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Author Topic: Robinson Hot Air Engine.  (Read 126827 times)

Offline Stilldrillin

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Re: Robinson Hot Air Engine.
« Reply #75 on: November 20, 2010, 01:02:55 PM »
Thanks for your ideas/ suggestions, Jack.  :thumbup:
But I think I'll leave the displacer thoughts, until this present section's sorted........  ::)

Finished roughing, at .005" per pass......




I'm going to face off the 6BA threads, down to below the level of the part thread.....




I'll then reduce the dia of the o/d by .1" per side, right through to the neck.
Then counterbore the new piece, to replace the o/d, and machine a larger flange.....




The original flange is a bit small. Doesn't seal well on the 1/16" cover plate.
Making new 3mm plate with recess for flange, to replace......




Unless anyone else has a better idea?  :wave:

David D



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Offline shoey51

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Re: Robinson Hot Air Engine.
« Reply #76 on: November 20, 2010, 01:23:11 PM »
david looks good to me just watching on the side lines :thumbup:
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Offline Reckless_Engineer

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Re: Robinson Hot Air Engine.
« Reply #77 on: November 20, 2010, 05:44:32 PM »
A Top job so far david! This thread may come in handy whilst trying to convince the other half the pile of random metalic objects i have could come in handy one day  :clap:
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Offline Dean W

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Re: Robinson Hot Air Engine.
« Reply #78 on: November 20, 2010, 06:09:02 PM »
Now I get it, David.  Wasn't sure I understood when you first started on that piece of CI.  Makes sense,
and I think it will work as you are hoping. 
For that displacer, do you mean the can part itself?  I would use aluminum for that.  Make it as thin walled
and light as you are able.  Less mass going up and down will do nothing but help the situation.

Dean
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Offline Stilldrillin

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Re: Robinson Hot Air Engine.
« Reply #79 on: November 21, 2010, 04:08:14 AM »
Graham, Tom, thanks!  :thumbup:

Dean, Isn't aluminium too conductive? Isn't steel better?  :scratch:

Read somewhere, someone's used balsa wood......


Looking around the still uncleaned casting.

The hole for the air tube is quite generous.......




Looking on t'other end, not much material left.

Err...... Wossat? ...... In't back corner?




Gave it a poke and a proddle.




Guess this is the source of the leak.......  :doh:




SIGH......... Again........

Wonder if this is the last of the glitches? ....... Nah.... Doubt it! :bang: :bang:

David D
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Offline shoey51

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Re: Robinson Hot Air Engine.
« Reply #80 on: November 21, 2010, 04:41:14 AM »
looks nasty David but im sure you can handle it :thumbup:
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Offline NickG

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Re: Robinson Hot Air Engine.
« Reply #81 on: November 21, 2010, 07:32:58 AM »
I used aluminium for my displacer David, think it's pretty standard to have a hollow aluminium displacer with a very thin wall - same as hot cap to minimise heat transfer.

Good work.

Nick
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Offline sbwhart

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Re: Robinson Hot Air Engine.
« Reply #82 on: November 21, 2010, 11:34:02 AM »
Quote from: Stilldrillin on November 21, 2010, 04:08:14 AM


Looking around the still uncleaned casting.

T
Err...... Wossat? ...... In't back corner?




Gave it a poke and a proddle.




Guess this is the source of the leak.......  :doh:




SIGH......... Again........

Wonder if this is the last of the glitches? ....... Nah.... Doubt it! :bang: :bang:

David D



TERMITES ?


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Offline Stilldrillin

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Re: Robinson Hot Air Engine.
« Reply #83 on: November 21, 2010, 12:02:46 PM »
Quote from: sbwhart on November 21, 2010, 11:34:02 AM

TERMITES ?


 :lol: :lol: :lol: :clap:

Could be, Stew!  :thumbup:

I'm wondering what else could be lurking.......  ::)

Just keep calm, and carry on!

