Author Topic: A Robinson from rejects.  (Read 71930 times)

Online Jasonb

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Re: A Robinson from rejects.
« Reply #225 on: February 21, 2018, 07:46:13 AM »
With a suitably antiqued base casting now sitting in the workshop I had  acloser look at the base drawing. Is it correct that the ctr line of the cylinder does not pass through the ctr line of the crankshaft? I have done other engines where the two are offset as per the original engine such as the Baker Monitors but just wanted to check before cutting metal.

Sketch below shows 1.5" for the vertical face from the top of the slope and then 0.625 in to the crank ctr line. The green line is 1.093 above the sloping face.


Offline Alyn Foundry

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Re: A Robinson from rejects.
« Reply #226 on: February 21, 2018, 11:19:08 AM »
Good morning All.

Yesterday was a long and both sad and happy day, glad to be home.

For Ian, yes that was a “ cold start “ we use a thin wall to the Stainless Steel ignition tube and those little burners are very effective. You get a nice little Orange spot formed on the side.

Please be aware that the flame point has a direct relation to ignition timing, lower down, advanced higher up retarded.

For Jason, I hadn’t noticed that, to be honest! We just machined and then fitted the parts together, it worked! Drew them afterwards....  My advice would be to assemble and see how it works.

Cheers Graham.

Offline ettingtonliam

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Re: A Robinson from rejects.
« Reply #227 on: February 21, 2018, 08:15:25 PM »
Graham
Not strictly from rejects, but definitely Robinson related. A few weeks ago I managed to acquire an unmolested set of castings for the Robinson hot air engine, still I think, in the original packaging. There is one drawing, is that all? I don't quite understand how the displacer piston goes together, what material did you use. I was thinking of thin wall brass tube with sheet brass end pieces, made to be a slack (maybe 30 thou) fit in the hot end cylinder. How hot does that get? Can I use soft solder on that displacer piston?
The other bit I don't understand is what seems to be a governor valve in the end of the cold cylinder. How does that work?

Regards

Richard

Offline Alyn Foundry

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Re: A Robinson from rejects.
« Reply #228 on: February 21, 2018, 08:35:18 PM »
Hello Richard.

Welcome to MEM.   :ThumbsUp:

This thread might be a good place to look for your answers.   ;)

I'll copy, paste and answer there.

http://www.modelenginemaker.com/index.php/topic,7561.0.html

Cheers Graham.


Offline Alyn Foundry

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Re: A Robinson from rejects.
« Reply #229 on: February 22, 2018, 04:48:15 PM »
Robinson mania....

Having effectively ruined my " rejects " thread by letting go of all the castings I had we had to resort to a new one!

Milling the " water base " is a doddle with a big machine.

Cheers Graham.

Online Jasonb

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Re: A Robinson from rejects.
« Reply #230 on: February 22, 2018, 05:05:55 PM »
Looks better than the original rejects and unlike mine I doubt you had any sparks flying while trying to machine the iron, 'twas a bit hard!

Offline Alyn Foundry

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Re: A Robinson from rejects.
« Reply #231 on: February 22, 2018, 05:12:49 PM »
Hi Jason.

I’m really quite shocked....

That base was “ run short “ not quite enough metal to finish the pour properly. I suppose it might have suffered a chill?

Rhuddlan Iron was always a bit tougher than Buckley but I never saw sparks other than when grinding.

Photos soon?

Cheers Graham.

Offline Jo

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Re: A Robinson from rejects.
« Reply #232 on: February 22, 2018, 05:41:12 PM »
Photos soon?

He's hoping that most people don't read what he writes so the longer he does not show any pictures of castings the longer he can pretend he doesn't like working with them  ::)

Jo
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Online Jasonb

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Re: A Robinson from rejects.
« Reply #233 on: February 22, 2018, 06:45:23 PM »
Just pacing myself Jo but just for you.

Think I may ask for some money back as the flywheel did not come with that special coating that I had been looking forward to though I did get a couple of sink holes on the other side thrown in for free.



Base casting only had minimal surface rust but one of the bent hails did come out while doing the initial fettling so will have to plug the hole if I want to avoid a wet patch.



It just so happens that Lidl had their small sand blast guns in the specials this week so thought it was worth a punt for the small outlay, just gave it a very quick try out on the cast writing and it seems to work quite well if a little messy.



I started by shimming up the casting to get it to sit as evenly as possible and took a skim off the top which saw the first sparks start to fly, the dark shiny areas are the hard bits.



With enough flat area to get a good mounting I turned the casting over to do the feet, again rather hard.



With that done I put it back up the right way and took a couple more passes with some new tips in the cutter as the hard spots had taken the edge right off them and got a reasonable finish on the top. (no pic yet)

J


Offline Jo

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Re: A Robinson from rejects.
« Reply #234 on: February 22, 2018, 07:17:08 PM »
Just pacing myself Jo but just for you.

They have been in his hands for less than 48 hours and the swarf is already flying  :lolb:

What happened to the casting fondling  :facepalm:

Jo
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Online Jasonb

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Re: A Robinson from rejects.
« Reply #235 on: February 22, 2018, 07:24:18 PM »

What happened to the casting fondling  :facepalm:


I'll leave that to the girlies :LittleDevil:

Offline Ian j

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Re: A Robinson from rejects.
« Reply #236 on: February 23, 2018, 04:02:46 PM »
OK a cry for help.
First test run a BIG disappointment.After letting the ignition tube get hot for several minutes turning the low pressure gas valve a small amount and spinning the fly wheel I can see the inlet valve flicker open a tiny amount but there's no attempt to ignite the gas which I hear if I hold the valve open. I think I set the exhaust valve timing as in the build instructions but on the intake stroke the exhaust valve is open only closing just before BDC.
If I remove the exhaust and inlet valve chests I can feel compression with a finger over the ports, I ground in the inlet valve which seems a good seal.The ignition tube is drilled out with a No. 11 drill, the low pressure valve inlet is via a No. 60 drill.  :(
« Last Edit: February 23, 2018, 04:40:14 PM by Ian j »

Offline Alyn Foundry

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Re: A Robinson from rejects.
« Reply #237 on: February 23, 2018, 04:49:17 PM »
Hi Ian.

Not to worry, this IS the 21st century after all.

Do you have Skype? We could work through this together.

Cheers Graham.

Offline Ian j

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Re: A Robinson from rejects.
« Reply #238 on: February 23, 2018, 05:35:30 PM »
Thank's for that Graham.
I have skype but never used it, I would have to get up to speed with it or we would get side tracked sorting skype out :)
I'm getting gas into the cylinder because I can ignite it at the exhaust  port on the exhaust stroke. When would you expect the exhaust valve to be shut on the intake stroke?

Offline Alyn Foundry

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Re: A Robinson from rejects.
« Reply #239 on: February 23, 2018, 05:47:20 PM »
Hi Ian.

I’ve been using Skype for years it works really well particularly if you have a hand held device like a phone or tablet.

I’ll PM my ID to you.

The exhaust can start opening anytime after 20 past the hour but must close at TDC, that’s the important part.

A simple test can be done by lighting the seepage past the inlet valve if you get a Yellow flame higher than say 2 inches, way too much gas is available. You’re looking for about an inch with everything stationary.

Cheers Graham.

 

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