Any Question Answered

[chrisveitch]

1 hour ago, Chris Higgs said:

 

It represents that a steel bufferbeam is a U shape (same as a solebar) with the open side of the U facing inwards. So indeed the outer face of the bufferbeam is flat.

 

And the end of the bufferbeams both sides of the beam are visible.

 

Chris

 

 

Thanks Chris - it's a few months since I worked on these and my confusion was exacerbated by forgetting what I'd done previously. I'll not embarrass myself by elaborating! 

 

Chris

[Valentin]

I am designing the frames for a chassis I want to test-build. I want to use 0.7mm P/B sheet for the frames and 6mm brass sheet for the inner chassis. Both, the frames and the chassis will be built using a CNC milling machine.

 

I have finished the design for the frames (drawings below). The dotted lines are construction lines.

 

I have two questions:

1. Are three 14BA countersunk bolts overkill? Will two bolts be enough? I would use 12BA (or even 10BA) but I can't find sleeves for them. I know I could use epoxy or nylon plugs but I am not sure I could set the milled brass chassis with enough precision after fitting the plugs.
2. Shall I repeat the slot I used for the middle drive-wheel for the front wheel? There is 0.12mm up-down play.

 

 

 

Edited August 16, 2022 by Valentin

[Izzy]

Hi Valentin,

 

Unless you are going to fit some kind of method to control the axles rising upwards, compensation or springing, I don’t see any advantage in providing upward movement past the datum line with any axle.  Indeed my past experience is that allowing just the middle axle to rise without any form of control just leads to the coupling rod forces making it ‘flap around’, lift off the rail head for no good reason, and look wrong. This is especially the case if you use jointed coupling rods and whether or not you drive off an outer axle or even the middle one. Allowing any axle to just drop a little bit is a different matter.

 

Bob

[nick_bastable]

On 16/08/2022 at 14:21, Valentin said:

I am designing the frames for a chassis I want to test-build. I want to use 0.7mm P/B sheet for the frames and 6mm brass sheet for the inner chassis. Both, the frames and the chassis will be built using a CNC milling machine.

 

I have finished the design for the frames (drawings below). The dotted lines are construction lines.

 

I have two questions:

1. Are three 14BA countersunk bolts overkill? Will two bolts be enough? I would use 12BA (or even 10BA) but I can't find sleeves for them. I know I could use epoxy or nylon plugs but I am not sure I could set the milled brass chassis with enough precision after fitting the plugs.
2. Shall I repeat the slot I used for the middle drive-wheel for the front wheel? There is 0.12mm up-down play.

 

 

 

looks like a O1 to me   in which case mill me a set please

 

Nick

[Valentin]

6 hours ago, Izzy said:

Allowing any axle to just drop a little bit is a different matter.

 

Bob

 

Thank you, Bob. I will adjust my design to let only the middle axle to drop a bit (0.1 - 0.15mm).

 

3 hours ago, nick_bastable said:

looks like a O1 to me   in which case mill me a set please

 

Nick

 

Nick, if everything goes according to the plan, you will definitely have a set of frames and the solid brass chassis sandwiched in between the frames. Currently I am waiting for new stepper motor drivers, which can supply more "oomph" than the ones I started with. And I am still learning about CAM in Fusion 360.

[Nig H]

Hi,

 

Probably a silly question to most of you but I know almost nothing about electrics/ electronics.

 

I want to connect a c. 16V AC power supply to a Velleman voltage step-down thingy. The power supply has a jack plug like female connector and the Velleman has two separate screwdown sockets for wires or spade type plugs. What I want to know is what I need to connect the two devices together, and where to get the connectors.

 

Any help gratefully received.

 

Nigel Hunt

[Nigelcliffe]

2 hours ago, Nig H said:

Hi,

 

Probably a silly question to most of you but I know almost nothing about electrics/ electronics.

 

I want to connect a c. 16V AC power supply to a Velleman voltage step-down thingy. The power supply has a jack plug like female connector and the Velleman has two separate screwdown sockets for wires or spade type plugs. What I want to know is what I need to connect the two devices together, and where to get the connectors.

