Track fiddlerI'm convinced you've already thought of this but what measures are you planning to balance the blades on the custom hubs you made?
Hi TF,
I certainly understand the need to balance the blades. I'm going to approach the balancing in stages.
The first step will be to install the cross bracing between the blades. I'm going to use 0.015" phosphor bronze wire. I will solder it in place and then grind the stubs smooth. This should add some stiffness to the blades which will be crucial for rounding them (see below).
The next step will be to get the blade hubs centered on the drive shafts. Currently I have one of the blades mounted on a temporary shaft which I can chuck into my drill to get an idea of how excentric the rotation is. I'm hoping to be able to use a marker pen to identify the 'high' side. Once I have the high side identified I will remove the temporary shaft, then drill the center hole slightly oversize, and then solder a bushing into the hole. Hopefully the markings will give me an idea of which way and how far the bushing needs to be moved to get it on center.
The third step will be to eliminate any side to side wobble. Hopefully once the bushings are soldered into the center of the hubs there won't be too much wobble, but I am anticipating having to make adjustments.
Once that is done, the next step will be to get the outside edges of the blade perfectly round, or at least as close to round as I can. Currently they are not perfectly round because of the way I shaped them. I did not cut the blades in an elipse. They have a constant radii. That meant that when I attached them to the hubs the centers of the blades were slightly further away from the hub than the ends were. I will put the temporary shaft into my drill and then run the drill at a reasonably high speed. Then I will use a large diamond grinding disc in my Dremel to grind the high spots off of the outside edges of the blades while they are rotating. This process will require a very gentle touch and will probably take some time because I can't afford to heat the blades up to the point where the solder might melt.
After all of that we still haven't addressed the issue of having the blades balanced. That will simply be a process of trial and error. If the blades are not balanced (which I fully expect), I will put them in the drill and arbitrarily add a tiny amount of weight to one side. Either the balance will get better or it will get worse. If it gets better I will add a very tiny bit more weight to the same spot and see what happens. If the balance gets worse then I will relocate the original added weight and try again. The process sounds a bit tedious but I think I can get it to work.
By the way, the balancing process will start as soon as I get the replacement worm gear from NWSL. You will remember that I melted the first one because I screwed up the order of assembly for the gearbox. I have ordered two replacements just in case I mess up again!
Wish me luck!
Cheers!!
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
Just out of curiosity, does anyone know what the RPMs of the prototype would be, and would the RPMs used be determined by the type of snow being cleared, or would it always be cranked to maximum?
Brent
"All of the world's problems are the result of the difference between how we think and how the world works."
hon30critter I don't have a schedule, but I would like to see the plow finished within the next two or three months.
I don't have a schedule, but I would like to see the plow finished within the next two or three months.
Rich
Alton Junction
BATMANJust out of curiosity, does anyone know what the RPMs of the prototype would be
Hi Brent,
IIRC I read somewhere that the blades operated at about 200 RPM.
BATMAN would the RPMs used be determined by the type of snow being cleared, or would it always be cranked to maximum?
I suspect the pilot would have goverened the blade speed depending on the conditions. It doesn't make sense to keep the blades at full speed if you are in a relatively clear patch, and obviously the blades would have to be ramped up before driving into heavy drifts.
The article on the plow said that it was quite capable of breaking up heavy snow and ice, and it could easily throw a chunk of ice that was too big and too solid to be handled with a shovel. Apparently the blades were 3" thick solid steel so there would have been a lot of mass working to move the ice and snow. I wish I had made the blades thicker, both for the sake of appearances and so they wouldn't bend so easily.
Glad the pups are okay!
I spent a couple of hours getting the blades to spin on center and not wobble side to side. I got one blade reasonably close but it still needs a bit more work. The second blade wasn't as far off center but it still needs some work too. I will go back at them tonight.
I realized my worst fear when working on the first blade. I got the hub too hot when I was trying to solder the bushing into the center of the hub and one of the blades came off. Fortunately it went back on fairly easily. I will use Tix low melt solder on the second blade, and I will wrap the whole thing in damp paper towels. I could use CA to mount the bushing but I just don't trust it to be strong enough.
