn't have the hardened edges caused by laser or flame cutting. You could always make up a set and experiment before committing to such a design.

Regarding rail: what size flat bar do you anticipate making track? The style you describe has been nicknamed 'groovy track' some years ago, and a few people tried it out. Never caught on very well. You could easily use standard live steam class 1" aluminium rail in lieu of flat bat, and have a very acceptable and long lasting track system. Check out discover live steam for used rail. It shows up fairly regularity. Also there are several new rail suppliers around.

Also, regular 12# steel rail is often cheaper than the new 1/6 scale aluminium rail.

Glenn.

[rkcarguy]

I'm using 3/8x1 steel flat bar, with 2x4 ties 6" center to center so there will be lots of support. 80' of flat bar was $55. Using steel is important to me, because I have my own Millermatic 250 at home I can weld, splice, build my own switch frogs, and so on. I also find it to be fairly to scale for yard rail, aside from lacking a rail shape of course. Where I am deviating from the groovy track style, is I am going to weld on washers and screw the rail to each tie as well as having the groove. I think I'll alternate inside outside to assure the rail doesn't pull one way or another with use. I think this will make things pretty bulletproof and once I get some fixtures set up it will go pretty fast.
I think you are right Glen, I'll try a test wheel, just a scrap of whatever size pipe welded to a circular center drop and see how it goes. What I do is use a pair of calipers to get the parts centered within a few thousandth's, then clamp, tack, and weld up. The important part is you don't just start welding and go all the way around. You weld say 1" of weld, then 1" opposite, then turn the wheel 90* and repeat, and so on, until the weld is complete. There will always be warping with welding, but it will be uniform with this method and I would expect not to have to turn off much more than 1/32nd to get things to true up. I have found the laser cut edges to be pretty friendly on tooling, in fact on several jobs we've had them cut the holes to some pretty exacting sizes and tapped them.

[rkcarguy]

I would say the groovy track didn't catch on well for several reasons:

It requires tools to cut and work with steel. Carbide tooling on wood working tools will go through aluminum like butter and is much easier for the average person to deal with.
Generally I don't think most people have a welder.
I would bet that over time, the flat bar rails would start to lean outwards as the grooves in the ties wear.
With nothing to secure the flat bar, I could see it popping up out of the grooves on hot days or working up/down as the train passes.

Btw, that was a pre-coffee oops, I meant 1/64th, or about .015". If I'm off by .030" I've messed up.

[rkcarguy]

Another question for you guys. I've found some 5" phenolic castor wheels with bearings that are $6 a piece, and they have enough meat around the rim portion that I could easily turn them on the lathe so they had a flange and use them for my "light duty" wheels. I also like the idea that they have their own bearings, and would likely incur less wear on curves(solid axles/wheels will want to go different speeds around the curves and scrub speed/wear). Think these would wear ok?

[Harold_V]

I would say the groovy track didn't catch on well for several reasons:

I'm not the right person to address this comment, as my experience is based only on visits to groovy tracks, but I've been to two clubs where that's what is in use, and they've been in existence for many, many years. To my knowledge, it works just fine. In both instances, the bar stock track simply fits in a snug groove, with no other type of restraint. It offers one real advantage---the track can't go off-gauge, although I don't know that that is an ongoing problem with scale prototype rail. If hot rolled bar is used (not cold rolled), there's generally one corner of the material with the desired radius.

H

[rkcarguy]

That was my thought, that the steel flat bar would last longer and once my "empire" is built I'd be limited to replacing ties as they rotted.
I am using hot roll for that exact reason, it has a bit of a radius on the corners where the cold roll is pretty sharp.
I got some flat bars from the scrap bin and sheared them to length for the guides for my saw fixture, I'll work on that tonight and hopefully get it adjusted to quickly produce good ties.