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Ian Bradley Heinrici Engine ME 3741

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Bob15/03/2012 20:05:11
38 forum posts

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?


Ian S C16/03/2012 11:13:07
7468 forum posts
230 photos

bob, sounds interesting, but I have not seen that motor, can't quite visualise the use of the large dia bearings, I would like to see some diagrams of it. Ian S C

Mark Foster 116/03/2012 13:30:17
34 forum posts

I have built one I think ! the bearing is just pinched in the Al bit .you have to wash out the bearing no oil . Mine has been heated with a Metho burner . runs for hours on a small amount . a nice running engine . How about a picture . I will take one of the bit .If its the same engine

Mark Foster 116/03/2012 13:32:30
34 forum posts

the radial holes just have screws in them to locate the bearing .(from memory ) think it would be better to have a steped bore

Bob17/03/2012 07:42:44
38 forum posts

Hi Mark et al

I find it difficult to understand how tightening the pinch bolt will cause the end of the con rod to grip the bearing outer race. The con rod as drawn would only touch the outer over about a quarter of its circumference so it looks to me a bit like a child with a small hand trying to pick up a basketball using just one hand. No matter how hard he trys the ball will always spring away. I would think that the conrod end needs to cover more than half the circumference of the bearing outer to afford any grip.

 Ian, I think the strange bearing with its large internal diameter is to give a very free running eccentric with minimal out of balance mass. Remember friction (and air leaks) are the enemy of hot air engines.  I believe that Ian Bradley had a background in aircraft engineering and I think that this style of bearing were used in aircraft control systems. I have seen them advertised as 'torque tube' bearings.

I agree it is a fine looking engine. I am thinking about water cooling the cold end and using either gas or spirit firing.


Edited By Bob on 17/03/2012 07:48:01

Ian S C17/03/2012 12:46:02
7468 forum posts
230 photos

I though it must be for an eccentric. If the radial nole are as i think they are, the end of the con rod would only have to cover two of them, the n a pair of screws through the con rod into the holes, then tighten the pinch bolt, and the whole thing would be solid, sounds a good system. Ian S C

Ian S C18/03/2012 03:06:19
7468 forum posts
230 photos

Had a look at bearings on google, Ransome Marles, is now Ransome Hoffmann Pollard Ltd. I could not find the bearing I was thinking of, proberbly a figment of my imagination. Ian S C

Bob06/04/2012 10:59:39
38 forum posts

Hi all

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.


Mark Foster 106/04/2012 14:47:11
34 forum posts

how about a picture ? or a bit of the plan if it is the same as mine .

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