This morning I was able to get both blades running on center with almost no wobble, and nothing fell apart while I was soldering the bushings into the hubs! One of the blades required multiple attempts to eliminate the wobble but I finally got it right, or at least close enough. The remaining wobble is less than 1/32".
The next challenge will be to balance the blades. That will simply be a matter of trial and error. I'm not too worried if I don't get the balance perfect. I figure that I can offset any minor imbalance by heavily weighting the plow. If that doesn't work I will just have to run the blades at slow speeds.
I also got the cylinders for the engines assembled. They still require a bit of filing. You may recall that I decided that the original cylinders were too small. I decided to use the original bottom cylinders for the new top cylinders and I built even larger bottom cylinders. I still have to build the engine support frames but I have a pretty good idea of what I want to do.
Here are the new unfinished cylinders. The wooden slats on the outside of the cylinders apparently were quite common in the early engines so I have decided to model them. I'm not sure whether or not they would have been used on larger engines but I will claim artistic licence because the varnished slats look so good. I have deliberately spaced them a bit further apart than the originals. If I placed them tight together the visual effect of the slats would be lost. Thank goodness for my NWSL Chopper II which allowed me to cut multiple slats of exactly the same length! Click on the photo to magnify:
Keep in mind that the engines will be much taller than the cylinders. There will be a bit of distance between the top and bottom cylinders and the whole engine will be about 3 times the height of just the two cylinders as you see them.
Thanks for your interest. Please don't hesitate to offer suggestions or ask questions.
It's looking great Dave! Keep up the good work.
Mike
The easiest way to balance the blades is to use the method we use for watch balances. In fact, I suspect a set of agate poising rails would do this job directly BUT... you have assembled the gearbox already!
That would indicate you might want to try something 'dynamic' -- like the British machines used to dynamically balance main drivers. This works much like a tire balancing machine: you set the assembly up on springs so it can 'walk' a bit when out of poise, and measure the offset -- perhaps with a marking pen that will make a little mark on the 'heaviest' side.
The steeple-compound cylinders are much fatter than you expect, for two reasons. The first is that they are lagged with wood over some kind of insulation -- what you see there is a bit like barrel staves secured with bands. The second is that, in the era of this plow, there would likely be steam jackets around the cylinders inside the lagging. Fletcher's book on 'the steam jacket practically considered (ed. 1895) is available on Google Books -- this will give you the theory and practice of jackets on steam motors that you need to know about 'modeling the result'.
Water Level RouteIt's looking great Dave! Keep up the good work.
Thanks Mike,
OvermodThe steeple-compound cylinders are much fatter than you expect, for two reasons. The first is that they are lagged with wood over some kind of insulation -- what you see there is a bit like barrel staves secured with bands. The second is that, in the era of this plow, there would likely be steam jackets around the cylinders inside the lagging.
Hi Overmod,
Thanks again for the valuable information! I'm not going to make the cylinders any bigger. I don't think they would look right. As they are now, the engines will take up most of the available space on either side of the electric motor driveshaft.
I should also note that you will only be able to see the backs of the engines through the open doors. I do plan on detailing them on all sides because I may decide to make the shell removable just for display purposes.
I just bought a Bachmann 4-6-0 from Trainworld to be part of the plow consist. I think it fits the era perfectly. All I have to do is install a decoder and speakers. The price was half of what eBay was asking.
Hi gang,
Sorry that I haven't posted in a couple of days. I am working on building the steeple compound engines and it is going rather slowly. I'm designing the things as I go. So far things seem to be headed in the right direction. I haven't had to redo anything, but I'm sure those moments will come.
One of the challenges is that the drive shaft from the electric motor has to go right through the middle of the two steam engines. I am building the engines on a common frame but I will have to cut that in half in order to install them around the actual drive shaft.
