Any Question Answered

[CF MRC]

I would be really careful at going anything less than 18” radius for 2mm FS.  Stewart Hine used to say that the rule of thumb was a foot for every scale millimetre: hence a perfectly safe ruling radius for ALL 2mm stock is  2’ (4’ in 4mm etc).   600 mm is the ruling radius on CF: also worth remembering that it very easy to get tight spots on hand built track.   Mons Meg tries to straighten out 18” radius track.

 

Tim

Edited May 13, 2019 by CF MRC

[Lacathedrale]

OK, maybe for the sake of an extra foot I should just stomach it, then! Thank you!

[MrSimon]

Hi all,

 

What's the best way to insulate a loco chassis from the body?  Also, is it best to insulate the whole body/chassis or just where contact is likely?

 

Thanks in advance

 

Simon

[Caley Jim]

19 minutes ago, MrSimon said:

What's the best way to insulate a loco chassis from the body?  Also, is it best to insulate the whole body/chassis or just where contact is likely?

I use thin tissue paper glued on with cyano. Easiest way is to cover the places on the top of the chassis, or the underside of the footplate, where you think contact is likely and then flood the tissue with the cyano.  Once it's set you can trim the tissue.  I've also used little bits of tissue to line the insides of splashers, fixed in the same way.

 

Another idea is to make your frames 10 thou or so shallow and then you can glue 10 thou styrene on top of them where the body sits on them.

 

Jim

Edited May 26, 2019 by Caley Jim
edited for typo

[Lacathedrale]

2mm association instructions suggested 9 or 9.5mm wheels for the Jinty chassis that is available from Shop 3 - I used these and found that I needed to grind away a fair bit of metal from the inside of the body/splashers for them to fit.  The 57xx conversion has the same equivocal recommendation, does it also require clearing out white metal from the loco to fit the 9.5mm wheels? Since I have the 9.5's to-hand, I would rather not order another three axles + quartering jig plates if I don't need to, but I'm not sure if I want to push my luck again with a rotary tool!

Edited May 27, 2019 by Lacathedrale

[richbrummitt]

14 minutes ago, Lacathedrale said:

2mm association instructions suggested 9 or 9.5mm wheels for the Jinty chassis that is available from Shop 3 - I used these and found that I needed to grind away a fair bit of metal from the inside of the body/splashers for them to fit.  The 57xx conversion has the same equivocal recommendation, does it also require clearing out white metal from the loco to fit the 9.5mm wheels? Since I have the 9.5's to-hand, I would rather not order another three axles + quartering jig plates if I don't need to, but I'm not sure if I want to push my luck again with a rotary tool!

 

Both my panniers have 9mm wheels. You'll be able to work out any problem by trialling the wheels in the chassis against the body since you have the larger size wheels to hand. IMO the 9.5mm wheels will be a bit big...

[Izzy]

Don’t wish to cause any possible confusion, but 9.5’s are the size fitted to the latest version Jinty and is what I used with the conversion parts, (mentioned in the 3F/4F to 2FS thread). Not sure if this would still work with a combination of the newer body with an etched chassis but would think it should. The footplate is still metal, but perhaps more finely cast as regards splasher thickness than the older one.

 

Izzy

[Argos]

Has anyone had any success with the new 3d printed universal joints?

 

I'll freely admit to being quite a ham-fisted modeller but have broken 3 joints now.

Two whilst installing them into the socket (and have had to drill them out) one while cutting off the sprue.

 

They feel too brittle to use.

If anyone had had success could the share their secrets?

 

I've also had one of the socket break whilst running with a wire installed.

 

Again I refer back to my ham-fisted comment rather than this being a criticism of the product. 

[Nick Mitchell]

1 hour ago, Argos said:

Has anyone had any success with the new 3d printed universal joints?

 

Yes!

It may just have been beginner's luck, but the one and only one I have used worked a treat.

There are bits in episodes 20 and 21 of my Jubilee videos which show in excruciating detail what I did with it.

If I hadn't been making the video, I'd have almost certainly made a brass version in my lathe from a pair of 7mm handrail knobs, however, I would have no qualms about using the printed ones again. They have the distinct advantage that the shaft doesn't fall out of the housing.

 

Nick.

[queensquare]

1 hour ago, Argos said:

Has anyone had any success with the new 3d printed universal joints?

 

I'll freely admit to being quite a ham-fisted modeller but have broken 3 joints now.

Two whilst installing them into the socket (and have had to drill them out) one while cutting off the sprue.

 

They feel too brittle to use.

