Donegal Railway Class 5 Drumboe 15mm scratch build

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Re: Donegal Railway Class 5 Drumboe 15mm scratch build

Post by tom_tom_go » Sat Apr 25, 2020 3:20 pm

Amazing accuracy here being modelled of the prototype.

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Re: Donegal Railway Class 5 Drumboe 15mm scratch build

Post by SeamusOD » Sat Apr 25, 2020 7:41 pm

Thanks drawing it in autocad from measurements taken from fullsize makes all the difference, I have found a few measurements that autocad basically says that is not correct, and then when I go next time to the foyle museum to check on meenglas I realised I wrote it down wrong or measured it wrong and autocad was right !

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Re: Donegal Railway Class 5 Drumboe 15mm scratch build

Post by SeamusOD » Sun Apr 26, 2020 6:29 pm

Eccentric crank, rod, and expansion link next, the eccentric crank is located on a flat on the crankpin to keep it in correct "timing" position I just glued it, once all the lengths were correct everything moves ok, no binding.
Will probably redo the expansion link as not the correct shape, but now I have the hole spacings correct easy to change.
As you can see I dont have the link running in the slot have a fixed hole at the top, and the missing upper half as such of link wont be noticed once I add the dummy radius/valve rod.
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Re: Donegal Railway Class 5 Drumboe 15mm scratch build

Post by SeamusOD » Mon Apr 27, 2020 8:15 pm

Final bit of my linkage/drive gear is the crosshead link and combination lever, they were easy enough one I figures out making a dummy radius/valve rod, its fixed but hornby does the same so thats good enough for me :)
Have done a short video of the whole thing working, I will see where I can upload it to and post link
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Re: Donegal Railway Class 5 Drumboe 15mm scratch build

Post by SeamusOD » Tue Apr 28, 2020 8:04 pm

Youtube link to the drivegear moving, hope it looks realistic, being turned by hand so bit stepy but its very free, no binding, have a plan to add some gearing to centre drive axle so I can power it for display purposes
https://youtu.be/WUoJY-J9CyE

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Re: Donegal Railway Class 5 Drumboe 15mm scratch build

Post by tom_tom_go » Tue Apr 28, 2020 8:50 pm

Brilliant!

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Re: Donegal Railway Class 5 Drumboe 15mm scratch build

Post by SeamusOD » Sat May 02, 2020 1:31 pm

been 3D printing some bits, initially wanted it to be just wood as all the laser cut models I have done in the past are all wood apart from maybe a perspex windscreen say on a model car, but realized some 3D printed bits would be more practical and look better especially for steam dome and chimney, which I have already done as can be seen from my early picture of the initial mock up.

Tanks caps & steam valve
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The Steam valve
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The one above is on the "cosmetically" restored meenglas but from columkille inside museum and other pictures I have seen the base seems to have been red not black so I will print another one later, also want to add bit more detail to it around bottom nuts etc.
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Also printed another steam dome and sanded it then painted it red, took about 5 coats after the plastic primer but looks well.
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Re: Donegal Railway Class 5 Drumboe 15mm scratch build

Post by philipy » Sat May 02, 2020 1:56 pm

That red dome certainly does look well, lovely job.
Philip

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Re: Donegal Railway Class 5 Drumboe 15mm scratch build

Post by SeamusOD » Sun May 03, 2020 6:42 pm

Some details for inside cab, regulator, reversing lever and brake are the obvious ones for now
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Discovered differences on reversing lever on meenglas and columbkille in regard to locking lever, no idea yet which drumboe had so I done both plus one for my painted version.
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Brake is easy enough just bit 2mm dowel, same as used for hand rails each side of door.
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Re: Donegal Railway Class 5 Drumboe 15mm scratch build

Post by ge_rik » Sun May 03, 2020 7:06 pm

Fascinating build. It's amazing how much detail can be achieved with laser cutting.

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Re: Donegal Railway Class 5 Drumboe 15mm scratch build

Post by SeamusOD » Mon May 04, 2020 1:08 pm

ge_rik wrote: Sun May 03, 2020 7:06 pm Fascinating build. It's amazing how much detail can be achieved with laser cutting.

RIk
If I was just starting today I dont think I could do it as latest versions of drawing programs like autocad are just way too complicated, I use a old autocad 2000 version which is very easy to use and ideal for 2D drawings like this, the latest versions hurt my head :( and I would like to think that I can use autocad fairly well but like all software they keep changing and moving and renaming things, drives me mad !!
I update nothing if it works I leave it alone :)

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Re: Donegal Railway Class 5 Drumboe 15mm scratch build

Post by SeamusOD » Mon May 04, 2020 3:51 pm

Have already laser cut some straight sections of track just for display purposes and want to do some curves just to see what would be minimum needed for an engine of this size, as its approx 395mm between centres of front and rear axles, and with 3 flanged main wheels, it wont be going round a R1 or 2 curve too easily.

What would be the norm minimum radius on 45mm track for the larger engines and I suppose gauge 1 is the most common run on 45mm

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Re: Donegal Railway Class 5 Drumboe 15mm scratch build

Post by GTB » Tue May 05, 2020 9:40 am

SeamusOD wrote: Mon May 04, 2020 3:51 pm What would be the norm minimum radius on 45mm track for the larger engines and I suppose gauge 1 is the most common run on 45mm
Outside the UK, 45mm is the common garden scale gauge, so it's not just used for G1. LGB would be more common and it is also used in a range of scales for various narrow gauges.

I model an Aust. 3' gauge railway in Fn3 scale, ie. 15mm/ft (1:20.3) on 45mm gauge.