Here are the engine's bottom frame and the crankshafts. There would normally be some sort of clutch mechanism and the drive chain between the two engines, but in this case I have to leave room for the electric motor drive shaft. Once I get the steam engines and the electric motor drive system in place I will be able to judge what, if any, clutch or drive details I can add. There should also be speed governer connecting rods attached to the crank shafts. They will be finicky but not impossible:
A little more progress on the engines. They are 10 scale feet tall which is what I wanted. There are several details still to be added. I have to work something out to get the steam from the boiler to the engines, and I could add some semblance of throttle controls.
The cylinders are not perfectly round. That's because I had to add extra layers to the tubing that I had to get them to the size I wanted. I can't change that now. Also, the engine frame uprights aren't quite perpendicular but that doesn't seem to show when viewed from an angle. I don't think the irregularities will show once the engines are inside the plow body because most of the engines will be forward of the open doors.
If you want to get really technical, you might notice that the geometry of the engines is a bit messed up. Can you identify what is wrong? Free beers in the Diner for anyone who can spot the problem!
Painting them will be fun. I use that word in the broadest possible sense. My hands were shaking tonight to the point where I almost gave up trying. Getting the rivets installed in the connecting rods took forever! By the way, I didn't make the connecting rods. They were from the N scale 4-4-0s that I used to make my brass critters.
Lagged cylinders don't have to be perfectly 'round' (i.e. cylindrical). In fact the steam jackets are almost certain not to be.
Don't forget to include the relief cock and blowoff-valve detail for when you start the engines in 'plowing weather' -- there will be a heap of condensation that will need to be relieved and drained before the engines can start spinning up the inertial mass of the rotor, let alone reliably produce torque...
That is an awfully short stroke for a DA engine even if jacketed and lagged. I still haven't figured out where the valves are.
Main steam line will be taken from the header that "was" to the cylinder downcomers at the top front of the boiler: it will be heavily lagged, have at least one steam trap at an intentional low point, and will have the 'throttle' that controls the engine right next to the reverse... accessible by direct and positive linkage from controls in the cupola. I'd retain the existing throttle in the dome as a safety cutoff, but not use the long linkage and stiff action to control or 'start' the engines; the actual throttle that the 'throttleman' uses ought to be a Wagner throttle (patented circa 1912 if you want to look it up) which is actually a "fluidic servo" of remarkable sensitivity and maintainability.
OvermodThat is an awfully short stroke for a DA engine even if jacketed and lagged.
Ahah! I owe you a couple of beers! Yes, the cylinders are far too short for the pistons to be able to move the distances that the crankshaft suggests. Am I going to remake them? No bloody way!!
OvermodI still haven't figured out where the valves are.
Neither have I! I'm going to add some important looking bits to the sides of the cylinders, and I will attempt to add connecting rods for the valves, but ultimately those details will be lost on almost all observers except for the knowledgable chaps like you.
At some point I will have to say that the engines are 'good enough'. After all, these things are as much of a product of my imagination as they are representative of the real thing.
I do have a question for you. Where would the steam have been fed into the cylinders? I suspect that I have to model some sort of intake manifold. Where would it have been connected to the cylinders?
Thanks again for your input!
I asked der Klugemeister about the stroke thing, and he said 'since you're not expecting the thing to actually rotate, just cut off the journals in the cranks and re-cement the rods with an appropriately shorter 'stroke inside circular webs...'
The thing I advise you to do is go on the Web and find what you can about the Willans high-speed engine that was installed in the first Heilmann locomotive. That as I recall was a triple-expansion steeple compound... that was actually balanced (six cylinders, 120-degree mutual crank angle) and I remember some very detailed cuts of the engine that you could crib from -- I believe there is at least one in the Scientific American article on the locomotive. You might also find one of the 3D cutaway illustrations of how the first series of Vauclain Compounds (the ones with the little cylinders over the big ones on each side except on cabbage-cutters) ran the compound expansion in proper phase, at high speed (the fastest locomotives in the world in 1891 were built that way) with only one piston valve! But be sure you have laid in a stock of Excedrin or perhaps oxycodone as you may need it before you fully understand what all the little ports and passages do as that valve moves...
