Stuart Sirius

[AN5523]

Here some picture of the last build Stuard Sirius steam motor.
It was build of a set of castings from Stuart.

IMG_6431_proc

• AN5523
• Oct 19, 2019

Height 6 Inches.
Discwheel Diameter 2 11/16 Inches.
Cylinder Bore 1 Inch Diameter.
Cylinder Stroke 1 Inch.

Greetings
an5523

 

[Richard Hed]

Here some picture of the last build Stuard Sirius steam motor.
It was build of a set of castings from Stuart.

IMG_6431_proc

• AN5523
• Oct 19, 2019

Height 6 Inches.
Discwheel Diameter 2 11/16 Inches.
Cylinder Bore 1 Inch Diameter.
Cylinder Stroke 1 Inch.

Greetings
an5523

Ah, I was out of the country at the time this was posted. Did you machine this? Have you got more photos?

 

[GreenTwin]

The Stuart website indicates that castings for this engine are still available for sale.
Here is a description of the engine from the Stuart site:

The Stuart Sirius was originally designed for racing steam hydroplanes. Particular attention was given to the valve gear and steam passage design with the result that the engine produces great power using a surprisingly low volume of steam. Our tests have shown that running at 2800 rpm the engine produces 1/3 bhp. at 80 psi.

The Stuart Sirius is a very interesting model to build and can be completed on a 3 1/2 in. lathe. The kit includes a pair of finished gears, as these are difficult to produce even with specialist equipment. Please note that no materials are included in the kit.

.

 

[Richard Hed]

The Stuart website indicates that castings for this engine are still available for sale.
Here is a description of the engine from the Stuart site:

The Stuart Sirius was originally designed for racing steam hydroplanes. Particular attention was given to the valve gear and steam passage design with the result that the engine produces great power using a surprisingly low volume of steam. Our tests have shown that running at 2800 rpm the engine produces 1/3 bhp. at 80 psi.

The Stuart Sirius is a very interesting model to build and can be completed on a 3 1/2 in. lathe. The kit includes a pair of finished gears, as these are difficult to produce even with specialist equipment. Please note that no materials are included in the kit.

.

Yes, I got one. Am looking for other peep's build logs. I keep forgetting to take photos of my build. Where I am working, I can machine most of what I have, however, I am having trouble with the crank shaft. I am using CNC but at home (1200 miles away) I have a conventional lathe on which it would be a snap to machine the crank. Also, the CNC easily crushes the brass parts when put in the 3 jaw.

 

[Steamchick]

Hi Richard, are you happy with a file? - But seriously, I doubt you would be happy to do that and try and get the precision you require. The only option without a lathe would be using an alternative rotating machine, such as a milling machine or Pilar drill, mounting the shaft (in an off-set clamp for big-ends) in the quill, and mounting the tool on the X-Y table.
I heard of someone trying a job like that, but don't know if they succeeded, as the forces for cutting are just all wrong and the machine is too femur. I can only suggest "ask a local machinist" if he can do it or lend you a lathe?
Is there a Model Engineering group near you? - perhaps they can help? (I am in the UK - and would do it for you - but I am sure you'll find something closer, and better!).
K2

 

[Jasonb]

If you can't do it with a CNC lathe then why not manually control it? Just jog to put on a cut and then jog the other axis to make the cut it would be no different to turning handwheels. Or if your controller has conversatonal or wizards just use that.

Get a collet chuck or make some split bushes if you are damaging fine parts.

 

[Richard Hed]

Ah, I knew someone would have some great suggestions. The prob with the crank is the actual offset part, (the crank) not the bearing parts. I'm thimpfking of making a holder with an offset. The distance between centers of the cranks is 1" so half an inch might not be out of the question. Maybe. An alternative would be to do it on the CNC mill with a cutter that could reach in past the parts that are sticking out in the way. I don't like the idea, but I will look into it more. OOoohhh, to have a four jaw on a conventional lathe!

As for the brass parts that are easily crushed under the pressure of the CNC jaws, for small parts, Jason's suggestion is precisely what I was thimpfking. HOwever, the two end bearings, being somewhat like a flat umbrella shape, the umbrella being .188" is very soft. That part is not a part that needs a precision fit so if it is crushed a bit, a simple file can fix the prob. Maybe not LOOK nice but still fine to work correctly. These two bearings are too large, a bit over 2" to find a collet chuck that would fit. Hey! How about an aluminum ring, split so it can fit around the thing and still be able to close? Ha! Thimpfk I will try that. Thanx guys--you've been a great help.

