Author Topic: A Robinson, in the " Making "  (Read 9930 times)

Offline Alyn Foundry

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A Robinson, in the " Making "
« on: April 16, 2018, 04:30:25 PM »
Hello All.

A few weeks ago my two youngest sons and I attended the Spring opening event at the Anson Engine museum. We had the privilege of playing with one of Geoff's oldest toys! The engine is a Robinson type
" HA " that has recently been fully restored to working condition by Dave Allen, the man on the right in the video. This engine had seen some hard action and the crankshaft was so badly worn that a new one had to be made.

These engines were designed to run on Paraffin/Kerosene and employed a " permanent lamp " to keep both the ignition tube and vapouriser hot. They were listed as HA being up to 10 HP then the HB up to 20 HP, in different bore and stroke ratios.

At present this engine is a " sole survivor " and my sons suggested that a model should be made. A few cursory measurements were made, the flywheel in particular. It was a massive 27" in diameter, half scale, out of the question. But.... at 1/3 rd scale things started to gel, my " X " type flywheel is nearly 9" in diameter and is equally as chunky. Hmmm, a Robinson, in the " Making "

<a href="https://www.youtube.com/watch?v=nlpRdfHx1Vk" target="_blank">http://www.youtube.com/watch?v=nlpRdfHx1Vk</a>

Over the next few weeks I'll take you on a journey of how an engine is scaled, patterned, cast and machined and hopefully a finished working model.

Cheers Graham.


Offline Jasonb

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Re: A Robinson, in the " Making "
« Reply #1 on: April 16, 2018, 05:10:07 PM »
Looking forward to following this.

J

Offline zeeprogrammer

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Re: A Robinson, in the " Making "
« Reply #2 on: April 16, 2018, 06:19:57 PM »
That'll be an interesting journey.  :popcorn:

On the left side of the engine there is a cylinder looking thing hanging down. Is that just a weight?
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
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Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #3 on: April 16, 2018, 06:43:04 PM »
Thanks Jason.   :ThumbsUp:

The Flywheel.

I've got a " thing " about flywheels. Always have....

Back before the days of printing things the flywheel pattern was quite a laborious process. My technique was to use good quality marine ply, 13 to the inch stuff.

I'd cut a disc or a square and proceed to machine the outer and inner rim profile to the correct size, not forgetting " shrinkage allowance " and depending on the job double shrinkage to allow for the wooden master to become an Aluminium master. By using plywood I could machine down to leave a single ply where I would be able to lay out the spokes. Before removing the blank I'd put a hole in the centre to take the hub spigot. Invariably my spokes would start out as cut lengths of " quadrant beading " the taper was arranged by using dress making pins at the small end and cocktail sticks at the hub end. Once the glue had set good old car body filler was used to fill and blend the gaps and create the curves.

The attached picture shows both a Robinson hot air and an R.L.E. " primary master " half. These patterns would then be moulded in sand, poured and cast twice. They were then " paired " together to fine finish and become the foundry " master pattern ".

The second picture is of the Robinson " X " type flywheel foundry master.

Cheers Graham.

Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #4 on: April 16, 2018, 06:47:30 PM »
That'll be an interesting journey.  :popcorn:

On the left side of the engine there is a cylinder looking thing hanging down. Is that just a weight?

Hi Zee.

Thanks for looking in, yes, it is in fact a " pendulum " governor. They are a rare sight and only work well if the engine is firmly anchored.

Cheers Graham.

Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #5 on: April 16, 2018, 07:17:22 PM »
WARNING

This engine will not be a true scale replica.... but a close facsimile, we can't have the full size one to play with!

Now a little more history.  The businesses of AE & H Robinson and L Gardner and sons were virtually at the opposite ends of the same street. Robinson were making engines before Gardner, in fact at that time Gardner's were general machinists, they made the parts like cranks and conrods for Robinson. Is it little wonder that Gardner's first engine a size 1 should look almost identical to a Robinson HA? Well, take a look at our modified Gardner size " 0 " base.   ;)

Cheers Graham.

Offline RayW

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Re: A Robinson, in the " Making "
« Reply #6 on: April 16, 2018, 07:20:14 PM »
Hi Graham,

I look forward to following this project with interest. Could there perhaps be a future kit in the making?