The thing is that I think the Willans engine was single-acting, like a car engine, and the way you've built yours is single-acting but a bit like a von Borries with the HP steam pushing down and the LP steam pushing up as the engine turns through a cycle. For DA you'll want plumbing to both ends of both cylinders...
The main steam line comes from the upper front of the boiler and passes to the chamber for the Wagner valve roughly under the cupola somewhere, then branches and curves down to a receiver with the equivalent of cylinder cocks (exhausting under the floor where the condensed steam ice won't screw up the brake rigging) and then up, branching, to the high-pressure cylinders on top. This is where you'll need a valve apiece, driven off... let's say a strap eccentric with one of those oversize crank webs acting as the cam. Some of these engines did not have either a link or a riding cutoff to adjust admission, and you could probably fake 'wiredrawing' cutoff as on the Army Franklin System type D gear if anyone were so imprudent to ask you how the model would do it, but I'd model some kind of cutoff, and figure out how the linkage to adjust it would be available up in the cupola -- it would not be cheating to have it adjust at the engines via compressed-air servo, no different from an air power reverse on a locomotive and of course smaller...
The valve admits steam to the HP engine, with enough mass flow that as it expands through what can be uniflow-like exhaust ports it will push effectively on the OPPOSITE SIDE of the LP piston, starting to cushion the deceleration of the piston assembly as it traverses dead center and giving some effective admission lead to the tired old unsuperheated push on the LP side. You will figure out how fast the engines are supposed to be turning by knowing the rotational speed of the rotors, what the "final drive" ratio is supposed to be, etc. -- you have a bit of trouble in that you only have two cylinders and not three, so you have some balance issues because you have to quarter the thing to make it self-starting and that's going to make for vibration, so you won't want to rev it as fast as the Willans, but we can handwave this 'just between us'
Where the real design fun comes in is what you do with the exhaust, which is going to come in enormous volume at comparatively wretched pressure and steam quality out of the LP cylinders and has to go back into the boiler to produce front-end draft. That is going to want to be a tapered, heavily-lagged duct (the taper toward the boiler end, to let the steam expand so the cylinders can 'breathe' as they exhaust). Now I suspect from the visible dimensions of the stack in the pictures that this would want to be in the low 20psi range as it gets to the (doubtless somewhat primitive and empirically designed) nozzle in the front end. This will work if most of the time the plow engine is running at near full throttle into a load, as you have many cycles per second to keep the exhaust steam hot at high mass flow, but might not be so fun when you're warming the engines or idling between runs. If I were building it I'd have multiple nozzles, probably four from the four individual LPs, and some fancy geometry of petticoat (doing what the vanes in a Kylchap do, precociously; google "Kordina" to see how the exhaust pulses are isolated) and a nice fat or elongated visible stack. (Big enough, in fact, that you could look down the model stack and see the nozzle detail at the bottom -- won't that get you points from the NMRA judges???)
Incidentally, in that era the 'sparks' and char caught by screening in the smokebox would have dropped to the bottom, where there would be a sort of vertical cylinder 'trap' for them with a hinge to allow bottom dumping. You see this on a wide range of contemporary locomotives, occasionally of surprising 'capacity'. I am not sure how you would rig this for use in snow-packed or icy conditions. If you were to add flanger-blade functionality, as in the 'conventional' rotary in your original post, that would tend to keep the thing clear, but backing the plow in loose snow would pack it where you probably wouldn't want it. Something you do NOT want to do is have to open up the smokebox and shovel out the accumulation while the car is operating...
Once again, tons of wonderful information! Thank you.
I will have to read some of it a couple of times before I understand exactly what you are describing. I did look at several Willans engines on the web and that has given me a better idea of how to do the 'plumbing'. I'm going to remove the brass pipes that link the cylinders because they are not representative of a Willans engine. I have a good idea of how to link the cylinders at the top as well as what sorts of piping and valves need to be added.
