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I am considering building a version of the Ian Bradley Electrically Heated Heinrici engine published in ME 3741 to 3751 in five parts (1984/5). I have sourced the torque tube bearing from the original supplier that Ian Bradley suggested back in 1985. My question is how is the connecting rod (Part O in Fig 31 ME 3747 p 214 connected to the outer of the eccentric bearing.

The drawing shows two holes which would be radial to the bearing outer and a suggestion that a pinch bolt causes the end of the conrod to grip the bearing outer race when it is tightened.

Is there something, not mentioned in the article? Do torque tube bearings (Ransome and Marles type CA1 1 9/16" bore by 2" OD by 9/32" wide) have protruding lugs on the outer that could fit into the radial holes? The size of these holes does not seem to be dimensioned in the plans.

Has anybody other the the author built an engine to these plans?

Bob

Is the "ME" an abbreviation for mechanical engineer? I suppose it is a magazine or publication of some kind, but I have never heard of it.

ME is the English Model Engineer magazine, it was first published in 1898, and the publisher was told by many that it would be lucky to last six months, I believe it is available in the USA, it is in Canada, and all parts of the British Commonwealth. For over one hundred years there have been articals about stirling engines. Have a look a http://www.model-engineer.co.uk
The current magazine has part two of the build of Robert Stirling's Air Engine, Thats a motor built before the one thats usually shown as his first, its a copy of one that was/is in the Glasgow university, the author recomends getting a copy of James G. Rizzo's book "Robert Stirling's Models of The 'Air Engine". Ian S C

Hi Ian et al

Well I now own one of the torque tube bearings. The exact item quoted by Ian Bradley in his ME (Model Engineer) magazine article. I have to say that I am none the wiser about how the con rod grips the bearing outer race. There are no holes or dimples in the periphery of the outer race for any pegs to engage in.

Bob

Hi Bob, I'v serching google to see if I could find a photo of the motor, to see if I could work out how the bearing is attached, but could not find one. Sorry not much help, maybe glue would hold it, a good test for the glue! Ian S C

Hi Ian

I am thinking that I need to redesign the con rod with either a bored diameter that will completly encircle the bearing outer or a two piece design with an alloy ring fitted with loctite to the bearing outer and a modified form of the original design conrod bolted to the alloy ring.

As a more general point of interest I wonder how many models are actual made by people other than the orginal author to plans published in ME? I would suspect the number of locomotives and traction engines is much higher than the number of Stirling engines or IC engines.

Bob

Bob, other than the scale modelers, I think a good many use the published plans as a guide only, and use the materials etc., that come to hand, also it is possible to improve the design of some motors considerably(even ones designed by seemingly knowledgable modelers), I tend to look to build with the most suitable materials ie., cast iron pistons,stainless displacer and its cylinder. I don't always get it right, my free piston engine went through three displacers made of aluminium before I changed to stainless steel. The first one did'nt have a stop and the hot end hammered against the end of the cylinder, it lasted about five miniutes, the end was shaped like a mushroom, the next two just melted down and collapsed. The main reason I advocate stainless steel is that my main engines are heated with LPG, although with any heat source aluminium is not good because of its good heat conduction. Saw one motor of reasonably complex design with both an aluminium displacer, and cylinder, and an aluminium piston in a bronze cylinder.
Hope no one takes offence, these are my opinions. Ian S C

Hi Ian

While you are on the topic of displacers...

... the engine that is currently on my bench is a small Robinson hot air engine. I am taking the leading dimensions from a design published in ME 3803 19 June 1987 page 707-7 by J Robinson. The design calls for a displacer formed from a stack of aluminium disks (24 in total) each disk is perforated with 5 holes and separated from adjoining disks with 2BA washers. The holes are aligned to create turbulance as the air passes back and forth through the displacer. The hot end is 1.5" diameter. The design calls for brass, but I am inclined to use stainless turned down to the thinnest possible wall thickness.

Now actual Robinson engines seemed to have a hollow thin-walled brass displacer, but a friend of mine has a Robinson with stacks of gauze forming the displacer/ moving regenerator. So, which is likely to give the best results? Air tight thin-walled stainless steel displacer or a stack of perforated disks acting as a moving regenerator? My gut feeling is that the disks will be quicker to make than the air tight displacer.

Bob

Bob, I think the stainless discs sounds the way to go, try and get stuff about as thick aas a baked bean can, just thick enough to keep its shape, ie., won't sag, and hit the end of the cylinder. I started to build one of those motors a few years back, but the parts ended up in another motor, the cylinder and piston form part of a tin can motor, but I think that may change, not over impressed with it. Ian S C