Gordon H

did you ever look at Sommerfeldt? They do a wide range of pantographs, even they are continental I suppose the size wouldn't be a problem.

https://www.sommerfeldt.de/de/?cat=c34_Spurweite-H0-H0m-spurweite-h0-h0m-34.html&cPath=6_34

 

None of the Sommerfeldt offerings are anything like a BW pan.

What the situation needs is for a European railway company to buy (or lease?) some locos which use them for real. Then we might stand a chance of getting some worthwhile RTR model versions.

DC kits may do a pantograph fs0965 AC type 25kva working scale pantograph.

Nothing like a Brecknell-Willis though...

I am also curious as to why no one seems interested in a better alternative even if its simpler and cheaper

Simpler and cheaper than what?

I think the existence of noise depends on the specific type of motor being used. The responsiveness of the motor to different PWM frequencies will also depend on the type of motor.

 

The existence of any noise depends almost entirely on the PWM frequency. The volume of the noise at that frequency is more attributable to the type and quality of the motor. If your chosen frequency is on or near the mechanical resonance frequency of the motor you will certainly know all about it.

I think the problem is that A standard Red LED will light on around 1.8 volts.   A standard White Led will not light on 2 X AAA batteries around 3.2 to 3.6 volts needing nearer 4 volts.

This is why White LED torches need 3 X AAA cells So you will need much higher value resistors for the reds. Quite literally the reds will burn out before the whites come on.

so you need very different resistors for the reds and Whites if they are simply in parallel. I can't give values because I use 3 volt and 5 volt supplies for my LEDs not the 12 volt nominal 19 volt actual most people seem to use

Dear me, not again...

Can we please stop referring to standard LEDs lighting from a particular voltage?

It has been explained on this and other forums time and time again that this topic needs to be considered in a different manner.

A controlled current is what lights an LED, and that current flow results in a voltage drop across the LED, the value of which varies with LED colour and internal chemistry.

Clearly, the supply voltage needs to be at least that which the LED is going to drop when lit, but any more voltage beyond that is then dropped by a further device, used to perform the current control - usually a resistor.

 

Is there a 'difference' between red & white LEDs that I'm not taking into consideration?

 

The Forward Voltage drop (Vf) of white LEDs is much higher than that of red LEDs, so a red LED in parallel with a white will almost certainly prevent the white one from lighting.

You would be better off either with the red and white LEDs in series, or having separate resistors for the white and red LEDs.

I checked the voltages on the blue/yellow and blue/white combinations and found ~13v 'on' and ~1.5v 'off'. The ~1.5v hardly lights the LED (unless you use a magnifying glass to look).

Try measuring the voltage across just the LED itself to see how little it varies from being just off to full brightness with your variable voltage input.

How thin do you need it to be?

It would be a relatively simple matter to create a stripboard sheet design and get a batch made in FR4 at one of the usual Chinese PCB houses like Elecrow or Itead.

Then you just select the thickness of board when you place the order.

Elecrow, for example, offer boards down to 0.6mm thickness, and you would get 10 off 100x100mm for about a tenner including postage.

According to the MERG technical bulletin for the old system handsets, the old MERG system used address zero and "stretching" of half of the DCC pulses. 

Yes, I remember the discussions with Mike at the time regarding which zeros should be stretched, as their number varies with packet content which could produce variability in the DC offset produced. I believe my suggestion of only stretching the Start bit in each packet byte was the method eventually adopted.

The zero stretching principle is defined in NMRA S9.1

FWIW, the MERG Decod10 and Decod11 decoders were designed to operate with DC traction systems too.

The main issue with simple two value resistor switching circuits is that the servo will always move at its maximum speed between one position and the other, which may be rather fast (and rather noisy, if brief).

I spoke to Cliff yesterday and he does supply the solvents to go with his range of track parts.

Many thanks. Cliff's chairs look narrow enough to do the job without lifting the existing rails.

 

I have looked up Butanol following your post, but cannot seem to find anyone who sells it in less than industrial quantities. How did you get yours? Would Acetone be a suitable alternative, do you think? That is widely available here, in supermarkets even, and has come up in my research as another type of solvent adhesive as one of its uses. 

Suggest you as Cliff about the best solvent to use and whether he can supply any, as he uses it for his ready to run pointwork range.