I still have to figure out how the steam was fed to the engines. I will have to reread your suggestions a couple of times before I will be able to get my wee mind around them. I haven't looked for the Heilmann locomotive illustrations yet. That's next.
I'm not going to adjust the crankshaft throw. Everything is glued solidly in place so I don't want to mess with it. Actually, I think the exaggerated crank offset looks better than it would with the offset reduced. If the offset is reduced the connecting rods will not show the angled joint as well. You are the only one who will notice!
I have some ideas for the floor ash grates. They won't be operable. To make them operate I would have to remove the steel floor weight which I am reluctant to do since the plow will be pushed most of the time. I want to keep it as heavy as possible.
I have revised the engines 'plumbing' to make it look more like the Willans design that Overmod suggested. The engines are exactly 1 1/2" tall:
The valves on the cylinders are a little overdone but I used what I had on hand. I would have used the small drain cocks that are on the bottom of the condensation drain(?) but I was one short.
Some parts on the top of the small cylinders are slightly out of place. I was using CA so it would set quickly, which it did. Unfortunately one of the parts shifted and before I could adjust it the CA had done its thing.
The black stains are from the Sharpie that I use to mark the styrene.
Here is the real thing for comparison. This is a small version:
Hi again Overmod,
After all the advice you have given me, I'll have to put a builder's plaque on the plow with your name on it!
OvermodWhere the real design fun comes in is what you do with the exhaust, which is going to come in enormous volume at comparatively wretched pressure and steam quality out of the LP cylinders and has to go back into the boiler to produce front-end draft. That is going to want to be a tapered, heavily-lagged duct (the taper toward the boiler end, to let the steam expand so the cylinders can 'breathe' as they exhaust).
Just a small clarification if you please. I'm guessing that the large end of the tapered duct would be closest to the boiler. Is that correct?
Also, can you describe what you mean by "heavily lagged"? Do you mean that the piping would be heavily insulated or are you referring to the taper in the pipe? The word 'lag' has a ton of meanings that I didn't know about. I'm used to using it as a verb.
Any guess as to what the diameter of the pipes leading from the boiler to the cupola might have been? I'm guessing that they would have been several inches in diameter.
The method of controling the engines raises an interesting point. I have read that in the early plows, the person in the cupola would have relayed instructions to an engineer who then operated the controls of the engines accordingly, the controls being located on or next to the backhead. In other words, the main steam was not routed past the cupola. I'm not sure of the method of communication. I'm considering using that setup for the plow. The cupola would have had steam for the purposes of operating a whistle which was how the plow communicated with the pusher locomotives. I'm not sure where I read this, but I do remember that there was typically a crew of five operating the plow itself. I can't remember the correct names for each of the crew members.
Thanks,
Yes, the wider end of the taper would go toward the boiler (and "into" it at the bottom, turning smoothly inside to end in the nozzle system for providing the draft in the stack arrangement.
For a much more exaggerated example of the taper action, look at the Steamotive arrangement in the UP high-pressure turbines 1 and 2 from 1938. Those are 1200psi going to full condensation, so the exhaust plena have lots and lots and lots of steam volume to deal with...
"Heavily lagged" is in the steam pipe sense: heavily insulated, probably with asbestos covered with primed canvas to get you toward the right surface appearance. This is more for keeping the steam from condensing than for holding down the heat in the operating space.
A bit about my philosophy of design: There is no practical 'second means of egress' from that cupola. I therefore consider that anything involving steam, particularly that could fail in such a way as to direct steam even at exhaust pressure toward the cupola interior, be kept as far away, ideally behind closable doors or hatches, from the people in that cupola.
That is why I said 'linkage' from the cupola to the throttle and (if provided) cutoff arrangements and clutches for the engine and drive. It is also why the whistle will be provided via some sort of linkage, probably a rope, to a whistle valve somewhere back on top of the carbody. Or perhaps blown with compressed air from the brake reservoir. The closest 'steam' gets to the cupola is the sidewall radiators or whatever provides the heat in there.