Regards

Ray
Ray

Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #7 on: April 17, 2018, 01:28:52 PM »
Hi Ray.

Let's wait and see.... ;)

Patterns, solid versus split.

There's probably a few readers wondering why we seem to make more work than necessary with regards to patterns.

A lot of parts that we need to make will need to use both halves of the moulding boxes. If we had a solid pattern the moulder would literally have to bury the item, turn the box over and then dig down to the centre. This is both messy and time consuming and the end results can be inconsistent.

With a split pattern the moulder simply lays down the first half on the board covers it with " virgin " facing sand then backs out the box with tempered older used sand. The box is turned over, top box placed and filled in the same fashion. For things like a flywheel the spokes will have excellent definition because the moulder didn't have to dig down, firm and part.

I'm hoping the above explains why we spend the extra time in making patterns in two halves rather than a more simple solid one?

Cheers Graham.

Offline crueby

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Re: A Robinson, in the " Making "
« Reply #8 on: April 17, 2018, 06:37:34 PM »
Graham, great descriptions on how it all works, following along with interest!

 :popcorn: :popcorn: :popcorn:

Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #9 on: April 17, 2018, 08:00:06 PM »
Thank you crueby.

Cores, prints and boxes.

Almost all readers will know that to make a casting hollow a sand core is placed within the mould for the molten metal to run around. Once cooled the core is broken away leaving the cavity.

The attached picture shows the piston pattern and core box for my failed attempt at the quarter scale Hornsby Akroyd. Please note that the longer small diameter is the " print " and the larger diameter forms the piston casting proper. If you look carefully you can see the Hornsby part numbers faithfully reproduced using pattern makers letters. Also the bosses that create the bosses for the gudgeon pin.

There's many a material to make cores with these days Silicates, Resins etc. All that's required is a solid mass that'll stand up to the strain of the molten metal as it races around.

In the past I've actually used ordinary flour, water and Silica sand to make simple cores for Aluminium work.

Sometimes a pattern can be made to make its own core, in the same picture above the Aluminium is a Nylon pattern. This was used to make two halves of a hollow piston for my, now shelved Brayton ready motor. These type of patterns are called " self codding " but can only be used on shallow draughts because if pushed too far the bond can break.

I'm a little under the weather at the moment, slight chest infection but I've managed to find some nicely seasoned Ash ready to make our cylinder pattern from.

More to come, cheers Graham.

Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #10 on: April 17, 2018, 08:10:47 PM »
I've just remembered this video I did for Ray.

<a href="https://www.youtube.com/watch?v=L5wxf5x_oBs" target="_blank">http://www.youtube.com/watch?v=L5wxf5x_oBs</a>

It's been doing rather well in India and Pakistan....   :)

Cheers Graham.

Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #11 on: April 27, 2018, 07:03:19 PM »
Not quite " Robinson " !!

It's amazing what can be done with time, patience and a few bits of seasoned Ash, glue and body filler!

Attached is a picture of the remake of two missing patterns for my Isaac F Allman engine.

Just some final detail finishing and a coat of Red Oxide primer before a trip to the foundry.

Cheers Graham.

Offline Jasonb

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Re: A Robinson, in the " Making "
« Reply #12 on: April 27, 2018, 07:16:57 PM »
They look good Graham and should save me some time if I'd had to carve from solid.

Online Jo

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Re: A Robinson, in the " Making "
« Reply #13 on: April 28, 2018, 07:03:05 AM »
They look good Graham and should save me some time if I'd had to carve from solid.

That's one of the main reasons we use castings  ::)

They also let you cast in cores that would be very difficult to machine unless you made the item by assembly and then you are forced to paint the item (or wait for the dirty black line when the silver solder tarnishes in years to come  :facepalm2: )

And sometimes it is cheaper to use castings than start from an expensive piece of barstock   ;)

Jo
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Offline Jasonb

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Re: A Robinson, in the " Making "
« Reply #14 on: April 28, 2018, 07:40:12 AM »
But using castings does take some of the enjoyment and satisfaction away from the process*, hardly exciting just facing off and drilling/boring a couple of holes in a piece like that. It also saves the issue of finding flaws in the casting and having to spend time making the outside look right where the two halves of the mould have shifted.