Here is a dwg. of the two bearings. I have pointed out the thin circular wall that is, indeed, a precision fit into the ends of the crankcase. So, you can imagine that this wall will NOT be crushed by the jaws. Also, the center hole for the crank shaft has that long stick-out for both pieces. Well, the jaws DID crush the outside but not badly. When I use the collet chuck to finish it up, it should work snappy fine.

K2, You told us about your experience with the Sirius's brother. But you don't have photos? 20 years ago? Any more anecdotess?

 

[Jasonb]

You have two options for the crank. First turn the actual shaft parts so you have something true and round to hold then
1. make a block with a hold offset by half inch and a couple of clamping screws at 90deg. You can then clamp the crankshaft in that and turn each pin. This is much like you would turn the pin on a single cylinder model aero engine. Repeat for the other pin.

2. Make two blocks that clamp onto the ends of the shaft with 1/2" offset ctr drill holed. These can then be clamped onto the shaft and used to turn it between ctrs.

I've used both methods in the past but would go with the first

4-jaw is not ideal as the small dia of the shaft is more than the throw so you can't get all 4- jaws in contact. If you have a square collet block then that would allow enough offset and all jaws to contact.

As for the end caps, that's a job for soft jaws. I'd turn the outside first then hold in the softjaws to do the inside and get the step that locates in the crankcase and the bore concentric

 

[Richard Hed]

You have two options for the crank. First turn the actual shaft parts so you have something true and round to hold then
1. make a block with a hold offset by half inch and a couple of clamping screws at 90deg. You can then clamp the crankshaft in that and turn each pin. This is much like you would turn the pin on a single cylinder model aero engine. Repeat for the other pin.

2. Make two blocks that clamp onto the ends of the shaft with 1/2" offset ctr drill holed. These can then be clamped onto the shaft and used to turn it between ctrs.

I've used both methods in the past but would go with the first

4-jaw is not ideal as the small dia of the shaft is more than the throw so you can't get all 4- jaws in contact. If you have a square collet block then that would allow enough offset and all jaws to contact.

As for the end caps, that's a job for soft jaws. I'd turn the outside first then hold in the softjaws to do the inside and get the step that locates in the crankcase and the bore concentric

Yup, as for the 4 jaw, I would make an alum holder (sort of soft jaws) then move the crank around with the adjustability of the 4 jaw. But I don't have that capability here. So I thimpfk that an offset alum holder should do the trick. As for the brass end bearings, I thimpfk a simple ring (split) should be equivalent to soft jaws. What do you thimpfk about that?

 

[JimSvarv]

For the bearing blocks you could glue the brass to a roundbar.
And turn the bar to fit your second setup and glue it to the other side.

Something I have been wondering but I guess wouldn't work.
Is if it would be possible to make a 180 degree crankshaft laying on it's side in a 3 axis cnc mill with 2 setups.
There will be a weird radius on half of the crank throws.

A built up crank is maybe best if one want to make it in 3 axis mill.

 

[Richard Hed]

For the bearing blocks you could glue the brass to a roundbar.
And turn the bar to fit your second setup and glue it to the other side.

Something I have been wondering but I guess wouldn't work.
Is if it would be possible to make a 180 degree crankshaft laying on it's side in a 3 axis cnc mill with 2 setups.
There will be a weird radius on half of the crank throws.

A built up crank is maybe best if one want to make it in 3 axis mill.

Good idea, very good idea. I have a tite-bond substitute that should do it. Thanx

 

[Jasonb]

A cup chuck or ali ring will spread the load in a similar way to soft jaws as some of that gun metal can be quite soft.

 

[Richard Hed]

A cup chuck or ali ring will spread the load in a similar way to soft jaws as some of that gun metal can be quite soft.

What are these: A cup chuck or ali ring ? Do they have different names?

 

[Charles Lamont]

"Ali" is short for aluminium.

 

[Richard Hed]

"Ali" is short for aluminium.

Oh; how silly of me. I always shorten it to "alum"

 

[Steamchick]

Hi, I may have a couple of photos I think, but must have a search. Probably pre-digital I think, so it may have been later different machining that I photographed, not being in the habit of using film cameras for recording such things. Made in 2001-2002, but I think i got my first digital camera in 2003...?
And my set-ups back then we're not as good as they should have been. I remember using the 4 jaw chuck, holding an eccentically set 3 jaw chuck, that held the shaft for machining the big-end journals. It was well out of balance!.
I remember I had 2 or 3 lathes before I inherited my Father's when he died in 2002, but showed him the block with crank and pistons before he died. I had bought the castings at the last show we attended together. So this Sun engine is a bit special for me.
K2.