You could indeed save a few bucks by having some poor throttleman at the levers, responding to some sort of engine-room telegraph or 'peep' air whistle cribbed from passenger components. But there's no better way to assess what the engine needs to be doing in the next couple of moments than by looking out the 'wheelhouse' windows with the levers right at hand. Can you imagine running a Hulett with whistle signals?
This being 1904 and all, and your having dedicated power for the plow trains, I would consider rigging up a color-light system to at least one of the locomotives, and use that rather than whistle signals to convey information for when and how to push the plow. An adapted engine-room telegraph (from a marine application) could be used also.
Thanks for the clarifications. I apologise for not catching all of the details in your posts, like for example your references to 'linkages' from the cupola to the controls. You do provide a prodigious amount of information and it does take me a while to absorb it all.
I also have to say that I don't want this project to turn into a nightmare of details so I'm probably not going to model all of the linkage bits. Most of them won't be visible anyhow, so why spend the time? If I decide to make the shell removable then that would justify more detailed modelling of various components.
I'm still waiting for parts from NWSL so I can go back to working on the blade drive system. Until they arrive I will spend my time working on the cosmetic details.
What do you think of the engines so far?
Most of what I'm discussing with linkages and so forth is to be used in explaining how the thing "works'' if anybody asks ... not to be explicitly modeled.
I like the engines just fine.
Huletts, I believe of similar vintage, use servo electric controls with no force feedback... no visible linkages there, just implied wires. You would want a manual throttle backup somewhere at the engine, but a throttleman would not be happy trying to work the throttle blind, never knowing whether a shock or collision was in the offing, or so I'd speculate...
OvermodMost of what I'm discussing with linkages and so forth is to be used in explaining how the thing "works'' if anybody asks ... not to be explicitly modeled.
Thanks for clarifying that. I was getting a little overwhelmed by all of the details.
My next step will be to figure out how to model the steam connections from the boiler to the engines. I'm assuming that there must be some sort of valve system to govern the flow, but I'm not sure what that would look like. Is there a 'standard' locomotive component that could stand in for the valve system, or is my understanding incorrect?
I'm still waiting for the worm gear from NWSL so I can put the gearbox back together so I can work on balancing the blades. In the mean time I have separated the shell from the frame. That allowed me to finish the roof supports around the smoke stack.
Every time I look at the blades I am not happy with them. The blades are far too thin (the originals were 4 1/2" thick!), and they have all sorts of dints and bends in them as a result of me trying to straighten them out. So, I'm seriously considering building new blades with 0.025" brass sheet The current blades have 0.005" sheet. They will look better and they will be far more durable (and I won't slice my fingers open on the 0.005" blades!). I now understand how to cut the blades in a slightly elliptic shape so they will fit the hubs properly when they are on the diagonal (thanks to TF for bringing the ellipse issue up). I won't need to use the soldering flanges that I added to the original blades. I will hold the blades in place with temporary wire anchors until they are soldered in place.
This will also give me a second shot at centering the hubs on the drive axles. The current hubs are pretty close to being centered but they aren't perfect. If I take my time I should be able to get the new hubs centered without wobbling.
Cutting the 0.025" brass blades will be a bit of a challenge but if I cut them slightly oversize I will be able to grind off any cut marks left by the shears and get them to fit the hubs properly.
I don't see this as a step backwards. The first set of blades were the trial, and the second set will be the final product. Don't hold your breath. The new blades will take a while.
If the boiler was 'sourced' from an older locomotive, as it would almost surely be, it will be saturated (no superheat) with a dome, dome throttle, and dry pipe. This would be retained in the plow, and if there were a 'throttleman' the original throttle could be maintained and used to run the plow engine. Cutoff would then be a linkage up to where the engines are; an air or steam reverse mechanism could be used instead, located close to the engines and probably with a cross rock shaft so one reverse does all four cylinders -- note that this simplifies cutoff control from both the boiler backhead area and the cupola if desired.
