Agenoria WR 1366 Pannier for Pencarrow Bridge

[Miss Prism]

I can't really see the point of "4-point" compensation

The advantage of 4-point over 3-point relates to lateral stability - it allows a greater freedom of the centre of gravity placement compared to 3-point. This is the achilles heel of 3-point, where, depending on the where the single beam is in the loco and its relationship to the CofG, locos can become unstable in the roll plane. Viz the preproduction version of Chris Gibbon's 0-4-2T, which fell off on curves, as predicted, and he redesigned it.

 

As Chaz notes, natural axle to bearing clearances and the relatively small vertical axle movements allows 4-point to work well, even if the bearings are secured solidly in their beam (as in this case). In 7mm, the approx 5x loco weight compared to 4mm does help a bit in flexing the beams if they are thin, but I don't regard such flexing as an essential.

 

In the general case, I feel a 4-point strategy is definitely superior to a 3-point one.

 

 

P.S. 40:1 feels a bit fast to me for a loco that probably never exceeded 20mph. A larger slower motor might be the solution?

 

 

[2ManySpams]

Try this linkhttp://www.metalsmith.co.uk/loco_buildingtesting_7mm_scale.htm or herehttp://www.meteormodels.com/www.meteormodels.gbr.cc/info.php?p=10

This is the simplest form of axle alignment (I think Alan Gibson might do them as well??) or if you are going to build a few locos you could try thishttp://www.avonsideworks.com/products.html

but it ain't cheap (& they get dearer!!)

I have one of these and swear by ithttp://www.hobbyholidays.co.uk/products.php?cat=32

But they don't seem to be making them at the minute

OR you could buy some 3/16 rod and make your own..........simples!!!

(Edit to include extra link cos I forgot about meteor models ones!!!)

Thanks for all the links. Can't help but notice the significant jump in price between the first two and second two options! I suspect I'll probably order one of the metalsmith ones for this toe dipping loco build.

[N15class]

JPL do a version using parts as per the first items but with a frame to get all holes level too. I will post a photo if you like as I use one.

[2ManySpams]

JPL do a version using parts as per the first items but with a frame to get all holes level too. I will post a photo if you like as I use one.

Yes please.

[The Nth Degree]

I understand we are talking of small movements of the axles, but does relying on the flexibility of the beams look like it's relying on a mechanical error, rather than something that's been designed? The reason I'm interested in this topic (having read all of the CLAG content!) is that I'm designing something for myself, and what I have seen so far relies too much on minimal bearing clearances and the springiness of metals (that aren't actually very springy) to function.

[N15class]

The instructions seem vague about fitting the bearings to the beams.  Am I correct in deducing that the bearings pass through the frames and are then soldered to the beams?  The beams are then trapped to the frames.  What do others think from what has been posted of the instructions?  There is a risk that the beams could be come soldered to the frames.  Also, careful cleaning will be required to remove flux trapped between the frames and beams.  

 

Then there is the qustion of bushes for the beams, which is a good modification.  That will require some reaming and the making of bushes.  If Chris is going to adopt this suggestion, it needs to be done now.

I have come across ones like this. the chassis holes are opened out to about a millimeter larger than they would normally be. Put a washer between the frames and beam. The use of phosphoric acid flux will stop any worries of leaving a residue, or as I do where possible use a screw and nut and make the beam removable and only fix after painting

[The Nth Degree]

The instructions seem vague about fitting the bearings to the beams.  Am I correct in deducing that the bearings pass through the frames and are then soldered to the beams?  The beams are then trapped to the frames.  What do others think from what has been posted of the instructions?  There is a risk that the beams could be come soldered to the frames.  Also, careful cleaning will be required to remove flux trapped between the frames and beams.  

 

Then there is the qustion of bushes for the beams, which is a good modification.  That will require some reaming and the making of bushes.  If Chris is going to adopt this suggestion, it needs to be done now.

Paul, the compensation unit is an entirely separate subframe that fits inside the loco frames. The only contact it makes with the loco frames is via the pivot rod/mechanism. The bearings must be soldered to the compensation unit and, ideally, not touch the loco frames at all – simply slide up and down the slot in the frames.

[N15class]

Here are the pictures. I build the frames then fit the bearings or horns. If fitting horns I use springs to gently push the them onto the frames whilst lining up and soldering. One of the axles goes through the hole that has the axle jig in it. stops everything falling of when moving it around.

