Author Topic: Wrestling with Robbo........  (Read 16420 times)

Offline Stilldrillin

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Wrestling with Robbo........
« on: June 06, 2012, 02:11:22 PM »
The original posting of this year's initial rebuilds, got a little lost, among the offers of auction lots.
So, I've reconstituted the Robbo postings.........


Time to start on Robbo......

You've all seen the story, up to pres.......... 
                       
                                                          http://madmodder.net/index.php?topic=6110.0

First off. I don't like relatively thick wall, brass hot caps........




Too much heat can pass to the cool end.
So, I sawed it off, to replace with a piece of steel vacuum cleaner pipe......




I noticed the original end cap was concave copper, and painted black, to absorb the heat.
A rub with emery highlighted the hammer marks........




I radiused a piece of delrin, and gave it a tap, or two........




Looks good now........




Carefully parted off, just behind the cap........




Bored the cool end 1/8" deep to take the chrome pipe, and cap.
Looks ok, I think.........




I emeried away the chrome, and silver soldered the cylinder in place........




Then after a clean up, replaced the original copper cap......




Another clean, and a quick assemble. I think they look made for each other......




Not a bad day's work.......




Need to sort out how to make a lightweight displacer now, cos I don't like the wasted volume of the regenerator.

It's nice to be back to it again!  :D

David D
« Last Edit: June 28, 2012, 12:40:11 PM by Stilldrillin »
David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Offline Stilldrillin

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Re: Wrestling with Robbo........
« Reply #1 on: June 06, 2012, 02:14:49 PM »
Having now had the time to examine what I'd achieved with the hot cap. I was feeling very pleased with meself.  :D

I had only ever silver soldered two small joints before.
It just goes to show, if enough notice is taken of techniques shown on here, the beginner can produce some very satisfactory work.  :thumbup:

Displacer time!
The cap bore is 1.4". I cut some steel sheet .020" thick, and wrapped it around a 32mm ali bar.
Ground the inner overlap to a feather edge, and strapped it tight.




Then turned the outer feather edge. Moving the pipe clip section by section.......




Swapped the clip for some stout wire, and fluxed........




Then silver soldered........




Just a nice line showing in the bore........




Cleaned up nicely.........




I think that will do nicely........




A busy few days ahead, including Harrogate. End caps next. As, and when.......

Thanks for watching!  :)

David D
David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Offline DaveH

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Re: Wrestling with Robbo........
« Reply #2 on: June 06, 2012, 02:30:55 PM »
David,

Well that has turned out very nice  :bow:

Great job  :thumbup: :clap:
 :beer:
DaveH
 
(Ex Leicester, Thurmaston, Ashby De La Zouch.)

Offline Stilldrillin

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Re: Wrestling with Robbo........
« Reply #3 on: June 06, 2012, 02:54:27 PM »
Thanks Dave.

My first proper session of metal forming, and silver soldering, went very well.......  :D

David D
David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Offline Stilldrillin

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Re: Wrestling with Robbo........
« Reply #4 on: June 06, 2012, 03:50:24 PM »
Time for the displacer end caps.

I used the original piece of delrin to dish a piece of steel sheet.

Then used it with a piece of emery cloth, as friction drive to turn to a sliding fit in the displacer tube.....




And silver soldered it into place........




Quick clean up.........




I turned an ali top cap. A push fit x 10mm thick.

Just for those who love to see swarf.........




I milled away some of the weight. Leaving a bridge, for an M3 grubscrew, to lock onto the screwed shaft......




The original displacer shaft bush was made of two opposing gland nuts, with an O ring in between. Didn't like that idea.
Locktited the glands in place. Drilled out and re bushed at 4mm dia.




Then milled away the hex head under the deck, for even less dead space.........




Next job was to temporarily re-assemble and give it a try. Dunno why the little end is so noisy.......




Hmmmm........  :bang:

Time for another think, I think.

David D

« Last Edit: August 15, 2016, 03:19:18 PM by Stilldrillin »
David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Offline Stilldrillin

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Re: Wrestling with Robbo........
« Reply #5 on: June 07, 2012, 08:12:15 AM »
Well..... I've done all I can to improve the existing parts.
It is so close to running! And very much improved, over the lifeless lump I first tried.

I've had a good think, and a measure round........
I read, somewhere, the displacer volume needs to be around 1.6 times, (or more), the power piston volume.

The displacer measures 1.32" dia x .45" stroke. The power piston measures 1.018" dia x .73" stroke. Giving a ratio of only 1.037.... Hmmm....

