7mm Loose Ends

D1054

Western Thunderer
Assuming that each fan in a pair has the same twist to the blades.... if the twist is not the same then the blades ought to rotate in different directions.

Young Ian has a lot to answer for... and a lot of answers to questions!
Answers will follow soon...... In the meantime, the fans are identical and all rotate on the same direction. The real problem is that the two at each end, each rotate at different speeds! Now I've not cracked that one yet.......

Looking forward to seeing this rake take shape Cynric!
 

Dog Star

Western Thunderer
The real problem is that the two at each end, each rotate at different speeds! Now I've not cracked that one yet.......
Put a cheap and simple DCC decoder at each end, link one fan drive to each chip... adjust speed tables to suit.

regards, Graham
 

28ten

Guv'nor
I have spent some time reverse engineering the kits into separate boxes, so I have piles of bodies, castings floors etc the idea being to do the same operation multiple times thus saving time changing tools etc.
I have yet to decide what to do with the bogies, whilst there is some provision for springing and compensation, its not exactly what I would choose for working models, so the idea of a sprung inner bogie is a possibility, added to which the ride is improved and this is very noticeable on coaching stock. For my intended use I would rather sacrifice brake detail for improved running, added to which highly detailed brake gear does tend to suffer handling damage when subjected to repeated packing.
 

marsa69

Western Thunderer
Answers will follow soon...... In the meantime, the fans are identical and all rotate on the same direction. The real problem is that the two at each end, each rotate at different speeds! Now I've not cracked that one yet.......

Looking forward to seeing this rake take shape Cynric!

How are the fans fed their power? In parallel or series? Could you not put a suitable resistor in to limit the current to one of them?
 

28ten

Guv'nor
10 minutes tinkering about with some inner bogie concepts. There are two possible options, with either inner or outer bearings, and both have pros and cons, outer bearings giving less friction, inner bearings make it easier to mount a bogie side from either an etch or casting. Springing will be from piano wire. I have a vague idea that these might interest other people building MK1's in 7mm.

bogie.JPG
 

Phill Dyson

Western Thunderer
I would be interested too, I like the idea of springing existing bogie's very much :)

Could I ask one stupid question:oops: , where do you obtain piano wire from ?.........& don't say pianos :D.

Is piano wire any different from guitar strings ?
 

28ten

Guv'nor
Unwound guitar strings :) My local model shop sells thicker gauges for r/c aircraft.
Inside bearings are going to be easier to adapt to different sides. Looking at what I have there will be a lot oh hacking and sanding with pinpoint bearings, but there is a long way to go yet.
 

28ten

Guv'nor
turning attention from the bogie to the truss, which is a fold up etch, ok so far, but it is fixed to the resin floor by glue and small tabs :eek:

IMG_0745.jpg

The solution is fairly simple, remove a couple of mm from the raised ribs and attach some section from eileen - but I havent got a mill..... however I do have a pillar drill, a 6mm end mil and a cunning plan. This is only resin so I shall set up some stops and do it freehand, pictures will follow after I have done the first one

IMG_0746.jpg

and finally there are these in some of the kits- whitemetal truss supports, they will meet Mr bin and be replaces with some angle.
IMG_0747.jpg


I knew all this would need doing, so its no shock, actually its unfair to say it needs to be done but for a more robust model then im happier to do the extra work, and in fairness I have employes similar dodges to easybuild using pcb.
 

28ten

Guv'nor
What do you guys find is the best sort of gauge of wire to use for 7mm springing ? :)
How long is a piece of string? :)) it depends on the distance between fulcrum points. generally the further apart the points the thicker the gauge of wire you will need for a given weight, you can get technical about deflection, frequency of response etc etc but being a bodger I just have a range of wires to suck it and see what works ;)
 

28ten

Guv'nor
Heres the basic idea:) the inside bearings have won me over, they are far more versatile for attaching different bogie sides. The bolster and sides will be one H shaped piece that folds up to make the assembly


concept.JPG
A standard 1/8 tophat bearing is soldered to the keeper, insert piano wire..... boing, boing ;)

detail.JPG

Brake gear can be attached to the outside of the frame via some tabs if so wished. Next step, order some 1/8 bearings, after which I will laser a prototype:) Secondary springing could be possible, but first thing is to get this working.
 

adrian

Flying Squad
The drawing seems to indicate two fulcrum points in the central bolster for the piano wire, is this correct? Just to throw another option into the melting pot. With this arrangement then the springing on the axles would be virtually independant, whereas if there was a single fulcrum in the bolster then there would be some form of compensation between the axles. Whether it's necessary or not, I suppose it depends on some extent on how you intend to fix the bolster to the under frame.
 

28ten

Guv'nor
Adrian you are quite correct, I had thought about making the hole in the bolster larger for clearance and using a single fulcrum in the center, the reason being I favour heavier wire and greater distance between the fulcrum points. I also find single wires are much easier to change and tune.
 

28ten

Guv'nor
I made a start on the crew. its very much work in progress, the secondmans shirt is ok but the drivers jacket needs a lot of work, and I may make the waistcoat a dark grey, and pick the watch chain and buttons out in brass, more work also is needed on the bulkhead. hopefully the figures give the impression of an older, ex steam driver and a younger second man
IMG_0748.jpg
 

28ten

Guv'nor
Hi Cynric,

Looks great:thumbs:. Who's figures have you used?

Rob
Omen on the left and Heroes of the footplate on the right


After a jaw dropping experience ordering some coach wheels - they were £5.50 last time I bought some :eek:
I got on with the some ideas for the fan, some very quick sketches
Replacement base to be lasered from mdf
fan1.JPG


From the underside, I plan to run a belt between the two, and drive will come from a motor either directly connected to a fan shaft or mounted to one side. Im assuming I should be ok using a 6v motor as long as a resistor is used to reduce the juice from the decoder?fanunder.JPG
 
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