Stanier 8F in S7

Discussion in 'S7 Group' started by DavidinAus, 8 February 2014.

  1. DavidinAus

    DavidinAus Western Thunderer

    I decided for some unknown reason to switch to the tender again. Perhaps because having succeeded with the brakes on the locomotive, I wanted to see if I could do them on the tender whilst the technique was still in my memory! So I measured the clearances, and found to my delight that no adjustment was really needed for ScaleSeven: the brake hangers could be soldered into the inner chassis frame and could be adjusted easily to be the correct clearance for the S7 wheels. Excellent. So I insulated the faces of the brake shoes as before, soldered the brake hangers and retried the running of the tender frames - it still works!
    Next in the instructions is the water scoop lift gear. This proved to be a real challenge for me. There are times when I wish I was living in the UK (though not many ....) - the instruction sheet is really deficient in this section: "assembly is per diagrams and photos"; two unlabelled pictures and some difficult-to-decipher diagrams. I'm rewriting the instructions for David Sharp as I go, and really whatever I write will be an improvement here! It would have been much easier to be able to look at the real thing, but instead I had to look on the 'net for drawings and pictures. It was almost too obscure even for the ubiquitous WWW: Google Images of "Stanier tender water scoop gear" produces almost no useful images! I eventually found some useful stuff - Isambarduk's pictures of his model 3500 gallon LMS tender (thank you, David), and most useful were pictures of the Duchess and its tender in a Birmingham museum. I had to work out from their appearance what all the parts were for, and then how they go together. I hope I was right.

    Small Water scoop mech 001.jpg

    The mechanism is mounted under a crossmember of the inner chassis (even this has to be deduced as it is not in the instructions), and appears to be a rod or axle (moved by a long control beam from the front of the tender) on which a number of cranks are mounted. The ones at the rear end (right of photo. above) are aimed to lift the water scoop itself.
    On the same axle are mounted levers which lower another device into the water troughs, the levers seen in the middle of the mech. and protruding to the left in the photo. below.

    Small Water scoop mech 002.jpg

    I'm not sure what this device did in real life - I guess that it was a deflector to channel more water from the edges of the water trough into the scoop?

    There is also what I think must be a balance weight for the water scoop attached to the axle, seen in the middle of the mech. above (probably in the wrong position). I added to the thickness of the etched parts which represent this.

    To make up the mechanism as seen above needed three parts to the frame (25 x 15 x 15mm), a piece of 1.6mm dia. rod, twelve tiny bits of etched nickel silver, half-a-dozen 1/32 brass pins and a HUGE amount of patience. Here it is in position:

    Small Water scoop mech 003.jpg

    Some of the brake gear is also seen, but no water scoop as yet.
    If my deductions were wrong about where everything goes, I'm not sure that I really want to know ....

    David
     
    Last edited: 3 May 2016
  2. mickoo

    mickoo Western Thunderer

    David,

    The inverted U shaped deflector is called an economiser as far as I can remember, it's job as you rightly surmise is to direct a stream of water into the scoop, some are tapered and the tapering accelerates the water flow up the scoop and fill pipe, handy if your a freight engine lumbering along at 25-30 mph.

    Time consuming as it is, it does look the business :thumbs:

    MD
     
  3. DavidinAus

    DavidinAus Western Thunderer

    Now in some respects I am very pleased with my progress, but in other respects quite distressed and appealing for help!
    I have finished the tender, with reservations - it doesn't run as well as it should and needs to!

