Guy Rixon

A new freight-flow has come to light. Cattle go north through Strand to the LNWR where they arrive at Maiden Lane goods station, that being the most-convenient depot for the Metropolitan Cattle Market. The cattle trucks return empty over the CCEJ and call at Bedford Street Depot, SECR, where they are back-loaded with empty fruit-baskets which are then dropped off at rural stations in Sussex and Kent.

Heat pumps circulate cooler water than conventional boilers, as their efficiency drops as the output temperature rises. This needs bigger pipes to transfer the heat. Any retrofit of a heat pump to a property with heating pipes of 15 mm dimeter or less won't move the heat properly. Such was the verdict of the team who our installed our heat pump, and they proceeded to rip out all the pipes and refit. There's a bodge with a higher-pressure pump for circulation, but our crew said that it doesn't work properly.

Possibly not in the winter? When We had an air-source heat pump installed, the year-round average efficiency was reckoned around 200% or a little less; OK, but not spectacular. The heat pumps are very good at heating water for your shower in summer and not so good at heating your house in winter.

There's a suggestion that the cuts reflect infrastructure work that cannot be completed this year or next year because of the pandemic. If the money were being deferred because it cannot be spent quickly, that would be reasonable. But that's not how public-sector budgets work; if it's gone now, it doesn't come back later. So we --- electorate --- need to extract some kind of government promise that investment will return when it can be used.

Mike has very kindly sent me v6 of the supported model in which the supports are stood off from the part a little more. This makes it easier to wash out any uncured resin, and easier to cut away the support without straining the part and breaking the thin areas. Elegoo grey resin, 0.04 mm layers @ 7 seconds (90 second for base layers). I now consider this part solved, and have enough in hand for the first two coaches. Many thanks to all who assisted, and especially to Mike for his detailed support.

I ran Mike's supported version of the model with his settings and this came out: It's clearly better, and I shall use Mike's settings for exposure, lift rate etc. from here on. It's not as good as Mike's prints and is still filling in around the supports. Possibly my printer is just not as good. Both prints broke while I was removing supports. Now that it's not filling in on the front face, I can minimise the thin, central area again to make it stronger.

SECR-coach-glazing-brake-3rd.stl For those who wish to try, I attach the STL for the glazing carrier.

It was the resin. I changed from 3Dream clear to Elegoo grey and I now have a useable print. This is with the supports on the non-cosmetic face only, and the orientation as before; I slightly thinned out the forest of supports. It's not a perfect print, but it can be made useable by sanding and filing with very little work. Notably, the lip of the drop light is fully formed in this resin. The scratches in these photos are from me scraping away uncured resin during the washing process. I should probably use a stiff brush for this so as to scratch less. I haven't filed or sanded anything after curing. I conclude that the 3Dream resin is not really useful in a Mars Pro printer for the things I want to make. Or, at least, its happy place is off in a corner of parameter space that I'm not likely to find. Possibly that stuff is more at home in SLA printers. Thanks to all who offered advice and and insight.

During printing. I've been trying to straighten it by bending and pressing after trimming and before curing. Some times it works, other times it breaks. Anyways, here's the latest, with the supports shown in my last post: The warp is avoided and the drippy areas can be cleaned up ... but the failure to print the visible edge of the droplight ruins the whole part. Try again when I have the other resin, I guess. Or redesign as a two-part assembly with no rebates on the back and print it flat on the bed.

Currently printing this: Extra supports to combat the warping and even more support to attack the problems aound the droplight lip.

The machine is in a heated room of the house, so ~19 Celsius in the evening, and warmer in the day when the sun is on. If it needs to be somewhat warmer, I can put a fan heater in there. BTW, the printer is not sitting in sunlight; it's on a shelf in an ex-wardrobe where it never sees the sun. The resin is 3Dream Lodour transparent, which claims to be of low viscosity. I chose it for the lack of pong rather than the other aspects. They don't post on their website any advice for temperature or exposure, but I might email them. Most-recent supports look like this: ...and it's still failing. One bottom arm of the I shape got truncated underneath, despite the supports; the top of the droplight frame filled in again, despite the supports to stop it slumping; the sides of the droplight frame shrank back again; and it warped into an S shape, then broke when I tried to flatten it (before curing). This is with an adapted model, where the visible lip of the droplight has been thickened from 0.33 mm to 0.5mm. The rebate (0.33m deep) on the non-cosmetic side now runs the full height of the piece so that it's easier to clean out with a file. So I am not happy with this resin and will try again with some Elegoo grey resin when it arrives. I may also add some supports to the the back of the droplight frame, contacting in the rebate, in the hope that this will stop it shrinking away. I may as well do one more run while I have the 3Dream glop in the tank. Plan C is to redo the model with a flat back and a single rebate on the front into which I can glue the etched droplight-frames. But that seems defeatist.

Last night's shot, with the model vertical, warped and cracked. Today's, with extra supports, avoided the worst of the warping and ended up like this (without any cleaning up, but primed so it's easier to see): It's slumped on all the undercuts and the visible part of the droplight frame has actually shrunk in its lower third. I can fix the slumping of the base and side cut-outs with extra supports, and these areas are anyway neither cosmetic nor of critical dimensions so can be filed square. What I can't fix with a file is the slumping and shrinkage of the cosmetic droplight frame. I'm not sure how I'm going to improve that. Possibly I have to thicken the thin lip; it's only 0.33 mm thick at present.

