Author Topic: A Robinson from rejects.  (Read 71929 times)

Offline Ian j

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Re: A Robinson from rejects.
« Reply #165 on: February 01, 2018, 06:25:09 PM »
Yes Graham the valve head is secured to the valve stem with a 7Ba screw.
As for getting it running I may be a coward and wait for Ray or Jason to sort out the plumbing for the gas :)
Ian

PS. Graham I only noticed today that you had written my engine number on the back of the name plate,thank you.
« Last Edit: February 01, 2018, 06:54:04 PM by Ian j »

Offline Jasonb

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Re: A Robinson from rejects.
« Reply #166 on: February 01, 2018, 06:39:35 PM »
I cut my inlet valve from a piece of 16mm Stainless and will also make the exhaust from solid.

Crank will be silver soldered and pinned, got to get a bit of 1/2" PGMS first though.

Offline RayW

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Re: A Robinson from rejects.
« Reply #167 on: February 01, 2018, 06:49:11 PM »
I usually either make valves in one piece from stainless or silver solder a disc to a suitable sized stem, then machine head to shape while holding the stem in a collect.
The crank is silver soldered and pinned.
Ray

Offline RayW

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Re: A Robinson from rejects.
« Reply #168 on: February 05, 2018, 02:39:41 PM »
Following a timely reminder from Graham about the problems of getting paint to stick to cast iron that has got impregnated with oil, I gave the base a protective first coat of acid etch primer today, after first wire brushing off most of Grahams special protective coating. I just hope that by doing so, I have not seriously devalued it by destroying the patina!
Seriously, though, Graham has a valid point. With cast iron being porous, it will soak up oil like a sponge and you will then have real problems when in comes to painting, so get some sort of protective coating on before the castings have a chance of being contaminated with oil or grease.

I will be doing more work in due course filling and rubbing down the castings and dealing with any flaws before giving them more primer and top coats.
Ray

Offline Jasonb

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Re: A Robinson from rejects.
« Reply #169 on: February 05, 2018, 03:28:23 PM »
I've been quite tempted to make a model with a weathered look at some time, Grahams castings would give me a head start ;)

Not sure of I would go with the matt dusty barn fresh look or the wiped over with diesel wet look?

Here is an example of an Economy with the no bling look.

http://www.homemodelenginemachinist.com/showpost.php?p=162489&postcount=47

And a Galloway

http://www.homemodelenginemachinist.com/showpost.php?p=299205&postcount=70

Offline Alyn Foundry

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Re: A Robinson from rejects.
« Reply #170 on: February 05, 2018, 04:21:24 PM »
Good afternoon everyone.

A few will know that my passion from late teens was the preservation of vintage machinery. My second engine was a half Ton Lister “ P “ type of 1919. This engine had been robbed of every last bit of Brass by the scavenging scrappers.

Its preservation back to near original condition meant a lot of parts had to be found, it never happened. The engine being so rare that I was forced into learning how to make patterns and then castings in my backyard. The rest is history....

As I grew older I realised that sometimes an engine looked better in the “ as found “ condition, in fact they sold better as a prospective buyer wanted to do the restoration themselves. A friend of mine used to create the as found look regularly by sullying the paint with old engine oil!

It’s a fact that these full size engines were bought to do work and their condition reflects it.

Attached is a picture of my unrestored Robinson type " XP " the " P " suffix is for Petrol, a very rare engine that was converted to Gas as the special inlet and carburettor were missing. The crank guard doubled as the Magneto bracket.

Cheers Graham.
« Last Edit: February 05, 2018, 04:34:47 PM by Alyn Foundry »

Offline RayW

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Re: A Robinson from rejects.
« Reply #171 on: February 05, 2018, 04:55:41 PM »
I like the finish on the Economy model, but the Galloway looks a bit too "patchwork quilt" to be realistic.
I have always restored engines to show condition but can also see the attraction of leaving them in their working clothes. A dear late friend of mine was very much of the "conserve" rather than "restore" brigade and we had many amusing discussions on the subject. The irony was that he bought a beautifully restored Petter Handyman as a present for his wife and it lived for many years on display in their sitting room without ever being run.