My garden track has a minimum radius of 7’6”, but not everyone has that much space, so I design for a minimum radius of 4’ so I can run on other tracks. I have a couple of pieces of LGB R3 curved track that I use to form an s-bend for checking chassis while building.

That said, my big locos are either 2-6-2 tender locos, or articulated. It's usually easier to get a loco with 2 wheel trucks and outside cylinders around 4’ radius, than it would be to get a 4-6-4 around that sort of radius, as a 4 wheel leading bogie can run into clearance problems around outside cylinders in 45mm gauge.

Regards,
Graeme

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Re: Donegal Railway Class 5 Drumboe 15mm scratch build

Post by SeamusOD » Tue May 05, 2020 12:23 pm

Thanks Graeme for reply, I dont have any lgb R3 curves so going to make some sections up today to test it, noticed that PIKO brand which I have some streight sections their R5 is the equivalent just track widths larger in dia. at 1243mm
You mentioned front bogie clearance, that was one thing I noticed when making the front bogie/pony truck that it didnt have much movement side to side before it would hit chassis side plates and cylinder and had to go back to the prototype to check it was the same.
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Re: Donegal Railway Class 5 Drumboe 15mm scratch build

Post by SeamusOD » Thu May 07, 2020 6:16 pm

Made up some of my own lasercut LGB R3 curves to test and apart from problems with rear bogie which I will mention shortly the front pony truck is limited by cylinders, but it does just fit PIKO R5 which is bit larger in diameter at 2486mm, so this looks like the minimum radius track without doing "non scale mods".

But discovered I made a design flaw on rear bogie, :error: I just have it swiveling in the middle which obviously dosnt work for going around curves, as initially this was just going to be a static model and it didnt really matter, now that I put so much time into getting all the linkages etc working, I would like to get as much of it right as possible.

I did see the springs each side on the bogie in prototype picture below, but didnt really look to see why, as never studied it much but now I realise the whole bogie could move side to side which make sense :oops:
So doing a redesign of my rear bogie tonight !
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Re: Donegal Railway Class 5 Drumboe 15mm scratch build

Post by SeamusOD » Sun May 10, 2020 1:08 pm

New design of rear bogie, basically done as the prototype the bogie rotates in the ring on the centre plate which also can move side to side, there is about 3mm movement each way with the stops in present position but on next one I will move them out another 1mm. The cross shaped support pillar will be fixed to chassis, bogie pivots on the 6mm dowel.
It tracks well on curves now, minimum at the moment is PIKO R5 at 1243r will need some mods to front pony truck to get it navigate a LGB R3 might look at that at later stage.
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Leonard seems happy with the modifications
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Re: Donegal Railway Class 5 Drumboe 15mm scratch build

Post by SeamusOD » Mon May 11, 2020 1:34 pm

Found this picture through the many shots I have taken of Meenglas, it shows the middle of the pony truck, it appears that the front may of had a similar side to side movement as the rear as there appears also to be stops, but I cant see how its possible as the frame and arm from the swivel point are all welded together, and space from the wheels to the inside of frame is only 50mm from my notes, plus I know from my model the inverted top hat cross member you see in photo also limits movement as wheels come in contact with it.

Can anyone shed any light on something done similar on other prototypes, will need to go and look again at meenglas once the lockdown measures allow.
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Re: Donegal Railway Class 5 Drumboe 15mm scratch build

Post by GTB » Mon May 11, 2020 2:31 pm

SeamusOD wrote: Mon May 11, 2020 1:34 pm Can anyone shed any light on something done similar on other prototypes, will need to go and look again at meenglas once the lockdown measures allow.
I can't see any evidence of swing links in the photos, so if we assume the front truck is complete (not always a safe assumption on preserved locos.), that would suggest it is a Bissell truck. That design used inclined surfaces in the form of an inverted V to centre the truck and provide some side control. There may be a drawing of the arrangement somewhere on the net.

The side play allowed would depend on the minimum track radius used by the CDJR.

On working models which have to run on smaller than scale radius curves, more side play will be needed and may require compromises like more clearance in frame openings, etc., etc.

Regards,
Graeme

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Re: Donegal Railway Class 5 Drumboe 15mm scratch build

Post by SeamusOD » Mon May 11, 2020 8:41 pm

Thanks Graeme I have looked up some info on the Bissell truck it mentions that apart from swinging radially some rotate on the vertical axes but I cant see how that is possible in this case, unless the axle framework is separate to the main frame but from my sketches and measurements plus the rivets you can see on the front frame in picture above its not. I really need to go a have a look again has me confused.
Below is another picture showing rear of pony truck and radial arm if that is correct term.
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My version of the pony truck
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Re: Donegal Railway Class 5 Drumboe 15mm scratch build

Post by GTB » Tue May 12, 2020 3:36 am

SeamusOD wrote: Mon May 11, 2020 8:41 pm I have looked up some info on the Bissell truck it mentions that apart from swinging radially some rotate on the vertical axes but I cant see how that is possible in this case, unless the axle framework is separate to the main frame but from my sketches and measurements plus the rivets you can see on the front frame in picture above its not. I really need to go a have a look again has me confused.
The Bissell truck/bogie was an early design, which came in 2 wheel trucks and 4 wheel bogies. Both types had the radial arm, but the 4 wheel ones had a centre pin as well, so the wheel frame could swivel, as well as bodily move from side to side, with the side control on both types coming from the inclined surfaces. The 4 wheel Bissell bogie is easily recognised, it has a very short wheelbase compared to later designs.

Regards,
Graeme

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