Comet Gresley 8'3" bogies

davebradwell
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Re: Comet Gresley 8'3" bogies

Postby davebradwell » Fri Dec 02, 2022 8:56 pm

David, I think you're confusing cantrail with cornice. The cantrail is a heavy internal member 4in high and seen in Bill's sections and dotted in my part sideview. The cornice is the tatty little bit of strip stuck on the outside which is 2 1/2 in ono X.1/2in. You'll see the cantrail runs from below the cornice to above it.

The drgs I'm looking at give height to bottom of cornice as 6ft 3 1/2in or 25.17mm for the correct height of your Comet side - 0.66 short or a couple of inches in real money. Some sort of stepped floor, perhaps, with a protruding edge that could be profiled or just live with it and set body a little high on its bogies. Alternatively you might perhaps make the cornice a little wider to regain part of the height - 1.3 instead of 0.75 almost gets you there!

Your side turnunder looks a bit severe at the moment. If you place straightedge across the flat bit where the windows would be, then the deflection of the bottom edge should be 4in. This corresponds to 3in turnunder from vertical because the upper sides slope inwards. I suspect it should start higher up the sides, too - about 10mm from bottom which would be just below the windows in a coach.

DaveB

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barhamd
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Re: Comet Gresley 8'3" bogies

Postby barhamd » Sat Dec 03, 2022 12:33 pm

Right, so looking at the first drawing Bill posted you have the roof profile and a chunky cant rail. On the second drawing you can see how the side was let into the cant rail and the join covered by the external cornice.

So I think I'll be 'near enough' if I draw a roof profile down to the bottom of the cant rail, include a small rib on the edge to represent the cornice and then butt the Comet side up against it. I think that will result in a coach which is about .5mm too short but I doubt anyone can notice that from layout view distance - perhaps it just had a lot of heavy parcels in it.

thanks
David

BorderCounties
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Re: Comet Gresley 8'3" bogies

Postby BorderCounties » Sat Dec 03, 2022 4:33 pm

Following on from Bryan Johnson's comments about the Comet roof profile on page 1 of this thread, it hasn't been mentioned that the end profiles and, therefore, the turn-under profile of nearly all the coach sides in the range (exceptions are BR Mk1 and Bulleid SR stock) are also a compromise between GW and LMS if not pure LMS. Therefore, the kits as supplied have matching profiles of ends, roof and sides and they go together - full stop.

Therefore, if you want the correct roof profile, you have to use an alternative - MJT LNER roof is the best place to start. But the ends don't now fit, and the sides and ends are too fat at the waist. There isn't much, if anything, available for a Thompson corridor coach end - I have used the casting that was available from 247 Developments - part number C566. This has the correct coach side profile so you will have to carefully reroll your sides to match. It might be worth contacting Brian Mosby to see if he still has that range of parts. If the castings were part of the ranges supplied by Errol Surman, these are supposed to be going to Squires empire in the near future.

Another alternative is the Bachmann D344 if you can pick up a cheap body shell. But again, there are problems with the roof profile - Tony Wright butchered a Bachmann coach for the Autumn 2020 virtual Missenden Abbey (https://www.missendenrailwaymodellers.org.uk/index.php/virtual-missenden-thompson-introduction/).

This probably hasn't really helped at all - we are sometimes at the mercy of what comes our way and striving to "Getting it all right" can become the "Art of Compromise" so we actually finish something rather than putting it back in the cupboard or worse.

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barhamd
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Re: Comet Gresley 8'3" bogies

Postby barhamd » Sat Dec 03, 2022 11:33 pm

Ok folks, be gentle with me....

I had a go at joining the Comet sides to the ends, I slightly tapered the sides in towards the top as the originals were vertical. I 3D printed a new roof in two parts. The resulting pieces are at the limit of what my printer can cope with and there was a little warping. I think I'll probably reprint in 3 pieces and add some more support next time probably including some more longitudinal spreader pieces in the CAD rather than just rely on Chitubox's support.

Comparing the roof profiles between the Comet extrusion and the 3D print. (this is the middle of the coach rather than the end which I printed as thinned down to .8mm

roof-profile3.jpg


Putting the roof on the sides and the sides on the chassis and it looks like this. Obviously we don't have the angled ends

aIMG_9945.jpg


I included holes for the ventilators in the print and also a bead for the gutter. I also tried to add the destination board supports.

aIMG_9946.jpg


Given the ridge along the bottom of the Comet extrusion trying to fit this and glazing with the windows would be really tricky. I think I might make the recess in the roof include space for the glazing so that I can fit the glazing up to the height of the etched side.

I've parked the coach next to a rewheeled Hornby Thompson, not because I think that the Hornby one is correct but just to see if it jars too much.

aIMG_9947.jpg


Waits with baited breath.

David
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barhamd
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Re: Comet Gresley 8'3" bogies

Postby barhamd » Sun Dec 11, 2022 2:42 pm

As no one screamed I'd got it all wrong I kept going..

I've reprinted the roof with better support and so the warping at the ends was much better. The two halves join much more smoothly and the ends will seat properly now. I've stuck some stretchers on the underside of the roof and between the sides in three places, the ones on the roof have a nut soldered onto them so I can fasten the roof to the sides in a removable way.

aIMG_9962.jpg


Because the roof profile has changed the whitemetal ends were no longer a fit to the roof. I opted to 3D print the ends to fit the roof and decided while I was at it to add the corridor connections to the end. The kit came with an etched corridor connection end which I think I will attach to the 3D print. The difficulty with this part is that the ends taper to nothing which makes printing hard in if you are trying to print them flat. I should have been more patient and printed them standing up but I think that would have taken the print time from ~1.5hr to neared 5hrs. I stuck the 3D printed ends to the brass ends and the roof profile join looks ok. The roof still needs something to tie the very ends down but the gap closes up completely.

aIMG_9961.jpg


I've printed some torpedo vents based on the drawings published on Western Thunder by Mike Trice and scavenged some T handles from an old project. I think the next step is probably the buffer beams and buffers. I suspect I can improve on the lumps of white metal but we'll see.

David
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barhamd
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Progress on a Comet Thompson Full Brake

Postby barhamd » Wed Dec 21, 2022 10:09 pm

Thanks to the help on this forum I've made some good progress on the Thompson coach. Having got the ends on and added the buffer beams I started with the detailing of the sides. I found some T handles from an old project and had fun yesterday cutting and fitting 36 1mm lengths of brass for the door hinges.

I need to do a little more tidying up on the roof but I don't think I'm too far off a coat of primer.
aIMG_0021.jpg

aIMG_0022.jpg

aIMG_0023.jpg


I was quite pleased with the torpedo vents, the drawings on the Western Thunder Gresley coach thread were extremely useful.
aIMG_0025.jpg


David
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