If I reduce the power piston dia. to .8"...... This will give a ratio of 1.68....... If my sums are correct.

Anyone got a comment? Or two pennorth?

David D




David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Offline sbwhart

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Re: Wrestling with Robbo........
« Reply #6 on: June 07, 2012, 10:40:51 AM »
Just checked the calc through using my long winded way and I get .796 so .8 is the man to go.

 :D :D

Stew
A little bit of clearance never got in the road
 :wave:

Location:- Crewe Cheshire

Offline OldMetaller

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Re: Wrestling with Robbo........
« Reply #7 on: June 10, 2012, 04:05:33 AM »
Nice work David!  I could see some Old Machinist's tricks being wheeled out there!  I especially like the Delrin dodge!

Regards,

John.

Offline Stilldrillin

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Re: Wrestling with Robbo........
« Reply #8 on: June 12, 2012, 01:27:21 PM »
Thanks for your comments Chaps!

I found the advised ratio is 1.5....... So, I made the steel cylinder with a bore, around .843".

Stuck it into the original cylinder, using high temp slide lock. Then honed it, using a piece of delrin, and fine grinding paste........




All done.......




Turned the piston to +10 thou' , and parted off.......




Screwed onto an M5 threaded mandrel, and finish turned.

Removing the last thou' or so with fine emery, backed by a 6" rule, a la Cedge.........




Looks ok, I think.........




Lit the burner......
So sorry for the amateur dramatics! But....... You know how it is..........




It's been a good day!   :D :) :D :)

David D
« Last Edit: June 15, 2012, 01:30:38 AM by Stilldrillin »
David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Rob.Wilson

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Re: Wrestling with Robbo........
« Reply #9 on: June 12, 2012, 01:38:07 PM »
 :clap: :clap: :clap:  :clap: :clap:  She goes like the clappers David   :clap: :clap: :clap:  :clap:

I always fined your "bring em back to life" threads a great read ,,,,,,,,,,, well done  :thumbup:



Rob

Offline Bluechip

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Re: Wrestling with Robbo........
« Reply #10 on: June 12, 2012, 03:13:21 PM »
As the Venerable Foggy would say ...

WELL DONE, THAT MAN

 :thumbup:

BC
I have a few modest talents. Knowing what I'm doing isn't one of them.

Offline krv3000

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Re: Wrestling with Robbo........
« Reply #11 on: June 12, 2012, 03:24:27 PM »
well dun from me to

Offline sbwhart

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Re: Wrestling with Robbo........
« Reply #12 on: June 12, 2012, 03:38:17 PM »
That will certainly do 

:nrocks: :nrocks: :nrocks: :nrocks: :nrocks: :nrocks:


 :clap: :clap: :clap: :clap: :clap: :clap: :clap:

Well done Dave I knew you'd tame it  :whip:

Stew
A little bit of clearance never got in the road
 :wave:

Location:- Crewe Cheshire

Offline Stilldrillin

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Re: Wrestling with Robbo........
« Reply #13 on: June 12, 2012, 03:59:30 PM »
Thanks for your kind replies Chaps!  :thumbup:

Only cobbled together, to prove, or not!
Now needing proper assembly, with gaskets, and the big & little end bearing fits sorting out.

Innit a great feeling, when an engine finally comes to life!!  :D  :D

Stillgrinnin.  :)
David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Offline millwright

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Re: Wrestling with Robbo........
« Reply #14 on: June 12, 2012, 04:41:27 PM »
Well done David,
 another one ressurected and running well :beer:
John

Offline AussieJimG

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Re: Wrestling with Robbo........
« Reply #15 on: June 14, 2012, 01:33:08 AM »
Looking good, sounding good and running well. Congratulations David, on another job well done.  :nrocks:
Jim

Offline stirling lad

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Re: Wrestling with Robbo........
« Reply #16 on: June 14, 2012, 08:54:24 PM »
brilliant !! blooming brilliant,you clever ole fox... :smart: :clap:

...Mike...

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Re: Wrestling with Robbo........
« Reply #17 on: June 29, 2012, 02:28:21 AM »
Thanks for all your support, Lads!  :thumbup:
It's much appreciated, when the hobby seems to be wading through treacle, and life is getting in the way..........  :(


This engine appears to have had two builders, before me. The first has done a really good job of details.

The linkage system fit and finish, is first class.......




The second builder has botched a few points.

The cross pins measure up at around .106"/ 2.7mm.......  :scratch:

The original displacer shaft has an 1/8" hole........




