Thomas brake

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David B
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Thomas brake

Postby David B » Mon Jan 19, 2015 2:08 pm

I am having a struggle interpreting the instructions for a GWR carriage truck (Scorpion), a D&S kit.

Does anyone know of a diagram, picture or good explanation of how the fittings fit the wagon? I have a shaft and handles, but there is a small geared link and another bracket, together with a 3mm shaft and I just cannot work out how they fit together.

Any help will be much appreciated. If anyone has made one of these and managed to get the brake together, could they post a photo, please?

Joe Newman
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Re: Thomas brake

Postby Joe Newman » Mon Jan 19, 2015 4:16 pm

David,

There is an illustrated example of the building of a 7mm Scorpion on Raymond Whalley's web site.

http://www.raymondwalley.com/carriages/ ... L0smk0qWUk

Hope this helps.

Joe

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David B
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Re: Thomas brake

Postby David B » Mon Jan 19, 2015 5:34 pm

Thank you for the pointer, Joe. Interesting to see and a help with other things.

Unfortunately, it is not the Thomas brake. In fact, though he says there are pictures of the finished model, I can't see a brake handle on it anywhere! All the pictures I have seen have the Dean Churchward handle and date from the 1940s & 50s. I am modelling an earlier period and although the Thomas brake was not long lived, I gather it was still there in the period I am doing.

Edit: I have just found the brake handle, a lever. I'll take Raymond's word for it but I have not seen any pictures with such a handle.

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Weskie
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Re: Thomas brake

Postby Weskie » Mon Jan 19, 2015 6:42 pm

David

I've sent you a 'pm' with some info. Hope it's useful.
Andy Westcott

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Dave K
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Re: Thomas brake

Postby Dave K » Tue Jan 20, 2015 1:32 pm

David B wrote:I am having a struggle interpreting the instructions for a GWR carriage truck (Scorpion), a D&S kit.

Does anyone know of a diagram, picture or good explanation of how the fittings fit the wagon? I have a shaft and handles, but there is a small geared link and another bracket, together with a 3mm shaft and I just cannot work out how they fit together.

Any help will be much appreciated. If anyone has made one of these and managed to get the brake together, could they post a photo, please?


David,

I've attached a couple of photos of the underside of my Scorpion. Like you I was having problems working out where all the bits went, bit fortunately when I was building mine Danny was still trading and attending shows so I was able to ask him how the brake bits when together.

IMG 0668.jpg
Underside of Scorpion. There was a full cross wire between the two handles until I fitted the AJ couplings.
IMG 0668.jpg (106.33 KiB) Viewed 5111 times


IMG 0679.jpg
Closeup of Thomas brake handle and ratchet.


Hope this helps :!: :!:

Dave

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David B
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Re: Thomas brake

Postby David B » Tue Jan 20, 2015 10:58 pm

Thank you, Dave. These are very helpful. Much appreciated.

DougN
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Re: Thomas brake

Postby DougN » Wed Jan 21, 2015 1:08 am

Dave, I like the way that you have set up the alex Jacksons... it is something I am trying to explore and get some rolling stock working. I think your method of a handrail knob and some copper clad glued to the floor removes one of the variables. :)
Doug
Still not doing enough modelling

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Dave K
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Re: Thomas brake

Postby Dave K » Wed Jan 21, 2015 1:07 pm

DougN wrote:Dave, I like the way that you have set up the alex Jacksons... it is something I am trying to explore and get some rolling stock working. I think your method of a handrail knob and some copper clad glued to the floor removes one of the variables. :)


Doug,

I usually prefer using a hinge plate to mount my AJ's but chose this method for the Scorpion as the model was already built when it was decided to change from 3 link etc. to AJ's

Dave

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David B
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Re: Thomas brake

Postby David B » Sat Jan 24, 2015 12:14 pm

Thank you for the help I have had from people, especially Mr Keeler (Dave K) who won a prize with his model at Scaleforum back in 2010. I think I have cracked the problem and come up with a credible solution.

First, an enlargement of the diagram in Tourret which, in my combined edition (1998) is on p53

Thomas-brake.jpg


The shaft (b) that is turned by the handle (at a) has a worm which engages with ' . . . a toothed bell-crank [coloured red] attached to the brake shafting.' In the kit, the toothed part is not cranked. I have coloured a short bracket in green. Again, although there is a bracket on the model, it does not hold the toothed bit anywhere near where the worm should be. I can only conclude that the kit is not quite accurate and missing a small bracket.