 

 

[2ManySpams]

Paul, the compensation unit is an entirely separate subframe that fits inside the loco frames. The only contact it makes with the loco frames is via the pivot rod/mechanism. The bearings must be soldered to the compensation unit and, ideally, not touch the loco frames at all – simply slide up and down the slot in the frames.

 

Must admit that I read it the same as Paul - bearings passing through (but not soldered too) the enlarged hole in the frames, then the compensation beam. 

 

Very hard to tell but here's a photo extracted from the destructions. Not 100% sure what it shows but I don't think it looks like a separate unit (although we may be talking at cross purposes).

 

[Donw]

Quite a neat and simple idea. the jig will hold the axles in line vertically and the coupling ros will keep the horizontal spacing correct. If I didn't have one already I would try this.

Don

 

edit refers to Pete's photo of a jig

Edited July 10, 2014 by Donw

[2ManySpams]

Here are the pictures. I build the frames then fit the bearings or horns. If fitting horns I use springs to gently push the them onto the frames whilst lining up and soldering. One of the axles goes through the hole that has the axle jig in it. stops everything falling of when moving it around.

 

d.jpg

e.jpg

 

Just looked up JPL - seems to be a model shop in Manchester? 

 

Edit £30 + P&P - order placed.

[chaz]

I understand we are talking of small movements of the axles, but does relying on the flexibility of the beams look like it's relying on a mechanical error, rather than something that's been designed? The reason I'm interested in this topic (having read all of the CLAG content!) is that I'm designing something for myself, and what I have seen so far relies too much on minimal bearing clearances and the springiness of metals (that aren't actually very springy) to function.

 

trust me, the method works fine.

[chaz]

The instructions seem vague about fitting the bearings to the beams.  Am I correct in deducing that the bearings pass through the frames and are then soldered to the beams?  The beams are then trapped to the frames.  What do others think from what has been posted of the instructions?  There is a risk that the beams could be come soldered to the frames.  Also, careful cleaning will be required to remove flux trapped between the frames and beams.  

 

Then there is the qustion of bushes for the beams, which is a good modification.  That will require some reaming and the making of bushes.  If Chris is going to adopt this suggestion, it needs to be done now.

 

I reverse the bearings so that the flange is inside and the plain end projects through the frames. This means that you can solder the bearings to the beams off the job  - but jigging them to get the correct WB - and then insert the bearings through the holes in the frames - no risk of soldering everything up solid. You may have to slim down the bearings if they project too far and stop  the wheels fitting the axles correctly. (Have a look at the snap I posted a few posts back)

 

Bushes for the beams? If the pivot holes are not too big you can use Slater's crankpin bushes. I push these through from inside and tack solder them to a brass rod, not the frames. if you ever want to remove the beams you just cut through the rod and the pivot bushes will pop out. (You can see this in my snap.)

 

Chaz

[2ManySpams]

On the subject of cleaning up, Malcolm Mitchell once advised me to use ViaCal or similar as a cleaning agent, prior to washing in water.  It is a limescale cleaner.  I use another brand which comes as a spray.  Use an old stiff brush to get into the crevices.  Then rinse well with warm water and leave the work somewhere to dry.  In the winter, I put it on top of a radiator.  In the summer, requisition a small area in the airing cupboard.......

 

I used a Viacal type product to clean up the Toad B brake van - worked well. 

[2ManySpams]

I reverse the bearings so that the flange is inside and the plain end projects through the frames. This means that you can solder the bearings to the beams off the job  - but jigging them to get the correct WB - and then insert the bearings through the holes in the frames - no risk of soldering everything up solid. You may have to slim down the bearings if they project too far and stop  the wheels fitting the axles correctly. (Have a look at the snap I posted a few posts back)

 

Bushes for the beams? If the pivot holes are not too big you can use Slater's crankpin bushes. I push these through from inside and tack solder them to a brass rod, not the frames. if you ever want to remove the beams you just cut through the rod and the pivot bushes will pop out. (You can see this in my snap.)

 

Chaz

 

Now I can see that working really well. You've done this before haven't you ;-p

[Stubby47]

Have you seen this ? http://www.masterpiecemodels.co.uk/LITE-GWR-WR-1400-4800-5800/

[puddlejumper]

Have you seen this ? http://www.masterpiecemodels.co.uk/LITE-GWR-WR-1400-4800-5800/

Mmmmmm nice, only problem is I sold one of my kidneys already so raising the "how much????" could be tricky

Edited July 11, 2014 by puddlejumper

[Dazzler Fan]

The detail available at 7mm has always been phenomenal. However for.

the intended 4mm model, do you think they will now introduce 3D printed

assemblies in place of lost wax sprues, especially for the Backhead detail.