This is the model; it's a glazing carrier for a coach. The face towards the LCD, that prints well (rebate represents the visible part of a droplight frame): Face towards the build plate, that gets messed up (rebate is supposed to hold the glazing, but gets partly filled in, plus minature mountain ranges form around the rebate ): This is what Chitubox thinks are suitable supports for printing it horizontally: If I tilt it ~20 degrees off horizontal, Chitubox allocates similar supports and I get the same problems with filling in between supports; plus the edge of the part nearest the build plate then seems to warp. I'm trying another run with the long side vertical in the printer. Bill, thanks for the insight. I've already positioned it with the sensitive, cosmetic face towards the LCD and I can do a little clean-up on the other face by filing. But should I really be getting nearly a millimetre depth of unwanted resin for several square millimetres around the support attachments? Seems excessive. BTW, it's not just this model. Every single print so far on this machine has had similar issues, and I've run five different models so far.

I've recently acquired a Mars Pro printer and I'm having some problems with print quality. The prints have acceptable finish on the side facing the LCD and rubbish finish on the other side, facing the build plate and the supports. The machine seems to be filling in the spaces between the supports with cured resin. It's as if the resin sitting on top of the undercuts --- which are, of course, on top during printing --- is getting cured by the LCD instead of remaining liquid and getting washed off after printing. Does anybody recognise this kind of problem, and does anybody have a cure? It's transparent resin. I wonder whether that leads to light passing through the print and curing the waste resin on top? Perhaps transparent resin is good in laser-based printers and inappropriate for LCD printers?

This is, IIUC, to push the blocks flat against the coning of the wheel-type without having to cast the coning into the blocks. The Mousa kit I've just built (in P4) represents this geometry. In general, I don't bother with it since it can't easily be seen with the wagon on the track.

There's no reason to hassle the smiths by specifying a curved bridle unless it's needed to clear the bottom of the axlebox. Therefore, one might look at trends in the shapes of axleboxes, or, just possibly, variations in the lengths of the axleguard legs.

Very little on a conventional workbench. It's a gamma source, and also used in ultra-high-stability clocks, the ones you get if a caesium fountain just won't cut it. I thought it was one of the elements used in posh magnets, but Wikipedia doesn't mention that.

Here's the beast pretty much finished. I still need to black the internal ironwork and the tyres. The may be some paint touch-up to do, and, of course, some weathering. The load is written as 8 tons, not 10, as that is written on the GA and I'd already set the transfers before Stephen's inputs. I suspect that the 1902 wagons had 10-ton bearings and springs like the 1904 ones, but chose not to scrape and repaint.

Are you allowed to say that these days? Sounds a bit disrespectful. In truth, you are quite right and the spin-up/spin-down thing is of course about the states where the electrons live. Here, the thing that still I'm trying to get my head around is that after 115 years development in quantum theory of atoms we still don't have an exact-enough theory of atoms to precisely identify all those states (in anything more complex than a Helium ion). And when I say "get my head around", I mean that I'm currently cat-herding scientists to make a labelling scheme that's just approximate enough to work and can be coded into a software system. Sore point. Pray for my quantum soul.

The return flows are sometimes an issue for S&T work, too. I once read an old article that spoke of problems on the Metropolitan Railway (the original bit, not the branch into darkest Buckinghamshire). This was built when London was an electrical desert. The telegraphs were earthed at both ends of the cable run --- i.e. return through earth --- and all was well for a while. Fast forward thirty years or so and London was majorly electrified, with motors (for lifts and such) appearing all over; and everybody was returning their current through the earth. The local earth-potential seen by the telegraphs went up and down like a whore's bloomers and the machines were not at all happy. Eventually, the S&T engineers were forced to install common-return wires for their telegraphs. Later, when the railway put in conductor rails, they put in return rails too. As to electrons being identical remember that they are fermions, and therefore bolshy little so-and-sos. Put any two in the same orbital and they will insist on distinguishing themselves by having different spins.

Your drawing suggests that this kind of push rod is a round bar, drawn down to a flat section at the end opposite to the block, where it's pierced for the pin that links it to the tumbler. If that were the case, I would make them of wire with the flat ends squashed in the vice and the sharp ends drilled into the blocks. They would be strong enough not to need a strong support.

Would you accept printed assemblies for the blocks, block hangers, push-rods, tumblers and safety loops? I have a few types available already and can easily add extra wheelbases if needed.

Thanks Steven. Yes, these are the 17'6" wagons, for which the GA is dated 1892. I guess they were built all through Mr. Longbottom's time as CE, and he died in office in 1902 IIRC. The kits has double-block brakes on one side only, so number 6216 sounds good. Now I can finish the transfers and get it varnished.

Current wagon is a NSR "Longbottom" 2-plank wagon of 1892, from the Mousa kit. Does anybody known any running numbers for these?

She is absolutely unique and more dear to me than any trains.