David D
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Offline Bogstandard

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Re: Robinson Hot Air Engine.
« Reply #84 on: November 21, 2010, 01:25:38 PM »
If you can Dave, get the whole inside surface sand blasted. Any little pockets of weakness like that will soon show up.

Then a bit of JB Weld or even soft solder will take care of it, just make sure you neutralise the flux afterwards.


John
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Offline Stilldrillin

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Re: Robinson Hot Air Engine.
« Reply #85 on: November 21, 2010, 03:43:14 PM »
Quote from: bogstandard on November 21, 2010, 01:25:38 PM
If you can Dave, get the whole inside surface sand blasted. Any little pockets of weakness like that will soon show up.

Then a bit of JB Weld or even soft solder will take care of it, just make sure you neutralise the flux afterwards.


John

Thanks for that John!  :thumbup:

Because of the very thin wall, in places. I have ordered some 5/16" brass tube with .014" wall thickness. Intending to fix with sleeve lock.

This will leave a smooth bore for the air tube, with O rings, mebbe!

David D
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Offline Bogstandard

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Re: Robinson Hot Air Engine.
« Reply #86 on: November 21, 2010, 04:19:21 PM »
I never considered that Dave.

That should do just as well.


John
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Offline Dean W

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Re: Robinson Hot Air Engine.
« Reply #87 on: November 21, 2010, 05:04:30 PM »
Quite a lot of stirlings use aluminum for the displacer can.  It may be a trade-off between a dead weight you have to pick straight up,
and a bit of heat transfer.  On this design, the heat transfer should not be a big concern, since the power piston and displacer can are
not directly connected.  I.E., when the can gets hot, it will not be putting heat into the cold end, as it would on the type that has both the
power piston and displacer can in a common bore.  Did I put that in a way that it makes sense?

Dean
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Offline Stilldrillin

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Re: Robinson Hot Air Engine.
« Reply #88 on: November 22, 2010, 02:03:46 AM »
I can understand your reasoning Dean.  :thumbup:

Though this type of engine has problems, as the heat is directly underneath the skirt, with no easy exit.

I intend to fit a copper pipe chimney, as I have seen on others. This looks better than several radialy drilled holes, or slots.

I fitted 2 insulating gaskets, made from exhaust manifold cardboard/ metal material, either side of the hot cap flange. (The white line above the skirt).

Anyone got a better idea?




David D
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Offline madjackghengis

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Re: Robinson Hot Air Engine.
« Reply #89 on: November 22, 2010, 10:31:24 AM »
Well David, from where I sit, it looks like you've got everything well under control.  I didn't mean to assume control of your project with regard to displacers, everything in hot air engines is a matter of trade off, and weight is equally a factor.  The main thing is plugging up all the leaks, which you've had to dig to find, and putting on a chimney is certainly a good idea, and will move lots of excess waste heat out of the way.  From the way it ran with all the problems, it ought to be a real powerhouse, now that everything is done up right, and patched up right nice and tidy.  That is an engine I'd keep in the living room, even if it did cause a bit of "discussion" between me and the Mrs.  I'm looking forward to the video when you're ready to run the engine, you've definitely done your share of the "building" of it, even if it was sort of together, when you got it.  I think your fix of the displacer chamber will be just what the doctor ordered. :beer:  cheers, mad jack
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Offline Stilldrillin

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Re: Robinson Hot Air Engine.
« Reply #90 on: November 22, 2010, 11:49:06 AM »
Thanks for that Jack!  :thumbup:



Did you get my PM, t'other day?.......  :scratch:

David D
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Offline madjackghengis