Tarnished solder joints tend to be more of an issue on fabricated brightwork when parts have been joined rather than cutting from a larger piece which would not normally have been supplied as a casting anyway. I do tend to paint the majority of "castings" anyway so that is not an issue for me, might be for those that don't get round to finishing and painting their engines.

Cost only really comes into it on larger parts. I've made six engines in that 24mm bore series now all about the size of a Stuart No 7 or No 8 and I would say they have cost me a 1/3 to a 1/4 of what one of those Stuarts would cost and that includes the barstock and fixings as well as materials to make the "castings" Even those large otto castings worked out about the same as using CI bar and 2 out of 3 columns were faulty.

J

*Unless you make your own patterns and maybe even do you own casting.
« Last Edit: April 28, 2018, 08:01:24 AM by Jasonb »

Online Jo

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Re: A Robinson, in the " Making "
« Reply #15 on: April 28, 2018, 09:00:57 AM »
I made the comments because all your negative comments about castings can discourage beginners  :disappointed: You are not a beginner.

But using castings does take some of the enjoyment and satisfaction away from the process*,


Speak for yourself: fondling bar stock does nothing for me  :hellno:

Cost only really comes into it on larger parts.

Until a beginner has a comprehensive set of bar stock then every bit will require them to buy yet another bit of bar stock  :facepalm: Kirt at Hemmingway is very good with his casting kits he provides all the bar stock so that beginners do not need to waste time and money buying stuff they probably won't need and will lay around rusting on their shelves  :Doh:

Yes a few lucky people like me have over the years acquired material that now has that Alyn Foundry special protective coating but always make sure you know what you are getting. My steel stocks all came from the Apprentice School or Aero Space Companies  :D

Jo
Enjoyment is more important than achievement.

Offline Jasonb

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Re: A Robinson, in the " Making "
« Reply #16 on: April 28, 2018, 10:12:53 AM »
That will be all the supplied imperial barstock and BA fasteners that most beginners don't understand will it ;)

Just worked out the cost for the Vertical that I have just finished if I had to go out and buy every bit of material. Used M-Machine pricelist and going for 12"/300mm lengths of the smaller section and 1"/25mm of the larger section materials you could buy all materials for £80 plus VAT so say £100 and say another £20 for packs of 50 nuts in the sizes needed.
That's the same size as a Stuart No 7 and the 7A sells for £260. so allowing for the fact you will have more material that can be used on the next engine my 1/3rd the cost was about right. You also have easy to hold lengths and spare material if you muck up. How can that be a bad buy for a beginner?
« Last Edit: April 28, 2018, 11:38:58 AM by Jasonb »

Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #17 on: April 28, 2018, 12:08:48 PM »
Good morning All.

Whilst I understand your point of view Jason I'm with Jo on " castings " being favoured over bar stock.

Perhaps it goes back to the many years of restoring vintage engines where missing parts were replaced with newly machined castings. I'm also a little lazy I found that making a pattern with all the shape was far easier than shaping a hard metal lump!

We're just waiting for it to stop raining long enough to get the " pot " on and do some casting of the Robinson " HA " base pattern.

Cheers Graham.

Offline Gas_mantle

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Re: A Robinson, in the " Making "
« Reply #18 on: April 28, 2018, 01:05:17 PM »
The subject of castings v barstock is an interesting one. I find that working from barstock worked out expensive to start with, when you are new to the hobby virtually every component you make needs the purchase of more barstock of a different size / material etc. As time goes on and you acquire a stockpile it becomes far cheaper. If I need to buy 2" of something I'll buy 12" and the rest is put aside for future projects so I have now reached the point where I can build most of the stuff I'm interested in at minimal cost.

To me the way forward seems to be buy a casting for the odd part that is difficult to make (or costly) but try to fabricate the rest. The Stuart no4 replica I'm working on is going to be primarily a barstock engine (I bought the trunk guide for £1.40) but in the case of the cylinder / valve chest when I tried to buy the cast iron stock I found it as expensive as buying a casting so I did the common sense thing and bought a casting.