 

You need to be a lot more precise about the "Velleman voltage step-down thingy".     If it's what I think it may be, a DC-DC voltage converter, then the answer is "do not connect it to a 16v AC power supply".    The clue is in the name:  "DC-DC", it requires a DC supply, and puts out DC.    

 

DC powerbricks are everywhere, phones, laptops, every device you buy has a switched mode DC power supply   (save a few old model railway controller designs which persist with AC input).    So, use a DC supply for it.  

 

 

- Nigel

 

 

[Nig H]

16 hours ago, Nigelcliffe said:

 

You need to be a lot more precise about the "Velleman voltage step-down thingy".     If it's what I think it may be, a DC-DC voltage converter, then the answer is "do not connect it to a 16v AC power supply".    The clue is in the name:  "DC-DC", it requires a DC supply, and puts out DC.    

 

DC powerbricks are everywhere, phones, laptops, every device you buy has a switched mode DC power supply   (save a few old model railway controller designs which persist with AC input).    So, use a DC supply for it.  

 

 

- Nigel

 

 

Hi,

 

Thanks Nigel. The Velleman unit is a VM124 1A power supply module. Maximum input voltage is 24V AC or 35V DC. Output voltage between 1.2V DC and 30V DC. The power supply is AC stepped between 3V and 15V.

 

I'm still wondering how to connect the two units.

 

Nigel Hunt

[Izzy]

Hi Nigel,

 

I use a previous kit version of these on my layouts to power such as hacked servos, LED's etc. The green sockets for power in and out should be printed on the PCB, all mine have been. Just in case they are not here is a quick shot of one of mine. From looking at them on the Vellmann website it appears that they are identical to before in the placement of parts, indeed your VM124 seems to have been replaced by yet another version. Perhaps it's just small changes to the actual part values for the general specs seem the same throughout all different versions.

 

 

Anyway, I have marked the DC outputs in black/white dots. You do need a Multi-meter to be able to set the current values that you desire.  Virtually impossible without. The pot adjustment is marked with a red dot. it's moulded with an arrow imprint to show where the point is. You twist this with a small screwdriver. Depending on the power input feed values the movement required to make small voltage adjustments is tiny, fractional, so it can sometimes take a while to hit the value you want if it is on the low side, just a few volts etc.

 

As to connecting the 16vac power supply if it is to be a permanent connection then I would say the quickest/easiest would be just to cut the plug off, strip the wires back, and stick them into the input socket. As it accepts AC it doesn't matter which way around the wires go whether the input is AC or DC.

 

If you want to be able to just plug it in and out at will, then you need to discover what plug type/size it is, there are many. Perhaps you could post a shot of it to give us an idea. I would guess it's the common type used for laptops and lots of similar electronic devices. There are myriad sizes used with these. Maplin used to be handy for sorting things like this when you weren't sure what you needed.

 

Bob

 

P.S. Oh I should add that if you want it to supply a fairly large continuous current then you will need to put a heatsink on the LM777 - the flat transistor type device at the top of the picture. It will rapidly overheat otherwise (Guess how I know) but for small bursts of current or just low LED values it's not required.

 

Edited August 23, 2022 by Izzy
add postscript

[Ian Morgan]

A couple of photos may help. If the power supply has a typical 'barrel' connector, you need to determine the diameter of the barrel and the pin, as various combinations are available.

 

 

[Nig H]

3 hours ago, Ian Morgan said:

A couple of photos may help. If the power supply has a typical 'barrel' connector, you need to determine the diameter of the barrel and the pin, as various combinations are available.

 

 

Hello Ian and Izzy,

 

Here is a photo showing the power supply box, the socket adaptors, and the Velleman unit, which looks like the one Izzy kindly pictured above.  

 

 

I'd prefer not to chop the power unit cable up and that's why I'm trying to find some sort of adaptor to connect the units. Maybe I could get a jack plug and route some wires from it to the Velleman?

 

Nigel Hunt

[Wotan]

I have a question?

