16mm scale "Linda"

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Trevor Thompson
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Re: 16mm scale "Linda"

Post by Trevor Thompson » Fri Nov 06, 2020 6:49 pm

So I am not the only one who struggled with his software. I keep putting in the relevant dimensions for my attempts at valve gear and it always seems to end up off the screen!

So it isn't a matter of being thick!

Trevor

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Re: 16mm scale "Linda"

Post by Trevor Thompson » Fri Nov 06, 2020 6:58 pm

I have made the steam whistle described in "Steam trains in your garden". Two out of three attempts worked.

I tried the whistle valve from the same book using an M5 tap as suggested in the text but repeatedly failed to get the tyre valve to seat. So I changed the design to make the valve body in two parts, screwed together (M6 threads). That enabled me to make the seat for the rubber seal more accurately ( with a centre drill) and wedging the valve into position between the two parts. That worked. So a whistle and valve:
IMG_1020.jpg
IMG_1020.jpg (350.11 KiB) Viewed 5596 times
and the valve in position on Linda:
IMG_1019.jpg
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It is a bit of an odd end result. I had already fixed the servo for the whistle under the cab floor, and the whistle valve was longer than I anticipated, which resulted in having to cut away the underneath of the operating arm to avoid it hitting the regulator when it was closed. I could have rotated the regulator - but i am reluctant to move things that work as they are. Anyway the regulator and the whistle all work like this!

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Re: 16mm scale "Linda"

Post by Trevor Thompson » Fri Nov 06, 2020 7:17 pm

I have been working on the water tank. Adding the details. I didn't make the water tank to the drawing - I actually made it so that it had a bottom and would hold water if I decide to fit an axle driven water pump. The cam to drive it is already there so it might happen. The underside of the tank:
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Firstly the filler lid :
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IMG_1018.jpg
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I shortened the filler valve so it didn't poke out of the hole.

and the dome. This is my home made ball turning tool, which I used to make it:
IMG_1021.jpg
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As the tank might hold water and the real tank filler already has a filler valve poking through it, I made the dome in two parts, so the top part can unscrew to fill the real tank. So the lower section soldered to the tank:
IMG_1024.jpg
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and the top section with a length of M8 studding in it (the studding was used to hold the dome in the chuck far enough away from the chuck to allow the ball attachment to work) In the background you can see the weir pump from K1 awaiting modification.:
IMG_1025.jpg
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and finally the water tank back on the loco:
IMG_1023.jpg
IMG_1023.jpg (317.7 KiB) Viewed 5596 times
Handrails and dummy injectors yet to be made.

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Re: 16mm scale "Linda"

Post by Trevor Thompson » Sat Nov 07, 2020 7:53 pm

Todays progress is limited. I spent most of it repeatedly dismantling the burner and cleaning the jet!

Anyway I have fitted the 3 d printed couplings with a view to running outside with a train in tow:
IMG_1030.jpg
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I wondered if the problem with the jet was the rubber hose which connects tender to loco. I replaced it. No change. So I now think it is the new gas which I got from screwfix. I emptied the tank and cleaned the jet yet again. So need to get a gas canister from a different source to check if that makes a difference.

As an aside I can confirm that the rubber hose takes the full gas pressure even with a blocked jet, and with a propane/butane mix.

Anyone else had problems with dirt in gas?

Trevor

Back to drawing up the valve gear.

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Re: 16mm scale "Linda"

Post by Trevor Thompson » Sat Nov 07, 2020 9:06 pm

some drawings for the valve gear as requested:
stephenson valve gear linda.jpg
stephenson valve gear linda.jpg (310.07 KiB) Viewed 5575 times
Firstly a general arrangement to name all of the parts and show where they fit together. This is for one cylinder of course. The same things are repeated for the other cylinder and the eccentrics are 90 displaced from this set.

Individual component drawings follow

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Re: 16mm scale "Linda"

Post by Trevor Thompson » Sat Nov 07, 2020 9:10 pm

The eccentric:
eccentric.png
eccentric.png (480.17 KiB) Viewed 5575 times
The centre for the axle is offset from the centre of the eccentric by 3.5mm.