My solution:

crop_0365.jpg
crop_0365.jpg (43.55 KiB) Viewed 4845 times


This is a crop of the following picture and I have coloured the parts the same as on the diagram with the blue addition where the worm would be on the shaft. I have made use of the straight toothed part supplied with the kit and made a small extra bracket (green). This is then attached to a further crank (top, right of centre) which would normally be attached to the brake gear but in this case is not because the brake gear is attached to the rocking iron.

IMG_0365r.jpg


This is the completed brake gear. You might wonder how the wheels are going to be fitted. In the red circle, I have temporarily held the parts together with a twist of wire. I will pin this properly once the wagon is painted and the wheels fitted. The next job is to fit the J hangers.

This has been an interesting conundrum. It's not been a matter of rivet counting but trying to make something that replicates the original, be credible and would appear to work. It might not be absolutely accurate, almost certainly not, but I do think it is much nearer how the original was made.

Thank you very much to those who offered help, especially My K. I hope this will be useful to anyone else who tackles this kit because the instructions are difficult to interpret on this part.
Last edited by David B on Sun Jan 25, 2015 4:58 pm, edited 1 time in total.

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grovenor-2685
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Re: Thomas brake

Postby grovenor-2685 » Sat Jan 24, 2015 2:04 pm

Seems a little odd that the hand brake applies only one shoe when it could have been connected to the main linkage and apply the brakes that way, was that how they worked?

Also the linkage to the clasp brakes in your pic looks wrong, when the brakes are applied the outer yoke and shoes is pulled onto the wheel but the inner yoke and shoes move away from the wheel, the support from the wagon floor needs to be seperate from the equalising lever and pivotted to it.(And, of course pretrty much invisible when the wagon in use :) )

Sorry to be picky but you did say
trying to make something that replicates the original, be credible and would appear to work.

regards
Keith

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David B
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Re: Thomas brake

Postby David B » Sat Jan 24, 2015 2:21 pm

No, not picky but right. The thought had occurred to me as well, Keith, but I looked at the diagram that is in the instructions and could not get the bits to fit any other way.

instruction-diagram.jpg
instruction-diagram.jpg (62.06 KiB) Viewed 4816 times


I see another afternoon trying to resolve this. It's most probably me having missed something obvious.

It would seem from literature that the hand brake may be linked to the butterfly rather than the brake shoe. This is not clear. The Thomas brake was normally fitted at the end of a vehicle and the diagram in Tourret shows the toothed crank linked to another crank and short shaft in the middle of the vehicle. This then operates the handed brake blocks on that side as they are worked by any other system.

The difference here is that the brake handle and shaft are already in the middle of the vehicle. I have then worked from Dave Keeler's explanation which he in turn got from Danny Pinnock.
Last edited by David B on Sun Jan 25, 2015 4:58 pm, edited 1 time in total.

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grovenor-2685
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Re: Thomas brake

Postby grovenor-2685 » Sat Jan 24, 2015 2:55 pm

It certainly appears on that diagram that the handbrake pushes directly on the brake shoe, either just the one or one each side.
The diagram has the equalising lever supports missing, so you had to make those up, the kit parts presumably relied on them being in an invisible place.
I am also puzzled by the right hand pull rod, the bend/joint at 35 makes no sense as the rod would just straighten up when tension applied, or it needs supporting from the frame with a robust (as in compression) link.
Side views are never really enough are they!
regards
Keith

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David B
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Re: Thomas brake

Postby David B » Sat Jan 24, 2015 3:15 pm

The equalising lever supports have been incorporated in to the levers, as you can see from my photo above. I think you are right and one has to consider them a representation and not readily visible once the kit has been made and the under fame painted mucky dark.

As for the pull rod with the bend, I agree, but that's what I have in the kit! I wonder if there was yet another support of some kind that has not been put in to the model. I can understand the reason, to clear the butterfly, but it does seem incongruous here as it is.

I have decided not to pursue the kit this afternoon. I will do something else, shorter, and come back to it tomorrow.