The 'catch' is that quick response at the engines and perhaps quick reversal may be important. In such case the dome throttle would be used as a 'stop' (as some locomotives converted to front-end throttles were) and a separate control -- the Wagner throttle in its enclosure -- would be provided in the new pipe coming from the end of the original dry pipe, with the branches then going to each side and then feeding the valves at each cylinder. That gives light and positive action, which a dome throttle would NOT have...
As an aside, a dome throttle ahead of a multiple poppet front end is THE definitive cure for 'nightwalking' (in case you ever wondered why the external throttle linkage has a reversing 1:1 lever in the middle of it). Even when the valve gear is centered at mid, the combination lever gives some valve action, and any steam leakage at the starting poppet when the boiler expands differentially from the extended throttle linkage can make the engine gently but inexorably move... and fill up with condensate, etc.... if not otherwise secured. A positive ground-seated stop in the dome will not allow that.
Not much work to show for the last three days. I did spent some time cogitating about how to do certain things like rebuild the rotary blades.
I tried using 3rdPlanIt to draw the rotary blades with an ellipse but I haven't got that right just yet. I may resort to making up a heavy paper blade and then trimming it until it fits the hub. Once I have that, I can cut the actual blades. I'm only going to put one mounting tab on either end of each blade instead of tabs all along like I did the first time. If I can get the curve correct the extra tabs won't be necessary with the thicker blade material.
I also played with positioning the engines and the boiler. Unfortunately a lot of the engine details can't be seen through the open doors. That has convinced me to make the shell removable which should be fairly easy to do. The fixed blades and the rotary blades will stay on the frame.
Stay tuned!
Be careful how you design a 'shell'. Much of the visible side of that car will be heavy framing; in fact I think some is cast steel. See the heavy frame on the conventional rotary drawings? Your plow takes longitudinal shock that is much greater, acting up higher, so the functional plow framing has to be more robust both in the underframe and to prevent the heavy nose bending backward even a little.
My advice is to treat the 'wooden panels' of the sides as removable, framed to have strength to come out as if they were doors, with solid permanent 'bridge truss' framing behind and in the roof and cupola structure. Lag them as refrigerator-car sides would be, put exhaust-steam radiators on the inside with appropriate plumbing, etc.
This would also facilitate inspecting and repairing the engines...
I finally figured out how to get the blades to fit the hubs properly. TF had asked how I cut the ellipses for the blades to sit against the hubs at an angle. In fact I had just cut the blades at the same radius as the outside of the hub, but that left the center of the blade a little high when the blade was turned on an angle. Today I realized that I didn't need an elliptical curve. All I needed was a slightly larger radius than that of the hub itself. After much trial and error I have a pattern that fits the hub on the diagonal perfectly. I'm sure all of the mathematicians out there knew that, but it only took me a couple of months to figure it out!
Next step is to see if it is worth trying to get the old blades off of the hubs. If they don't come off easily I'll just make new hubs.
Last night I got the new thicker blades cut out (0.025" copper) and I got the temporary mounting tabs attached to them. The tabs will be ground off once all the soldering is done. The tabs have pins through them so they can't come loose even if the solder melts.
This shows (I hope) the relative thickness of the blades. The first set of blades were 0.005" thick. The new blades are 0.025" thick. The prototype blades were 4 1/2" thick! The new blades scale out to about 3" thick. I had some 0.032" brass that would have been closer to the 4 1/2" but it was just too hard to cut. The 0.025" copper was fairly easy to cut and it is much more solid than the first attempt.
I also spent a couple of hours measuring and remeasuring the hub centers and I actually got them right! There is no perceivable excentricity in the hubs. I tested them by mounting a 1/8" bit in my drill (the hubs are drilled for a 1/8" OD bushing) and sliding the hubs all the way down so they were resting on the chuck jaws. When I ran the drill there was practically no runout. I'm glad that I had my dad's old vernier callipers.
Next step is to file all the edges of the blades smooth. I should have done that before installing the mounting tabs!