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Re: 16mm scale "Linda"

Post by Trevor Thompson » Sat Nov 07, 2020 9:13 pm

The eccentric strap:
eccentric strap.png
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Re: 16mm scale "Linda"

Post by Trevor Thompson » Sat Nov 07, 2020 9:18 pm

Expansion link:
expansion link.png
expansion link.png (451.63 KiB) Viewed 5579 times
and die block:
die block.png
die block.png (431.79 KiB) Viewed 5579 times

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Re: 16mm scale "Linda"

Post by Trevor Thompson » Sat Nov 07, 2020 9:23 pm

lifting link:
lifting link.png
lifting link.png (464.39 KiB) Viewed 5580 times
and lifting arm:
lifting arm.png
lifting arm.png (437.83 KiB) Viewed 5580 times

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Re: 16mm scale "Linda"

Post by Trevor Thompson » Sat Nov 07, 2020 9:27 pm

link block hanger:
link block hanger.png
link block hanger.png (464 KiB) Viewed 5579 times
and extension rod:
extension rod.png
extension rod.png (389.05 KiB) Viewed 5579 times

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Re: 16mm scale "Linda"

Post by Trevor Thompson » Sat Nov 07, 2020 9:35 pm

Pivot for the rocker arm:
Screen Shot 2020-11-07 at 21.28.52.png
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The rocker arm pin which is tapped 8BA at each end:
Screen Shot 2020-11-07 at 21.29.08.png
Screen Shot 2020-11-07 at 21.29.08.png (419.43 KiB) Viewed 5884 times
the inner rocker arm. It is tapped 8BA and held in place with a nut and pinned as well. If it isn't pinned it will move.:
Screen Shot 2020-11-07 at 21.29.22.png
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the outer rocker arm. Again tapped 8BA but no nut. Pin through.
Screen Shot 2020-11-07 at 21.29.46.png
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valve link:
Screen Shot 2020-11-07 at 21.30.01.png
Screen Shot 2020-11-07 at 21.30.01.png (426.17 KiB) Viewed 5884 times

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Re: 16mm scale "Linda"

Post by Trevor Thompson » Sat Nov 07, 2020 9:41 pm

Some notes on the valve gear. All the pivot points are tapped 10BA and pivot on 10BA bolts. Where possible lock with a 10 BA nut. The only exception to that is the rocker arm where both ends are tapped 8BA. Each end will move if it isn't pinned. The outer end is permanent - the inner can be dismantled. I use 10 BA bolts with 11BA heads throughout.

I hope that the dimensions are readable. Having drawn it in sketch I then had difficulty exporting it without catching loads of unwanted dimensions - which is why I ended up with screenshots. If the original sketch file is of use I can post that as well.

Trevor

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Re: 16mm scale "Linda"

Post by dewintondave » Sat Nov 07, 2020 10:55 pm

Thank you Trevor!
Best wishes,
Dave

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Re: 16mm scale "Linda"

Post by bambuko » Sun Nov 08, 2020 8:10 am

Trevor Thompson wrote: Fri Nov 06, 2020 6:49 pm So I am not the only one who struggled with his software...
It's not just a software. The book is hard read as well.
Don was extremely knowledgable and very respected but as far as I am concerned the master of the subject doesn't necessarily make the best teacher of it ;)
I am still persevering though :mrgreen: - worst part of it is that there is nobody to ask if one has any questions (forum is not the right place for it...)
I personally prefer using prof. Bill Hall's approximate method, followed by Charlie Dockstader's simulator.
Trevor Thompson wrote: Fri Nov 06, 2020 7:17 pm ---I didn't make the water tank to the drawing - I actually made it so that it had a bottom and would hold water if I decide to fit an axle driven water pump...
There seem to be quite a difference of opinion about merits of axle driven pump.
I personally like the idea, but think that it has to be carefully designed.
Trevor Thompson wrote: Sat Nov 07, 2020 7:53 pm ...Anyone else had problems with dirt in gas?...
no personal experience, but here is Dick Moger's comments in G1:
gas.png
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Trevor Thompson wrote: Sat Nov 07, 2020 9:41 pm ...I hope that the dimensions are readable...
Thank you for posting details of your gear.
With the exception of extension rod, which is a bit challenging (but still usable) all of the drawings attached are perfect.

