RobjUK

The E3D "ASMBL" milling head concept could be used to cut / mill / engrave card or thin sheet, up to a few mm, materials on a 3D printer chassis. All the parts except the E3D toolchange plate are printed or pretty generic and readily available. The design concept could be adapted with additional or alternate printed to make a small milling head for just about any 3D printer. https://www.thingiverse.com/thing:4206827 Their original design is intended for use on a toolchanging machine, alternating between printing and precision finishing the printed layers - but in principle it's just a general purpose small milling / drilling head. They use a standard ER8 collet chuck; I've got a set of collets including for 3mm or 1/8 dremel bits etc. on the one I made. I got all the parts from either ebay or aliexpress.

6% phosphoric acid. Phosphoric acid rust remover from ebay, diluted by an appropriate amount with deionised water. The bottle I got was 73% so 11:1 for that. A litre bottle of the rust remover costs only about the same as some tiny bottles of ready to use flux, and the rest can be used for making such as paint prep cleaning/etching solutions. (1L of 85% is presently £13 inc postage, eg. https://www.ebay.co.uk/itm/144196873331 ). Once diluted below 10% it's not considered dangerous. I've used it for some time now for white metal to white metal or white metal to brass soldering, with low melting point solder, and it works very well.

Still no response from Railmagic as to whether their system can cope with other magnets in a layout - switched and/or moving - without the field from those confusing the detectors in the locos? That seems to be the biggest weakpoint to me; software features can always be added in, but if the position detection system cannot cope with typical hardware as used in many layouts, it's a showstopper.

Another thought - how would the system be affected by other magnets or electromagnets, anything from solenoid point motors to track-based decouplers to older locos that have "Magnadesion" ? Using fixed magnets for navigation points implies there must be no variable magnetic fields in the same area?

Whether they said it or not, what they meant was "Disable the DC operation bit in CV29". Either they misunderstood themselves, or were just talking shorthand, assuming you were familiar with the various options that can be set in CV29.

I've been building a brass 7mm Deltic kit, a PRMRP one. The original assembly instructions say these should have a nickel silver window frame etch set, but they are no longer supplied or available according to PRMRP. I found an original DJP brass kit, around 1988 vintage - but when that arrived, a few parts were a bit bent from having motors and axles rattling about in the box for a few decades - and the window etch was damaged, only one of the four cab frames intact and a couple of the other small frames wrecked. DJP say they passed the brass kit design on to PRMRP and have nothing left. (Though the two kits have rather different construction for both the bogies and bodies; it's not the same model). I now have two kits without window etches! Does anyone know any place these are available, or is there anyone with experience creating etch artworks willing to recreate them? I took plenty of photos of the parts that were intact, with a ruler for scale. Thanks, Rob.

For info, be sure with any kind of crimp connector or terminal that you use a real crimp tool, not one that just flattens instead of crimping. This is a "flattener" - there is often not enough pressure to form a gas-tight contact between the wire strands and terminal sleeve, so they can corrode over time, or just pull out. Nasty crimp tool These are the better style - the jaws prevent the terminal just spreading sideways, so the metal must compress and flow - that's what makes a good reliable crimp. Better style crimp tool

If the coach stop position is reasonably fixed, could you make the brake external with dummy check rails that can move slightly on a servo or solenoid and spring, to apply light pressure to the inside of the wheel flanges in the appropriate stopping area. That should allow a controlled stop, based on the spring pressure?

Yes, he says nanoseconds, but supposedly measured and displayed to three decimal places, so down to 1/1000 nanoseconds. Smoke and mirrors, to be polite. Back on topic - Can you use a single 12V supply for both the CBUS module power and LED lighting? That may simplify things a bit.

I cannot see that it was working as claimed. That video of from 2013 and supposedly shows an FPGA device timing in picoseconds - a timing accuracy of one millionth of a microsecond or a count rate of 1THz, a thousand GHz. From the info I can find, the fastest FPGA reached around 1GHz in 2019. That guy posted a single "updated version" video in 2015 showing nothing but boxes with wires or connectors, and announcing a new company - whos web site does not exist now. Radio distance measurement over small ranges such as indoors in just not practical, or at least with existing technology, the timing accuracy needed is phenomenal. A more practical system could be a single overhead camera & image detection setup - possible with even a Raspberry Pi or Jetson Nano - tracking unique appearance items by visual detail, or possibly use "invisible" symbols such as IR or UV visible ink and an appropriate camera.

You can have different power supplies for different CBUS modules, however all the grounds must be linked to keep the CAN bus voltages within an acceptable range for the CAN transceiver ICs on each module. It's not ultra-critical, the ground links can be indirect through other wiring, just something so the different CAN modules are not totally floating. The driver ICs are designed so they will not be damaged if one part of the system is powered, as long as the ground (negative supply) voltage difference is not too great between devices. One way is just to use screened twisted pair cable for the bus and tie the screen to the module ground at each device. The bus should be twisted pair, if any significant length or running near any other cables that may have noise or inductive switching spikes. Again not all that critical over a few metres, if you are using individual wires just twist the two for the CAN bus together. Leave the ground link untwisted.

Have a look at "Designspark Mechanical" - free from RS Components. I'd call it engineering modelling rather than artistic, but it's a lot easier to use than programs such as Blender - and you can define exact dimensions for items as you work. It handles multiple file formats and can import & export .step and stl among many others.