I reckon all in I can build a Stuart no4 lookalike for £80, it's not going to be perfect and it won't sell for the kind of money a real one does but at 20% of the cost I should have a reasonable engine and the satisfaction of saying I built it (or most of it)


Offline Jasonb

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Re: A Robinson, in the " Making "
« Reply #19 on: April 28, 2018, 01:18:57 PM »

We're just waiting for it to stop raining long enough to get the " pot " on and do some casting of the Robinson " HA " base pattern.


I take it that as you sound like you are casting at home that this will be the Aluminium pattern that will then go off to the iron Foundry? Would be interested to see a couple of photos of your casting set up.

Agree with you that the larger full size and big model parts are often better done with castings particularly if you have a local Foundry that will do one offs. But if you only want a small part for a model having to spend a day driving to and back from a foundry twice plus petrol costs will soon make cutting from the solid seem attractive ;)

Online Jo

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Re: A Robinson, in the " Making "
« Reply #20 on: April 28, 2018, 02:20:02 PM »
How can that be a bad buy for a beginner?

And they will have to buy lots of other tools over and above the lathe that most people start with when they build model engines, tools that most of us slowly buy over many years like silver soldering equipment which requires even more skills that the beginner must learn before they can achieve their first engine   :(


Most of the model engineering companies who provide us with, amongst other things, excellent castings sets are making very little in the way of profits: use them or loose them. Encouraging scratch building from the new customer market will ensure we loose them earlier   :toilet_claw:


Jo
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Offline Jasonb

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Re: A Robinson, in the " Making "
« Reply #21 on: April 28, 2018, 02:24:41 PM »
I'm not going to disrupt Graham's thread any more but if you want to move these posts to a new thread it would be worth continuing

Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #22 on: April 28, 2018, 02:48:37 PM »
No problem, it's a lively debate....

In essence that's what this thread was all about. Showing how a model starts from either an idea or the real thing. The pattern making, casting and machining until a finished product.

Anyone can make patterns and almost anyone can make their own Aluminium castings too.

My first casting was actually in Brass believe it or not. I used a converted " Rayburn " fire, the one with the segmented glass front door. Used coke and air and a small 10 Lb " Morganite " crucible. I did everything right until I poured the mould. Disaster, just as the sprue was filling the boxes parted and I had what I learned later, in good old foundry parlance, a " Pisser " !! Yes you guessed it, I hadn't put any weights on the top box. The displacement of molten Brass is far greater than that of damp sand!

That event was 40 years ago now....

Cheers Graham.

Offline Jasonb

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Re: A Robinson, in the " Making "
« Reply #23 on: April 28, 2018, 03:09:42 PM »
Just hope you did not scorch the front room carpet too much.

Well if you don't mind then I'll comment on Jo's last post.

I don't see why anyone making one of my 24mm bore engines would need to buy much more in the way of tools and tooling over and above the lathe. Granted mills etc will make the job easier but any of them could be done on just the late, if I can make a Minnie with just the lathe when I was still very much a beginner then I don't see why anyone else could not manage one of these simpler engines with just a lathe.

As for silver soldering a couple don't need any and those that do use it could have those parts made in other ways with either simple screw together construction or as the likes of Ramon have shown a steam engine cylinder can be stuck together with JBWeld and hapily be steamed.

Yes if the suppliers don't move with the times they could disappear particularly with the growing number of people with CNC and 3D printing in their home workshops which makes it even easier for the scratch builder to make their own patterns or machine complex parts from solid. But at least the models being made will cover many new and varied subjects rather than just banging out the same 100year old designs again and again.

Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #24 on: April 28, 2018, 03:52:51 PM »
Hmmm....

Well this Robinson in the " Making " will definitely be a 100 year old design!!   :)

Online Jo

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Re: A Robinson, in the " Making "
« Reply #25 on: April 28, 2018, 04:11:32 PM »
Please take note Graham: Jason clearly doesn't want those casting sets he is trying to buy from you :hellno: Just like that totally unnecessary Robinson X type cylinder, flywheel and the base that you forced him to buy so that he didn't have to make them out of bar stock  :Lol: 

If you think about it the heretic has brought more castings than I have this year  :lolb: He says one thing... and does another  :-X

Jo
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Offline Jasonb

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Re: A Robinson, in the " Making "
« Reply #26 on: April 28, 2018, 04:36:27 PM »
Not really Jo just showing that engines can be made either way and that castings don't have to limit your choice of subject. I'm happy to build both ways or mix the two to get the results I personally want, did not know I could not share my views with others.

