Sir Sagramore, 3.5” gauge Maunsell King Arthur

[CF MRC]

The revised brake wheel drive modifications came early for Sir Sagramore as I remembered that there was an old dental hand piece in the big workshop.  After a bit of dismemberment it looked very promising:

The original brake column was modified to take the hand piece head. 

The vertical brake shaft needed splicing onto the hand piece drive, (not a trivial exercise) and the brake handle shaft re-engineered to mimic a dental bur, with a ‘latch grip’ drive. The original box, made by Ian Jaycroft, was significantly re-modelled to be closer to prototype. 

The mechanism works well, as the original alignment of the contrate gears is maintained. 

The prototype has a rounded top to the brake column and this now correct on the model. 
The video probably shows the quite complex arrangements better than photos. 

The whole assembly is held together with 10 bolts. 

The support column should be square / rectangular in section, so that can be modified quite easily with some brass channel section. 
The improvement in the view from the tender I think makes all the work worthwhile. 

 

Tim
 

[CF MRC]

Just looking on ebay I found these for anyone interested. 
www.ebay.co.uk/itm/203680871226?_trkparms=amclksrc%3DITM%26aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D20221018081743%26meid%3D1e7a64362abd46ccbccc05155fcd288c%26pid%3D101429%26rk%3D5%26rkt%3D12%26sd%3D272894791506%26itm%3D203680871226%26pmt%3D1%26noa%3D0%26pg%3D2332490%26algv%3DSimplAMLv9PairwiseUnbiasedWebCpr08MlcBERTGreedyV3KnnRecallV1%26brand%3DSKYSEA&_trksid=p2332490.c101429.m2460&amdata=cksum%3A2036808712261e7a64362abd46ccbccc05155fcd288c%7Cenc%3AAQAHAAABIFVAfz4vmJboe8N%252FfRYfRpkGnGuVpKoiKJ1XR%252FPBbEk2IyDS9eHJSGUt14M5EGunOBPNQImpe2ExIwtTF9FZzcfPHYA1ybIYWNhPJ%252B8EnUQNR435oQWLE%252FfbYE47Tsu0QhueXMsrxQ8YqnfSlzb%252BmFV7semTN8HoqAZJIiJ2ZpaucQ%252BOzd3CA2LBvUpC2z6xWLLC2pbzm7OAHxPk6xfUGi36lDF4hBlL4yvORFf9Uo6K%252BVF0smU1nQwfKEn5rWwcs89r99OagfKAX3hAO%252Bz2ufrU65QS255gXgBe6VRi55MMQlq90PiN0nhSc3X4OKnOJK8CHTNxV17vFMElsGOK9KDq%252B3IEvVRZxi%252FtwQuhsWBCNOq0HgkFkPf9VnxeirVwyw%253D%253D%7Campid%3APL_CLK%7Cclp%3A2332490
Effectively a Chinese copy of a Japanese copy of an original German design. 

Tim

[CF MRC]

After a fairly heavy couple of months making 2mm scale tube railways I thought a change of size was needed.  Some remedial work was needed on the cab side sheets following a mishap. 

Sir Sagramore has now been dismantled to fit the ashpan and grate.

There has been a huge amount of head scratching to work out how it all dismantles and fits.  Obviously, the boiler came off, but so also did the smokebox, steam pipes, mechanical oiler and reversing linkage.

The ashpan is complicated by straddling the back axle

It is also complicated by having two dampers and a bottom emptying flap on the model.

Once in situ  everything gets very crowded, in this view the dampers and flap are closed. 

Here we see the bottom flap and front damper open. 

The bottom flap will be good for emptying ash and manoeuvring the grate into the firebox - for sure it will need a special tool made for the job. The front and rear dampers will also need robust linkages to work well. These will need to be threaded in to the space behind the wheels, brakes and axle driven mechanical pump plumbing. That is not too difficult, the challenge is how to bring the control linkage into the cab and also make it dismount-able for servicing and repairs.
 

Oh well, at least it gives the little grey cells something to think about…

Tim

 

Edited January 10 by CF MRC

[CF MRC]

I have now worked out the mechanism to work the bottom ashpan flap. Ian Jaycocks very cleverly used a nut-bolt fixing onto the rear brake to act as a fulcrum for the first operating crank.

It was much easier working on Sir Sagramore with the brakes removed and this also simplified plumbing alterations.

The mechanism will need a connection in the cab but I think I have a solution for that. It also gives me a steer for the damper linkages. 

Tim

Edited January 20 by CF MRC

[CF MRC]

After an inordinate amount of thinking and puzzling I have now made the front and rear damper linkages for Sir Sagramore.

The rear linkage is simply a rod that links to the damper clevis and snuggles in close to the back head.

The rod is located by a grooved bobbin that centralises it with low friction.  The top is rebated and has a separate top hat 12BA bolt assembly.

This rod has a rotating handle that locks it open by resting on the frames (a detent will be filed in when the boiler is next removed). To rest the concept, a lump of styrene was carved to shape. 

This was then converted to metal and can be seen here with the handle in closed position. It will be prevented from moving medially by the support component of the front damper.

The pillar that supports the front damper lever has a rebate to locate the rear damper body when in the closed position. 

In this image, the dampers and drain cocks are in the open position; the brass nut will be replaced with steel.

I have tried to maintain the style of Ian Jaycocks’ work with these new components. 
 

Tim

 

 

Edited January 24 by CF MRC

[tigerburnie]

Excellent work, the reference to the 12 BA bolt gives me a reference as to the size of things, not sure my dexterity is up to such fine work these days.

[CF MRC]

The central trap door on the Sir Sagramore ashpan now has a control / locking device. It’s a bit unorthodox but it will hold the trap door shut when running.

The linkages ended up with a rod pointing backwards at 45deg from the base of the footplate, with it pulled up to close the trap door. I therefore made a steel toggle that holds the rod in the open position:

It rotates 90deg. and pushes in towards the backhead to open the trap door for ash disposal:

I wasn’t convinced by the appearance of the toggle and it was also a bit slippery to handle. I therefore made a hand wheel to make it easier to hold and also reduced the locking pillar in size.  The wheel was turned as a blank and mounted on a mandrel, Loctited in place. This was then drilled on the rotary table. 

The outer ring was then turned off to give the ‘grippy’ outer part of the hand wheel. 

After rounding off the edges the front face was given a rebate using a graver. 

The locking toggle components can be seen here, before assembly.  The hand wheel was simply soft soldered onto the steel toggle, and held in place with a 10BA nut, with it pivoting freely on the rod - a piece of coat hanger suitably turned down & threaded.

Finally an exciting video showing it in action!

Back to small scale stuff now. 
 

Tim