Author Topic: Rene Schaffer's HR-25  (Read 5303 times)

Offline Bluechip

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Rene Schaffer's HR-25
« on: August 16, 2017, 11:37:22 AM »
Some time ago I started a Stirling Engine based on Rene Schaffer's HR-25, a design published in Heissluftmotoren X.
A vague reference here:   http://www.modelenginemaker.com/index.php/topic,2748.msg51573.html#msg51573
Now having got some sort of shop in action, and with regard to some chidings re: lack of swarf from a certain quarter, I have raked out the box containing it's 
bits.
Which is where the trouble started ...  :(  there being a whole heap of other stuff in there.  :facepalm2:
Chucked out all the bits that were obviously nothing to do with the HR-25 I landed up with the stuff in pic. 1.
..... And did a rough trial assembly to see how far I had ( n't ) got.  pic. 2
Now, it is based around the test tube which is larger than the original design so the thing as a whole is larger.
It follows that the geometry is not the same.
So I re-drew it to suit.
But I've no idea on which of my PC's the revised dimensions are ( if any ) .
Need to start again I think.


Dave

EDIT  This refers, I think. Rene's site:

http://www.modellschaffer.ch/index.htm?shop.htm

Click Gallerie, several versions there.



« Last Edit: August 16, 2017, 11:48:55 AM by Bluechip »

Offline Ian S C

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Re: Rene Schaffer's HR-25
« Reply #1 on: August 16, 2017, 01:22:08 PM »
If you do go to a bigger diameter test tube for the hot end, it would probably be best to reduce it's stroke to maintain the ratio of about 1.5 : 1 between it and the power piston /cylinder volume. The other way (probably the best) is to bore out the power cylinder, and make a new piston.  These V type GAMMA motors are as simple as you can get, only requiring the single crank pin directly coupled to each cylinder.
Get every thing running with minimum friction and leaks, a well fitting power piston in a smooth bore, and you should have a good looking engine that runs in fairly short order.
Ian S C
« Last Edit: August 16, 2017, 01:32:32 PM by Ian S C »

Offline Bluechip

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Re: Rene Schaffer's HR-25
« Reply #2 on: August 16, 2017, 04:06:34 PM »
Ian:

I have a lot of 24mm OD tubes so that's what I'll use.     ;D

OK I've found the drawing I made, very scruffy, so I'll just give the numbers.

The crank throw is 24mm, this drives the end of the rocking lever at a radius of 125mm. At 85mm radius there is the drive to the displacer so we have a displacer stroke of 24 x ( 85 / 125 ) = 16.3mm ( or near, it's an arc so it will be a bit shy but not significant for this argument )
The test tube bore is circa 22mm and the displacer is 20.2mm dia. ( I can skim a bit off that, there is enough meat on the ally tube wall ).
So, cranking that around I get 5224 cu. mm displacer swept volume.
The power cylinder needs to be about 1 / 1.5 of that figure nominal as Ian says which gives 3482 cu. mm.
We are stuck with a stroke of 24mm which gives a power cylinder bore of about 13mm. ( No, it doesn't . But I have got a 13mm reamer .  :)  ). It makes the ratio a bit more, but it's on the right side I think.

So, as a first approximation, that's what it'll be.

BOOM         Swarf time  ....

Dave



« Last Edit: August 16, 2017, 04:11:52 PM by Bluechip »

Offline Bluechip

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Re: Rene Schaffer's HR-25
« Reply #3 on: August 18, 2017, 10:18:06 AM »
Grrrrrrrr.

Made a bit of progress last night, but not a lot.
I decided that it would be a good idea to make the 5mm dia. Stainless Steel pins that hold the linkages together.
Made a 1/32" wide grooving tool, very laborious and fraught with peril, but I succeeded. Just off-hand grinding, not very good at it.
Two grooves for e-clips were made ..  and then ... PING!
The tool perishes.  :Mad:
I suspect that 5mm SS is 316 which I don't find to be very tractable.

Sat down with a Becky and wracked my brain cells. ( When I got to 00FFh I went round them again :thinking: ).
Years ago I did a lot of these e-clip grooves no bother.
Then I remembered.
Use a slitting saw. ( And find some 304 SS ! )

 :whoohoo:    Success

Att. are a couple of scratty pics. to show the idea in case anyone is interested.