The way some people go on about castings the beginner could be lead to believe its the only way.

I've only bought one and a half casting set this year but completed two scratchbuilds with a third underway. Also I don't have any where near the amount you have stashed away.

Offline Gas_mantle

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Re: A Robinson, in the " Making "
« Reply #27 on: April 28, 2018, 04:46:17 PM »
Funnily enough in the last few minutes, I've just bought a 10v casting set on ebay - I didn't really need it but it's still sealed in the plastic and has the Andrew Smith book included - It was a bargain I couldn't resist :-)

I now have 3 verticals to build  :)

Offline Jasonb

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Re: A Robinson, in the " Making "
« Reply #28 on: April 28, 2018, 04:55:29 PM »
If you can get them at a good price then why not. That's probably why Jo has bought less than me this year as she has very bought all that Eric had to sell at a very good price and does not want to spend more on anything else, not that there is much left that she has not already got :embarassed:

Offline zeeprogrammer

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Re: A Robinson, in the " Making "
« Reply #29 on: April 28, 2018, 05:17:03 PM »
Apologies if I shouldn't be throwing in my two cents...

Regardless of some people's opinion...I'm still a newbie. I'm currently doing what I consider my 1st casting kit.
It's been much more of a challenge than my other bar-stock engines.
Primarily because it adds challenges to holding parts and determining reference points.
Not to mention (as a newbie) the increase in anxiety knowing that if you screw up...you're buying another casting part (if you can) rather than a bit of bar.

For me, this isn't a discussion about 'one over the other' but 'what is appropriate/desirable for the model and builder'.

Many experienced people (and not so experienced as myself) forget what they didn't know.

My 1st engine was indeed a casting. But a very simple model that came with a 'how-to' video. Even so, I ended up purchasing two more flywheels. (Actually two whole kits because it wasn't just the flywheels I screwed up.)

I remember when I first started this hobby. It's a lot of learning. The machines, tools, methods, finding center, setting cutters, feeds/speeds, and on and on.
At the time I thought 'drill a hole' was it. Not spot, drill, ream. Tapping threads? Who knew there were up to 3 taps to use?

Having said that...when I was young, it was casting kits that caught my attention and ignited the flame.
It burned for some 45 years before I was able to jump in. Had I started with a real casting kit...I think I would have failed and the flame be extinguished.

Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
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Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #30 on: April 28, 2018, 05:51:50 PM »
Well....

I have an engine in the workshop, made from castings that were " leftovers " from the late 1890's.

Several sets of castings and forgings were bought by the Uppingham school from A.S. Barker of Leyton E. London. The story goes that if a student " screwed up " they'd just go and get another from the basement.
This left a few that couldn't be completed and both Vincent and I ended up with the remains. With Vincent's passing I've inherited his set of 3/4 HP engine castings.

I have to agree that castings can present added difficulty when trying to work out a method of action, I always aim for the simplest route. Grip it, centre it machine it.

Cheers Graham.
« Last Edit: April 28, 2018, 05:56:48 PM by Alyn Foundry »

Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #31 on: May 02, 2018, 07:51:11 PM »
A sad moment.

I have to report the demise of a hard working member of the Alyn Foundry team. For at least 25 years my Black and Decker BD 280 powerfile has performed many a task in the pattern shop. Amazingly it's not the motor but the little wheel at the front, despite a couple of try's at repair the belts just keep flying off.

A replacement has been found but I fear it'll never last as long as my B&D has....

The base pattern is coming along nicely....

Cheers Graham.

Offline Tennessee Whiskey

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Re: A Robinson, in the " Making "
« Reply #32 on: May 02, 2018, 08:21:57 PM »
RIP and our regards

Cletus

Offline b.lindsey

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Re: A Robinson, in the " Making "
« Reply #33 on: May 03, 2018, 01:07:18 AM »
Deepest sympathies Graham. 25 years ago things were made to last. These days things are made to use until they break or wear out prematurely,and then to be replaced. It's a disposable mentality that is taking over sadly.

Bill

Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #34 on: May 03, 2018, 11:49:10 AM »
Thanks guys.