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Re: Robinson Hot Air Engine.
« Reply #91 on: November 23, 2010, 08:22:48 AM »
Hi David, I did just look at your p.m., forgot they exist, truthfully,  I think the model engineering kind of faded quite a bit for a while, and lots of what was available was pretty shoddy manufacture, but it seems to have picked up some, and there are lots of good quality casting kits out now, so hopefully we can look forward to better beginnings as we move forward.  I suspect your kit was one with too many flaws for someone who wasn't ready to find them all, and have a ready fix for them.  I always think such things are the best way to get a nice project at a cheap price, and pay up in work, to make up for to price.  Personally, I don't mind, I'd rather be in the shop anyway.  I'm looking forward to seeing how you set up your chimney, I think it'll make a big difference in the long run. :beer: :thumbup: mad jack
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Offline Stilldrillin

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Re: Robinson Hot Air Engine.
« Reply #92 on: November 25, 2010, 04:02:14 PM »
Well, the worst of the roughing is finally finished!

Sawed/ machined away the air tube, part thread. Also the flange......




Then counterbored the new portion......




We've got a new member in the inspection department

She's learning, slowly......




Hmmmm......




Tried for fit.......




Passed, ready for assembly.....




Now assembled, with high temp sleeve lock. Final machining, later.  :thumbup:

David D
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Offline shoey51

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Re: Robinson Hot Air Engine.
« Reply #93 on: November 25, 2010, 04:16:29 PM »
nicely done David and a young machinist in the making :clap: :thumbup:
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Offline Bogstandard

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Re: Robinson Hot Air Engine.
« Reply #94 on: November 25, 2010, 08:17:46 PM »
David,

The only problem with using inspectors of such a young age is having to polish out the teethmarks afterwards.


John
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Offline Dean W

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Re: Robinson Hot Air Engine.
« Reply #95 on: November 25, 2010, 09:43:13 PM »
She looks like a very influence-able inspector to me, David.  I'm betting she could be bribed with a sweet biccy.
I know I can.  ; )
She's quite a doll!
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Offline sbwhart

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Re: Robinson Hot Air Engine.
« Reply #96 on: November 26, 2010, 02:32:36 AM »
That the way to go Dave start them young.

Nice picture, thats one for the album

 :thumbup: :thumbup: :thumbup:

My grandson is fascinated with wheels that turn, he sits on my knee at my computer desk happily turning my finger engine over and over its lost it polish with the sticky fingers,

Bin thinking of making him a wooden one for Christmas  :proj:

Stew
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Offline Stilldrillin

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Re: Robinson Hot Air Engine.
« Reply #97 on: November 26, 2010, 03:16:53 AM »
Quote from: sbwhart on November 26, 2010, 02:32:36 AM

My grandson is fascinated with wheels that turn, he sits on my knee at my computer desk happily turning my finger engine over and over its lost it polish with the sticky fingers,

Bin thinking of making him a wooden one for Christmas  :proj:

Stew

Now, that's a great idea Stew!  :clap:

Something robust. For little hand, not finger, but not needing muscles to operate. Hmmm......  :thumbup:

David D
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Offline NickG

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Re: Robinson Hot Air Engine.
« Reply #98 on: November 26, 2010, 03:37:55 AM »
I always think it's a lovely idea to make people things for christmas - trouble is, I'd need to start in January if this idea is to work!  :lol:

Nice work David, have you thought of driving anything with this when the improvements are complete? I think it'll be powerful enough and with a convection water cooler it should run for a while.

Nick
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Offline Stilldrillin

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Re: Robinson Hot Air Engine.
« Reply #99 on: November 26, 2010, 03:58:17 AM »
Quote from: NickG on November 26, 2010, 03:37:55 AM
I always think it's a lovely idea to make people things for christmas - trouble is, I'd need to start in January if this idea is to work!  :lol:

Nice work David, have you thought of driving anything with this when the improvements are complete? I think it'll be powerful enough and with a convection water cooler it should run for a while.

Nick

Nick,
I arrived here via the Steamtoys forum. Been watching wheels go round for several years..... Never driven anything!  ::)

Once things are running to my satisfaction, I seem to move on to another engine.......

I often have vague thoughts of making a water pump..... Then another orphan arrives, needing my attention!  :thumbup:

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

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