Problems

 

There are a number of known problems with the engine as sold.

I have run into a number of other problems associated with my level of skill!

This page attempts to list them so that other builders can avoid them.

Some of these problems are minor design glitches whereby a part made to its drawing doesn't match up with a corresponding part.

Some problems are potentially catastrophic in terms of collisions of major components.

Some are annoying drawing mismatches.

The numbers in the table are simply to help identify the issue and do not, at this stage, give any priority.

 

 Number Problem Description Photos Solution
1 The pump arms (part of the box guides) will collide with the wayshaft at the top of the stroke of each cylinder by between 0.250" and 0.375"

REVISION 24 December 2002

This collision problem ceases to exist if you choose to redesign the wayshaft pivot to port as described below

This depends on when you find out about the problem!

 

You won't know how bad the problem is until you assemble everything. My interference was a bit less than 3/8", made worse because my main bearing centreline is level with the top of the bedplate rather than 1/8" below as the drawings suggest.

 

If you haven't machined the columns make them 0.750" longer below the cross bar holes. This allows plenty of room for a nut on top of the pump arm for the pump rod.

 

If you have machined the columns then:

Shorten the connecting rods, the feet will end up at around 7/16" thick

Machine pads for the bottoms of the columns around 3/8" thick if you have enough thread or 1/4" for the top if you don't.

Either pad the feet of the slide bars by 1/4" or slot the bottom mounting holes.

You may have to thin the pump arms a bit.

2 The mounting holes for the LP valve chest are drawn at 3/8" diameter while the holes in the cylinder block are for 5/16" UNC studs I found out after I had drilled the valve chest holes...

5/16" fasteners would probably have looked tidier

3

If machined to the drawings the connecting rod top bearings foul the slidebar aspect of the crossheads as the crank approaches 90 degrees and 270 degrees. ie the wristpin is too close to the slidebar face of the crosshead

These photos show how another builder overcame the problem

I was fortunate in finding out about this one before I bored the holes in the crosshead for the wristpin!

My solution is to move the wristpin bore and the threaded hole for the piston rod 1/8" away from the slide bar and to move the slidebars 1/8" to port

This led to some mischief when mounting the slidebars to the bottom cylinder covers but that is a devil of a job anyway.

Plenty of room!

Slidebar feet (IP)

4 The design of the valve gear regulating arms is incorrect

The drag links should be horizontal in the ahead position so that sideways movement of the links is minimised.

The engine has the draglinks horizontal in the midgear position and inclined at an angle of about 20 degrees in the ahead position

This means that about 5/16" of lateral thrust is given to the end of the regulating arms with every stroke of the valve resulting in a lot of clatter and/or severely strained valve linkages

 

 

 

 

 

 

 

 

 

 

 

 

Showing the inclined drag links in the engine built in Maine

Measuring regulator arm "kick" as designed

Showing the mockup I used to optimise the wayshaft position, shown here in astern

The extension piece

From forward

Finished

 

This is the hardest one to solve and probably the most serious in terms of engine silence and longevity.

I am separated from this by about four months or the time it takes to machine all of the valve gear components

Ideas floating around at the moment lean to recasting the regulating arms about 1 1/2" longer and altering the valve gear regulating slots so that they are horizontal (maximum effect) when the regulating arms are down close to the engine.

The ideal solution would be to lengthen the arms and move the wayshaft sideways by about 2 ".

Update 24 December 2002

After much head-scratching, experimenting and lost sleep I decided to move the wayshaft pivot point 2.500" to port and down by 0.375"

This was achieved by extending the part of the lower valve chest covers that support the wayshaft using an extension piece machined from mild steel.

By utilising the existing regulator arms I am able to obtain horizontal drag links in both ahead and astern and reduce link slip (or regulator arm "kick") to around 0.105" rathe than the 0.190" measured in my experiments with the "as designed " pivot point

With everything assembled and running there is negligible regulator arm "kick"

5 I have had continual problems with collisions and misalignments along the long axis of the engine.

From lining the big ends up with the crankshaft to the HP & IP valve gear colliding with the crossheads or the columns.

The most serious of these is the need to offset the HP valve trunnion forward by over 1/8" so that the eccentric rod top bearings clear the forward columns

 

The HP valve gear showing an offset of 0.190"

The drawings require the valve trunnion to be offset by 0.125"

I can't move the quadrant etc. back due to fouling of the forward column and the eccentric strap fouls the bedplate

The finished HP trunnion showing the marked offset necessary

 

These problem are, to a large part, my own fault.

When "targeting" the cylinder block I started measuring from where I thought the LP port face would be.

I should have started measuring from the centre of the IP bore so that my errors started in the middle and did not accumulate the full length of the block.

Similarly I targeted the bedplate from the centre of the landing pads for the columns rather than the centre of the IP crank web "pit"

A beginner's error!

6 A blowhole in the IP bottom cylinder cover above the gland

When I machined the cover I noted the hole but didn't consider that it may have passed right through the casting.

This explained the loud hiss with the engine running on air despite various attempts to tighten the packing gland and I could feel a draught from somewhere!

From inside the cover

From outside (underneath)

 

I bored out the gland deeper and inserted a "bush" with a press fit

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