Half Scale 1/4HP A J Weed Engine

[Jasonb]

And so begins another engine build. This time the subject is a 1/4HP A J Weed steam engine as featured in the 1895 Chas A Strelinger & Co catalogue which was the second smallest in a range of casting sets for workshop engines they sold range from 1/8HP to 2HP. This is also said to be the same engine that P M Research based their #6CI on, I have not seen the PMR drawings but have based my half size version on some Youtube videos of an engine restoration and the list of various sizes of parts given as part of the spec in the Strelinger catalogue.



A true half scale would be 3/4" bore x 1.25" stroke but my metric version is actually 20mm bore x 31mm stroke, 90mm flywheel and comes out at 210mm long.



There will be quite a lot of CNC work on this one so look away now if that is not your thing. I also gave 3D metal printing a go for one part, more of that later.

Aluminium worked out the best option for making the bed "casting" so a block was reduced in size to leave 1mm all round the sides and then th ebottom had 1mm skimmed off with an 809mm facemill after which I tapped two M6 holes so a block of metal could be screwed on and that in turn held in the vice.

The first job on teh CNC was just to use the jog as a power feed and skim 1mm off the top with a 25mm insert cutter bringing the 1.25" stock down to the required 30mm height.



It was then just a case of running the various paths, first was an adaptive to remove most of the waste, then a scallop that finished all the main surfaces - the vertical ones all have 2degrees of draft angle to mimic a casting. Then a quick horizontal for the tops of the feet and finally spot drilling and then drilling the tapping size holes for the bearing blocks and trunk guide. The holes were tapped M2.5 and M3 using the tapping function of the SX2.7mill to start the blind holes with spiral flute taps then finished to final depth by hand. A quick rub over with Emery to remove the cosmetic tool marks and the base was done.



More details of feeds and speeds in the video.

<a href="https://www.youtube.com/watch?v=7R378SQfIVY" target="_blank">http://www.youtube.com/watch?v=7R378SQfIVY</a>

[redhouseluv]

That is some serious progress already.......

I must admit the curvature of the bed makes it for me, looks very appealing 

[Johnmcc69]

Very nice! 
 

 John

[Dave Otto]

Looks good, someone snuck in and dropped off a casting when you weren't looking?

Dave

[Jasonb]

I quite like the chunky but curving look of the base too. The PM Research version looks a bit squarer and the corners more angular as are many of the other castings. 

Dave, don't worry no castings will be used in this engine build, there is a big clue in what I wrote in the opening post. But I'll take it as a complement that my CAD produced a part that looks like a casting

[redhouseluv]

Wow, if that's what a 3d metal printing looks like well, what's there not to like, the finish looks great. I presume it came as an approx. solid and you machined to spec as usual from the look of the machining marks? I guess no blow holes, occlusions, soft/hard areas either?

Did you send the file away and get it printed or is the technology required now within reach of the home user?

[Jasonb]

I was going to cover the trunk guide a bit later but since you asked.

I’ve been waiting a while for a suitable part to come up that I could get 3D metal printed just to see how it would turn out. The trunk guide for my this engine seemed to fit the bill so an STL file was created from my Alibre 3D CAD model and uploaded to a few online printing sites to see what the costings and options were.

I added 1mm machining allowance to the bottoms of the feet and also to the cylinder mounting flange. The bore was reduced by 1mm for final boring to size.



I have seen mention of Craftcloud on a couple of other ME forums and ended up going with them. Stainless Steel 316L along with Aluminium seem to be the most common and cost effective materials and Craftcloud offer several prices for both, they also offer DMLS which is said to have smaller layer height than SLM which most other sites do so I went with a 316L DMLS part, basic sandblasted finish.

Production was quoted as 3-4 days and a further 3 for delivery and that is what it took. Several update emails to tell me of progress and good tracking all the way via Fedex.

I’m quite happy with how it turned out, better than most sand castings and as good as many lost wax. There was a tiny depression on the flange but as I had included the 1mm machining allowance o it was not an issue. I can’t see any layer lines and there is just a hint of a bit of remaining support in a couple of places. For an idea of scale it is 61mm long.





