Increased car body, increased tonnages, recalculations, lumbar support, CAN bus masters

So, when I had decided I was going to make my stock dual gauge, 7.25" and 12", I had nominally increased the car body width to 600mm. And yes, that is indeed suitable for the Casino layout, despite being 100mm over the AALS interoperability standards.

However, I run into this, when I got myself a present of a 2m baby tape measure:

The 20L drum I was going to use is only 300mm wide, which would be dwarfed by the 600mm car body width. The "clap boards" under the rotating drum would be disproportionately huge, and angled totally wrong to allow easy unloading without a shovel.

I had to come up with a better solution. The problem was, I would have to increase my per-wagon tonnage.

Add to this, I had gotten the density constant for the sand wrong. I had used a constant of times 1.44. When I rechecked the site I had done the calculations at, not only had I gotten it wrong, I noticed an option I hadn't before - "Sand with gravel, wet."

The density constant of wet sand with gravel through it is times 2.02. So assuming a 100L plastic drum can carry a nominal 100kg of water, multiplying 100kg by the constant of 2.02 equals 202kg weight of load. Round that to 250kg for each wagon, four wagons make a tonne loading.

A 100L plastic drum is 445mm diameter, by 800mm tall. The wagon would need to be 1,000mm long at least, and would best be a bogie wagon to allow operation on tighter curves. This, however, forces the costs per the wagon through the roof, especially considering I have to have most of the parts custom made. At some point, a laser cutter and CNC mill of my own are on the agenda.

Now, the problems with my back are no secret, my lumbar, ie, the lower back, is twisted, and even since I hurt it at Wards River, I have been in constant pain pretty much. I was thinking about assisted support, but it come to a head when Glen said "My recommendation to you is Gauge 1 - anything larger, and you can't physically move it, and hired help is not able to get it right..."

I beg to differ on both points.

While I'll need to be careful with my back, and certain activities I physically won't be able to do, I am able to assist my lumbar with a powered supporting brace, like a wearable robot. Don't ask me the price, but I will find out soon enough:

http://www.cyberdyne.jp/english/products/Lumbar_LaborSupport.html

If I have to go to full leg support later, I just will do it. I'd like to be able to operate my trains.

Note the name of the company - Cyberdyne Systems. As in Terminator. Cyberdyne was also featured in the Aliens novels, which is today's piece of pub ammo.

I noted an ex-worker of Cityrail was laid off when she failed a medical, the railways stipulating that her oesto-arthritis in her knees and hips affected her ability to walk on ballast, leading to the fears the damage incurred could give her cause to sue on OH&S negligence. My own railway will be earthen ballast, at track level, allowing a mower to run over it easily, so if there is any concerns that walking on actual ballast would aggravate my back problems, it simply won't happen with at grade earthen ballast.

That gives you the general idea of what I'm thinking.

So, with all of this in mind, I now have a 4.6 metre long train, at one tonne, with four wagons, but the wagons are considerably more expensive due to the need to construct dual gauge bogies. The superstructures will remain wood, perhaps with some metal bracing/ framing. Add a tonne and a half for the loco and brake van, and that's a 12 metre or so train at two and a half tonnes weight.

Hired help? I'm quite articulate and detailed with my needs and specifications, I'm used to explaining to various tradesmen what I am requiring, I've made a damned good foreman in my time, never paid for it, but I am able to run a worksite, or a radio operations centre, just as easily as one another. I would incrementally test the tradesmen, the next issue is cost. Looks like I'll have to earn some money, right? I was going to get Casino Engineering to make me up a track welding jig in any case, so I'll start getting an idea of wha this will all start to cost me soon enough.

Speaking of being articulate with needs and specifications, I emailed Benjamin about the details of the VESC programming I was needing. However, the VESC being open source, I can just look at the source code, and examine it myself. I have this great start, I imagine a stub in the traction control section to run a custom program to pulse the pin to activate the sand blower under the wheel as it slips would be the ticket here:

http://vedder.se/2015/08/vesc-writing-custom-applications/

I don't normally program in C, but I know enough to get myself into trouble.

MU (multiple unit) detail:

http://www.railway-technical.com/muops.shtml

Rather than needing a "cross over" the insertion of a MU jumper cable will signal the Arduino CAN "Master" which serves as local throttle and reverser. According to this quote:

"

0. The Controller Area Network (CAN) bus is a multi-master message broadcast system that is suitable for systems where data contained in short messages are needed to be received at multiple locations simultaneously. Because messages are sent to all the nodes in a system, CAN is especially suited to systems where consistency in the received messages at all the receiving nodes is needed 

"

Source: http://www.ti.com/lit/an/slla159/slla159.pdf

The CAN bus is a multi-master bus, meaning the "Slave Mode" of the VESCs is higher up in level on the OSI model and can easily be programmed for. Again, the source code, and thus, protocol, is open, so I'd be able to craft up a control scheme using a "Master" controller per chassis, but each "Slave" VESC will defer to any Master, and if any Master signals them (within reason, there needs to be a time delay, so two locos can't literally be commanded to pull apart if someone was riding in the second units cab, then again, possibly a key to put into the controller as a token?) the VESCs will Dial-A-Power and all that. I'm thinking I might make electro-pneumatic wagon brakes to compliment the independent and regenerative brakes on-loco, based on CAN bus. Once again power will be passed through at +24VDC, and a set of two small 7.2Ah SLA batteries hooked up in series will save the day.

I use those two on long train trips to provide extended power to my MacBook and Surface, as well as 4G phone and iPad. I believe they were $30 each from Jaycar, minus the bags and cigarette lighter sockets. They'd work great to provide on board power for a wagon. Little sensor package over the CAN bus, why not, we can do it. Always wanted to play with CAN bus, nows my big chance!