If anyone had had success could the share their secrets?

 

I've also had one of the socket break whilst running with a wire installed.

 

Again I refer back to my ham-fisted comment rather than this being a criticism of the product. 

 

Afraid Ive not tried them, and to be honest, I'm not likely to - give me brass tube/bar every time. To me, trying to 3D print part of the drive mechanism is exactly the sort of thing I was talking about in the latest MRJ editorial.

 

Jerry 

[Argos]

Thanks both,

 

I am back to brass wire and section have now broken all six 3d printed male ends.

I've also manage to crack a couple of the female ends  one will drilling out the other when mounted and using a twisted wire to dirve..

 

Obviously too delicate for my ham-fists.

Edited May 31, 2019 by Argos

[Caley Jim]

Like Jerry, I'm unlikely to try them.  My own 'system' is to have the shafts at the front of the tender and the rear of the loco end flush with their respective bearings.  The shafts each have a slot cut lengthwise about 1.5mm into them.  The driveshaft is a piece of 8thou steel guitar string with a ring formed on each end and this squashed or filed a bit thinner.  The shaft is c1mm shorter than the distance between the inner ends of the slots.

 

It does have the disadvantage that the shaft comes out when to separate the loco and tender, but it's simple and works well in my three tender locos.

 

Jim

Edited May 31, 2019 by Caley Jim
Edited for typos

[Nick Mitchell]

54 minutes ago, queensquare said:

To me, trying to 3D print part of the drive mechanism is exactly the sort of thing I was talking about in the latest MRJ editorial.

I enjoyed reading your editorial, Jerry. While I agree entirely with the overall sentiment, I must confess that I've been wondering whether 3 printing parts for a drive mechanism might actually be the answer to a conundrum I've been pondering on and off for a number of years.

 

The scenario I'm thinking of would require 2 different sized spur gears joined together as one, but free to rotate around an axle. Moulded acetal gears can't realistically be glued, and I don't see how I could successfully solder brass gears together like that. Such gear pairs as I have seen in the past have always been plastic and moulded as one unit.

I remember Ian Morgan reporting on his successes with 3D printed gears for a Dapol Terrier in the 2mm Magazine about 5 years ago. I wonder how they have stood up over time.

I suppose different plastics for printing will have different properties. Some of the materials Shapeways have claim to be suitable for mechanical parts and have "good" chemical resistance. I don't think there is anything wrong with plastic parts per-se. We all use plastic muffs in our drive mechanisms after all.

 

I still think the bit of the hobby I enjoy most is soldering things together, however.

[2mm Andy]

I think part of the problem here is the lack of instructions on how to use the UJs. Having discussed this with the designer, the intention is for the male part of the UJ to be drilled full depth (0.3mm or 0.4mm) and the wire drive shaft glued in and then trimmed as required. This gives added strength, especially where the 'ball' of the UJ meets the shank. The female part should be drilled to fit the motor/gearbox shaft (as per Nick's Youtube videos). You do need to be careful when drilling all of the holes, and not to force the drill too hard. We'll try to get some notes added to the website shop listings.

 

As regards the suitability of 3d printing and plastics, etc., please don't assume that these weren't thought about, tested to destruction, refined, etc. Bear in mind also that different parts of a drive mechanism are subject to different stresses. I would also add that the designer is one of the keenest proponents of 'multi-media' models in 2mm that I know of. The UJ design in the shop has been tested in different types of locomotive, and tweaks made to the design in light of experience (I think the design in use is version 4). There are also similar designs of UJs moulded in plastic in use in RTR models, and available from other suppliers such as N Brass Loco if you find the 2mm ones too delicate and don't want to make your own.

 

I hope that answers some of the comments/concerns.

 

Andy

[Chris Higgs]

On 28/05/2019 at 09:16, Izzy said:

Don’t wish to cause any possible confusion, but 9.5’s are the size fitted to the latest version Jinty and is what I used with the conversion parts, (mentioned in the 3F/4F to 2FS thread). Not sure if this would still work with a combination of the newer body with an etched chassis but would think it should. The footplate is still metal, but perhaps more finely cast as regards splasher thickness than the older one.

 

Izzy

 

Generally if the loco has a certain size of wheel fitted in N then a 2FS replacement to the same or smaller dimensions is going to fit fine.

 

Unfortunately old-style Farish tended to all have very undersized wheels.

 

Chris

[Argos]

11 hours ago, 2mm Andy said:

the intention is for the male part of the UJ to be drilled full depth (0.3mm or 0.4mm) and the wire drive shaft glued in and then trimmed as required. This gives added strength, especially where the 'ball' of the UJ meets the shank.