Milling (carbide) and boring (HSS) were fine, just a bit more pressure needed when drilling the holes (HSS) so no problems with machining which some of the earlier sintered 3D prints gave problems with. First the feet were milled with a 6mm 3-flute carbide cutter and drilled for M3 fixings



These holes were then used to mount the print to my much used machining plate so that it could be bored on the lathe making use of powerfeed and at the same setting I flycut the cylinder flange ensuring it was true to the 18mm bore





The last job was to clamp the machining plate to an angle plate so that the Screw hole pattern sould be drilled.



Knowing that the print was going to be usable I went ahead and ordered the other potential "castings" from M-machine



Cost wise it was a bit expensive compared with what I could have fabricated it for or even cut from solid on the CNC. It was a fairly even split between the minimum job cost and postage costing just over £50. However having later looked at the Fedex shipping that postage cost would have covered anything upto 1kg and I could have got more prints done and still been within the minimum so could actually have gotten seven printed for the same cost bringing the individual cost to about £7.50. If using again I would group a few parts together so that they were all covered by the one off job cost as that would be far more economical.

[redhouseluv]

I'm sure this of great interest to everyone here.

My personal view is that it is a great advance; if in future those of us who are casting aficionados have a broken cylinder from an early 20th century engine, the option to recreate it via the method you have described is fabulous. The price is not that prohibitive when compared to how much a single casting can cost from Stuarts for instance. As with all these things the price is higher when the technology is newer.

Looks I really need to get my university CAD skills back up scratch! 

[Michael S.]

That's a good start! I really like steam engines with these bases. I could imagine building one myself someday. They come in many variations.

Michael

[Jasonb]

Some nice subjects there, this is one that has been on my to-do list for some time. A Tangye colonial engine

[Michael S.]

Very interesting! I've never seen the valve rod emerge from the back of the valve body and drive the feed pump like this before. Will you build it like this?

[Jasonb]

Probably not as all the other images I have don't have a pump, they do have the tail end of the rod exposed and passing through a packing gland

[bent]

That is a sharp looking 3d printed part!  It looks like it machined nicely as well, no chunks pulling out or nasty finish on the bore?  And the cost sounds quite reasonable too.   

[Jasonb]

Yes it machined very nicely and seems to be very solid

For tonights entertainment I will cover the bearing pedestals and their caps. The original I am replicating used Babbit for the bearings but I will turn mine from bronze so the pedestals are a bit narrower to allow for flanges each side of the bearing.

Two x two blocks of 6082 were roughed out oversize on the manual mill and then located in the KX-3s vice. First I did the hump back profile and boss of the caps followed (not shown) drilling the clearance holes.

The pedestals were then located - I tend to use the top centre of the stock a lot as my datum. The basic shape cut with a 4mm 3-flute ali cutter leaving 0.3mm still to come off. The holes were then drilled and in the case of the top two tapped M3. Canging to a 4mm dia cutter with a 1mm corner radius to leave a fillet around the bottom I contoured the pedestal and then screwed the cap in place an ran the contour again at a different height which ensures all the edges match up and are perfectly flush.

<a href="https://www.youtube.com/watch?v=JUaK34OdFf8" target="_blank">http://www.youtube.com/watch?v=JUaK34OdFf8</a>



Back to the manual mill to remove the excess holding material from the bottom of the pedestalls.



Then with the caps in place I drilled and reamed for the bearings. Should say 9.8mm drill and reamed 10mm, it's the crankshaft that is 8mm! No photos of the bearings as they are just bobbin-shaped bits of bronze.

[Krypto]

I'm enjoying seeing how you use your small CNC mill to great effect for making parts that would be extremely difficult or time consuming on manual machines.  I even went back and read your old posts about the mill in the ME forum. 

I used to think these small CNC mills weren't particularly useful as you so rarely see forum posts or videos with people using them, but they do seem worth it for 2nd operations milling.  A few of them are starting to pop-up in the used market as they are getting a bit long in the tooth or the owners want big and better, so it's something I might have to keep a lookout for in the marketplace.