Metalsmiths still have a site listing up to 65ft turntables - but 70ft C&S still "Under development". There is a contact phone number; it may be worth giving them a call? (The Midland railway centre site appears to either have been abandoned or hijacked.) Metalsmiths site: http://www.metalsmith.co.uk/4mm_scale_00_EM_P4.htm And contact info: http://www.metalsmith.co.uk/toolmakers-contact.htm

PRMRP list both delrin chain kits and their standard ratio gears under the "Motors, gears and delrin" category: http://www.prmrp.com/motors-gears-and-delrin.html

I'd say it is inherent with the airbrush design? When you use it, paint is pulled up out the container to the nozzle. The pick-up pipe then stays full of paint when you release the trigger. Take the container off and you open the bottom of the full pickup pipe - allowing air back in and the paint out. Letting air in via the trigger first, allows the pickup to drain back before the bottom end is opened up.

That airbrush looks very similar to one I have; press the button/lever for air control & pull for paint flow? If so, try pulling the level full back without pressing for airflow, so air can get back into the paint channel through the nozzle and allow the pickup tube to drain back?

A dead winding or dry joint on the commutator motor could cause something like that - or just a very dirty commutator or contaminated brushes.

How about a "one coat" plaster? They are fine particle but OK in thick / solid sections. I've never tried one for casting, but I have used the stuff in the past as bulk filler and it works well. You can get it from such as wickes or B&Q, or in 25Kg bags (around £15) from builders merchants. https://www.diy.com/departments/thistle-one-coat-plaster-12-5kg/147437_BQ.prd https://www.wickes.co.uk/British-Gypsum-Thistle-One-Coat-Plaster---12-5kg/p/141937

Videos - I've only got the sound working for startup and idling so far, nothing while it is moving, so two separate clips for sound and motion: (The driver is on loan from the Barclay project)

I still have a lot of tidying up and finishing off to do, plus the centre engine cover to make. The sound project also needs a lot! of work - I have a new respect for the people that do them full time! It runs, but so far the control is very touchy at low speed, which I think is due to it being a nominally 3V motor. Hopefully it will improve with some tuning of the motor parameters.

I never realised how strong loctite could be on something as small as this, I ended up prying the shaft and sleeve in opposite directions with two pairs of sidecutters & still needed to heat the shaft with a soldering iron to try and break down the locktite. The gearbox shaft was wrecked in the process but luckily one of the DAS87 shafts was exactly the same size. I took the gearbox apart and soldered the output gear to the new shaft, to try and be sure it could not come loose again. The minor disaster turned out to be a benefit in a way, as I could offset the shaft and move the gearbox near one side. I also left out the inner bearings when reassembling it - with the joints as strong as they were, it had no need of any extra support! With it now turning the wheels, I added the decoder (ESU Loksound 5 micro) and some pickups. The result below:

The cast front and footplates / mudguards are from a Wiseman static white metal kit, which is a slightly smaller scale, hence the split and stretched footplates. The seats are spares from some other 7mm parts I collected for my other projects. Painting was rather slow - I tries airbrushing the yellow to start with, but all it did was put a faint tint over the primer, It ended up with something like five coats by brush to get a solid colour. The drive system all assembled quite nicely, or so I thought - the machined 2mm to 1.5mm reducer bushes pressed in to the wheels, with a solid 1.5mm shaft at the back and some DAS87 1.5mm OD sleeves in the driven wheels, through the bearings. Everything test fitted, then reassembled with locktite to permanently fix it. After it had time to cure, I tried the motor and that ran nicely - but the wheels did not turn! The gearbox shaft just turned freely with no connection to the motor. At that it went back in storage for a couple of weeks.

Some of you may remember I was enquiring about possible sources of very small wheel for an O Gauge / 7mm project last September. Based on PatB's suggestion, I got some Marklin HO wheels and started trying to work to what to do with them... When the wheel sets arrived, I found they had 2mm axles. The only tiny geared motor I could find had 1mm axles & far too narrow. More parts searching followed, ending up with a mix of DAS87 spare shafts & sleeves, some Nigel Lawson machined adapter bushes, 1.5mm bore bearings and other various bits of shafts. Then brass "chassis bashing" - The photos show the progression, spread over several months as time and parts sourcing progressed:

I've just found an advert for Peco point motors that gives the current requirements - Two amps. 7/02 wire has a resistance of 93 milliohms per metre, almost a tenth of an ohm. Double that when calculating for a two-wire loop; call it 0.2 Ohms in round figures. Based on that, each metre of the loop from source to destination would lose almost 0.4V at 2A With four point motors in parallel, that become 1.6V per metre lost. Personally, I'd not use 7/02 for any power handling circuit of more than a few inches and at low current; I'd suggest something quite a bit bigger for the points, possible even 1mm^2 flex for the multi-motor cable run.

Probably not directly relevant to your existing problem, but to prevent future ones: It's not a good idea to tin wires that will be used in screw terminals of any type. Solder is relatively soft and will flow over time, allowing the joint to become loose. That's professionally been considered bad practice since the 60s and it is a specific item in electrical safety regulations as with power circuits, a loose connection over time can cause overheating or start a fire. The regs do not apply to low voltage hobby wiring, but the reliability principles do. Another downside is that you get a stress point at the end of the tinned area and the individual strands are more likely to fail there over time with movement or vibration. A detailed explanation here: https://cdn.thomasnet.com/ccp/00142951/263810.pdf If you want to prevent the possibility of stray wire strands, the preferred was is to use wiring ferrules, aka Bootlace ferrules. They both hold the strands and act as a strain relief, giving some support to the wire insulation. Hopefully this may save another faultfinding session in a few years time!