One immediate question is about eccentric.
I am assuming that 3mm dia hole for axle is not quite what it is in reality? :scratch:

I will have more deatiled look at it and come back if I have any questions.
BTW - I am assuming that steam and exhaust ports in your design are as per Charles of K. B. ?

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Re: 16mm scale "Linda"

Post by Trevor Thompson » Sun Nov 08, 2020 10:43 am

Yes the hole in the eccentric might be wrong. I did that from memory (but measured the critical bits).

The rest of the engine is as per the drawings.

Thanks for the info on gas jets blocking. I will have to make a filter.It will have to be very fine though as the No 3 jet has a tiny hole in it.

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Re: 16mm scale "Linda"

Post by Trevor Thompson » Mon Nov 09, 2020 9:53 pm

Todays progress is limited to making handrails for the tank and firebox.

I make my own handrail knobs:

The first stage is to mount stainless rod 4mm diameter in the chuck and turn down the end and tap it 6BA. I then cut a grove either side of where the ball will be created. Then saw the part free, (it is too small to part off reliably) Repeat 6 times:
IMG_1035.jpg
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Next stage is to set up the rotating table and convert the machine to milling form. Centre for the hole and drill 1.5mm:
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IMG_1036.jpg
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and back to the lathe and set each one up in a mandril and file to a ball shape. (To small to use the ball turning tool reliably)
IMG_1037.jpg
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And finally after fitting onto Linda. Holes drilled, tapped and the knobs secured with locktight. The one on the smokebox:
IMG_1041.jpg
IMG_1041.jpg (297.32 KiB) Viewed 5753 times
and on the water tank:
IMG_1042.jpg
IMG_1042.jpg (273.06 KiB) Viewed 5753 times

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Re: 16mm scale "Linda"

Post by dewintondave » Mon Nov 09, 2020 10:34 pm

That is beautiful work Trevor! I must continue my Charles project now
Best wishes,
Dave

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Re: 16mm scale "Linda"

Post by bambuko » Tue Nov 10, 2020 7:07 am

Trevor Thompson wrote: Sat Nov 07, 2020 9:10 pm The eccentric:
...
The centre for the axle is offset from the centre of the eccentric by 3.5mm.
Hi Trevor, what advance did you use for the eccentric (either angular or linear dimension), please?
According to Charles drawings, as designed it has 1/32" steam lap.

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Re: 16mm scale "Linda"

Post by Trevor Thompson » Tue Nov 10, 2020 1:23 pm

The drawings showed 8BA grub screws holding the eccentrics. I adjusted them initially at dead centre. When assembled I adjusted each one until the valves were opening just after dead centre, and closing again after about 75 - 80% of the travel.

A bit crude I know but it seems to have worked.

I think Don Ashton gives a better way, which I will try next time.

I could only get the 8BA grub screws with slotted heads - and they are far too weak. I kept breaking them. So I would certainly lock the eccentrics permanently before assembly next time.

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Re: 16mm scale "Linda"

Post by bambuko » Tue Nov 10, 2020 5:30 pm

Trevor Thompson wrote: Tue Nov 10, 2020 1:23 pm ...A bit crude I know but it seems to have worked...
it's remarkable how forgiving these little steam engines are :thumbup:
Trevor Thompson wrote: Tue Nov 10, 2020 1:23 pm ...I think Don Ashton gives a better way...
Yes, he does.
Setting (or making them) as a pair is definitely much better than juggling four eccentrics :mrgreen:

Trevor Thompson wrote: Tue Nov 10, 2020 1:23 pm ...I could only get the 8BA grub screws with slotted heads - and they are far too weak...
8BA is equivalent to M2.5 - you can easily get stainless allen key grub screws from ebay in this and other sizes.
That is, provided you are willing to go metric :D
for example this is the supplier I use:
grub screw

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