Suggest you get in touch with Cliff Barker: http://www.cliffbarker.talktalk.net/Gauge1FineandStandardTrack.html

He has a range of chairs for Code 200 and (I believe) can supply a suitable solvent for fixing them in position.

Yes, you control them exactly the same.

 

You can use subtle differences in the way you control them to eliminate some little quirks, but fundamentally all control systems send a pulse between 1us and 2us fifty times a second and don't care which type of servo is connected.

Between 1ms and 2ms (not us) I think you mean.

The only difference I have heard of between analogue and digital is that some, if not all digital ones will try to maintain their position even if the control pulses stop.

The HK15178 should behave almost identically to the SG90 or any similar type. Mine do.

All such analogue servos are controlled and powered in much the same way, using typically 50Hz pulses of duration between 1ms and 2ms. The duration of the pulse determines the servo angular position (1.5ms is centre).

Some servo driving circuits disable the drive pulses once the servo has reached its position each time it is moved, I don't know whether the Peco Smartswitch does this or not.

whats the best tool / tools for cutting PCBs for making sleepers, l have a Proxxon saw bench but the PCB have blunted all my circular saw blades ? any ideas...

Partly depends on what the PCB base material is.

For fibreglass material such as FR4, the Proxxon with diamond cutting blade is ideal. I have been using mine for many years with the same blade.

For paxolin (SRBP) material a toothed blade would likely be better, though I wouldn't using it for sleepers in the first place.

I'm not sure how a working (ie sprung and/or current collecting) pantograph can be described as an essential working part.  It clearly is not an essential working part. 

Of course it is - it's what makes an overhead electric what it is. At a minimum it should work mechanically.

I can think of only one modeller who has working 3rd rail (and a Class 508 with power operated doors - most impressive). From what I can gather from this thread and others, those with working OHLE exist but are very few in number.

Hence my on-going mission to encourage more to give it a go and not just assume it is all too difficult.

Assuming it is the case, it does seem rather ironic that the manufacturers worry themselves more about perceived loss of sales through non-numbering than their failure to provide rather essential working parts in the first place.

The vast majority probably wouldn't say anything because that would be poor etiquette.

That was the view I took having seen the layout in question a few times at shows.

The discrepancies stood out a mile to me, but apart from that, at least it has wires that can be approached physically, if not electrically.

Many don't seem to bother at all. 

But I'm curious: if producing a scale and functional pantograph is the same price as producing either of the other two options, I wonder why you think Hornby's designers have not done so. Do you really think they are that inept?

It is not usually designers themselves that are inept - It is far more likely to be the managers in charge who are the limiting factor in pushing such advancements. Designers in all spheres rarely get to produce the things they would like to, given the chance.

Having seen the plastic sprues that are to be used, they are clearly well designed and manufactured.

It might be useful if they could somehow use the same moulds/CAD files to produce them in metal as a lost wax or similar casting. Can't see that happening though.

Just to set the record straight and finish this off, any assumptions on my part were based entirely on seeing the actual models on display at Peterborough, and asking the actual Hornby reps what the situation is.

No doubt this message will be removed anyway, but there you are.

It's the current that matters in these circumstances, not the voltage.

Sad two burst two bubbles in one night, but the pantographs don’t conduct metal, that’s why Hornby made them from plastic. Rtr gets its juice from the track. Has done for a couple of years, give or take a few.

 

But removing that constraint makes it easier to make more accurate looking ones.

Pantographs don't conduct metal? That statement is completely meaningless.

RTR is only constrained to get its juice from the track due to the lack of suitable working pantographs.

The one thing that sets overhead models apart from the rest is the existence of the pantograph - so surely it deserves a reasonable effort - otherwise why bother?

Only by hand in all directions - up/down & forwards/backwards - and then hope it stays there. They won't stay up if any contact is made, and won't retain their shape either. That might be possible to arrange by application of a suitable solvent to the plastic joints - but that is very much a one-way exercise.

I hate to break the news, but all ready to run Railways are just bits of pivoted floppy plastic.

The bits that need to conduct are usually made of metal, these ones aren't.

Sorry to burst your bubble, but you're clearly making an assumption here. The BW pantograph can be posed correctly. It's Hattons who've not done so...

Possibly so. However, they wouldn't have to concern themselves with posing at all if they were constructed properly.