I have one of the latest batch of GF Class 37’s  which is giving me some problems.

There’s an intermittent short occurring with the replacement association wheels fitted. which I think is happening when the centre axles come in contact with the centre wheel pickup ??? This doesn’t happen when the original n wheels are put back in????

has anyone found this or do I have an odd one??? Hope that makes sense and the pic helps explain 🙄

yours scratching his head 

michael 

[Izzy]

I've hit this problem in the past with my CL31's. The original centre axle wheels don't have the boss on the back like the 2mm ones do so they don't touch the contacts strips. However the 2mm ones do and cause a short. One answer is to paint the area around the contact strips and the boss on the wheels. If this doesn't work then overlaying something insulating might. Or cutting/filing the contact strips but means removing them to do it, and they are soldered into place. I cheated in the end, re-machined the original wheels to 2FS and used them. No easy answers with this.

 

Bob

[Chris Higgs]

2 hours ago, Nig H said:

Hello Ian and Izzy,

 

Here is a photo showing the power supply box, the socket adaptors, and the Velleman unit, which looks like the one Izzy kindly pictured above.  

 

 

I'd prefer not to chop the power unit cable up and that's why I'm trying to find some sort of adaptor to connect the units. Maybe I could get a jack plug and route some wires from it to the Velleman?

 

Nigel Hunt

 

You could maybe break open one of those 5 adaptors to leave you with a plug that goes into the power cable, and then solder wires from it to the board.

 

Chris

[2mmMark]

2 hours ago, Nig H said:

Hello Ian and Izzy,

 

Here is a photo showing the power supply box, the socket adaptors, and the Velleman unit, which looks like the one Izzy kindly pictured above.  

 

 

I'd prefer not to chop the power unit cable up and that's why I'm trying to find some sort of adaptor to connect the units. Maybe I could get a jack plug and route some wires from it to the Velleman?

 

Nigel Hunt

My advice would be to get a mono 3.5mm jack socket, either panel mount or inline depending on where you want to use it. Solder a pair of wires to it and connect them to the AC input of the Velleman.  Being AC, it doesn't matter which way round you connect them.  Then use the bigger of the jack plug tips to feed power.   If you want to retain the tip in place, some heatshrink tubing over the inline connector will do the job.  Failing that, a smear of silicone sealant will do the same thing.

A lot of DC devices (like the little Medvend controllers) have round sockets for the barrel connectors, so using the jack plug avoids you accidentally plugging an AC supply into a DC device.

Mark

 

[Donw]

My first impression is that I would be wary of anything  with such a poor description on the packaging I am assuming it is not intended for 240v mains. However it may well be sound electrically. The packaging suggest the input and output are both AC so I would check that first because you most likely need a DC output. It looks to me that you are offered a range of jack plugs and you could find the size to fit what you want.

Bob picture is most helpful. I am slightly puzzled by his mention of adjusting the current. I would have presumed the setting changed the voltage and the current depends on the load subject to a maximum  of 1A. Perhaps I am missing something. 

 

Don

[Izzy]

1 hour ago, Donw said:

M

Bob picture is most helpful. I am slightly puzzled by his mention of adjusting the current. I would have presumed the setting changed the voltage and the current depends on the load subject to a maximum  of 1A. Perhaps I am missing something. 

 

Don

 

No, your right Don, I meant voltage. Sorry.

 

Bob

[Winchat]

8 hours ago, Nig H said:

Hello Ian and Izzy,

 

Here is a photo showing the power supply box, the socket adaptors, and the Velleman unit, which looks like the one Izzy kindly pictured above.  

 

 

I'd prefer not to chop the power unit cable up and that's why I'm trying to find some sort of adaptor to connect the units. Maybe I could get a jack plug and route some wires from it to the Velleman?

 

Nigel Hunt

 

Nigel

 

You probably need a barrel jack to wire connector.  Connection is self explanatory.  I have attached a photo of one but I am not sure where you would get one in the UK.