 

That makes a lot of sense and would reinforce the joint at the point I keep getting the breakage.

I did contemplate trying to drill just the head, but accurately drilling the ball was beyond me as I couldn't find a way to clamp it without damaging the spines.

[oily]

Does anyone know if an etch is available from any source  for a 2mm scale GWR 4-4-0 (Bulldog) or an SR 4-6-2  Spam Can (West Country, Battle of Britain, Merchant Navy classes)

I've found the Worseley Works  BoB chassis etch but nothing else so far.

Many thanks

Oli

[Izzy]

10 hours ago, Chris Higgs said:

Unfortunately old-style Farish tended to all have very undersized wheels.

Chris

 

Yes, I recently saw a photo of a original Farish J69. I had a couple when they first came out - in the GER blue - but had forgotten just how small the actual wheels were compared to the huge (pizza cutter) flanges. Still remember them with fondness even though most little Arnold tank locos with even smaller wheels could knock spots off them in respect to running qualities!

 

Izzy

[Nigelcliffe]

On 31/05/2019 at 18:22, Nick Mitchell said:

I enjoyed reading your editorial, Jerry. While I agree entirely with the overall sentiment, I must confess that I've been wondering whether 3 printing parts for a drive mechanism might actually be the answer to a conundrum I've been pondering on and off for a number of years.

 

The scenario I'm thinking of would require 2 different sized spur gears joined together as one, but free to rotate around an axle. Moulded acetal gears can't realistically be glued, and I don't see how I could successfully solder brass gears together like that. Such gear pairs as I have seen in the past have always been plastic and moulded as one unit.

 

 

Random suggestions on how to fix the two gears together:

 

a - pin them with multiple small holes drilled through in coordinate fashion, and small glued in pins.  Coordinate drilling could be done by temporary fixing gears to an axle whilst drilling them, then unfixing the temporary axle - Shellac being one of my favourites for this sort of thing. 

b - fix them to a common hollow (tube) axle, suitable to rotate on your mechanism axle

c - variant of b - fix together at faces with solder, onto tube axle, then drill tube axle out completely (requires a bit of thinking about workholding).

 

Or, in 3D printing, don't just look at Shapeways.   There are other firms with a similar service offering different materials.

 

 

- Nigel

[Caley Jim]

1 hour ago, Nigelcliffe said:

b - fix them to a common hollow (tube) axle, suitable to rotate on your mechanism axle

Another variant of this would be to temporarily mount them on an axle from a material which will not take solder, such as aluminium or some types of steel ( or even a piece of wood dowel?).  You could also grease the axle before mounting the gears.  Applying solder paint to the faces first would mean that there was minimal solder and so less chance of clogging up the teeth.

 

Jim

[richbrummitt]

I had it recommended to me by people who do 3D printing as a service with (20+) years of experience that reversing the drill is close to the silver bullet when opening out holes. Ordinary drills are highly likely to catch with bad outcomes for the workpiece. An alternative that most of us won't have is the ability to take the edges of the cutting faces of the driver bit to prevent catching, which is something I have seem done in the workshop when drilling certain materials as a matter of course.

[Lacathedrale]

For those of you who use the Easitrac tie bars, is there any good solution to holding the switchblade plates against the tie bar in a vertical axies? For some unknown reason, one of the switchblades on a turnout I've just replaced is curving up by 0.5mm or so, which means when the turnout gets set, the plate jams against the adjacent rail instead of moving underneath it. I've used rail and PCB sleeper with no chairplates, and left the switchblades unsoldered/free to move where there would be slide chairs.  If I poke at the end with the tip of a file, it dings underneath and functions how would one hope until it's set in the opposite direction and pings out again.

[Ian Smeeton]

Would it be possible to solder a piece of brass or n/s to the switch rail which is long enough to slide under the stock rail.

 

Regards

 

Ian

[Lacathedrale]

Ah, what a cracking idea! I will give that a shot and report back.

[Chris Higgs]

On 01/06/2019 at 16:59, oily said:

Does anyone know if an etch is available from any source  for a 2mm scale GWR 4-4-0 (Bulldog) or an SR 4-6-2  Spam Can (West Country, Battle of Britain, Merchant Navy classes)

I've found the Worseley Works  BoB chassis etch but nothing else so far.

Many thanks

Oli

 

Not that I am aware of. I do harbour vague hopes of doing etched frames for a Bulldog/Dukedog with appropriate printed boilers but it may well never come to anything.

 

Chris