As regards the Robinson, I suppose the correct authentic finish should include a wipe over with a rag soaked in chip fat!
Ray

Offline Jasonb

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Re: A Robinson from rejects.
« Reply #172 on: February 05, 2018, 05:12:19 PM »
As regards the Robinson, I suppose the correct authentic finish should include a wipe over with a rag soaked in chip fat!

It would give it that authentic Chippy smell ;)

Offline Ian j

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Re: A Robinson from rejects.
« Reply #173 on: February 07, 2018, 01:17:23 PM »
A bit more progress on my engine built from bar stock/scrap!/casting

Flywheel ('s):-

The gap on my Myford ML7RB only allows 1 1/2" width in it so I  bolted the flywheel to the table of the milling machine and milled a little off the face of one of the bosses and the face of the rim on the other side this allowed it to fit in the gap and finish just under the 1 1/2" total thickness.
The flywheel on the left is yours Graham and the one on the engine is the one I had cast using yours as the pattern.Key way was cut using my home constructed slotter, just takes a few minutes.
Also remade the valves , turned from SS bar as advised earlier.

Offline crueby

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Re: A Robinson from rejects.
« Reply #174 on: February 07, 2018, 03:07:20 PM »
Thats looking great! That flywheel fits the style very nicely.

Offline RayW

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Re: A Robinson from rejects.
« Reply #175 on: February 07, 2018, 03:28:07 PM »
Looking really good Ian. I still have the flywheel to do. Is the keyway in the flywheel parallel or tapered?

Ray
Ray

Offline Ian j

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Re: A Robinson from rejects.
« Reply #176 on: February 07, 2018, 04:56:56 PM »
Ray. The drawing shows the key way to be 1 in 100 taper ( written on the right hand side just above the 1/2" diam bore dimension on the fly wheel drawing.)
 The weight of the flywheel certainly sorts out any tight spots on the engine :)

Offline Alyn Foundry

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Re: A Robinson from rejects.
« Reply #177 on: February 07, 2018, 05:07:12 PM »

 The weight of the flywheel certainly sorts out any tight spots on the engine :)


Hi Ian.

Very nice! The full scale flywheel weighs over 80 Lbs believe it or not. So you had another made from mine eh? Cunning!!  ;)

Cheers Graham.

Offline Alyn Foundry

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Re: A Robinson from rejects.
« Reply #178 on: February 07, 2018, 07:10:17 PM »
A good apprentice anticipates his bosses needs....

I felt that an introduction to the gas plumbing might be useful at this juncture.

I have attached a picture of my Robinson number 103.

As most will know the original engines ran on " Town gas " lighter than air with a much larger volume needed than what we're going to use with Propane. I learned a little over the years....  ;)

With town gas the mixture for combustion can be very wide but Propane isn't so forgiving it's quite a narrow window.

These engines employ " hot tube " ignition, this means an externally heated hollow tube sealed at one end with the other open to the combustion chamber. In the old days using town gas the tube didn't need to be ridiculously hot so a simple low pressure gas air mixer made a flame that surrounded the ignition tube.

We discovered very early that for the Propane air mix a bright Orange tube was essential to successful ignition. Back in the day Primus were offering a range of beautifully made burners, we opted for the 8842 because it produced a neat pencil point flame. The downside is that they need around 40 PSI of gas pressure to work effectively.

The dilemma is.... Do we have two gas lines to the engine, one low one high pressure? My answer was no!

My solution.... In the picture you can see a " Wade " 3/16" needle valve directly screwed into the inlet valve, there's a good reason for this. A scale engine suffers with a " little does a lot " a tiny tweak of gas makes a huge difference wheras the full size wouldn't notice it so much. What you can't see is that the Copper pipe bringing the gas into the needle valve has had the end plugged with soft solder and then punctured with a fine needle. This doesn't alter the pressure but drastically reduces the flow so there's more control.

I seem to have gone on a bit but if you need more information please don't hesitate to ask, I earned that Tee shirt the hard way!

Cheers Graham.

Offline Jasonb

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Re: A Robinson from rejects.
« Reply #179 on: February 07, 2018, 07:59:21 PM »
Thank's for that graham

Do you use a low pressure regulator on the propane cylinder? Also is there any form of demand valve, I would have thought not as the inlet valve acts much like a demand valve only opening when there is a vacuum in the cylinder.

J

 

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