Jynn: a 7 1/4" gauge wren

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Nomis
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Re: Jynn: a 7 1/4" gauge wren

Post by Nomis » Mon Jul 13, 2020 5:50 pm

I don't have any pictures of the rest of the build (but can answer questions if anyone has any).

A few pics of Jynn's first weekend in steam:

ImageDSC_0118 by simon mace, on Flickr

ImageDSC_0122 by simon mace, on Flickr

ImageDSC_0121 by simon mace, on Flickr

ImageDSC_0129 by simon mace, on Flickr
Last edited by Nomis on Mon Jul 13, 2020 6:21 pm, edited 1 time in total.

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Re: Jynn: a 7 1/4" gauge wren

Post by Nomis » Mon Jul 13, 2020 5:52 pm

And back home after initial breaking in:

ImageDSC_0119_1572243224484 by simon mace, on Flickr

ImageDSC_0123 by simon mace, on Flickr

ImageDSC_0122_1572243224052 by simon mace, on Flickr

Nomis
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Re: Jynn: a 7 1/4" gauge wren

Post by Nomis » Mon Jul 13, 2020 5:55 pm

Despite being a (relatively) small engine, Jynn is still quite a heavy object to move around, so I built a simple trolley to make things easier:

ImageDSC_0174_1582404742027 by simon mace, on Flickr

In full flight in the garden:

Image2020-02-23_09-14-11 by simon mace, on Flickr

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Re: Jynn: a 7 1/4" gauge wren

Post by Nomis » Mon Jul 13, 2020 6:07 pm

There have been some (minor) teething issues, but nothing I wouldn't expect from a new engine:

- getting the suspension & valve timing to work together. With hackworth gear the distance from the weigh shaft to the rear axle has quite a bit of effect on the valve events, so getting the "ride height" correct is important. The wren has leaf springs all round with short push rods to connect to the axle boxes. Shortening these rods lowers the chassis on the wheels.

- there was a tigh spot in the motion that turned out to be connecting rod bearings being slightly too tight tolerances. Fortunatley these are marine style split bearings, so easy to introduce a little "slop" until things loosen up.

- the blower was pretty weak at first. On wrens the piping for this runs from the cab, under the left hand side of the saddle tank and into the smokebox; about 4' of pretty small bore copper pipe making a pretty ideal condenser. Mostly just hot water coming out at the business end. Fixed by wrapping the whole pipe with string to insulate (held in place by soaking in thin superglue)

- some injector trouble resulting from the water in the saddle tank getting hot. I have added a couple of layers of gasket material where the tank brackets meet the boiler and smokebox. This blocks the worst of the conducted heat, and increases the air gap underneath the tank itself.

- I am still trying to get the delivery rate from the mechanical lubricator right, it is adjusted by moving the drive rod between different holes on the ratchet arm. Hopefully I am getting close now....

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Re: Jynn: a 7 1/4" gauge wren

Post by Nomis » Mon Jul 13, 2020 6:18 pm

I took a few close-up pictures of various parts of the engine to show some of the fine detail.

I have no idea how Joe managed to machine some of the more complex shapes in the motion work.

You can see the wrapped blower pipe running up to the smokebox here:

ImageDSC_0174 by simon mace, on Flickr

This is the lubricator drive, set here for maximum delivery (which meant a very oily exhaust, and getting covered in sooty black oil spots after driving!).

You can also just see the balance pipe between the two "legs" of the saddle tank. This has a T piece with a large ball valve that makes it quick & easy to drain the tank (either at the end of a run, or the dump hot water & replace with cold).

ImageDSC_0176 by simon mace, on Flickr

A driver's view of the cab. Everything is nice and easy to reach. I cut an opening in the cab roof to give a better sightline of the gauge glass, and Joe mounted the pressure gauge as low as possible for the same reason.
Apart from these things it is all laid out as per the prototype. The small brass handles either side of the boiler are the water controls for the two injectors, and the lever on the floor (left of the firedoor) actuates the draincocks.

ImageDSC_0175 by simon mace, on Flickr

Not sure how visible it is here, but the front part of the footplate is hinged. It flips up to give access to the boiler blowdown and ashpan.
Last edited by Nomis on Mon Jul 13, 2020 6:23 pm, edited 2 times in total.

