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Mike Adams

Kelvin stay bar

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My J2 installation has a stay bar mounted on the front of the forward cylinder and attached to the starbord side of the boat.Is this normal practice on a narrowboat as it seems to have caused some damage to the cylinder? I noted after reading the instuctions Kelvin suggest transverse mounts and mine are longways. I think mine is a rigid coupling( the end is behind the panelling) so I can't see it without taking of the t and g. Is the answer to beef up the engine beds?

Mike

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4 hours ago, Mike Adams said:

 Is the answer to beef up the engine beds?

This is how the engine beds were strengthened on Owl.  The engine is stable and there is no need for a stay bar.

wfbc4.jpg.51aef45cc0e9b880bbdeeb5bb4948b52.jpg

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The stay bar is best fitted to a J if you don't have the wide feet fitted ( The K is wider naturally), though I have seen several installations without one.  Much depends on the beds and the mounting arrangements. Bergius expected the engine to be in a wooden boat on wooden bearers which is never going to be a stiff as a steel platform in a steel boat.

The weak points are the two feet mounting bolts through the crankcase at each end.  These are close tolerance special bolts in close tolerance holes. A wobbly engine causes wear either in the feet to crankcase holes (fairly easy to bush) and/or in the crankcase ( a black enamelled beggar of a job to bush). Check these bolts are tight.

It sounds like your set up is not the best for stiffness if the main bearers are longitudinal so any improvement would be good. Longitudinal bearers must have  made for  a really awkward installation given the general engine shape.  

 I would try to keep the stay bar, which  is best to the PORT side of the engine because iit is in compression then, and have a look  at the engine end. There is a shaped recess around the stay bar stud and the bar-end should fit this on the cylinder side but be flat on the other side. The stud is 7/16 I think.  The detail of the recess is on the cylinder drawing IIRC and I will look my copy out if that would be helpful.

I would also check that the stay is mounted horizontal, with a load path direct to the hull. T&g on battens is not really up to the task. Mine has a bit of 4x4 Douglas Fir between the flange at the end of the metal stay bar and the hull steel to cut down the vibration transfer.

Regards

N

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Thanks for helpful hints. The engine has been in the boat since 1987 so maybe nobody has checked the engine mounts. I appear to have a problem leak around the stay bar, which is fabricated. The cylinder has been brazed at some point and then covered with some sort of sealant so I cant clearly see the arrangement without taking it off. Do all cylinders carry the facility for mounting the stay bar or do I need a special one? I think the stay bar is welded directly to the hull behind the panelling. I would have thought some sort of rubber coupling/mount would have been better.

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I owned a boat some years ago with a J2 installation complete with tie bar. The engine vibrated quite significantly to the extent that it had a habit of fracturing the rear engine mount which was made of cast steel. I think the tie bar had been some sort of attempt to eliminate the vibration, but the whole problem was a very poor initial installation. I now know from my present boat that with a correctly installed vintage engine, no vibration whatsoever should be present.

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Mike, all the cylinders should have the recess for the stay bar and a threaded hole for the stud.  Only No1 cylinder is actually fitted with the stud as it will otherwise foul the next cylinder forward if fitted to 2,3,or4. The stud hole goes right through to the water passage so that may be the source of your leak rather than a crack.

If you are thinking of swopping No 1 and 2 cylinders the only really difficult bit is getting at the nuts on the forward and aft cylinder to crankcase studs. A crowsfoot spanner is recommended if you don't have the special tool ( a crowsfoot spanner on a long bar with a hook and spring to go over the head stud) though a shortened OE spanner annd a selection of universal joints  and a socket will get you there  in the end. The first time I fitted a cylinder it took 6 hours struggling with the front/back nuts! Got the hang of it now!

If you are really stuck I know of two places  where there is a pattern for casting new cylinders.

N

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Here is a photo of a set of wide feet I have fabricated for a Kelvin, it is an F4 rather than a J but there are some similarities between the engines.

The paraffin engines were never fitted with stay bars or wide feet as standard, I do know of an F2 with wide feet from a J fitted.image.jpg.97e24438b2db671027f93ab86c842093.jpg

Tom

Edited by tom_c

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