Festiniog Railway Cleminson 6 wheel coal wagon

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Trevor Thompson
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Re: Festiniog Railway Cleminson 6 wheel coal wagon

Post by Trevor Thompson » Wed Feb 01, 2023 10:07 am

Yes I suspect that you may have a point in as much as when I have added too much pigment then the resin is too light resistant for it to work. However I did an exposure test on the black pigmented resin when it had been diluted and found that it hadn't affected the exposure time at all. So I think the answer is actually no - it didn't need longer exposure times.

Philip had an interesting point about the pigment settling in the tank, and I have been raising and lowering the plate to mix it quite a few times before setting it off to make sure that this isn't a factor.

I think part of the issues is to do with the type of resins in use. I am not saying anything negative about the clear resin (with or without pigment added) it is working properly for me. However the "tough" resin which costs twice as much certainly performs better. Whether its is twice as good is something I haven't worked out! The supports SEEM to part during printing more with the standard resin - but that is just a gut feeling and may be more to do with using black pigment.

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philipy
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Re: Festiniog Railway Cleminson 6 wheel coal wagon

Post by philipy » Wed Feb 01, 2023 11:13 am

Trevor Thompson wrote: Wed Feb 01, 2023 10:07 am The supports SEEM to part during printing more with the standard resin - but that is just a gut feeling and may be more to do with using black pigment.
Hmmm... my gut feeling has been that supports part more easily using the tough resins although I'm not using the same supplier as you, which is of course another factor to take into consideration when doing comparisons. I've had a feeling that the tough resins are more viscous than standard types, irrespective of colour, and create more drag which allows the supports to give way. It may be that that could be overcome by playing with exposure times, speed, etc, not to mention the support parameters, but that would all take a lot of work and would only be worth it, IMO, if I was wanting to standardise on one specific resin for everything.

Going back to my point about the black pigment settling out, I only noticed it when I inadvertantly left a few mm of resin in the machine for a several weeks over the Christmas period. When I realised and went to clean it out, I noticed a whole load of tiny black specs sitting in the bottom of the vat and the 'black' liquid above it was much more translucent than opaque as it should be.

I think when I've worked through ( and chucked failures) the various coloured resins I've got in stock, I'm going to standardise on translucent green which seems to be much more reliebale that denser, coloured, resins.
Philip

Trevor Thompson
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Re: Festiniog Railway Cleminson 6 wheel coal wagon

Post by Trevor Thompson » Thu Feb 02, 2023 7:53 pm

I now have the "bogies" printed. The pivots for the outer bogies are also bonded in place. I used 2mm diameter balls on the outer bogies and 2.5mm balls on the central bogie. The pivot bolts for the outer bogies are 8BA, bought bolts worked, but I made up some special ones on the lathe. A short length of 3mm diameter rod formed the connection pin mounted on each end the centre bogie. The bottom of the wagon with the balls in place:
IMG_2727.JPG
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The 2mm balls are very easy to loose!

I found the correct position for gluing the pivot blocks by assembling the bogie to the pivot, with bearings in place and gluing them into place on full lock, ensuring that the angle ends were even on both sides.

The bogies secured in position:
IMG_2729.JPG
IMG_2729.JPG (1.56 MiB) Viewed 3013 times
I have started to make the axles up. I don't think that the resin printed wheels are going to work. The axle is 3mm diameter. I mounted a wheel in the lathe and bored the hole 3mm. When I pressed the wheel on to the axle the hub of the wheel split. That also happened with a second wheel. There has to be some interference fit - or the wheels have to be glued on - and I was expecting to have to glue these. So I will print the wheels on the filament printer tomorrow - I know they will work.

The bogies seem to fit neatly, and the outer ones seem to hold the middle one down sufficiently to prevent balls from escaping when the wagon is turned over. They all move freely as I intended. I am making the axles so that there is little sideplay in the axleboxes. Any sideplay, particularly in the centre axle will prevent the centre bogie moving sideways as intended.

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Trevor Thompson
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Re: Festiniog Railway Cleminson 6 wheel coal wagon

Post by Trevor Thompson » Wed Feb 15, 2023 2:11 pm

A bit of a change of direction on the wheels. I found some stainless rod which was 2.98mm diameter, and which I could make fit into 3mm reamed holes in the resin printed wheels. So back to resin printed wheels. The axles were turned down for the bearings:
IMG_2769.JPG
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That is the 3mm OD, 1mm ID bearings which I have been using on my slate wagons, fitted onto the end of the axle. Of course I had to fix the wheels onto the axle using superglue.

Some gentle easing with a file was required to get the axle boxes to move freely in the W irons. The axle fitted and held in place by these "keepers" which are superglued to the ends of the w irons:
IMG_2771.JPG
IMG_2771.JPG (1.74 MiB) Viewed 2902 times
The paper is there to keep the superglue away from the axle boxes. It has a strong tendency to glue the axle boxes into place - and of course I want them to move freely under the influence of that spring which you might just be able to make out in the next photo.The holes in the end of the "keepers" are for 1mm diameter rod which supports the bottom of the w irons - as per the prototype.

The finished wagon on its wheels, and with magnetic couplings fitted. It seems to run on the test track OK - but I think it will need the weight of a load of coal to keep it on the track:
IMG_2773.JPG
IMG_2773.JPG (1.77 MiB) Viewed 2902 times
It just needs some final painting and it's ready to add to the goods wagon fleet.

I will sort out the STL files and add them to the 3D files section shortly.

Trevor

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Peter Butler
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Re: Festiniog Railway Cleminson 6 wheel coal wagon

Post by Peter Butler » Wed Feb 15, 2023 4:46 pm

Looks superb Trevor. As long as a little additional weight keeps it on the track you have winner!
The best things in life are free.... so why am I doing this?

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philipy
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Re: Festiniog Railway Cleminson 6 wheel coal wagon

Post by philipy » Wed Feb 15, 2023 6:19 pm

Very nice Trevor.
Philip

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