 

Noel

[2ManySpams]

Have you seen this ? http://www.masterpiecemodels.co.uk/LITE-GWR-WR-1400-4800-5800/

You bad man Stubzie, I'm not turning to the dark side ;-p

[2ManySpams]

Mmmmmm nice, only problem is I sold one of my kidneys already so raising the "how much????" could be tricky

Interesting that they also do an airsmoothed Bulleid...but that's two kidneys worth!

[Simond]

The advantage of 4-point over 3-point relates to lateral stability - it allows a greater freedom of the centre of gravity placement compared to 3-point. This is the achilles heel of 3-point, where, depending on the where the single beam is in the loco and its relationship to the CofG, locos can become unstable in the roll plane.

Miss P

 

I do agree with your concerns over lateral stability, see my earlier comments regarding 4-4-0 where the CoG may be near to or even ahead of the leading axle, & 4-6-0 locos, where the CoG will tend to get very near the mid point between the two front axles. In both cases, even if it is within the support triangle, here will be a real risk that hitting a corner at speed might easily lead to roll-over.

 

This is clearly one area where springing can have an edge over three-point compensation, and four point "quasi-compensation" would have an advantage - and Chaz, even my very small layout has some horrid twists after a few years - those of us who run in the garden will have undoubtedly experienced some less-than-perfect track too.

 

In these cases, it must be true that, at some places, only one axle is in proper contact with the rail on one side of the loco, and thus, however briefly, pick-up will suffer. If you're unlucky this will coincide with the chassis tightening up as the rocking beam bearing misalignment reaches a maximum, and disappointing running may well result. Worst case might lead to derailment, but this seems improbable with normal 0F flanges.

 

Whilst you, Michael Edge and Chaz all report successful outcomes, a little part of me says, "yes, ok, but it's still wrong", and personally, I would tend to try to modify the kit so I felt it was "more correct", but in the end, I guess it is a case of rule one. Assuming it is free running, it can't be worse than a rigid chassis so my advice to the original question would be , "build it as the kit was designed".

 

Best

Simon

[chaz]

 

a little part of me says, "yes, ok, but it's still wrong", and personally, I would tend to try to modify the kit so I felt it was "more correct", but in the end, I guess it is a case of rule one. Assuming it is free running, it can't be worse than a rigid chassis so my advice to the original question would be , "build it as the kit was designed".

 

Simon

 

before we worry too much about theoretical objections it might be well to remember that any working model has only a superficial resemblance to the prototype. Beneath the paint everything is "wrong" and numerous compromises will have been made. (Are your boilers made of steel and full of fire-tubes?) So we should design the frames so that they work as well as possible and can be built by ordinary mortals.

 

The choice comes down to some form of compensation or springing or a combination. Some of my locos are sprung, others have beam compensation. In terms of the amount of work involved in building them I don't think there is much to choose and I honestly don't think you can tell the difference when they are moving along the track. If I was building an 0-6-0 I would use twin-beam compensation with one rigid axle although springing would be fine. Certainly if I were building a kit which made provision for beams it would seem perverse to opt for springing (but I have done sillier things with models).

 

Chaz

[2ManySpams]

And don't forget the (lack of) experience and skill of the person building this kit. It is my first venture into this complex arena and my workbench is stocked to build plastic buildings and create scenery. I've much to learn and there will need to be much walking before contemplating even a little jog! Thanks all for your continued advice.

[2ManySpams]

Well the posty has just been and has delivered a chassis alignment jig from JPL. I only ordered it yesterday afternoon. Cracking service!

[Simond]

Chaz.

 

As I said, personal choice is the final arbiter, hopefully supported by good advice and accurate info.

 

In this case the "wrong" is that four-point is not three point compensated, the issue is physics, not prototype fidelity. It's not opinion, it's fact. But of course, it might not matter - the advantage of "right" over "nearly right" might well be negligible, or at least not worth the added effort.

 

In terms of workload, I think springing is quite a bit more hassle to get right, particularly if you build "floating" rather than "sprung one way", and for that reason, I'm inclined to compensation

 

Having in mind Chris' concerns over his experience, I'm sure building it four point compensated per the instructions will give a satisfactory result, and whether I would do something different, sillier or not is really only of academic interest. (And I too have done "silly")

 

Chris

 

I haven't used the jig, but I expect it will be easier than the rubber band, paper clip, hair grip & balancing acts that I resort to!

 

Good luck, looking forward to seeing how you get on

 

Best

Simon