Dave







« Last Edit: August 18, 2017, 11:54:43 AM by Bluechip »

Offline Ian S C

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Re: Rene Schaffer's HR-25
« Reply #4 on: August 18, 2017, 10:48:36 AM »
Hi Dave, the ratio doesn't have to be too exact.
I,v use 316 to make hot caps for Stirling Engines, my metal supplier didn't have any 304 at the time, so he gave me a discount on the 316 and said as I went out of the store, "you'll be pushing your luck with that".  It wasn't too bad except for strings of swafe miles long. It's important to keep the tool cutting, and don't let it rub.
Ian S C

Offline Bluechip

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Re: Rene Schaffer's HR-25
« Reply #5 on: August 18, 2017, 12:22:37 PM »
Hi Ian

I think shrinking the power cylinder is better than upping it, we'll see.

Never have much luck with 316, as you say, horribly stringy. I think that's why the grooving tool went pop. Only 0.7mm-ish wide cut, if it doesn't clear it's going to let go.  As, indeed, it did     :cussing: . Yes, I did use RTD on the SS.

Ah well, sorted anyway   :D Onward & Upward

Dave


Offline Bluechip

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Re: Rene Schaffer's HR-25
« Reply #6 on: August 28, 2017, 02:18:58 PM »
Done a bit more, not much though ...  :)

Rounded off the linkage ends, made the power piston & cylinder and sorted out the geometry somewhat.

Anyway, now 30oC in the shop so that's it for now. Power cylinder is not screwed down  :ThumbsUp:

Power piston is brass with a Graphite sleeve stuck on with Truloc 271. I doubt if it's going to run all that hot .... otherwise, do it over ..  :Doh:

Power cylinder is brass tube in ally.

Couple of pics:

Dave
« Last Edit: August 28, 2017, 02:23:19 PM by Bluechip »

Online Jo

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Re: Rene Schaffer's HR-25
« Reply #7 on: August 28, 2017, 03:23:28 PM »
8) You will have to bring it along when you visit next (and any other engines you have made  :embarassed: )

Forgot to ask: Where do you get that graphite stuff from to make pistons out of? I thought of making another Stirling (lets not talk about the first one  :ShakeHead: ) .... a coffee cup engine would have been nice but they are now available commercially for next to nothing  :-\

Jo
Enjoyment is more important than achievement.

Offline Bluechip

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Re: Rene Schaffer's HR-25
« Reply #8 on: August 28, 2017, 03:40:00 PM »
Looking @ Sunday if that's OK ??  Give the new Forester a neck-wringing .... Get that Saturday Sept. 2

Could do with recovering the space currently occupied by:

(1) Your Onions
(2) Ditto Firewood
(3) Ditto Tool cabinet
(4) Ditto Insulation Bubbly Stuff
(5) Ditto Box of Odds & Sods

Noggin End for Graphite  ... not cheap ..
https://www.nogginend.com/product/Graphite-Round-Bar
Wreak havoc with your moths ...  :'(

The only other engine I made and kept is the Elmers Fancy from about Sept. 2015 ..
http://www.modelenginemaker.com/index.php/topic,5176.msg98927.html#msg98927

Made two or three other Stirlings over the years that ran but died and got dumped. Rather ugly anyway. Just messing about.
There WAS a video of one on PB but the buggers lost it when they 'improved' the site about 2-3 yrs ago. A lot of my stuff just went.
PB said 'Deleted or moved by owner' or whatever.
NO, I DAMN WELL DIDN'T, you did.  :Mad:
Unfortunately I kept no other copy.

Dave


« Last Edit: August 28, 2017, 03:49:08 PM by Bluechip »

Online Jo

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Re: Rene Schaffer's HR-25
« Reply #9 on: August 28, 2017, 03:55:51 PM »
Sunday is good, be nice to see the new wheels and you can meet the latest addition to the family "Sweep", you might like him :naughty:

Does the box of Odd Sods include those electrical cable glands, I could do with one on the Hegner where I added that foot switch. :) And you wouldn't have a electrical knob would you for a 5mm shaft? I broken the plastic top on the compressor shut off valve  :facepalm2:

Thanks for that Noggins... I might see them at the Midlands (assuming I am well enough to travel by then  :-\ )

Jo
Enjoyment is more important than achievement.