The gudgeon pin was an 8BA screw, only locating in it's threaded hole. Not touching the other bearing areas.......




So, I drilled through at 2.7mm........




And made a 1/8" headed pin, to suit.......




I hate to see wobbobly flywheels. This one had most of it's sections eccentric too!

I trued both bosses, and the inner rim. Opened up the bore, plugged and re-drilled to 6mm.

The eccentric spokes area, I left as is. A balancing feature..........




The wick end of the burner locates in a central hole. Under the hot cap. Leaving the tank end to pendulum from side to side.

So, I fitted a 10 x 2mm magnet in it's base........




And one in the oak base........




Underneath the brass base. Made a new knurled filler cap too.........




Put on your sunglasses............




After a some time. The revs had climbed much too high for me. I like to see the wheels go around.

So, I trimmed the wick back as far as it would go. It runs around 150rpm now........




HAPPY!!!  :)

Defor.




David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Offline stirling lad

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Re: Wrestling with Robbo........
« Reply #18 on: June 29, 2012, 09:39:43 AM »
another excellent rescue David, and its looking really smart after a wee polish too.
thanks for another ecucational thread.. :thumbup:

  ...Mike...

Offline NickG

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Re: Wrestling with Robbo........
« Reply #19 on: July 21, 2012, 01:34:04 PM »
It's a beauty now! Nice 1 David!  :thumbup:
Location: County Durham (North East England)

Offline Stilldrillin

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Re: Wrestling with Robbo........
« Reply #20 on: July 21, 2012, 04:02:58 PM »
Mike, Nick.
Thank you!  :thumbup:

It's now had a couple of hours running happily, around 20mins at a time.

When it stops, the residual heat creeps into the cylinder, nipping the brass piston in the steel bore.
I think that could be called an accurate fit...... I'm astounded!  :bugeye:

And pleased!  :)

David D
David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Rob.Wilson

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Re: Wrestling with Robbo........
« Reply #21 on: July 21, 2012, 05:15:02 PM »
I think "jobs a good un " too David  :bow: :bow: :bow: :bow: :bow:

Sure is a smooth runner , a testament to your ability as a machinist  :clap: :clap: :clap:


Rob 

Offline Dean W

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Re: Wrestling with Robbo........
« Reply #22 on: July 21, 2012, 05:36:03 PM »
Could have sworn I had commented on this before.  Guess I'm going crazy, again..
Well, it surly is a "goodun", David.  It's absolutely beautiful in all respects, and runs
like an American watch!  (We made really good watches!)  : )
Thanks for the excellent video!
Dean W.

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Offline saw

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Re: Wrestling with Robbo........
« Reply #23 on: July 21, 2012, 05:37:27 PM »
Nice work  :thumbup: :thumbup: :thumbup:
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Offline doubleboost

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Re: Wrestling with Robbo........
« Reply #24 on: July 21, 2012, 05:39:53 PM »
Hi
David
Just read this post
Cracking job you have made of it :clap: :clap: :clap:
Like you said some bits were very well made , others not so good :Doh: :Doh:
It will be around for a long time now :) :)
John

Offline Stilldrillin

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Re: Wrestling with Robbo........
« Reply #25 on: July 23, 2012, 02:24:44 AM »
I think "jobs a good un " too David  :bow: :bow: :bow: :bow: :bow:

Sure is a smooth runner , a testament to your ability as a machinist  :clap: :clap: :clap:
Rob

Thanks for that Rob!

But, I just wish I could get it as shiny as your machining.........  :thumbup:  :D


Could have sworn I had commented on this before.  Guess I'm going crazy, again..
Well, it surly is a "goodun", David.  It's absolutely beautiful in all respects, and runs
like an American watch!  (We made really good watches!)  : )
Thanks for the excellent video!

Dean.
You're definitely not going crazy. The original posting got rather lost, in the charity donation offers. So, I re posted.......
Unfortunately, your post was left behind.  :palm:   So sorry. Please forgive me?

Thanks for your comparison to top quality instruments. I do my best. Sometimes, I get a good outcome........  :)



Nice work  :thumbup: :thumbup: :thumbup:

Thank you, Benni!




Hi
David
Just read this post
Cracking job you have made of it :clap: :clap: :clap:
Like you said some bits were very well made , others not so good :Doh: :Doh:
It will be around for a long time now :) :)
John

Thank you, John.

With luck, it will be running, long after I've stopped....... Hobbling!  :lol:

David D
David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!