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grovenor-2685
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Re: Thomas brake

Postby grovenor-2685 » Sat Jan 24, 2015 3:55 pm

As for the pull rod with the bend, I agree, but that's what I have in the kit! I wonder if there was yet another support of some kind that has not been put in to the model. I can understand the reason, to clear the butterfly, but it does seem incongruous here as it is.
I agree there would have to be a support for it to work, similar to the supports for the equalising levers, ie pinned to that joint and pinned to something at the top.
Regards
Keith

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Will L
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Re: Thomas brake

Postby Will L » Sat Jan 24, 2015 6:52 pm

Have to say that while the single V hanger makes some sort of sense when paired with the external brake lever, used to supporting one end only of a relatively long cross shaft with the Thomas brake looks a bit unlikely? What chances the V hanger was only part of the lever brake and the Thomas brake did operate centrally on the full brake linkage?

essdee
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Re: Thomas brake

Postby essdee » Sat Jan 24, 2015 7:04 pm

Now - is that a working vacuum cylinder David....?

However it ultimately fits together, that is superlatively neat work, sir.

Awed,

BW

Steve

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David B
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Re: Thomas brake

Postby David B » Sat Jan 24, 2015 8:15 pm

Will L wrote:Have to say that while the single V hanger makes some sort of sense when paired with the external brake lever, used to supporting one end only of a relatively long cross shaft with the Thomas brake looks a bit unlikely? What chances the V hanger was only part of the lever brake and the Thomas brake did operate centrally on the full brake linkage?


I think, Will, that if the job were done 'properly', the shaft off the single V hanger might be much shorter with the mechanism much closer to the solebar. It does look rather long here. It seems from Mr Keeler's discussions with Danny Pinnock that the V hanger was part of the system, without the long brake handle.

essdee wrote:Now - is that a working vacuum cylinder David....?

However it ultimately fits together, that is superlatively neat work, sir.


The working vacuum cylinder I am keeping for Missenden! It has been a long-cherished dream of Mr Langdon's do build working brakes.

Thank you for your kind comment on my work, Steve. I aim to please.
Last edited by David B on Sun Jan 25, 2015 4:59 pm, edited 1 time in total.

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grovenor-2685
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Re: Thomas brake

Postby grovenor-2685 » Sat Jan 24, 2015 8:50 pm

What chances the V hanger was only part of the lever brake and the Thomas brake did operate centrally on the full brake linkage?

The diagram does show a pull rod from the Thomas brake to the lever that uses that brake hanger, but what might be the origin of the diagram?
Probably all lost in history now unless there is a preserved one hiding somewhere.
Keith

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Flymo748
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Re: Thomas brake

Postby Flymo748 » Sat Jan 24, 2015 10:02 pm

grovenor-2685 wrote:The diagram does show a pull rod from the Thomas brake to the lever that uses that brake hanger, but what might be the origin of the diagram?
Probably all lost in history now unless there is a preserved one hiding somewhere.
Keith


One thing that did go through my mind was whether it was a patented system. Therefore there may be diagrams buried deep in the archives of the best British bureaucracy...

I have no idea where to start looking for these things, although given the breadth of knowledge on this Forum, I'd be confident that someone does.

Cheers
Flymo
Beware of Trains - occasional modelling in progress!
www.5522models.co.uk

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David B
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Re: Thomas brake

Postby David B » Sat Jan 24, 2015 11:04 pm

It was patented.

dal-t
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Re: Thomas brake

Postby dal-t » Sun Jan 25, 2015 9:49 am

Flymo748 wrote:One thing that did go through my mind was whether it was a patented system. Therefore there may be diagrams buried deep in the archives of the best British bureaucracy...


According to The National Archive, patents after October 1852 'generally do not survive'! That doesn't mean there aren't diagrams, but they will be pretty hard to find. The Archive normally expects you to know both the Patent holders name and the Patent Number to search for those they do have. Without wishing to totally swamp this idea with cold water, in my (much more recent than 1852, but still somewhat dated) experience, patent drawings are also limited to the particular aspect being patented, without setting that in any wider context of non-patented elements, and at least to this non-technical reader they can be extremely difficult to interpret (which does rather beg the question why I was sent to do that particular piece of research ...).
David L-T

billbedford
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Re: Thomas brake

Postby billbedford » Sun Jan 25, 2015 10:14 am

The place to search for patents is espacenet.com.
Bill Bedford
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