    Small Tender complete not painted 05.jpg

    As you can see, it looks OK (given that it isn't painted).
    However even on my S-shaped test track it de-rails: there is a compensation mechanism which should allow there to be free movement of the rear four wheels almost independent of each other but this doesn't seem to work completely effectively. If it did, the six wheels would all be always in contact with the rail. However the front axle seem to be able to have one rim off the rail, and so with the small S7 flanges, it de-rails. Adding weight to the front end of the tender makes no difference.
    If anyone out there is familiar with the MOK mechanism, could you offer some suggestions, please? The rear four wheels have a mechanism which allows each side pair to rotate about a rod, and each pair can move up and down relative to the other, and to the chassis itself. Each end of each axle is held in a "loose link" which allows the axle to change angle relative to the chassis: necessary to allow free movement and angulation. It is very clever, but I feel that it cannot be working perfectly, because if it were working OK, it would mean that the rear four wheels were always in contact with the rails whilst the front (fixed) axle was the other two points of a triangle able to fit to any uneven-ness in the track.
    I had been so careful .... !
    At every stage of construction up to the stage seen in my post from 3rd May I had run the tender chassis up and down behind the locomotive and it ran without problems. However at the next stage it becomes necessary to put it all together, take a deep breath and solder it up in such a way that it cannot be taken apart to adjust it. By the time I have the water-scoop parts and the split-axle pick-up components all crowded together, it looks like this:

    Small Tender complete not painted 06.jpg

    I dread having to unsolder it and take it all apart again!
    It looks so good.

    Small Tender complete not painted 03.jpg

    However looks aren't everything, and unless additional lubrication of the moving parts frees up the mechanism and allows it to run over uneven track, what else can I do?
    Always, any assistance or suggestions gratefully received !


    David
     
    Len Cattley and Dog Star like this.
  4. markjj

    markjj Western Thunderer

    Have you packed out the axles that should float with washers to take up the side play? If you have you may be restricting the free movement by making it too tight.. It's hard to see any other reason from your photos
    Mark J
     
  5. DavidinAus

    DavidinAus Western Thunderer

    There are no packing washers. There's very little side-play in the chassis with S7 dimensions.

    D
     
  6. Ressaldar

    Ressaldar Western Thunderer

    Hi David,

    probably a silly question but, is the 'problem' there when it runs as just a chassis?

    regards

    Mike
     
  7. DavidinAus

    DavidinAus Western Thunderer

    A good thought. so I have just tried.
    I have done my best to make sure that everything is square and even, but you could easily be correct that the body distorts the chassis.
    However, no, taking the body off makes no difference.

    Small Tender complete not painted 07.jpg

    It still de-rails. here's a better picture of the chassis:

    Small Tender complete not painted 08.jpg

    David
     
  8. Peter Insole

    Peter Insole Western Thunderer

    David, Looking at your underside photo, the centre axle appears to be out of alignment and is sitting low in the last shot. The leading nearest wheel is clearly lifted off the rail on what looks like level track.

    Hope this helps your investigation?

    Pete.
     
  9. Dog Star

    Dog Star Western Thunderer

    What track radius are you using for your test?

    What side play do you have on each axle?

    With the tender sitting on a piece of flat glass... which tyres are touching the glass?
     
  10. DavidinAus

    DavidinAus Western Thunderer

    I agree, Pete, and had seen that myself. However the compensation mechanism should stop that happening. Essentially if this mechanism works as it should, the four rear wheels should fit any variation in trackwork and essentially form a single point of contact with the track level. The centre axle should be able to move upwards if necessary to allow the other axles to be relatively lower. That is why I wonder if it is either just stiffness in the mechanism, or some restriction in the way that the mech. works. The trouble is I don't know how to test these theories!

    D
     
    Last edited: 11 July 2016
  11. DavidinAus

    DavidinAus Western Thunderer

    Good thought, DogStar.
    2 metres radius.
    Virtually no side-play - it's not possible!
    More importantly, on a flat piece of granite, the front left wheel doesn't sit flat on the surface! All the others are in contact, and remain so even if I press down on the front left corner to force the wheel into contact with the surface.
    So, why that should be, and what do I do .... ?

    D
     
  12. Steph Dale

    Steph Dale Western Thunderer

    David,

    If I have problems like this (tight coupling rods, etc) I roll the chassis along the the track until it begins to stiffen up/jam. I can then use a piece of wire, hand held, to tap the various parts (wheels, compensation beams, coupling rods, etc). The one that doesn't move when lightly tapped with the wire is the part that needs investigating.

    Steph
     
    simond likes this.
  13. DavidinAus

    DavidinAus Western Thunderer

    Thanks, Steph. All the wheels move freely, though, and in testing the components of the compensation mechanism I wouldn't know which way to try to move them. I am reluctant just to put oil on every moving joint, but perhaps that's the only way forward.