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Re: Jynn: a 7 1/4" gauge wren

Post by Nomis » Mon Jul 13, 2020 6:20 pm

The finished engine, pretty as a picture :)

ImageDSC_0173 by simon mace, on Flickr

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Re: Jynn: a 7 1/4" gauge wren

Post by Nomis » Tue Jul 14, 2020 12:06 pm

And here she is in action:


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Re: Jynn: a 7 1/4" gauge wren

Post by Nomis » Tue Jul 14, 2020 4:56 pm

And better one of a full lap:


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bambuko
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Re: Jynn: a 7 1/4" gauge wren

Post by bambuko » Tue Jul 14, 2020 5:34 pm

very nice :thumbright:
thank you for sharing

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tom_tom_go
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Re: Jynn: a 7 1/4" gauge wren

Post by tom_tom_go » Tue Jul 14, 2020 7:03 pm

Nomis wrote:
Mon Jul 13, 2020 6:07 pm

- getting the suspension & valve timing to work together. With hackworth gear the distance from the weigh shaft to the rear axle has quite a bit of effect on the valve events, so getting the "ride height" correct is important.
My Sweet Pea also uses Hackworth gear which required the suspension and valve timing to be adjusted when I first got it to get it spot on (it now runs in forward and reverse with no issues and does not need a push to get going even when pulling passengers, only tested with 8 people so far).
Nomis wrote:
Mon Jul 13, 2020 6:07 pm

- the blower was pretty weak at first. On wrens the piping for this runs from the cab, under the left hand side of the saddle tank and into the smokebox; about 4' of pretty small bore copper pipe making a pretty ideal condenser. Mostly just hot water coming out at the business end. Fixed by wrapping the whole pipe with string to insulate (held in place by soaking in thin superglue)
The blower pipe arrangement on your Wren is similar to that on my Sweet Pea, however, I have not experienced any condensate issues. Trying to think what would cause this on your loco?
Nomis wrote:
Mon Jul 13, 2020 6:07 pm
- some injector trouble resulting from the water in the saddle tank getting hot. I have added a couple of layers of gasket material where the tank brackets meet the boiler and smokebox. This blocks the worst of the conducted heat, and increases the air gap underneath the tank itself.
I drilled a small breather hole through the plug of my saddle tank on my loco as the fit was very snug.
Nomis wrote:
Mon Jul 13, 2020 6:07 pm
- I am still trying to get the delivery rate from the mechanical lubricator right, it is adjusted by moving the drive rod between different holes on the ratchet arm. Hopefully I am getting close now....
I also had to adjust the arm on my mech lubricator when I first ran my loco as it showered me in oil. Too much oil is better than too little though!

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Re: Jynn: a 7 1/4" gauge wren

Post by tom_tom_go » Tue Jul 14, 2020 7:05 pm

Thanks for sharing the video, I am very much in awe of what you have achieved.

Hopefully my next house move will allow me to build a small line to have a play on with my loco (when the kids finally move out!)

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Re: Jynn: a 7 1/4" gauge wren

Post by Nomis » Tue Jul 14, 2020 8:09 pm

Glad you enjoyed the pictures and video.

I think the blower issue was just due to the length of pipe, it goes quite a long way round from the steam turret up to the smokebox (plus my initial testing was in cold december / january weather.

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Re: Jynn: a 7 1/4" gauge wren

Post by Old Man Aaron » Mon Jul 20, 2020 12:43 am

Quite like those little Kerr Stuarts. And such an in-depth write-up to boot! :thumbright:
Anzac Creek Workshops blog - HO, 16mm & 2ft endeavors.

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Re: Jynn: a 7 1/4" gauge wren

Post by Keith S » Sun Jul 26, 2020 8:14 pm

That second video (the full lap) shows you have a talent for railway videos too; I can't imagine anyone would fail to enjoy that. It shows the railway, wagons, and locomotive from all the angles and vantage points one could wish for in order to get a good idea what it's really like- even a bit of flange-squeaking going across the drive! Just as good as any railway video, I think.


My garden isn't even large enough to build a railway for my 16mm scale locomotive. I'm pretty envious of your situation!

The locomotive is the perfect match for your garden.

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Andrew
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Re: Jynn: a 7 1/4" gauge wren

Post by Andrew » Fri Jul 31, 2020 11:57 am

Great videos, and the loco and garden are both lovely. A really interesting route, I especially like the "wilder" bits, as I'm sure the local wildlife does...

If I had a little more space and a LOT more engineering ability I'd be very tempted!

All the best,

Andrew.

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