16mm scale "Linda"

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Trevor Thompson
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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
The rocker arm pin which is tapped 8BA at each end:
Screen Shot 2020-11-07 at 21.29.08.png
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
the outer rocker arm. Again tapped 8BA but no nut. Pin through.
Screen Shot 2020-11-07 at 21.29.46.png
valve link:
Screen Shot 2020-11-07 at 21.30.01.png

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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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bambuko
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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
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.

Trevor

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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
Next stage is to set up the rotating table and convert the machine to milling form. Centre for the hole and drill 1.5mm:
IMG_1034.jpg
IMG_1036.jpg
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
And finally after fitting onto Linda. Holes drilled, tapped and the knobs secured with locktight. The one on the smokebox:
IMG_1041.jpg
and on the water tank:
IMG_1042.jpg

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dewintondave
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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.

Trevor

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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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Re: 16mm scale "Linda"

Post by Keith S » Tue Nov 10, 2020 6:02 pm

Trevor Thompson wrote:
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.

Trevor
A bit crude, maybe, but this is pretty much the method Roundhouse advocates for valve-timing on their kit models.

I must say how glad I am you've decided to start posting about this model. Many of us lack the skill and/or machinery to make a locomotive completely from scratch, and there are several of these in the works right now which is very inspirational. And, this shouldn't be considered a slight towards anyone's building, but the other chaps, well it seems to me that their builds are very polished- which is a good thing- but I especially like this one because you readily admit that sometimes your ideas don't work out, and your locomotive (again I hope not to cause offence) bears the tool-marks from having been made out of pieces of metal hand-worked the old-fashioned way. Which again, isn't necessarily a virtue nor is it a fault, but for me it's just a little easier to appreciate in a way for someone like me who struggles to do a nice job on a Brandbright coach-kit and usually has to do things twice or thrice before they work out. I like to hear about the trial-and -error approach to home engineering, although when it happens to me I struggle to persevere sometimes.

Anyway, I just wanted to register my appreciation for your work, and I'm looking forward to seeing more.

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Re: 16mm scale "Linda"

Post by Hydrostatic Dazza » Tue Nov 10, 2020 7:51 pm

Bravo
Cheers from Dazza, The Hydrostatic Lubricator 8)
The chances of finding out what’s really going on in the universe are so remote, the only thing to do is hang the sense of it and keep yourself occupied. Douglas Adams

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Re: 16mm scale "Linda"

Post by GTB » Wed Nov 11, 2020 9:58 am

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. I kept breaking them. So I would certainly lock the eccentrics permanently before assembly next time.
Slotted head grub screws are about as much use as a chocolate teapot in my opinion, much too easy to break off one side of the slot.......

I've used M3 hex socket grub screws in the eccentrics of the two sets of Stephensons vg that I've scratchbuilt so far and 6BA in the set I rebuilt. I've not had any movement of the eccentrics in service once the vg is set up and the grub screws tightened.

I can drive down the road and buy M3 hex socket grub screws, but I had to import the 6BA ones from the UK, which is why I've now standardized on M3.

Personally I prefer to be able to set each eccentric separately. Prototype eccentrics were keyed to the axle, so the only way to adjust the valve gear was to remove the eccentric rods and get a blacksmith to stretch, or shrink, the rod(s) that needed adjustment. Not for this little black duck........

If you use hex socket grub screws, the key can be also used to sight the eccentric position relative to the crank pin, which makes adjustment fairly easy. A suitably positioned hole drilled in the eccentric straps means adjustments can be made with the valve gear fully erected and the hole can do double duty as an oiling point.

Regards,
Graeme

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Re: 16mm scale "Linda"

Post by Trevor Thompson » Wed Nov 11, 2020 3:53 pm

[/quote]

A bit crude, maybe, but this is pretty much the method Roundhouse advocates for valve-timing on their kit models.

I must say how glad I am you've decided to start posting about this model. Many of us lack the skill and/or machinery to make a locomotive completely from scratch, and there are several of these in the works right now which is very inspirational. And, this shouldn't be considered a slight towards anyone's building, but the other chaps, well it seems to me that their builds are very polished- which is a good thing- but I especially like this one because you readily admit that sometimes your ideas don't work out, and your locomotive (again I hope not to cause offence) bears the tool-marks from having been made out of pieces of metal hand-worked the old-fashioned way. Which again, isn't necessarily a virtue nor is it a fault, but for me it's just a little easier to appreciate in a way for someone like me who struggles to do a nice job on a Brandbright coach-kit and usually has to do things twice or thrice before they work out. I like to hear about the trial-and -error approach to home engineering, although when it happens to me I struggle to persevere sometimes.

Anyway, I just wanted to register my appreciation for your work, and I'm looking forward to seeing more.
[/quote]

Thanks for the kind words. It is good to hear that my input to the website is appreciated.

Trevor

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Re: 16mm scale "Linda"

Post by Trevor Thompson » Wed Nov 11, 2020 3:59 pm

Maybe it is worth persevering with grub screws, certainly M2.5 sounds attractive - I will have to look to see if I have an M2.5 tap? Probably need to buy one! I am planning a Stephenson valved model of one of the large England engines - so that might be the time to try it.

The De Winton has fixed eccentrics - and I hope I have silver soldered them in the correct position! Time will tell.

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