Indeed Bill, and we're living on a planet with finite resources. Making things to last should be a priority.

My powerfile almost became an extension of my right hand, making complex radii with the little wheel was easy. The ergonomics of this new one are very different, almost cumbersome.

If anyone has a spare part, the wheel or arm, I'd be happy to hear from them.

Meanwhile, a sketch of the next pattern is always useful as a guide to formulating a plan for the pattern to follow.

Cheers Graham.

Offline RayW

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Re: A Robinson, in the " Making "
« Reply #35 on: May 03, 2018, 06:10:39 PM »
Hi Graham,

Just returned from a week break in your native land and now ready to tackle the Robinson again. Talking of long serving tools, I am now 71 and still have the Black and Decker drill that my aunt gave me for my 21st birthday! It has already outlived several of its later relatives and is still going.

Ray
Ray

Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #36 on: May 03, 2018, 06:53:56 PM »
Hi Ray.

That's good to read, I'm 10 years behind you and also still regularly use a Solon 60 Watt soldering iron that my grandparents bought for me in my early teens.

Some good news though, I managed to find a new arm on eBay that's winging its way to North Wales my BD 280 will be back in " sterling " service!

Cheers Graham.

Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #37 on: February 21, 2022, 01:36:05 PM »
Blimey, how time has flown by….

With number 3 son forced into hibernation for 10 days and the Brayton castings still being made we decided to pick up the Robinson again.

Sadly the Gardner base didn’t allow for 1/3rd scale so we started from scratch. I thought we’d try out Polycarbonate sheet this time as it’s very slippery and even tougher for the foundry than wood. Without boring you people too much I’ll just post some pictures of our progress to date.

Please don’t hesitate to ask any questions, that’s if anything isn’t self explanatory.

Cheers Graham.

Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #38 on: February 21, 2022, 01:46:56 PM »
It seems after reading through this thread I promised a video of the famous Robinson “ pendulum “ governor, well….

<a href="https://www.youtube.com/watch?v=aPgSG3JbjOc" target="_blank">http://www.youtube.com/watch?v=aPgSG3JbjOc</a>

Offline Jasonb

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Re: A Robinson, in the " Making "
« Reply #39 on: February 21, 2022, 04:02:15 PM »
Wot, no more progress today :( ;)

Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #40 on: February 21, 2022, 04:25:54 PM »
Wot, no more progress today :( ;)

Still a few hours left Jason….  ;)

Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #41 on: February 21, 2022, 08:48:40 PM »
Beginning to look like a Robinson Oil engine….

Offline Craig DeShong

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Re: A Robinson, in the " Making "
« Reply #42 on: February 21, 2022, 10:16:07 PM »
I am constantly amazed at the vast variety of governing devices I’ve seen on engines.  This one “takes the cake”.
Craig
The destination motivates us toward excellence, the journey entertains us, and along the way we meet so many interesting people.

Offline crueby

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Re: A Robinson, in the " Making "
« Reply #43 on: February 22, 2022, 01:34:05 AM »
That governor video is amazing, how they came up with that, wow.

Offline Jasonb

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Re: A Robinson, in the " Making "
« Reply #44 on: February 22, 2022, 07:07:03 AM »
Thanks for leaving the loose piece unpainted I can see exactly how you are going to do that bit now, just don't let it get lost.

Is there draft angle on the exhaust mounting boss?


Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #45 on: February 22, 2022, 11:09:12 AM »
The governor is both simple and effective but not very good on an unstable platform. The engine has to be firmly planted to get results. There’s been many an accident on the rally field where they’ve gone out of control due to the engine rocking in opposition to the pendulum.

Morning Jason.

Yes there’s a draft angle but much less than 2 degrees. The new foundry although well versed in “ Greensand “ moulding seem to prefer “ air set “ so you can get away with virtually zero draft.

Cheers Graham.

Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #46 on: February 26, 2022, 11:47:23 AM »
Although some patterns are fairly simple most are pretty complex.

With the aid of some decent wood, a lathe and my trusty Power file the cylinder head pattern is now ready for filleting and paint. A small core print has been made because the inside, where the ignition tube is fixed is angled at around 45 degrees. The second picture is of a burned out head, in fact the full size engine is now on its third one having worked very hard in its day.