    D
     
  14. Ian@StEnochs

    Ian@StEnochs Western Thunderer

    Hi David,

    I have never had a problem with tenders and curves, locos yes, but not tenders.

    Check that your axleboxes are not jamming in their guides. They should drop when you lift the chassis off the ground. Sometimes the guides can be slightly tapered which lets the box stick at top or bottom. A bit of slop is not a problem on carrying wheels.

    Another bit to check out is the clearance around your brake shoes. I file the back of the shoe back to give flange clearance if the wheel tilts or moves from side to side on a curve. Epoxy on the rubbing face will prevent shorts but it is also less slippy than metal and can 'pick up' the wheel.

    Ian.
     
  15. DavidinAus

    DavidinAus Western Thunderer

    Good thought, Ian, and I will try the brake shoes/blocks - I've made them really close for realism. If you look at my post dated 21st September I have plastikard linings for the shoes which could easily be cut back a little if needed.
    No axleboxes. The compensation mechanism seems to move very freely up and down.
    It'll have to wait until tomorrow, though - it's late-night here in Aus.


    David
     
  16. Dog Star

    Dog Star Western Thunderer

    An earlier post says that the front axle is fixed with the equalising arrangement at the rear providing the third leg of the milking stool. The post that I have quoted implies that the rear two axles are providing two points of contact with the RH front tyre acting as the third point. Seems to me that you need to re-visit the instructions to see what might cause the front axle to be non-parallel to the two rear pivot points.
     
    Scale7JB likes this.
  17. Scale7JB

    Scale7JB Western Thunderer

    Definitely agree with Graham there..

    The ride height of both sides of the fixed axle is probably the most important part of the entire chassis.

    JB B
     
  18. DavidinAus

    DavidinAus Western Thunderer

    Sounds like good advice.
    Sadly, as ever, though, it means that I will have to take apart what I have done so far. It makes sense to do so, though, for whatever cause the problem has - the chassis worked OK until the point at which I fixed the outer frame in place, soldered up the brake stretchers and Araldited the axle boxes to the outer frame. Somewhere in this process I must have distorted the chassis or introduced some interference with the compensation mechanism. The outer frame is screw-fitted onto the inner. If I loosen that and it runs properly again, I will know what the problem is, even if I will not know how exactly to fix it.
    So I have at least two theories to work on: non-parallel front axle and compensation axle (possibly by distortion of the inner frame by the outer), and brake shoes or something else rubbing.
    Thank you to everyone for the advice so far.

    At least the body looks good!

    D
     
  19. Dog Star

    Dog Star Western Thunderer

    Another possibility - each compensation beam has a central pivot whereby the beam is located in a side plate. If those pivot points are not at the same distance from the datum / base / glass plate then the effect is to "twist the frame" relative to the front axle - or cause the front axle to appear to be twisted relative to the compensated centre / rear axles.
     
  20. DavidinAus

    DavidinAus Western Thunderer

    This is turning into a major problem with major reconstruction needed, I fear.
    I have taken the chassis and frames apart, unsoldering lots of the water scoop mechanism and brake rods as I do it, and found that the problem lies in the inner frames. Even with the outer frame removed the inner frame rocks, standing on the flat surface with the one of the front wheels off the ground. I had tried running the inner frame on its own before assembling the rest, and it seemed to run OK. It still does, I checked, even though it seems Graham/Dog Star is right and there must be an angle between the front axle and the compensation beam.
    It seems to be counterintuitive that it should run better without weight on it, but that seems to be the case.
    I constructed the inner chassis using Steph's method to allow the use of split axles, and this must be where misalignment set in. I'll send some pictures about the problem when my camera battery has recharged, but this is looking seriously difficult to correct. Even apart from having to take an awful lot of the construction apart, there is quite a bit of epoxy to undo, as well as solder. And then how do I ensure that the axles are exactly parallel?
    Pictures tomorrow, and then lots of help, please!

    David
     
    Dog Star likes this.