Offline Bluechip

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Re: Rene Schaffer's HR-25
« Reply #10 on: August 28, 2017, 04:23:59 PM »
What sort of glands, I gave you some Stuffing Glands ...  :thinking:

I've dumped some 20mm Flex Conduit & Glands for same in there.

SOMEWHERE    :headscratch:  :headscratch: I have some fairly hefty black control knobs that came off line printers but they certainly won't have a 5mm fitting, probably 1/4". AFAIK Apart from small knobs that push on to a serrated & split shaft, they're either 1/4" or 6mm.

When I've done slurping my medicinal Becky I'll have a shufti in the roof space.  Hot here today ....

Wot's Sweep ?? If it's a dog I will certainly like him, but I'll bet it's another machine been Christened ...  :cartwheel:

Dave 

 :'( Can't find them ... maybe they've been dumped. Have found some collet knobs but they're for 1/4" shafts. IIRC they don't even go down to 6mm ...  :headscratch:
« Last Edit: August 28, 2017, 05:22:48 PM by Bluechip »

Offline DEVITG

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Re: Rene Schaffer's HR-25
« Reply #11 on: September 04, 2017, 07:19:58 PM »
My first post , I´m not a so beautiful thing builder , but I love watch as you work .
Reading this thread I notice it about machining SS

Quote
It's important to keep the tool cutting, and don't let it rub.
 

I work with SS , the best cut mean is  PORK´s LARD , the same you can get at the grocery , or just melting PORK GREASE , pick up the not melted part , usually meat rest and the grease solids,  let the rest to be solid at the fridge, then you apply it to the tool and piece.
In my country we call the solid part "chicharrón" , it is tasty , and used to add to bread before oven it.
https://es.wikipedia.org/wiki/Chicharr%C3%B3n

Apologize for my English.

Offline Bluechip

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Re: Rene Schaffer's HR-25
« Reply #12 on: September 04, 2017, 07:53:32 PM »
Hi DEVITG

I've never heard of lard being used for turning stainless steel but it's quite plausible. When I was at work we often used Tallow for screw-cutting steel electrical conduit so why not lard on stainless. Lard is commonly available so I will try it if I remember.  :ThumbsUp:

Just done a bit more to this thing. A couple of short ( mercifully ) videos.
One is the fit of the power piston, got a good fit then decided to just relieve it a little bit more, easy to do. Happy with it now.
I think I have the geometry somewhere near now. It's not as stiff as it seems but I suspect that phosphor-bronze flywheel is rather too heavy.
The main shaft is 12mm Stainless running in dry brass bushes, which is why it doesn't do many revs. There don't appear to be any tight spots anyway.
I'm going to continue as is. If it runs I will make an aluminium flywheel on a 8mm shaft and use ball-races. The OD of the brass bushes were sized to suit.


<a href="https://www.youtube.com/watch?v=SkOQhkn47rg" target="_blank">http://www.youtube.com/watch?v=SkOQhkn47rg</a>

<a href="https://www.youtube.com/watch?v=aOENFOIvOh8" target="_blank">http://www.youtube.com/watch?v=aOENFOIvOh8</a>

Dave



« Last Edit: September 04, 2017, 08:00:07 PM by Bluechip »

Offline Bluechip

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Re: Rene Schaffer's HR-25
« Reply #13 on: September 05, 2017, 09:56:48 AM »



There WAS a video of one on PB but the buggers lost it when they 'improved' the site about 2-3 yrs ago. A lot of my stuff just went.
PB said 'Deleted or moved by owner' or whatever.
NO, I DAMN WELL DIDN'T, you did.  :Mad:
Unfortunately I kept no other copy.

Dave

 :whoohoo:

I did keep a copy ... whilst ferreting about in the dark recesses of my drawers ( what a hero )  I found an abandoned USB stick. On said stick was this:

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

The long gone sort-of Stirling that I melted the hot cap on ..  :facepalm:  File is dated Nov. 2011

The PB flywheel is on the HR-25 attempt ..

dave

« Last Edit: September 05, 2017, 10:03:39 AM by Bluechip »

Offline Ian S C

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Re: Rene Schaffer's HR-25
« Reply #14 on: September 05, 2017, 12:46:42 PM »
You have not been trying hard enough if you haven't had a melt down or two, these are aluminium displacers from my free piston motor, its got a stainless steel one now.
Ian S C
           

 

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