By tomorrow I’m hoping to be able to show you the cylinder jacket with its core box. This part will eventually have the honed cylinder liner, a separate component, glued into position.

Offline Jasonb

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Re: A Robinson, in the " Making "
« Reply #47 on: February 26, 2022, 03:43:34 PM »
Well at least you should not have a problem replicating that rusty finish ;)

At the rate you are going we should see a running engine by Easter :stickpoke:

Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #48 on: February 26, 2022, 08:13:55 PM »
A little sooner than advertised….

The core box started out from two pieces of the same hardwood that made the outer cylinder jacket pattern. These had been thicknessed at my local sawmill. Using 4 wood screws to secure the halves the block was centred up in the 4 jaw chuck. The first operation was to drill right through at 3/4” diameter which matches the smaller core print on the cylinder pattern. The hole was then bored out to suit the open end.

Using an internal screw cutting tool the water jacket space was bored between two pencil marks on the shank. This was deepened by about 3/8” all round.

The final part was to secure two pieces of hardwood to the side of the core box to make the exhaust tract form from the cylinder to cylinder head tract. This is something I have never done before so it will be quite interesting to see how the small core reacts to being almost totally enveloped in molten Iron.

Alan is Beavering away with the bed pattern, hopefully some pictures tomorrow.

 :cheers:


Offline Jasonb

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Re: A Robinson, in the " Making "
« Reply #49 on: February 26, 2022, 08:37:36 PM »
Graham, is there any means to hold the core in position radially so that there is no risk of the exhaust core drooping down and possibly touching the edge of the pattern

Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #50 on: February 27, 2022, 11:33:00 AM »
Morning Jason.

Well spotted….   ;)

Not at this moment there isn’t. To make the core box easier to use I chose to run the tract through the box split line. I’m hoping that the rather fragile core will emerge without the right angled section breaking away during handling.

If folks look closely at the cylinder they’ll notice that the exhaust mounting actually runs from the centre line to the bottom.
This will mean that the core needs to be skewed slightly from its centre line so the end of the tract becomes central to the spigot. Once this angle is ascertained a small section of the cylinder core print will be cut off and glued into the core box to act as a register.

 :cheers:


Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #51 on: February 27, 2022, 11:55:33 AM »
With the engine being what is known in the Stationary engine movement as a “ headless “ type the cylinder bore can present some real problems regarding boring and honing. Our first model, the Robinson type “ X “ that was built over 30 years ago had the same problem. After a great deal of thought at the time, a separate cylinder liner was used to overcome this problem.

I have obviously incorporated the same method this time around and if you look closely at the core box you’ll see that the water jacket is only brought to the front, shy of the exhaust port. I have also reduced the draft angle to a minimum to facilitate ease of drilling the top and bottom water cooling tracts. The casting can then be bored out to the cylinder liners outside diameter and the finished liner can be glued into position.

As luck would have it the aborted 1/4 scale Hornsby Akryod piston and cylinder liner patterns/core boxes will come in very handy for this model.

 :cheers:

Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #52 on: March 01, 2022, 11:49:48 AM »
Dydd Dewi Sant Hapus

A bright but chilly start to Saint David’s day today here in North Wales and we do have a couple of Daffodils in bloom.

Due to paint incompatibility some of the patterns had to be re sprayed but we’re back on track. The small Acrylic tube is the core box for the angled ( horizontal ) ignition tube and vaporiser, part of the cylinder head.

 :cheers:

Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #53 on: March 05, 2022, 01:37:19 PM »
With some help from another pattern maker we’ve finally reached the end of this particular thread. I hope I have been able to perhaps inspire one or two to try this avenue for a new project? Just some minor adjustments and painting before they are sent to the foundry.

With today’s modern equipment in the form of CNC and 3D printing, pattern making couldn’t be easier !

Obviously I’m able to share the fruits with other, like minded engine builders and I shall start a new thread here as the castings become available.

Many thanks to those that contributed, and please don’t hesitate to ask any questions if something is unclear.

 :cheers:  Graham.

Offline Jasonb

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Re: A Robinson, in the " Making "
« Reply #54 on: March 05, 2022, 04:03:20 PM »
Well I've enjoyed following along despite some of my opinions on castings  ;) and look forward to seeing what comes out of the sand. Should make a nice companion for anyone who has an X-type and if you can get it to run off the "blowlamp" with it's limited heating that will look the part when running particularly if it can be kept a san oil burner rather than propane.

