Half Scale 1/4HP A J Weed Engine

[JasonBModerator @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 the bottom 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 the 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.

[DiogenesParticipant @diogenes]

Why the kind of ramping up and down the sides at the head end @ 2 mins in?..

[Adrian R2Participant @adrianr2]

Looks more aerospace than Victorian. With what you now know about 3D metal printing, could this base have been economically produced in a batch with the slide, and possibly other parts?

[JasonBModerator @jasonb]

The 3D Scallop finish path takes some weird and wonderful routes. Basically it steps over a given amount which in this case was set at 0.2mm no matter what the angle of the surface is. So unlike the Adaptive which leaves horizontal steps much like contours on a map the scallop can end up moving in quite complex paths as it may reach a more vertical edge in one direction while still cutting a near horizontal area in the other. I expect the software works out the shortest route to cover the whole surface and that is why it can seem quite random at times.

 

[JasonBModerator @jasonb]

Adrian, I’ll get some prices for various options and post the results in the other thread, probably won’t be until later today. Should also be able to work out what it would cost me to have cast in the UK.

[DiogenesParticipant @diogenes]

..I get it – I’d forgot there was draught on it..

[DiogenesParticipant @diogenes]

..forgott-en, even..

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