 

Kind regards

 

Geoff

 

 

 

 

[Donw]

7 hours ago, Winchat said:

 

Nigel

 

You probably need a barrel jack to wire connector.  Connection is self explanatory.  I have attached a photo of one but I am not sure where you would get one in the UK.

 

Kind regards

 

Geoff

 

 

 

 

 

Ebay  I have bought some. I generally look for a uk posting you pay more than if from china but it avoids problems

 

Don

[ShadowinLinby]

Wotan - having looked at the photo of your class 37 it looks as though the PB contact on the front right wheel is bent out of position on is bearing on the wheel tread rather than on the back of the wheel. Don't know if that is causing your problems.

 

ChrisB

[Wotan]

No ShadowinLinby 

perhaps a bad photo but sorry your deduction is not correct 😁 that has nothing to do with it. 

Just to clarify my original point there is an alteration in the pick up design as noted and a similar problem by Izzy . The only way I can see to making it work is to remove the fitted pick ups file quite a large section away and refit which is never going to be as good as it was in the first place but thank you for your comment 

 

as an afterthought here’s the offending axle slot the slot if fine for the factory fitted wheel but the association one with the boss simply cover most of the side causing the short filing that away is not an easy operation 

 

michael 

Edited August 24, 2022 by Wotan

[Chris Higgs]

2 hours ago, Wotan said:

No ShadowinLinby 

perhaps a bad photo but sorry your deduction is not correct 😁 that has nothing to do with it. 

Just to clarify my original point there is an alteration in the pick up design as noted and a similar problem by Izzy . The only way I can see to making it work is to remove the fitted pick ups file quite a large section away and refit which is never going to be as good as it was in the first place but thank you for your comment 

 

as an afterthought here’s the offending axle slot the slot if fine for the factory fitted wheel but the association one with the boss simply cover most of the side causing the short filing that away is not an easy operation 

 

michael 

 

Surely you can just stick some Sellotape over the contacts around the middle axle area?

 

Chris

[Wotan]

1 hour ago, Chris Higgs said:

 

Surely you can just stick some Sellotape over the contacts around the middle axle area?

 

Chris

Well now here’s the thing and perhaps after banging my head against a wall all day trying to be understood this might clear things up

i measured the distance between the boss of the association wheels and that came out on my set as 6.45mm 

 

the distance between my beefed up pick ups on this Farish model on the middle axle space came out at 6.77mm 

therefor I deduce it will certainly not help having a further barrier of kapton/sellotape 

the bosses clearly are a problem as the chassis stands 

perhaps that’s enough of this saga now ???

michael 

[Yorkshire Square]

58 minutes ago, Wotan said:

Well now here’s the thing and perhaps after banging my head against a wall all day trying to be understood this might clear things up

i measured the distance between the boss of the association wheels and that came out on my set as 6.45mm 

 

the distance between my beefed up pick ups on this Farish model on the middle axle space came out at 6.77mm 

therefor I deduce it will certainly not help having a further barrier of kapton/sellotape 

the bosses clearly are a problem as the chassis stands 

perhaps that’s enough of this saga now ???

michael 

 

The boss is part of the anodised axle and therefore should be electrically insulated. In the unlikely event that the anodising has worn away on both bosses the 12V would still need to arc across the 0.3mm gap.

 

Have you checked the wheesets for non-continuity across the wheelsets? You might just have a faulty set.

[Caley Jim]

2 hours ago, Wotan said:

i measured the distance between the boss of the association wheels and that came out on my set as 6.45mm 

the distance between my beefed up pick ups on this Farish model on the middle axle space came out at 6.77mm 

therefor I deduce it will certainly not help having a further barrier of kapton/sellotape 

Thinner than sellotape or Kapton tape is to cut a piece of tissue paper to fit round the slot, lay it in place and flood it with cyano.  That is the method I use to insulate the insides of splashers, and anywhere else it's needed, on my locos.  Measuring some tissue I have it comes out at .06mm for 4 layers, so c .015mm thick, which isn't going to cause any interference.  If the piece you fit is a bit too big, it's easily trimmed back with a sharp scalpel.

 

Jim

Edited August 24, 2022 by Caley Jim
Typos