J

PS don't forget the inlet valve guide. :)

Offline Alyn Foundry

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Re: A Robinson, in the " Making "
« Reply #55 on: March 05, 2022, 07:20:55 PM »
Thanks Jason.

Well, pattern making is really only fabrication in another material isn’t it?   ;)

I have no doubts about the engine running, my first model oil engine was a converted Sphinx. It had a Sparklets soda siphon CO2 bulb stuck in the front end. The problem was with stopping it from revving its  :censored: off ! The Akryod was problematical due to scale, I have since discovered that the water cooled injector wasn’t being cooled enough and the oil would vaporise within it.

The Robinson is quite different insofar as the oil sits directly on the valve seat and is partially atomised by the rattle as it enters the combustion chamber. The oil is then further vaporised and ignited by both compression and the hot tube. Luckily it also has the “ hit and miss “ pendulum Governor to keep the RPM in check.

Today saw the arrival of 4 lengths of 1/2” diameter Silver Steel so a couple of crankshafts are in the offing….

 :cheers:  Graham.

Sphinx Oil engine on the left hand side. Circa 1986.

Offline Jasonb

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Re: A Robinson, in the " Making "
« Reply #56 on: March 05, 2022, 07:50:08 PM »
I watched the video you posted at the beginning of this thread again just now and the blowlamp looks to have quite a sizable burner by way of diameter so it may be possible to use a modified Sievert or as I mentioned elsewhere one of the "kitchen" type torch burners. If this were mated to a dummy can and the support for the platform that the blowlamp sits on made with a hollow bracket then you could plumb it in to propane but have it look like the blowlamp was doing the work. That is unless you are up for making a miniature paraffin blow lamp :stickpoke:

Certainly like the idea of an oil engine as it's something else to cross off the list. I notice the two flywheels on the oil Sphinx no diubt to help carry it over with the higher compression.

Online Roger B

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Re: A Robinson, in the " Making "
« Reply #57 on: March 06, 2022, 08:36:05 AM »
Hot bulb engines typically had quite low compression ratios, around 6-1 depending on the fuel type. Some of the Lanz Bulldog models have overcome the problem of keeping the bulb hot by using a semi concealed automotive diesel glowplug.
Best regards

Roger

Offline ettingtonliam

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Re: A Robinson, in the " Making "
« Reply #58 on: March 06, 2022, 12:34:02 PM »
With some help from another pattern maker we’ve finally reached the end of this particular thread. I hope I have been able to perhaps inspire one or two to try this avenue for a new project? Just some minor adjustments and painting before they are sent to the foundry.

With today’s modern equipment in the form of CNC and 3D printing, pattern making couldn’t be easier !

Obviously I’m able to share the fruits with other, like minded engine builders and I shall start a new thread here as the castings become available.

Many thanks to those that contributed, and please don’t hesitate to ask any questions if something is unclear.
 

Lovely! I am a self taught pattern maker, and always enjoyed it, regarding it as just another challenge in the creation of a model or a machine. My pattern making highlights were a 24" planer based on a Tom  Senior No. 3, and the recreation of a Stuart Turner 600 gas engine. The cylinder block incorporated 5 separate cores and I built a wooden model just to show the foundry how it was all supposed to fit together. I believe they used it as a training exercise for one of their apprentice moulders! Mine were all traditional loose wooden patterns, mostly pine, but I did the flywheel (14" dia, 35 lb weight) as a split pattern by building up a sandwich of 12mm MDF and then shaping the curved spokes with a hand held router.

« Last Edit: March 06, 2022, 06:05:45 PM by Jo »

Offline Jasonb

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Re: A Robinson, in the " Making "
« Reply #59 on: August 15, 2022, 04:53:52 PM »
I'm sure someone is trying to bring me back from the dark side and convert me to the way of the casting  :hellno: as I seem to keep finding various boxes on my doorstep packed with bits of cast iron.

This rather weighty one turned up today tipping the scales at 20kg and there is also the beginnings of another project in there too. Flywheel is just over 9" dia for an idea of scale.


 

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